NUREG-0396
EPA 520/1-78-016
PLANNING BASIS FOR THE DEVELOPMENT OF
STATE AND LOCAL GOVERNMENT
RADIOLOGICAL EMERGENCY RESPONSE PLANS
IN SUPPORT OF
LIGHT WATER NUCLEAR POWER PLANTS
A Report Prepared by a
U. S. Nuclear Regulatory Commission and
U. S. Environmental Protection Agency
Task Force on Emergency Planning
DECEMBER 1978
Office of State Programs
Office of Nuclear Reactor Regulation
U. S. Nuclear Regulatory Commission
Office of Radiation Programs
U. S. Environmental Protection Agency
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NUREG-0396
EPA 520/1-78-016
PLANNING BASIS FOR THE DEVELOPMENT OF
STATE AND LOCAL GOVERNMENT
RADIOLOGICAL EMERGENCY RESPONSE PLANS
IN SUPPORT OF
LIGHT WATER NUCLEAR POWER PLANTS
A Report Prepared by a
U. S. Nuclear Regulatory Commission and
U. S. Environmental Protection Agency
Task Force on Emergency Planning
H. E. Collins* B. K. Grimes**
Co-Chairmen of Task Force
F. Galpin***
Senior EPA Representative
Manuscript Completed: November 1978
Date Published: December 1978
*Off ice of State Programs
* "Office of Nuclear Reactor Regulation
U. S. Nuclear Regulatory Commission
Washington, D.C. 20555
***Office of Radiation Programs
U. S. Environmental Protection Agency
Washington, D. C. 20460
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FOREWORD
The purpose of this report is to provide a basis for Federal, State and
local government emergency preparedness organizations to determine the
appropriate degree of emergency response planning efforts in the environs
of nuclear power plants. The report is the product of a Task Force of
NRC and EPA representatives formed in 1976 to address this issue. The
Task Force hopes that the guidance provided here will be used to supplement
the extensive emergency planning guidance already published by NRC and
EPA.
This report introduces the concept of generic Emergency Planning Zones
as a basis for the planning of response actions which would result in
dose savings in the environs of nuclear facilities in the event of a
serious power reactor accident. Application of the Task Force guidance
should result in the development of more uniform emergency plans from
site to site but should not result in a large incremental increase in
the resources required to implement the existing planning elements.
This is particularly true of recently licensed plants where planning
elements have been implemented at substantial distances from reactor
sites.
This report represents a consensus view of the Task Force on the
planning basis guidance and on a number of important Issues related
to emergency planning which were considered in the development of
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the guidance. As of the publication date of this report, these
recommendations had not been formally adopted by the NRC or EPA and
therefore represent only Task Force views. However, the concept of
a generic area in which to plan has received general acceptance by the
variety of groups commenting on drafts of this report. If adopted by
the NRC, the Task Force expects that the key elements of the guidance
would be incorporated in the NRC's primary emergency planning guidance
publication for States and their local governments (NUREG-75/111) and
therefore used by Federal agencies as a part of the basis for concurrence
in State and local government Radiological Emergency Response Plans in
support of power reactor facilities.
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NRC/EPA TASK FORCE
ON
EMERGENCY PLANNING
Membership on the Task Force on Emergency Planning was drawn from both
the United States Nuclear Regulatory Commission and the United States
Environmental Protection Agency and is listed below.
Co-Chairmen
Harold E. Collins, Assistant Director for Emergency Preparedness, Office
of State Programs, NRC
Brian K. Grimes, Assistant Director for Engineering and Projects, Division
of Operating Reactors, Office of Nuclear Reactor Regulation, NRC
Senior EPA Representative
Floyd L. Galpin, Director, Environmental Analysis Division, Office of
Radiation Programs, EPA
Members
*Roger M. Blond, Senior Risk Analyst, Probabilistic Analysis Staff, Office of
Nuclear Regulatory Research, NRC
Harry W. Calley, Chief, Protective Action Planning and Investigation
Branch, Office of Radiation Programs, EPA
Leo B. Higginbotham, Acting Director, Division of Fuel Facilities and
Materials Safety & Inspection, Office of Inspection and Enforcement, NRC
C. Vernon Hodge, Transportation Specialist, Transportation Branch, Office
of Nuclear Material Safety & Safeguards, NRC
Michael T. Jamgochian, Nuclear Engineer, Site Designation Standards Branch,
Office of Standards Development, NRC
Joe Logsdon, Health Physicist, Protective Action Planning and Investigation
Branch, Office of Radiation Programs, EPA
James A. Martin, Reactor Safety Engineer, Accident Analysis Branch, Office
of Nuclear Reactor Regulation, NRC
Jerry Swift, Environmental Engineer (Radiation), Technology Assessment
Division, Office of Radiation Programs, EPA
Consultants to the Task Force
Fredric D. Anderson, Senior Nuclear Safety Engineer, Site Designation
Standards Branch, Office of Standards Development, NRC
Delbert F. Bunch, Director, Program Support Staff, Office of Nuclear
Reactor Regulation, NRC
R. Wayne Houston, Chief, Accident Analysis Branch, Office of Nuclear
Reactor Regulation, NRC
Legal Consultants Acquired by the Task Force
Joseph Scinto, Deputy Director, Hearing Division, Office of Executive Legal
Director, NRC
Royal J. Voegeli, Attorney, Office of the Executive Legal Director, NRC
* Replaced Ian B. Wall, Office of Nuclear Regulatory Research effective
May 15, 1978.
iii
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ACKNOWLEDGEMENT
Two major versions of this Task Force report have been reviewed by
interested Federal agencies, and a limited number of State and
local government emergency preparedness representatives. Many written
comments and suggestions were received on the two major draft versions
and all of the comments were carefully considered in preparing the
final version of this report. The report was significantly improved
as a result of the comments and suggestions.
The Task Force wishes to thank all of those who provided comments and
critiques of the report during the two year period of its development
and in particular the Interorganizational Advisory Committee on
Radiological Emergency Response Planning and Preparedness, of the
Conference of (State) Radiation Control Program Directors.
Members of the committee also included representatives of the National
Association of State Directors for Disaster Preparedness and the U.S.
Civil Defense Council.
iv
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TABLE OF OCMltHTS
I. Introduction 1
Accident Considerations 4
II. Planning Needs 7
III. Rsoonmended Planning Basis 11
Emergency Planning Zones — ^/^ 11
Size of the Emergency Planning Zone —&.fA 15 — r/l*
f C. Time Factors Associated with Releases 18
1 0i^, it
" [D. Radiological Characteristics of Releases 20
IV. Conclusions 24
References 25
Glossary 26
Appendix I - Rationale for the Planning Basis 1-1
A. General Considerations 1-1
B. Consequence Considerations 1-4
1. Design Basis Accidents 1-4
2. Class 9 Accidents 1-6
C. Probability Considerations 1-7
D. Emergency Planning Considerations Derived
from Siting, Meteorological Models, and
Licensing Criteria 1-12
1. Siting 1-12
2. Meteorological Considerations 1-20
3. Licensing Considerations 1-26
E. Emergency Planning Considerations Derived
fron the Reactor Safety StuSy (ttASH-1400) 1-36
F. Examination of Offsite Emergency Protection
Measures for Core Melt Accidents 1-44
References 1-53
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TABLE OF CONTENTS (Ccn't.)
Appendix II - Background Concerning the Report II-l
A. NRC Reactor Siting and Emergency Planning
Regulations II-l
B. Federal Guidance Effort II-3
C. Reactor Accident Considerations II-8
D. Establishment of the Task Force 11-13
References 11-15
Appendix III - Related Issues Considered By
the Task Force III-l
A. Issue: Whether and to what extent, so-
called "Class 9" events having consequences
beyond the most serious design basis
accidents analyzed for siting purposes,
should be considered in developing emergency
plans III-l
B. Issue: Is there a need to plan beyond the
low Population Zone? III-5
C. Issue: Whether there is a conflict between
Protective Action Guides for plums exposures
and dose criteria for siting and design of
nuclear power facilities III-8
D. Issue: Whether the guidance in this document
for offsite emergency planning can be
separated from siting considerations in the
NRC licensing process 111-12
References 111-17
VI
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TABLE OF OONTENTS (Con't.)
List of Tables
Table ft
1. Guidance en Size of the Emergency Planning Zone 17
2. Guidance on Initiation and Duration of Release 20
3. Radionuclides with Significant Contributions to
Dominant Exposure Modes 23
1-1. Relation of Turbulence Types to Weather
Conditions 1-15
1-2. Upper Bound Plume Exposure Pathway Projected
Doses Based on 10 CFR Part 100.11 Values 1-17
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TftBIE OF CONTENTS (Oon't.)
list of Figures
Figure #
1. Concept of Emergency Planning Zones 12
1-1. Dose Falloff with Distance 1-18
1-2. Crosswind versus Downwind Distances 1-21
1-3. Wind Persistence (22 1/2° sector) 1-23
1-4. Wind Persistence (67 1/2° sector) 1-24
1-5. Example of Time-Dose-Distance Relationships
for Worst Case DBA Thyroid Dose (Inhalation) -
Plume Exposure Pathway 1-29
1-6. Thyroid Dose Versus Distance (DBA-HX&) 1-30
1-7. Cumulative Frequency of Thyroid Dose at
10 miles 1-31
1-8. Whole Body Dose Versus Distance (DBA-LOCA) 1-32
1-9. Cumulative Frequency of Whole Body Dose at
10 miles 1-33
1-10. Thyroid Ihgestion Dose Versus Distance 1-35
1-11. Conditional Probability of Whole Body Dose
Versus Distance given Core Melt 1-38
1-12. Conditional Probability of Lung Dose Versus
Distance given Core Melt 1-39
1-13. Conditional Probability of Thyroid Dose Versus
Distance given Core Melt 1-40
1-14. Conditional Probability of Thyroid Ingestim
Dose Versus Distance given Core Melt 1-42
1-15. Conditional Probability of Exceeding PflGs
given PWR "melt-through" releases 1-46
1-16. Conditional Probability of Exceeding PAGs
given PWR "atmospheric" releases 1-46
viil
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TRBIE OF CONTENTS (OOn't.)
List of Figures (Con't.)
Figure #
1-17. Early Fatalities for Selected Protective
Actions- 1-48
1-18. Early Injuries for Selected Protective Actions 1-48
IX
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I. INTRODUCTION
Nuclear facility licensees are required by NRC regulations to develop
emergency response plans^ . Portions of these regulations require
the licensees to coordinate their plans with State and local agencies.
(2 3)
Published Federal guidancev ' ' recommends that State and local
governments formalize their emergency response plans in support of
these facilities to protect public health and safety in the unlikely
event of a significant release of radioactive material from a nuclear
facility to the environment.
Present Federal guidance* suggests the use of a spectrum of accidents as
a basis for developing emergency response plans. For various reasons,*
in 1976 an ad hoc Task Force of the Conference of (State) Radiation
Control Program Directors passed a resolution requesting NRC to "make
a determination of the most severe accident basis for which radiological
emergency response plans should be developed by offsite agencies".
Additionally, the NRC and EPA received other comments from State and
local governments relating to this recommendation.
*See Appendix II.
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In November 1976, a Task Force consisting of NRC and EPA representatives
was convened to address this Conference request and related issues.
The Task Force reviewed what is currently being done in terms of
emergency planning for newly licensed plants and found that substantial
efforts were being made both in on-site and off-site planning. It
also reviewed current guidance from Federal Agencies regarding emergency
(2 3 4)
response planningv * * ' and concluded that adequate guidance was
available or was being developed with regard to the elements of a
plan. While the previous guidance has not precisely specified distances
to which planning elements should be applied, the actual current
application of previous guidance on a case basis during the licensing
process has in practice extended to substantial distances from
reactor sites, i.e., independent of specific Low Population Zone
distances used for siting purposes. However, information regarding
the consequences and characteristics of the accident situation for
which planning was being recommended had not been fully defined.
The Task Force accepts the principle noted in existing NRC and EPA
(2 3)
guidancev * ' that acceptable values for emergency doses to the
public under the actual conditions of a nuclear accident cannot be
predetermined. The emergency actions taken in any individual case
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must be based on the actual conditions that exist and are projected
at the time of an accident. For very serious accidents, predetermined
protective actions would be taken if projected doses, at any place and
time during an actual accident, appeared to be at or above the appli-
cable proposed Protective Action Guides (PAGs), based on information
readily available in the reactor control room, i.e., at predetermined
(A)
emergency action levelsv . Of course, ad hoc actions, based on
plant or environmental measurements, could be taken at any time.
The concept of Protective Action Guides was introduced to radiologi-
cal emergency response planning to assist public health and other
governmental authorities in deciding how much of a radiation hazard
in the environment constitutes a basis for initiating emergency
protective actions. These guides (PAGs) are expressed in units
of radiation dose (rem) and represent trigger or initiation levels,
which warrant pre-selected protective actions for the public if
the projected (future) dose received by an individual in the
absence of a protective action exceeds the PAG. PAGs are defined
or definable for all pathways of radiation exposure to man and
are proposed as guidance to be used as a basis for taking action
to minimize the impact on individuals.
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The nature of PAGs is such that they cannot be used to assure that
a given level of exposure to individuals in the population is
prevented. In any particular response situation, a range of
doses may be experienced, principally depending on the distance
from the point of release. Some of these doses may be well in
excess of the PAG levels and clearly warrant the initiation of
any feasible protective actions. This does not mean, however,
that doses above PAG levels can be prevented or that emergency
response plans should have as their objective preventing doses
above PAG levels. Furthermore, PAGs represent only trigger levels
and are not intended to represent acceptable dose levels. PAGs are
tools to be used as a decision aid in the actual response situation.
Methods for the implementation of Protective Action Guides are an
essential element of emergency planning. These include the pre-
determination of emergency conditions for which planned protective
actions such as shelter and/or evacuation would be implemented
offsite. Details of these methods are being provided as separate
(3 4)
guidancev ' ' and are not included in this report.
Accident Considerations
After considerable discussion, the Task Force concluded that there
was no specific accident sequence that could be isolated as the
one for which to plan, because each accident could have different
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consequences, both in nature and degree. Further, the range of
possible selections for a planning basis is very large, starting
with a zero point of requiring no planning at all because signifi-
cant offsite radiological accident consequences are unlikely to occur,
to planning for the worst physically possible accident regardless
of its extremely low likelihood. As an alternative to attempting
to define a specific accident sequence, the Task Force decided to
identify the bounds of the parameters for which planning is
recommended based upon a knowledge of the potential consequences,
timing, and release characteristics of a spectrum of accidents.
