United States
Environmental Protection
Agency
Office of Radiation Programs
Las Vegas Facility
PO Box 15027
Las Vegas NV 89114
ORP'LV 75-88
April 1978
Radiation
Radioactivity Associated with
Geothermal Waters in the
Western United States
A Modeling Effort to Calculate
Working Levels of Radon-222
and its Progeny for Nonelectrical
Applications
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Technical Note
ORP/LV-75-8B
RADIOACTIVITY ASSOCIATED WITH GEOTHERMAL
WATERS IN THE WESTERN UNITED STATES
A Modeling Effort to Calculate Working Levels of
Radon-222 and its Progeny for Nonelectrical Applications
Michael F. O'Connell
Gary A. Gilgan*
Apfil 1978
OFFICE OF RADIATION PROGRAMS - LAS VEGAS FACILITY
U.S ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
*Department of Physics, University of Nevada, Las Vegas
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DISCLAIMER
This report has been reviewed by the Office of Radiation
Programs-Las Vegas Facility, U.S. Environmental Protection
Agency, and approved for publication. Mention of trade names or
commercial products does not constitute endorsement or recommenda-
tions for use.
11
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PREFACE
The Office of Radiation Programs of the U.S. Environmental
Protection Agency has the responsibility to evaluate population
exposure from ionizing and nonionizing radiation. This role is
important in the development of Federal radiation protection
philosophies, policies and controls.
Within the Office of Radiation Programs, the Las Vegas
Facility (ORP-LVF) conducts detailed technical assessments of
various radiation sources (e.g., nuclear fuel cycle facilities,
and mineral and energy sources). These studies are supported by
field studies to enhance the data base and to verify models of
population exposure.
This report is the second of two reports which describe and
summarize initial investigations conducted by ORP-LVF of the
radioactivity associated with geothermal waters. The previous
report presented the analytical results of the field study
efforts. The present report describes a preliminary dose assess-
ment of the current nonelectrical uses of shallow geothermal
waters. This assessment will be used to determine the need for
further in situ measurements. Comments or suggestions are invited
from the readers.
Donald W. Hendricks
Director, Office of
Radiation Programs, LVF
iii
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TABLE OF CONTENTS
Page
LIST OF FIGURES v
LIST OF TABLES vi
ABSTRACT 1
INTRODUCTION 2
THE CONCEPTUAL MODEL 5
DESCRIPTION OF NONELECTRICAL APPLICATIONS 9
DESIGN STRUCTURES AND EXPOSURE PATHWAYS 14
RADON IN THERMAL WATERS 17
RESULTS 20
CONCLUSIONS 25
REFERENCES 29
APPENDICES
A NBSLD, the computer program for calculating
heating and cooling loads in buildings 33
B Conversion of BTU/hr to radon input rate,
atoms/hr 36
C GEOWL1, A program to compute working levels
of radon-222 and daughters in structures 39
D Working levels for 5 design structures using
different ventilation rates 43
IV
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LIST OF FIGURES
Figure 1. CONCEPTUAL MODEL TO CALCULATE WORKING
LEVELS BASED UPON RADON RELEASED FROM A
SPACE HEATING SYSTEM 6
Figure 2. VARIABLES REQUIRED TO CALCULATE WORKING
LEVELS INSIDE GEOTHERMAL HEATED STRUCTURES
USING CONSTANT RADON PARTITION FUNCTIONS
AND CLIMATIC DATA 21
v
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LIST OF TABLES
Table 1. DESIGN DAY PARAMETER
Table 2. OBSERVED STRUCTURAL DESIGNS OF BUILDINGS
GEOTHERMALLY SPACE HEATED
Table 3. INTERNAL LOADS OF THE BUILDING AFFECTING
HEAT LOAD AND OTHER WATER USAGE
Table 4. WORLDWIDE OBSERVATIONS OF RADON-222
CONCENTRATIONS IN THERMAL WATERS
Table 5. RANGE OF RADON-222 CONCENTRATIONS FOUND
IN THERMAL WATER IN THE WESTERN UNITED
STATES
Table 6. RADON-222 CONCENTRATIONS ASSUMED TO BE
TYPICAL OF VARIOUS APPLICATIONS OF
GEOTHERMAL WATERS
Table 7. MAXIMUM WORKING LEVELS FOR THE DESIGN
STRUCTURES DURING OCCUPATION
Table 8. POTENTIAL DOSES FROM INHALATION OF RADON
DAUGHTERS IN STRUCTURES UTILIZING
GEOTHERMAL HEAT
Page
14
15
15
17
19
19
22
23
VI
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ABSTRACT
It has been known for some time that geothermal fluids
contain a variety of dissolved minerals including radioactive
species, particularly radium-226 and radon-222. There is an
interest in examining radiation exposures to humans in contact
with these fluids or their deposited minerals. The literature
contains a few studies which have evaluated the ingestion and
inhalation of radon and its daughters in situations associated
with the balneological uses of thermal fluids. In this report,
an attempt is made to predict the radon progeny (working levels)
concentrations that could be expected inside structures using
geothermal fluids for domestic hot water and space heating
purposes.
A model is developed to calculate the working levels from
the heat load requirements that are necessary to maintain interior
conditions, during winter climatic conditions when space heating
is at its highest. Calculations were also included for an indoor
pool facility which is partially heated by the heat loss of the
pool water. The results show that the pool represents the
highest potential exposure environment. Other applications that
were included in this analysis included greenhouses, private
dwellings, and apartment and motel complexes.
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INTRODUCTION
In March 1976, the Office of Radiation Programs Las Vegas
Facility, issued a report entitled "Radioactivity Associated with
Geothermal Waters in the Western United States, Basic Data."
Presented therein were radiochemical data on water samples
collected from nearly 140 hot springs and shallow hot water
wells. During the planning stages of the previously reported
field survey, it was recognized that an accompanying assessment
of public health implications resulting from radiation exposure
from dissolved radon-222 would be desirable. Nonelectrical
applications are of particular interest since they are currently
the dominant use of geothermal resources and have recently
received additional impetus from the Department of Energy (formerly
the U.S. Energy Research and Development Administration) through
resource assessment and development projects in Northern California
and Idaho.
Nonelectrical applications of geothermal resources are not
only widespread but also thriving (Peterson, 1976). These
various applications are located in geographical areas where the
potential of developing a geothermal area is enhanced by obvious
natural emanations of the resource, i.e., hot pools, springs or
fumaroles. Historically, mineral baths and similar enterprises
represent the primary use of this resource. Present recreational
and therapeutic uses are characterized by "health" resorts,
hotels, motels, recreational vehicle parks, campgrounds, swimming
pools and "plunges," bottled mineral water producers, picnic
grounds, Federal (also State, county and city) parks, bath
houses and spas, hospitals and summer camps (Peterson, 1976).
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Additional uses have been proposed and/or developed over the
past 20 years which include residential and commercial or industrial
applications of geothermal energy. These developments have
included extensive residential space heating projects in Boise,
Idaho; Klamath Falls, Oregon; and Reno, Nevada. Also there are
geothermally heated agricultural and aquaculture projects in
California, Oregon and Colorado.
The additional impetus by the ERDA loan quarantee program
has moved project proposals into reality. For example, an onion
dehydration plant at Brady Hot Springs, Nevada and an expanded
district space heating project in Boise, Idaho.
At the present time, there appear to be no major technological
drawbacks to the utilization of a geothermal resource as a
supplement or replacement of other energy forms (in areas where
the resource is available). Processes such as refrigeration, air
conditioning, cooking, drying and chemical processing can be
assisted or replaced by geothermal energy (Reistad, 1975).
Significant limitations do exist for applications in some areas,
however, and include: low temperature, chemical composition,
reservoir production capability, waste water disposal, and
location of the resource with respect to the desired location of
use or application.
In this report, we have limited the discussion to low-
temperature geothermal applications (below boiling temperatures
at the ground surface) and to uses that were observed during the
sample collection of 1974. Five space heating applications were
found to be prevalent and have the greatest potential for develop-
ment in the future. Other applications, specifically commercial
space heating and process hot water uses, are not discussed
because these applications were not observed during the 1974
survey. Also, it is believed that the calculated working levels
should be verified using existing structures. In this report a
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methodology is developed to compute working levels based upon the
space heating and domestic hot water requirements for a private
residence, a motel, an apartment building, a greenhouse, and an
indoor swimming pool.
