-------
(1) evacuation,
(2) respiratory protection,
(3) shelter,
(A) prophylaxis (thyroid protection), and
(5) controlled access.
Restorative actions would then include:
(1) reentry first by survey and decontamination teams,
(2) removal of respiratory protection,
(3) exit from shelters,
(4) stepping prophylactic measures, and
(5) allowing free access by the population.
Exposure through the food chain may be either short term or
chronic depending on the characteristics and half-lives of the
radionuclides involved. Control of this pathway of exposure would
be by:
(1) control of access to contaminated animal feeds,
(2) decontamination of certain foodstuffs,
(3) diversion and storage to allow decay of short half-life
radionuclides, and
(4) destruction of contaminated foods.
Exposure from materials deposited on the ground might also be
either short term or chronic depending on the radionuclides involved,
Protective actions would include:
1.6
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(1) evacuation, and
(2) controlled access.
Since the problem for ground contamination involves an increase
in background levels, denial of access might continue for extended
periods of time. Decontamination may then be the only action which
will allow free access to and utilization of contaminated areas within
a short time. Restorative actions would be reentry, decontamination,
and lifting of controls.
The PAGs are to provide standardized criteria for selecting
predetermined actions at the sacrifice of some flexibility in
balancing the risk of health effects versus the effects of protective
actions during an emergency. The loss of flexibility in response is
expected to be within the limits of accuracy of determining the
factors involved. The loss of flexibility is also offset by the
advantage of being able to respond to the immediacy of the risks in
the case of an emergency.
The range of PAG values allows consideration for local constraints
during planning for implementation. PAGs should be assigned for each
site to assure that local constraints are properly introduced.
1.3 Protective Action Decision Making
A nuclear incident as defined herein refers to a series of events
leading to the release of radioactive materials into the environment of
sufficient magnitude to warrant consideration of protective actions.
Protective actions are those actions taken following a nuclear incident
1.7
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that are intendad to minimize the radiation exposure of the general
public resulting from incidents.
The decision to initiate a protective action may be a complex
process with the benefits of taking the action being weighed against
the risks and constraints involved in taking the action. In addition,
the decision will likely be made under difficult emergency conditions,
probably with .little detailed information available. Therefore,
considerable planning is necessary to reduce to manageable levels the
types of decisions leading to effective responses to protect the
public in the event of a nuclear incident.
1.3.1 Action Factors
Within the context of nuclear incidents, a wide variety of
possible situations may develop. Some perspective of the needs of the
responsible planning officer can be shown in a brief description of
the factors involved. Basically, the officer must balance problems
involving identification of the magnitude of the release, possible
pathways to the population at risk, how much time is available to take
action, what action to take, and what the effects might be.
1.3.2 Incident Determinations
The first problem to arise will be that of identifying the type of
incident and the magnitude of the release. Nuclear incidents may be
extremely variable and may range from very small releases having no
measurable consequences offsite to large scale releases possibly
involving lar^e populations and areas. Responses must be appropriate
to the incident reported.
l.i
-------
One of the variables will be the source term, which refers to
the characteristics and release rate of the radioactive material.
The amounts and types of radionuclides available for release should
be immediately calculable by site personnel. What is actually being
released to the environment can be estimated but may not be confirmed
for some time after the incident.
The magnitude and duration of the release may be estimated by
site personnel from plant conditions or from knowledge of the type
of incident that has occurred. However, the estimate may be highly
uncertain and must be updated on the basis of onsite and offsite
monitoring observations and operational status of engineered safeguards,
If source term information is not available immediately, default
values should be available from planning efforts. These values could
be based on accident scenarios from WASH-1400 (1), design basis acci-
dents evaluated in the NRC safety evaluation report for individual
facilities, or other scenarios appropriate for a specific facility.
The second major variable will be where the released material is
expected to go. Meteorology and geography will affect this variable.
Current meteorological conditions can be observed directly at the site
and relevant locations. However, complete meteorological data will
never be available, and extension of observed data must be made to
predict the course of released material.
Current weather conditions may restrict the options for response,
e.g., evacuation in a blizzard may be reduced or impossible. Weather
1.9
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forecasts have all of the inherent uncertainty of the current condition
estimates since they are derived from these.
Geography is important both in its influence on meteorology and
on demography and in its influence on value judgments to be made.
The planning for a coastal site or a river valley site may be different
due to road patterns and methods for communicating or applying protec-
tive actions.
Demography is a variable to be considered during the planning
stage. Demography is of most importance in helping to assess the
possible impact of an incident. Population numbers, age distribution,
distribution within an area, etc., will have some influence on responses
available in any situation.
Providing for the ability to detect and measure a release are
important factors for planning. Although it may be possible to detect
releases and measure release rates at the site, information from environ-
mental measurements will be needed to confirm any estimates made on the
basis of onslte measurements. Detection and measurement at locations
offsite are necessary to update and/or confirm predictions about the
movement of the release in the environment. Locations for installed
equipment must be planned, probably on the basis of average area
meteorology. Instrumentation needs are discussed in more detail in
Appendix A.
The source term, meteorology, and geography parameters are
utilized in making a prediction of the path and time profile for the
1.10
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release. This prediction, in combination with demography data, will
be used to select the best responses for the situation. The most
reasonable approach is to plan path and time profiles (isopleths)
for unit release situations and then to modify them as real data
are obtained.
1.3.3 Exposure Pathways
The next decision after the determination of an accident situa-
tion will probably concern identification of important pathways of
radionuclides to the population. Exposure pathways of immediate
importance and the time available to interrupt them can be decided
to a large extent on the basis of planning judgments.
The single most important pathway during the emergency phase
is probably by air. The air pathway will be via inhalation of
either gases or particulates and whole body exposure to the plume.
Released gases will be either radioactive noble gases, organic
iodides, inorganic iodides, or volatile inorganic materials. Par-
ticles will probably form by the condensation of vaporized material.
Water is a pathway for exposure by ingestion or immersion. Re-
leased material may enter the water directly or in the form of fallout
or rainout followed by surface runoff. The immersion pathway of
exposure is unlikely to have significance except in very specialized
circumstances. Ingestion of water is probably only a minor pathway
1.11
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of exposure in the short run. However, the gastrointestinal system
must be considered for longer term ingestion of contaminated drinking
water.
Ingesticn of food is an important exposure pathway. However,
with the possible exception of drinking water, milk, and contaminated
leafy vegetables, entry of released materials into food and passage
along this pathway is delayed. Identification of sensitive points
for control should be made during planning.
Characterization of release materials involved in air, water,
and food pathways will not be done for some time after an accident.
The initial decisions will have to be made on the basis of estimates
developed in. planning and modified as real information becomes
available.
Direct external whole body radiation exposure may be a hazard.
Released material deposited in soil or water or suspended in air and
material still at the site serve as sources of direct radiation, mostly
by gamma and beta radiations. Although exposure rate may be measured
directly at specific locations, the distribution must be estimated and
the estimates updated on the basis of monitoring data. Fairly complete-
monitoring will be needed during implementation of restorative actions.
Soil contamination, in addition to providing part of the direct
whol* body exposure, also provides a contribution to the air pathway.
Released material deposited on soil can be resuspended, thus possibly
1.12
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entering the air, water, and food pathways. Evaluation of these
hazards will be particularly important in deciding appropriate
actions during the restoration phase, e.g., level of decontamination
needed.
1.3.4 Populations at Risk
The next consideration of importance to the responsible official
is what population is to be protected. Prior judgment and planning
based on the geography and demography of the area around the site
and on critical pathways are essential to identifying populations
at greatest risk.
The avtrage population is made up of persons with varying
sensitivities to radiation exposure, and responses may be keyed to
the most sensitive, or responses may be restricted, depending on
characteristics of the local population.
(1) For purposes of response planning, the general population
will be evaluated on the basis of risk to individuals within
the population, usually on the basis of avoiding clinical
effects. However, the population as a whole will also be
considered in planning some responses on the basis of
statistical risk of somatic and/or genetic effects.
(2) Sensitive populations may be considered on a special basis.
Children, including the fetus and unborn children, are
generally more sensitive than healthy adults. For this
reapon, such members of the population may be selected
1.13
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either as the most sensitive receptors or as a special
group for protection.
(3) Selected populations will also be present. These
populations may be selected on voluntary or involuntary
bases. Workers at a nuclear facility are classified
as radiation workers and fall under different criteria for
protection than the general population. Those persons who
are engaged in public service activities during or after
the accident are voluntarily placing themselves under
different criteria for protection than the general popula-
tion. Finally, some persons are involuntarily included
under different criteria because the risk of taking action
is different than for the general population. This
involuntarily selected population may include bedridden
and critically ill patients, patients in intensive care
units, prisoners, etc.
1.3.5 Radiation Effects
A final parameter which must be considered is radiation effects.
These may fall into two categories, early or delayed, but are not
mutually exclusive.
(1) Early (acute) effects, occurring within 90 days, may include
fatalities, symptoms of radiation sickness, or clinically
detectable changes. Efforts to protect selected populations
will extend to prevention of fatalities, minimization of
1.14
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symptoms of radiation sickness in radiation workers and
public service personnel, and prevention of clinically
detectable changes of uncertain significance in the rest
of rhe population. The basis for decisions regarding early
effects is not hard to justify because of the imminence
of such effects. However, they must be made rapidly under
conditions of competing needs to protect the public.
(2) Delayad statistical effects (i.e., biological effects which
can only be observed on a statistical basis) will occur
at random in a population after exposure to released
materials. These effects may be fatalities or disabilities
of somatic or genetic origin. The incidence of these
effects is estimated on the basis of statistical evaluation
of epidemiological studies in groups of people who had been
exposed to radiation. Decisions concerning statistical
effects ori populations will be more difficult because
of the lack of immediacy of the effects. But in the long
run, these effects might cause the greatest impact on the
general population.
The response times, actions to consider, and possible health
effects for each pathway are shown in table 1.2 for a typical population.
Effects on animals, vegetation, or real estate are also possible
but may be controlled or alleviated to the extent that decontamination
Is employed or that destruction of the affected items is employed.