The Task Force recognized that more specific guidance with respect
to accidents whose consequences would be more severe than the design
basis accidents explicitly considered in the licensing process was
appropriate. Additional discussions regarding the need to plan for
consequences of such accidents (commonly known as Class 9 accidents*)
may be found in Appendix III.
The Task Force concluded that the objective of emergency response plans
should be to provide dose savings for a spectrum of accidents that
could produce offsite doses in excess of the PAGs. Although the selected
throughout thTs report, "Class 9 accidents" will refer to those accidents
in which there is melting of the core and/or containment failure.
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planning basis is independent of a specific accident sequence, a number
of accident descriptions were reviewed including the design basis accidents
with various active engineered safety features, and the accident release
categories of the Reactor Safety Study*^ '.
Additional information regarding the rationale for the recommended planning
basis,the background of Federal emergency planning efforts, the Task Force
deliberations on Class 9 accidents, the relationship between emergency
planning and siting criteria, and the difference between PAGs and dose
criteria used for siting can be found in the appendices to this report.
*The Task Force has used information in the RSS as a basis to perform
calculations which illustrate the likelihood of certain offsite dose
levels given a core melt accident. Various aspects of the study have
been debated by reviewers and additional programs are underway to extend
or refine the study. While the RSS is considered by the Task Force to
have limited use in dealing with plant/site specific factors, it provides
the best currently available source of information on the relative
likelihood of large accidental releases of radioactivity given a core
melt event. The results derived from the RSS-based work served to
confirm the Task Force judgment that offsite planning for a generic
distance around nuclear power plants is prudent and useful.
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II. PLANNING NEEDS
The Task Force reviewed the types of information that State and
local governments need to develop emergency response plans and
determined that the information fell into two categories; site
specific and generic. The site specific information such as
population distribution and topography must be available to State
and local officials as part of the planning process. Such informa-
tion is summarized in Environmental Reports and Safety Analysis
Reports prepared by applicants for a permit to construct and
operate a nuclear power facility and is useful for emergency
planning purposes. Some generic information related to the
(2 3 4)
planning effort is already being provided by Federal agencies ' .
The Federal generic guidance provided includes the topics which should
be addressed in an emergency plan^ ' , protective action guides ,
the types of protective action appropriate^ ' and emergency instru-
mentation considerations^ ' ' '.
If it were possible to identify a single accident on which to base
emergency response planning, one could use the release characteristics
of that single accident in connection with site specific characteristics
and other generic information to specify the planning effort. Having
determined that a single specific accident sequence for a light water
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reactor nuclear power plant cannot be identified as a planning basis,
the Task Force chose to provide recommendations in terms of the conse-
quences or characteristics of accidents that would be important in
determining the extent of the planning effort. The planning basis
elements needed to scope the planning effort were determined to be:
1. The distance to which planning for the initiation of
predetermined protective actions is warranted.
2. The time dependent characteristics of potential releases
and exposures.
3. The kinds of radioactive materials that can potentially
be released to the environment.
The most important guidance for planning officials is the distance
from the nuclear facility which defines the area over which planning
for predetermined actions should be'carried out. The other elements
of guidance provide supporting information for planning and preparedness.
The need for specification of distance for the major exposure
pathways is evident. The location of the population for whom actions
may be needed, responsible authorities who would carry out these
actions and the means of communication to these authorities are all
dependent on the size of the planning area.
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Information on the time frames of the accidents is also important.
The time between the initial recognition at the nuclear facility
that a serious accident is in progress and the beginning of the
radioactive release to the surrounding environment is critical in
determining the type of protective actions which are feasible
immediately following an accident. Likewise, knowledge of the
potential duration of release and the time available before
exposures are expected several miles offsite is important in
determining what specific instructions can be given to the public.
A knowledge of kinds of radioactive materials potentially released
is necessary to decide the characteristics of monitoring instru-
mentation, to develop tools for estimating projected doses, and to
identify the most important exposure pathways.
In this report, emergency preparedness is related to two predominant
exposure pathways. They are:
1. Plume exposure pathway — The principal exposure sources from
this pathway are (a) whole body external exposure to gamma
radiation from the plume and from deposited material and
(b) inhalation exposure from the passing radioactive plume.
The time of potential exposure could range from hours to
days.
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2« Ingest ion exposure pathway — The principal exposure from
this pathway would be from ingestion of contaminated water
or foods such as milk or fresh vegetables. The time of
potential exposure could range in length from hours to
months.
The Task Force has provided separate guidance for these two exposure
pathways, although a single emergency plan would include elements
common to assessing or taking protective actions for both pathways.
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III. RECOMMENDED PLANNING BASIS
A. Emergency Planning Zones
With regard to the area over which planning efforts should be
carried out, the Task Force recommends that "Emergency Planning
Zones" (EPZs) about each nuclear facility be defined both for
the short term "plume exposure pathway" and for the longer term
"ingestion exposure pathways." The Emergency Planning Zone
concept is illustrated in figure 1. EPZs are designated as
the areas for which planning is recommended to assure that prompt
and effective actions can be taken to protect the public in the
event of an accident. Responsible government officials should
(2\
apply the applicable planning items listed in NUREG-75/llr '
in the development of radiological emergency response plans.
The following are example planning elements considered appro-
priate for the EPZs:
(1) Identify responsible onsite and offsite emergency response
organizations and the mechanisms for activating their
services,
(2) Establish effective communication networks to promptly
notify cognizant authorities and the public,
(3) Designate pre-determined actions'as
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PLANNING ZONE
EXCLUSION AREA
EXAMPLE
RESPONSE
AREAS
PLUME
TRAVEL
DIRECTION
ro
I
TRANSPORT OF
MILK TO DAIRY
PROCESSING CENTER
Figure 1 Concept of Emergency Planning Zones
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(4) Develop procedures for use by emergency workers,
(5) Identify applicable radiation measurement equipment,
(6) Identify emergency operations centers and alternate
locations, assembly points, and radiation monitoring
locations,
(7) Implement training programs for emergency workers as
appropriate, and
(8) Develop test procedures for emergency response plans.
Emergency planning should predetermine appropriate emergency
responses within the EPZ as a function of population groups,
environmental conditions^ , plant conditions and time
available to respond. For the plume exposure phase, shelter
and/or evacuation would likely be the principal immediate
protective actions to be recommended for the general public
within the EPZ. The ability to best reduce exposure should
determine the appropriate response. The key to effective
planning is good communication to authorities who know what
they are going to do under pre-determined conditions.
For the ingest ion exposure Emergency Planning Zone, the
planning effort involves the identification of major exposure
pathways from contaminated food and water and the associated
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control points and mechanisms. The ingestion pathway exposures
in general would represent a longer term problem, although some early
protective actions to minimize subsequent contamination of milk or
other supplies should be initiated (e.g., put cows on stored feed).
It is expected that judgment of the planner will be used in
determining the precise size and shape of the EPZs considering
local conditions such as demography, topography and land use
characteristics, access routes, jurisdictional boundaries, and
arrangements with the nuclear facility operator for notification
and response assistance.
The EPZ guidance does not change the requirements for emergency
planning, it only sets bounds on the planning problem. The Task
Force does not recommend that massive emergency preparedness programs
be established around all nuclear power stations. The following
examples are given to further clarify the Task Force guidance on
EPZs:
No special local decontamination provisions for the general public
(e.g., blankets, changes of clothing, food, special showers)
No stockpiles of anti-contamination equipment for the general
public
No construction of specially equipped fallout shelters
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No special radiological medical provisions for the general public
No new construction of special public facilities for emergency
use
No special stockpiles of emergency animal feed
No special decontamination equipment for property and equipment
No participation by the general public in test exercises of
emergency plans.
Some capabilities in these areas, of course, already exist under
the general emergency plans of Federal and State agencies.
B. Size of the Emergency Planning Zone
Several possible rationales were considered for establishing the
size of the EPZs. These included risk, probability, cost
effectiveness and accident consequence spectrum. After reviewing
these alternatives, the Task Force chose to base the rationale
on a full spectrum of accidents and corresponding consequences
tempered by probability considerations. These rationales are
discussed more fully in Appendix I.
The Task Force agreed that emergency response plans should be
useful for responding to any accident that would produce offsite
doses in excess of the PAGs. This would include the more severe
design basis accidents and the accident spectrum analyzed in the
RSS. After reviewing the potential consequences associated with
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these types of accidents, it was the concensus of the Task Force
that emergency plans could be based upon a generic distance out
to which predetermined actions would provide dose savings for any
such accidents. Bevond this qeneric distance it was concluded that
actions could be taken on an ad hoc basis using the same considerations
that went into the initial action determinations.
The Task Force judgment on the extent of the Emergency Planning Zone
is derived from the characteristics of design basis and Class 9
accident consequences. Based on the information provided in Appendix
I and the applicable PAGs a radius of about 10 miles was selected
for the plume exposure pathway and a radius of about 50 miles was
selected for the ingestion exposure pathway, as shown in table 1.
Although the radius for the EPZ implies a circular area, the actual
shape would depend upon the characteristics of a particular site.
The circular or other defined area would be for planning whereas
initial response would likely involve only a portion of the total area.
The EPZ recommended is of sufficient size to provide dose savings to
the population in areas where the projected dose from design basis
accidents could be expected to exceed the applicable PAGs under
unfavorable atmospheric conditions. As illustrated in Appendix I,
consequences of less severe Class 9 accidents would not exceed the
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PAG levels outside the recommended EPZ distance. In addition, the
EPZ is of sufficient size to provide for substantial reduction in
early severe health effects (injuries or deaths) in the event of the
more severe Class 9 accidents.
Table 1. Guidance on Size of the Emergency Planning Zone
Accident Phase
Plume Exposure
Pathway
Ingestion Pathway**
Critical Organ and
Exposure Pathway
Whole body (external)
Thyroid (inhalation)
Other organs (inhalation)
Thyroid, whole body,
bone marrow (ingestion)
EPZ Radius
about 10 mile radius*
about 50 mile radius***
* Judgment should be used in adopting this distance based upon considerations
of local conditions such as demography, topography, land characteristics,
access routes, and local jurisdictional boundaries.
** Processing plants for milk produced within the EPZ should be included in
the emergency response plans regardless of their location.
***The recommended size of the ingestion exposure EPZ is based on an expected
revision of milk pathway Protective Action Guides based on FDA-Bureau of
Radiological Health recommendations. The Task Force understands that
measures such as placing dairy cows on stored feed will be recommended
for projected exposure levels as low as about 1.5 rem to the infant
thyroid. Should the current FRC guidelines, 10 rem'8), be maintained,
an EPZ of about 25 miles would achieve the objectives of the Task Force.
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C. Time Factors Associated with Releases
The planning time frames are based on design basis accident
considerations and the results of Cerlculdttws reported in ttve
Reactor Safety Study' '. The guidance cannot be very specific
because of the wide range of time frames associated with the
spectrum of accidents considered. Therefore, it will be
necessary for planners to consider the possible different
time periods between the initiating event and arrival of the
plume and possible time periods of releases in relationship to
time needed to implement protective actions. The Reactor Safety
Study indicates, for example, that major releases may begin in the
range of one-half hour to as much as 30 hours after an initiating
event and that the duration of the releases may range from one-
half hour to several days with the major portion of the release
occurring well within the first day. In addition, significant plume
travel times are associated with the most adverse meteorological
conditions that might result in large potential exposures far
from the site. For example, under poor dispersion conditions
associated with low windspeeds, two hours or more might be required
for the plume to travel a distance of five miles. Higher wind-
speeds would result in shorter travel times but would provide
more dispersion, making high exposures at long distances much
less likely. Therefore, in most cases, significant advance warning
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fl 4)
of high concentrations should be available since NRC regulationsv '
require early notification of offsite authorities for major releases
of radioactive material. The warning time could be somewhat different
for reactors with different containment characteristics than those
analyzed in the Reactor Safety Study. The range of times, however,
is judged suitably representative for the purpose of developing
emergency plans. Shorter release initiation times are typically
associated with design basis events of much smaller potential
consequences or with the more severe Reactor Safety Study accident
sequences.
The planning basis for the time dependence of a release is expressed
as a range of time values in which to implement protective action.
This range of values prior to the start of a major release is of
the order of one-half hour to several hours. The subsequent time
period over which radioactive material may be expected to be released
is of the order of one-half hour {short-term release) to a few days
(continuous release). Table 2 summarizes the Task Force guidance
on the time of the release.
The time available for action is strongly related to the time
consumed in notification that conditions exist that could cause a
major release or that a major release is occurring. Development
and periodic testing of procedures for rapid notification are encouraged.
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Table 2 - Guidance on Initiation and Duration of Release
Time from the Initiating event
to start of atmospheric release
Time period over which radioactive
material may be continuously
released
Time at which major portion of
release may occur
Travel time for release to
exposure point
(time after release)
0.5 hours to one day
0.5 hours to several days
0.5 hours to 1 day after
start of release
5 miles — 0.5 to 2 hours
10 miles — 1 to 4 hours
D. Radiological Characteristics of Releases
To specify the characteristics of monitoring instrumentation,* develop
decisional aids to estimate projected doses, and identify critical
exposure modes, planners will need information on the characteristics
of potential radioactivity releases. For atmospheric releases from
nuclear power facilities, three dominant exposure modes have been
identified. These are (1) whole body (bone marrow) exposure from
external gamma radiation and from ingestion of radioactive material;
(2) thyroid exposure from inhalation or ingestion of radiodines; and
*An Interagency Task Force on Emergency Instrumentation (offsite) is now
preparing guidance^) on the type and quantity of instruments needed
for the various exposure pathways. Federal agencies represented on the
Instrumentation Task Force include NRC, EPA, DCPA, HEW, and DOE.
-------
- 21 -
(3) exposure of other organs (e.g., lung) from inhalation or
ingest ion of radioactive materials. Any of these exposure modes
could dominate (i.e., result in the largest exposures) depending
upon the relative quantities of various isotopes released.
Radioactive materials produced in the operation of nuclear reactors
include fission products and transuranics generated within the
fuel material itself and activation products generated by neutron
exposure of the structural and other materials within and immediately
around the reactor core. The fission products consist of a very
large number of different kinds of isotopes (nuclides), almost all
of which are initially radioactive. The amounts of these fission
products and their potential for escape from their normal places
of confinement represent the dominant potential for consequences
to the public. Radioactive fission products exist in a variety of
physical and chemical forms of varied volatility. Virtually all
activation products and transuranics exist as non-volatile solids.