The methodology uses the heat load requirements for these
five applications to identify the demand on a geothermal system,
measured by flow rate (liters per hour). The radon escaping from
the heating system was assumed to be a percentage of the total
quantity of radon passing through the system. Also included are
domestic hot water uses which were assumed to release 100% of the
dissolved radon during the time of use. Estimated working levels
reported herein have not been verified at this time. Indoor air
measurements should, at a later date, be conducted to provide
verification.
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THE CONCEPTUAL MODEL
Insofar as it is known, radon and radon daughter concentra-
tions inside structures utilizing geothermal energy for space
heating or domestic purpose have not been measured. Pohl-Riiling
and Scheminzky (1972) found radon activities in air at the
Badgastein spa in Austria to vary from 500 to 8000 picocuries per
liter (pCi/1). The Austrian study did not provide a correlation
between dissolved radon concentrations in water and concentrations
in air. However, the authors felt barometric pressure played an
important role. It was estimated that 200 millicuries of radon
per day are released from the water at this spa: partly at the
source, partly at the spills into reservoirs, and, finally,
in the treatment baths (Pohl-Ruling and Scheminzky, 1972).
A model was developed to calculate the airborne concentration
of radon and radon progeny as a function of building heat load
requirements in conjunction with a mass balance concept to describe
radon gas buildup and loss within the structures. This model is
depicted in Figure 1. There are three steps in the computations
as shown in the figure.
The first step is to calculate the required heat, in British
Thermal Units (BTU) to maintain interior design conditions for a
specific winter environment. This is accomplished using the
National Bureau of Standards Load Determination program (NBSLD)
for computing heating and cooling loads in buildings (Kusuda,
1976).
For step two, the radon input rate is calculated assuming
that the required heat is provided by a geothermal source, that
the heat exchange efficiency is predetermined, and that the
5
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DESIGN WINTER
CLIMATIC
CONDITIONS
STRUCTURAL DESIGN
AND OCCUPANCY DATA
RADIOACTIVE
DECAY
HEAT REQ'D
TO MEET
DESIGN
CONDITIONS
T
WELL CHARACTERISTICS
TEMP., RAPON CONC., ETC.
VENTILATION,
RADON
DAUGHTERS
WORKING LEVELS
\
AMBIENT
RADON +
DAUGHTER
CONC.
COMPUTATIONS AND THEIR SEQUENCE
1 HEATING AND COOLING LOAD DETERMINATION PROGRAM,
NATIONAL BUREAU OF STANDARDS, APPENDIX A
2 RADON INPUT RATE, APPENDIX B
3 WORKING LEVEL CONCENTRATIONS USING GEOWLI, APPENDIX C
Figure 1. Conceptual model to calculate working levels
based upon radon released from a space heating
system
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release fraction of radon from the heat exchangers is known.
Radon release fraction into the room was estimated to be one
percent (1%) of the total radon flowing through the system.
Radon is expected to be released within these design structures
because it has been reported that hydrogen sulphide, another
dissolved gas species, was detectable inside geothermally heated
homes in Boise, Idaho. Actual radon or radon progeny data are not
available to accurately estimate this "partition factor."
Potential multiple sources such as leakage around pipe fittings,
valves and vented surge tanks can and probably exist.
For domestic uses and pools, the degassed radon is assumed
to be totally released into the surrounding air and to be distributed
equally throughout the structure.
In the case where geothermal water is used for both heating
and domestic hot water, the input rate of radon (R) in picocuries
per hour (pCi/hr) to a structure can be represented by the following
equation:
R(pCi/hr) = Q«K-a-C
o-oi
Where :
Q - the NBSLD output of hourly heat load (BTU/hr) required
to space heat a structure under designed climatic
conditions .
K - a constant to convert BTU/hr to liters per hour of
required hot water. The radiator and hot water
systems were assumed to operate at an inlet water
temperature of 82 °C with a 8.3°C temperature loss across
the heat exchangers. (K = 0.0309 liters/BTU)
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a - the estimated partition factor or ratio of radon in
air versus in water (0.01 for heat exchangers, 1.0
for pool and domestic uses).
W,- the average volume of domestic hot water used per hour,
(from Table 3).
C - the concentration of radon in the geothermal fluid,
pCi/1.
The calculated radon input after an hour is subsequently
reduced by ventilation and exponential decay (in Step three).
This assumes that the ventilation make-up air contains only
background concentrations of radon which cycles between 0.03 to
3.5 pCi/1 daily (Johnson, et al., 1973). The resulting buildup
of decay products (daughter isotopes of radon-222) are also
affected by decay and ventilation processes. To remain conserva-
tive, "plate out" of the daughters was not considered. A computer
program was developed from radon mass balance equations found in
previous reports by Wilkening and Watkins, (1976) and Barton, et
al. , (1973). The program identified by the acronym, GEOWL1, is
described in Appendix C.
The model was used to calculate a 24-hour working level
profile for radon and its daughters that could be expected inside
the enclosed buildings of the five applications under discussion
in this report. Results were obtained to show the variation in
the profiles with ventilation rates ranging from 0.5 to 4 air
changes per hour (ACH). Appendix D summarizes these calculations.
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DESCRIPTION OF NONELECTRICAL APPLICATIONS
Many geothermal fluids are currently exploited for space
heating and for domestic hot water uses. In this report, five
applications were chosen as being representative of such uses in
the western United States. For each case, an example is believed
to be available in the western United States to verify the dose
model presented herein. The design parameters for the structural
and climatic variables do not describe a particular known building
but were compiled from a number of firsthand observations. The
calculated radon working levels are intended to show the relative
potential for exposure to radon daughters among the various uses.
At most of the observed uses, local geothermal resources
were developed to compliment or even substitute other energy
systems. It is apparent that low-temperature (below 160°C)
geothermal reservoirs can be utilized for many uses. For instance,
economic incentives and creative business attitudes have resulted
in investments in agricultural uses including fish farming,
vegetable and flower production, commercial processing of asphalt
emulsions, milk pasteurization, snow melting and a unique business
concern which casts plastic explosives (Garside, 1974). For
these and other applications, minimum technical expertise was
required but much experimentation and inventiveness is evident.
The hot water (or low temperature steam) source such as artesian
wells, springs, pools or fumaroles were tapped by various means
to divert the fluid to a nearby structure. In some cases, the
natural flow was insufficient to meet demand; therefore, pumps
and deeper wells were required.
If reservoir temperatures up to 250°C were available, numerous
industrial processes could be adapted to geothermal energy.
9
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Reistad (1975) has compiled a table of various processes and the
required temperature for potential geothermal reservoir develop-
ments. Of course, in order to produce reservoirs of high temperature
water, sophisticated drilling and engineering techniques are
needed.
For purposes of this report, the geothermal fluids available
to provide space heating and domestic hot water for the applications
are assumed to be only 82°C at the point of heat release. Thus
these geothermal sources are simply a hot water system with no
flashing (phase separation). Of course, the reservoir temperatures
may be much higher.
Heat extraction methods observed during the sampling phase
were dependent upon the chemical constituents of the geothermal
fluids. Some of the fluids are corrosive (low pH) and present
scaling problems (high mineralization). In these cases, primary
interfaces or sacrifice systems are used to heat water or air
which in turn is circulated to the heat exchangers. Such systems,
being exposed to such fluid chemistry, are constructed to withstand
the geothermal environment. For example, in Klamath Falls, Oregon,
within-the-well heat exchangers or U-tube exchangers have been
successfully used to minimize damage to sensitive plumbing within
the structure. This method circulates domestic water through a
pipe placed in the geothermal well, which subsequently flows to
the radiators within the structure. The water is then recycled
to the well for reheating. No geothermal water is withdrawn.
This technique also minimizes waste and discharge problems
(Peterson and Groh, 1967).
The following paragraphs briefly describe the nonelectrical
applications to be evaluated in this report. These brief descrip-
tions are derived mostly from the recollection of the authors but
some references are provided for more detail. Until the energy
crisis became evident in 1975, geothermal heat was neither
10
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developed to its best and highest use nor was it always an
economically competitive energy source. Therefore, many current
applications are simple adaptations of existing technology at the
least affordable cost. The development of future systems by
individuals, corporations and public entities may extend this
resource to new and broader applications not addressed in this
report. Reistad (1975) has outlined such scenarios.
