EPA 402-R-96-013
USER'S GUIDE FOR
PRESTO-EPA-CPG OPERATION SYSTEM
Version 2.1
June 1, 1996
Developed by
Cheng Yeng Hung, Ph. D.
U.S. Environmental Protection Agency
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EPA 402-R-96-013
USER'S GUIDE FOR
PRESTO-EPA-CPG OPERATION SYSTEM
Version 2.1
June 1, 1996
Developed by
Cheng Yeng Hung, Ph. D.
U.S. Environmental Protection Agency
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Office of Radiation and Indoor Air
Washington, DC 20460
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USER'S GUIDE FOR
PRESTO-EPA-CPG OPERATION SYSTEM
Version 2.1
June 1, 1996
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Developed by
Cheng Yeng Hung, Ph. D.
U.S. Environmental Protection Agency
Office of Radiation and Indoor Air
Washington, DC 20460
DISCLAIMER
This user's guide for the PRESTO-EPA-CPG operation system is
the result of integrated work sponsored by an agency of the
United States Government. Neither the United States Government
nor any agency thereof, nor any of their employees, contractors,
subcontractors, or their employees, make any warranty, expressed
or implied, nor assume any legal liability or responsibility for
any third party's use of the results of such use of any
information, apparatus, product or process disclosed in this
report, nor represent that its use by such third party would not
infringe privately owned rights.
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PREFACE
A mainframe version of the PRESTO-EPA-CPG model was
developed for generating basic data to support EPA's rulemaking
on the generally applicable environmental standards for the
management and disposal of low-level radioactive waste (LLW).
Since the mainframe version of the PRESTO-EPA-CPG model was
published in December 1987, the Office of Radiation and Indoor
Air has received numerous requests from potential users of the
model urging the Office to convert the model to a form usable on
a personal computer. This effort has subsequently proceeded in
two phases, the simplification of the PRESTO-EPA-CPG model and
the development of the PRESTO-EPA-CPG Operation System. The
simplification of the PRESTO-EPA-CPG model involved primarily the
modification of the DARTAB subroutine so that the size required
by the random access memory can be reduced considerably without
altering the accuracy of the simulation results. The PRESTO-EPA-
CPG operation system is designed to assist users to create and
edit the main input file for the PRESTO-EPA-CPG model. It is a
user friendly, menu-directed operation system. Users will find
that the operation of the system can be simplified and many of
the potential errors can be prevented by employing the operation
system program. The operation system does not include the
preparation of the input file required by the INFIL subroutine
because the input file can be easily handled without an operation
system. The first version of the Operation System was published
on April 30, 1989, and the second version on September 1, 1993.
The second version of the Operation System added several
improvements to the previous version: (1) color monitor support,
(2) more user friendly features, and (3) plotting capability for
annual individual dose.
This version of the operation system has added four
improvements: (1) addition of the daughter nuclide in-growth
effects into the risk assessment, (2) update of the dose and risk
conversion factors to 1994 level, (3) addition of the annual
mortality and risk incidence calculation, and (4) adoption of the
iii
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International System (SI) units.
IV
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TABLE OF CONTENTS
Page
LIST OF FIGURES viii
LIST OF TABLES ix
1 INTRODUCTION 1- 1
1.1 Background 1- 1
1.2 Changes in Version 2.1 1- 2
2 DESCRIPTION OF PRESTO-EPA-CPG MODEL 2- 1
2.1 General Description of the Model 2- 1
2.1.1 Description of a Disposal Site 2- 1
2.1.2 Description of the Model 2- 3
2.2 Mathematical Formulations 2- 6
2.2.1 Transport Pathways Involving Water 2- 7
2.2.2 Atmospheric Transport Sources and Pathways 2-25
2.2.3 Food Chain Calculations 2-32
2.2.4 DOSTAB Calculations 2-41
2.2.5 Daughter Nuclide In-Growth Effect Calculation
2-43
2.2.6 Basement Dose to Resident 2-46
2.3 Development of PRESTO-EPA-CPG Code 2-50
2.3.1 Model Structure 2-50
2.3.2 Subroutine Description 2-51
2.3.3 PC Version of PRESTO-EPA-CPG 2-58
2.4 Input File Requirements 2-58
VI
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2.4.1 Site and Nuclide Specific Input File 2-58
2.4.2 INFIL Subroutine Input File 2-59
2.4.3 Dosimetric input File 2-59
2.5 Output File Description 2-60
2.5.1 Replication of Input Data 2-60
2.5.2 Radionuclide Summary Tables 2-60
2.5.3 INFIL Input/Output 2-60
2.5.4 Annual Summaries 2-61
2.5.5 Radionuclide Uptake and Concentrations ... 2-61
2.5.6 Maximum Individual Dose Summary 2-61
2.5.7 DOSTAB Result Tables 2-61
2.5.8 Dose to Critical Population Group 2-61
3 DESCRIPTION OF THE SYSCPG PROGRAM 3- 1
3.1 PC Version of PRESTO-EPA-CPG Model 3- 1
3.2 Description of SYSCPG System 3- 2
3.2.1 General 3- 2
3.2.2 System Structure 3- 3
4 SYSTEM INSTALLATION 4- 1
5 SYSTEM OPERATIONS 5- 1
5.1 Start Up 5- 1
5.2 Copy a New Input File from the Standard Input File
5- 2
5.3 Edit the Existing Input File 5- 2
5.3.1 Editing the CPG Input File 5- 3
5.3.2 Comparing with a Standard File 5- 4
5.3.3 Review the CPG Input File 5- 5
5.3.4 Delete Radionuclides 5- 5
5.3.5 Insert Radionuclides 5- 6
5.3.6 End of Editing 5- 7
5.4 Test the Current Input File 5- 7
5.5 Execute PRESTO-EPA-CPG 5- 8
5.6 Print Out CPG.OUT 5- 9
5.7 Plot the Annual Doses 5- 9
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5.8 End of Operation 5-10
REFERENCES R- 1
APPENDIX A - THEORETICAL BACKGROUND OF THE INFILTRATION
SUBMODEL
A- 1
APPENDIX B - THEORETICAL BACKGROUND OF THE GROUNDWATER TRANSPORT
SUBMODEL B- 1
APPENDIX C - THEORETICAL BACKGROUND OF DAUGHTER NUCLIDE IN-GROWTH
EFFECTS CORRECTION FACTOR C- 1
APPENDIX D - INPUT FILE FORMAT D- 1
Table D-l Environmental and Nuclide Specific Input File
D- 3
Table D-2 INFIL Subroutine Input File D-16
Table D-3 Dose Conversion Factor Input File D-18
Table D-4 Risk Conversion Factor Input File D-24
APPENDIX E - SAMPLE INPUT AND OUTPUT FILES E- 1
Table E-l Environmental and Nuclide Specific Input File
E- 3
Table E-2 INFIL Subroutine Input File E- 9
Table E-3 Dose Conversion Factor Input File E-15
Table E-4 Risk Conversion Factor Input File E-23
Table E-5 Sample Output File E-27
Vlll
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LIST OF FIGURES
Figure No. Page
2-1 Environmental Transport Pathways Used in PRESTO-EPA
Model 2 - 2
2-2 Hydrologic Transport Pathways 2- 5
2-3 Atmospheric Transport Pathways 2- 6
2-4 Trench Cap Failure Function 2-12
2-5 PRESTO-EPA-CPG Subroutine Structure 2-52
5-1 Main Menu of the Operation System 5- 1
5-2 Sub-Menu for Input File Editing 5- 3
5-3 Instructions for File Editing 5- 4
IX
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LIST OF TABLES
Table No. Page
1-1 Function of PRESTO-EPA Family Codes 1- 2
2-1 Leaching Options Specified for LEAOPT 2-13
2-2 Units of Exposure and Dose Rate Factors Used in DOSTAB 2-42
2-4 Results of Basement and Infinite Plane Unit Dose Rate
Computations 2-49
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XI
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1. INTRODUCTION
1.1 BACKGROUND
The U.S. Environmental Protection Agency (EPA) is
responsible for developing a generally applicable standard for
the disposal of low-level radioactive waste (LLW) to support the
U.S. Nuclear Regulatory Commission and the U.S. Department of
Energy in developing a national radioactive waste management
system. Technical support for the standard includes an
estimation of the health impacts from the disposal of LLW in a
wide variety of facilities, ranging from a standard sanitary
landfill to a deep geologic repository.
As an aid in developing the standard, a family of computer
codes, entitled PRESTO-EPA-POP, PRESTO-EPA-DEEP, PRESTO-EPA-CPG,
PRESTO-EPA-BRC, and PATHRAE-EPA has been developed under EPA
direction. The PRESTO-EPA-POP code was the first code developed
and served as the basis for the other codes in the family. EPA
uses the PRESTO-EPA code family to compare the potential health
impacts (cumulative population health effects and maximum annual
dose to a critical population group) to the general public and
critical population group for a broad number of LLW disposal
alternatives to evaluate and support its decisions for the LLW
standard. Table 1-1 provides a brief description of the function
of each member of the family. The application of these codes in
the LLW Standards was described in detail elsewhere (Hu83, Gal84,
Ro84). Information on obtaining complete documentation and
user's manuals for the PRESTO-EPA family of codes (EPA87a through
EPA87g, MeySl, Mey84) is available from EPA.
The PRESTO-EPA-CPG (Critical Population Group) code is a
computer code designed to analyze the maximum annual committed
effective dose (CED) to a critical population group, resulting
from the disposal of low-level radioactive waste in a underground
disposal facilities.
In addition, a new user may find that one of the input files
is too complicated to generate for obtaining a successful
execution of the program without undergoing several trial runs.
1-1
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In order to reduce the potential of making these errors, a user
friendly input file preparation program, INCPG, was developed to
automate the input file preparation [Hu87] .
This user friendly PRESTO-EPA-CPG Operation System Program,
SYSCPG, is the combination of the input file preparation program
and the PC version of PRESTO-EPA-CPG model and is designed to
simplify the operation of PRESTO-EPA-CPG model. The first
version of the Operation System was published in April 1989. The
second version of Operation System made considerable improvements
to the first version, including (1) color monitor support, (2)
more user friendly features, (3) plotting capability for annual
individual committed effective doses, and (4) inclusion of the
theoretical background of the model in its documentation.
Table 1-1 Function of PRESTO-EPA Family Codes
PRESTO-EPA Code
Purpose
1-2
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PRESTO-EPA-POP
PRESTO-EPA-DEEP
PRESTO-EPA-CPG
PRESTO-EPA-BRC
PATHRAE-EPA
Estimates cumulative population health
effects to local and regional basin
populations from land disposal of LLW by
shallow methods; long-term analyses are
modeled (generally 10,000 years).
Estimates cumulative population health
effects to local and regional basin
populations from land disposal of LLW by
deep methods.
Estimates maximum annual committed effective
dose to a critical population group from
land disposal of LLW by shallow or deep
methods; dose in maximum year is determined.
Estimates cumulative population health
effects to local and regional basin
populations from less restrictive disposal
of BRC wastes by sanitary landfill and
incineration methods.
Estimates annual committed effective doses
to a critical population group from less
restrictive disposal of BRC wastes by
sanitary landfill and incineration methods.
1.2 CHANGES IN VERSION 2.1
There are four improvements made to this version, (1)
addition of the daughter nuclide in-growth effects into the risk
assessment, (2) update of the dose and risk conversion factors to
1994 level, (3) addition of the annual mortality and risk
incidence calculation, and (4) adoption of the International
System (SI) units.
The dose coefficients are extracted from the RADRISK data
file (Du80) and the weighting factors are consistent with the
definitions used in ICRP Publications 26 (ICRP 77) and 30 (ICRP
79). The effective dose equivalent is the weighted sum of the
1-3
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50-year committed dose equivalent to the organs or tissues.
The cancer risk coefficients are calculated from radiation-
risk models which are based on 1980 U.S. vital statistics. The
genetic-risk coefficients for serious disorders to all subsequent
generations are calculated from the product of the average
absorbed dose to the ovaries and testes up to age 30 per unit
intake before that age. Risk coefficients of 2.60xlO'2 and
6.9xlO'2 Gy1 for low-LET and high-LET radiation respectively are
used for the calculation of risk conversion factors (EPA 89).
The Version 2.1 Operation System modifies the PRESTO-EPA-CPG
model by integrating the daughter nuclide in-growth effects into
the Version 2.0 model. The daughter nuclide in-growth effects
(DNIE) are calculated based on a crude assumption that the
sorption characteristics of the parent and daughter nuclides are
identical throughout the processes of leaching and groundwater
transport. The DNIE are adjusted annually by using the
correction factors derived from Bateman Equations (Ev55).
The adjustment for DNIE is performed only for those parent
nuclides designated and built into the model. To simplify the
modeling, the adjustment is carried up to 4-member decay chains.
The transport of daughter nuclides is not calculated in the
model.
1-4
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2. DESCRIPTION OF PRESTO-EPA-CPG MODEL
2.1 GENERAL DESCRIPTION OF THE MODEL
2.1.1 Description of a Disposal Site
The life cycle of a low-level waste disposal site begins
with site selection. Following site selection and regulatory
approval, trenches are dug on the site. Waste materials in
various types of containers are placed into each trench. Once a
section of the trench is filled, the trench is backfilled to
eliminate voids to decrease the potential for subsidence and
cracking of the trench cap. Following backfilling, the trench is
covered with a cap of soil or clay, one to several meters thick,
mounded above grade to facilitate runoff and decrease
infiltration.
In general, hydrologic transport is the principal pathway by
which the general public may become exposed to radioactivity from
LLW disposed in shallow trenches. Figure 2-1 is a schematic
description of the routes that water and any transported
radionuclides may follow from a trench in a LLW disposal site.
The major source of water is from precipitation. The
precipitated water at a site will either infiltrate into the
trench cap, run off the trench area by overland flow, or
evaporate into the atmosphere. The distribution of these
components will depend on the ground cover, steepness of the
slope, and other factors.
Hydrologic transport of radionuclides from a LLW disposal
trench may occur by the infiltrated water or by the overland
flow. The infiltrated water entering the trench leaches out
radionuclides from the waste matrix and becomes contaminated.
This contaminated water may either overflow from the top of the
trench or percolate downward through the bottom of the trench to
the subtrench soil zone and ultimately enter an aquifer.
Radionuclides that finally reach the aquifer will generally
be transported at velocities less than the flow velocity of the
water in the aquifer. This "retardation" is due to the
2-1
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interaction of radionuclides with solid media in the aquifer.
When the radionuclides being transported in the aquifer reach a
well, they will be consumed by residents through drinking,
irrigation, and cattle feed pathways. Residual radionuclides in
the aquifer are assumed to be transported further downstream and
impose additional health impacts to the downstream population.
PRECIPfTATION
ATMOSPHERIC TRANSPORT
RESUSPENSION
DEPOSITION
RUNOFF
DRINKING &
IRRIGATION
EXFILTRATION
STREAM
WELL
AQUIFER
RADIONUCLIDE TRANSPORT THROUGH AQUIFER
The contaminated water in the trench will accumulate if the
rate of infiltration from the cap exceeds the rate of
Figure 2-1. Environmental Transport Pathways used in
PRESTO-EPA models.
exfiltration out of the trench bottom. When the volume of water
accumulated in the trench exceeds the total void space in the
trench, overflow of trench water onto the ground surface occurs.
The radionuclides in the trench water will then mix with the
overland flow and be further transported into nearby streams.
This contaminated water will potentially be consumed by the local
2-2
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residents and by the population downstream via drinking,
irrigation, and cattle feed pathways.
Residents living near the site may also be exposed to the
radionuclides transported from the sites by atmospheric
processes. Radionuclides deposited on the soil surface by trench
overflow, by spillage during disposal operations, or by complete
erosion of the trench cap may be suspended in the atmosphere and
transported downwind where they may be inhaled or deposited on
the ground and vegetation. Deposited radioactivity may
contaminate crops, meat, and milk and enter the food chain.
Deposition on the soil surface may also result in external
radioactive exposure to humans.
2.1.2 Description of the Model
The model has been designed to calculate the maximum annual
committed effective dose (CED) to a critical population group
(CPG) from the disposal of LLW in an underground disposal
facility. The model simulates the transport of radionuclides
from the LLW trench to the environmental receptors and the human
exposures through food chain pathways. The doses for a CPG
are calculated from the radionuclide uptake rate and the dose
conversion factors which are precalculated from EPA's REDRISK
model and tabulated in a format established in EPA's DARTAB model
(Be81). The PC version of the model replaced the DARTAB submodel
with DOSTAB Submodel which is detailed in the following section.