The characteristics of these materials shows quite clearly that
the potential for releases to the environment decreases dramatically
in this order: (1) gaseous materials; (2) volatile solids; and
(3) non-volatile solids. For this reason, guidance for source
terms representing hypothetical fission product activity within
-------
- 22 -
a nuclear power plant containment structure emphasizes the development
of plans relating to the release of noble gases and of volatiles such
as iodine. However, consideration of particulate materials should not
be completely neglected. For example, capability to determine the
presence or absence of key particulate radionuclides will be needed
to identify requirements for additional resources.
Table 3 provides a list of key radionuclides that might be expected
to be dominant for each exposure pathway. More detailed lists of core
inventories are presented in Chapter 15 of recent Safety Analysis
Reports and in Appendix V of the Reactor Safety Study. Both of these
sources give details on the time histories of the release fractions
for a spectrum of postulated accidents.
-------
Table 3
RADIONUCLIDES WITH SIGNIFICANT CONTRIBUTION TO DOMINANT EXPOSURE MODES
Radionuclides with Significant
Contribution to Thyroid Exposure
Radionuclides with Significant
Contribution to Whole Body Exposure
Radionuclides with Significant
Contribution to Lung Exposure*
(Lung only controlling when
thyroid dose is reduced by iodine
blocking or there is a long delay
prior to releases).
Radionuclide
1-131
1-132
1-133
1-134
1-135
Te-132
Kr-88
Half Life
(days)
8.05
0.0858
0.875
0.0366
.028
3.25
0.117
Radionuclide
1-131
Te-132
Xe-133
1-133
Xe-135
1-135
Cs-134
Kr-88
Cs-137
Half Life
(days)
8.05
3.25
5,28
0.875
0,384
,028
750
0.117
11,000
Radionuclide
1-131
1-132
1-133
1-134
1-135
Cs-134
Kr-88
Cs-137
Ru-106
Te-132
Ce-144
Half Life
(days)
8.05
0.0858
0.875
0.0366
.028 ,
,750 es
0.117 '
11,000
365
3.25
284
*Derived from the more probable Reactor Safety Study fuel melt categories and from postulated design basis
accident releases.
-------
- 24 -
IV. CONCLUSIONS
In summary, the Task Force concludes that:
. A spectrum of accidents (not the source term from a single
accident sequence) should be considered in developing a
basis for emergency planning.
. The establishment of Emergency Planning Zones of about 10
miles for the plume exposure pathway and about 50 miles for
the ingest ion pathway is sufficient to scope the areas in
which planning for the initiation of predetermined protective
action is warranted for any given nuclear power plant.
. The establishment of time frames and radiological characteristics
of releases provides supporting information for planning and
preparedness.
. If previous consideration has been given to the basic planning
(2 3 4)
elements put forth in existing guidance documents^ ' ,
the establishment of Emergency Planning Zones should not
result in large incremental increases in required planning
and preparedness resources.
-------
- 25 -
REFERENCES
1. 10 CFR Part 50, Licensing of Production and Utilization Facility.
Appendix E, U. S. Nuclear Regulatory Commission, Washington, D. C.
2. Guide and Check List for the Development and Evaluation of State
and Local Government Radiological Emergency Response Plans in Support
of Fixed Nuclear Facilities. NUREG-75/111, Dec. 1974, U.S. Nuclear
Regulatory Commission.
3. Manual of Protective Action Guides and Protective Actions for
Nuclear Incidents, EPA-520/1 -75-001. Sept. 1975, U.S. Environmental
Protection Agency.
4. Emergency Planning for Nuclear Power Plants, Regulatory Guide 1.101,
Mar. 1977.U.S. Nuclear Regulatory Commission, Washington, D. C.
5. Reactor Safety Study: An Assessment of Accident Risks in U.S.
Commercial Nuclear Power Plants. (NUREG-75/014), October 1975,
WASH-1400, U.S. Nuclear Regulatory Commission.
6. Instrumentation for Light-Water-Cooled Nuclear Power Plants to Assess
Plant Conditions During and Following an Accident, Regulatory Guide 1.97.
Dec. 1975, U.S. Nuclear Regulatory Commission, Washington, D. C.
7. Interim Guidance on Offsite Radiation Measurement Systems, A Report to
Developers of State Radiological Emergency Response Plans by the
Federal Interagency Task Force on (offsite) Emergency Instrumentation
for Nuclear Incidents at Fixed Facilities, August 1977, U.S. Nuclear
Regulatory Commission, Washington, D. C.
8. Federal Radiation Council Staff Report No. 5, July 1964; Staff Report
No. 7, May 1965.!
9. Federal Response Plan for Peacetime Nuclear Emergencies (Interim Guidance)
April 1977, Federal Preparedness Agency, General Services Administration.
10. Disaster Operations, A Handbook for Local Governments (CPG 1-6) July
1972, & Change No. 1, June 1974, Defense Civil Preparedness Agency.
11. Radiological Incident Emergency Response Planning, Fixed Facilities and
Transportation: Interagency Responsibilities, Federal Preparedness Agency
General Services Administration, Federal Register Notice, Vol. 40,
No. 248 December 24, 1975.
-------
- 26 -
Class 9 Accident
Consequences
Core Melt Accident
GLOSSARY
An accident considered to be so low in
probability as not to require specific
additional provisions in the design of
a reactor facility. Such accidents would
involve sequences of successive failures
more severe than those postulated for
the purpose of establishing the design
basis for protective systems and engineered
safety features. (Class 9 event sequences
include those leading to total core melt
and consequent degradation of the contain-
ment boundary and those leading to gross
fuel clad failure or partial melt with
independent failures of the containment
boundary).
The results or effects (especially projected
dose rates) of a release of radioactive
material to the environment.
A postulated reactor accident in which the
fuel melts because of overheating.
-------
- 27 -
Emergency Planning Zone (EPZ)
Ingestlon Exposure Pathway
Planning Basis
A generic area defined about a nuclear
facility to facilitate emergency planning
offsite. It is defined for the plume and
ingestion exposure pathways. In relation
to emergency response an EPZ is an area in
which best effort is performed making use
of existing emergency plans and is not an
area in which particular criteria must be
met.
The principal exposure from this pathway
would be from ingestion of contaminated
water or foods such as milk or fresh
vegetables. The time of potential
exposure could range in length from
hours* to months.
Guidance in terms of (1) Size of Planning
Area (Distance); (2) Time Dependence of
Release; and (3) Radiological Characteristics
of Releases.
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- 28 -
Plume Exposure Pathway
Projected Dose
Protective Action
Protective Action Guide
Source Term
The principal exposure sources from this
pathway are: (a) whole body external
exposure to gamma radiation from the plume
and from deposited materials and (b)
inhalation exposure from the passing
radioactive plume. The time of potential
exposure could range in length from
hours to days.
An estimate of the radiation dose which
affected population groups could potentially
receive if protective actions are not taken.
An action taken to avoid or reduce a
projected dose. (Sometimes referred to
as protective measure).
Projected absorbed dose to individuals in
the general population which warrants
protective action following a contaminating
event.
Radioisotope inventory of the reactor core,
or radioisotope release to the environment,
often as a function of time.
-------
APPENDIX I
RATIONALE FOR THE PLANNING BASIS
A. General Considerations
The Task Force considered various rationales for establishing
a planning basis; including risk, probability.
cost effectiveness, and consequence spectrum.
After studying the various approaches discussed below, the
Task Force chose to base the rationale for the planning basis
on a spectrum of consequences, tempered by probability consider-
ations.
With respect to the risk* rationale.such an approach would
establish "planning guidance" that could be compared with
the risks associated with non-nuclear accidents. This
rationale would seemingly give a uniform basis for emergency
planning and would clearly indicate the level of risk that
could be mitigated by advanced planning. However, emergency
planning for non-nuclear hazards is not based upon quantified
risk analyses. Risk is not generally thought of in terms of
probaDilities and consequences, rather it is an intuitive feeling
of the threat posed to the public. Reactors are unique in this
regard: radiation tends to be perceived as more dangerous than
other hazards because the nature of radiation effects are less commonly
*Risk is defined as accident consequences times the probability of
accident occurrence.
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1-2
understood and the public generally associates radiation
effects with the fear of nuclear weapons effects. In addition,
a risk-related rationale might imply the determination of an
acceptable level of risk which is outside the scope of the Task
Force effort. Choosing a risk comparable to non-nuclear events,
therefore, was not directly used as the rationale for an emergency
planning basis.
With respect to a probability rationale, one could arrive at
"planning guidance" by selecting an accident probability
below which development of an emergency plan could not be
justified. Factors favoring using this rationale center around
providing a quantitative probability basis, which could be
compared with the probabilities of other types of emergencies
for which plans are prepared.
Factors arguing against the probability rationale are similar
to those against the risk approach. Emergency planning is not
based upon quantified probabilities of incidents or accidents. On
the basis of the accident probabilities presented in the Reactor
Safety Study (nuclear and non-nuclear) society tolerates much more
probable non-nuclear events with similar consequence spectrum*
without any specific Planning. Radiological emergency planning is
not based upon probabilities, but on public perceptions of the
problem and what could be done to protect health and safety. In
essence, it is a matter of prudence rather than necessity.
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1-3
Ageneric "probability of an event" appropriate for planning has
many implications felt to be outside the scope of the Task Force
objective. However, the concept of accident probability is important
and does have a place in terms of evaluatinq the ranae of the
consequences of accident sequences and setting some reasonable
bounds on the planning basis. The probability rationale was used
by the Task Force to gain additional perspective on the planning
basis finally chosen.
With respect to a cost-effectiveness rationale, the level of
emergency planning effort would be based on an analysis of
what it costs to develop different levels of such a plan and
the potential consequences that could be averted by that degree
of development. The factor favoring the cost-effectiveness
rationale is that an emergency plan could be developed on the
basis of cost per potential health effect averted. Factors
arguing against the cost-effectiveness rationale are the dif-
ficulty in arriving at costs of plan development and maintenance
and considerations that general and radiological emergency
response plans have already been developed. In addition,absent
an actual accident, it would be very difficult to assign a dollar
value to the effectiveness of the plan in terms of health effects
averted.
Lastly, the calculated consequences from a spectrum of postulated
accidents was considered as the rationale for the planning basis.
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1-4
Such a rationale could be used to help identify desirable
planning elements and establish bounds on the planning effort.
Further, a planning basis could be easily stated and understood
in terms of the areas or distances, time frames and radio-
logical characteristics that would correspond to the conse-
quences from a range of possible accidents. Consequence oriented
guidance would also provide a consistency and uniformity in
the amount of planning recommended to State and local
governments. The Task Force therefore judged that the conse-
quences of a spectrum of accidents should be the principal
rationale behind the planning basis.
B. Consequence Considerations
The Task Force considered the complete spectrum of accidents
postulated for various purposes, including those discussed
in environmental reports (i.e. best estimate Class 1 through
8 accidents), accidents postulated for purposes of evaluating
plant designs (e.g. the DBA/LOCA), and the spectrum of
accidents assessed by the Reactor Safety Study. The Task Force
concluded that the environmental report discussions (Class 1-8)
were too limited in scope and detail to be useful in emergency
planning.
1. Design Basis Accidents
Under NRC Regulations, the site/reactor design combination must
be such that the consequences of design basis accidents are
-------
1-5
below the plume exposure guidelines of 10 CFR Part 100. The
design basis loss-of-coolant accident (DBA-LOCA) has been
typically the most severe design basis accident in that it
results in the largest calculated offsite doses of any accident
in this class. The DBA-LOCA is not a realistic accident
scenario in that the release magnitudes are much more severe than
would be realistically expected and may exceed that of some core-
melt type accidents. A best estimate assessment of the release
following a LOCA would be significantly smaller than the DBA-LOCA
used for siting purposes. An analysis of this accident has been
performed for most of the power plants licensed or under review
by NRC to determine the dose/distance relationships as computed
by traditionally conservative assumptions used under 10 CFR Part
100 requirements. Results of this study are presented later in
this appendix. The study concluded that the higher PAG plume
exposures of 25 rem (thyroid) and 5 rem (whole body) would not
be exceeded beyond 10 miles for any site analyzed. Even under
the most restrictive PAG plume exposure values of 5 rem to the
thyroid and 1 rem whole body, over 70 percent of the plants would
not require any consideration of emergency responses beyond 10
miles. It should be noted that even for the DBA-LOCA, the lower
range of the plume PAGs would likely not be exceeded outside the
low population zone (LPZ) for average meteorological conditions.
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1-6
For the ingestion pathways, under the same DBA-LOCA conditions,
the downwind range within which a PAG of 1.5 rem thyroid could
be exceeded would be limited to within 50 miles even
under the conservative 10 CFR 100 assumptions. The 50 mile
distance is also justified as a maximum planning distance
because of likely significant wind shifts within this distance
that would further restrict the radius of the spread of radioactive
material.
2. Class 9 Accidents
"Class 9" accidents cover a full spectrum of releases which range
from those accidents which are of the same order as the DBA-LOCA
type of releases; i.e., doses on the order of PAGs within 10 miles;
to those accidents which release significant fractions of the
available radioactive materials in the reactor to the atmosphere,
thus having potential for life-threatening doses. The lower
range of the spectrum would include accidents in which a core
"melt-through" of the containment would occur. As in the DBA-LOCA
class, the doses from "melt-through" releases (involving
thousands of curies) generally would not exceed even the most
restrictive PAG beyond about 10 miles from a power plant. The
upper range of the core-melt accidents is categorized by those
in which the containment catastrophically fails and releases large
quantities of radioactive materials directly to the atmosphere
because of over-pressurization or a steam explosion. These
-------
1-7
accidents have the potential to release very large quantities
(hundreds of millions of curies) of radioactive materials. There
is a full spectrum of releases between the lower and upper range
with all of these releases involving some combination of atmospheric
and melt-through accidents. These very severe accidents have the
potential for causing serious injuries and deaths. Therefore,
emergency response for these conditions must have as its first
priority the reduction of early severe health effects. Studies*6' '
have been performed which indicate tnat if emergency actions sucn
as sheltering or evacuation were taken within about lu miles of a
power plant, there would be significant savings of early injuries
ana deatns from even the most "severe" atmospneric releases.
For the ingestion pathways, (due to the airborne releases and
under Class 9 accident conditions), the downwind range within
which significant contamination could occur would generally be
limited to about 50 miles from a power plant, because of wind
shifts during the release and travel periods. There may also be
conversion of iodine in the atmosphere (for long time periods)
to chemical forms which do not readily enter the ingestion pathway.