GREENHOUSES
Large Quonset type and rectangular "hot house" structures
were observed near Susanville, California; Lakeview, Oregon;
Wabuska, Nevada; and Willard, Utah. Recently, the Oregon Institute
of Technology at Klamath Falls, Oregon designed and built a
geothermally heated greenhouse to be used to investigate construc-
tion, engineering and efficiency (Karr and Laskin, 1977). The
aforementioned observed structures are commercial ventures
operated by individuals, families or partnerships. The buildings
are made of wood or steel supporting frames with fiberglass or
glass sheathing. The principal product of greenhouses has been
tomatoes although at a noncommercial greenhouse, in Colorado,
flowers were grown year round.
Hannah (1975) and Rosenbruch and Botige (1976) have reported
in detail the costs and operational aspects of the well known
Hobo Wells Hydroponics operation outside Susanville, California.
In summary, the thermal water is pumped from a spring into a
holding tank from which water is fed to a radiator. A fan is
used to circulate the air within the structure via the radiator.
Some of the spent or waste water leaving the greenhouse flows
into a nutrient tank. The nutrient solution is used for flood
irrigating within the greenhouse.
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PRIVATE RESIDENCES
In Klamath Falls, Oregon; Reno, Nevada; Susanville, California;
and Boise, Idaho, geothermal heat has been utilized in many homes
for space heating requirements and domestic hot water supplies.
In the majority of situations, each home has its own well. Very
few community heating and hot water systems have been developed
as in Iceland and Hungary. In Boise, Idaho there is a private
district heating system which supplied geothermal water to nearly
400 homes at one time. Presently 200 homes are still utilizing
this system (Hamilton, 1977).
Heat extraction, within a house, usually uses a system of
pumps, thermostats, pressure regulators, storage or surge tanks
to maintain flow, and either forced-air or gravity designed
radiators. The thermal ground water is pumped through this
system, a portion of the heat extracted, and the "waste" water is
discharged to open drainages or reinjected. As previously
mentioned, the corrosiveness and scaling potential of some
geothermal waters in Klamath Falls, Oregon prohibits it from
being distributed through the rather "delicate household systems."
At these locations a U-tube heat exchanger is placed within the
well such that city water can be heated and circulated between
the well exchanger and those within the structure (Peterson and
Groh, 1967).
In some cases (i.e., Reno), the thermal groundwater does not
contain noxious odors or tastes and also conforms to State and
Federal water supply standards for private wells. This well
water is not only used for space heating but also for domestic
purposes. In the case of shallow thermal wells in the Imperial
Valley of California, however, the hot water is high in total
dissolved solids and alkalinity. This water is normally used
solely for non-potable uses such as bathing and dishwashing.
However, it was observed that in some cases the migrant farm
labor force in that area may also use this water as a potable
water supply (O'Connell and Kaufmann, 1976).
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MOTELS AND APARTMENT COMPLEXES
At two motels and one apartment complex in Reno, Nevada,
space heating and domestic potable water are provided by geothermal
wells (O'Connell, Kaufmann, 1976). Space heating of these
structures is similar to that of a conventionally heated structure
using either baseboard floor heaters or a central heating design.
Recently, in Klamath Falls, Oregon a complex of four (4) two
story four-plexes have been built (Lund, 1977). The complex
utilizes individual forced-air heat exchangers such that new
geothermal water is only added to the circulating system when the
temperature of the system dips below a predetermined level. The
"used" water is released to a storm drain.
A typical heating system for such a large structure requires
the hot well water to be pumped to a central storage tank and
then recirculated to each unit. This provides for controlled
temperature distribution and less thermal waste.
SPAS AND RECREATIONAL FACILITIES
Perhaps the earliest record of the use of geothermal resources
is the development of bathing communes and resorts around natural
emanations. People of ancient Greece, the Roman Empire, Israel,
Babylonia and other cultures developed and embraced the use of
mineral spring areas (Horvath and Chaffin, 1971).
Many of the locations sampled during 1974-1975, were either
active, business ventures or abandoned historical relics of early
attempts (O'Connell and Kaufmann, 1976). Commonly found at these
facilities are large swimming pools (enclosed if in a cold
climate), sauna rooms and hot whirl-pool type baths. "Vapor
caves" were also observed in Colorado which were simply manmade
caverns having hot spring water seeping out of the surrounding
rock. Peterson (1976) has reported that 250 hot and mineral
spring enterprises are currently operating in the United States.
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STRUCTURAL DESIGNS AND EXPOSURE PATHWAYS
Five different structural designs are under consideration.
They are: 1) a single story private home, 2) a single story
motel, 3) a two story apartment building, 4) a glass greenhouse,
and 5) an indoor swimming pool. Examples of these structures
were observed during field sampling exercise. Also, Hannah
(1975) and quarterly bulletins from the Geo-Heat Utilization
Center at the Oregon Institute of Technology describe these and
many other specific nonelectrical applications.
Tables 1, 2 and 3 provide a summary of pertinent input data
for the National Bureau of Standards Load Design (NBSLD) computer
program. This program is described in appendix A. The output
obtained from this program is a daily profile of hourly heat
requirements (BTUH) to balance structural and occupational heat
losses. This heat is provided solely by the geothermal fluid.
For the subsequent calculations of radon release, it is assumed
that the hot geothermal water is circulated within the structure
and not reheated, but reinjected or released to surface drains.
The Environmental Protection Agency feels that the primary
exposure pathway to occupants of these structures is inhalation
of radon daughters from the decay of radon released to occupied
TABLE 1. DESIGN DAY PARAMETERS
Maximum outdoor temperature -6°C (21°F)
Daily range of outdoor temperature 17°C (10°F)
Design outdoor temperature -23°C (10°F)
Ground heat transfer coefficient 0.6 BTUH/m2/°C
Outdoor relative humidity 50%
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TABLE 2. OBSERVED STRUCTURAL DESIGNS OF BUILDINGS
GEOTHERMALLY SPACE HEATED
STRUCTURE DIMENSIONS, meters
DESCRIPTION
EXTERIOR WALL COEFFICIENTS
Transmission/Solar Absorption
BTU per (hour)•(meter2)•(°C)
Greenhouse 18.2 x 12.2 x 3.6
Apartment 30.4 x 9.1 x 5.2
Builidng
Motel
9.21 x 6.1 x 2.6
Indoor Pool 28.9 x 15.2 x 4.6
Pool size 22.8 x 9.1 x 2.1
Private 19.4 x 7.6 x 3
Residence
Garage 5.5 x 4.6 x 3
A light frame structure 2.2 0
constructed solely of 1/4"
single pane glass
A two story concrete block 2.24 13.44
structure with interior gypsum
board walls. The building is
divided into ten-27.7m2 units.
Each unit has 8.9m2 of 1/4" single
pane glass
A single story concrete block 2.24 13.44
structure with interior gypsum
board walls. The building is
divided into twenty-27.7m units
with 2.2m2 of 1/4" single pane glass
per unit
A concrete block structure with 6.04 9.74
35.7m2 of 1/4" single pane glass
A wood frame structure with 6.04 9.74
exterior stucco finish and
interior of gypsum board. The
garage is heated. There are
15.6m2 of double pane window
glass.
TABLE 3. INTERNAL LOADS OF THE BUILDINGS AFFECTING
HEAT LOAD AND OTHER WATER USAGE
INSIDE
STRUCTURE °C
Greenhouse
Apartment
Building
Motel
Pool
Private
Residence
24
24
24
21
24
24
TEMP. LIGHTING LOAD
watts/m2
43
10
10
(night) 21.
(day)
10.
(continuous)
(occupied)
(occupied)
5 (occupied)
7 (occupied)
OCCUPANCY
persons/time
intervals
4
35
30
30
4
0900-1700
1700-0800
1700-0800
0900-1800
1700-0900
DOMESTIC WATER USAGE
(Eng. Manual, 1959)
liters per hour
0
94
189
1135
915
(over night) 22
(shower)
(pool makeup)
15
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areas. The secondary route is direct consumption of radon laden
water. The source of radon within the structure is the radiator,
associated plumbing and venting.