1.15
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Table 1.2 Action and Health Effects
Versus Exposure Pathways
Exposure Response
Pathway Time
Air - Particulate Min - Hr
Gas Min - Hr
Water - Particulate
Rainout Hr - Da
Fallout Min - Hr
Immersion Day
Food - Milk Da
Drinking Water Hr
Beverages Da
Foodstuffs Da
Mo
Mo
Mo
Mo
Soil - Resuspension Da
Direct Min - Da
Direct - Facility Min
Air Min - Hr
Water Hr
Action
Available
P
P
P
P
PSR
PSR
PiiR
P&R
P&R
R
P&F
P&R
P
P&R
Public
Health
Effects
D
F,E,D
D
D
D,F,E
D
D
D
D
D
E,D,F
F,S,D
F,E5D
D,F,E
Actions: ? - Protective R - Restorative
Effects: F - Rapid Fatality E - Early D - Delayed
1.16
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\.'t KiMyviiiiHr I'bin Arl Ion Times
A typical sequence of events tor developing emergency plans nnd
responding to nuclear incidents is shown in figure 1.1. This figure
illustrates the general order of events but not relative lengths of
time for each event. These will vary according to individual circum-
stances.
.1 Preparation of Plans
Considerable preparation will be required to ensure the adequacy
of emergency response plans. This preparatory time includes the
following elements:
(1) The decision must be made to prepare emergency response plans
according to the legislative mandates or needs within a
given State.
(2) Then basic plans should be developed using appropriate
guidance from this manual and the AEG "Guide and Checklist" (2)
These plans should include emergency response actions for
coping with nuclear incidents and directions on the use of
EPA Protective Action Guides for these situations.
(3) These plans should be approved by responsible persons or
agencies.
(4) Scenarios must be developed from the basic plans to cover
major contingencies which can be identified.
Methods of implementation must be prepared and tested so that
nonviable responses and contingency plans may be identified and dis-
carded. This discarding of nonviable responses may be based in part
1.17
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RESPONSE
PLANNING
Oe
pr
ge
NUCLEAR
INCIC
Develop emergency response
plan
i
Prepare equipment,
train personnel
and test plan
Review of
plan
1
)ENT
R ESPONSE
EMERGENCY
Preliminary evalu-
ation of inc
idcnt
and projected doses
\
f
cision to Acceptance
epare emer- Of
ncy response pian
plan
Cl) Notification tiroe
fO\ Daennnfa +"ima
Activate
emerge
Notify
author
(
i
PROTECTION
RESTORATION
Field monitoring and continuing evaluation
of exposure pathways, population at risk, dose
projections, PAGs, and protective actions
State
ncy plan
i
DrTttfl r* +• i \l& a/* ¥ -i r\r\ Aafi e- -J rvw
Protective Action Restorative
Initiated Implemented Action
'
ities
4)
—
(11
CD
._
(Z) _
Radiation
returns tc
guide leve
—
' Projected Dose time
^^
>
Is
Implementation time
Time before population exposure
(Ideally protective actions would be implemented during this time.)
Possible accumulation of projected dose before initiation of protective action
Partial accumulation and partial avoidance of projected dose
Time in which projected dose is avoided by protective action
Partial accumul-ation of projected dose during restoration
FIGURE 1,1 SEQUENCE OF EVENTS FOR RESPONSE PLANNING
AND RESPONDING TO NUCLEAR INCIDENTS
-------
on evaluation of local constraints. For example, evacuation of
prisoners or critically ill persons might not be considered viable
while alternative protective actions may be at least partially
effective.
Development of the basic emergency response plan may run a course
of several months or longer. However, planning should be a continuing
activity after the basic plans are developed. Advances in meteorology,
development of new protective actions, changing demography, etc.,
should be used in reevaluation of the original scenarios. And of
course, recurrent testing of implementation methods should be carried
out.
1.4.2 Implementation of Plans
A sequence of steps to implement a response plan following a
nuclear incident is also shown in figure 1.1. The time after an in-
cident may be divided into three phases which are called emergency,
protection, and restoration. These phases are not necessarily distinct
consecutive time periods, but they do serve to indicate the general
nature of activities in a typical response sequence.
The emergency phase includes all those activities leading to
initiation of protective actions. This phase involves assessment of
the situations and is characterized by urgency in determining the need
for protective action and getting the action initiated. In general,
this may be considered to be the first few hours following notification
of an incident and deals primarily with protection of the population
1.19
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from exposure to the airborne plume.
The most important step in emergency response is the prompt
notification that an incident has occurred that could result in an
offsite exposure such that there is a need for initiating protective
action. It is the facility operator's responsibility to notify State
or local authorities that such an incident has occurred. It is
important that agreements be reached during the planning phase on
who is to be notified, data to be provided, offsite measurements that
will be made, and actions to be initiated at the site so that there
will be a minimum time loss in starting implementation of protective
action in the offsite area. Proper planning must include incentives
to prevent delays in notification. Nuclear facility operators have
the initial responsibility for accident assessment. This includes
prompt action necessary to evaluate public health and safety both
onslte and offsite (2). Ideally, this notification should occur as
soon as conditions in the facility are such that an impending accidental
release potential exists. While such notification could lead to false
alarms on rare occasions, they could also permit more timely protective
actions than postponing the notification until a release has occurred.
The sequence of events during the emergency phase includes the
notification of responsible authorities, evaluation and recommendations
for action, and warning of the public. In this early phase of response,
the time available for effective action will probably be quite limited.
As part of their plans, the State should establish with the facility
operator a strict protocol for notification of the State such that early
responding of possible impending releases would not involve disincentives
to the facility operator.
1.20
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Immediately upon becoming aware that an incident has occurred
that may result in exposure of the offsite population, a preliminary
evaluation should be made by the facility operator to determine
the nature and potential magnitude of the incident. This evaluation,
if possible, should determine potential exposure pathways, population
at risk, and projected doses. At this time, projected doses may be
estimated froir. monitoring data at the point of radionuclide release
or from releases anticipated for particular types of nuclear incidents.
The incident evaluation information should then be presented to the
proper authorities. If authorities were notified earlier and have
mobilized resources, protective actions can be started immediately in
predesignated areas or in the areas indicated by projected dose based
on facility operator information. In the absence of detailed informa-
tion from the facility operator as indicated above, the emergency plans
should provide for action in the immediate downwind area of the facility
based on notification that a substantial release has occurred or that
plant conditions are such that a substantial release potential exists.
The next step is to gather additional information on radiation
levels in the environment, meteorology, and environmental conditions.
Further actions or modifications to actions already taken should be
based on these data and Protective Action Guides considering constraints
discussed in section 1.6 of this chapter.
The State should continue to seek information on radionuclide
releases and environmental monitoring data. In fact, an evaluation of
1.21
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such information, as well as exposure pathways, population at risk,
dose projections, and PAGs should be a continuing activity in
both the emergency and protection phases in order to modify pro-
tective actions as needed.
The protection phase begins with the initiation of protective
action and continues until that action is terminated. Figure 1.1
indicates that ideally the protective action such as evacuation would
be implemented before any population exposure. However, the action
may not be initiated in time to avoid all of the projected dose,
and some dose may be received during implementation of the action.
The restoration phase includes those actions taken to restore
conditions to "normal". Restorative actions include the halting of
protective actions, the lifting of restrictions, and possible decon-
tamination procedures.
1.5 Types of Action
The action taken may be, as previously indicated, either protec-
tive or restorative. It may also be voluntary or involuntary, or no
action at all may be taken.
(1) No action would usually be taken by State authorities if
the risk of undesirable radiation effects is anticipated to
be much less than the risk of taking action.
(2) Voluntary action may be suggested for the population at
risk, or it may be taken by them anyway on the basis of
public information provided during an accident situation.
Voluntary action may be valid in the gray area where the
1.22
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risk of exposure to released material and the risk of taking
action are not too different. It may also be taken at
lower levels of exposure by individuals to alleviate their
fears. The negative aspects of possible confusion and
possible panic where incomplete knowledge exists must be
considered during decisions to implement protective actions.
(3) Involuntary (mandatory) action by State authorities should
be implemented when the risk of undesirable effects exceeds
the risk of taking action to such an extent that public
well-being can be adversely affected. This is when action
must be taken in the public interest.
The types of action which can be taken include:
(1) Protective actions, such as evacuation, taking shelter in
homes or civil defense shelters, controlling food and water
distribution, prophylaxis (e.g., thyroid protection), or
individual protective actions (e.g., gas masks, protective
clothing, etc.); and
(2) Restorative action where everything is returned to "normal".
This action includes lifting restrictions or halting
activities initiated as protective actions. It also
includes decontamination where necessary.
The actions to be taken should be evaluated and set in priority or
sequence with identification of ranges for appropriate action and of
decision points during planning. Based on prior judgment of which
1.23
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actions may be effective in any given situation, scenarios can be
prepared which will indicate which actions or mix of actions are
appropriate for various situations.
1.6 Goals of Protective Action
The ideal goal of protective action in an emergency is complete
protection of the endangered population. However, various constraints
may prevent attaining this ideal, so a more realistic goal is minimi-
zation of harmful effects.
In the case of an emergency involving a radiological hazard,
efforts are directed towards minimizing:
(1) early somatic effects such as death within days or develop-
ment of extensive symptoms of radiation sickness;
(2) delayed somatic effects, such as increased probability
of death due to radiation related cancer; and
(3) genetic effects such as increased prenatal mortality or
increased probability of hereditary defects in future
generations.
The minimization of effects implies that the radiation exposure under
consideration is an avoidable exposure. However, for purposes of
determining whether to take a protective action on the basis of
projected dose from an airborne plume, the projected dose should not
include unavoidable dose that has been received prior to the time the
dose projection is done. If a situation should occur where the unavoidable
dose would bo very large as compared to the avoidable dose, different
protective actions might be warranted.
1.24
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1.6.1 Balancing Factors to Achieve Protection Goals
The ideal goal is maximum protection of the public with the
least cost and disruption. Within the need to protect the public
several constraints, including physical, social, and fiscal, will
be operating.
The planner should balance the cost of not taking action (risk
of radiation exposure) against the cost of taking action from both
fiscal and societal aspects. In particular, the fiscal costs of
preparing for action, as well as the costs of all actions to be taken,
should be balanced against the need for response to protect the public,
Also, the societal costs such as panic and disruption of life style
should be balanced against the risk to society of not taking action.
This balancing of costs and risks will place constraints on the
options available for action. This balancing also implies that in
planning, certain cut-off points can be identified, e.g., a marginal
increase ip protection probably may not justify the required expendi-
tures or extensive disruption of families or daily activities.