Additionally, much of the particulate materials in a cloud would
have been deposited on the ground within about 50 miles.
C. Probability Considerations
An additional perspective can be gained when the planning basis
is considered in terms of the likelihood (probability) of
accidents which could require some emergency response.
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1-8
Probabilities can be used to give a perspective to the
emergency planner by comparing the chance of a reactor accident
to other emergencies for which plans and action may be required.
This consideration forms an additional basis upon which the
Task Force selected the planning basis. The Reactor Safety
Study (RSS) estimated the probabilities* of various severe
accidents occurring at nuclear power plants. The probability of
a loss-of-coolant accident (LOCA) from a large pipe break was
estimated to be approximately one chance in 10,000 (1x10" ) of
occurring per reactor-year. LOCA accidents would not necessarily
lead to the melting of the reactor core since emergency core
cooling systems (ECCS) are designed to protect the core in
such an event. In fact, other accident initiating events such
as the loss-of-coolant accident from a small pipe break or
transient events have a higher chance of leading to core-melting
than do large LOCA accidents. Core-melt type accidents were
calculated to have a probability of about one chance in 20,000
of occurring per reactor-year. There is a significant degree
of uncertainty associated with both of the above probability
estimates.
Use of the RSS probability estimates, in the context of emergency planning,
has been thoroughly examined. It is recognized that there is a large range
of uncertainties in these numbers (as indicated in,the Risk Assessment
Review Group Report, NUREG/CR-0400). but the perspective gained when con-
sidering the probabilities is important in making a rational decision
concerning a basis for emergency planning.
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1-9
The degree of uncertainty is such that no differentiation can
be confidently made, on a probabilistic basis, between the
DBA/LOCA and the releases associated with less severe core-melt
categories.
As discussed in Appendix III, the Task Force has concluded that
both the design basis accidents and less severe core-melt accidents
should be considered when selecting a basis for planning pre-
determined protective actions and that certain features of the
more severe core-melt accidents should be considered in planning
to assure that some capability exists to reduce the consequences
of even the most severe accidents. The low probabilities associated
with core-melt reactor accidents (e.g. one chance in 20,000 or
-5
5 x 10 per reactor-year) are not easy to comprehend and additional
perspectives are useful. Within the nex
-------
1-10
100. To restate this, there is about a 1% chance of emergency
plans being activated in the U.S. beyond the recommended EPZs
within the next few years. For a single State, this probability
drops appreciably. For a State with ten reactors within or
adjacent to its borders, the probability of exceeding PAGs
outside the planning basis radius for the plume exposure pathway
-5
is about 1.5 x 10 x 10 or about one chance in 6000 per year
according to the Reactor Safety Study analysis.
For perspective, a comparison between reactor accidents and
other emergency situations can be made. Considerations of
emergency planning for reactor accidents are quite similar
to many other emergencies; floods, for example, have many
characteristics which are comparable. Timing, response
measures and potential consequences, such as property
damage are similar for both events.
Flood risk analysis has been carried out by the Flood
Insurance Program of the Department of Housing and Urban
Development and the Corps of Engineers. Flood plains have
been designated for all areas of the country by computing
the probability of being flooded within a certain period
of time; ie., the 100-year flood plain designates those
areas which can be expected to be under water when .the worst
flood in a century occurs. Even with this relatively high
probability of severe flood occurrence there are no explicit
requirements for emergency response planning.
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1-11
Hurricanes and tornadoes are two potential threats for which some
emergency planning is required. Approximately 2 hurricanes
per year may be expected to hit the Atlantic coastal States
which require emergency response. For individual States, the
hurricane frequency ranges from 0.01 to 0.65 per year.
Tornadoes have a very high probability of occurrence per year.
A severe tornado can be characterized by wind speeds of
over 200 miles per hour. Such tornadoes are capable of
lifting cars off the ground, tearing roofs and walls
off frame houses, overturning trains, and uprooting or
snapping most trees. Emergency actions would probably be
taken for such tornadoes. The frequency of severe tornadoes
for individual States, ranges from about 0.1 to 4 per year.
Severe reactor accidents are at least 100 times less likely to
occur than these other disasters requiring emergency response.
Me nevertheless believe, that 1t 1s appropriate to develop
flexible emergency response capabilities which will assure that
consequences from nuclear reactor accidents are minimized.
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1-12
D. Emergency Planning Considerations Derived from Siting,
Meteorological Models and Licensing Criteria
1. Siting
As indicated in 10 CFR Part 100 (Siting Criteria),
an applicant for a construction permit to build a nuclear
power plant must designate an exclusion area, a low population
zone (LPZ) and a population center based upon consideration
of population distribution. The exclusion area must be of such.
a size that^an individual located at any point on its boundary
for two hours immediately following the onset of a postulated
design basis accident fission product release from the reactor
plant would not receive a total radiation dose to the whole body
of 25 rem or 300 rem to the thyroid from radioactive plume exposure
The LPZ must be of such a size that an Individual located at any
point on its outer boundary who is exposed to the radioactive
cloud during its entire period (30 days) of passage would not
receive a total radiation dose to the whole body of 25 rem or 300
rem thyroid. Calculated doses are usually substantially less
than these doses. Protective measures are not
assumed to be taken to avoid or mitigate these doses during
the denoted time periods. In addition, site related requirements
are placed on the exclusion area and the LPZ. The licensee must
have authority over all activities within the exclusion area,
which normally requires ownership of the area. There must
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1-13
be a reasonable probability that appropriate protective
measures, Including evacuation, could be taken for the
residents in the LPZ in the event of a serious accident.
Dose guideline values are not given for the population
center, although the expected doses would be less than within the
LPZ. Demographic characteristics within 50 miles of sites
are discussed in detail in Environmental Reports and in
Chapter 2 of Safety Analysis Reports for each nuclear power
plant and in Reference 1.
Assumptions used by the NRC staff to assess conformance
with these regulations are contained in various Regulatory
Guides le.g. Regulatory Guides 1.3 and 1.4) and the NRC staff's
Standard Review Plans for Chapter 15 of Safety Analysis
Reports submitted by applicants for construction permits and
operating licenses. Although various assumptions are utilized
in this guidance, certain common features are shared: systems
containing potentially significant quantities of radio-'
nuclides are postulated to fail for an unspecified reason,
releasing all or substantial fractions of their inventories
from their normal location to the reactor plant containment
structure;* various installed safety systems in the contain-
ment designed to mitigate the consequences of the postulated
release, are assumed to be inoperable at the time of the event,
*In particular, for the worst case DBA/LOCA postulated for contain-
ment design, 100% of the noble gases and 50% of the radioiodines in
the reactbr core are presumed to be released from the core and primary
pressure boundary to the containment, which is assumed to isolate
and leak at a specified volumetric leak rate.
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1-14
or are assumed to be operating in a degraded mode, or combin-
ations thereof; the resulting fractional release to the
atmosphere is assumed to occur at ground level under extremely
unfavorable dispersion conditions, i.e., under conditions
such that the calculated dose for the given fractional release
would not be exceeded more than five percent of the time at the
site under review; and dose models which overestimate the dose
on a plume center line for the given release fraction are used in
the dose calculation. For all of these postulated, simultaneously
occurring circumstances, 10 CFR Part 100 dose guideline values
must not be exceeded at the specified distances from the site.
Perspective on the implications of these 10 CFR 100 reactor
siting criteria for emergency planning can be obtained by
relating the calculated doses to the EPA PAGs, to guidelines
for milk ingestion, and to certain meteorological aspects
of dispersion in the atmosphere. For ground level releases,
without a wind shift, dose decreases with downwind distance (r)
in proportion to r"a, where a_ is between 1.5 and 3, depending on
(2)
the stability class prevailing at the time. '(Stability classes
are measures of atmospheric dispersion and are classified
by the letters A through G, with A denoting extremely dispersive
conditions (see Table 1-1)^). For the NRC staff assumption
conditions (e.g., class F conditions with low wind
-------
Table r-i — RELATION OF TURBULENCE TYPES
TO WEATHER CONDITIONS
A—Extremely unstable conditions D—Neutral conditions*
B—Moderately unstable conditions E—Slightly stable conditions
C—Slightly unstable conditions F— Moderately stable conditions
Nighttime conditions
~ ... . , ,. Thin overcast
0 f . . Daytime insolation
Surface wind - - -
or
speed, m/sec Strong Moderate Slight cloudinesst cloudiness
<2
2
4
6
>6
A
A-B
B
C
C
A-B
B
B-C
C-D
D
B
C
C
D
D
E
D
D
D
F
E
D
D
* Applicable to heavy overcast, day or night.
tThe degree of cloudiness is defined as that fraction of the sky above
the local apparent horizon which is covered by clouds.
REF: flETEOROLOGY AND ATOMIC ENERGY - 1968
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1-16
speed) and for "average" dispersion conditions (e.g., class
D stability), a value of a_= 1.5 provides a qood approxi-
mation for purposes of projecting dose rates with distance
from an exclusion area boundary. Table 1-2 and figure 1-1
illustrate this dose rate decrease. For illustrative purposes,
figure 1-1 also shows the decrease for values of a_ equal to
1 and 2. Except for stability class A, which seldom
occurs, dose rate should decrease with distance within the
1/r and 1/r curves in this figure, barring a significant
wind shift during a release period.
For purposes of this discussion, dose ^s_ distance extrapola-
tions of the exclusion radius dose rate for LWR accidents
are of the greatest interest. Table 1-2 presents projected
upper bound (no wind shift) values of 2 hour whole body and
thyroid doses at various distances given a 25 rem and 300 rem
dose level at an exclusion radius (rQ). For a site with an
exclusion radius of one mile, the upper limits of the proposed
EPA PAGs for plume exposures would be exceeded within 3
miles (whole body PAG) and 5 miles (thyroid PAG) of the reactor
plant containment structure; the lower limits could be exceeded
within 8 miles (whole body) and 15 miles (thyroid) of the reactor
plant containment structure. For a site with an exclusion radius
of 0.5 miles (about the median for currently licensed plants),
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1-17
TABLE 1-2
UPPER BOUND PLUME EXPOSURE PATHWAY
PROJECTED DOSES BASED ON
10 CFR PART 100.11 VALUES
r/rr
1.
1.5
2
3
4
5
6
8
10
15
20
(r/rv)
-1.5
1.
0.54
0.35
0.19
0.13
0.089
0.068
0.044
0.032
0.017
0.011
0 to 2 HR DOSE LIMIT (REM)
Whole Body THYROID
25
14
8.8
4.8
3.3
2.2
1.7
1.1
0.8
0.43
0.28
300
162
105
57
39
27
20
13
9.6
5.2
3.3
ETA
(hrs)
0.5
0.75
1
1.5
2
2.5
3
4
5
7.5
10
NOTES: (1) Dose = Dose commitment on plume center!Ine.
(2)
= Exclusion area boundary, or exclusion radius
for a given site; r/r = multiple of exclusion
radius; lefthand column can be read as miles if
rQ = 1 mile.
(3) Presumes 100% of noble gases and 50$ of radioidines
in core inventory released to containment, constant
volumetric leak rate from containment, "five percentile"
meteorology, straight line of sight travel of the plume,
and conservative dose factors for plume exposure.
(4) ETA = Estimated time of arrival of plume front based on
ro = 1 mile and 2 mph wind speed. Higher wind speeds
reduce travel times and calculated doses.
-------
DOSE FALLOFF WITH DISTANCE
(ALONG ACTUAL PLUME TRACK)
1.0 r-
0.8 -
Relative 0.6
Dose
Rate
0.4 -
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-------
1-19
these limits could be exceeded within half the denoted distances.
Calculated course-of-accident doses could be several times
larger than the above values.
A second perspective from which to peruse the data in table 1-2
is that of the thyroid PAGs for the milk ingestion pathway.
The ratio of thyroid dose commitment factor (related to air
concentration) for the milk pathway to the inhalation (plume
exposure) pathway is of the order of 300 for 1-131.* From
this perspective it is clear that, without a wind shift during
the release period, potential dose commitments via the milk
pathway could exceed the ingestion PAG for tens of
miles from the reactor site for the presumed conditions, given
the presence of dairy herds and pasture in the downwind direc*
tion. Clearly, wherever there is a potential to exceed a
plume exposure PAG for the thyroid, there is a much greater
potential to exceed the milk pathway thyroid PAG. Alternately,
much lower releases of radioiodine could result in projected
doses in excess of the ingestion PAG without there being a
potential to exceed plume exposure PAGs.
*For a core release, 1-131 activity would be about one eighth the total
radioiodine activity. Initially (for a day or so) 1-133 or 1-135
activities would be dominant. Thus, although 1-131 would dominate the
projected dose commitment rate, the key early indicators for monitoring
purposes would be the hard (1-2 MeV) gamma emissions from 1-135.
-------
1-20
2. Meteorological Considerations
Although actual atmospheric diffusion is unlikely to behave
as simple theory would suggest, initial projections of
dose during an incident would most likely be based in part
on the simple, theoretical, gaussian plume model (i.e., Pasquill
diffusion). Shown in figure 1-2 are theoretical "widths" of
gaussian shaped plumes^ ' (the concentration of a pollutant
at the selected width of the plume is about 1% of the center-
line concentration). Travel times of plume fronts for different
wind speeds are also illustrated in figure 1-2. Stability
class, wind speed and wind direction might be considerably
different at the same time at different locations in the vicin-
ity of a site and local topography could significantly influ-
ence wind patterns. Nevertheless, the information displayed
in figure 1-2 could be useful for scoping initial emergency
response actions, especially for those areas within a couple
of miles of a site. For example, for a wind speed of 2
miles per hour and class F stability ( corresponding
roughly to the meteorological conditions assumed for the worst
case (5%) design basis accident considered for purposes of con-
tainment design), a plume front would not arrive at a location
two miles downwind for almost one hour. For this hypothetical
case, given timely warning, and using crosswind travel, an
individual could, barring any obstacles, walk out of the poten-
tially impacted area before the plume front extends to two miles,
-------
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1-22
since the individual would have to travel for about six
minutes to do so. Generally, higher wind speeds result
in lower dose rates for a given release fraction (source
term), but time of arrival of a plume front at a specific
distance is shorter.
In the foregoing, on several occasions note was made of the possible
influence of a wind shift. Clearly, upon a wind shift the
plume exposure dose commitment rate of persons in the original
downwind direction, due to the passage of a plume, would
end, and a different population dose commitment rate would
begin in the new downwind direction.