The air-water ratio between the radon content in the incoming
fluid and content in the air is defined as a partition fraction.
This factor varies according to the use and the heat transfer for
technology. For this report, partition fractions are estimated.
The domestic water usages in Table 3 are expected volumes of
radon laden hot water that will release dissolved radon at the
time of use. In recreational situations, i.e., saunas and pools,
radon will be released as the thermal water is replenished and
circulated. Daily water usage within the greenhouse was assumed
to be zero since mixing of nutrients in the holding tank before
irrigation will probably reduce the radon concentration signifi-
cantly and therefore, not contribute to the radon buildup in the
structure. Therefore, flood irrigation of the greenhouse is assumed
not to be a source of radon. The other domestic uses are primarily
bathing and washing.
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RADON IN THERMAL WATERS
Radon content of hot springs and other geothermal systems
(well, pools, etc.) have been reported worldwide. Observed
concentrations have shown that at many locations, radon will vary
considerably even within local or regional settings. This
variation has been attributed either to seismic activity (Craig,
et al., 1975), regional geology (Jurain, 1960), or cold water
intrusion (Mazor, et al., 1973). As of yet, there is no exact
correlation of radon to any natural event or situation that
enables one to predict radon concentration in groundwater other
than to note that its presence can be expected. It has also been
found that radon in producing geothermal zones will vary with
time and production volumes (Stoker and Kruger, 1975). In Table
4, radon concentrations in thermal systems observed worldwide are
summarized.
TABLE 4. WORLDWIDE OBSERVATIONS OF RADON-222
CONCENTRATIONS IN THERMAL WATERS
Rn-222
Location Pico Curies*/Liter Reference Source
Badgastein, Austria 500 - 120,000 Pohl-Ruling
(1972)
Bath, England 23,000 (average) Andrews and Wood
(1974)
Taupo Graben, 800 - 320,000 Belin (1959)
New Zealand
Hammat Gader, Israel 2,900 - 7,420 Mazor, et al.,
(1973)
Japan 29,000 Moringa (1958)
Kamchatka, USSR 1,000 (fumaroles) Cherdynstev
Hot Springs, National 30,500 Kuroda, et al..
Park, Arkansas, USA (1954)
Western USA 3 - 14,000 O'Connell and
Kaufmann (1976)
*10~12 curies
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It should be noted that elevated radon concentrations in
geothermal waters are sometimes within concentration ranges
typical of cold water sources. Pohl-Ruling (1972) found radon in
cold springs in the Badgastein, Austria region to vary from 100-
36,000 pCi/1. In the United States, a review of available ground
water data (438 samples) found that 74 percent contained radon
concentrations up to 2000 pCi/1 and of the remaining 26 percent,
five percent were above 10,000 pCi/1 (USEPA, 1977). In Maine and
New Hampshire, a U.S. Public Health Service study (Grune et al.,
1960) reported that of the nearly 250 cold water wells sampled,
radon concentrations exceeded 10,000 pCi/1 for 24 percent of the
locations and 100,000 pCi/1 for 2 percent.
From the previous study of low-temperature (<100°C) geothermal
fluids in the western United States, O'Connell and Kaufmann
(1976) measured radon concentrations up to 14,000 pCi/1. This
particular location was an artesian well located near the San
Andreas fault in Southern California. It has been developed to
supply a recreational spa complex with hot water for pools and
saunas. In Table 5, a summary of observed radon concentrations
throughout the western United States are presented to clarify the
various uses. They are: hydroponic applications which include
hothouse and greenhouse uses, indoor/outdoor pools and saunas
were usually recreational facilities; and potable water supplies
because at some locales the thermal water met state drinking
water standards, although in most areas, high hydrogen sulphide
concentrations or dissolved solids content limited the hot water
usage to either bathing, dishwashing, or space heating.
Radon data from the previous report (O'Connell and Kaufmann,
1976) are grouped into categories (Table 5) (as shown by the
horizontal lines). The average radon concentrations are calculated
from observed radon values. The combined averages (in Table 5)
are calculated from grouping similar uses. It was felt that the
combined averages were more appropriate to use in the calculations
since multiple uses were observed at many developments.
18
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TABLE 5. RANGE OF RADON-222 CONCENTRATIONS FOUND
IN THERMAL WATERS IN THE WESTERN US1
Number of
Observed
Uses Locations
Hydroponics
Indoor Pools
Outdoor Pools
Saunas
Potable Water
Non-Potable Water
Heat Exchanger
3
6
18
18
7
5
11
Range of Dissolved Observed
Radon-222 in Water Average
pCi/1 pCi/1
32 -
13 -
72 -
61 -
58 -
120 -
58 -
1,400
5,800
14,000
14,000
980
2,100
1,400
564
1,369
2,432
2,319
365
778
360
Combined
Average
PCi/1
564
2,231
365
490
'From O'Connell and Kaufmann, 1976
In Table 6, a summary of the radon concentrations from Table
5 is presented whose combined use approximates the five design
applications discussed in this report.
TABLE 6. RADON-222 CONCENTRATIONS ASSUMED TO BE TYPICAL
OF VARIOUS APPLICATIONS OF GEOTHERMAL WATERS
STRUCTURE
Greenhouse
Apartment Building
Motel
Private Residence
Indoor Pool
PCi/1
564
365
365
490
2231
19
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RESULTS
The concept of the model described below is based upon
standard engineering guides, a mass balance methodology and a few
critical assumptions. The results are working levels (WL) of
radon and its daughters, (polonium-218, lead-214, and bismuth-
214) inside the predescribed structures. The few critical areas
which affect the calculated working levels and more importantly,
future verification of these concentrations are:
(1) that the design day conditions are considered
typical winter conditions,
(2) that radon is degassed inside the house and can be
described as a percentage of the total radon flowing
hourly through the system,
(3) that structural heating and ventilation parameters
are adequate,
(4) that radon daughter "plate out" is not significant,
and,
(5) that higher than calculated WL's may be expected in
enclosed rooms where large quantities of water are
used and ventilation is minimal such as the laundry
or bath.
THE COMPUTER PROGRAMS
The computational sequence and input parameters of the
computer programs are shown in Figure 2. To accommodate variations
in ventilation rates, structural design and radon in water
20
-------
concentrations, these parameters remained as input variables for
each application whereas heat exchanger efficiencies, radon
air/water ratios, ambient radon concentration and climatic
conditions remained integrated into the calculations. The
calculation scheme is depicted as follows:
H
OL
r PROGRAM OU1
o.
z
Btu/hr
NBSLD
(Appendix A)
Structural Design
Ventilation rates
atoms/hr of radon
Heat Exchanger
Conversion
(Appendix B)
Radon in water cone.
Hourly WL's
GEOWLI
(Appendix C)
Ventilation rates
Figure 2. Variables required to calculate working levels
inside geothermal heated structures using constant
radon partition functions and climatic data
Working levels (WL) are computed on an hourly basis for a
24-hour cycle or a complete day. The program, GEOWLI, has the
capability of continuous operation for multiple day buildup. It
is noted however, that after the first day (24-hour period) the
subsequent hourly profiles are repeated if the same hourly radon
input and structural ventilation rates are used.
WORKING LEVEL CONCENTRATIONS
Appendix D contains a summary of calculated working level
concentrations for the previously described structures. The
output is dependent upon ventilation rate changes. In Table 7,
the maximum calculated working level concentrations are summarized
for potentially occupied time periods (see Table 3). These are
not necessarily the highest values calculated. In general, space
heating requirements are the highest in the early mprning hours
(1-5 a.m.) and subsequently also the maximum working level concentra-
tions. Since greenhouses are not occupied during those hours,
21
-------
.the maximum reported in Table 7 is not the daily maximum from
Appendix D. In the case of an indoor swimming pool, the air
temperature was allowed to drop 3°C at night. Therefore, as
shown in Appendix D, the peak heat use (and working levels) for
greenhouses and pools occurs during the occupied period.