These costs and constraints should be evaluated in planning by the
responsible public officials in determining the responses to be made
in a given situation.
Even if the balance of costs indicates that a response or set
of actions is reasonable, other constraints may preclude their use.
These additional constraints on action are primarily physical in
nature (e.g., in the case of a puff release, exposure time may be
too short to allow effective protective action).
1 .25
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1.6.2 Constraints on Goal Attainment
The constraints which operate to prevent attaining the ideal
goal include those of environmental, demographic, temporal, resource
availability, and exposure duration.
Environmental constraints will include meteorologic and
geographic considerations. Protective action options ir.ay be restric-
ted by severe weather conditions, windstorms, blizzards, tornadoes,
large accumulations of snow, etc. Options are also restricted by
numbers, types and directions of roads, and obstruction of easy
egress from a site by rivers, mountains, or other geologic formations.
Options are further constrained by the density and distribution
of population, the total size of the population involved, the age
and health status of segments of the population, and other demographic
considerations.
Temporal constraints will be present during all phases of
protective action and some situations during restorative action. Time
available for action may be a real constraint for evacuation of
close-in populations, particularly in the case of short term (puff)
releases. After an incident, exposures of the population close to the
site may occur before control of the situation is established. Even
after a decision for action has been made, notification of the population
and implementation of the action may require enough time such that sub-
stantial exposures occur. The constraint of time in restorative action
will probably be more related to reduction of costs rather than to
direct protection of the population. Rapid decontamination to allow
1.26
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access to utilities, food stores, crops, etc., will reduce the total
cost due t" the accident.
Resources will be one of the largest constraints on viable
options fo . action. The best planning will fail if the resources
to implement actions are not available. Resources needed are
fiscal, manpower, and property, although fiscal will probably be
the limiting factor. Given sufficient fiscal investment, then
manpower, equipment, and training, all will be available in adequate
quantities. However, since only limited amounts of fiscal support
may be available, the lack of equipment and manpower with sufficient
training ana practice in implementation of protective actions will
limit the numbsr of viable options for protecting the public.
In general, as the population to be protected increases, less
protection is available for the same total cost (equal levels of
protection require greater fiscal investment in large populations
than in small populations). Likewise, as the level of preparedness
increases, the cost of obtaining and maintaining this preparedness
increases. The cost of protective action, however, will probably be
a step function. Each decision to take an action or extend an action
will cause an incremental step increase in the cost. All of these
constraints Jiust be considered in planning operations so that the
optimum projection of the public can be obtained with the least
expenditure, both social and fiscal, commensurate with the goal of
protective action.
1.27
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1.6.3 Evaluation of ^Constraints
Local officials involved in developing emergency response plans
must be thoroughly informed on what protective actions are available
for limiting the radiation exposure of the general public during a
nuclear incident. These actions are a vital part of the emergency
response plan and should be specified during the planning phase
rather than at the time of the incident. There are, however, local
constraints associated with each protective action which will influence
the decision to implement a given protective action. The local planner
must also be familiar with and apply these constraints to any emergency
situation. Ideally, it should be possible to balance these constraints
in some analytical fashion which would place each constraint in its
proper perspective on a common scale. Since many of the constraints
cannot be quantified, local planners must use rational, subjective
judgment in evaluating them.
Tables 1.3 and .1.4 list protective actions that are available
for various types of reactor incidents as a function of approximate
time periods following the incident, and the following discussion
attempts to evaluate constraints such as costs, time, societal con-
siderations, etc., that relate to each protective action. This infor-
mation should be valuable to the local planner in making the value
judgments that are necessary to plan actions during an emergency-
1.6.3.1 Constraints on Evacua* ion
While evacuation may seem to be the protective action of choice
following a nuclear incident at a fixed nuclear facility, constraints
1.28
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Table 1.3 Protective and Restorative Actions for Nuclear-
Incidents Resulting in Airborne Releases
Nuclear Incident
(a)
Puff Release -Gaseous
or Gaseous and
Particulate
Continuous Release
Gaseous or Gaseous
and Particulate
Protection Phase
Approximate Time of Initation
0-4 hr.
1,2,3,4,5
1,2,3,4,5
4-8 hr.
3,4,5
1,2,3,4,5
> 8 hr.
3,4,5,6,
7,8
1,2,3,4,
5,6,7,8
Restoration
9,10,11
9,10,11
1 Evacuation
2 Shelter
3 Access control
4 Respiratory protection for
emergency workers
5 Thyroid protection for emergency
workers
6 Pasture control
7 Milk control
8 Food and water control
9 Lift protection controls
10 Reentry
11 Decontamination
(a)
(b)
(c)
Puff release - less than
2 hours
Continuous release -
2 hours or more
Restoration phase may begin
at any time as appropriate
1.29
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Table 1.4 Initiation Times for Protective Actions
Approximate
Initiation Time
0-4 hours
4-48 hours
2-14 days
Exposure Pathway
inhalation of gases or
parti culates
direct radiation
milk
harvested fruits and
vegetable
drinking water
unharvested produce
harvested produce
milk
drinking water
Action to be Initiated
evacuation, shelter, access control, respiratory
prctcct.icn, [.vcphylc :',<, (thyroid proftction)
evacuation, shelter, access control
take cows off pasture, prevent cows from drinkin
surface water, quarantine contaminated milk
wash all produce, or impound produce
cut off contaminated supplies, substitute from
other sources
delay harvest until approved
substitute uncontaminated produce
discard or divert to stored products, such as
cheese
filter, demineralize
LO
O
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associated with a specific site could render the evacuation ineffective
or undesirable. Other optional protective actions such as taking
shelter should be considered. The planner must take into consideration
all local constraints to determine whether or not evacuation is a
viable protective action for the given situation. Examples of the
effects of constraints could be provided on a general basis. However,
it remains the responsibility of the planner to determine the most
reasonable protective actions for each site.
A. Effectiveness of Evacuation
The effectiveness of evacuation in limiting radiation dose is
a function of the- time required to evacuate. If a radioactive cloud
is present, the dose will increase with the time of exposure; if the
evacuation is completed before the cloud arrives, then evacuation
is obviously 100 percent effective. Anything that delays an evacuation
is therefore a constraint, and such constraints are likely to be very
much a function of local site conditions and planning. The planner
should be aware of these constraints in order to minimize their
impact, thus maximizing the effectiveness of the evacuation.
The evacuation time, T(EV), at a particular site is defined as
the time from the start of the nuclear incident to the time when evacuees
have cleared the affected areas. It may be expressed as:
T(EV) = T + T + T + T
-/here:
T = time delay after occurrence of the incident associated with
1.31
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notification of. responsible officials, interpretation of data> am!
the decision to evacuate as a protective action.
T = time required by officials to notify people to evacuate,
T = time required for people to mobilize and get underway.
T = travel time required to leave the affected areas.
T includes several separate time elements as defined above,
and all of them can be reduced by effective planning. Nominal values
for T may range from 0.5 hours up to 1.5 hours and possibly longer
depending on the adequacy of planning and whether the decision is to
be based on onsite information or offsite environmental measurements.
The least well defined time constraint is T , which is strongly
influenced by local population, geographic conditions, and planning.
T has been postulated to be inversely proportional to population
density; the closer people are together, the quicker it is to notify
them to evacuate. For fast developing incidents, news media warnings
must be augmented by telephone, pulic address, and door knocking, the
effectiveness of which is a function of local planning and resources,
There are new innovations such as computer telephoning, planes with
loud speakers, etc., which the local planner may find worthwhile
to explore. Tru value of T under the best conditions of local, planning
is estimated to range from 15 minutes to 1 hour or more.
T._, the time required for people tc prepare to leave, depends on
M
such parameters a;>:
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(1) Is tne family together?
(2) Rural or urban community? Some farms or industries require
nore shutdown time than others.
(3) Special evacuations - special planning effort is required
to evacuate schools, hospitals, nursing homes, penal
institutions, and the like.
(4) Tnere will be some people who will refuse to evacuate.
The bee; time for T._ for an urban family together might be 0.2 to
M
0.5 hours, whi^.e to shut down a farm or factory might take hours.
The evacuation travel time, T , is related to:
(1) Tota1 number of people to be evacuated.
(2) Tae capacity of a lane of traffic.
(3) The number of lanes of highway available.
(4) Distance of travel.
(5) Roadway obstructions such as uncontrolled merging of traffic
or accidents.
The totil number of people to be evacuated depends on the popula-
tion density and affected area. It is an advantage if good planning
can keep the area and thus the number of people to as small a value
as possible, or possibly to evacuate one area at a time so that the
number of people on the move at one time is within the capacity of the
roads.
The capacity of a lane of traffic depends on the number of vehicles
per hour and the capacity of each. Surveys during evacuations found
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4 persons/car on the average indicating that at 2,500 cars/hr at
35 mph, the capacity of a lane is 10,000 persons/hr. Commuter traffic,
however, contains about 1.2 persons/car, lowering the capacity to
about 3,000 persons/hr-lane. Use of buses exclusively, if this is
practical, increases the lane capacity by a factor of about 10 such
that 100,000 persons/hr-lane could be moved. However, if buses are
used, the increase in time caused by getting the buses to the evacua-
tion area and oy return trips must be considered. If the average
speed of traffic is less than 35 mph, capacity/lane-hr is lowered in
proportion.
The number of lanes of traffic is ordinarily sufficient for evacu-
ation from the low population zone around fixed nuclear facilities.
Lanes may be increased by using lanes that ordinarily carry traffic
into the area. All these lanes cannot be used, however, since some,
at the option of the planner, must be held open for emergency vehicles
coming into thr* area.
Traffic control will be effective in reducing the evacuation
travel time. Tf lanes ordinarily inbound are used for outbound traffic,
traffic officers will be required to direct vehicles to them; otherwise
they will not be used. Traffic barriers, signs, traffic light over-
rides, disabled vehicle removals, etc., will be required to keep
traffic speeds high. Traffic control at bottlenecks will be of par-
ticular importance. Allowing single lanes to run alternately rather
than having r.ars dovetail through an intersection will significantly
1.34
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increase traffic flow. Access controls to keep unauthorized vehicles
and persons out of the evacuated areas will be needed also.
Examination of specific sectors around four different light-
water powei reactors indicates that T may range from 0.2 to as much
as 1.5 hours under exceptional conditions where the road system is
inadequate compared to the population to be evacuated. An average
traffic speed of 35 mph was assumed if road capacity was great enough
to preclude traffic jams.