The code was designed to accommodate a wide range of
hydrogeologic and climatic conditions. It can also handle waste
leaching and the groundwater transport of nuclides under
partially saturated as well as saturated hydrogeologic
conditions, while taking into account nuclide retardation due to
geochemical processes. The code has features to account for the
dynamic leaching process resulting from deterioration of waste
containers; the farming scenario which simulates farming over the
trench with root uptake of radionuclides from the waste matrix;
and the reduction in the source inventory due to radionuclide
decay during the operational period.
The effect of daughter nuclide ingrowth is incorporated in
the final results by multiplying the parent-nuclide-caused health
effects with its daughter nuclide in-growth effect correction
2-3
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factor which is defined in later section. Up to the fourth
member of the decay chain is included in this adjustment.
The radionuclides which are spilled from incoming waste
packages may remain on the ground surface at the close of
disposal operations. These radionuclides would subsequently be
transported either by the atmospheric pathway to the local
population or by the surface water pathway to the nearby stream.
The complex physical and chemical interactions between the
radionuclides and the solid geologic media have been grouped into
a single factor, the distribution coefficient (Kd) . Different Kj
values can be used for soil, trench material, sub-trench soil,
and aquifer.
The subsurface transport path of radionuclides is assumed to
be vertical from the trench bottom to the aquifer and then
horizontal through the aquifer. A one-dimensional quasi-steady
state flow field model is employed for both vertical and
horizontal reaches. The flow in the vertical flow reach is
calculated either as saturated or unsaturated flow, depending on
the relationship between the rate of exfiltration, the degree of
saturation, and the properties of the geologic media. An
empirical formula as developed by Clapp et al. is used for the
analysis.
Because of the inclusion of longitudinal dispersion effects
and the adaptability of irregular boundary conditions, a
numerical transport model is normally inevitable in analyzing the
radionuclide transport in an aquifer. By employing the
analytical model developed by Hung (Hu81), the tedious numerical
calculation is avoided. Hung's correction factor is used to
compensate for the effects of longitudinal dispersion. In
addition, since the model considers the leaching of radionuclides
from a disposal site an area source, a numerical integration
model is employed in analyzing the transport of radionuclides in
the aquifer underneath the disposal site.
Three types of submodels are used in the PRESTO-EPA-CPG
code: unit response, bookkeeping, and scheduled event. The unit
response submodels calculate the annual response of a given
process. For example, the submodel INFIL calculates the annual
infiltration through an intact trench cap. This annual
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infiltration is then apportioned among the transport processes by
the bookkeeping submodels. Other unit response models calculate
the annual average atmospheric dispersion coefficient and erosion
from the trench cap.
Bookkeeping submodels keep track of the results of unit
response submodels and user-supplied control options. For
example, the TRENCH submodel calculates the level of standing
water in the trench and the volume of water leaving the trench.
Annual concentrations of each radionuclide in environmental
receptors, such as well water or the atmosphere, are used to
calculate radionuclide concentrations in foodstuffs. Foodstuff
concentrations and average ingestion and breathing rates are
utilized to calculate the annual average radionuclide intake per
individual in the local population. These intake data are then
used to estimate dose rates.
The atmospheric transport submodel assumes that the entire
population resides within the same 22.5-degree sector. User-
specified parameters give the fraction of year that the plume
blows in that sector. The transport of the radionuclide from the
source area to a nearby population is calculated by employing the
Gaussian plume diffusion model. Therefore, each member of the
population will inhale the same quantity of each radionuclide.
Each person in the CPG is assumed to consume the same
quantities of food, all grown in the same fields, and obtains
his/her drinking and irrigation water from the same source; but
the user may specify the distribution of the sources of drinking
and irrigation water supplies between well and stream.
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SPILLAGE
OVERFLOW
GROUNDWATER TRANSPORT
1
SURFACE
WATER
BODY
BASIN
STREAM
BASIN
POPULATIOI
IRRIGATION
SOIL
PLANT UPTAKE
CROPS
AND
ANIMALS
I
DRINKING INGESTION DRINKING
HUMANS
OCEAN
SINK
2-6
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Figure 2-2. Hydrologic Transport Pathways,
2-7
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SURFACE
CONTAMINATION
ERODED
TRENCH
SUSPENSION
LL
AIR
INHALATION]
IMMERSION
HUMANS
(Local Population)
DEPOSITION
IRRIGATION FROM GROUND
INGESTION
CROPS
AND
GROUND
Figure 2-3. Atmospheric Transport Pathways.
2.2 MATHEMATICAL FORMULATIONS
Pathways for environmental transport of radionuclides
considered by the model are shown in Figures 2-2 and 2-3.
Transport pathways involving both surface water and groundwater
are illustrated in Figure 2-2. Water may leave the trench
through the exfiltration from the trench bottom or overflow from
the top of trench. Radionuclides in the spilled surface area may
be transported to a surface water body or to the aquifer through
deep underground seepage. The contaminated water may ultimately
reach the local population either from a well or from surface
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water.
The modelled atmospheric pathways for radionuclide transport
are illustrated in Figure 2-3. Material may reach the atmosphere
from the site soil surface contaminated by overflow or
operational spillage, or by the denuded trench following possible
erosion of the entire trench cap. A member of the population
residing in a local community may ultimately be impacted by
inhalation of or immersion in the suspended materials downwind,
by ingestion of crops contaminated following deposition on soil
or crops, or by direct irradiation from ground surfaces.
The model approach in calculating radionuclide
concentrations in the pertinent environmental receptors is
described in the following two sections.
2.2.1 Transport Pathways Involving Water
Infiltration Through Trench Cap
The basic model for simulating the annual infiltration
through the trench cap assumes a portion of the trench cap will
fail and allow the precipitated water to drain into the trench.
The fraction of the cap which fails is assumed to vary with time.
Due to the distinct nature of the infiltration mechanism
between the intact portion and the failed portion of the trench
cap, the annual infiltration through the trench cap is divided
into two components.
On the intact portions of the cap, the normal infiltration
rate is calculated by the method developed by Hung (Hu83b) which
is described in Appendix A. For the failed portion of the cap,
the infiltration equals to rainfall. Therefore, the volume of
water entering the trench annually is calculated by
Wt = At[fc-Pa + (1 - fc)Wa] (2-1)
where:
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Wt = volume of water entering trench in current year (m3) ,
At = area of trench (m2) ,
fc = fraction of trench cap that has failed (unitless),
Pa = annual precipitation (m) and,
Wa = annual infiltration (m).
The value of Wc is added to the standing trench water from
the earlier year to calculate the maximum depth of standing water
in the trench for the current year.
The component of annual infiltration through the intact
portion of the trench cap, Wa, is estimated by employing the
infiltration model developed by Hung (Hu83b, Appendix A). The
model simulates the rate of infiltration by solving system
equations which describe the dynamics of overland flow,
subsurface flow, and atmospheric dispersion systems. The basic
equations employed in the model are:
Q0 = { (Sin0)1/2 H5/3}/n (2-2)
dH/dt = P - E0 - q0 - Q0/L (2-3)
Ep when P + H/At > Ep
P + H/At when Ep > P + H/At > 0 (2-4)
. 0 when P + H/At = 0
Ks when P - E0 + H/At > Ks
P - E0 + H/At when Kg > P - E0 + H/At > 0 (2-5)
. 0 when P - E0 + H/At = 0
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Ks when Zg <
0 when Zg = Zn
(2-6)
dZg/dt = (q, - q0 + qt)/Wg
(2-7)
q, = -DeWp/Zp + Ke
- EO
qv = -(Ep - E0)
0.5Zr
1 +
0.66(W
-1
(2-8)
(2-9)
dZp/dt = -(qp + qc)/Wp
(2-10)
qt =
q0 when Zp > 0
. 0 when Zp = 0
and
where
qp = -Max ( q, , qv )
(2-11)
(2-12)
Q0 = rate of overland flow per unit width of trench
cover (m3/m-hr) t
H = average depth of overland flow over the entire trench
cover (m),
L = length of slope or half of trench width (m),
n = Manning's coefficient of roughness,
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e = average inclination of the trench cover (m/m),
P = rate of precipitation (m/hr),
E0 = rate of evaporation from the overland flow (m/hr),
q0 = rate of percolation from the overland flow system
(m/hr),
Ep = evaporation potential (m/hr),
qL = flux of moisture infiltrating into the trench (m/hr),
q, = flux of pellicular water transported in the liquid
phase (m/hr),
Ka = saturated hydraulic conductivity of the soil (m/hr),
Zg = deficit of gravity water (m),
max = maximum deficit of gravity water, equivalent to the
thickness of the trench cover (m),
Wg = component of wetness for the gravity water; under
a fully saturated condition, it is numerically
identical to the porosity for the gravity water
(unitless),
Wp = component of wetness for the pellicular water;
under a fully saturated condition, it is
numerically identical to the porosity for
pellicular water {unitless),
Zp = deficit of the pellicular water (m),
De = hydraulic diffusivity at equivalent wetness (m2/hr),
Ke = hydraulic conductivity at equivalent wetness (m/hr),
qv = flux of moisture being transported in the vapor
phase (m/hr),
qt = flux of moisture being transformed from gravity
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water to pellicular water (m/hr) and,
flux of pellicular water (m/hr).
The amount of annual infiltration through the trench cap is
then calculated by integrating the hourly infiltration over the
entire year.
Trench Cap Modifications
The trench cap may fail by erosion or mechanical
disturbance. In the case of erosion, the annual thickness of
material removed from the trench cap by sheet erosion is
calculated using an adaption of the universal soil loss equation
(USLE) (Wi65).
The annual amount of erosion is subtracted from the cap
thickness for the current year of simulation. If the remaining
thickness is less than 1 cm, the cap is considered to be
completely failed and fc is set to 1.0. The USLE may be written
as:
I, = fr-fk-f1-fs-fc-fp-fd (2-13)
where
I, = yearly sediment loss from surface erosion (tons/ha),
fr = rainfall factor (fr unit or 100 m-tons-cm/ha) ,
fk = soil erodiability factor (tons/ha/fr-unit) ,
fx = slope-length factor (unitless),
fg = slope-steepness factor {unitless),
fc = cover factor (unitless),
fp = erosion control practice factor (unitless), and
fd = sediment delivery factor (unitless).
2-13
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The parameterization scheme of McElroy, et al. (McE76) was
used to specify site-specific values of the factors in Equation
(2-13) . The rainfall factor, fr, expresses the erosion potential
caused by average annual rainfall in the locality. The soil
erodibility factor, fk, is also tabulated by McElroy, et al. as a
function of five soil characteristics: percent silt plus very
fine sand; percent sand greater than 0.1 mm; organic matter
content; soil structure; and permeability. The factors, f: and
fs, for slope-length and steepness account for the fact that soil
loss is affected by both length and degree of slope. The PRESTO-
EPA-CPG code usage of USLE combines both factors into a single
factor that may be evaluated using charts in McElroy, et al. The
factor, fc, represents the ratio of the amount of soil eroded
from land that is treated under a specified condition to that
eroded from clean-tilled fallow ground under the same slope and
rainfall conditions. The erosion control practice factor, fp,
allows for reduction in the erosion potential due to the effect
of practices that alter drainage patterns and lower runoff rate
and intensity. The sediment delivery ratio, fd, is defined by
McElroy, et al. as the fraction of the gross erosion that is
delivered to a stream. Units of I, are converted to (m/yr)
within the code. See Section 2.5 for the description of input
units.
The second method of trench cap failure is mechanical
disturbance due to human intrusion or some other means which
might completely destroy portions of the cap. This phenomenon
can be termed a partial failure, but in reality is a total
failure of some part of the cap. The code user may specify some
rate of cap failure as shown in Figure 2-4.
By specifying appropriate values for the time in Figure 2-4,
the user may selectively simulate the failure of the cap from a
portion of the trench area. Mathematically this function is
represented by
fc
p 0, if t < NYR1
(PCT2-PCTI)(t-NYRl)/(NYR2 - NYR1) + PCT1 (2-14)
if NYR1 S t S NYR2
PCT2 if t > NYR2
2-14
-------
Even though PCT2 might be less than 1.0 in year NYR2, the cap may
ultimately fail completely by virtue of erosion. As fc changes,
the amount of water added to the trench annually also changes.
PCT2
PCT1
NYR1 NYR2
TIME (Years)
Figure 2-4. Trench Cap Failure Function
The amount of water leaving the trench annually via the
trench bottom is calculated by:
VB = (DH + DIT
(2-15)
and
where
Dw = VH/CAT-
(2-16)
2-15
-------
VB = volume of water leaving trench bottom annually (m3/yr) ,
Dw = depth of water in trench during current year (m) ,
IT = permeability of material below the trench (m/yr) ,
AT = trench area (m2) ,
Vw = volume of water in trench (m3) ,
WT = porosity of trench contents (unit less) , and
L = length of saturated zone (m) .
Water will overflow the trench if the maximum depth of
standing water is greater than the trench depth. If this is the
case, the overflow is calculated by
V0 = (Dw - DT)AT-WT (2-17)
where
V0 = volume of water overflowing trench in a year (m3-) ,
DB = depth of water in trench (m) ,
DT = trench depth (m) ,
AT = trench area (m2) , and
WT = porosity of trench material (unitless) .
Water in the trench may be contaminated by contact with the
waste material. To calculate the concentration of radionuclides
in the trench water exfiltrating out of the trench, two model
types are used, a dynamic model based on the chemical exchange
and an empirical model based on the annual release fraction.
The user must choose one of the three options shown in Table
2-1 to calculate the concentration of radionuclides in the trench
water.
2-16
-------
Table 2-1 Leaching Options Specified for LEAOPT
Option
Leach Calculation Method
Chemical exchange without solubility limit
Chemical exchange with solubility limit
Annual release fraction
Leaching options, l and 2, utilize a dynamic model which
estimate the radionuclide concentration in the trench water based
on chemical exchange.
2-17
-------
The model is developed based on a multi-phase leaching
concept (Hu86b, Hu95) which simulates a leaching system under
field environment. The model assumes that the flow of
infiltration is concentrated in preference paths and, thereby,
forms a finger flow system. This flow system leads to the
transport of radionuclides in two phases, the convective phase
and diffusive phase. These phases of transport is assumed to
take place in convective zone and diffusive zone respectively.
The radionuclides in the diffusive zone must be transported to
the convective zone first before it can be transported downward
through convective process.
Due to the complexity in the modeling of the multi-phase
leaching concept, a simplified and yet conservative model is
used. The simplified model assumes an idealized steady uniform
leaching model to calculate the radionuclide concentration in the
trench water based on chemical exchange process. A correction
factor is then added to account for the leaching process under
field conditions derived from the multi-phase leaching concept
(Hu86b). The final formula is expressed by:
IT-FAC
(Chemical exchange option) (2-18a)
and
FAC = Min [TINFL/PERMT, 1] (2-18b)
where
FAC = a correction factor to account for the multi-phase
leaching phenomenon experienced in field conditions,
TINFL = annual infiltration rate (m/yr),
PERMT = trench hydraulic conductivity (m/yr),
2-18
-------
On, = concentration of radionuclide in trench water (Ci/cm3) ,
IT = amount of activity in trench (Ci),
AT = trench area (m2) ,
WT = porosity within trench (unitless),
DT = trench depth (m),
Kd2 = distribution coefficient within waste for radionuclide
(ml/g), and
pw = density of waste material (g/cm3) .
Leaching option 2 uses a solubility factor to estimate the
maximum concentrations of radionuclides in the trench water. The
solubility option may be used when the radionuclide solubility is
low or information concerning Kd values is not available. The
concentration of the radionuclide is estimated by:
r S«NCNV IT-FAC
:„ = Min ,
M D^WT + ATDTKd2pw J
(Solubility Option) (2-18c)
in which,
S = elemental solubility (g/ml)
M = mass of radionuclide (g/mole)
Nc = ratio (Ci/mole)
Nv = ratio (ml/m3)
Leaching option 3 allows the user to input an average annual
fractional release of the total radionuclide inventory. This
fraction is applied to each radionuclide and does not consider
2-19
-------
either Kd or solubility. Leaching option 3 is normally used for
a solidified waste form. The model calculates the primary
release of radionuclide from the waste form by using a user-
specified constant-fractional leach rate. To accommodate the
hydrodynamic effects, the released radionuclides are then
adsorbed by the waste form according to Equation 2-18a to
calculate the actual rate of release out of the trench. This
calculation accounts for the adsorption effects inside and
outside of the waste form.