TABLE 7. MAXIMUM WORKING LEVELS FOR THE DESIGN
STRUCTURES DURING OCCUPATION (xlO~3)
STRUCTURE AIR CHANGES PER HOUR
0.5 1.0 2.0 3.0 4.0
Greenhouse 1.18* 0.94 0.79 0.77 0.70
Apartment Bldg 1.36 1.02 0.83 0.76 0.72
Motel 1.69 1.14 0.87 0.78 0.73
Indoor Pool 29.96 9.58 3.21 1.89 1.4
Private
Residence 1.46 1.08 0.86 0.77 0.73
*i.e., 1.18 x 10 3
To estimate the potential lung dose from exposure to the radon-
222 daughters represented by the working levels shown in Table 7,
requires the selection of a dose conversion factor. Johnson, et
al., (1973) in their work on radon daughter exposures from
natural gas, identified and acknowledged the wide variation found
in the literature. They found that the important reasons that
dose conversion factors were not inter-comparable are that "each
exposure situation has involved different radon - daughter
equilibrium conditions, free ion fractions and carrier particle
sizes for attached daughters."
DOSE CONVERSION
Barton, et al., (1973) used a dose conversion factor of 100
rads per year to the lungs for a continuous exposure at one
working level (100 pCi/1 of radon in secular equilibrium with
daughters) atid a quality factor of 10. Computations of radon and
daughters using GEOWL1 show that such equilibrium is not obtained
under the conditions selected for this report. Duncan, et al.,
22
-------
(1976) used a dose conversion factor based upon a radon
daughter equilibrium ratio of 1:0.9:0.5:0.35. They computed that
0.25 working level months/year (WLM/YR) is equal to a maximum
dose of 4 Rem/year in the 5th generation bronchus of the lungs.
The aforementioned dose conversion factors may not La
adequate to describe expected doses from short term (winter
months only) exposures resulting from space heating since they
were developed using continuous inhalation models. In the case
of enclosed swimming pools and greenhouses, they may apply for
continuous users or workers. Even though 50 percent equilibrium
was not computed, the dose conversion factor 0.25 WLM/Yr was used
to develop Table 8. Because the potential for exposure from
geothermal space heating systems is highest during four winter
months, the WL's calculated for homes, apartments and motels are
for this time period. The greenhouse and pool applications use
water year round, therefore, the working levels calculated for
the worst case situation are assumed to hold for 12 months.
Using the calculated working levels in Table 7, annual doses were
derived and summarized in Table 8.
TABLE 8. POTENTIAL DOSES FROM INHALATION OF RADON
DAUGHTERS IN STRUCTURES UTILIZING
GEOTHERMAL HEAT, REM/YR
STRUCTURE AIR CHANGES PER HOUR
0.5 1.0 2.0 3.0 4.0
Greenhouse 0.94 0.75 0.63 0.61 0.56
Apartment Bldg 0.36 0.26 0.21 0.19 0.19
Motel 0.45 0.30 0.29 0.20 0.19
Indoor Pool 23.94 7.60 2.50 1.50 1.12
Private
Residence 0.38 0.28 0.23 0.20 0.19
Note: The dose contribution from the domestic
hot water uses during the non-winter seasons for the
apartment motel, and house were not included since
the maximum WL's in Table 7 showed little contribution
from this source of radon.
23
-------
CONSUMPTION DOSE
The consumption of geothermal fluids is not common place
since there are many instances of obnoxious tastes and odors.
However, in the Soviet Union, it is reported that there are 86
mineral water bottling plants presently in operation (Informatics,
1972). According to this same report, the Soviets have set a
norm of 5000 pCi/1 of radon for thermal waters to be considered
for balneological use. In the United States there are a few
places which also produce a bottled product for general consumption,
These products are available in food stores and markets nationwide.
Data is not presently available as to the radium concentration in
these waters and the subsequent radon buildup inside the containers,
From the previous report, the observed average radon-222
concentration for potable (drinkable) waters is 365 pCi/1 (Table
5). Since there are cases of intentional drinking of mineral
water at health clinics and spas and also routine consumption of
potable hot water supplies (i.e., in Reno, Nevada), an estimate
of potential exposures is warranted. The critical organ is the
stomach. The dose equivalent was reported by Suomela and Kahlos
(1972) to range from 350 to 380 mrem/yCi ingested. A worst case
estimate, assuming a daily intake of 2000 ml of raw non-boiled
water, yields a consumption dose of approximately 100 mrem/yr.
24
-------
CONCLUSIONS
Five applications of nonelectrical uses of geothermal energy
resources were evaluated for potential doses from the inhalation
and/or consumption of radon-222. These uses include spaceheating,
domestic hot water sources, and recreational examples which were
observed during a previous field sampling survey (O'Connell and
Kaufmann, 1976) .
The maximum calculated working levels for each application
are summarized in Table 7. These concentrations are expected
values during occupied periods. The annual inhalation dose to
individuals resulting from a four month exposure period (winter
conditions at design day conditions) to the maximum concentrations
are presented in Table 8. The contribution of radon-222 to the
inside air from the spaceheating model greatly exceeded that from
domestic hot water uses, therefore Table 8 contains accumulated
doses from those months of maximum spaceheat demand for the
apartment, motel and private residence applications. The greenhouse
and indoor pool examples are expected to withdraw hot water from
the geothermal reservoir year round but at reduced volume. In
some circumstances, the hot water well must be kept flowing to
prevent the well from "cooling down" and stopping artesian flow.
Elsewhere, at many recreational spas, there is little or no
control of the incoming water because the source (spring or well)
is connected directly to the mineral baths or saunas. Therefore,
for these applications, the expected doses shown in Table 8, were
calculated using the maximum working levels for year round
exposure periods.
Ingestion doses to the stomach were calculated from the
annual consumption of domestic water, all of which originated
25
-------
from the geothermal source. Even though in most cases, cold
water supplies are more likely to be used, there are circumstances
where for balneological reasons, mineral water is consumed. A
dose of 100 mrem/yr was calculated using a known radon-222
concentration (365 pCi/1) for a potable geothermal source.
The highest working levels and resulting lung "doses were
calculated for an indoor pool. The degassing of-radon from pool
water into a poorly ventilated building may produce significant
airborne concentrations. Though radon is nearly ten times more
soluble in water than oxygen from 0 to 70°C (Lawrence, et al.,
1946) , agitation from recirculation and use will release much of
the radon. The employees and repetitious users of such a facility
may accumulate long exposure periods.
At the present time specific criteria are not available to
provide guidance as to what levels are advisable for homes or
commercial establishments having the potential to accumulate
radon-222 and subsequently its daughters from building materials,
natural gas or geothermal resources (all of which are sources of
radon-222). There are recommendations and criteria coupled with
remedial measures for homes and other buildings which have been
built using uranium mill tailings for structural foundations
(e.g., in Grand Junction, Colorado) or have been built on reclaimed
phosphate strip mines in Florida. The U.S. Surgeon General's
Guidelines recommend remedial action above 0.05 WL of indoor
radon daughter products for dwellings constructed on or with
uranium mill tailings. In Canada, recently, it was announced
that 0.02WL is the primary criterion above which remedial action
will be necessary to limit radon-222 build up in homes built on .
uranium mill wastes (from a news release on behalf of the Federal
Provincial Task Force on Radioactivity, Atomic Energy Control
Board, April 7, 1977). Recently, the United States Environmental
Protection Agency recommended 0.005 WL as the upper level for new
habitable structures built on reclaimed phosphate land.
26
-------
As shown in Appendix D, the calculated WL's are inversely
related to the ventilation rate. Reduction in the working level
concentrations are particularly noteworthy for the indoor pool
circumstance where doubling of the ventilation rate can reduce
the working level value by up to 60%. For the other structures,
the change in working level is less dramatic with average reductions
of 19-25% being calculated where the ventilation rate is doubled.
V
It was found that at the maximum concentration conditions
(ACH=0.5) for any of the structures, the radon daughter build up
would not produce a working level concentration exceeding the
Surgeon General's 0.05 WL guideline if the combined average
radon-222 concentrations in water for known geothermal systems
were used. In some actual cases or locations, the guidelines
would be exceeded if a higher activity radon source was present
or if ventilation and other design parameters were not similar to
those assumed in this report. It is shown that the EPA guidelines
of 0.005 WL were not exceeded in any example structure if the
ventilation rates were 2 ACH or greater. At some recreational
facilities, where radon-222 concentrations in water were as high
as 14,000 pCi/1, the ventilation rates would have to be much
higher not to exreed this guideline.