Table ?..5 summarizes the various time segments that act as
constraints on evacuation. These values are rough estimates that
should be improved upon by the local planner for each site. An
example of . one-hour evacuation might be the evacuation late in the
evening of a rural area including a small town (250 persons). In
such a case the population is small, concentrated, and at that time
the families would be united. An example of an evacuation in the
longer time range might be evacuation during the daytime of a rural, low
population zone containing farms. Warning would be time consuming,
and the preparation for farm shutdown might be lengthy. The road
system is adequate, but families may be separated during the day,
requiring Icnger evacuation travel distances. Emergency plans for
areas located near State boundaries would require interstate cooperation
and planning. .ligh population, high density areas such as those around
Indian Point present a different situation, and evacuation times are
more complex, probably longer, and must be analyzed on a case by case
basis. In these areas, notification time may be short but access
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Table 1.5 Approximate Range of Time Segments
Making Up the Evacuation
Approximate
Time Segment Range
Hours
TD 0.5 - 1.5
T 0.2 - 1.0(C)
N
T 0.2 - 2.0(d)
M
T 0.2 - 1.5(S)
T 1.1 - 6.0
population, high density areas such as
those around Indian Point, present a different
situation, and evacuation times are more complex,
probably longer, and must be analyzed on a case
by case basis.
Maximum time may occur when offsite radiation
measurements and dose projections are required
before protective action is taken.
Maximum time may occur when population density is
low and evacuation area is large.
Maximum time may occur when families are separated,
a large number of farms or industries must be shut down,
and special evacuations are required.
Maximum time may occur when road system is inadequate
for the large population to be evacuated and there are
bottlenecks.
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limited. Appendix B provides techniques for evaluating the various
time periods involved in evacuation.
B. Risk ?f Death or Injury
If evacuation were likely to greatly increase an individual's
risk of deatn or injury, this would act as a significant constraint
on the use of evacuation as a protective action for a nuclear incident.
Fortunately, examination of numerous evacuations indicate that risk
of death or injury is not likely to be increased when evacuation is made
by motor vehicle (_3) . Premature childbirth is routinely encountered
in emergencies and subsequent evacuations, and in at least one State
emergency pj.an, prior arrangements are made for this problem.
C. Evacuation Costs
For evacuations caused by storms or floods, cost is not usually
a constraint bacause hazard to life and limb is obvious and because
the evacuation cost is judged to be small compared to the damage
caused by the disaster. However, in the event of a nuclear incident
where there may be the strong inclination to evacuate even though the
radiation dose t.o be saved is vanishingly small, the economic cost of
the evacuat:on may act as a constraint. Therefore, the planner may
wish to estimate this cost for various kinds of evacuation.
Evacuation costs may be broken into four categories:
(1) costs involving evacuees,
(2) costs involving evacuators,
(3) financial losses of farm areas, and
(4) financial losses of urban and industrial areas.
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Limited information on estimated costs is given in reference (_3) .
For a specific site, the various costs probably can be ascertained
with more accuracy. Parameters that would affect the costs of an
evacuation around a specific site are listed in table 1.6. Considera-
tion of these parameters and how they affect cost should allow the
planner to calculate the approximate monetary cost of an evacuation
and thus estimate and evaluate this constraint.
1.6.3.2 Seeking Shelter
The local constraints on seeking shelter as a protective action,
such as time ti take action, cost of taking the action, and societal
considerations , intuitively tend to support taking such action since
the cost in each case is relatively small. However, if one compares
the effect oJ seeking shelter with some other action such as evacuation
on the basis of dose savings, it may be concluded that evacuation will
save a far greater dose than seeking shelter. Generally, shelter
provided by dwellings with windows and doors closed and ventilation
turned off "ould provide good protection from inhalation of gases and
vapors for & short period (i.e., one hour or less) but would be generally
ineffective after about two hours due to natural ventilation of the
shelter.
Not every constraint can be evaluated using established techniques;
therefore, a certain amount of subjective judgment must be made on the
part of the xocal planner. The important thing is that the local
planner be aware of the constraints associated with each action and
that these constraints be balanced on whatever basis possible in order
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Table 1.6 Parameters Affecting the Cost of Evacuation
Area
Size of area affected
Location
Population
Number
Distribution
Makeup
Institutions
Type
Population in
Care required
Farms
Size
Type
Product values
Business and Industry
Type
Size
Work force
Product value
Mode of Travel
Number of Evacuators Required
Shelters Needed
Duration of the Evacuation
Anti-looting Efforts
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to arrive "t a decision.
1.6.3.3 Access Controj.
Access control can be a very effective protective action to
avoid exposure of personnel who might otherwise enter high exposure
areas unnecessarily. Whether or not it can be applied effectively
at all sites trill depend upon several considerations which are site
specific. For example, the time required to establish the necessary
roadblocks way be longer than the exposure time. The cost of main-
taining the capability for roadblocks and control of access points
may be prohibitive. Furthermore, personnel that would be used in
maintaining roadblocks might be more effectively used for other
emergency functions. All of these factors must be considered in
deciding whether to plan for full or partial access control during
the early phases of an incident.
1.6.3.4 Respiratory Protection
Radiation exposure from inhalation of gaseous or particulate
radionuclides may be reduced by the use of respirators. These devices
protect the wearer by removing radioiodines (the primary gaseous nuclide
of concern) on activiated charcoal and by removing particulate material
by filtration. Several types of respirators are commercially available
for use by odult male workers in contaminated atmospheres. However,
respirators designed for women and children, i.e., the most radiation
sensitive part of the population, may not be readily available. The
first constraint on the use of respirators, therefore, is whether
suitable devices are available. Secondly, for respirators to be
1.40
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effective for the general population, they should be kept on hand by
each person for immediate use upon notification and they must have been
individually fitted. This means they should be distributed to the
population at risk prior to a nuclear incident, and training should be
provided for their use. The logistics of distributing such devices
after an incident would greatly reduce their effectiveness by limiting
their time of use. The cost of providing respirators for the entire
population at risk is also a constraint, especially for large popula-
tions. Additional constraints include upsetting the population by
acknowledging the danger with visible means and the failure of
individuals to have their respirators personally available over long
periods (years) Even if funding is available to provide the necessary
respirators, ic should be noted that use of such devices can only be
a short tern action of 2 to 3 hours. Therefore, they might best be
used in conjunction with other protective actions such as seeking
shelter or ( vacuation. It should also be kept in mind that respirators
would not be of value where the exposure of concern was from direct
radiation aud not from inhalation of iodines or particulate material.
Respirators may be most effective for emergency workers or other
persons requlrad to remain in evacuation zones.
1.6.3.5 Prophylaxis (Thyroid Protection)
The uptake of inhaled or ingested radioiodine by the thyroid
gland may be reduced by the ingestion of stable iodine. The oral
administration of about 100 milligrams of potassium iodide will result
1.41
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in sufficient accumulation of stable iodine in the thyroid to prevent
significant uptake of radioiodine. The main constraint in the use
of this me^ns of thyroid protection is that potassium iodide is
normally administered only by prescription and would have to be dis-
tributed in accordance with State health laws. Potassium iodide as
a prophylaxis is only effective if the exposure of concern is from
radioiodine and only if the stable iodine is administered before or
shortly aft^r the start of intake of radioiodine. All emergency
workers for areas possibly involving radioiodine contamination should
receive this kind of thyroid protection, especially if appropirate
respirators are not available. The cost constraint would not be
significant for potassium iodide itself, but the cost for administering
this material should be considered, including the cost of testing
emergency workers for sensitivity to iodine prior to issue or use.
The usrf of stable iodine as a protective action for emergency
workers has bean recommended by EPA, but only in accordance with State
health laws and under the direction of State medical officials as indica-
ted above. However, the efficacy of administering stable iodine as a
protective rction for the general population is still under consideration
by government agencies and should not be construed to be the policy of
EPA at this tiro*.
1.6.3.6 Milk Control
In order to protect the population from exposure to ingestion of
contaminated milk, the planner has two basic alternative actions, which
are:
1.42
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(1) Cow-feed or pasture control to'prevent the ingestion of
radioactive materials by dairy cattle, or
(2) Milk control either by diverting the milk to other uses
that allow the radioactivity to decay before ingestion or
by destroying the milk and substituting uncontaminated milk
from other areas.
The optimum action would be to prevent, through pasture and feed
control, contamination of the milk. This would be followed up by
milk control only in contaminated areas where pasture and feed control
were not carried out or were not adequate. Local constraints may reduce
the acceptability or effectiveness of these two protective actions.
The alternatives to taking these actions include:
(1) Permitting the population to receive higher dosage.
(Thyroid cancer is generally not fatal.)
(2) Suggest voluntary avoidance of the use of contaminated milk
by children and pregnant women. (Children are more sensitive
than adults because of greater intake of milk and greater
concentration within the thyroid.)
(3) Administer stable iodine as discussed earlier under thyroid
protection (section 1.6.3.5).
The local constraints on the control of dairy cow feed or pasture
may include the following:
(1) A shortage of uncontaminated feed.
1.43
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(2) A shortage of personnel to carry out feed and pasture controls
in ovacuated areas.
(3) The short time available to implement feed and pasture con-
trols over a large area (possibly hundreds of square miles)
r-ay create communication problems and uncertainties as to
the areas where pasture and feed control should be implemen-
> ed.
(4) The cost of the stored feed and the cost of transporting it
to needed areas might be prohibitive.
Local constraints on the control of milk may include:
(1) The shortage of nearby processing plants.
(2) Inadequate storage capacity to wait for radioactive decay.
(3) Objections to shipment of contaminated milk to other juris-
dictions for processing.
(4) Pollution from disposal of large volumes of milk.
(5) Snorfage of monitoring personnel and equipment for all milk
producers.
(6) Shortage of milk for critical users.
(7) Costs associated with transporting, storage, or disposal of
miJk.
The dos'J to the thyroid of a child from drinking milk contaminated
with radioicdine through the atmosphere-pasture-cow-milk exposure path-
way may be hundreds of times the thyroid dose that would be received
by the same -hild from breathing the air that caused the contamination
of the pasture. Therefore, the size of the area over which milk might
1.44
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have to be controlled could be much larger than the size of the area
that would be evacuated to prevent inhalation of the iodine.