Waste containers can inhibit nuclide leaching until they
lose their integrity. The duration for the containers to lose
their integrity, container life, depend on their design,
structural strength, and material. In PRESTO-EPA-CPG, the net
radionuclide release is calculated by multiplying the
radionuclide concentration in the trench water by the fractional
container fracture factor (CFF) that is time dependent. The
fraction CFF is set to zero while all of the containers are
intact. Once the containers start to fracture, CFF is assumed to
increase linearly to a maximum value of 1, which represents
failure of all of the containers.
Transport Below Trench
Once radionuclides have been leached out of the waste in the
trench and have migrated through the surrounding trench walls or
bottom, they are transported vertically downward to the aquifer
and then horizontally through the aquifer to a well. The
velocity of radionuclide transport is retarded, relative to the
movement of water, by vertical and horizontal retardation
factors, Rv and RH, as explained below.
Because of the distinct nature of radionuclide transport in
various reaches, the model subdivides the transport field into
three reaches, vertical reach, collection reach, and horizontal
reach. The solute transport analyses for each reach are
conducted as detailed in the following subsections.
Vertical Reach
The groundwater flow in the vertical reach is assumed to be
saturated or partially saturated. The degree of saturation is
2-20
-------
used to calculate the water velocity, Vv and the vertical
retardation factor, Rv. The degree of saturation, SSAT, is
either read in as an input parameter or calculated from the
equation:
, ATINFL, ° "
SSAT = RESAT + (1-RESAT) (2-19a)
[ PERMV J
where
RESAT = residual moisture content, expressed in a fraction of
total water content when saturated (unitless)
ATINFL = average exfiltration rate (m/yr)
PERMV = vertical saturated hydraulic conductivity (m/yr)
Equation (2-19a) is based on approximate expressions for the
fraction of saturation (Cla78, McW79). The exponent, 0.25, is
generally a function of soil type, but has been assigned a
conservative fixed value for simplicity. The residual moisture
content, RESAT, is an input parameter that is generally identical
to the input parameter Wp of the INFIL submodel. The parameter
ATINFL is the average trench exfiltration rate. When there is no
overflow of trench water, the rate is calculated by the
expression
ATINFL = [PCT2-(PPN+XIRR)+(2-PCT2)-XINFL]-0.5 (2-19b)
where
PCT2 = maximum fraction of trench cap failure (unitless)
PPN = annual precipitation rate (m/yr)
XIRR = annual irrigation rate (m/yr)
XINFL = infiltration rate through the intact trench cap (m/yr)
(calculated by the INFIL subroutine)
2-21
-------
Vertical water velocity Vv (m/yr), and the vertical
retardation factor Ry (unitless) are calculated as follows:
Vv = ATINFL/(PORV«SSAT) (2-19c)
RV = 1 + (BDENS«XKD3)/(PORV«SSAT) (2-19d)
where
BDENS = host formation bulk density (g/cm3)
XKD3 = distribution coefficients for the host formation (ml/g)
PORV = subsurface porosity (unitless)
Horizontal Reach
The transport analysis for the horizontal reach calculate
the radionuclide transport in the aquifer without lateral or
vertical supply of radionuclide flux. The transport analysis
employs Hung's groundwater transport model (Hu81, Hu86, Appendix
B). The basic equations for the model, as adopted from Hung,
are:
Q = nQ0(t-RL/V) Exp(-XdRL/V) (2-20a)
and
oo
f 0.5 (RP/n63)1/2 Exp [-Nd6- (P6/4R) (R/0-1) 2] d9
Jo
n =
Exp(-RNd)
Exp[P/2 - (P/2) (1 + 4RLXd/PV)1/2]
(2-20b)
Exp(-RLXd/V)
where
2-22
-------
ri = Hung's correction factor, a correction factor to
compensate for the dispersion effect
R = retardation factor
P = Peclet number, VHDH/d
6 = dimensionless time, TV/L
Nd = decay number, XdL/V
L = flow length, Dv or DH (m)
V = water flow velocity, Vv or VH (m/yr)
t = time of simulation (yr)
d = dispersion coefficient (m2/yr)
Xj = radiological decay constant (yr'1)
T = dummy time variable (yr)
Q = rate of radionuclide transport at the point of
interest, which is at well point in this case (Ci/yr)
Q0 = rate of radionuclide released at the upstream reach,
which is at the downstream edge of a disposal site
(Ci/yr)
In the above equation, the horizontal retardation factor,
RH/ is calculated by
RH = 1 + (BDENS»XKD4)/PORA
in which
XKD4 = distribution coefficient of the aquifer (ml/g)
PORA = aquifer porosity (unitless)
2-23
-------
Collection Reach
This analysis calculates the rate of radionuclide transport
in the aquifer while receiving the radionuclide flux from the
vertical reach. The primary interest of the analysis is to
calculate the rate of radionuclide transport at the downstream
edge of the site boundary.
The basic equation used to calculate the rate of transport at
the site boundary is expressed as:
C(t) =
JO V X V a
(2-21)
in which
Q = rate of radionuclide transport at the downstream edge
of the disposal site (Ci/yr)
B = width of the disposal site measured in the direction
perpendicular to the ground water flow (m)
L = length of the disposal site in the direction of ground
water flow (m)
n(x)= Hung's correction factor for the flow reach from the
downstream edge of the disposal site to the point of
integration
q = radionuclide flux entering the aquifer at the point of
integration {Ci/yr/m2)
U = unit step function
To simplify the calculation, Hung's correction factor,
is assumed to be equal to one in the actual model analysis. This
approximation is acceptable because the length of the integration
reach should not exceed the length of disposal site which is
relatively small and the n(x) value is always practically 1.0
under normal application. Furthermore, the model takes the
2-24
-------
segment of integration, dx or Ax, to be one tenth of the length
of the disposal site in conducting the numerical integration.
Radionuclide Breakthrough Time
The breakthrough time, which is the time required for a
radionuclide to travel from the bottom of the trench to the well,
is the sum of the vertical and horizontal transit times. From a
practical view point, the breakthrough time is approximated in
the model by assuming the radionuclide leaching is from a point
source and by assuming the dispersion effect on the radionuclide
transport can be neglected.
The vertical and horizontal transit time, tv (yr), and tH
(yr), are calculated according to
DVRV
tv = , tH = (2-22)
Vv VH
where:
Dv = distance from trench to aquifer (m)
DH = length of aquifer flow from trench to well (m)
Vv = vertical water velocity (m/yr)
VH = water velocity in aquifer (m/yr)
and retardation factors, Rv and RH, are as previously defined.
Concentration in the Well Water
Since the well point receptor for the calculation of maximum
annual committed effective dose is, in general, fairly close to
the edge of the disposal site, the concentration of the well
water may vary considerably with the depth of the well screen
installed.
2-25
-------
The PRESTO-EPA model assumes that the well screen is
installed at the bottom of the aquifer, which is the most
reasonable assumption based on the current well drilling practice
and the State's well water regulation in the United States.
Furthermore, the model also assumes that all of the radionuclide
are uniformly distributed over the entire depth of aquifer. This
assumption tends to over-estimate the concentration of
radionuclide and is considered to be a conservative approach.
To calculate the radionuclide concentration at the well
point, the rate of groundwater flow at the well point is
calculated first. By considering the lateral dispersion of the
flow, the total rate of flow available for dilution is calculated
by:
WA = VAPADA[V/2 + 2«tan(a/2)DH] (2-23a)
where
WA = the rate of contaminated water flow in the plume at the
well point (mVyr)
VA = groundwater velocity (m/yr)
PA = porosity of aquifer material (unitless)
DA = thickness of the aquifer (m)
a = constant angle of spread of the contaminant plume in
the aquifer (radian)
AT = trench area (m2)
DH = trench-to-well distance (m)
The angle "a" is the dispersion angle of a contaminated
plume in the water in an aquifer. This dispersion angle may be
empirically determined (e.g., by field dispersion tests wherein
the angle of dispersion is determined from measurements of
chemical, conductivity, or radioactivity tracers in water from a
series of bore holes downstream across the plume), or it may be
2-26
-------
estimated. The use of a dispersion angle is consistent with
published characterizations of the horizontally projected profile
of a chemical contamination front as it moves through an aquifer
(Sy81).
The radionuclide concentration in the well water, Cw
(Ci/m3) , is then calculated by
CB = Q/WA (2-23b)
Rate of Water Consumption
The total water demand, VUf including drinking water, cattle
feed, and crop irrigation, is calculated by
V0 = [S.gE-T'W^Ii! + UWLH + 1.5E4»LA]Np (2-24)
where
Vu = annual well water demand in liters (I/person-yr)
3.9E7 = 4492 m2 irrigated per person X 8760 hr/yr
Wx = irrigation rate per unit area (l/m2-hr)
fI = fraction of year when irrigating (unitless)
UB = individual annual water consumption (1/person-yr)
LH = fraction of drinking water obtained from well water
1.5E4 = water fed to cattle consumed by humans (I/person-yr)
LA = fraction of cattle feed water obtained from well water
Np = size of the population (persons)
L! = fraction of irrigation water obtained from well water
2-27
-------
If the calculated total water demand, Vul exceeds the flow
rate of the contaminated plume, WAI the concentration of
radionuclides in the pumped out water is recalculated using the
actual volume of pumping to correct for the dilution effect from
the noncontaminated groundwater. Units of Vu are converted to
cubic meters within the code.
The calculated concentrations of radionuclides in well water
are averaged over the length of the simulation and used by the
food chain and human exposure parts of the code for the drinking
water and cattle feed pathways.
Trench Overflow Transport and Stream Contamination
As previously mentioned, water will overflow the trench
onto the soil surface when the maximum depth of standing water is
greater than the trench depth. If this occurs, radionuclides
will be added to the surface inventory of radionuclides deposited
by initial operational spillage. The surface soil will then have
a component adsorbed by the soil with concentration Css (Ci/kg)
and a component of contaminated water in the surface soil of Csw
(Ci/m3) . The material adsorbed by the soil will remain in the
soil and becomes a source term for resuspension and atmospheric
transport (this process is discussed in Section 2.2.2). The
contaminated water in the surface soil is available to enter
nearby surface water bodies via overland flow, or percolate down
to the aquifer.
Radionuclides dissolved in the soil water may either be
transported to the stream by overland flow or to the deep soil
layers by percolation. The amount of each radionuclide added to
the stream is represented by the product of Csw, the radionuclide
concentration in the surface soil water, and the annual volume of
runoff from the contaminated soil surface, WSTREM. The value of
Csw for each radionuclide is calculated by
1000»IS
:SM = (2-25)
KdlMs + MM2/Pw
where
2-28
-------
Csw = radionuclide concentration in surface soil water
(Ci/m3) ,
Is = amount of radionuclide on surface (Ci),
Kj,! = distribution coefficient for surface soil region
(ml/g),
Ms = mass of soil in contaminated region (kg),
MW2 = mass of water in contaminated soil region (kg),
pw = density of water (g/cm3) , and
1000 = conversion factors used for Kd(l ml/g = 1 m3/1000 kg)
and for pw (1 g/cm3 = 1000 kg/m3) .
Equation 2-25 is used to compute the concentration of
radionuclides in the surface soil interstitial water.
The radionuclide concentration in the contaminated surface
soil region, Css, is calculated using
Css = CSMKdl/1000 (2-26)
The contaminated region of surface soil is defined by the
user in terms of length, SL (m) ; width, Sw (m) ; and depth, SD (m)
These parameters allow the calculation of soil mass (Ms) and the
water mass (Mw) in the contaminated soil region by
Ms = 1000«psSwSLSD; Mw = 1000»WSSWSLSD (2-27)
where
ps = soil bulk density (g/cm3)
Ws = soil porosity (unitless)
1000 = conversion factor for the mass of soil and water
2-29
-------
Water falling on the contaminated soil region may either
evaporate, run-off, or infiltrate. Of the liquid, a certain
fraction of the total precipitation, fr, will enter the stream
annually.
The amount of water that enters the stream from runoff of
the contaminated region is given by
Ws = ftPSvSL. (2-28)
The amount of water that enters deep soil layers and eventually
the aquifer is given by
WD = WaSMSL (2-29)
where Wa is the yearly infiltration rate for the farmland.
The annual amount of radionuclides moving from the
contaminated surface soil region to the stream, Rs, is then the
product of Ws and the radionuclide concentration in the surface
soil water Csw, (Equation 2-25) . The amount of each radionuclide
annually entering the deep soil layers from the contaminated
surface soil region is the product of WD and CSH. The concen-
tration of radionuclides in the stream is the quotient of Rs and
the annual flow rate of the stream.
As with water removal from the well, the amount of each
radionuclide removed from the stream is conserved by using
Ir = [3.9E7«WIfISI + UWSH + 1.5E4»SA]»NP»CRM (2-30)
where
Ir = annual amount of nuclide removed from stream (Ci)
CRW = radionuclide concentration in stream (Ci/m3)
ST = fraction of irrigation water obtained from stream
2-30
-------
SH = fraction of drinking water obtained from stream
fraction of cattle feed water obtained from stream
Other parameters are the same as defined for
Equation 2-24.
If Ir is larger than the annual input of that nuclide to the
stream, Rs, then the radionuclide concentration in the stream is
recalculated referencing the water volume removed from the stream
rather than the stream flow by
CRW = RS/V0. (2-31)
Mean concentrations of each radionuclide in well water and
stream water are calculated for the appropriate number of
simulation years by dividing the sum of the annual radionuclide
concentrations in the well water and the stream water by the
length of the simulation.
2.2.2 Atmospheric Transport Sources and Pathways
For some sites, atmospheric transport of radionuclides may
be a major transport mechanism. Therefore, careful consideration
is given to obtain an accurate atmospheric transport model. On
the other hand, one of the goals in developing the PRESTO-EPA-CPG
is to minimize the complexity of input data. A compromised
solution to achieve these conflicting goals is to employ a
simplified and compact algorithm for the model. A model assuming
the population is concentrated into a single, small community,
and allow the code user to enter an externally computed
population average value, the air concentration, X, to source
strength, Q, ratio. An example of a code which could be used for
determining this ratio, X/Q, is AIRDOS-EPA (Moo79).
In most cases, the uncertainties in the computed atmospheric
source strength for contaminated areas are larger than the
differences between the internally computed and externally
determined (using a code such as AIRDOS-EPA) X/Q ratios. Use of
an external code has several advantages; the most salient being
2-31
-------
that explicit specification of complex population distributions
and the site wind rose removes the possibility of the code user
making errors of judgement in determining population centroid.
Internal Model Capability and Formulation
The atmospheric transport portion of the code will be
discussed in two parts: (a) a description of source strength
computation and (b) a discussion of the calculation of
atmospheric concentration at the residence site of the specified
at-risk population. For most applications, the model is expected
to be applied to a site of known population distribution, and the
user must input geographical and meteorological parameters
characterizing the population site and its relationship to the
low-level waste disposal area. The formulation of atmospheric
transport discussed herein is not intended to automatically
identify regions of high risk; rather, it is formulated to
calculate risk-related parameter values for a particular site.
Where population health effects are to be determined, the
geometric population centroid specified by the user is the point
for which a 22.5-degree sector average ground-level air
concentration is determined. A mean yearly value for the sector-
averaged atmospheric concentration is computed by PRESTO-EPA-CPG
and is input to DOSTAB for use in computing population health
effects.
The most common approach used for estimating the atmospheric
concentration and deposition of material downwind from its point
of release is the Gaussian plume atmospheric transport model
(S168). This approach is versatile and well documented. We have
chosen to incorporate a Gaussian plume transport code called
DWNWND (FiSOa) as a module, in subroutine form, in the PRESTO-
EPA-CPG code.
User inputs for the atmospheric transport simulation allow
specification of a surface radionuclide concentration at the
waste disposal site. Parameters used here include the initial
surface radionuclide inventory and the chemical exchange
coefficient for surface soils. The portion of radionuclides
sorpted onto soil particles is considered available for
transport. A source strength is computed based either on a time-
dependent (monotonically decreasing) resuspension factor or a
2-32
-------
process-dependent mechanical suspension variable. The given LLW
site is described by meteorological variables including:
FM = fraction of the year wind blows toward at-risk
individuals,
H = source height (m),
HL = lid height (m),
S = stability class,
Td = type of dispersion formulation,
Hr = Hosker roughness parameter (m) (about .01 of the actual
physical roughness),
u = wind velocity (m/s),
Vd = deposition velocity (m/s),
Vg = gravitational fall velocity (m/s), and
x = distance from source to receptor (m).