Since there is uncertainty in the proposed model, particularly
the radon air/water partition fraction for heat exchangers and
degassing pool water, there is an obvious need for verification
studies. These efforts should be conducted at existing structures
with known radon input rates (calculated or estimated) to verify
the effect of ventilation especially in limiting circumstances
such as saunas or steam rooms where ventilation is undesirable.
Since increased ventilation produces a corresponding higher radon
input rate (replacement of lost heat causes higher flow rates
from the geothermal reservoir), optimization of competing require-
ments may be desirable for those structures found to contain high
working level values.
27
-------
Geothermal energy can be utilized for nonelectrical applications
of space heating and hot water supplies without radiological health
implications by using engineering techniques to either remove
radon from the heating system or to contain it within the system.
Recreational or balneological uses of thermal or mineral waters
present more difficult problems, yet in many cases radon and
other minerals and gases are considered desirable constituents.
28
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and lead-210 in Bath Thermal Springs compared with some
environmental waters." Health Physics, Pergamon Press,
New York, Vol. 27, No. 3, p. 307-310.
Barnett, J., 1977. National Bureau of Standards, personal
comm.
Barton, C.J., R.E. Moore and P.S. Rohwer, 1973. "Contribution
of radon in natural gas to the natural radioactivity
dose in homes." ORNL-TM-4154, Oak Ridge National
Laboratory, Oak Ridge, Tennessee.
Belin, R.E., 1959. "Radon in the New Zealand geothermal regions."
Geochim. et Cosmochim. Acta. 16, p. 181-190.
Cherdyntsev, V.V., 1970. "Origin of thermal waters on the basis
of their radioisotope content." Presented at UN symposium
on the Development and Utilization of Geothermal Resources;
Pisa, Italy.
Craig, H., J.E. Lupton, Y. Chung, and R.M. Horowitz, 1975.
"Investigation of radon and helium as possible fluid
phase precursors to earthquakes." Technical Reports 1-4.
Scripps institution of Oceanography; La Jolla, California.
Duncan, D.L., T.F. Gesell, and R.H. Johnson, 1976. "Radon-222
in potable water." Proceedings of the Tenth Midyear Topical
Symposium of the Health Physics Society; Rensselaer
Polytechnic Institute, Troy, New York.
Engineering Manual, 1959. John H. Perry and Robert H. Perry,
Editors. McGraw-Hill Book Company, New York.
Evans, Robley D., 1969. "Engineer's guide to the elementary
behavipr of radon daughters." Health Physics, Vol. 17,
No. 2,'p. 229-252.
Garside, Larry J., 1974. "Geothermal exploration and development
in Nevada through 1973." Nevada Bureau of Mines and Geology,
Report 21. University of Nevada; Reno, Nevada, 12 p.
Grinnell Company, Inc., A969. Advantages of heating with
Grinnell Thermolier unit heaters. Providence, Rhode Island.
p. 401-415.
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Grune, W.N., F.B. Higgins, and B.M. Smith, 1960. "Natural
radioactivity in ground water supplies in Maine and
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Saph-73551, U.S. Public Health Service, Division of
Radiological Health, Washington, D.C.
Hamilton, Bruce, 1977. "Boise rediscovers geothermal."
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March 11, 1977; Lander, Wyoming. Reprinted in Geothermal
Energy Magazine, Vol. 5., No. 7.
Hannah, Judith L., 1975. "The potential of low temperature
geothermal resources in northern California." Report
No. TR13, California Division of Oil and Gas. Sacramento,
California. 53 p.
Horvath, Joeseph C. and Robert L. Chaffin, 1971. "Geothermal
Energy, Its Future and Economics." Atlantic Economic Review,
Georgia State University; Atlanta, Georgia. Vol. 21,
No. 12.
Informatics, Inc., 1972. "Soviet geothermal electric power
engineering, report 2." Translation sponsored by Advance
Research Projects Agency, ARPA Order No. 1622-3, 79 p.
Johnson, R.H., D.E. Bernhardt, N.S. Nelson, and H.W. Galley,
1973. "Assessment of potential radiological health effects
from radon in natural gas." EPA-520/1-73-004, Office of
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Washington, D.C.
Jurain, G., 1950. "Methods and results of the study of
radioactivity due to radon in natural waters." Geochim. et
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Karr, Don J. and Saul Laskin, 1977. "The geothermally heated
greenhouse." Quarterly bulletin of the Geoheat Utilization
Center. Oregon Institute of Technology; Klamath Falls,
Oregon. Vol. 2, No. 3.
Kuroda, P.K., P.E. Damon, and H.I. Hyde, 1954. "Radioactivity
of the spring waters of Hot Springs National Park and
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Vol. 252, p. 76-96.
Kusuda, Tamami, 1976. "NBSLD, the computer program for heating
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the National Bureau of Standards, Washington, D.C., 150 p.
Lawrence, J.H., W.F. Loomis, C.A. Tobias, and F.H. Turpin, 1946.
"Preliminary observations on the narcotic effect of xenon
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Lund, John W., 1977. "Direct use of geothermal water for apartment
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Center. Oregon Institute of Technology; Klamath Falls,
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Mazor, E., A. Kaufman, and I. Carmi, 1973. "Hammat Gader
(Israel): geochemistry of a mixed thermal spring complex."
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Morinaga, H., 1958. "Radioactive springs in Japan." Centre
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Internazaionale di Idrologia e Climatologia, Lacco, Ameno
d'Ischia. Oct 4-8, 1958, p. 1057-1066.
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activity associated with geothermal waters in the western
United States, basic data." ORP/LV-75-8A. Office of
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Las Vegas, Nevada. 25 p.
Olivieri, Joseph B., 1973. How to Design Heating and Cooling
Comfort Systems. Business News Publishing Company;
Birmingham, Alabama. 316 p.
Peterson, Normal V. and Edward A. Groh, 1967. "Geothermal
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Peterson, Richard E., 1976. "Nonelectric geothermal, A
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Pohl-Ruling, J. and F. Scheminzky, 1972. "The natural
radiation environment of Badgastein, Austria and its
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symposium on the Natural Radiation Environment; August 7-11,
1972. Houston, Texas.
Reistad, Gordon M., 1975. "Analysis of potential nonelectrical
applications of geothermal energy and their place in the
national economy." UCRT-51747, Lawrence Livermore Laboratory,
Livermore, California. 27 p.
Rosenbruch, Jimmie C. and Robert G. Bottge, 1976. "Geothermal
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Geothermal Energy Magazine, Vol. 4., No. 10, p. 36-38.
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Ross, Shepley L., Editor, 1974. Ordinary differential equations.
Zerox College Publishing, Lexington, Massachusetts.
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Stoker, A.K. and P. Kruger, 1975. "Radon measurements in
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Palo Alto, California. 116 p.
Suomela, M. and H. Kahlos, 1972. "Studies on the elimination
rate and the radiation exposure following ingestion of
radon-222 rich water." Health Physics, Vol. 23, No. 5,
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U.S. Environmental Protection Agency, 1977. "Radiological
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EPA 520/1-77-009, Office of Radiation Programs, Washington,
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32
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APPENDIX A
NBSLD, THE COMPUTER PROGRAM
FOR CALCULATING HEATING AND COOLING LOADS IN BUILDINGS
33
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NBSLD, the National Bureau of Standards Load Determination
program is a compilation of various algorithms and subroutines
recommended by the American Society of Heating, Refrigeration and
Air Conditioning Engineers Task Force Group on Energy Requirements.
The program is very extensive and contains, within the subroutines,
thermal resistance data for many materials.