To avoid the problems and constraints assoicated with milk
storage, transport, or disposal, the planner should prepare for pasture
or feed co-itrol in all directions from the plant out to five times the
distance planned for evacuation and in predominantly downwind directions
out to about 50 to 100 miles. Controls over greater distances could
be needed if the wind persisted in a single direction for an extended
period. If pasture and feed control actions have been implemented (even
if only partially implemented), noncontaminated milk supplies may be
available at least for critical users.
All mill: producers in the affected area should be restricted from
using or distributing milk until monitored. If monitoring of all milk
supplies is a constraint, monitoring efforts could be concentrated on
milk suppl:-as where pasture and feed control had been implemented and
on the frirges of the contaminated area.
The planner can reduce the effect of constraints related to uncon-
taminated feed supplies and processing plants by identifying their
locations and procedure for access.
Resistance by milk producers to protective actions for milk may
be reduced by the planner having answers to questions regarding reim-
bursements of costs incurred by the producer.
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1.6.3.7 Food Control
Food exposed to airborne radioactive materials may become
contaminated ey deposition of radioiodine and particulate material.
To avoid population exposure from ingestion of these materials, the
response planner should consider the following protective actions for
short term protection.
(1) Prohibition on use of potentially contaminated food such
as field and orchard crops and substitution from uncontamina-
ced supplies.
(2) Decontamination.
The primary constraint on the use of these controls will be the
availability of adequate substitute supplies at a reasonable cost.
If other supplias are not available or the cost is high, then it may
be necessary to implement decontamination procedures. For protection
beyond a fe~? days where availability and cost constraints would be
more critical, then decontamination may be even more cost effective.
The primary .neans of decontamination would be through washing and
peeling (where appropriate) of fresh fruits and vegetables. The con-
straints on fuch procedures would be the ability to monitor the decon-
taminated items to assure adequate decontamination. Monitoring of
food will likely be a much demanded service both by the individual
farmer-consumer and by the distributor.
Other alternative controls would be to impound food stocks and
store them to allow decay of radiation levels or destroy them to prevent
consumption. The main constraint on these alternatives would be spoilage
1.46
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and the vaiuc of the food stocks in relation to the costs of storage
or destruction.
1.6.3.8 Water Control
Water may be contaminated either by direct release of radio-
nuclides t< surface waters or by deposition from an atmospheric
release. V,?ter reservoirs supplied by land surface run-off or
cisterns sipplied by roof run-off would be most severely affected
by atmospheric deposition, whereas reservoirs supplied from streams
and lakes would be most affected by contaminated liquid effluents.
Spring and well water should not be affected by an accidental release
of radioactive material to the atmosphere or to waterways. However,
springs or wells that appear muddy after a rain might be suspect and
should be monitored after a rain if they are in the area receiving
heavy deposition. Some accident scenarios involve fuel melting its
way into the soil, and such a condition could contaminate underground
water supplies.
The protective actions for water can be either to prevent contamina-
tion or decontamination of the water supply or to condemn the use of
the water fo/ consumption.
In the ~ase of reservoirs supplied from surface or roof run-off,
prevention OL reservoir contamination would not be possible unless
methods exis.ed for diverting the run-off. Reservoirs receiving their
supply from a stream or lake normally are filled through pumping and
filtration stations which are controlled by operators. These stations
could be shut off if the source of the water supply became contaminated.
1.47
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This may also be true for food processors using a stream or lake
directly for their water supply. Many reservoirs supply water to
municipal Lystems through a filtration plant. Such a plant would
tend to decontaminate the water supply, and monitoring of water after
filtration world provide data that should be taken into consideration
in the process of deciding whether or not to condemn the supply.
The constraints associated with restrictions on supplies to
reservoirs or condemnation of water systems are related to the
difficulties, hardships, and costs associated with the resulting
shortage of wa :er supplies. If the planner determines that these
protective act'.ons may be appropriate for particular water systems,
he should also identify the hardships that may result and plan methods
for alternatxve supplies. These may include rationing of uncontaminated
supplies, substitution of other beverages, importing water from other
uncontaminated areas, and the designation of certain critical users
that could be allowed to use contaminated supplies. These might be
fire-water jystems and process cooling systems,
1.6.3.9 Restorative Actions
A. Lilting Protection Controls
The lifting of controls for protective actions may be justified
on the basis of cost savings when the corresponding health risks have
been adequately reduced. For example, the costs to the public and
the State in maintaining access control, pasture control, milk control,
or food and wacer control will exceed the risk reduction value of
1.48
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these controls after some period, and then the controls should be
lifted. The costs for maintaining these controls will be relatively
constant wi'th respect to time while their significance in reducing
risk will decrease as the source of radionuclides is halted and
the released naclides disperse or decay away. Therefore, it may be
desirable to lift controls even though some additional dose may be
accrued.
B. Reentry
After evacuation, persons will be allowed to reenter the zone
when the potential radiation risk has been averted or reduced to
guide levels for members of the general population. However, it may
be necessary for certain essential personnel to return even before
the dose is reduced to these guide levels. In addition, reentry
may be allowed earlier for less radiosensitive persons such as adult
males who n.ay need to return to their homes or jobs. The criteria
for reentry will require a balancing of remaining radiation risk
such as from ground contamination and the cost of disrupted services,
lost income, etc. resulting from the evacuation. Time is not a
constraint on reentry except as a factor in the cost of remaining out
of the evacrated area.
C. Decontaminat ion
The movement of radionuclides along several pathways involving
milk, food, and water may result in prolonged contamination. Each of
these elements may require processing to remove radioactive contaminants
1.49
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prior to consumption. In each case, the radionuclide concentrations
would be r duced to levels "as low as practicable" commensurate with
treatment costs.
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CHAPTER 2
Protective Action Guides for Exposure
to Airborne Radioactive Materials
2.0 Introduction
Following an incident involving a release of radioactive
material to tha atmosphere, there may be a need for rapid action
to protect the public from radiation exposure from inhalation
and/or from whole body external radiation. This chapter provides
Protective Action Guides (PAGs) for whole body external gamma
radiation and for inhalation of radioactive material in an air-
borne plume. A. person who is exposed to the plume of airborne
radioactive materials may also be exposed at a later date from
contaminated food, water, or other pathways. However, the PAGs
in this chapter refer only to the exposure received directly
from the airborne plume. The emergency response situation addressed
in this chapter is the period from initiation of an atmospheric
release unti1. perhaps two to four days after the event occurs.
During this ->eriod, the principal effort would be directed toward
protection of the public from direct exposure to the plume or from
inhalation of radioactive material in the plume.
It is important to recognize that the PAGs are defined in
terms of projected dose. Projected dose is the dose that would be
received by tne population if no protective action were taken. For
2.1
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these PAGs, the projected dose does not include dose that may have
been received prior to the time of estimating the projected dose.
For protective actions to be most effective, they must be instituted
before exposure to the plume begins. PAGs should be considered
mandatory values for purposes of planning, but under accident con-
ditions, the values are guidance subject to unanticipated conditions
and constraints such that considerable judgment may be required for
their application.
2.1 Whole Body External Exposure
A radioactive plume will consist of gaseous and/or particulate
material. Either of these can result in whole body external expo-
sure. Measurements or calculations of environmental levels of
radioactivity are usually in terms of exposure. To translate from
whole body gonrna exposure to whole body dose requires a correction
factor of approximately 0.67. However, due to the many uncertain-
ties in proie2Cing dose from exposure to a plume, it is generally
conservatively assumed that gamma exposure and whole body gamma
dose are equivalent.
Recommended PAGs for emergency response in the case of whole
body externr1 exposure to radionuclides in the atmosphere are
summarized fn table 2.1. These guidelines represent numerical
values as to when, under the conditions most likely to occur,
intervention is indicated to avoid radiation exposure that would
otherwise result from the incident. When ranges are shown, the
2.2
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Table 2.1 Protective Action Guides for Whole Body
Exposure to Airborne Radioactive Materials
Projected Whole Body
Population at Risk Gamma Dose (Rera)
General population 1 to
Emergen y workers 25
Lifesaving activities 75
(a)When ranges are shown, the lowest value should be used if
there ate no major local constraints in providing protection at
that level, especially to sensitive populations. Local con-
straints n?ay make lower values impractical to use, but in no
case should the higher value be exceeded in determining the need
for protective action.
2.3
-------
lowest valui should be used ±f there are no major local constraints
in providing protection at that level, especially to sensitive popu-
lations. Local constraints may make lower values impractical to use,
but in no case should the higher value be exceeded in determining the
need for protective action. The rationale and technical bases for the
numerical guides and their ranges are described in greater detail in
Reference (4_) and are summarized in Appendix C. It is recommended
that anyone responsible for applying these guides in a nuclear emergency
become familiar with the rationale on which the guidance was based.
2.2 Inhalation Dose
The giseous portion of a radioactive plume may consist of
noble gas PS and/or vapors such as radioiodines. The noble gases
will not cnuse as much dose from inhalation as from whole body
external exposure and therefore need not be considered as a
separate contributor to inhalation exposure. The principal
inhalation dose will be from the iodines and particulate material
in the plume.
2.2.1 Exposure to Radioiodines in a Plume
Due l D the ability of the thyroid to concentrate iodines,
the thyroi'd dose due to inhaling radioiodines may be hundreds
of times greater than the corresponding whole body external
gamma dose that would be received. The PAGs for thyroid dose
due to inhalation from a passing plume are shown in table 2.2.
The technical support for their development is provided in
reference (4) and is summarized in Appendix C.
2.4
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Table 1,2 Protective Action Guides for Thryoid Dose
Due to Inhalation from a Passing Plume
Projected Thyroid Dose
Population at Risk rem
(a)
General population 5-25
Emergency workers 125
Lifesaving activities (b)
(a)
^ 'Wl.en ranges are shown, the lowest value should be used if
there are no major local constraints in providing protection at
that level, especially to sensitive populations. Local con-
straints ni&y make lower values Impractical to use, but in no
case should the higher value be exceeded in determining the need
for protective action.
Nc specific upper limit is given for thyroid exposure
since in the extreme case complete thyroid loss might be an
acceptable penalty for a life saved. However, this should
not be necessary if respirators and/or thyroid protection for
rescue personnel are available as the result of adequate
planning.
2.5
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2.2.2 Exposure to ^articulate Material in a Plume
This section is being developed.