NOA/r ' has analyzed National Weather Station meteorological
data across the United States and has presented results in
the form of graphical displays of the probability of hours of
wind persistence in 22.5° and 67.5° sectors. (Figure'I-3 and 1-4).
The study concludes that there is an even chance of a sig-
nificant wind shift occurring in the next two to four hours at
any given location in the United States. A few general observations
are of import to emergency planning and/or response:
". . . the higher the wind speed, the greater is
the tendency for the wind to remain in a given direction. Con-
versely, it is in the lowest wind speed categories of calm
and 1 to 5 mph that the least direction persistence is found."
-------
REF. I. VAN DER HOVEN. WIND PERSITENCE PROBABILITY.
ERLTM-ARL-10. NOAA AIR RESOURCES LABORATORY.
SILVER SPRING, MD. 20910
Highest 50-percent probability of hours of wind persistence in a 22^u sector centered on the
indicated direction*-.
ro
Figure I-3.
USNRC 12/75
-------
3.9
4.2'
REF. «. VAN DER HOVEN. WIND PERSISTENCE PROBABILITY.
ERLTM-ARL-10. NOAA AIR RESOURCES LABORATORY.
SILVER SPRING, MD. 20910
Highest 50-percent probability of hours of wind persistence in a 67% sector centered on the indicated
directions.
Figure 1-4.
USNRC 12/75
-------
1-25
and "... wind roses (frequency) that favor a particular
sector will also tend to persist in that sector."
Three caveats to the meteoroloaical discussion are worth noting. The
first has to do with precipitation. Rainfall could occur either at
the time of a radioactive release or some time during transport,
possibly many miles away from the source of the release. Rainfall
is usually a very efficient scavenger of particles in the
atmosphere. Should a radioactive release to the atmosphere
occur during rainfall, one should expect to find relatively
greater ground deposition close to the source of the release,
independent of the height of the release, than one would find
during clear weather. Under rainy conditions, relatively less
air and ground concentrations of radioactive material should
be found at greater distances from the source of the release.
On the other hand, a release could occur during dry weather
yet the release could intercept a rainfall at some distance
away; at this distance particles could be deposited on the
earth, vegetation, structures, water, etc., very efficiently.
In a strong rainfall a substantial fraction of deposited
radioactive material could even be washed away. Rainfall
interception could be the most important meteorological
phenomena of concern for the case of a strongly elevated
release, such as due to plume rise of a thermally hot
release which is probable with larger accidents.
-------
1-26
The second caveat concerns real world meteorology. As noted
earlier, plumes or puffs do not normally follow straight lines,
especially in low wind speed conditions. Nor do they maintain
a constant windspeed and stability. Puffs can double back and
return from where they came and slow down or speed up. Clearly,
the track of a major radioactive release would be of great interest
and concern. As illustrated in Figure 7.15 of reference (3),
radiation signals well above natural background should be observed
even miles away from a plume at the center of which the dose rate
is as low as one rem per hour, and even less. Such plumes could
be tracked using aircraft and generally available instrumentation
such as Geiger counters and "cutie pies."
It is also important to realize that a substantial amount of energy
could be associated with major releases. This energy will tend to
lift the radioactive material off of the ground and form a cloud
or plume. If this occurs, tracking of the material could be much
more difficult since the wind direction can change dramatically
with attitude.
3. Licensing Considerations
NRC regulation require applicants for licenses to construct and
operate nuclear power facilities to make accident dose calculations.
Such calculations take into consideration plant designs and site
characteristics. They are based in part on the DBA-LOCA accident
scenario.
Inherent in the consequence calculations for the postulated
DBA-LOCA is the presumption of "five percentile" meteorology,
i.e., the presumption that atmospheric dispersion at a site
-------
1-27
at the time of the postulated accident should be more favorable
(leading to lower doses) ninety-five percent of the time.
Alternately, given the postulated accident, the odds are at
least twenty to one against the doses being as large as
calculated for the DBA-LOCA. This "five-percentile" meteoro-
logy is derived from measurements made at the site during, or
previous to, the construction period. It can nominally be
characterized by class F stability and very low wind speeds
(e.g., 2 miles/hour or less), i.e., the very conditions
for which a wind shift is most likely. These data are presented
in Chapter 2 of current Safety Analysis Reports for each nuclear
power facility and are given as funcions of elapsed time and
distance.
The results of the conservative licensing calculations for the
DBA-LOCA vary from plant-to-plant because of plant design and
variation in meteorology. For this reason a large number plants
were analyzed in order to report the likely range of the con-
servative DBA-LOCA doses. Data from seventy safety analysis
reports were collected and used for this purpose. The seventy
plants consisted of 129 separate nuclear units. The resulting
distribution of DBA-LOCA doses calculated for these facilities are
indicative of plants that are now operating and plants that will
be operating in the near future.
An example of the results of such calculations is shown in
-------
1-28
figure 1-5. As is seen in the figure, the major portion of the
radioactive material will be released in the first few hours,
after the accident. Fortunately, for release durations of more
than a couple of hours there will be significant wind shifts
and cloud meander (especially associated with the 5% to meteor-
ological conditions postulated). Therefore, for purposes of these
calculations it was assumed that the dose of any individual
would be limited to that of the first two hours after the accident.
The results of the analysis are depicted in figures 1-6 through
1-9. Figure 1-6 shows the 2 hour thyroid dose versus distance
for the 50 percentile and 10 percentile cases. The 50 percentile
curve is the median dose for all 129 units; thus half of the
units had doses less than that indicated and the other half
had greater doses. The 10 percentile curve means that 10% of
the units had doses greater than that indicated. This figure
also shows a rapid decrease in thyroid dose out to almost 10 miles
with a leveling off at greater distances. It shows that at ten
miles, the 2 hour thyroid dose would be typically about 4 rem
and that in a few cases it may exceed 10 rem. Figure^I-7 takes
the same data but plots the dose at 10 miles against the cumulative
frequency of reactor units. It can be seen that the DBA-LOCA
doses were calculated to exceed the lower PAG range for only
30% of the units.
Figure 1-8 and 1-9 provide similar plots for the whole body
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103
10'
DISTANCE (METERS)
Figure 1-5. Example of Time-Dose-Distance Relationships for Thyroid Inhalation Dose
From DBA/LOCA (5% Meteorology and Straightline Plume Trajectory)
-------
1-30
2
iii
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80
70
60
50
40
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DISTANCE (MILES)
30
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I
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I
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I
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I
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APPROX. TIME OF CLOUD ARRIVAL (HOURS)
Figure I-6. Centerline Dose Versus Distance for Licensing Calculation of DBA/LOCA at 2 Hours
Assuming 5 Percentile Meteorology and Straight Line Plume Trajectory.
50% Curve is Median of 67 Actual Site Calculations
10% Curve is Highest 10% of Calculations
-------
r-31
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Figure I-7. Cumulative Frequency of Units Versus Dose at 10 Miles for Licensing Calculation of
DBA/LOCA at 2 Hours Assuming 5 Percentile Meteorology and Straight Line
Trajectory.
-------
1-32
2 HOUR WHOLE BODY DOSE
I
20 30
DISTANCE (MILES)
I
5 10 15
APPROX. TIME OF CLOUD ARRIVAL (HOURS)
20
Figure I-8. Centerline Dose Versus Distance for Licensing Calculation of DBA/LOCA at 2 Hours
Assuming 5 Percentile Meteorology and Straight Line Plume Trajectory.
50% Curve is Median of 67 Actual Site Calculations
10% Curve is Highest 10% of Calculations
-------
1-33
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Figure I-9. Cumulative Frequency of Units Versus Dose at 10 Miles for Licensing Calculation of
DBA/LOCA at 2 Hours Assuming 5 Percentile Meteorology and Straight Line
Trajectory.
-------
1-34
dose case. The results are similar to the thyroid case.
The dose is seen to sharply decrease within 10 miles and to
decrease slowly at greater distances. At 10 miles the
whole body dose for the median plant was about 1/10 of a rem
and very few plants had doses in excess of 1/2 rem whole body.
From these results, the Task Force concluded that about a
10 mile Emergency Planning Zone for the plume exposure pathway
was justified to assure that predetermined actions would be
planned in those areas where PAGs could be exceeded in the
event of a release comparable to a design basis accident.
For the ingestion pathway, figure J-10 was developed showing
a distance relationship of potential dose to an infant's
thyroid from milk consumption. As was done for the plume
exposure, conservative calculational techniques were used to
attempt to bound the results of the ingestion exposure. For
example, the straight line trajectory was used with no credit
taken for wind shifts. All of the assumptions of the Reactor
Safety Study for the calculation of thyroid dose from milk
ingestion were used for this analysis. The results of
-figure 1-10 show that for the DBA-LOCA,ingestion doses above
PAG's are unlikely to occur beyond about 50 miles from power plants,
-------
1-35
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APPROX. TIME OF CLOUD ARRIVAL (HOURS)
Figure 1-10. Maximum Thyroid Dose (Milk Pathway) to Infant Versus Distance, From 1-131,
for DBA/LOCA Assuming Worst Possible Meteorology and Straight Line
Trajectory.
-------
1-36
E. Emergency Planning Consideration Derived from
The Reactor Safety Study (HASH-14QQ)
The Reactor Safety Study (RSS) attempts to provide a detailed
quantitative assessment of the probability and consequences of
"Class 9" accidents. The study concluded that the public risk
from nuclear reactor accidents was dominated by accidents in
which there was substantial damage to the reactor core and
that the probabilities of such accidents were very small.*
Since emergency planners are encouraged to develop response plans
which will be flexible enough to respond to most accident
situations, some understanding of "Class 9" accidents and the
relationships between them and emergency planning is needed.
The Reactor Safety Study developed the mathematical techniques
and data base to provide an understanding of these relationships.
To obtain an appreciation for the distances to which or areas
within which emergency planning might be required, a perspective
on the relative probabilities of certain critical doses as
a function of distance from the power plant for these accidents
*Probability of a "core-melt" accident was estimated to be approxi-
mately 1 in 20,000 (5 x 10"b) per reactor year. There is a
large uncertainty on this number.
-------
1-37
is needed. A set of such curves has been prepared for all
of the RSS accident release categories (figure 1-11). These
curves include both Pressurized and Boiling Water Reactor (PWR
& BWR) accidents. Doses are given for the critical values
for which emergency planners should be concerned. One and
five rem whole body doses correspond to the lower range of the
PAGs; 50 rem whole body corresponds to the dosage at which
early illnesses start to occur; and 200 rem whole body is the
dose at which significant early injuries start to occur. As
can be seen from figure 1-11, core melt accidents can be
severe, but the probability of large doses drops off substanti-
ally at about 10 miles from the reactor. Similar conclusions
can be reached by evaluating the other critical organs of
lung and thyroid shown in figures 1-12 and 1-13, respectively.
For the lung, the doses of 5, 25, 300 and 3000 rem were plotted
as a function of distance and probability of occurence. For
the thyroid, the reference doses of 5, 25, 300 rem, which
correspond to the lower and upper PAG levels, and the guide-
line exposure used for siting purposes are presented.
Given a core melt accident, there is about a 70% chance of
exceeding the PAG doses at 2 miles, a 40% chance at 5 miles,
and a 30% chance at 10 miles from a power plant. That is,
the probability of exceeding PAG doses at 10 miles is 1.5 x 10~5
-------
1-38
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REM
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Figure 1-11. Conditional Probability of Exceeding Whole Body Dose Versus Distance. Probabilities
are Conditional on a Core Melt Accident (5 x 10"5).
Whole body dose calculated includes: external dose to the whole body due to the
passing cloud, exposure to radionuclides on ground, and the dose to the whole body
from inhaled radionuclides.
Dose calculations assumed no protective actions taken, and straight line plume
trajectory.
-------
1-39
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Figure 1-12. Conditional Probability of Exceeding Lung Doses Versus Distance. Probabilities are
Conditional on a Core Melt Accident (5 x 10'5).
Lung dose calculated includes: external dose to the lung due to the passing cloud,
exposure to radionuclides on ground, and the dose to the lung from inhaled
radionuclides within 1 year.
Dose calculations assumed no protective actions taken, and straight line trajectory.
-------
1-40
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Figure 1-13. Conditional Probability of Exceeding Thyroid Doses Versus Distance. Probabilities
are Conditional on a Core Melt Accident (5 x 1Q-5).
Thyroid dose calculated includes: external dose to the thyroid due to the passing
cloud, exposure to radionuclides on ground, and the dose to the thyroid from
inhaled radionuclides.
Dose calculations assumed no protective actions taken, and straight line trajectory.
-------
1-41
per reactor year* (one chance in 50,000 per reactor-year) from
the Reactor Safety Study analysis.
Based in part upon the above information the Task Force judged
that a 10 mile plume EPZ would be appropriate to deal with
core melt accidents.
Potential ingestion doses to the thyroid (through the cow/milk
pathway) from core melt accidents are given in'"figure 1-14.
The distance for which emergency planning is needed is not easily
determined from the information given in the figure. It is
evident that doses can potentially be quite high out to
considerable distances.
The current PAG for milk ingestion is 30 rem thyroid to an
individual and 10 rem thyroid to a suitable sample of the
population (usually calculated on the basis of an infant's
thyroid). Given a core melt accident, there is a near
100% chance of exceeding the 10 rem thyroid PAG from milk
ingestion at 1 mile, about an 80% chance at 10 miles and a 40%
chance at 25 miles from a power plant. A planning basis
for milk ingestion on the order of 25 miles would therefore
approximately correspond to the 10 mile plume exposure distance
*There is a large uncertainty on this number.
-------
1-42
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1000
Figure M4. Conditional Probability of Exceeding Thyroid Dose to an Infant Versus Distance.
Probabilities are Conditional on a Core Melt Accident (5 x 10~5).
Thyroid dose calculated is due solely to radionuclide ingestion through the milk
consumption pathway.
Dose calculations assumed no protective actions taken, and straight line trajectory.
-------
1-43
if current FRC guidance were used. However, because the
Task Force is aware that revision of the FRC guides
may result in recommendations for certain types of pre-
ventive measures (such as putting cows on stored feed)
at projected doses substantially below these levels,*
the Task Force chose an ingestion pathway EPZ on the order
of 50 miles.
*The recommended size of the ingesticn exposure ERZ is based on an expected
revision of milk pathway Protective Action Guidelines by FDA-Bureau of
Radiological Health. The Task Force understands that measures such as
placing dairy cows on stored feed will be recommended for projected
exposure levels as low as about 1.5 rem to the infant thyroid. Should
the current FRC guidelines be maintained,an EPZ of about 25 miles would
be(recommended by the Task Force.
