ML20038A570
| ML20038A570 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim, Diablo Canyon  |
| Issue date: | 06/30/1980 |
| From: | ENVIRONMENTAL PROTECTION AGENCY |
| To: | |
| References | |
| CON-#487-4997 2.206, EPA-520-1-75, EPA-520-1-75-00, NUDOCS 8111130209 | |
| Download: ML20038A570 (184) | |
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PDL 0902.b p$l IPA-520/1-75-001 Manual 9
of Protective Action Gcides and Protective Actions for Nuclear Incidents September 1975 (Revised June 1980) i 4
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o Contents
- Zage, Chapter 1 - Perspectives for Protective Action.....................
1.1 1.0 Introduction.............................................
1.1 1.1 The Need for Planning..................................... 1.2 1.2 Nature of Protective Action Guides, Protective Action, and Restorative Action................................... 1 3 1.3 Protective Action Decision Making........................
1.7 1.3.1 Action Factors....................................
1.8 1 3.2 Incident Deterati na tions...........................
- 1. 8 1.3.3 Exposure Pathways.................................
1.11 1 3.4 Populations at Risk............................... 1.13 135 Radiation Effects.................................
1.14 1.4 Response Plan Action Times............................... 1.17 1.4.1 Preparation of Plans.............................. 1.17 1.4.2 Implementation of Plans........................... 1.19 1.5 Types o f Action..........................................
- 1. 22 1.6 Goals of Protective Action............................... 1.24 1.6.1 Balancing Factors to Achieve Protective Goals..... 1.25 1.6.2 constraints on Goal Attainment.................... 1.26 1.6.3 Evaluation of constraints......................... 1.28 1.6.3.1 constraints on Evacuation................ 1.28 1.6.3 2 Seeking Shelter.......................... 1.38 1.6.3.3 Access control...........................
- 1. 40 1.6.3.4 Respiratory Protection................... 1.40 1.6.3.5 Prophylme n (Thyroid Protection).........
1.41 1.6.3.6 Milk control............................. 1.42 1.6.3 7 Food control............................. 1.46 t
1.6.3.8 Water control............................ 1.47 1.6.3 9 Restorative Actions...................... 1.48 Chapter 2 - Protective Action Guides for Exposure to Airborne Radioactive Materials.................................. 2.1 2.0 Introduction.............................................
2.1 2.1 Whole Body External Exposure.............................
2.2 2.2 Tn ha l a tion Dose..........................................
- 2. 4 2.2.1 Exposure to Radiciodines in a Plume...............
2.4 2.2.2 Exposure to Particulate Material in a Plume....... 2.6 23 Interpretation of PAGs...................................
- 2. 6 b
o Contents (Continued) m P_ age Chapter 3 - Protective Action Guides for Exposum from Foodstuffs or Water'...............................................
3 1 Chapter 4 - Protective Action Guides for Exposure from Material Deposited on Property or Equipment.....................
4.1 Chapter 5 - Application of Protective Action Guides for Exposum to Airborne Radioactive Materials free an Accident at a Nuclear Power Facility............................ 5.1 5.0 Introduction............................................. 5.1 5.1 Release Assumptions...................................... 5.2 5.1.1 Radioactive Noble Gas and Radiciodine Releases.... 5.4 5.1.2 Radioactive Particulate Material Releases..........
5.5 5.2 Sequence of Events.......................... '.............
- 5. 5 5.2.1 Accident Notification............................. 5.7 5.2.2 Immediate Actions.................................
- 5. 8 r,. 3 Establisbaent of Exposure Rate Pattems.................. 5 9 1.4 Dose Proj ec tion.......................................... 5.12 5.4.1 Duratice of Exposure.............................. 5.14 5.4.2 Whole Body Dose Projection........................ 5.15 5.4.3 Thyroid Dose Projection........................... 5.18 5.4.3.1 Concentrations Based on Release Rates.... 5.21 5.4.3.2 Concentrations Based on Gamma Exposure Rate Measurements........................ 5.24 5.5 Protective Action Decisions.............................. 5.30 f
Chapter 6 - Application of PAGs for Foodstuffs and Water I
Con - t m.......................................... 6.i l
Chapter 7 - Application of PAGs for Contaminated Property or Equipment.............................................. 7.1 Chapter 8 - Application of PAGs for Transportation Incidents....... 8.1 References.......................................................... R-1
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I Contents (Continued) 8.8E1 Appendix A - Stamary of Interim Guidance on Offsite Emergency Radiation Measurement Systems.......................... A-1 Appendix B - Planner's Evaluation Guide for Protective Actions...... B-1 Appendix C - Summary of Technical Bases for Protective Action Guides................................................. C-1 Appendix D - Teobnical Bases for Dose Projection Methods............ D-1 a
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i Tables I.agy, Table 1.1 Exposure Pathways and Appropriate Responses............