Kusuda (1976) describes the energy balance equations that
depict the amount of energy transferred from and simultaneously
added to a room at any time. Wehlage (1976) and Olivieri (1973),
in their books on design, have outlined and presented examples of
heat transfer through exterior structural surfaces. The fundamental
heat transfer equation which describes heat (energy) conduction
through a medium is:
where: Q = A(u)(AT)
A = surface area, ft2
u = coefficient of transmission, BTU/hr ft2 °F
AT = temperature differential of media, °F
Q calculates to be, in english units, BTU/hr (BTUH). Thermal
resistances (R) are reported for various construction materials
by the American Society of Heating, Refrigeration, and Air Condi-
tioning Engineers (ASHRAE, 1972). The coefficient of transmission
is related to R as:
u = 1/R
For building material of multiple layer construction an
overall coefficient of transmission is computed from:
m _i
u = (ZR ) where m = number of layers
1 m
34
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In applications involving four walls, a roof, a floor,
interior ceiling, windows, doors, and infiltration of outside
air, the calculations become quite lengthy. Complications arise
from internal energy sources, solar loading, exterior shading,
and thermal storage effects of the building. The resulting
computations are not practical for every day usage. Therefore,
many architects result to standard "rules of thumb" which have
been developed for various climatic conditions. This may result
in over design for heating and cooling equipment.
Since geothermal application are using resources of possibly
marginal temperatures, and are faced with restrictions on disposal
of waste water, and withdrawal of groundwater, it was felt that
through the use of this computer program, the calculations could
be performed for any structure with adequate accuracy to optimize
resource utilization. The program, NBSLD, developed by the
National Bureau of Standards Center for Building Technology was
the first program of its kind to be available. Since 1976,
others have been developed at the University of California,
Berkeley and the U.S. Army Civil Engineering Laboratory,
Champaign, Illinois (Barnett, 1977).
The output from this program is a 24-hour profile of hourly
energy requirements. For purposes of this study, the design
characteristics found in Tables 1-3 were used to compute the
profiles for the 5 structures. The ventilation rate was varied
from 0.5 to 4 ACH to compute the increased heating load that
would be required to maintain similar interior conditions. The
hourly WL profiles are shown as a function of ventilation rate in
Appendix D.
35
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APPENDIX B
CONVERSION OF BTU/HR TO RADON INPUT RATE, ATOMS/HR
36
-------
A data processing program was written in BASIC language to
be used with a Hewlett Packard model 9830 programmable calculator.
The program converts the heat load data from NBSLD plus domestic
water usuage and/or pool makeup water requirements, to an hourly
radon-222 input rate. This program assumes the following:
(1) the temperature drop across the heat exchangers
for space heating is 8.3°C (15°F),
(2) space heating needs for each case except for the
indoor pool (pool water losses provide significant
heat input) is provided by the heat exchangers
only, and
(3) the radon air/water heat exchanger partition fraction
is 0.01.
The basic relationship describing heat release from a
radiator with heat supplied by a fluid medium (Grinnell, 1969)
is:
Heat transferred = Flow rate x fluid density x specific
heat x temperature change
The system flow rate (liters per hour) is calculated from
the above equation. The fraction of radon-222 release inside the
structures (assumed to be 0.01) is used to estimate, from the
average radon in water concentrations, the radon input rate
(atoms/hr).
37
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The hourly radon input rate from space heating sources is
adjusted by the additional releases from the domestic and/or pool
water sources, assuming that 100% of the dissolved radon from
these uses are released to the interior air.
38
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APPENDIX C
GEOWL1
A PROGRAM TO COMPUTE WORKING LEVELS OF
RADON-222 AND DAUGHTER IN STRUCTURES
39
-------
The purpose of the GEOWL1 program and its associated subroutines
is to calculate the number of atoms of radon-222 and its first
three daughters (Po-218, Pb-214, Bi-214) in a room under the
following conditions:
1) Radon enters and disperses on a continuous basis but
the input rate will vary hourly, as a function of heating require-
ments
2) there is an exchange of air volume with outside air,
(i.e., known ventilation rate)
3) the air being exhausted (from ventilation) contains
the same concentration of radon daughters as the room air (i.e.,
assume complete mixing) ,
4) the incoming air (from ventilation) contains background
levels of radon and daughters. (Note: A background concentration
for radon-222 was assumed to be 0.1 pCi/1, and the daughters were
assumed to be in the ratio 1./0.6/0.5).
Working levels are calculated as described by Evans (1969)
coupled with a mass balance equation to account for the buildup,
ventilation losses and radioactive decay of radon-222 and daughters.
This mass balance is represented as:
* [Radon] = R*doninput - R**°*out - Radondecay
Similar forms for subsequent radon daughters can be written
except that the input terms are provided by the decay of the
preceding isotope.
40
-------
The radon mass balance equation can be written as:
* = ABTU + ABkgd
V - A F -
in out
Where A = Radon input from heat exchangers,
BTU
atoms/hour
= Radon background concentration, atoms/liter
V = Ventilation rate, liters/hour
A = Total radon concentration inside structure,
atoms
F = Fraction of room (air) volume removed by
ventilation, air changes per hour
_ i
A = Radon decay constant, hour
cl
Rearranging this equation yields:
dA + A-A + AT = Afikgd.V + A or
dA + AUa+F) =
This expression and subsequent expressions for the radon
daughters take the form of a linear differential equation:
dy_ + P(x)Y = Q(x)
dx
which has an integrating factor of the form:
e/P(x)dx
41
-------
which yields a solution of the form (Ross, 1974) :
-/P(x)dx
Y = e
f/P(x)dxQ(x)dx +
Using this solution, the differential describing radon-222
concentration at time, t, is:
A = A + (A -A. )e~t(Aa"l"F) where:
k OK
Ak = ABkgd'v + ABTU
<* + F)
A = Radon at t = o, a constant assumed to equal
ambient air concentrations.
Similar computations are necessary for the radon daughters
Po-218, Pb-214 and Bi-214. Solutions to the linear differential
equation 2, are lengthy and will not be presented here. GEOWLl
incorporates these solutions to produce a 24 hour profile of the
number of atoms present inside the buildings. Working levels are
calculated for midpoint of each hour using the method described
by Evans (1969) .
This program utilizes a CDC-6400 computer which computes the
parental decay, the subsequent ingrowth of daughters, the losses
due to ventilation all on a repetitious time scale of one second.
The number of atoms of radon and its daughters are continuously
summed. The program does not account for losses of radon daughters
from free ion attraction to dust and subsequent deposition nor
plating out on wall surfaces.
42
-------
APPENDIX D
WORKING LEVELS FOR THE 5 DESIGN STRUCTURES
USING DIFFERENT VENTILATION RATES
43
-------
SUMMARY OF WORKING LEVELS (xlO~ ) CALCULATED
FOR A GREENHOUSE USING GEOTHERMAL WATERS
CONTAINING 564 pCi/1 RADON-222
HOUR AIR CHANGES PER HOUR
0.5 1.0 2.0 3.0 4.0
1
2
3.