2.3 Interpretation of PAGs
The guides for the general population listed in tables
2.1 and 2.2 were arrived at in consideration of protection of
the public frcm early effects of radiation and maintaining the
delayed biological effects at a low probability. Consideration
has been nade of the higher sensitivity of children and pregnant
women and the need to protect all members of the public. Con-
sideratiot. has also been made that personnel may continue to
be exposed via some pathways after the plume passes, and that
additional PAGs may have to be applied to these exposure pathways.
Where a range of values is presented, the lower guide is a
suggested level at which the responsible officials should consider
initiating protective action particularly for the more sensitive
populations indicated above. The higher guide is a mandatory
level at which the respective governmental agency should plan to
take effective action to protect the general public unless the
action would have greater risk than the projected dose.
At projected doses below the lower guide, responsible
officials may suggest voluntary action available to the public
at risk. This should be done with the philosophy that popula-
tion doses be kept as low as possible as long as the effects of
2.6
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action are not more hazardous than the projected dose. The
concept of voluntary action and the types of action that may be
considered were discussed in Chapter 1.
The need for selected populations, such as emergency response
team members and persons involved in lifesaving activities, to be
allowed higher exposures than the general public is in line with
policies wherein these categories of individuals normally accept
greater risk. Public safety and nuclear plant personnel will be
essential to provide services for the public even though they may
receive a greater radiation exposure.
In tbi event greater exposures to selected populations are
required to save lives, these should be taken. However, if the
radiation injury in these lifesaving activities is excessive,
the harm iL£y exceed the good, so some restrictions must be made.
Because of the variations in sensitivity of the population
to radiation effects and in local conditions (weather, etc.), a
range of values is recommended for the general population. Where
selective protective actions (i.e. evacuation) for the general
population is possible, children and women of childbearing age
should be protected at the lower levels of the range. A further
interpretation of the range is that plans should be made to consider
organized protective action at the lower end of the range whereas it
is mandatory that plans be made to implement protective action at the
upper end. However, if no constraints existed, the lower range should
2.7
-------
always be used. Since constraints exist on a local basis under
different conditions, the range allows adjustment by local
officials during the planning stage for special local problems
as discussed in Chapter 1.
The values given for emergency workers recognize the need
for some civil functions to continue in the event of an evacu-
ation of the general population. The risks are considered to be
warranted when necessary on the basis of the individual exposure
and the benefits derived. In such cases, precautions should be
taken to minimize exposures to emergency workers.
PAGs for lifesaving missions are given for those persons
whose normal duties might involve such missions, i.e., police.
firemen, radiation workers, etc. These guides would normally
be limited to healthy males. No specific upper limits are
given for thyroid exposure since in the extreme case, complete
thyroid loss might be an acceptable penalty for a life saved.
However, this should not be necessary if appropriate protective
measures for rescue personnel are available as the result of
adequate planning. For example, respiratory protection and/or
stable iodine for blocking thyroid uptake of radioiodine should
be available to the extent possible for personnel involved in
lifesaving missions and other emergency actions. The issuance
of stable iodine must be in accordance with state medical procedures,
2Q
. O
-------
CHAPTER 3
Protective Action Guides for Exposure from Foodstuffs or Water
3.1 Whole Body External Exposure
3.2 Ingestion
3.2.1 Milk
3.2.2 Food
3.2.3 Water
(Guidance to be Developed)
3.1
-------
CHAPTER 4
Protective Action Guides
for Exposure from Material Deposited on Property or Equipment
4.1 Reentry and Release
4.2 Decontamination
4.3 Land Use
(Guidance to be Developed)
4.1
-------
CHAPTER 5
Application of Protective Action Guides
for Exposure to Airborne Radioactive Materials
5.0 Introducticn
Following notification that a radiological incident has
occurred involving an atmospheric release that may require
protection of the public, the State authorities will need
information for decisions on what protective actions to
implement. The types of information needed are (1) Protective
Action Guides (dose limits) adjusted for local situations and
(2) projected doses in specific areas for comparison to the
Guides. Projected doses must be determined on the basis of
data available following the incident. These data may come
from either onsite measurements and conditions or offsite
environmen-.al measurements. This chapter deals with methods
for estimating population dose from exposure to a radioactive
cloud or p_utne and comparison of the projected dose with
PAGs for decipions on protective actions. These methods are
recommended for use by State and local officials for develop-
ment of operational plans for responding to incidents at nuclear
facilities, The guidance in this chapter Is directly related
to releases to the atmosphere that have been postulated for
nuclear power facilities.
5.1
-------
5.1 Release Assumptions
The types of protective actions that should be planned to
reduce population exposure are related to the characteristics
of the relea3e that might occur. A recent publication of the
NRC, WASH-1400 (1), indicates that should there be an accident
at a nuclear power station, there is an extremely wide spectrum
of different kinds of possible releases to the atmosphere depen-
ding on the severity and the exact sequence of the failure modes.
Significant releases of radioactivity may occur within 1-1/2 to
2-1/2 hou-T of the initiating cause of the incident; therefore,
if protective actions are to be effective, they must be taken
promptly.
Incidences of relatively small environmental impact may
involve a loss of coolant for the reactor but without a meltdown
of the reactcr core. For this class of accidents, the release to
the atmosphere should be restricted to mostly radioactive noble
gases and iodines.
Accidents of increasingly larger environmental impact would
involve a meltdown of the reactor core and eventual loss of con-
tainment integrity. This class of accident will release quantities
of radioactive particulate matter as well as the radioactive noble
gases and iodiaes.
5.2
-------
5.1.1 Noble Gases and Radi_qioditie Releases
For an atmospheric release at a nuclear power facility that
involves only noble gases and radioiodines, it is usually con-
servative to assume that 100 percent of the equilibrium noble
gases inventory and 25 percent of the equilibrium radioiodine
inventory would be available for release from containment. In
the absence of more accurate information from the facility opera-
tor regarding the release composition, it would be conservative
to assume hat this composition is released to the environment
at the design leakrate. The relative abundance of radioiodines
and noble j,ases i° an actual release from containment would be
a function of the effectiveness of engineered safeguards (e.g.,
filters, spray systems, and scrubbing systems) in removing each
component.
Table 5,1 summarizes the total quantities of radiologically
significant gaseous radionuclides that are available to be
released to the containment vessel following a loss of coolant
accident at d 1,000 megawatt-electrical nuclear power reactor
assuming 100 percent of the noble gases and 25 percent of the
radioiodines escape from the core. These values may be adjusted
linearly fo - reactors of other sizes.
"'"This assumption is in agreement with NRC guidance (_2,5.,j>) on
assumptions that may be used in evaluating the radiological conse-
quences of an accident at a light water cooled nuclear power facility,
5.3
-------
Table 5.1 Initial inventory of the radiologically signit'ic.mt
noble gases and iodines
Nuclide
Megacuries
(a)
available for
release from
containment
Sum of kryptons 192 MCi
Sum of xenons 258 MCi
Sum of noble gases = 425 MCi
Sum of iodines = 184 MCi
Half life
Krypton- 8 5m
Krypton-85
Krypton-87
Krypton-88
Iodine-131
Iodine-132
Iodine-133
Xenon- 13 3m
Xenon-133
lodine-134
Iodine-135
Xenon- 13 5m
Xenon-135
33.5
0.66
64.4
93.0
18.7
28.5
45.9
4.0
164.3
51.5
39.5
19.0
46.4
4.4 hr.
10 yr.
76 min.
2.8 hr.
8.1 day
1.3 hr.
20 hr.
2.3 day
5.3 day
52 min.
6.7 hr.
16 min.
9.1 hr.
Ratio of
iodines _ 184
noble gases 425
Based on equilibrium inventory developed from maximum full
power operation of a 1000 megawatt electrical light-water-cooled
nuclear power reactor. This includes 100 percent of the noble
gases and 25 percent of the iodines.
5.4
-------
Calculations of the projected population dose based on
the relative quantities shown in table 5.1 indicate that the
thyroid dnne from inhalation of radioiodine ranges up to 1,000
times grer-.tet than the whole body gamma dose from noble gases
and radioiodines. If the engineered safeguards function as
designed, chsy should reduce the iodine concentration such that
the whole body gamma radiation exposure to noble gases will be
the controlling pathway.
5.1.2 Radioactive Particulate Material Releases
This section is being developed.
Initial studies indicate that except for the most severe
and improbable accidents postulated by WASH-1400, protective
actions (pjophylaxis iodine excepted) chosen on the basis of
assuming .ihat the iodine exposure pathway is critical (figure
5.2) will be sufficient to provide protection from radioactive
particular material. This particulate material will deliver
an additicnal dose to the lung and to the whole body from
material located in the lung, but these doses are not likely
to be greater than the thyroid dose.
5.2 Application of Protective Actions
Following an incident at a nuclear power facility in-
volving a release to the atmosphere, the most urgent actions
in terms of response time will be those to protect the popu-
lation from inhalation of radioactive materials in the plume
5.5
-------
and from direct whole body exposure to gamma radiation from the
plume. The time of exposure to the plume can be conveniently
divided into two periods; (1) the period immediately following
the incident when little or no environmental data are avail-
able to confirm the seriousness of population exposures, and
(2) a period when environmental levels and/or concentrations
are known During the first period, speed for completing such
actions as evacuation, seeking shelter, and access control may
be critical to minimize exposure in areas where PAGs may be
exceeded. Furthermore, environmental measurements made during
this period may have little meaning because of uncertainties
concerning plume location when measurements are made or changes
in release rate due to changes in pressure and radionuclide con-
centrations within containment. Therefore, it may be necessary
to initiate early protective actions on the basis of dose
projections provided by the facility operator followed by
adjustments tD these actions based on more detailed environ-
mental measurements.
For accidents involving a release to the atmosphere at a
nuclear power facility, the following sequence of events is
suggested to minimize population exposure.
(1) Notification by the facility operator that an inci-
dent has occurred that is expected to cause offsite
projected doses that exceed the PAGs. This notifica-
tion should be provided as soon as possible following
5.6
-------
the incident and prior to the release if possible.
(2) Immediate evacuation of a predesignated area.
(3) Monitor gamma exposure rates in the environment.
(4) Calculate plume centerline exposure rate as
inversely proportional to distance from release
point, or use prepared isopleths to estimate
exposure rate in downwind area.
(5) Use exposure rate and estimated exposure duration
to convert to projected dose.