1.5 Table 1.2 Action and Health Effects Versus Exposure Pathways..... 1.16 Table 1.3 Protective and Restorative Actions for Nuclear Incidents Resulting in Airborne Releases......................... 1.29 Table 1.4 Initiation Times for Protective Actions................ 1.30 Table 1.5 Approximate Range of Time Segments Making Up the Evacuation Time........................................ 1 36 1
Table 1.6 Parameters Affecting the Cost of Evacuation............ 1.39 Table 2.1 Protective Action Guides for Whole Body Exposure to Airborne Radioactive Materials......................... 2.3 Table 2.2 Protective Action Guides for Thyroid Dose Due to.
Tnhal a tion fma a Passing Plume........................ 2.5 Table 5.1 Reo - =aded Protective Actions to Reduce Whole Body and Thyroid Dose from Exposure to a Gaseous Plume..........
- 5. 31 Figures
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Figure 1.1 Sequence of Events for Response F1=aa4af and Respaad4af to Nuclear Incidents................................... 1.18 I
Figure 5.1 Projected Whole Body Gamma Dose as a Function of Gamma Exposure Rate and Projected Duration of Exposu m....... 5.17 4
Figure 5.2 Projected Thyroid Dose as a Function of Either Gamma Exposure Rate, or Ra'.ioiodine Concentration in Air and the Projected Exposure Time............................ 5.19 Figum 5.3 Typical values for XD/Q as a Function of Atmospheric Stability Class and Downwind Distance.................. 5.22 i -
Figun 5.4 Radiciodine Release Correction Factor.................. 5.27 Figure 5.5 Genom Exposum Rate Finite Cloud Correction Factor..... 5.28
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o Preface This manual has been prepared to provide practical guidance to State, local, and other officials on criteria to use in planning protective actions for radiological emergencias that could present a hazard to the public. The guidance presented here is not intended as a substitute for, or an addendum to, a State radiological emergency response plan. It is intended only to provide information for use in the development of such a plan.
In conformance with a Federal Register Notice of interagency responsibilities for nuclear incident response planning dated January 17, 1973 EPA is responsible for (1) establishment of pro-tective action guidelines, (2) reco - dations as to appropriate protective actions, (3) assistance to State agencies in the develop-ment of emer6ency response plans, and (4) establishment of radiation detection and measurement systems. This document is intended to be responsive to these assigned responsibilities.
The manual is organized to provide first, a general discussion of Protective Action Guides and their use in planning for the implemen-tation of protective actions to protect the public. This is followed by chapters dealing with Protective Action Guides for specific exposure pathways and time periods. The application of Protective Action Guides i
and protective actions is discussed separately for various categories of source terms. Support information that has not been previously published is provided as appendices.
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l'ha loose leaf format was chosen for flexibility. Copies of additional or revised sections will be forwarded routinely to manual recipients designated as having responsibilities for developing or updating State radiological amargency response plans.
Users of thf.s = annal are encouraged to provide comments and suggestions for improving the contant. Comments should be sent to the EPA Office of Radiation Programs, Environmental Analysis Division,
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I CHAPTER 1 Perspectives for Protective Action 1.0 Introduction in emergency preparedness planning for a nuclear incident with l
l potential for exposing the general public to harmful radiation.
public health officials require criteria to determine the need for protective actions and for choosing appropr'iate protective actions.
EPA is responsible for providing these criteria and for assisting the States in preparing emergency response plans to implement these criteria.
After a nuclear incident occurs, an estimate is made of the radiation dose which affected population groups may potentially receive.
This dose estimate is called the projected dose. A protective action is an action taken to avoid or reduce this projected dose when the I
benefits derived from such action are sufficient to offset any j
undesirable features of the protective action. The Protective Action i
Guide (PAG) is the projected dose to individuals in the population which warrants taking protective action.
A Protective Action Guide under no circumstances implies an acceptable dose. Since the PAG is based on a projected dose, it is used only in an ex post facto effort to =4n4=4*e the risk from an event which is occurring or has already occurred.