-------
1-44
F. Examination of Off site Emergency Prnt.PrtivP Mpasnres for
Core Melt Accidents
A recent study (6, 7) has been published which is of general
use to those responsible for emergency response planning for
reactor accidents in understanding the "Class 9" accident
relationships and specifically the core "melt-through" and
"atmospheric" accident classes. This study was undertaken to
evaluate, in terms of public radiation exposure and health
effects, the relative merits of possible offsite emergency
protective measures for response to potential nuclear reactor
accidents involving serious reactor accidents. Three types of
protective measures were examined and compared: evacuation;
sheltering followed by population relocation, and medical
(iodine) prophylaxis. This study was based upon the Reactor
Safety Study results and methodologies. The conclusions of
the study not only give a perspective on the relative merits
of £ given protective measure, the conclusions also confirm
the Task Force recommendations on the distances and times
for which planning is appropriate.
-------
1-45
Figures1 "I5 and L16 give the additional perspective of the
study on the probabilities and needs for emergency planning
in terms of the core "melt-through" and "atmospheric" categories
and a range of expected emergency actions. Figure I-ISshows
the probabilities of exceeding thyroid and whole body PAGs
versus distance from the reactor, conditional on the occurrence
of a'Vielt-through" release. The probabilities are calculated
for an individual located outdoors, and are presented for
both lower and upper PAG levels for each organ. A similar curve
is shown in figure I-l&for the"atmospherid1 releases.
The figure indicates that both whole body and thyroid
PAGs are likely to be exceeded at very large distances*
from the reactor (and correspondingly over very large areas)
if an "atmospheric" accident were to occur. Doses in excess
of threshold levels for early health effects are confined to
smaller areas much closer to the reactor. Therefore, in the
unlikely event that an accident of this magnitude were to occur,
responsible authorities might choose to direct their available
*Caution must be used in interpreting the large distances indicated.
The RSS consequence model assumes an invariant wind direction following
the release of radioactive material. However, because of the time
required by the cloud to travel large distances, it is likely that the
wind directions will, in fact, shift and that the predicted dose levels
would not be observed at the reported radial distance. Rather, the
distance applies more closely to the trajectory of the released cloud.
-------
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O)
0.001
10 100
DISTANCE (MILES)
Figure 1-15. Conditional Probability of Exceeding Thyroid and Nhole Body Protective Action
Guides (PAGs) Versus Distance for an Individual Located Outdoors.8
Probabilities are Conditional on a WK "Melt-Through" Release (PHP 6 and 7).
Yielding factor for airborne radionuclides » 1.0. Shielding factor for
radionoclides deposited on ground > 0.7. 1-day exposure to radionuclides on
ground.
bV*iole body (thyroid) dose calculated includes: external dose to the whole
body (thyroid) due to the passing cloud and 1-day exposure to radionuclides
on ground, and the dose to the whole body (thyroid) from inhaled radionuclides
within 1 year.
Figure 1-16. Conditional Probability of Exceeding Thyroid and Whole Body Protective Action
Guides (PAGs) Versus Distance for an Individual Located Outdoors.3 Probabilities
are Conditional on a PHR 'Atmospheric" telease
-------
1-47
resources towards limiting the life- and injury-threatening
doses to individuals in those closer areas. Then, if sufficient
resources are available, protective measures might also be
implemented for individuals at larger distances for whom PAGs
are, or are likely to be, exceeded.
Mean** numbers of projected early fatalities and injuries
within selected radial intervals, conditional on an '^atmos-
pheric" release, are compared for evacuation and sheltering
strategies in figures 1-17 and 1-18. Seven strategies are
included, as defined in the key to these figures. Strategy
1 assumes that no immediate protective actions are taken.
2, 3, and 4 are selected sheltering strategies. Strategies
3 and 4 represent sheltering for regions in which a large
fraction of homes have basements. Effective exposure
durations to ground contamination for these two strategics
are 1 day and 6 hours, respectively. Strategy 2 repre-
sents sheltering for regions in which most homes do not
have basements, with 6 hours of effective exposure to ground
contamination. Strategies 5, 6, and 7 represent evacuation
with 5, 3 and 1 hours of delay time, respectively. The results
presented in ftgures 1-17 and H8 assume a uniform population
density of 100 people per square mile. The corresponding
** The mean refers to the average of 91 stratified weather sequences
-which were used to calculate a frequency distribution of early
public health effects.
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££ QC
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UJ f,.f
gg 30
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Ij^ ^*«
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o. ~— 20
o to
oc <
«I 10
il
S n
i
-
-
-
-
-
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-
i
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3
4
5
6
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Iliii.
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134 5 6 7
-«—-•» —
_
-
_
—
IMP
«k
00
0-5
5-10 10-15
RADIAL INTERVAL (MILES)
15-25
0-5
5-10 10-15
RADIAL INTERVAL (MILES)
15-25
Figure t-17. Mean ttatxc of Ptojected Baily Fatalities Within selected Radial
Intervals for Bracuation and Shelterinj Stcateqiss, Giwen a MR
•Atnuspheric" delease (£Wt 1-5). A Uniform l*pulation tensity
of 100 Persona per Square Nile is Assured.
Figure 1-18. Mean Number of Projected Early Injuries Within Selected Radial
Intervals for evacuation and 3wlterin; Strategies, Given a fW
"Atmospheric- Release |WR 1-5). A Uniform ftmulation Dnv.ity
ot 100 Persons per Square lile is Assured.
Key; b
1, No imnediate protective action, SF's (0.75, 0.33). 1-day exposure
to radionuclides on ground.
2. Sheltering, SF's (0.75, 0-3J), 6-hour exposure to cadionuclides on
ground.
3. Sheltering, SF's (0.5, 0.08), 1-day exposure to radionucUdes on •
ground.
4. Sheltering, SF's (0.5, 0.08), 6-hour exposure to radiomjclvtes on
ground.
5. Evacuation, 5 hour delay tine, 10 MPB.
6. evacuation, 3 hour delay time, 10 «PH.
7. evacuation, 1 hour delay time, 10 WH.
aShielding factors (airborne radionuclides, ground contamination).
bShielding factors for no protective action were chosen to be the sane as for
sheltering in areas where rost homes do not have basements (see reference 6).
1. No imnediate protective action, SF's" (0.75, 0.53), 1-day exposure
to radionuclides on ground.
2. Sheltering, SF's !O.T>, 0.33). 6-hour exposure to radionuclides On
ground.
3. Sheltering, SF's (0.5, 0.08), 1-day exposure to radionuclides on
ground.
4. Sheltering, SF's (0.5, 0.08), 5-hour exposure to raUonuclides on
ground.
5. Evacuation, 5 hour delay time, 10 "PH.
6. Evacuation, 3 hour delay time, 10 WH.
7, evacuation, 1 hour delay time, 10 WH.
Shielding factors (airborne radionucliHes, ground contamination).
"shielding factors for no protective acliin were chosen to he the same a", for
shelterirvi in areas where most hones do not have HiSMient? (see reference f).
-------
1-49
number of projected early fatalities and injuries for any par-
ticular site would depend on the actual population distri-
bution surrounding the site. Nevertheless, the relative com-
parison of numbers for the strategies indicated is nearly
independent of the population distribution within a given
interval.
Several observations can be drawn from the results
presented in figures 1-17 and 1-18. Most early fatalities
resulting from "atmospheric" accidents are projected to
occur within approximately 10 miles of the reactor, while early
injuries are likely out to somewhat larger distances.*
Within 5 miles of the reactor, evacuation appears to be more
effective in reducing the number of early health effects
than sheltering, as long as the delay time and nonparticipating
segment of the population are kept sufficiently small.
This distinction is not as apparent in the 5 to 10 mile
interval. Throughout both of the intervals from 0 to 10 miles,
the importance of a rapid and efficient implementation of
either evacuation or sheltering is evident (small delay
times for evacuation, small ground exposure times for sheltering)
*Projected early fatalities and injuries in the 15 to 25 mile
interval arejiigher than for the 10-15 mile interval because
the interval *is twice as wide.
-------
1-50
Note that evacuation (i.e., removal of population from
hazardous area) with delay times of 1 hour or less will
reduce the projected number early public health effects
to roughly 0 in any radial interval, and will always be
the most effective response measure for a severe accident,
if it can be achieved. In the intervals beyond 10 miles,
there is little apparent distinction between the effective-
ness of evacuation and sheltering strategies in terms of
projected early fatalities or injuries. The mean number of
early fatalities is 0 in both of these intervals, and projected
early injuries, although not 0, are greatly reduced for each
of the protective strategies investigated.
Several important conclusions about the relative effective-
ness of the protective measures examined, the distances to
which or areas within which they might be required, and
the time available for their implementation, were drawn by
the study from the results provided by these analyses. For
the "melt-through" class, projected whole body and thyroid
doses in excess of PAGs for those organs are, for all practical
purposes, confined to areas within 10 miles of the reactor.
Emergency response planning for this type of accident should
therefore be primarily directed towards limiting the dose to
those individuals located within that distance. Evacuation
appears to provide the greatest benefit«of any protective measure.
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I- 51
However, sheltering, particularly in areas where most homes
have basements, also offers substantial benefit* and may in
many cases offer an acceptable alternative to evacuation. Iodine
prophylaxis, if administered in sufficient time, could also
offer substantial reduction in the projected dose to the
thyroid.
'Atmospheric" accidents could result in the occurrence of sig-
nificant numbers of early fatalities and injuries. However, doses
in excess of threshold levels for significant early health
effects (about 200 rem whole body) are generally confined
to areas much closer to the reactor. Therefore, given an
"atmospheric" accident, responsible authorities should concentrate
their immediately available resources on limiting the life-
and injury-threatening doses to individuals in those closer
areas.* Within 5 miles of the reactor, evacuation appears to be
more effective than sheltering in reducing the number of early
health effects, as long as the delay time and nonparticipating
fraction of the population can be kept sufficiently small.
Between 5 and 10 miles, this distinction is not as apparent,
and sheltering in areas where basements are widely available
(followed by rapid relocation) may be as effective as
evacuation with relatively small delay times. For all affected
*Then, when time permits, protective measures might be implemented
for individuals at larger distances for whom PAGs are, or are
likely to be, exceeded.
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1-52
areas within approximately 10 miles of the reactor, the speed
and efficiency with which either evacuation or sheltering
and relocation are implemented strongly influence the number
of projected early health effects. For areas beyond 10 miles,
there is little apparent distinction between the effectiveness
of evacuation and sheltering strategies in terms of projected
early fatalities or injuries. Therefore, although protective
actions may be required for individuals located in areas fur-
ther than 10 miles from the reactor for an "atmospheric"
release, the actual measures used and how rapidly or efficiently
they are implemented, will not strongly influence the number
of projected early health effects.
-------
REFERENCES FOR APPENDIX I
(1) D. Bunch, K. Murphy and J. Reyes.
Demographic Statistics Pertaining to Nuclear Power Reactor
Sites. (Draft) NUREG-0348. USNRC Washington, D. C. 20555
Dec. 1977
(2) D. Bruce Turner. Workbook of Atmospheric Dispersion Estimates.
AP-26. USEPA Office of Air Programs, Research Triangle Park,
NC 27711. 1970 Revision.
(3) USAEC. Meteorology and Atomic Energy - 1968. D. Slade, ed
TID-24190. National Technical Information Service, Springfield, Va.
22151
(4) J. A. Martin, Jr. Doses While Traveling Under Well Established
Plumes. Health Physics Jr. V. 32, n.4, pp. 305-307, April 1977.
(5) I. Van der Hoven. Wind Persistence Probability. ERLTM-ARL-10.
NOAA Air Resources Laboratory, Silver Spring, MD 20910
(6) Aldrich, D. C., Examination of Offsite Radiological Emergency
Protective Measures For Nuclear Reactor Accidents Involving
Core Melt, MIT, Department of Nuclear Engineering, March, 1978.
(7) Aldrich, D. C., et al, "Examination of Offsite Emergency Protective
Measures For Core Melt Accidents," American Nuclear Society Topical
Meeting, Newocrt Beach, Ca., May, 1978. K
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APPENDIX II
BACKGROUND CONCERNING THIS REPORT
The commercial nuclear power industry has expanded greatly in the last
several years and is expected to grow even larger in the years ahead as
more plants go into operation. The industry to date has had an excellent
safety record. The Federal government recognizes this excellent safety
record and the efforts by the nuclear industry to continue to reduce even
further the likelihood of accidents. It also recognizes, however, that
the probability of an accident involving a significant release of radio-
active material, although small, is not zero. It has been and continues
to be Federal policy to adopt a cautious attitude with respect to the
potential of these facilities for the release of radioactive materials
in hazardous quantities. Such emergency situations are the focus of
attention of Federal radiological emergency preparedness activities.
A. NRC Reactor Siting and Emergency Planning Regulations
The U. S. NRC, as the agency with the principal regulatory authority
for the construction and operation of nuclear power plants, has
long recognized that emergencies could arise in the operation of
such plants. One of its regulations, Reactor Site Criteria (10 CFR
Part 100 published in 1962' ') states that a capability for taking
protective measures on behalf of the public in the event of a serious
II-l
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accident should be established within a region called the low
population zone (LPZ) surrounding a nuclear power plant site.
Whether a specific number of people can, for example, be evacuated
from a specific area, or instructed to take shelter, on a timely
basis will depend on many factors such as: egress routes, availa-
bility of sheltering, the scope and extent of advance planning,
and the actual distribution of residents within the area.
In 1970, explicit requirements for plans to cope with emergencies
were published in 10 CFR 50, Appendix E. In accordance with
provisions of the Atomic Energy Act of 1954, these requirements
are directed to applicants who apply for licenses to operate these
facilities rather than to State or local governments. With respect
to a planning basis, NRC regulations in 10 CFR 50, Appendix E, do
not provide explicit guidance as to the character or magnitude of
accidental releases to the environment which should be considered
in the development of nuclear facility or State and local government
emergency plans. The Appendix E regulations also do not include
any explicit references to the low population zone or other
particular geographical areas other than "within and outside
the site boundary". They do, however, require that applicants
for construction permits for these facilities provide sufficient
II-2
-------
information to "assure compatibility of proposed (facility) emergency
plans with facility design features, site layout, and site location
with respect to such considerations as access routes, surrounding
population distributions, and land use".