Source Term Characterization
The release rate for atmospheric transport is termed the
source strength. In PRESTO-EPA-CPG, the source strength is
directly dependent on the surface soil-sorpted radionuclide
concentrations from operational spillage and trench overflow, CG
(Ci/m2) . The source strength is the arithmetic sum of two parts:
a time-dependent resuspension factor, Re, (An75) and a
resuspension rate, Rr, (He80).
First, the wind-driven suspension component is described.
If the time-dependent resuspension factor is defined as
Re = RelExp(Re2T1/2) + Re3 (2-32)
2-33
-------
where T is elapsed time (days) and Re has units of inverse
meters, then the atmospheric concentration above the site, CA, is
given by
CA = ReCG (2-33)
and
CG = 1000«CspsSD (2-33a)
Using Anspaugh's values of 1E-4, -0.15, and 1E-9 for Rel,
Re2, and Re3, respectively, the value of Re calculated as above is
probably conservative for humid sites. As additional data from
humid sites become available, model users may wish to update the
equation used for computing Re.
The value of elapsed time appearing in Equation 2-32 is
computed from the start of the simulation. It is, therefore,
correct for the initial surface inventory, but not for
incremental additions thereto, which may occur at later times.
However, when later additions result from trench overflow, they
will likely consist of dissolved material and would likely act as
surface depositions of mobile particulate. It is, therefore,
assumed that a steady-state asymptotic value of Re is for most
sites appropriate for later additions to the surface inventory.
The user wishing to specify a time independent windblown
resuspension factor may do so by setting the values of Rel and Re2
to zero. When this is done, determination of windblown
suspension of all contributions to the surface inventory will be
treated identically, regardless of time of occurrence.
In the above expression, CA is the atmospheric concentration
of radionuclide immediately above the site at a height of about
one meter (Shi76), for a site of large upwind extent. Large
upwind extent may be interpreted as exceeding the atmospheric
build-up length, given by u HD/Vg, where u is wind velocity in
m/s, HD is the mixing height ( = 1 m) , and Vg is the gravitational
fall velocity. The representative site extent used in the
PRESTO-EPA-CPG code is the square root of the site area, A (which
is characterized by SLSM), and a tentative correction fraction,
F. The correction factor is computed using the equation:
2-34
-------
F = [V_(SLSM)1/2/uHD] .
(2-34)
With the stipulation that the value used for F may not
exceed unity, the source term component (Ci/s) for windblown
suspension is given by:
Qr = CAHDuFA1/2.
(2-35)
The second source component results from mechanical
disturbance of site surface soil. Mechanical disturbance occurs
during a user-specified interval. Within this interval, the
fraction of time per year that the disturbance occurs is Fmech.
The source term component for mechanical disturbance is the
resuspension rate, Rr, having units of inverse seconds, as:
mech
(2-36)
The net source strength for the site is the sum of these
components:
Q = Qr + Q,
'mech
(2-37)
Transport Formulation
The PRESTO-EPA code uses a Gaussian plume atmospheric
transport model, which is an extension of an equation of the form
(S168)
y2
x =
Exp --
Exp --
2nuayaz
z-H
oz
+ E
(2-38)
2-35
-------
This equation describes Gaussian distribution, where X
represents the radionuclide concentration, Q the source strength,
and H the corrected source release height to be discussed later.
Dispersion parameters, ay and az, are the standard deviations of
the plume concentration in the horizontal and vertical
directions, respectively. The aerosol is assumed to be trans-
ported at a wind speed (height-independent), u, to a sampling
position located at surface elevation, z, and transverse
horizontal distance, y, from the plume center. Mass conservation
within the plume is insured by assuming perfect reflection at the
ground surface. This is accomplished by the use of an image
source at an elevation -H, which leads to the presence of two
terms within the braces, and to the factor 1/2. A correction for
plume depletion will be discussed later. Equation 2-38 may be
obtained from any of several reasonable conceptual transport and
dispersion models.
Atmospheric transport at several sites of possible interest
to individuals evaluating consequences of radionuclide transport
has also been considered elsewhere. These sites include Hanford,
Washington (Fi81, Mi81), Savannah River, South Carolina (FiSOb),
and Brookhaven, New York (Si66).
Implicit in Equation 2-38 is the assumption that the plume
centerline height is the same as the release height, H. In
practice, the plume may be considered to originate at some
height, H, with respect to the population at risk. Some
situations, such as the existence of a ridge between the disposal
site and the population centroid, may dictate use of an effective
height greater than H, e.g., the ridge height. The plume thus
has an effective height, Heff, at which the plume may be
considered to originate. This effective value should be used
instead of the actual stack height as the starting point of
Gaussian plume calculations. If the particulate in the effluent
has an average gravitational fall velocity, Vg, the plume
centerline will tilt downward with an angle from the horizontal,
the1 tangent of which is Vg/u. The elevation of the plume
centerline at a distance x downwind is then
H = Heff - xVg/u (2-
39)
for H ;> 0
2-36
-------
and it is this corrected value that is used to compute the
aerosol concentration at a distant point.
Effects of a Stable Air Layer on Transport
The Gaussian plume formulation has been modified for use in
PRESTO-EPA-CPG to account for the presence of a stable air layer
at high altitudes. Upward dispersion of the plume subsequent to
release is eventually restricted when the plume encounters an
elevated stable air layer or lid at some height HL. Pasquill has
summarized some reasonable approximations to the modified
vertical concentration profile for various ranges downwind which
are used here (Pa76) . The limiting value of az may be defined as
az(limit) = 2 (HL - H/2)/2.15. (2-40)
This equation follows from setting the ground-level contribution
to the plume from an image source located above the stable air
layer to one-tenth the value of the plume concentration. It is
assumed that the limiting value of az calculated in this manner
is correct for distances beyond this point. For shorter downwind
distances, where the vertical dispersion coefficient oz is less
than az(limit), the Pasquill-Gifford value of oz is used. For
greater downwind distances, where az is greater than or equal to
az(limit), the value of oz(limit) given in Equation 2-40 is used
instead. The lid height is a user-specified value in the PRESTO-
EPA-CPG code. For LLW applications, the source height will
usually be sufficiently low that the influence of HL will be
small. For some sites, however, the influence of an intervening
ridge may necessitate a larger effective source height.
Effects of Plume Depletion
The plume is depleted at ground level during travel as the
particulates are deposited. Both fallout and electrochemical
deposition may be important considerations, and ground cover
characteristics are of major importance. Under certain obvious
conditions, washout is also of importance, but those conditions
have not been included within this model. Fallout is partially
2-37
-------
quantified in the Vg term defined earlier. At near ground level,
the deposition process is often characterized by a deposition
velocity Vd (Gif62, Mu76a, Mu76b). The deposition rate W is
defined by
W = Vd X, (2-41)
where
X = radionuclide concentration in air (Ci/m3) .
The magnitude of the plume depletion within the downwind
sector may be found by integrating the deposition across the
entire plume. Using Equation 2-38 and setting z = 0, it is found
that
dQ/dx = f VdXdy
(VdQ/unayaz)Exp[-(y2/2ay2) - (H2/2az2)]dx (2.42)
By performing the indicated quadrature across the plume and
further integrating along the longitudinal direction to express
the loss of release agent as a multiplicative factor, it can be
shown (Mi78) that the ratio of the air concentration considering
deposition processes, Xj, to the air concentration without
regarding deposition, X, is
x
Fd = Xd/X = Exp{-(2/n)1/2Vd/u f (l/az)Exp[-H2/(2az2]dx} (2-43)
J 0
Since az is a complicated empirical function of x, Equation 2-43
must be evaluated numerically.
2-38
-------
In the PRESTO-EPA-CPG applications, the average value of
radionuclide concentration X across a 22.5-degree downwind sector
is the desired quantity. In this case, the transsector
integration leads to the value 2.032 in the air concentration
equation (Cu76). This value includes the l/2n factor in Equation
2-38.
In conclusion, assuming that the radionuclide distribution
is that of a Gaussian plume, we may compute the mean radionuclide
concentration, X, at ground level for the 22.5-degree downwind
sector by
X= (2.032FdFwQ/UXOz)Exp[-(H2/2az2] . (2-44)
The value of H in Equation 2-44 must be an effective source
height. This value is corrected in the model for plume tilt as
in Equation 2-39 and the accompanying discussion. In the code, H
is on the order of 1 m for reasonably flat sites but, in many
other cases, different values should be used to account for local
site characteristics; e.g., for the presence of updrafts.
It has been noted that the choice of plume dispersion
parameter oz is a user option in the PRESTO-EPA-CPG code. Choice
of appropriate parameterization depends on site meteorology,
topography, and release conditions. The DWNWND code (FiSOa),
which has been included as part of the model, includes a choice
of eight parameterization schemes for plume dispersion and a
choice of six stability classifications. The most often used
dispersion parameterization scheme for the Gaussian plume is the
Pasquill-Gifford model. This is the approach most appropriate
for the assessment of long-term performance of LLW disposal
sites. Likewise, unless site-specific meteorology dictates
otherwise, the D stability category, denoting a neutral
atmosphere, should be used.
Pasquill (Pa61, Pa74) considered ground-level emission
tracer studies and wind-direction fluctuation data and developed
dispersion parameterizations for six atmospheric stability
classes ranging from A, most unstable, through F, most stable.
Pasquill's values are approximate for ground-level emissions of
low surface roughness (Vo77). These values were devised for
small distances to population (<1 km). The so-called Pasquill-
Gifford form of this parameterization (Hi62) has been tabulated
2-39
-------
by Culkowski and Patterson (Cu76), and is used in this model.
2.2.3 Food Chain Calculations
Mean concentrations of radionuclides in air, stream water,
and well water are calculated by using the equations listed in
Sections 2.2.1 and 2.2.2. This section describes how
radionuclides in those environmental media are used to calculate
human internal exposure and potential health effects.
Radionuclides in water may impact humans by internal
exposure, directly from use of drinking water or indirectly from
use of irrigation water used for crops. Radionuclides in air may
impact humans by either external or internal radiological doses.
External doses may result from immersion in a plume of
contaminated air or by exposure to soil surfaces contaminated by
deposition from the plume. Internal doses may result from
inhalation of contaminated air or ingestion of food products
contaminated by deposition from the plume. Dose and mortality
risk calculations are made by the DOSTAB subroutine which is
modified from DARTAB program (Be81). Radionuclide related input
to DOSTAB consists of the constant concentrations in air (person-
Ci/m3) , constant concentrations on ground surface (person-Ci/m2) ,
constant collective ingestion rate (person-pCi/yr) and constant
collective inhalation rate (person-pCi/yr). Calculation of these
variables follows.
Concentrations of radionuclides in air which affect the
population or an individual are calculated as described in
Section 2.2.2. It is assumed that the mean nuclide
concentrations in air are constant during the total period of the
simulation, as required, for input to DOSTAB.
Concentration of each radionuclide on the ground surface,
Qs(PCi/m2) is calculated using
Qa = CSP + CSPO, (2-45)
where
Qg = concentration of radionuclide on the ground surface at
2-40
-------
the populated area of interest (pCi/m2)
CSP = radionuclide concentration in the soil used for farming
due to atmospheric deposition (pCi/m2)
CSPO= radionuclide concentration in the soil used for farming
due to irrigation (pCi/m2)
Appropriate unit conversions are made within the code.
The inhalation rate of radionuclides is calculated by
multiplying the generic individual inhalation rate by the
concentration of radionuclides.
Qinh = UaCA, (2-46)
where
Qmh = rate of inhalation exposure (Ci/yr)
Ua = inhalation rate (m3/yr)
CA = mean ground level radionuclide concentration at a point
of interest (Ci/m3)
The units of Qinh are converted to person-pCi/yr by the population
size for input to the DOSTAB subroutine.
The ingestion rate is the input to DOSTAB that requires the
most calculation. Ingestion includes intake of drinking water,
beef, milk, and crops. Except for drinking water, all of these
media may be contaminated by either atmospheric processes or by
irrigation.
The atmospheric deposition rate onto food surfaces or soil
that is used in subsequent calculation of radionuclide content in
the food chain is
d = 3.6E15»CAVd, (2-47)
where
2-41
-------
d = mean rate of radionuclide deposition onto ground or
plant surfaces (pCi/m2»hr) ,
CA = mean ground-level radionuclide concentration at the
point of interest (Ci/m3) ,
3.6E15= conversion factor, sec-pCi/hr-Ci, and
Vd = deposition velocity (m/sec).
The following equation estimates the concentration, Cv, of a
given nuclide in and on vegetation at the deposited location
(except for H-3 and C-14) :
Cv = d-R[l-Exp(-Aete)]/(YvAe) + (B»CSP/P)Exp(-Xdth) (2-
48)
where,
Cv = the radionuclide concentration in pCi/kg,
d = mean rate of radionuclide deposition onto ground or
plant surfaces (pCi/m2»hr) ,
R = the fraction of deposited activity retained on crops
(unitless),
Ae = effective removal rate constant for the radionuclide
from crops (hr'1) , which is the sum of the radioactive
decay constant and the removal rate constant from
weathering, \,
te = the time period that crops are exposed to contamination
during the growing season (hr),
Yv = the agricultural productivity or yield [kg (wet
weight) /m2] ,
B = the radionuclide concentration factor for uptake from
soil by edible parts of crops, [pCi/kg (dry weight) per
pCi/kg dry soil],
2-42
-------
CSP = soil radionuclide concentration updated yearly
(pCi/m2) ,
P = the effective surface density for topsoil [kg(dry
soil) /m2] , and
th = time interval between harvest and consumption of the
food (hr).
In the above equation, the value of CSP is calculated by:
CSP = (CSPL + d-At)Exp[-(Xd + Xs)At]
where
CSP = soil radionuclide concentration for this year (pCi/ma) ,
CSPL = soil radionuclide concentration for last year (pCi/m2) ,
d = mean rate of radionuclide deposition (pCi/m2-yr) ,
Xd = radioactive decay constant (yr'1) ,
Xg = rate constant for contaminant removal (yr'1) ,
At = time increment, equal to one year in PRESTO model,
If farming is performed on the trench site, then the soil
radionuclide concentration is calculated as:
SOCON = 1E12»SD(CSMWS + 1000»Cssps)
where
SOCON = soil radionuclide concentration (pCi/m2) ,
SD = depth of contaminated surface region (m),
Csw = radionuclide concentration in interstitial water of
contaminated surface region (Ci/m3) ,
2-43
-------
Ws = porosity of surface soil (unitless) ,
Css = radionuclide concentration in soil of contaminated
surface region (Ci/kg) ,
pg = bulk density of surface soil (g/cm3) ,
1E12 = pCi/Ci, and
1000 = (kg/g) • (cm3/m3) .
The rate constant for contaminant removal from the soil, X3,
is estimated from
As = - , (2-49)
(0.15) (8760) { (1 +
where
Ag = removal rate coefficient (hr*1) ,
rg = watershed infiltration (m/yr) ,
ps = soil bulk density (g/cm3) ,
Kd = distribution coefficient (ml/g) ,
Ws = porosity (unitless) ,
0.15= depth of soil layer (m) , and
8760 = hr/yr.
Equation 2-48 is used to estimate radionuclide
concentrations in produce and leafy vegetables consumed by humans
and in forage (pasture grass or stored feed) consumed by dairy
cows, beef cattle, or goats.
The concentration of each radionuclide in animal forage is
calculated by use of the equation
2-44
-------
Cf = fpfsCp + (1 - fpfs)Cs/ (2-
50}
where
Cf = the radionuclide concentration in the animal's feed
(pCi/kg),
Cp = the radionuclide concentration on pasture grass
(pCi/kg) calculated using Equation 2-48 with th = 0,
Cs = the radionuclide concentration in stored feeds in
pCi/kg, calculated using Equation 2-48 with th = 2160
hr or 90 days,
fp = the fraction of the year that animals graze on pasture
(unitless),
fg = the fraction of daily feed that is pasture grass when
the animals graze on pasture (unitless),
The concentration of each radionuclide in milk is estimated as:
Cm = FmCfQf«Exp(-Adtf) (2-51)
where
Cm = the radionuclide concentration per liter in milk
(pCi/1),
Cf = the radionuclide concentration in the animal's feed
(pCi/kg),
Fm = the average fraction of the animal's daily intake of a
given radionuclide which appears in each liter of milk
(d/1),
Qf = the amount of feed consumed by the animal per day (wet
kg/d),
tf = the average transport time of the activity from the
feed into the milk and to the receptor (hr), and
2-45
-------
Xd = the radiological decay constant (hr'1) .