4
5
6
7
8
9
10
11
12 (noon)
13
14
15
16
17
18
19
20
21
22
23
24
1.16*
1.17
1.19
1.19
1.20
1.20
1.20
1.18
1.16
1.14
1.13
1.11
1.09
1.07
1.06
1.05
1.07
1.09
1.10
1.11
1.12
1.13
1.14
1.15
0.95
0.96
0.96
0.96
0.96
0.96
0.96
0.94
0.93
0.93
0.92
0.91
0.90
0.89
0.89
0.88
0.90
0.91
0.92
0.92
0.93
0.93
0.94
0.95
0.80
0.80
0.80
0.81
0.81
0.81
0.81
0.79
0.79
0.79
0.78
0.78
0.77
0.77
0.77
0.77
0.79
0.79
0.79
0.79
0.79
0.80
0.80
0.80
0.78
0.78
0.78
0.78
0.78
0.78
0.78
0.77
0.77
0.76
0.76
0.75
0.75
0.75
0.75
0.75
0.76
0.76
0.77
0.77
0.77
0.77
0.77
0.78
0.71
0.71
0.71
0.71
0.71
0.71
0.71
0.70
0.70
0.70
0.70
0.70
0.70
0.70
0.69
0.69
0.70
0.70
0.70
0.70
0.71
0.71
0.71
0.71
_ 3
*i.e., 1.16 x 10 WL
44
-------
_3
SUMMARY OF WORKING LEVELS (xlO ) CALCULATED
FOR AN APARTMENT BUILDING USING GEOTHERMAL WATERS
CONTAINING 360 pCi/1 RADON-222
HOUR AIR CHANGES PER HOUR
0-5 i.o 2.0 3.0 4.0
1
2
3
4
5
6
7
8
9
10
11
12 (noon)
13
14
15
16
17
18
19
20
21
22
23
24
1.34*
1.35
1.35
1.35
1.36
1.36
1.36
. 1.36
1.36
1.35
1.34
1.33
1.31
1.31
1.30
1.31
1.31
1.31
1.31
1.31
1.32
1.33
1.33
1.34
1.02
1.02
1.02
1.02
1.02
1.02
1.02
1.02
1.02
1.01
1.00
0.99
0.99
0.98
0.98
0.99
0.99
0.99
0.99
0.99
1.00
1.00
1.01
1.01
0.82
0.83
0.83
0.83
0.83
0.83
0.83
0-82
0.82
0.82
0.81
0.81
0.81
0.81
0.81
0.81
0.81
0.81
0.81
0.82
0.82
0.82
0.82
0.82
0.75
0.75
0.76
0.76
0.76
0.76
0.76
0.76
0.75
0.75
0.75
0.74
0.74
0.74
0.74
0.74
0.74
0.74
0.74
0.75
0.75
0.75
0.75
0.75
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.71
0.71
0.71
0.71
0.71
0.71
0.71
0.71
0.71
0.71
0.71
0.71
0.71
0.71
0.71
0.72
*i.e., 1.34 x 10" WL
45
-------
3
SUMMARY OF WORKING LEVELS (xlO ) CALCULATED
FOR A MOTEL USING GEOTHERMAL WATERS
CONTAINING 360 pCi/1 RADON-222
HOUR AIR CHANGES PER HOUR
0.5 1.0 2.0 3.0 4.0
1
2
3
4
5
6
7
8
9
10
11
12 (noon)
13
14
15
16
17
18
19
20
21
22
23
24
1.67*
1.67
1.68
1.69
1.69
1.69
1.69
1.69
1.69
1.68
1.67
1.66
1.65
1.64
1.64
1.64
1.64
1.64
1.64
1.64
1.65
1.66
1.66
1.67
1.14
1.14
1.14
1.14
1.14
1.14
1.14
1.14
1.14
1.13
1.13
1.12
1.11
1.11
1.11
1.11
1.11
1.11
1.12
1.12
1.12
1.13
1.13
1.13
0.87
0.87
0.87
0.87
0.87
0.87
0.87
0.87
0.87
0.86
0.86
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.86
0.86
0,86
0.86
0.87
0.77
0.78
0.78
0.78
0.78
0.78
0.78
0.77
0.77
0.77
0.77
0.76
0.75
0.76
0.76
0.76
0.76
0.76
0.77
0.77
0.77
0.77
0.77
0.77
0.73
0.73
0.73
0.73
0.73
0.73
0.73
0.73
0.73
0.73
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.73
0.73
0.73
0.73
*i.e., 1.67 x 10~ WL
46
-------
3
SUMMARY OF WORKING LEVELS (xlCf ) CALCULATED
FOR A PRIVATE RESIDENCE USING GEOTHERMAL WATERS
CONTAINING 490 pCi/1 RADON-222
HOUR AIR CHANGES PER HOUR
0.5 1.0 2.0 3.0 4.0
1
2
3
4
5
6
7
8
9
10
11
12 (noon)
13
14
15
16
17
18
19
20
21
22
23
24
1.44*
1.45
1.45
1.45
1.46
1.46
1.46
1.46
1.45
1.44
1.43
1.41
1.40
1.39
1.39
1.39
1.39
1.38
1.39
1.39
1.40
1.41 .
1.42
1.43
1.07
1.07
1.08
1.08
1.08
1.08
1.08
1.07
1.07
1.06
1.05
1.04
1.03
1.03
1.02
1.03
1.03
1.03
1.04
1.04
1.05
1.06
1.06
1.07
0.85
0.86
0.86
0.86
0.86
0.86
0.86
0.86
0.85
0.85
0.84
0.83
0.83
0.82
0.82
0.83
0.83
0.83
0.84
0.84
0.84
0.85
0.85
0.85
0.77
0.77
0.77
0.77
0.77
0.77
0.77
0.77
0.77
0.76
0.76
0.76
0.76
0.76
0.76
0.76
0.76
0.76
0.76
0.74
0.76
0.77
0.77
0.77
0.73
0.73
0.73
0.73
0.73
0.73
0.73
0.73
0.73
0.73
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.72
0.73
0.73
0.73
0.73
0.73
*i.e., 1.44 x 10 WL
47
-------
3
NUMMARY OF WORKING LEVELS (xlO~ ) CALCULATED
FOR AN INDOOR POOL USING GEOTHERMAL WATERS
CONTAINING 2231 pCi/1 RADON-222
HOUR AIR CHANGES PER HOUR
0.5 l.C 2.0 3.0 4.0
1
2
3
4
5
6
7
8
9
10
11
12 (noon)
13
14
15
16
17
18
19
20
21
22
23
24
14.26*
14.16
14.11
14.07
14.05
14.04
14.03
14.03
17.47
22.05
25.27
27.29
28.51
29.25
29.69
29.96
26.68
22.19
19.02
17.04
15.84
15.12
14.68
14.42
5.85
5.85
5.85
5.85
5.85
5.85
5.85
5.85
8.42
10.62
11.57
11.94
12.07
12.12
12.14
12.14
9.58
7.37
6.43
6.07
5.93
5.88
5.87
5.86
2.62
2.62
2.62
2.62
2.62
2.62
2.62
2.62
3.98
4.48
4.56
4.57
4.58
4.58
4.58
4.58
3.21
2.71
2.63
2.62
2.62
2.62
2.62
2.62
1.74
1.74
1.74
1.74
1.74
1.74
1.74
1.74
2.66
2.80
2.81
2.81
2.81
2.81
2.81
2.81
1.89
1.75
1.74
1.74
1.74
1.74
1.74
1.74
1.36
1.36
1.36
1.36
1.36
1.36
1.36
1.36
1.97
2.01
2.01
2.01
2.01
2.01
2.01
2.01
1.4
1.36
1.36
1.36
1.36
1.36
1.36
1.36
*i.e. ,14.26 xT
-------
TECHNICAL REPORT DATA
(Please reaa ..-.strucrions on the reverse before completing)
REPORT NO.
ORP/LV-75-8B
2.
3. RECIPIENT'S ACCESSION NO.
"'T'TRADIOACTIVITY ASSOCIATED WITH GEOTHERMAL WATERS IN TH
WESTERN UNITED STATES - A modeling effort to calculat
working levels from radon-222 and its progency for
REPORT DATE
April 1978
5. PERFORMING ORGANIZATION CODE
Michael F. O'Connell, EPA
Gary A. Gilgan,.University of Nevada - Las Vegas
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Radiation Programs, LVF
P.O. Box 15027
Las Vegas, NV 89114
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Same as above
13. TYPE OF REPORT AND PERIOD COVERED
Technical Note
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
It has been known for some time that geothermal fluids contain a
variety of dissolved minerals including radioactive species, particularly
radium-226 and radon-222. There is an interest in examining radiation
exposures to humans in contact with these fluids or their deposited
minerals. The literature contains a few studies which have evaluated
the ingestion and inhalation of radon and its daughters in situations
associated with the balneological uses of thermal fluids. In this
report, an attempt is made to predict the radon progeny (working levels)
concentrations that could be expected inside structures using geothermal
fluids for domestic hot water and space heating purposes.
A model is developed to calculate the working levels from the heat
load requirements that are necessary to maintain interior conditions
during winter climatic conditions when space heating is at its highest.
Calculations were also included for an indoor pool facility which is
partially heated by the heat loss of the pool water. The results show
that the pool represents the highest potential exposure environment.
Other applications that were included in this analysis included greenhouses,
nT"f "Ua t"g> HTJO 1 1 i npQ anH anayi'mon f* sir\A
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI I'ield/Croup
Geothermal
Radon-222, health effects
Nonelectrical application
of geothermal energy __
Working levelcalcualtion
08D
18H
Heat load calculations
for structures
18. DISTRIBUTION STATEMENT
release unlimited
19. SECURITY CLASS (This Report/
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (Rav. 4-77) PREVIOUS EDITION is OBSOLETE
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