(6) Compare projected dose to PAGs and adjust areas
for protective actions as indicated. Table 5.2
summarizes recommended actions as a function of
PAG levels for exposure to a gaseous plume.
(7) Continue to make adjustments as more data become
available.
5.2.1 Actions Based on Licensee Notification
The AEC Guide and Checklist (_2) indicates that the noti-
fication from a nuclear power facility to the State and local
response organizations should include an estimate of the
projected dose to the population at the site boundary and
in the Low population zone following an accidental release.
The State emergency response planners should make arrangements
with the facility operator to assure this information will be
made available on a timely basis (within 1/2 to 1 hour following)
5.7
-------
Table 5.2 Recommended protective actions to avoid whole body and thyroid dose from exposure to a gaseous plume.
Projected Dose (Rem) to
the Population
Whole bocjy <1
Thyroi d <5
Whole body 1 to <5
Thyroid 5 to <25
Whole body 5 and above
Thyroid 25 and above
Projected Dose (Rem) to
Emergency Team Workers
Whole body 25
Thyroid 125
Whole body 75
Recommended Action^9'
•No protective action required.
•State may Issue an advisory to seek shelter and await
further instructions or to voluntarily evacuate.
•Monitor environmental radiation levels.
•Seek shelter and wait further instructions.
•Consider evacuation particularly for children and
pregnant women.
•Monitor environmental radiation levels.
•Control access.
•Conduct mandatory evacuation of populations in the
predetermined area.
•Monitor environmental radiation levels and adjust area
for mandatory evacuation based on these levels.
•Control access.
•Control exposure of emergency team members to these
levels except for lifesavlng missions. (Appropriate
controls for emergency workers, Include time limita-
tions, respirators, and stable Iodine.)
•Control exposure of emergency team members performing
lifesaving missions to this level. (Control of time
of exposure will be most effective.)
Torrents
Previously recommended
protective actions may
be reconsidered or
terminated.
Seeking shelter would
be an alternative 1f
evacuation were not
Immediately possible.
Although respirators
and stable Iodine should
be used where effective
to control dose to emer-
gency team workers , thy-
roid dose may not be a
limiting factor for
lifesaving missions.
These actions are recommended for planning purposes. Protective action decisions at the time of the
incident must take into consideration the impact of existing constraints.
-------
the incident and prior to the start of the release if possible),
and that it will be provided in units that can be compared to
PAGs (i.e., projected dose to the whole body or thyroid).
The first indication that an incident has occurred with
potential for population dose in excess of PAGs should come to
State authorities from the facility operator. Although plans
may include provisions for the facility operator to include
information in the notification regarding projected dose to
the population, such information may not be available. Further-
more, if dose projections are available, there may be reason to
suspect tLeir accuracy. Therefore, the State should have planned
a designated area for immediate evacuation (or other suitable
action). Immediate actions would be taken in this area if the
facility operator's estimate of projected dose was not available
or was not considered to be on a sound basis. If the facility
operator provides projections of population dose, then these
projections should be used by the State to determine the area
for immediate action in lieu of the predesignated area.
The i-commended area to be designated for immediate action
is the dovnwind sector (one sector covers 22-1/2 degrees) and
the two adjacent sectors. The radial distance for action should
be to the outsr edge of the low population zone. Other planned
downwind distances or widths for immediate action may be justifi-
able for particular sites.
5.9
-------
A. transparency should be prepared which shows the down-
wind area for immediate action. The scale of the transparency
should be the same as the map of the environs around the facility
so that the action area can be quickly identified.
5.2.2 Actions Based on Environmental Measurements
During or following initial actions to protect the close-in
population, environmental exposure rate measurements should be
made to provide a data base for projecting dose and for re-evalu-
ating the ueed for additional protective actions or termination
of those actions already taken.
5.2.2.1 Dose Projection for Noble Gas and Iodine Releases
A gaseous release from a light water reactor is assumed to
include ndioactive noble gases, and iodines as shown in table
5.1. Unless engineered safeguards were successful in significantly
reducing che quantity of radioiodines available for release rela-
tive to the quantity of noble gases, the dose from the inhalation
of radioioiine would be the controlling pathway.
Since field measurements of environmental radioiodine con-
centrations would be difficult and time-consuming, it is recom-
mended that thfi State plan to measure gamma exposure rate and
estimate thyroid dose from inhalation by converting from gamma
exposure rate to projected thyroid dose. The method for this
conversion is discussed later in this section.
5.10
-------
The -projection of either whole body dose or thyroid dose
requires a knowledge of the exposure rate and the time period
of exposure. The time period of exposure may be difficult to
predict. Exposure would start at a particular site when the
plume ariived and would be ended by a shift in wind direction
or by an end to the release. Arrangements should be made for
the State or local weather forecast center to provide informa-
tion on predicted wind direction persistence during the inci-
dent. If neither wind change nor the time until the end of the
release c-n be predicted, the period of exposure could be
assumed to be equal to the maximum (or 99% probable maximum)
duration of wind direction for that site as determined from
previous luute.orological history.
Having obtained information regarding gamma exposure rate
at selected locations in the environment, one must then estimate
exposure rate in additional locations in order to identify the
pattern of the exposed area. Estimation of exposure rate patterns
based on a few downwind measurements can be conducted in a variety
of ways. One simple way is to determine a plume centerline exposure
rate at grnuna level at some known distance from the release point
and use these data to calculate exposure rates at other designated
distances downwind by conservatively assuming that the cloud center-
line exposure rate is inversely proportional to the distance from
5.11
-------
2
the release pcint. The following relationship can be used for this
calculation:
Where:
DI = exposure rate measured at distance RI
D_ = exposure rate at distance R_
One could then develop a crude and very conservative pattern of
estimated exposure rates by assuming that the exposure rate calculated
for the plume canterline would also exist at points equidistant from
the source dn the downwind sector (22^ degrees) and in the two adja-
cent sectors. This 67% degree sector allows for wind meander and
some uncertainty in wind direction. The use of this method would
likely result in an overestimate of the exposure rate in all areas
downwind of the measurement point. In addition, one must be sure
that the exposure rate measurement is taken at or near the plume
centerline.
A second and more accurate method for estimating exposure
rate pattern? is to use a series of prepared exposure isopleths
(maps with lines connecting points of equal exposure rates)
o
The canterline exposure rate can be determined by traversing
the plume af. a point sufficiently far downwind (usually greater than
one mile from the site) while taking continuous exposure rate measure-
ments. The highest rating should be at the centerline of the plume.
5.12
-------
plotted on transparencies. These isopleth plots are fre-
quently available from the licensee thus eliminating the
need for the State to develop them. Since both the
meteorological stability and the wind speed existing at
the time of the release affect the shape of the exposure
isopleth curves, several sets of curves would be needed to
represent the variety of stability conditions and wind
speeds likely to exist at that site. The appropriate trans-
parency can be selected on the basis of wind speed and
meteorological conditions at the time of the incident. The
transparency can then be placed over a map of the area such
that the curves are properly oriented with regard to wind
direction. The isopleth curves are used to estimate exposure
rate by plotting the exposure rates known at specific locations
on the curves. Exposure rates at other locations are simple
multiples of the known exposure rates as indicated by the
multipliers associated with each curve.
A third alternative for determining exposure rate patterns
is to obtain gamma exposure rate measurements at a large number
of locations and plot these data on a map of the arer.. This
method would provide the most accurate data but would require
a large number of radiation instruments and trained persons to
make the measurements as well as a method for communicating the
data to the control center on a continuing basis.
5.13
-------
Having established gamma exposure rate patterns in
the environment and having determined (or estimated) the
time peUod of exposure, the next task is to estimate the
projected whole body and thyroid dose to members of the
population so that the projected dose can be compared with
appropriate PAGs. If engineered safeguards operate as
designed, they may reduce iodine concentrations to levels
such that the whole body gamma radiation exposure from
noble gases will be the controlling pathway. Otherwise,
the controlling exposure pathway will be inhalation of
radioiodrnes resulting in thyroid dose ranging up to
hundreds of times the whole body gamma dose depending on
the effectiveness of the engineered safeguards.
To avoid the necessity for calculating projected dose
at the time of the incident, it is recommended that dose
projection nomograms be developed. Figures 5.1 and 5.2 are
examples of such nomograms. Appendix D provides details
regarding their development.
The projected whole body gamma dose can be estimated by
simply multiplying the gamma exposure rate at a particular loca-
tion by the time period of exposure. Figure 5.1 provides this
multiplication. It also provides a relationship between exposure
rate in mr/hr and the noble gas concentration based on the mixture
of radioactive noble gases shown in table 5.1.
5.14
-------
1.000,000 9
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PROJECTED TIME PERIOD OF EXPOSURE (HOURS)
345 678
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FIGURE 5.1-PROJECTED WHOLE BODY GAMMA DOSE AS A FUNCTION
OF GAMMA RADIATION EXPOSURE RATE AND PROJECTED
TIME PERIOD OF EXPOSURE
5.15
-------
GAMMA RADIATION DOSE RATE (MREM/HR)
3
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PROJECTED TIME PERIOD OF EXPOSURE - HOURS
FIGURE 5.2 PROJECTED THYROID DOSE AS A FUNCTION OF GAMMA
RADIATION EXPOSURE RATE AND PROJECTED TIME PERIOD OF EXPOSURE
A. USE OF THIS FIGURE ASSUMES THAT THE RADIOIODINE/IMOBLE GAS ACTIVITY
RATIO IS 0.3. IF IT IS KNOWN THAT THE RATIO HAS A LOWER VALUE, THE
CORRECTION FACTOR GIVEN IN FIGURE 5.3 SHOULD BE USED.
'.
3.
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100,000
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-------
The estimation of projected thyroid dose on the basis of
gamma exposure rates and duration of exposure is more complex
because the projected dose is also a function of the compo-
sition of the release which is a function of the type of
incident, the time after shutdown, and the operation of
engineered safeguards.