Neither the NRC nor the other Federal agencies have statutory authority
over State and local governments with respect to emergency planning
related to nuclear facilities. In the regulation of nuclear power
plants, however, NRC requires licensees to develop an emergency
response plan which contains provisions for the protection of the
public. The implementation of any protective actions offsite,
however, is necessarily the responsibility of offsite organizations.
The NRC requires that the licensee develop procedures for notifying
local, State and Federal agencies. NRC also requires that licensees'
emergency plans contain agreements reached with local, State and
Federal agencies which provide for the early warning of the public
and the implementation of any appropriate protective actions.
B. Federal Guidance Effort
The legal authority and responsibility of local, State and Federal
governments for offsite response was recognized when 10 CFR 50,
Appendix E was published. NRC regulations require licensees to
II-3
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incorporate provisions for participation by offsite authorities
or organizations whose assistance may be required in the event of
a radiological emergency in periodic drills to test response plans.
As the NRC staff gained experience with these requirements, it
became concerned with the abilities of State and local governments
to discharge their responsibilities should the need ever arise.
This concern in part gave rise to a Federal Register Notice^ '
which started an Interagency program for providing radiological
emergency response planning guidance and related training to
State and local government organizations. NRC exercises the
lead role in this activity and several Federal Agencies, including
EPA, participate. Guidance has been published by NRC, EPA and other
Federal agencies for use by State and local governments in developing
radiological emergency response plans.
It has been Federal policy to encourage planning for a variety of
radiological consequence situations "within and outside the site
boundary" and the Task Force reemphasizes the necessity for
emergency planners to consider a wide spectrum of situations.
Existing Federal guidance documents are constructive in this
regard. But these documents are not sufficiently definitive as
evidenced by'the continuing dialogue among Federal, State and
II-4
-------
local agencies and licensees on this subject. Existing Federal
guidance which bears on the basis for developing offsite emergency
plans is summarized below.
1. 1970 - "The licensee should give particular attention to
protective measures that may be necessary for individuals
within the low population zone ...n^3^
2. 1974 - The NRC staff's acceptance criteria for preliminary
planning at Preliminary Safety Analysis Report (PSAR) review
stage refers to a basis of "calculated radiological dose
consequences of an airborne release following the most
serious design basis accident."^'
3. 1974 - The NRC's principal guidance document^ for State
and local government emergency planners contains the following
under an introductory heading of "Magnitude of the Accident:"
"The evaluation of sites and plant designs, required testing
programs, and quality assurance for the operation of such
facilities all provide substantial assurance that accidents
with serious consequences to the public health and safety
are not likely to occur. Nevertheless, highly unlikely
sequences of events are postulated and their potential
consequences analyzed by the applicant in the Safety Analysis
Report wtrtcti acuumpantes eauti apTJlicattorrand-by the {NRC-)
II-5
-------
staff in its Safety Evaluation Report for each plant. The
(NRC) considers that it is reasonable, for purposes of
emergency planning relative to nuclear facilities, to
prepare for the potential consequences of accidents of
severity up to and including the most serious design basis
accident analyzed for siting purposes."
..."The (NRC) recognizes that accidents with more severe
potential consequences than design basis accidents can be
hypothesized. However, the probability of such accidents
is exceedingly low. Emergency plans properly designed to
cope with design basis accidents would also provide
significant protection against more severe accidents, since
such plans provide for all of the major elements and functions
of emergency preparedness. An added element of confidence
can be gained, however, if States and local governments
assure that their plans for responding to radiological
emergencies are coordinated with their plans for dealing
with floods, earthquakes, or other disaster situations which
might necessitate large scale displacement of people and the
provision of shelter, food, medical aid, and other emergency
services. Communications, traffic control, evacuation, public
notification and other emergency responses will tend to be
11-6
-------
the same whether or not the emergency involves radiological
considerations. The (Department of Energy's) Radiological
Assistance Program (RAP), the Federal Interagency Radiological
Assistance Plan (IRAP) and other Radiological Emergency
Assistance Plans, which are a part of the Federal capability,
provide significant additional emergency resources in the event
of a serious accident."
This introductory text in the "Guide and Checklist"^
document was written for the express purpose of providing
interpretive guidance to the meaning of the enumerated
checklist elements in this document.
4. 1975 - With respect to evacuation as a protective measure,
applicants are requested to provide "plots showing projected
ground-level doses for stationary individuals, — resulting
from the most serious design basis accident analyzed in the
Safety Analysis Report. These should be based on the same
isotopic release rates to the atmosphere and the same
dispersion model as are acceptable for use in Chapter 15
of the PSAR for the purpose of showing conformance to the
siting dose criteria of 10 CFR Part
II-7
-------
5. 1975 - With respect to the levels at which emergency actions
should be initiated, EPA issued as Agency guidance, portions
of the "Manual of Protective Action Guides and Protective
Actions for Nuclear Incidents" which provided PAGs for plume
exposure and application procedures for these PAGs. '
These bear on the areas or distances for which plans might be
implemented.
6. 1977 - "Planning and implementation of measures to cope with
plant related emergencies outside the site boundary with
particular emphasis on the low population zone should be a
coordinated effort involving the licensee, and local, State,
/p\
and Federal agencies having emergency responsibilities.
C. Reactor Accident Considerations
Current NRC regulatory practice requires that events which may be
anticipated to occur one or more times during the lifetime of a
facility lead to no significant releases of radioactive material
to the environment. No design or mode of operation is, however,
entirely risk free. Despite the efforts made to prevent accidental
releases of significant quantities of radioactive material, the
possibility does in fact exist that such accidents may occur. Each
application for a license is accompanied by a detailed assessment
II-8
-------
of such postulated accidents, and NRC staff performs an independent
evaluation of these accidents before a nuclear facility license is
granted.
The NRC staff has provided guidance to applicants as to the type of
accidents to be considered in the design of nuclear power plants (see
for example, Sections 2.3 and 15 of Regulatory Guide 1.70^ and
particularly Table 15-1 of that guide). The recommended approach
by the NRC staff is to organize the postulated accidents to ensure
that a broad spectrum of events have been considered and then to
categorize the events by type and expected frequency so that only
the limiting (i.e., more severe) cases in each group need to be
quantitatively analyzed.
NRC staff has categorized postulated accidents into four major
groups as follows:
1. Events of moderate frequency (anticipated operational
occurrences) leading to no significant radioactive
releases from the facility.
2. Events of low probability with potential for small
radioactive release from the facility.
II-9
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3. Events of very low probability with potential for large
radioactive releases from the facility and whose consequences
are evaluated to establish the performance requirements
of engineered safety features and to evaluate the accepta-
bility of the reactor site. These events, some of which
assume unlikely failures or fission product releases are
referred to as design basis accidents (DBAs).
4. A fourth group of accidents, the so-called "Class 9"*
accidents, which include any situation not specifically
included in the foregoing groups of events and which
typically are represented by some combination of failures
which lead to coremelting and/or containment failure.
These larger events are generally considered in the
regulatory process by reducing their probability of
occurrence to acceptably low values through design
of the plant and its engineered safety features. This
group includes external events such as severe natural
phenomena as well as accidents initiated within the
*The first three groups have also been divided into eight categories in some
accident assessments. The eight categories plus a "Class 9" category are
defined in the proposed Annex to Appendix D to 10 CFR Part 50 dated
December 1, 1971. (Also listed in NUREG 0099, Regulatory Guide 4.2,
Appendix I).
11-10
-------
facility. Unlike groups 1 through 3, the consequences
of events in group 4, are not specifically analyzed
in most applications.
One design basis accident in the third group routinely considered in
the safety analysis performed by the staff is a loss-of-coolant accident
(LOCA) where it is assumed that a large fission product release from
the containment also occurs. The analysis of this accident is used in
connection with the site suitability evaluations done to establish
compliance with 10 CFR Part 100 of the NRC regulations by comparing
computed accident consequences with exposure guidelines given in the
regulations.
The Task Force considers the events described in NRC Regulatory Guide
1.70 as a useful source of information on the type of events in
groups 1 through 3 above. Each application will have detailed infor-
mation on these possible events, including important plant and site-
specific factors that affect the probability and consequences of
accidents. Safety Analysis Reports submitted by licensees are not
likely to include a discussion of Class 9 accidents. Other documents,
such as the Reactor Safety Study^ \ discuss the Class 9 type
accidents and their consequences. The Task Force believes that
the findings on types of severe accidents reported in WASH-1400
provide a useful supplement to the Safety Analysis Reports in
developing a basis for emergency planning.
11-11
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The current version of NRC Regulatory Guide 1.70 requests applicants
to provide two separate analyses of accident consequences: one using
conservative assumptions to verify that plant design is adequate
and a second using best estimate assumptions. One purpose for the
latter assessment is to illustrate the margins of conservatism used
in designing plant engineered safety features. This provision is
a recent addition and consequently there are few analyses of this
type actually available. Therefore, while the nuclear facility
Safety Analysis Report will contain a great deal of information
on credible accidents and how they are accommodated by design,
there is likely to be little information provided on the expected
consequences of such initiating events.
Best estimate consequences of a number of representative initiating
events are addressed in the staff's environmental impact statements.
The Task Force has reviewed the summary information on accident
consequences provided in connection with these statements and we
conclude that these best estimate analyses are too limited in scope
and detail to be useful in emergency planning. It is apparent,
however, from these analyses as well as from the NRC Regulatory
Guide 1.70 analyses, that best estimate consequences are likely
to be a factor of 10 or so smaller, from the standpoint of
meteorological considerations alone, than the consequences of
11-12
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accidents as typically presented in Safety Analysis Reports and
in NRC staff safety evaluation reports for the purpose of site
and plant design feature evaluation.
D. Establishment of the Task Force
To prepare adequate emergency response procedures, basic information
regarding an accident, such as the time characteristics of an
accident, the radioactive material release characteristics, and
the extent of the area potentially impacted is required. Past
practice has been to use a spectrum of accidents, including
design basis accidents for emergency response planning. These
accidents, however, were developed for the specific purposes of
reactor siting and the design of containment and engineered
safety features. Further, the description of the DBAs in Safety
Analysis Reports does not always contain the information needed
for developing emergency response plans. In addition, since the
publication of the Reactor Safety Study in 1975, there has been
some concern and confusion among State and local goverment
emergency response planning and preparedness organizations
as to how the accidents described in the Reactor Safety Study
relate to emergency planning.
11-13
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As a result of some perceived confusion in how accident analyses
should relate to emergency planning, the Conference of (State)
Radiation Control Program Directors passed a resolution in 1976
requesting NRC to "make a determination of the most severe accident
basis for which radiological emergency response plans should be
developed by offsite agencies." Additionally, the NRC and EPA
received correspondence from a few States, and local governments
in this regard.
In response to this dialogue, a Task Force consisting of NRC and
EPA representatives was assembled to address this Conference request
and related issues in November 1976. The Task Force interpreted
the request as a charge to provide a clearer definition of the types
of radiological accidents for which States and local governments
should plan and develop preparedness programs.
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Appendix II
REFERENCES
1. Title 10 Code of Federal Regulations, Part 100 Reactor Site
Criteria.
2. Radiological Incident Emergency Response Planning. Fixed
Facilities and Transportation: Interagency ResponsYBTTTties
Federal Preparedness Agency, General Services Administration'
Federal Register Notice, Vol. 40, No. 248, December 24, 1975.'
3- "Guides to the Preparation of Emergency Plans for Production and
Utilization Facilities. December 1970. U. S. Atomic Energy
Commission. '
4. "Standard Review Plan for the Review of Safety Analysis Reports for
Nuclear Power Plants." Section 13.3 - Emergency Planning, NUREG 75/087
September 1975, U. S. Nuclear Regulatory Commission.
5. Guide and Check List for the Development and Evaluation of State and
Local Government Radiological Emergency Response Plans in Support of
Fixed Nuclear Facilities. NUREG 75/111, Dec. 1974, II. 9. Nuclear
Regulatory Commission.
6- "Standard Format and Content of Safety Analysis Reports for Nuclear
Power Plants, LUR jgnion." section l5.3 - Emergpnry Panning. NUREG
75/094 (Rev. 2), September 1975, U. S. Nuclear Regulatory Commission.
7. Manual of Protective Action Guides and Protective Actions for Nuclear
Incidents, EPA-520/1-75-D01. September. 1975, u. s. Frnnrr»nmoPf:Q
Protection Agency.
8. "Emergency Planning for Nuclear Power Plants." Regulatory Guide 1.101
Rev. 1, March 1977. ~~ " *
9. "Standard Format and Content of Safety Analysis Reports for Nuclear
Power Plants LWR Edition." Regulatory Guide 1.70, RPV. ? September
7975, U. S. Nuclear Regulatory Commission.
10. Reactor Safety Study: An Assessment of Accident Risks in U S
Commercial Nuclear Power nants. (NUREG-75/014), (WASH-1 Ann)
October 19/5, U. S. Nuclear Regulatory Commission.
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APPENDIX III
RELATED ISSUES CONSIDERED BY THE TASK FORCE
Certain issues related to providing a more definitive planning basis
were considered by the Task Force. These issues were examined in
the light of existing Federal guidance and particularly in light of
guidance promulgated by the former AEC regulatory arm (Now the NRC).
There are four principal issues:
A. Issue: Whether and to what extent, so-called "Class 9"
events having consequences beyond the most serious design
basis accidents analyzed for siting purposes, should be
considered in developing emergency plans.
Commentary:
The Task Force believes that States should be encouraged
to develop a breadth, versatility and flexibility in
emergency response preparations and capabilities - and
that some consideration of Class 9 events in emergency
planning is consistent with this view. Further, the
potential consequences of improbable but nevertheless
severe power reactor accidents, while comparable in some
sense to severe natural or man-made disasters which
would trigger an ultimate protective measure such as
III-l
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evacuation, do require some specialized planning considerations.
We do not suggest that these specialized planning considerations
are or ought to be excessively burdensome. Rather, we recommend
that they be considered and developed as a matter of prudence.
The Task Force recognized from the start that there is no
specific design basis accident or Class 9 accident scenario
which can be isolated as the one for which to plan because
each such accident would have different consequences, both
in nature and degree. It is for this reason that NRC and EPA
have encouraged State and local agencies to concentrate
their efforts on devising response preparations and capa-
bilities that are versatile and that also take into account
the unique aspects of radiological accidents.
The Reactor Safety Study (RSS)^ provides a detailed
assessment of the probability and consequences of Class 9
accidents. Various aspects of that study have been debated
by reviewers. Additional programs are underway to extend
or refine the study. It should be noted that the RSS is
based on an analysis of two specific reactors, and the
consequences presented are based on a spectrum of data
compiled from many sites. The report therefore is of
limited use in dealing with plant/site specific factors.