The radionuclide concentration in meat from atmospheric
deposition depends, as with milk, on the amount of feed consumed
and its level of contamination. The radionuclide concentration
in meat is estimated using
Cf = FŁCfQf«Exp(-Xdtg)
(2-52)
where:
Cf = the nuclide concentration in animal flesh (pCi/kg),
Ff = the fraction of the animal's daily intake of a given
radionuclide which appears in each kilogram of flesh
(d/kg),
Cf = the concentration of radionuclide in the animal's feed
(pCi/kg),
Qf = the amount of feed consumed by the animal per day
(kg/d), and
ts = the average time from slaughter to consumption (hr).
Concentrations of radionuclides in foodstuffs that result
from spray irrigation with contaminated water are estimated using
essentially the same equations as for atmospheric deposition with
the following differences: the concentration in vegetation, Cv,
is estimated using Equation 2-48, but a different value of the
retention fraction, R, is used. For irrigation, the second term
of Equation 2-48 is modified by a factor of f:/ the fraction of
the year during which irrigation occurs, and the te in the
exponent becomes tw, equivalent to fx in hours. For irrigation
calculations, the deposition rate, d, in Equation 2-48 becomes
the irrigation rate, Ir, expressed as:
Ir = Cw Wx (2-53)
2-46
-------
where
Ir = radionuclide application rate (pCi/m2 hr) ,
Cw = radionuclide concentration in irrigation water (pCi/1),
and
Wz = irrigation rate (l/m2-hr) .
The concentration in water, Cw/ is an average of well and stream
water weighted by the respective amounts of each that are used.
Another modification introduced for irrigation calculations
is related to the radionuclide concentration in milk and meat
where the animal's intake of water was added to Equation 2-51 and
2-52, respectively. This becomes:
Cm = Fm(CfQf + CwQJExp(-AdtŁ) (2-54)
CF = Ff(CfQf + CwQw)Exp(-Adta) (2-55)
where:
Qw = the amount of water consumed by the animal each day
(1/d)
Once radionuclide concentrations in all the various
foodstuffs are calculated, the annual ingestion rate for each
radionuclide is estimated by
Qing = Qv + Qnuik + Qmeat +
(2-56)
where the variables represent individual annual intakes of a
given radionuclide via total ingestion, Qing, and ingestion of
vegetation, Qv, milk, Qmiik, meat, Qmeat» and drinking water, QM1
respectively, in pCi/yr. The annual intakes via each type of
food, Qv for instance, are calculated as
2-47
-------
Qv = (Cvl + CVA)UV (2-57)
where
Qv = annual radionuclide intake from vegetation (pCi/yr),
Cvl = radionuclide concentration in vegetation from
irrigation (pCi/kg),
CvA = radionuclide concentration in vegetation from
atmospheric deposition (pCi/kg), and
Uv = individual annual intake of vegetation (kg/yr).
To satisfy the input requirements for DOSTAB, the annual
individual intakes are multiplied by the size of the population
to calculate the collective ingestion annually.
As mentioned earlier, Equations 2-47 through 2-55 do not
apply directly to calculations of concentrations of H-3 or C-14
in foodstuffs. For application of tritium in irrigation water,
it is assumed that the transfer factor for the concentration in
all vegetation, Cv/ from the tritium concentration in the
irrigation water is 1 when the units of Cv and Cw are in pCi/kg
and pCi/1, respectively, then
Cv = 1-CW (2-58)
where Cv and Cw are in pCi/kg and pCi/1, respectively. In the
same manner, the concentration of H-3 in animal's feed, Cf, is
also equal to Cw. Then, from Equations 2-54 and 2-55, the
concentration of tritium in animal's milk and meat can be written
as:
Cm = FmCw(QŁ + QJ (2-59)
CP = FfCw(Qf + QJ (2-60)
where
2-48
-------
Cm = concentration of tritium in milk (pCi/1),
Fm = fraction of the animal's daily intake of H-3 that
appears in each liter of milk (days/1),
Cw = H-3 concentration in animal drinking water (pCi/1),
Qf = animal's daily intake of forage (kg/d),
Qw = cow's daily intake of water (1/d),
CF = concentration of tritium in animal meat (pCi/kg), and
Ff = fraction of the animal's daily intake of H-3 that
appears in each kg of meat (d/kg).
The exponential term is neglected due to the relatively long
half-life of tritium as compared to transit times in the food
chain.
The root uptake of C-14 from irrigation water is considered
negligible and, therefore, has been set equal to zero.
For vegetation contaminated by atmospheric deposition of
tritium, H-3 concentrations are calculated by
Cv = (CA/h)(0.75)(0.5)(1E15) (2-61)
where
Cv = tritium concentration in vegetation (pCi/kg),
CA = concentration of H-3 in air (Ci/m3) ,
h = absolute humidity of the atmosphere (g/m3) ,
0.75 = ratio of H-3 concentration in plant water to that
in atmospheric water,
0.5 = ratio of H-3 concentration in atmospheric water to
total H-3 concentration in atmosphere, and
1E15 = (1E12 pCi/Ci)x(1000 g/kg).
2-49
-------
The mean ground-level air concentration of H-3, CA, is calculated
using the equations in Section 2.2.2.
For C-14, the concentration in vegetation is calculated
assuming that the ratio of C-14 to be the natural carbon in
vegetation is the same as that ratio in the surrounding
atmosphere. The concentration of C-14 is given by
Cv = (CA/0.16)(0.11)(1E15) (2-62)
where
Cv = C-14 concentration in vegetation (pCi/kg),
CA = mean ground-level concentration of C-14 in air (Ci/m3) ,
also calculated from equations given in Section 2.1.2
r = ratio of the total release time of C-14 to the total
annual time during which photosynthesis occurs, r s 1,
0.11 = fraction of the plant mass that is natural carbon,
0.16 = concentration of natural carbon in the atmosphere
(g/m3) , and
1E15 = (1E12 pCi/Ci)x(1000 g/kg).
2.2.4 DOSTAB Calculations
In Equations 2-49 through 2-59 it was shown how calculations
are made of radionuclide concentrations in air, ground
concentration, and annual ingestion and inhalation rates. These
concentrations and rates are utilized by the DOSTAB portion of
the PRESTO-EPA-CPG code to generate tables of radiological dose
and resulting health effects. This section describes the
mathematical calculations made within DOSTAB. For the most part,
the equations and text have been taken from the DARTAB
documentation report (Be81), Section 2.3 entitled, "General
Equations."
2-50
-------
Radiological Doses
The annual dose committed to an individual at location k for
the 1th organ, ith nuclide, and jth exposure pathway is given by
DlDl(k) = (KDEi:|(k)»DF13l)/P(k)
(2-63)
where K., contains any numerical factors introduced by the units
of E1;J (k) , the exposure to the ith radionuclide in the jth
pathway, DF1Dl is the dose rate factor of the ith radionuclide,
the jth pathway and the 1th organ, and P(k) is the exposed
population at location k. Note that all E1D and DF1:)1 for various
nuclides (index i) and organs (index 1) have consistent units.
DOSTAB performs three calculations and tabulations for dose
rate and dose: (1) dose rate to an individual at a selected
location, (2) dose rate to a mean or average individual, and (3)
collective population dose rate. Table 2-2 lists units of DF1;)1
and E1D for each of the four pathways for selected individual
dose calculations. Dose rates, D1Dl, are in mrad/yr.
Mean individual dose rates are calculated using
= [lP(k)«D1Dl(k)/]TP(k)]
k k
(2-64)
Table 2-2 Unit of Exposure and Dose Rate Factors used in
DOSTAB
pathway
Ingest ion
Inhalation
Unit of Factor
=xj
(Person-pCi) /yr
(Person-pCi) /yr
DF13l
(mrad/yr) / (pCi/yr)
(mrad/yr) / (pCi/yr)
2-51
-------
Air immersion
Ground Exposure
(Person-pCi) /yr
(Person-pCi) /yr
(mrad/yr) / (pCi/yr)
(mrad/yr)
Note that in PRESTO-EPA-CPG the impacted population is considered
to reside at only one location (k = 1). Hence, calculations of
mean individual dose rate are numerically equivalent to the sum
of pathway doses for the selected individual dose rate. The
collective dose rate for the exposed population is the product of
Dijl and the number of persons exposed. Units of the collective
dose rate are person rad/yr.
The above dose rates may be expressed in a number of
different combinations. The doses can be summed directly over
pathways:
Du(k) = JX3l(k) (2-65)
3
or over all nuclides:
DDl(k) = Ł D1Dl(k) (2-66)
i
The total dose to the 1th organ at location k, D(k), is then
D1Dl(k) (2-67)
The dose equivalent (mrem) , H, for the 1th organ is given as
= QF(low.leC)D1(low.LET) +
D 1
(2-68)
where QF denotes the relative biological effect factor. The
factor is defined for each organ or health effect.
2-52
-------
To combine dose rates to different organs, a weighted sum is
used
Di:(k) = Ł W!D13l(k) (2-69)
where Wx are weighting factors for the various organ doses
supplied by the user where
= 1 (2-70)
Weighting factors developed by EPA for the various organs were
used as input into DOSTAB. The International Commission on
Radiological Protection (ICRP79) has proposed a similar approach
to adding organ doses .
2.2.5 Daughter Nuclide In-Growth Effect Calculation
The earlier version of the PRESTO model calculates the
committed effective doses resulting from parent nuclides and
ignores the doses contributed by their daughter nuclides. This
simplification may, in some cases, incur significant error in the
results of the assessment. A correction factor for daughter
nuclide in-growth effects is introduced to incorporate the
daughter nuclide in-growth effects into the results of dose
calculation and to improve the accuracy of the analysis. This
correction factor is then used to correct the result of dose
calculations described later in this section.
In order to simplify the analysis, a crude assumption is
imposed. The analysis assumes that the sorption characteristics
of the parent and daughter nuclides are identical throughout the
processes of leaching and groundwater transport. This assumption
seems to be unrealistic but the error incurred from this crude
assumption is not excessive and, in most cases, on the
conservative side. Furthermore, this assumption is widely
adopted in existing screening type of risk assessment models.
When the above assumption is imposed, the mathematical
2-53
-------
relationships for nuclide transport can be greatly simplified.
This is because a moving control volume concept with no flux
transport across its boundary can be applied. As a result, the
ratio of the activities between daughter and parent nuclides
within a designated control volume at any given time can be
calculated from the Bateman equation (Ev 55). This ratio is then
used to calculate the correction factor to account for the
daughter nuclide in-growth effects.
Decay Chains
For the purpose of assessing the health impacts from the
disposal of low-level radioactive waste and NORM waste, the
following decay chains were selected for incorporation into the
PRESTO-EPA model:
1. Am-243 Pu-239 • U-235
2. Cm-244 Pu-240 > U-236 • Th-232
3. Pu-238 U-234 Th-230 • Ra-226 Pb-210
4. Pu-241 • Am-241 Np-237
5. Pu-242 • U-238 • U-234 • Th-230 > Ra-226 > Pb-210
The decay chains depicted above assume those progeny not shown in
these chains can be ignored for the analysis.
Altogether, 13 parent nuclides are considered and built into
the model for calculating their progeny effects. They are Am-
243, Pu-239, Cm-244, Pu-240, U-236, Pu-238, U-234, Th-230, Ra-
226, Pu-241, Am-241, Pu-242, and U-238. The model evaluates the
progeny in-growth effects up to the fourth member of the chains
shown above. The effects contributed from the fifth and higher
members are neglected.
Mathematical Formulation
The derivation of the correction factors for the second,
third, and fourth decay chain members as derived by Hung (Hu94)
are included in Appendix C. The results are summarized as
follows:
2-54
-------
4-Member" Decay Chain
The correction factors, respectively, for the parent, second,
third, and fourth decay products are derived to be:
,
= i
(2-71)
CF,
n, = x.—2-
2 2 CF,
EXP(-(X -
(2-72)
j) t)
(2-73)
X2x3x4
CF
(X.-X,)
+ EXP(-(X2-\)t)
,-X,) + (X.-X,) (X,-X,) (X,-
EXP(-(X3-X.) t) BJfP(-(X -X.) t)
* 1
-X,) (X,-X,J (X,-X,) (X,-XJ (X,-X4) (X,-XJ
(2-74)
In above equations, ri denotes the committed effective dose
2-55
-------
correction factor, A is the radionuclide decay constant, CF is
the dose conversion factor, and subscripts 1, 2, 3, and 4 denote
parent, second, third, and fourth decay chain products,
respectively.
The combined daughter-nuclide dose correction factor, nc, is
expressed by the sum of the impacts from all 4 members,
nc = 1 + n2 + n3 + i\t (2-75)
For simplicity, the subscript c is dropped throughout the rest of
this document.
3- and 2-Member Decay Chains
The combined daughter-nuclide dose correction factors for 3-
and 2-member decay chains is reduced from the correction factor
developed for the 4-member decay chain shown above. The results
of this reduction are expressed in the following equations:
ri = 1 + r|2 + n3 (2-76)
for the 3-member decay chain, and
n = 1 + n2 (2-77)
for the 2-member decay chain.
Dose Calculation
When the daughter nuclide in-growth effect correction factor
is calculated the combined parent and daughter nuclides
equivalent dose is calculated by:
Dc = Dp x n (2-78)
Where Dc denotes the combined effective dose for daughter and
parent nuclides, and Dp is the calculated parent nuclide
equivalent dose.
2.2.6 Basement Dose to Resident
2-56
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The DOSTAB subroutine of the PRESTO-EPA-CPG model contains
algorithms to compute the dose rate per unit radionuclide surface
concentration to an individual standing on a contaminated,
infinite plane. This section describes the calculation of a
factor which is used to convert the input to this infinite plane
computation so that the calculation computes a value appropriate
for an individual spending part of his time in a basement. In
this calculation it is assumed that the basement actually extends
into and is surrounded by the trench contents. Furthermore, it
is assumed that most of the individual's time is spent at the
center of the basement, that the basement radius is three meters,
and that the radiation attenuation coefficient of the trench may
be approximated by that of soil, with attenuation coefficients
taken from literature published by the British Standard Institute
(BSI66). The elapsed time between closure of the waste disposal
area and construction of the basement is an input parameter for
the model.
A conversion factor F is defined which is used to convert
the radionuclide concentration in the trench surrounding the
basement to a value appropriate for an input parameter to the
infinite plane calculation. Provided the basement is
continuously occupied, this conversion factor is defined by the
equation
Db/N
F = (2-79)
DP/A
where
Db/N = dose rate in basement per unit of radionuclide
concentration in trench (mrad/yr)/(pCi/m )
DP/A = infinite plane dose rate per unit of surface
concentration on ground (mrad/yr)/(pCi/m2)
In Equation 2-79, A represents the radionuclide concentration per
unit surface area on the infinite plane and N represents the
radionuclide concentration per unit volume in the trench
material. If the value of the factor F is known, the
radionuclide dose rate to an individual within the basement may
be found by using a modified form of the above equation
2-57
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Db = (Dp/A) FN (mrad/yr) (2-80)
The basement whole-body gamma dose rate per unit of
radionuclide concentration at a distance 1 meter above the
basement floor is found by integrating the radiation flux from
each volume element of the trench material over the trench volume
v:
(Db/NC) = [ {B(/*TrT)/r2 Exp{-(/zara + /iTrT) }dv (2-81)
where
C = units transformation constant [(mrad/yr)/(pCi/m2) ]
B(/iTrT) = build up factor, using formulas by Eisenhauer and
Simmons for energies up to 200 kev and Taylor's formula
for energies above 200 kev. Coefficients for the
Eisenhauer and Simmons equation are taken from
Eisenhauer and Simmons (Ei75) and for Taylor's formula
are taken from Morgan and Turner (Mor67)
r = distance from point of interest to element of volume of
the trench dv (m)
/xa = linear attenuation coefficient of air (m'1)
/iT = linear attenuation coefficient of trench (m'1)
ra = distance in air from point of interest to element of
volume dv (m)
rT = distance in trench from point of interest to element of
volume dv (m)
v = trench volume (m3)
The basement may be considered circular, so that Equation
2-73 becomes:
2-58
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(Db/NC) = f {B(MTrT)/r2}Exp{-(/iara + /xTrT) }dv
J v(floor)
+ f {B(fiTrT)/r* Exp{-(|iara + /zTrT) }dv
Jv(wall)
R+D H+d
/I
2n
:f /* {r'B(/iTrT)/r2 Exp{-(/iara + /iTrT) }dZdr
Jo J H
R+d H+d
2n {r'B(/xTrT)/r2} Exp{-(^ara + /iTrT)}dZr'
f I
J R J C
(2-82)
where
R = basement radius (m)
h = distance of point of interest from floor (h = l m)
H = basement height (m)
d = cut-off thickness of trench, chosen to be 10 mean free
paths (or !0//iT)
The first integrand refers to the section of the trench
immediately below the basement floor, while the second integrand
refers to the trench material outside the walls of the basement.