In the most probable event, radioiodines will be present
in a release but neither the ratio of radioiodines to the
noble gase-5 nor concentrations of radioiodines in the environ-
ment will be known. If this is the case, the conservative assump-
tion can Le made that the radioiodine is the most critical and
that the radioiodine/noble gas activity ratio is 0.3. (Although
the initial ratio in containment is assumed to be 0.4 as shown
in table 5.1, this value rapidly decreases with time and 0.3
would be : .ore representative by the time the plume reached the
population). This assumption allows the direct use of figure 5.2
to estimau^ projected thyroid dose as a function of gamma exposure
rates and tiire period of exposure. If the actual radioiodine/noble
gas activity ratio has been determined and is less than 0.3,
figure 5.3 mi/ be used to derive the appropriate correction factor
for gamma dose rate values before applying them in figure 5.2 If
radioiodines are known to be absent or reduced to 0.005 or less of
the originj-1 concentration, the critical exposure pathway becomes
that of whols body gamma exposure, and figure 5.1 applies instead
of figure 52.
5.17
-------
:
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HOLE BODY
WIA RADIATION
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TO USE THIS GRAPH
• rlND
TORR
RAT I
NOB!.
CORR
GAM
' BE U
PRO
FIGU
/
/
THE CORRtCTION FACTOR
ESPONDING TO THE KNOWN
0 OF RADIOIODINES TO
E GASES. APPLY THIS
ECT10N FACTOR TO THE
A RADIATION LEVEL TO
SED IN DETERMINING THE
ECTED THYROID DOSE IN
RE 5.2
/
/
f
•
f
f
/
/
_/
4
.002 .003 O04 O06O080.01 .02 .03 .04 .06 .080.1 .2 .3 .4 A .8 1
Gamma Radiation Exposure Rate Correction Factor
1
FIGURE 5.J GAMMA RADIATION EXPOSURE RATE CORRtCTION FACTOR
5.18
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A better method for correcting the gamma exposure rate for
use in figure 5.2 to estimate the projected thyroid dose would be
to take one or more iodine concentration measurements at some
locations where gamma exposure rate measurements were taken.
Compare the gairma exposure rates to the corresponding iodine
concentration measurements on figure 5.2 and determine the ratio
of measurer1 concentration to the observed "corresponding" con-
centration. This ratio can be used to correct other gamma
measurements prior to their use in figure 5.2 to project thyroid
dose.
Figure 5.2 can also be used to estimate projected thyroid
dose if one kr.ows environmental concentrations in terms of
o
nCi/cm . To use figure 5.2 to estimate projected thyroid dose,
one needs the projected time period of exposure and the environ-
mental radioactivity level. The time period of exposure may be
estimated on the basis of (1) history of maximum wind direction
persistence for that area, (2) forecasts of wind change at the
time of the incident, or (3) the facility operator's prediction
of the expected duration of the release based on plant conditions.
To estimate projected thyroid dose for a particular site,
plot the point of figure 5.2 corresponding to the exposure rate
(gamma exposure rate in mr/hr, or radioiodine concentrations in
uCi/cc) and the expected time period of exposure for persons at
that location. Estimate the projected thyroid dose from the dose
5.19
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values on the curves below and above the point. For example, if
the gamma radiation level is reported to be 100 mR/hr and is expec-
ted to last three hours, then the projected adult thyroid dose is
approximately 60 rems, and the child thyroid dose would be approxi-
mately 300 rems. (Refer to table 5.2 for recommended protective
actions associated with each projected dose).
Figure 5.3 is used only in the event that the radioiodine/
noble gas activity ratio is known and is less than the assumed
value of 0.3 and only for correcting the gamma exposure rate
for use in figure 5.2. No correction factor is needed if the
environmental radioactivity level is expressed as iodine con-
centration. The measured gamma exposure rate may be multi-
plied by the factor obtained from figure 5.3 to give a "corrected"
gamma exposure rate for use with figure 5.2 to determine
projected thyroid dose.
For example, if the radioiodine/noble gas radioactivity
ratio is measured and found to "be 0.01, the gamma radiation
level correction factor from figure 5.3 is 0.08. The "corrected"
gamma radiation level is then 8 mR/hr for a measured gamma radi-
ation level of 100 mR/hr. For a projected time period of exposure
3Note that the child thyroid dose is five times the adult thyroid
dose The child dose would apply to general populations for deciding
whether or not to evacuate, while the adult dose would apply to emergency
teams or other adults.
5.20
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of three hours, the actual projected child thyroid dose would
be approximately 25 rem as compared to approximately 300 rem
without use of the correction factor.
For a puff or continuous release to the atmosphere where
the report of release includes the number of curies released or
that could potentially be released or where the release rate
and the >xpected duration of the release is reported, the
immediate question becomes; how far downwind should actions
be taken to protect the population from the airborne plume?
Although uore projections based on release information would
normally be. done by facility operators, it is advisable for
State radiological personnel to understand the techniques
involved. The dose projections can be accomplished by using
nomograms such as those in figures 5.1 and 5.2 to identify the
time-concentration that would produce a projected dose equal
to the PAf and a plot of x^/Q versus downwind distance such as
figure 5.4 to determine the distance where that time-concentra-
tion would exxst.
To make this determination, one must have information
regarding the principal exposure pathway, the curies released
of the radi->nuclides contributing to that exposure pathway, the
windspeed, and atmospheric stability class. In the absence
of any of these bits of information, one must be prepared to sub-
stitute assumed values and conditions based on a knowledge of the
facility and the environment.
5.21
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-
These values assume
an Inversion 11d at
1000 meters altitude
and a ground level
release.
\
u
0.5
12 5 10 20
Distance Downwind (Miles)
kilometers 100
J 1 I
^ 5.4 Typical values for XU/Q as a function of
atmospheric stability class and downwind distance
5.22
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The methods for determining the downwind distance to where pro-
tective accion should be taken for a puff release are similar to the
methods fcr a longer term release. However, for purposes of using
the nomograms in figures 5.1 and 5.2, it is convenient to assign
a release time of one hour for the puff release. The distance
downwind for protective action can be read from a plot of xu/Q
versus distance for various atmospheric stability classes as
shown in figure 5.4. The term xU/Q can be calculated using the
relationship
CU = Q x xU/Q (D
Where:
o
C = environmental concentration of concern in Ci/m or
UCi/cm3
0 = average windspeed in m/sec. Multiply MPH by .5 to
obtain m/sec (approximately)
Q = release rate in curies/sec
X/Q = environmental concentration at a particular location
per ;urie per second being released at the source
O
i,sec/mj)
Then:
(2\
V '
CJ/Q
For example:
If the accident involves a puff release of 20,000 curies
of iodines and the PAG is 5 rem to the thyroid, then from figure
5.23
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5.2 one can observe that the concentration of concern over a
period of GI^ hour would be 3.3 x 10~6 uci/cm3. The release
rate averaged over one hour would be 20'000 ci = 5-5 ci/sec.
3600 sec
Therefore:
3.3 x 10-6 (uci/cm3) x U(m/sec)
5.5 ci/sec
= 6.7 x 10~7 U
If:
0 = ^.0 mph = 5 m/sec
Then :
XU/Q = 3 x 10~6
From figure 5.4 one can observe that a xU/Q value of 3 x 10~6
would occur at about 0.6 miles downwind under atmospheric sta-
bility condition A and about 3j> miles downwind under condition F.
For tha puff release, PAGs could be identified (i.e. 5 rem
to the thyroid) and a specific time period for the release could
be assumet1 (i.e., 1 hour = 3,600 sec) so that equation 2 could be
simplified to:
jJr/Q . 3.3 x 1Q"6 UCi/cc x U = .012U
ci/3600 sec curies released
or:
0.012U
Ci (3)
The methods presented in this Chapter for relating data at
the time of the incident to projected dose are recommended for
5.24
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use in development of operational response plans for gaseous
releases. However, planners are encouraged to improve on
these methods where possible and to alter them as necessary
to respond to special circumstances.
5.2.2.2 Dose Proj "iction for Particulate Material Releases
This section to be developed.
5.25
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CHAPTER 6
Application of PAGs for Foodstuffs and Water Contamination
6.1 Relocation
6.1.1 Whole Body
6.1.2 Organ Exposure
6.2 Shelter
6.2.1 Whole Body
6.3 Access Control
6.4 Milk Control
6.5 Food Control
6.6 Water Control
(Guidance to be Developed)
6.1
-------
CHAPTER 7
Application of PAGs for Contaminated Property or Equipment
7.1 Release and Reentry
7.2 Decontamination
7.3 Land Use
(Guidance to be Developed)
7.1
-------
CHAPTER 8
Application of PAGs for Transportation Incidents
(Guidance to be Developed)
8.1
-------
APPENDIX A
Summary of Interim Guidance on
Offsite Emergency Radiation Measurement Systems
(to be developed)
A-l
-------
APPENDIX B
Planner's Evaluation Guide for Protective Actions
(to be developed)
B-l
-------
APPENDIX C
Summary of Technical Bases for
Protective Action Guides
(to be developed)
C-l
-------
APPENDIX D
Technical Bases for Dose Projection Methods
(to be developed)
D-l
-------
REFERENCES
(1) U.S. ATOMIC ENERGY COMMISSION. An Assessment of Accident Risks
In U.S. Commercial Nuclear Power Plants. (WASH-1AOO, draft),
U.S. Nuclear Regulatory Commission, Washington, D.C. August 1974.
(2) U.S. ATOMIC ENERGY COMMISSION. Guide and Checklist for the
Development and Evaluation of State and Local Government Radio-
logical Emergency Response Plans in Support of Fixed Nuclear
Facilities. (WASH 1293) U.S. Nuclear Regulatory Commission,
Washington, D.C. December 1974.
(3) HANS, JOSEPH M., JR., and THOMAS C. SELL. Evacuation Risks -
an Evaluation. (EPA-520/6-74-002) U.S. Environmental Protection
Agency, Washington, D.C. June 1974.
(4) NELSON, N.S. Approaches to Population Protection in Case of
Nuclear Accidents. U.S. Environmental Protection Agency, Office
of Radiation Programs, Washington, D.C. (Draft, December 1974).
(5) U.S. ATOMIC ENERGY COMMISSION. Regulatory Guide 1.3. Assump-
tions Used for Evaluating the Potential Radiological Consequences
of a Loss of Coolant Accident for Boiling Water Reactors.
Directorate of Regulatory Standards, Nuclear Regulatory Commission,
Washington, D.C. June 1973.
(6) U.S. ATOMIC ENERGY COMMISSION. Regulatory Guide 1.4. Assump-
tions Used for Evaluating the Potential Radiological Consequences
of a Loss of Coolant Accident for Pressurized Water Reactors.
Directorate of Regulatory Standards, Nuclear Regulatory Commission,
Washington, D.C. June 1973.
R-l
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