III-2
-------
Nonetheless, the RSS provides the best currently available
source of information on this subject.
The Task Force had to decide whether to place reliance on
general emergency plans for coping with the events of
Class 9 accidents for emergency planning purposes, or
whether to recommend developing specific plans and organi-
zational capabilities to contend with such accidents.
The Task Force believes that it is not appropriate to
develop specific plans for the most severe and most
improbable Class 9 events. The Task Force, however,
does believe that consideration should be given to
the characteristics of Class 9 events in judging whether
emergency plans based primarily on smaller accidents
can be expanded to cope with larger events. This is
a means of providing flexibility of response capability
and at the same time giving reasonable assurance that
some capability exists to minimize the impacts of even
the most severe accidents.
For example, if we are dealing with a very large release
of radioactive material, the principal goal is to prevent
serious adverse health effects to individuals. The measures
required to minimize health effects and to cope with
secondary effects of a large accidental release (such as
III-3
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land or water contamination, and the housing and feeding
of any people required to be relocated for substantial
time periods) would, in all likelihood, require the
involvement of Federal agencies in addition to State
and local governments.
The planning basis recommended by the Task Force therefore
includes some of the key characteristics of very large
releases to assure that site specific capabilities could
be effectively augmented with general emergency preparedness
(response) resources of the Federal government should the
need arise.
NRC and other Federal agency emergency planning guidance
has perhaps been misinterpreted as reflecting a position
that no consideration should be given to so-called Class 9
accidents for emergency planning purposes. The Task Force,
after considering the published guidance and available
documentation/ " ' concludes that Class 9 accidents
have been given some consideration in emergency planning.
It has been, and continues to be the Federal position that
it is possible (but exceedingly improbable) that accidents
could occur calling for additional resources beyond those
that are identified in specific emergency plans developed
111-4
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to support specific Individual nuclear facilities. Further,
the NRC and Federal position has been and continues to be,
that as in other disaster situations, additional resources
would be mobilized by State and Federal agencies.
ll--thgrg__a_nee-d to. P^n beyond the Low Population Zone?
Commentary
The Low Population Zone (LPZ) is determined in accordance with
the requirements of NRC Reactor Siting Criteria, 10 CFR Part
(5)
100V ' . While the consequences of postulated design basis
accidents would be expected to be substantially lower than
the guideline values of 10 CFR Part 100, there are three
reasons why some planning beyond the LPZ is useful:
First, if an accidental release were as severe as the design
basis releases analyzed for purposes of 10 CFR Part 100,
doses could be above the Protective Action Guide (PAG)^
levels beyond the LPZ. In this instance, the responsible
officials should take reasonable and practical measures
to reduce exposures to individuals beyond the LPZ.
III-5
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Second, the deposition of radioactivity, and its subsequent
uptake in foodstuffs such as milk products could be significant
beyond the LPZ even if the plume exposure pathway doses did not
exceed the PAG level at the LPZ outer boundary, because of
the reconcentration of certain radionuclides in the food
chain. Emergency protective measures in that situation
should be taken to minimize exposures from the food chain
via the ingest ion pathway.
Third, there is a very small probability that releases larger
than those from design basis accidents used in evaluating the
acceptability of the reactor stte could occur which could
have consequences substantially in excess of the PAG levels
outside the LPZ outer boundary. As discussed in Issue "A"
the Task Force concluded that such larger accidents should
be considered in developing the basis on which emergency
plans are developed.
The Task Force considered these factors in establishing the
size of the emergency planning zone. Two basic options were
considered. One option was to develop site specific guidance
based on the low population zone (LPZ) with some modifications
to better assure that actions could be extended beyond the LPZ
if needed. The second option was the concept of a planning
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area completely independent of the LPZ. The Task Force
recognized that the LPZ is included in NRC regulations for
siting of nuclear facilities, and is closely connected
to design basis accident consequences. We also recognized
that actual emergency response actions would be based on
proposed Protective Action Guides. Given these factors,
the Task Force concluded that the concept of Emergency
Planning Zones (EPZs) around each nuclear power facility
would best serve to scope the desired spectrum of situations
for which emergency planning should be accomplished. EPZs
for both the "plume exposure pathway" and the "ingestion
exposure pathway" are proposed. The separation of this
concept from NRC siting considerations is discussed in
Issue 0.
While the Task Force recognizes that there are site-to-site
variations in LPZs, due in part to varying features of the
plant, the Task Force concluded that the size of the EPZs
need not be site specific. The principal reason for this
is that the size of the LPZ is determined primarily by the
type and extent of engineered safety features installed in
the reactor plant and their response to design basis accidents.
The loss of either some or all engineered safety features are
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postulated in Class 9 accidents. If the engineered safety
features are lost during an accident, then the LPZ has no
meaning with regard to the size of the areas around the
plant in which emergency response would be appropriate.
A principal aim in establishing EPZs is to foster a breadth,
versatility and flexibility in response preparation and
capabilities in a systematic manner. From the standpoint
of general emergency planning guidance, emergency planning
needs seem to be best served by adopting uniform Emergency
Planning Zones for initial planning studies for all light
water reactors.
c- Issue: Whether there is a conflict between Protective Action
Guides for plume exposures and dose criteria for siting and
design of nuclear power facilities.
Commentary
The Reactor Site Criteria (10 CFR Part 100) require that an
applicant identify an area surrounding a nuclear power reactor,
defined as a Low Population Zone (LPZ). The consequences of
the most severe "design basis accidents" analyzed for siting
purposes should not result in exposures in excess of 300 rem
to the thyroid from radioiodine exposure or 25 ren? to the whole
body for an individual located at any point on the outer
boundary of the Low Population Zone (LPZ).
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Protective action guides (PAGs) for plume exposure have been
provided to State and local government agencies for use as
EPA agency guidance in developing State and local government
radioTogical emergency response plans for areas around
nuclear facilities. One might reasonably ask whether it
is inconsistent for the Federal government to recommend
the development of plans to implement protective actions
at projected dose levels lower than the projected doses
associated with siting criteria. The discussion that
follows reviews this issue.
The dose guideline values in 10 CFR Part 100 do not constitute
acceptable limits for emergency doses to the public under
accident conditions. The numerical values of 25 rem whole
body and 300 rem thyroid can be considered values above
which prevention of serious health effects would be the
paramount concern. Good health physics practice would
indicate that radiological exposures of these magnitudes
should not be allowed to take place if reasonable and
practical measures can prevent such exposures.
The assumptions used for siting purposes in calculating
the doses that could result from design basis accidents
are conservative. The actual doses that would result
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from releases postulated to occur from a design basis
accident therefore would be expected to be much lower
than the dose guidelines of 10 CFR Part 100 under most
meteorological conditions. The inhalation and direct
exposure doses from the releases postulated for design
basis accidents are not likely to exceed the PAG levels
beyond the LPZ under average meteorological conditions.
It has been, however, the NRC's position that a spectrum
of postulated conditions be considered in emergency planning
including adverse meteorological conditions.
Protective Action Guides were devised for purposes of dose
savings and are defined as the projected absorbed dose to
individuals in the general population that warrants protective
action following a contaminating event. Emergency response
plans should include them as trigger values to aid in decisions
to implement protective actions, and responsible officials
should plan to implement protective actions if projected
doses exceed the PAGs. The PAGs, which have numerical values
smaller than the 10 CFR Part 100 guidelines*, are decision
*The PAGs for the plume exposure pathway are expressed as a
range of 1 to 5 rem whole body dose and 5 to 25 rem thyroid
dose to individuals in the population. PAGs for the ingestion
exposure pathway have no parallel in the 10 CFR Part 100
guidelines.
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aids in devising best efforts, considering existing
constraints. They have been set at levels below those
that would produce detectable short term biological effects
and at levels that would minimize long term biological
effects. In the event of an accident they should be
considered as criteria against which available options
for various types of emergency actions can be weighed.
Officials responsible for implementing the protective
actions must take into account constraints that exist
at the time and use professional judgment in determining
the actions appropriate to protect the public.
The nature of PAGs is such that they cannot be used to
assure that a given exposure to individuals in the
population is prevented. In any particular response
situation, a range of doses will be projected, principally
depending on the distance from the point of the radioactive
release. Some of these projected doses may be well in
excess of PAG levels and clearly warrant the initiation
of any feasible protective actions. This does not mean,
however, that doses above PAG levels can be prevented,
or that emergency response plans should have as their
objective preventing exposures above PAG levels. Furthermore,
PAGs represent only trigger levels and are not intended to
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represent acceptable dose levels. PAGs are tools to be used
as a decision aid in the actual response situation.
As discussed above, PAGs and Part 100 dose guidelines
serve distinctly separate functions. The concept of
Emergency Planning Zones (EPZs) introduced in this report
is an attempt to provide guidance on the areas for which
offsite officials should be prepared to make judgments using
the PAGs, to initiate predetermined actions.
D. Issue: Whether the guidance in this document for offsite
emergency planning can be separated from siting considerations
in the NRC licensing process.
Commentary
The NRC siting criteria as related to accidental releases
of radioactivity are given in 10 CFR Part 100 of the
Federal regulations, and are supplemented by the Statement
of Considerations published with this regulation in 1962
and in various regulatory guides and standard review plans
used by the NRC staff. These criteria are used'in the
review of applications for nuclear power plant construction
permits, operating licenses and operating license amendments.
The evaluation performed under 10 CFR 100 primarily involves;
(1) assuring that possible effects of all relevant natural
and man-made phenomena on the nuclear facility have been
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identified and expressed as design conditions for the
facility, (2) determining that adequate engineered safety
features have been provided to assure that postulated
releases of radioactivity resulting from design basis
accidents will not lead to radiological exposures that are
in excess of the numerical guidelines of 10 CFR Part 100
at specified offsite locations> even under adverse
meteorological conditions, (3) evaluating the distance
to the nearest densely populated area to allow calculation
of the offsite location at which certain of the Part 100
exposure guidelines must be met, and {4} evaluating the
general current and projected population density around
the proposed facility out to about 30 miles. The first
three evaluation areas are reexamined at the operating
license review stage and occasionally over the plant
lifetime as facility or site conditions change. The
fourth area (population density) is only evaluated in a
prospective manner to assure the use of low population
density'sites when such are available and is generally
not reexamined. The objective of the evaluations performed
during the Part 100 siting review is to assure that the
risk from any accident (including a Class 9 accident) is
low.
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The definition of the Low Population Zone (LPZ) in 10 CFR
Part 100 states that it is an area which contains residents,
the total number and density of which are such that there
is a reasonable probability that protective measures could
he taken, in their behalf in the event of serious accident.
The outer boundary of the LPZ is one of the locations at
which Part 100 exposure guidelines must be met. The outer
boundary of the LPZ must also be less than a fixed fraction
of the distance to the nearest boundary of a densely populated
center containing more than about 25,000 residents. These
are not in practice siting constraints because restrictions
on the 2 hour exposure from design basis accidents at the
site (exclusion area) boundary generally provide ample time
to take action within a few miles to cope with postulated
design basis releases and because additional engineered
safety features could be added to the facility design, at
some additional cost, to allow the outer boundary of the
LPZ to be as small as the site boundary.
The current NRC staff evaluation of emergency plans for a
particular facility is substantially independent of the
siting criteria. The staff review includes facility
emergency plans and plans for at least the offsite area
referred to in 10 CFR Part 100 as the Low Population
. 111-14
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Zone (LPZ) and in current licensing reviews often extends
to substantially longer distances, particularly for the
ingestion pathway. Emergency plans are reviewed by the
NRC staff during the construction permit and operating
license review stages and audited during the plant lifetime.
Emergency offsite response to large accidents may be less
effective for sites located in an area of general high
population density. Such sites, which may have adequate
engineered safety features to meet the explicit criteria
of 10 CFR Part 100, tend to be eliminated by the NRC staff
guidelines on the general population density around
prospective sites.
We recognize that there would be a reduction in exposures
through the emergency response of the facility staff and
local authorities even without planning. This is based on
experience in coping with more common emergencies such
as those associated with large chemical releases or dam
failures. It seems reasonable that some additional
reduction in exposures may be obtained by certain planning
activities related to emergency preparedness at any
site. However, the reduction in exposures from planned
actions would be difficult to take into account in a
quantitative or qualitative way in siting reviews.
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In view of the above we conclude that although there is
an indirect relationship between siting and emergency
planning, the two can and should be considered separately
in the NRC licensing process. Some clarification of the
NRC regulations may be desirable to make clear the separation
of these issues in the licensing process.
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Appendix III
REFERENCES
1• Radiological Incident Emergency Response Planning, Fixed Facilities
and^ Transportation: Tnteragency Responsibilities, Federal Preparedness
Agency General Services Administration, Federal Register Notice,
Vol. 40, No. 248, December 24, 1975.
2. Reactor Safety Study: An Assessment of Accident Risks In U. S.
Commercial Nuclear Power Plants, (NUREG-75/014fT"6ctober 1975,
HASH-1400. U. S. Nuclear Regulatory Commission.
3. Disaster Operations, A Handbook for Local Governments (CPG 1-6)
July 1972, & Change NoT 1, June 1974. Defense Civil Preparedness
Agency.
4. Federal Response Plan for Peacetime Nuclear Emergencies (Interim
Guidance) April 1977, Federal Preparedness Agency, General Services
Administration.
5. Title 10, Code of Federal Regulations, Part 100. Reactor Site
Criteria.
6. Manual of Protective Action Guides and Protective Actions for
Nuclear Incidents. EPA-520/1-75-001, September, 1975, U. S.—
Environmental Protection Agency.
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7. AUTHORS, F. L. Gal pin. EPA - Office of Radiation Programing
H. E. Collins, NRC - Office of State Programs
ft. K. Grimes, NRP. - DffiVp nf Nnr1oar
NRC FORM 335
(7 77)
U.S. NUCLEAR REGULATORY COMMISSION
BIBLIOGRAPHIC DATA SHEET
4. TITLE AND SUBTITLE (Add Volume No., if appropriate)
PLANNING BASIS FOR THE DEVELOPMENT OF STATE AND LOCAL
GOVERNMENT RADIOLOGICAL EMERGENCY RESPONSE PLANS IN
SUPPORT OF LIGHT WATER NUCLEAR POWER PLANTS
' "" ''•'•••• -
1. HEPORT NUMBER (A«/<*»•
20. SECURITY CLASS (Th,spage)
21 NO. Of PACil
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