For this calculation, the basement is assumed circular, and a
two-dimensional Simpson's rule method (McC64) is used to
numerically evaluate the integral.
Equation 2-74 has been evaluated to determine values of the
ratio Db/NC, and we have found that as the assumed basement
radius varies from 3 to 6 m, the completed value of Db/NC changes
by only 30 percent (being greater for the smaller basement
2-59
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radius) for radiation energies ranging from 20 keV through 10
MeV. Tabulated values of the linear attenuation coefficient for
air (Ko79) and for earth are used (BSI66).
The dose rate at a height of 1 meter per unit surface
concentration from an infinite plane is given by the equation
Dp/AC = | (l/r2) Exp(-/iar) ds
J s
= 2n| (l/r) Exp(-/xar) dr
= 2nl (2-83)
where
C = units transformations constant (mrad/yr)/(pCi/m2)
•)Exp(-/xar)dr (dimensionless)
1 = A(1/r
(Jia = linear attenuation coefficient of air (m-1)
z = height of point of interest (z = 1 m)
In this transformation, the incremental area element ds is
2nrdr, where r is the radius projection onto the plane; and since
R2 = r2 + l, it follows that rdr=RdR. The value of the integral,
1, in this equation, may be computed numerically using a
polynomial approximation (Gau64) for values of /xa corresponding
to different values of gamma energies. The results of these
calculations are summarized in Table 2-3.
The value of the ratio F as defined by Equation 2-71 may be
obtained for a given energy by dividing the results of the
2-60
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Table 2-3 Results of Basement and Infinite
Plane Unit Dose Rate Computations
Energy
MeV
0.05
0.10
0.20
0.50
1.00
2.00
4.00
6.00
8.00
10.00
F(m)
0.015
0.045
0.061
0.087
0.087
0.088
0.092
0.098
0.099
0.101
basement calculation by the results of the infinite plane
calculation. Values of this ratio for energies between 10 keV
and 10 MeV are given for a basement radius of 3.0 m in Table 2-3.
A very conservative average value of F may be chosen to be 0.1 m.
If the basement is occupied one-third of each day, then the
radionuclide concentration within the trench is one-third.
Therefore, the basement exposure dose rate in the infinite plane
dose rate calculation of the DOSTAB subroutine is found by
multiplying the average radionuclide concentration by the volume
within the trench during the basement occupancy period by the
volume to the surface correction term F and the fraction of time
the basement is assumed to be occupied. Thus, the value of A is
augmented by the quantity 0.033N to yield a value that
corresponds to the plane dose plus the basement dose. In the
computer code, the time at which the basement is constructed is a
user input parameter, and the average radionuclide concentration
by volume for that period between basement construction until the
end of the simulation period is computed by the code. This
incremental concentration is added to the computed average
surface concentration if the code user has elected to include the
basement exposure mode.
2-61
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2.3 DEVELOPMENT OF PRESTO-EPA-CPG CODE
2.3.1 Model Structure
The mainframe version of PRESTO-EPA-CPG code is written in
FORTRAN VII for an IBM 3081 and requires 85OK bytes of memory.
It is designed to process up to 40 nuclides for a maximum of
1,000 years. The program should be easily transferrable to other
IBM installations. It has run correctly on another non-EPA IBM
computer system after installation directly from tape. Non-IBM
users may have to modify the job control language (JCL), the
NAMELIST inputs and other program segments where character
manipulations are used.
The PRESTO-EPA-CPG code is structured in a modular form to
permit simple upgrading or replacement of given submodels without
rewriting the entire code. The subroutine structure of the code
is shown in Figure 2-5.
There are three classes of submodels: unit response,
scheduled event, and bookkeeping submodels. Unit response
submodels simulate processes such as rainwater infiltration
through the intact portion of the trench cap, erosion of soil
overburden from the trench cover, and atmospheric transport.
Such submodels are usually accessed only once during a model run
and generate parameters and rates used elsewhere in the
simulation.
Scheduled event submodels estimate events such as the time
of trench cap failure, while bookkeeping submodels determine the
water balance in the trench and radionuclide concentrations in
the trench outflow and the aquifer. Output from the bookkeeping
submodels is iterated annually over the simulation period. Risk
evaluation bookkeeping submodels accept the cumulative or mean
output from the transport portion of the code and generate doses
based on a life-table approach.
2.3.2 Subroutine Description
An alphabetical listing and description of the subroutines
and main program found in PRESTO-EPA-CPG is given below.
MAIN - This routine is the main calling program of PRESTO-
2-62
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EPA-CPG and defines the most commonly used variables of the code,
specifies dimension and common areas, and initializes variables
and input control parameters. The input and output subroutines,
SOURCE and OUT, are called directly by MAIN (Figure 2-5), as are
the unit response model subroutines AIRTRM, and ERORF. MAIN also
calculates: the vertical water velocity; retardation factors;
vertical, horizontal and total transit times in groundwater (the
transfers from trench to vertical soil column to aquifer in
Figure 2-1); and the basement exposure correction factor (Section
2.2.2). The decay dispersion correction factor, DDETA (Hu81), is
calculated for each radionuclide in MAIN (factor DDETA adjusts
the activity output of the aquifer for the combined interactions
of longitudinal dispersion and radioactive decay.) QUANC8, which
is based on an eight panel Newton-Cotes rule, performs the
integration necessary to obtain the correction factor.
MAIN calls the bookkeeping subroutines to calculate
quantities associated with trench water balance, trench cap
status, changes in land use and basement occupancy. Other
subroutines called by MAIN compute the amount of leaching from
trench, transport of soluble surface components, atmospheric
concentrations, and well concentrations. In addition, aquifer
volume, hypothetical radionuclide withdrawal from well, and
material balances for water in the aquifer are calculated in
MAIN.
Risk evaluation submodels called from MAIN account for
radionuclide concentrations in food due to atmospheric deposition
and water irrigation, and radionuclide intake by man. These
subroutines are IRRIG, FOOD, HUMEX, CV, COV, IRRIGA, FOODA,
HUMEXA, CVA, AND COVA. Finally DARTAB (equivalent to DOSTAB used
in PC version), which creates tables of predicted health effects
from radioactive effluent is called from MAIN.
The annual simulation loop and the radionuclide loop are
executed a selected number of times. During a model run, MAIN
may access any or all of the subroutines or functions which are
listed below in alphabetical order.
2-63
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2-64
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Figure 2-5 PRESTO-EPA-CPG Subroutine Structure
AIRTRM - This subroutine is the main calling program for the
atmospheric transport submodel. AIRTRM calculates sector-
averaged (22.5 degree) atmospheric exposures normalized to the
source strength. AIRTRM and all its supporting subroutines are
adaptations of the interactive Gaussian plume atmospheric model,
DWNWND (FiSOa). AIRTRM also calculates the deposition rate onto
surfaces per unit source strength. To make these calculations,
AIRTRM accesses four other subroutines, SIGMAZ, DPLT, YLAG, and
SIMPUN, and utilizes a number of user-input parameters including
source height, lid height, stability class, type of stability
class formulation, Hosker roughness parameter, wind velocity,
deposition velocity, gravitational fall velocity, and source to
receptor distance. The normalized atmospheric exposures are
returned to the main program and are used in later dose and risk
calculations.
CAP - This function calculates and returns to both MAIN and
TRENCH the fraction of the trench cap that has failed. Cap
failure may be either partial or total. Total failure may be
caused by erosion of all overburden as calculated by ERORF.
Partial failure indicates that a portion of the cap has been
completely removed; the remainder of the cap is still subject to
erosion. Partial failure may be caused by user input of the end
points of a linear function to selectively remove all overburden
from a fraction of the trench.
COV. COVA - These functions are called by subroutine IRRIG
and IRRIGA to calculate radionuclide concentrations in
vegetables, milk, and meat that may be contaminated by
irrigation. The radionuclide concentrations in food depend on
such quantities as the agricultural productivity of vegetation,
the period of irrigation annually, the storage delay period
between harvest and use for pasture grass, feed, leafy vegetables
and produce, and the radionuclide decay constant.
CV. CVA - These functions are utilized by subroutines FOOD
and FOODA to calculate radionuclide concentrations in pasture
grass and stored feed consumed by animals, and in leafy
vegetables and produce consumed by humans. CV is essentially the
same as function COV, except that CV is used for atmospherically
2-65
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deposited radionuclides and COV accounts for radionuclides
deposited by spray irrigation. Pertinent input data include
agricultural productivity, fraction of the year vegetation is
exposed to depositing radionuclides, and the delay time between
harvest and consumption for stored feed, pasture grass, leafy
vegetables, and produce.
DARTAB/DOSTAB - The original DARTAB code is a self-contained
program which combines radionuclide environmental exposure data
with dosimetric and health effects data to create tables of
predicted impacts of radioactive effluent. DARTAB has 11
subroutines and contains over 3000 FORTRAN source statements.
DARTAB subroutines are RDSTOR, FACOUT, CHLOC, PREPDR, PREPRF,
PREPHR, MULT, DRTAB, ORGFAC, SUMMRY, and SUMMR2. These are not
discussed specifically in this report. For information on the
original DARTAB consult the document describing the code (Be81).
DARTAB has been modified for PRESTO-EPA-CPG so that the program
is treated as a subroutine. Environmental exposure data are now
passed in COMMON from MAIN to DARTAB's subroutines.
DARTAB uses dosimetric and health effects data from the
methodologies of RADRISK (Du80). RADRISK uses a life-table model
to calculate the human health risk to a cohort of 100,000 people
from a constant input of 1 pCi/yr (0.037 Bq/yr) via ingestion and
inhalation over a lifetime (70.7 yr) .
These intake conditions are approximated in PRESTO-EPA-CPG
by calculating an average intake over the span of the assessment
of each type of intake. RADRISK data files are accessed directly
by DARTAB.
The PC version of the PRESTO-EPA-CPG model simplifies the
submodel by accessing the dose factors from a precalculated dose
factor table instead of reading them out from the complex RADRISK
file. The modified submodel is designated as DOSTAB.
DAUTER - The subroutine DAUTER is called the MAIN program to
calculate the daughter nuclide in-growth effect correction factor
for simulation time of interest. The submodel is called each
time when the committed effective dose calculation is performed.
DPLT - The subroutine DPLT is called by AIRTRM and computes
a correction factor for plume depletion. To make this
calculation, DPLT calls subroutines SIGMAZ and SIMPUN.
2-66
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ERORF - This subroutine uses the universal soil loss
equation, USLE, developed by the U.S. Department of Agriculture
(USDA61) to determine sediment loading for rain-driven surface
erosion. Estimation methods and tabulations for factors used in
USLE have been organized and published by McEloy et. al. (McE76).
The code user inputs all six of these factor values. The
calculated erosion rate is returned to MAIN where it is converted
to an annual erosion rate in meters. This erosion rate is
utilized by MAIN to determine the thickness of the cap.
FCN - This function subprogram returns to QUANC8 a
functional evaluation of the integral used in calculation of the
aquifer decay-dispersion correction factor. The routine is
written in double precision to facilitate interaction with the
double precision routine QUANC8.
FOOD. FOODA - Subroutine FOOD is called only once per
simulation and calculates the average concentration of each
radionuclide in foods contaminated by atmospheric deposition and
root uptake. The deposition input to FOOD is calculated in
subroutine AIRTRM. The equations and internal parameters used by
FOOD are those in AIRDOS-EPA (Moo79). Output from FOOD is used
by the subroutine HUMEX to calculate the human exposure via
ingestion of these contaminated foodstuffs. Subroutine FOODA is
called from MAIN each simulation year.
HUMEX. HUMEXA - Subroutine HUMEX accepts user input and
receives averaged data from subroutines AIRTRM, FOOD, IRRIG, and
VERHOR to calculate the average annual human exposures via
ingestion and inhalation. Output from HUMEX supplies the input
to the DARTAB subroutines for calculations of risk and dose and
tabulation of health results. Subroutine HUMEXA is called from
MAIN each simulation year.
INFIL - The subroutine INFIL is based on a model by Hung
(Hu83b) and calculates annual infiltration through the trench
cap. INFIL calls subroutine SOIL and ROUT. Inputs to INFIL
include hourly precipitation, daily temperature, and various
trench cap characteristics.
IRRIG. IRRIGA - Foods may be irrigated with contaminated
water from either surface or groundwater sources. Input to
IRRIG, which is called only once per simulation, includes
the time-averaged radionuclide concentrations in well
2-67
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or surface water calculated by VERHOR or subroutine SURSOL,
respectively. IRRIG calls the function COV and uses the
equations in AIRDOS-EPA (Moo79, FiSOb) to calculate the time-
averaged concentration of each radionuclide from direct
deposition by irrigation and subsequent root uptake in foodcrops.
Subroutine IRRIGA is called from MAIN each simulation year.
LEACH - Subroutine LEACH calculates the amount of each
radionuclide from the homogeneous trench contents that leaves the
trench each year. Losses may be via transport through the trench
bottom or by overflow from the trench. There are five
independent user-specified methods that may be used to calculate
these amounts: the option is chosen by specifying a value from
one through five for parameter LEAOPT. Table 2-2 lists the
calculational methods corresponding to values of LEAOPT. The
total contact options, 1 and 3, assume that all of the trench
contents have been in contact with water during the previous
year. The immersed fraction options, 2 and 4, assume that the
wetted fraction of the waste equals the ratio of maximum water
level to the trench depth. The distribution coefficient options,
1 and 2, utilize a Kd approach to calculate the radionuclide
concentrations released from the wastes to the water, while
options 3 and 4 use a solubility estimate rather than Kd. If the
user selects LEAOPT = 5, then a user-specified fraction of the
total radionuclide concentration in the waste is lost through the
trench bottom annually. Output from LEACH is the activity
leaving the trench annually for each radionuclide through the
bottom of the trench and by overflowing.
OUT - This subroutine produces annual summaries for the
trench cap status, trench water balance, amount of water leaving
trench, and radionuclide contents in trench water, trench
overflow water, aquifer, well water, and on the ground surface.
The user may choose to print these summaries for every year or
less frequently by specifying the appropriate values of IPRTI,
IPRT2, and IDELT in the input data file.
OUANC8 - This subprogram employs a Newton-Cotes 8-panel
quadrature formula (For77). The integral to be evaluated is
specified by the function FCN.
ROUT - This subroutine is called by INFIL. This subroutine
calculates the hydrological parameters for the overland flow
known as flow routing. These parameters are used to calculate
2-68
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the rate of overland flow and the rate of infiltration which
serve as the driving forces for the risk assessment.
SIGMAZ - This subroutine is called by both AIRTRM and DPLT
to compute the vertical atmospheric dispersion parameters.
Depending on the choice of parameterization specified in the
input data set, SIGMAZ will calculate the dispersion parameters
by one of eight schemes. Necessary input data include the
downwind distance, stability class, Hosker roughness parameter,
and lid height. Other data necessary for Lagrangian
interpolations (by function YLAG) are built-in internally in
SIZMAZ.
SIMPUN - This subroutine, originally written by Barish
(Bar70), uses Simpson's rule to integrate along the ground level
centerline of the atmospheric plume to compute the depletion
fraction. All input to SIMPUN is supplied by DPLT, the
subroutine that calls SIMPUN and to which the results are
returned.
SOIL - This subroutine is called by ROUT and is used to
calculate the moisture contents in the soil cover. The soil
moisture contents are used to calculate the rate of infiltration
in the ROUT subroutine.
SOURCE - Subroutine SOURCE reads the input required to
initialize and quantify transport parameters, except those
required for subroutine INFIL. Data concerning program control,
climatic description, trench description, aquifer description,
atmospheric description, site-surface description, and
radionuclide description are read in by SOURCE. SOURCE also
prints out these data before any calculated results are printed
out.
SURSOL - Subroutine SURSOL computes the amount of soluble
radionuclide that enters the stream annually. Input variables to
SURSOL include the average depth of active exchange in the soil,
the average downslope distance to the stream, the cross slope
extent of the spillage, the average annual infiltration, the bulk
density of soil, the amount of spillage, and the surface soil
distribution coefficients. Variables printed out from SURSOL
include the amounts of radionuclide going to the stream and the
deep soil layers and the radionuclide concentration in the
interstitial water of the contaminated surface region.
2-69
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SUSPND - This subroutine calculates the above trench
atmospheric source term from the ground surface by two pathways,
a wind driven resuspension and a resuspension due to mechanical
disturbance. Input variables include the current year of
simulation, the spatial area of the contaminated surface, the
radionuclide concentration on the ground surface, the beginning
and ending years of mechanical disturbances, the resuspension
rate, and the wind velocity. SUSPND assumes that all
radionuclides to be resuspended are deposited on the soil surface
at a simulation time zero. The resuspension factor calculated
uses the empirical equation of Anspaugh et al. (An75).
The atmospheric source term is returned to MAIN and is used
along with X/Q to calculate the air concentration of each
radionuclide available for deposition onto foodstuffs and for
inhalation by the general population. The value of X/Q is
calculated by AIRTRM.
TRENCH - This subroutine determines the trench water
balance. Input variables include trench dimensions, porosity and
permeability of trench contents, trench water volume from the
previous year, length of the saturated zone, and annual
precipitation and infiltration. Output from TRENCH includes the
maximum depth of water in the trench, the volume of water in the
trench, volume of water overflowing the trench, and water volume
lost from the bottom of the trench.
The amount of water which overflows the trench is calculated
by comparing the maximum water depth to the trench depth and
overflowing any amount greater than the trench volume. The
variables VOLO, VOLB, OLDWAT, and DMAX that quantify overflow,
bottom loss, water level during previous year, and maximum water
depth in trench, respectively, are used by the subroutine LEACH,
discussed previously.
VERHOR - This subroutine calculates the amount of each
radionuclide, that reaches the irrigation/drinking water well in
a given year. Variables evaluated elsewhere in the code and
input to VERHOR include the current year of the simulation,
transit time from the trench to the well, the volume of water
leaving the trench bottom, the amount of each radionuclide
leaving the bottom of the trench, the amount of radionuclide
reaching the aquifer from the contaminated surface region, and
the radioactive decay constant.
2-70
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YLAG - This function performs a Langragian interpolation as
part of the atmospheric transport calculations. The original
program was written by Brooks and Long (Br70) and adapted for use
here. All input data are supplied by subroutine SIGMAZ.
XPRESS - This subroutine computes and stores exponential
decay factors to be used repetitively in the nuclide loops.
XPRESS saves a substantial amount of computing time.
2.3.3 PC Version of PRESTO-EPA-CPG Model
The mainframe version of the model employed the DARTAB
subroutine, which prohibited executing the model in a personal
computer because it was designed to read-in the necessary input
data from the RADRISK file. Therefore, to execute the model in a
personal computer, it is necessary to modify the model design to
reduce the core memory requirement and to improve the process
efficiency.
The major modifications of the model include the replacement
of the DARTAB subroutine with the DOSTAB subroutine, addition of
HUNG function, elimination of the QUANC8 function, and adjustment
of I/O statements [Ro87].
The replacement of the DARTAB subroutine with DOSTAB has
reduced considerably the core memory requirement. To calculate
the dose equivalents resulting from human exposures, the DOSTAB
subroutine reads a set of dose equivalent conversion factors from
the dosimetric input file, which were precalculated from the
RADRISK file using the same methodology as used in the original
DARTAB subroutine. The results of the calculation are printed
out in much the same format used in the mainframe version of the
model.
The elimination of the QUANC8 function, a function for
integrating an algebraic function having an infinite limit,
prevents the tedious numerical integration of Hung's correction
factor [Hu80]. The modified model employs an analytical solution
derived by Hung [Hu86] which is calculated in HUNG function.
This modification resulted in some savings in the process time.
In addition, the model calculates and prints out the dose
equivalent incurred through the drinking water pathway as a
component of the ingestion pathway. The PC version of PRESTO-
2-71
-------
EPA-CPG is called PRESTO-EPA-CPG throughout the rest of this
documentation hereafter.
2.4 INPUT FILE REQUIREMENTS
There are three input files required for the execution of
PRESTO-EPA-CPG. They are: (1) the environmental and nuclide
specific input file; (2) the INFIL subroutine input file, and (3)
the dosimetric input file. Details of the input files are
presented in the following sections. The requirements described
in this section apply to the PC version of the model.
2.4.1 Environmental and Nuclide-Specific Input File
This input file is used to supply the physical and
hydrogeological characteristics of the disposal site, the
meteorological data for atmospheric dispersion and deposition,
the data for the biological pathways, and the radionuclide
characteristics and inventories.
The data set also contains parameters describing the site
characteristics, the disposal technology, the human exposure
characteristics, and some specific parameters characterizing the
site and exposure scenarios. For simplification, this input file
is referred to as the main input file throughout this
documentat ion.
2.4.2 INFIL Subroutine Input File
The INFIL subroutine input file is used to calculate
rainwater infiltrating through the trench cap into the waste
trench. It is divided into two categories, trench cap
characteristics and local hydrological and meteorological data,
2.4.3 Dosimetric Input File
This file contains the dose conversion factors for each
radionuclide. It is used to calculate the committed annual
effective dose for each organ and the whole body through each
exposure pathway.
2-72
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These conversion factors are independent of disposal site
and disposal method; therefore, this file is incorporated into
the program and requires no changes from the user under normal
application.
The format for the environmental and nuclide-specific, INFIL
subroutine, and dosimetric input files are listed in Appendix D,
Tables D-l, D-2, and D-3, respectively.
The definition and format of the input files for the
environmental and nuclide-specific input file and INFIL
subroutine input file are basically identical to that for the
mainframe version of the model, except for 3 cards used in the
environmental and nuclide specific input file. Modifications on
these cards are described as follows:
1. Card 4: A variable IORG is added to the end of the
original card (see Appendix D for the
definition of IORG).
2. Card 19: The variable name RR is renamed RMECH, but
the definition of the variable remains the
same (see Appendix B for definitions of RR
and RMECH).
3. Card 20: Two variables, RR and FTRR, are added in
front of the two original variables, IT and
IS (see Appendix D for definitions of RR,
FTRR, IT, and IS).
2.5 OUTPUT FILE DESCRIPTION
The output of PRESTO-EPA-CPG is designed to be self-
explanatory and contains descriptive comments, definitions, and
intermediate and final tabulations. It is assumed that the
output may be analyzed by users unfamiliar with PRESTO-EPA-CPG
structure. The PRESTO-EPA-CPG output is organized into nine
sections, each described below.
2.5.1 Replication of Input Data
2-73
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The first section of the PRESTO-EPA-CPG output is
replication of the user supplied input data files (1) and (2) as
read in. This provides the user with a record of the input data
set used for later result identification and analysis. PRESTO-
EPA-CPG also organizes this input data to allow for easy
interpretation. A summary of the input data files (1) and (2) is
printed according to data type and transport sub-system. These
descriptive summaries are output in sentence format to improve
ease of review.
2.5.2 Radinuclide Summary Tables
A set of tables under the heading "Nuclide Information" next
summarizes the radionuclide data used for the transport
calculations. These tables include radionuclide distribution
coefficients, nuclide inventories, and waste stream inventories.
2.5.3 INFIL Input/Output
The third output section of PRESTO-EPA-CPG consists of the
input data and results for the subroutine INFIL. The input to
subroutine INFIL is presented first and consists of infiltration
control, monthly averages for hours of sunshine, daily average
temperatures, hourly rainfall amounts, and specific trench
characteristics (snow melt coefficients, trench cover thickness,
width, cover slope, porosity, and permeability).
With these input data, subroutine INFIL calculates and
outputs several data items. The most important of these are the
annual infiltration and annual precipitation. Annual
evaporation, runoff and cap infiltration are also calculated and
output.
2.5.4 Annual Summaries
Input control parameters determine the years for which
intermediate results are printed. For these years, a number of
hydrological and transport variables are output. Included are
trench cap status, water depth in trench, water loss by overflow
and drainage from the trench, and trench radionuclide
inventories. Radionuclide concentrations and flux values are
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also given for key pathways and regions of interest.
Intermediate whole body doses to the critical population group
are another important result given in this section of the PRESTO-
EPA-CPG output.
2.5.5 Radionuclide Uptake and Concentrations
The radionuclide concentration tables present, by
radionuclide, the average concentration over the entire
assessment period, and the maximum concentration for the
atmosphere, the ground surface, and for the well and stream
water.
The total uptake factors quantify, on a radionuclide
specific basis, the annual amount of nuclide uptake by the
critical population group from all potential sources. For
inhalation, it is just the quantity of nuclides inhaled. For
ingestion, it is the total consumption of nuclides (pCi/year)
from contaminated vegetation, meat, milk, and drinking water.
2.5.6 Maximum individual Dose Summary
PRESTO-EPA-CPG next outputs the data and results described
in Sections 2.5.4 and 2.5.5 for the year in which the maximum
critical population dose occurs. This allows for specific
identification of contributing pathways and radionuclides.
2.5.7 DOSTAB Result Tables
These outputs present individual dose summary rates by organ
and exposure pathways for each radionuclide.
2.5.8 Dose to Critical Population Group
The final output from PRESTO-EPA-CPG is a summary of the
whole body dose received by the critical population group (CPG).
This summary is produced for each year during the user specified
scenario run time. These data are particularly useful when the
run scenario includes analysis of collocated facilities.
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3. DESCRIPTION OF SYSCPG OPERATION SYSTEM
As it was stated in the previous chapter, the original
mainframe version of PRESTO-EPA-CPG model employed the DARTAB
subroutine, EPA's standardized generic submodel for doses and
health effects calculations, which requires a large volume of
access file. The model could therefore only be executed by a
mainframe computer. Soon after the model was released to the
public, we received numerous comments from potential users that
it would be beneficial to new users if the model could be
operated on a personal computer (PC). In responding to the
requests, the mainframe version of the model was modified and
converted into a PC version [Ro87] .
In addition, one of the input files is too complicated for a
new user to have a successful execution of the program without
undergoing several trial runs. In order to reduce the potential
of making these errors, a user friendly input file preparation
interface program was developed to automate the input file
preparation [Hu87].
The user friendly PRESTO-EPA-CPG Operation System Program,
SYSCPG, is the combination of the input file preparation program
and the PC version of PRESTO-EPA-CPG model which simplifies the
operation of PRESTO-EPA-CPG.
The first version of the operation system was published in
1989 and accepts only a monochromatic monitor. This version of
the operation system added several improvements to the previous
version which include: (1) color monitor support, (2) more user
friendly features, and (3) plotting capability for annual
individual dose.
3.1 PC VERSION OF THE PRESTO-EPA-CPG MODEL
The PRESTO-EPA-CPG model was designed to analyze the
committed annual dose equivalent to a CPG resulting from the
disposal of LLW in near surface trenches. The original mainframe
version of the model was well documented in the documentation of
the PRESTO-EPA-CPG model [EPA87] and is restated in chapter 2.
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The mainframe version of the model employed the DARTAB
subroutine, which prohibited executing the model on a personal
computer. To execute the model on a personal computer, it is
necessary to modify the model to reduce the core memory
requirement and to improve the process efficiency as well. The
major modifications of the model include the replacement of the
DARTAB subroutine with the DOSTAB subroutine, elimination of the
QUANC8 function, adding HUNG function, and adjustment of I/O
statements [Ro87].
The replacement of the DARTAB subroutine with DOSTAB has
reduced considerably the core memory requirement. To calculate
the dose equivalents resulting from human exposures, the DOSTAB
subroutine reads a set of dose equivalent conversion factors from
the dosimetric input file, which were precalculated from the
RADRISK file using the similar and updated methodology as used in
the original DARTAB subroutine. The results of the calculation
are printed out in much the same format used in the mainframe
version of the model.
The elimination of the QUANC8 function, a function for
integrating an algebraic function having an infinite limit,
prevents the tedious numerical integration of Rung's correction
factor [Hu80]. The modified model employs an analytical solution
as derived by Hung [Hu86] and calculates the correction factor in
HUNG function. This modification resulted in some savings in the
process time. In addition, the model calculates and prints out
the dose equivalent incurred through the drinking water pathway
as a component of the ingestion pathway. A complete listing of
the PC version of the PRESTO-EPA-CPG model is presented in
Appendix C. The PC version of PRESTO-EPA-CPG will be called
PRESTO-EPA-CPG throughout the rest of this documentation.
Four improvements are made to this version (Version 2.1) of
PRESTO-EPA-CPG model. They are (1) addition of the daughter
nuclide in-growth effects into the risk assessment, (2) update of
dose and risk conversion factors to 1994 level, (3) addition of
annual mortality and risk incidence calculation, (4) adaption of
International System (SI) units.
3.2 DESCRIPTION OF THE SYSCPG OPERATION SYSTEM
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3.2.1 General
The PRESTO-EPA-CPG operation system, SYSCPG, is designed to
help the user of the PRESTO-EPA-CPG model to prepare the input
data files, to perform necessary file management for the
execution of the compiled PRESTO-EPA-CPG objective module, and to
automate the execution of the PRESTO-EPA-CPG model. In creating
an input data file, the program also directs users to enter each
individual datum in the right format and at the right data field.
The program also provides the capability of editing the
input data file which includes line editing of the input file,
display of the input file, line-by-line comparison with a
predesignated input file, and the insertion and deletion of
radionuclides to be considered in the analysis.
In managing the data files for the execution of the compiled
objective module, the operation system helps users to clear the
files which need to be deleted, check the availability of the
storage volume, and save the preexisting output file.
Although there are three input files required to execute the
PRESTO-EPA-CPG model, the SYSCPG operation system includes the
preparation of the environmental and nuclide specific input file
only because this file is the most complicated input file of all
and needs the most attention.
The preparation of the INFIL subroutine input file is
excluded from the program because there would be only one line of
input data to change if there is a change in the trench cap
design.
The preparation of the dosimetric input file is also
excluded from the SYSCPG program because the file is independent
of site location and facility design, and no change is necessary
under normal application.
3.2.2 System Structure
The structure of the PRESTO-EPA-CPG operation system
consists of many subprograms each of which performs a designated
function. The subprograms include 10 operation programs, 7
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batch programs, 3 direct input data files, 4 system data files,
and 2 compiled objective program.
The operation programs include GRAPH.BAS, INCPGC.BAS,
INCPGD.BAS, INCPGE.BAS, INCPGI.BAS, INCPGR.BAS, LOGO.BAS,
MENU.BAS, MENUED.BAS, and RUNCPG.BAS. The batch programs include
COPFIL.BAT, COPY1.BAT, COPY2.BAT, COPY3.BAT, COPY4.BAT,
RUNCPG.BAT, and SYSCPG.BAT. The three direct input files are
INCPG.DAT, INFIL.DAT, and DOSEFAC.DAT and the 4 system data files
include STCPG.DAT, PRDOSFAC.DAT, PRSTCPG.DAT, and PRSTGRAP.DAT.
Finally the compiled objective files include CPGPC.EXE and
DATACHK.EXE.
The functions of each subprogram are described as follows:
GRAPH.BAS:
an operation program which allows the user to
have a quick check on the results of the
program execution by plotting the annual
equivalent dose with simulation time on the
screen.
INCPGC.BAS:
an operation program which allows the user to
make a line-to-line comparison of the input
file with a predesignated standard input file
to locate errors in the input file;
INCPGD.BAS:
INCPGE.BAS:
INCPGI.BAS:
INCPGR.BAS:
LOGO.BAS:
an operation program which allows the user to
delete radionuclides of no concern, thus
saving the calculation time.
an operation program which allows the user to
make line editing of the input file;
an operation program which allows the user to
insert radionuclides of his interest;
an operation program which allows the user to
have quick review of the entire input file;
a program which displays the logo of the
SYSCPG program;
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MENU.BAS:
MENUED.BAS:
RUNCPG.BAS:
COPFIL.BAT:
COPY1.BAT:
COPY2.BAT:
COPY3.BAT:
COPY4.BAT
RUNCPGB.BAT:
an operation program which displays the main
menu of operation and subsequently loads the
operation program selected by the operator;
an operation program which displays the
editing menu and subsequently loads the
editing program selected by the operator;
an operation program which performs file
management, including the saving of the
preexisting output file, checking of the
available storage volume, and execution of
the PRESTO-EPA-CPG program;
a batch program which copies an input data
file from the standard input data file;
a batch program which duplicates the current
input file, standard file and dosimetric file
for editing use;
a batch program which replaces the current
file with the update2d file for editing use;
a batch program which replaces the old files
with updated final files and deletes all the
temporary files during the course of editing;
a batch program which deletes all of the
temporal files created for editing purpose.
a batch program which prepares the files and
issues the command to execute the PRESTO-EPA-
CPG model;
SYSCPG.BAT:
a batch program which issues the command to
run the LOGO.EXE program;
DOSEFAC.DAT:
an input data file which contains the
effective whole-body dose equivalent
conversion factors;
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INCPG.DAT:
INFIL.DAT:
STCPG.DAT:
PRDOSFAC.DAT:
PRSTGRAP.DAT:
PRSTCPG.DAT:
CPGPC.EXE:
an input file containing environmental and
radionuclide-specific data;
an input file containing trench cap
characteristic and local meteorological data;
a standardized input file equivalent to the
INCPG.DAT file;
a permanent data file containing effective
whole-body dose equivalent conversion
factors, which includes all 40 radionuclides
built in the model;
a permanent data file containing the
standardized annual effective whole-body dose
equivalent conversion factors, which is used
to plot the annual dose for testing the
plotting operation;
a permanent data file containing the
standardized environmental and radionuclide
specific input file, which includes all 40
radionuclides;
an executable PRESTO-EPA-CPG module used
primarily for the calculation of the
committed annual effective dose equivalent;
and
DATACHK.EXE:
an executable file used to locate the illegal
input data in the environmental and
radionuclide specific input file.
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4. SYSTEM INSTALLATION
The PRESTO-EPA-CPG operation system is designed to be
operated on an IBM PC/AT compatible microcomputer. The computer
should be equipped with a math co-processor (8087/80287 or
equivalent) and have a minimum of one megabyte of disk storage
after all of the software has been stored in the disk.
The system software is recommended to be installed on a hard
disk drive and the same drive can be used to store the output
file and the temporal output file. Normally all of the system
operation software, executable module of PRESTO-EPA-CPG, the
sample input and output, and the standard input file can be
transmitted to a user in a high density floppy diskette. To
install the system, simply copy all of the files into the same
directory or subdirectory. The system will then be ready for
operation.
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5. SYSTEM OPERATION
The PRESTO-EPA-CPG operation system program is a menu-
directed, user friendly system. Detailed instructions of the
system operations are displayed on the screen so that the users
may proceed with the operations by simply following the
instructions printed on the screen. This chapter provides the
supplemental instructions to the system operation.
5.1 START UP
To start the system, proceed as follows:
1. Turn on the power switch, access the disk operating
system (DOS), and change the directory to the DOS
prompt corresponding to the drive in which the software
package is stored;
2. Type the commend, "SYSCPG"; the logo of the operation
system will appear, and finally;
3. Press any key to display the main menu (see Figure 5-
1) .
PRESTO-EPA-CPG OPERATION SYSTEM Version 2.1
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MAIN MENU
1. Copy a New Input File from
the Standard Input File
2. Edit the Existing Input File
3. Test the Current Input File
4. Execute PRESTO-EPA-CPG
5. Print out CPG.OUT
6. Plot the Annual Doses
7. End of Operation
*** Enter your selection number
Figure 5-1. Main menu of the operation system.
The system is now ready to receive the user's selection for
operation. Upon receiving the selected number, the system will
transfer the operation to the corresponding subsystem. When "End
of Operation" is selected, the system will return to the DOS
system.
5.2 COPY A NEW INPUT FILE FROM THE STANDARD INPUT FILE
This option is recommended for creating a new input file.
Since the main input file, INCPG.DAT, contains many data which do
not require change from the standardized file, STCPG.DAT, built
in the system, it is more efficient to create a new main file by
simply copying the standardized file. Therefore, a massive
typing of a new file can be prevented. Any changes of the site
specific data may be edited from the copied file using the file
editing operation discussed in the following sections.
To exercise this option, simply respond "1" to the request
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(see Figure 5-1). To avoid this selection being made by accident
and subsequent loss of the existing input file, the system
responds with a warning to make sure this is indeed your
selection. This warning tells you that the copying of a new
input file will result in the loss of the old input file. Upon
your confirmation, the system will duplicate the permanent
standard file built in the system and then return to the main
menu after informing you of the completion of the copy operation.
The copied new file is designated as "INCPG.DAT."
5.3 EDIT THE EXISTING INPUT FILE
This option is designed to allow the user to edit the input
file which is stored in the INCPG.DAT file. This selection
provides five functions: 1) edit the CPG input file; 2) compare
with the standard file; 3) review the CPG input file; 4) delete
radionuclides; and 5) insert radionuclides.
When the selection is made by the user, the system displays
the menu for input file editing as shown in Figure 5-2.
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PRESTO-EPA-CPG OPERATION SYSTEM, Version 2
MENU FOR EDITING
1. Edit the CPG Input File
2. Compare with the Standard File
3. Review the CPG Input file
4. Delete radionuclides
5. Insert radionuclides
6. End of Editing
***Enter selection number
Figure 5-2. Sub-Menu for Input File Editing
5.3.1 Edit the CPG Input File
When the option of editing the CPG input file is selected
the system will transfer the control to the INCPGE.EXE program
which is followed by the read-in of the current input file.
If the input file is incomplete, the program will give an
error message, "Input file is incomplete", and then return to the
main menu. This case will never happen under a normal operation.
If the input file is complete, the system will display the
instructions for file editing, as shown in Figure 5-3. The
system will continue to request the first card number of the
block (altogether 21 lines or cards in a block) that you wish to
edit. If the card number is either No. 32 or No. 33, the program
will make an additional request for the first radionuclide number
of the block that you wish to edit. When the system receives
your response, you should see the screen display a whole block of
21-line input data with its top line being highlighted indicating
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that the line is being edited.
INSTRUCTION
1. Input the starting card number (and nuclide number if the
starting card number is 32 or 33) of the block of lines you
wish to edit;
2. Highlight the succeeding lines by pressing 'enter1, '!' or
11' until the line you wish to edit is highlighted;
3. Edit the line by using ' -»' to copy, new character to replace
the old one, 'backspace1 or ' 'to change the previous entry,
'ins1 to insert, and 'del' to delete.
4. Press 'enter' when all of the necessary editing is completed;
5. Repeat steps 3 and 4 until all of the lines you wish to edit
are completed;
6. To quit or move to another page, press 'esc' at any time
***Press any key to continue
Figure 5-3 Instructions for File Editing.
To edit the highlighted line, proceed as instructed in
Figure 5-3. After the updated line data are entered, the system
will display the updated line of input data and move on to
highlight the next line for editing.
To terminate the editing of the current block of input data,
you may simply press the 'esc' key. The system will go back to
request the first card number of the block that you wish to edit.
This will commence another editing cycle for the newly requested
block.
You may escape from the editing mode by pressing the 'esc'
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key when the first card number of the editing block is requested.
Based on your response directed by the menu, the system will
either replace the input file with an updated file or do nothing
to the existing input file and return to the menu for editing.
5.3.2 Comparing with a Standard File
This option provides the capability of a line-by-line
comparison of the current input file, INCPG.DAT, with the
standard file, STCPG.DAT, and is primarily designed for checking
the format and numerical field of the input data in the current
file. It is particularly useful in locating the invalid input
data which caused the run time error in the execution of the
PRESTO-EPA-CPG model.
When this option is selected, the system starts with the
read-in of the standard and the current files. If the current
file is incomplete, the system will issue the warning message,
"INCPG.DAT is incomplete," and then return to the menu for
editing. If the file is complete, the program displays a block
of three-line information for each card starting from card number
1. Because of the limited space available on the screen, seven
blocks (only six blocks for the radionuclide-specific input data
cards) are displayed on a page. Each block displays the card
number and the data field location on the first line, the data
input from the standard input file on the second line, and the
input data from current input file on the third line.
You may move the display to the next page by pressing the
'enter1 key. To terminate the option, press the 'esc1 key. When
the 'esc' key is pressed, the system will return to the menu for
editing and will be ready for another selection.
5.3.3 Review the CPG Input File
This option provides the capability for quick review of the
entire current input file. It can be used to check the
completeness of the file or to scan the input file for any
obvious error.
When this option is selected, the system will start with a
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read-in of the current input file and check the completeness of
the file. If the file is incomplete, the system will issue a
warning message "INCPG.DAT is incomplete" and then return to the
menu for editing. If the file is complete, the system will
display the input data starting from card no. 1 and displays 20
lines on a single page. To view the next page, you may simply
press the "enter1 key. You may terminate the reviewing option at
any time by pressing the 'esc' key. When this is done, the
system will return to the menu for editing and will be ready for
another selection.
5.3.4 Delete Radionuclides
This option provides the capability of deleting
radionuclides of no interest to the user from the input files.
For maintaining the capability of comparing with the standard
input file and matching the number of radionuclides with the dose
conversion factor table, the same deletion of a radionuclide is
automatically conducted for the standard input file and dose
conversion file.
When this option is selected, the system will issue the
warning, "Deletion of radionuclides from the input file will also
result in the deletion of the same radionuclides from the
standard input file and dose conversion factor table" to give the
user a chance to save the existing files.
Upon the approval of the user, the system will proceed with
matching the radionuclide name among the current input file,
standard file, and dose conversion factor file. If there are
inconsistencies, the system will print out the inconsistencies
and return to the menu for editing. If no inconsistency is
found, the system will proceed to print out the current
radionuclide sequence and request the range of radionuclide
numbers to be deleted.
Notice that the model takes up to 40 radionuclides with each
radionuclide assigned a sequence number from 1 to 40. The system
takes these sequence of numbers as a base to identify
radionuclides rather than taking radionuclide names. The range
of "radionuclide sequence numbers" must fall between 1 and 40 or
the program will not accept the entry.
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Upon receiving the range of radionuclide numbers to be
deleted, the system will proceed with the deletion of the
designated radionuclides from the current input file, the
standard input file, and the dose conversion file; print out the
new radionuclide sequence; and ask for another block of deletion.
If the user approves the request, the system will continue to
request the range of radionuclide sequence numbers to be deleted,
and the whole cycle will be repeated. If the user denies the
request, the system will move on to ask if the user wants to save
the new files. If it is approved, the system will replace all
three files with the updated files and return to the menu for
another editing operation,- otherwise, the system will return to
the menu for editing without replacing the updated files.
5.3.5 Insert Radionuclides
This option provides the capability of inserting those
radionuclides into the input files which are of particular
interest to the user. For maintaining the capability of
comparing with the standard input file and matching the number of
radionuclides with the dose conversion file, the same insertion
of radionuclides are also automatically conducted for the
standard input file and dose conversion file.
When this option is selected, the system will issue the
warning "Insertion of radionuclides into the input file will also
result in the insertion of the same radionuclides into the
standard input file and dose conversion factor table." This
warning gives the user a chance to save the existing files.
Upon approval from the user, the system will proceed with
matching the radionuclide name between the current input file,
standard file, and dose conversion factor file. If there are
inconsistencies, the system will print out the inconsistencies
and return to the menu for editing. If no inconsistency is
found, the system will proceed to print out the current
radionuclide sequence and request for the range of radionuclide
sequence numbers to be inserted.
As explained earlier, the maximum number of radionuclides
that the model can handle is 40. Therefore, intending to insert
a number of radionuclides which will result in the total number
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of radionuclide in excess of 40 will be rejected by the system.
Upon receiving the range of numbers of radionuclides to be
inserted, the system will proceed to insert the designated
radionuclides into the current input file, the standard input
file, and the dose conversion file. The system will continue to
print out the new radionuclide sequence and ask for another
insertion. If the user approves the request, the system will
continue to request the range of radionuclide numbers to be
inserted and the whole cycle will be repeated. If the user
denies the request, the system will move on to ask if the user
wants to save the new files. If it is approved, the system will
replace all three files with the updated files and return to the
menu for editing; otherwise, the system will return to the menu
for editing without replacing the updated files.
5.3.6 End of Editing
When this selection is entered, the program will leave the
editing mode and return to the main menu for another selection.
5.4 TEST THE CURRENT INPUT FILE
This option allows the user to test the entire input file
for the illegal real numbers and integers. Since the PRESTO-EPA-
CPG code will not take any illegal real numbers and integers, it
is important to test the file before you run the code.
To test for the illegal real numbers and integers, simply
respond "3" to the request, Figure 4-1. The system responds
with an instruction and then tests the input data line-by-line
and page-by-page. Following a successful test of a line data,
the system will display the line tested. When the test reaches
the end of the page without encountering any illegal numbers, a
message, "No illegal numbers found," and a request for the
approval of continuation will be displayed. Upon the user's
approval of continuation, the system will continue on the next
cycle of testing by testing the following page. The system will
go back to the main menu automatically when the testing of the
entire file is completed.
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When an illegal number is found, the testing will be
terminated with an error message. The search for the illegal
number in the line shall be proceeded manually by the operator.
5.5 EXECUTE PRESTO-EPA-CPG
The option for the execution of PRESTO-EPA-CPG is designed
to prepare and run PRESTO-EPA-CPG. The preparation includes the
saving of the existing output file, the reminder of checking the
availability of disk storage, and the status of the INFIL
subroutine input file, INFIL.DAT.
When the option is selected, the system will ask if the user
wants to save the existing output file, CPG.OUT. If the user's
response is "no," the system will move directly to check the
available disk storage space. If the user's response is "yes,"
the system will ask for a new name of the file. Upon receiving
the new name of the output file, the system will rename the
CPG.OUT file as designated and move on to check the available
disk storage space.
The system will not check the available disk storage
automatically. Instead, it will print out the existing available
disk storage and let the user compare it with the minimum storage
requirement of 1 megabyte. This is done by asking the user "Do
you have enough free space?" If the answer is "no," the system
will remind the user to secure more free space and return to the
main menu. If the user's response is "yes," then the system will
ask if the existing INFIL subroutine input file, INFIL.DAT, is
current. If the user's response to this question is "no," the
system will remind the user to update the INFIL.DAT and return to
the main menu. If the user's response is "yes," the system will
issue the message that the system is ready to run the PRESTO-EPA-
CPG model and remind the user that the output file will be saved
in the CPG.OUT file.
Upon final user approval, the system will automatically copy
INFIL.DAT, INCPG.DAT, and DOSEFAC.DAT, data files and then run
the PRESTO-EPA-CPG program.
The PRESTO-EPA-CPG is a huge FORTRAN program requiring
relatively long time to execute the entire program. On a 286 IBM
compatible computer, it takes approximately 90 minutes to
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complete a run involving 40 radionuclides; whereas; when it is
reduced to 5 radionuclides, it takes only 15 minutes to run. On
the other hand, it takes only 2.5 minutes to complete a run
involving 40 radionuclides on a 586 IBM compatible computer. To
inform the user of the status of the run during execution, the
system will print out the year of the dose that the model is
calculating. This will continue to 1000 years for a standard
run.
When the execution is completed the system will issue the
message "Execution of PRESTO-EPA-CPG completed, and your output
is stored in CPG.OUT." The system will return to the main menu
after receiving your approval to continue.
5.6 PRINT OUT CPG.OUT
This option allows the user to print out the results of the
PRESTO-EPA-CPG run which is stored in the file, CPG.OUT. Due to
the fact that the capability of a word processor today is
remarkable, one may prefer to print out the output file through a
word processor. A word processor can print out a text file in
various options to satisfy the user's needs. For instance, a
land scape printing with a reduced character size (16.67 cpi) can
considerably reduce the number of pages to be printed and enhance
user's filing system.
When this option is selected the system will simply suggest
the user to use his/her favorite word processor and then return
to the main menu.
5.7 PLOT THE ANNUAL DOSES
This option allows the user to plot the annual committed
equivalent whole body doses against the time of simulation. This
option provides two functions: 1) to test for the graphic
capability of user's equipment and 2) to plot the results of
annual doses obtained from last execution of PRESTO-EPA-CPG
model.
Notice that the operation system software is developed for a
286 IBM compatible system with EGA color monitor. To get into
5-11
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the testing mode, simply select "2" to plot the standard output
file. If the graphic capability of the equipment meets the
requirement, you should see the display of the graph on screen.
To plot the results of annual doses obtained from the last
run, simply select "1" to the request. The annual doses will be
plotted on the screen where the maximum individual dose and its
year of occurrence can be read from the graph. If the PRESTO-
EPA-CPG model has been re-run and no results are created, the
system can not plot the annual doses. The system will respond
with a message, "No new graphic data file was created from last
run!" and then go back to the main menu. Therefore this option
can also be used as a tool to have a quick check on whether the
last run is successful.
5.8 END OF OPERATION
When this option is selected, the system will leave the
SYSCPG operation system and return to the DOS system.
5-12
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