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F.xposures to populations from an incident may well be above
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acceptable levels, in an absolute sense. However, since the event has occurred, PAGs should be implemented to ameliorate the impact on already exposed or yet-to-be exposed populations.
On this basis there is no direct relationship between acceptable levels of societal risk and Protective Action Guides. PAGs balance risks and costs against the benefits obtained from protective action, assuming that the projected threat will transpire. The responses made 1a o given situation should be based on PAGs and the spectrum
'of pcesible protsetive actions available at that time.
1.1 The Need for Plann_ing Within the general framework of providing
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health protec-tion for an endangered public, tha public official charged with re-sponse to a hazardous situation may be faced with a number of decisions which muire be made in a short time. A number of possible alternatives for action cay be available, but the information needed to select the optimum alternative may not be available. In those situations where a public official must rapidly select the best of several alternatives, it is helpful if the number of decision points can be reduced during the accident response planning phase.
The efforts of p1===4ne activities can usually be based on the need for inusediate response. Therefore, the objective is to minimire the number of possible responses so that resources are expended only on viable alternatives in emergency situations. During planning it is possible to assess value judgments and determine which steps in 1.2 gum e
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f response are not required, which steps can be answered on the basis of prior judgments, and which r===fn to be decided in an actual emergency. From this exercise, it is then possible to devise a set or several sets of operational plans which can be called out to I
answer the spectrssa of hazardous situations which may develop.
l In the case of an accident at a nuclear reactor, a hazardous situation could develop which may have public health implications over a large area with diverse populations and population densities.
Probably little time will be available to amh decisions. The availability of " action guides" based on advance planning will facili-tate rational. decisions in emergency situations. During'the p1=aa4ag stage, the responsible public official must consider the total range of possible release scenarios and consider in each what goals are f-achievable keeping in mind both fiscal and societal costs. Because of this knowledge of local conditions, he will be aware of any con-straints which may restrict his scope of response, such as specific industries, institutiens, $.-traffic patterns, etc. He will then be able e..a.4p.
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I to select the optimum response for each situation.
1.2 Nature of Protective Action Guides, Protective Action, and Restorative Acrion Protective Action Guides are the.nssaarical projected doses which act as trigger points to initiate protective action.
PAGs must be provided for three broad pathways of radiation exposure:
(1) Exposure from airborne radioactive releases. This type of exposure could occur within a short period following an
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(2) Exposure through the. food chain. This exposure will be from ingestion of contaminated foodstuff and water. It I
may commence shortly after the passage of airborne radio-v active materials and may continue for a long or short time depaading on the radionuclides involved.
(3) Exposure from radioactive materials deposited on the ground.
Here we are d==14ng with a change in background radiation 1evels, and exposure pathways may includa inialation, ingestion, and external whole body exposures.
1i Different PAGs must be developed for each pathway of exposure since different criteria of risk, cost, and benefit are involved.
Each exposure pathway would involve different sets of protective or restorative actions as indicated in table 1.1.
Each action listed applies to the gener"al population except for prophylmwin, respiratory protection, and protective clothing. These actions would primarily apply to emergency workers.
Erposure to the airborne plume is related to the duration of a release inte the atmosphere. While release durations as long as 30 days or more are theoretically possible, for amergency purposes, release durations of a fu hours up to a few days are more realistic.
Protective action to be taken for this pathway may include any or all of the following:
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(1) avacuacion, (2) respiratory protection, (3) shelter, (4) prophylaxis (thyroid protection), and (5) controlled access, b -
Eastorative actions would then include:
(1) reentry first by survey and decone=4 nation teams, (2) removal of respiratory protection, (3) exit from shelters, (4) stopping 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 radionnelides involved. Control of this pathway of exposure would be by:
(1) control of access to cone-4nated animal feeds, (2) deconem=4 nation of certain foodstuffs, (3) diversion and storage to allow decay of short half-life radionuclides, and (4) destruction of conemminated foods.
Exposure from materials deposited on the ground might also be l
either short term or chronic depending on the radionuclides involved.
Protective actions would include:
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I (1) evacuation, and (2). controlled access.
Since the problem for ground cone==4 nation involves an increase in background levels, denial of access might continue for utended periods of time. Deconenmination may then be the only action which will allow free access to and utilization of cone==inated areas within a short time. Restorative actions would be reentry, decone==4 nation.
and lifting of controls.
5 The PAGs are to provide standardised 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 flexibilfty in response is expected to be within the limits of accuracy of deter =ini"F the (C
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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j The decision to initiate a protective action may be a complex process with the benefits of taking the action being weighed assinst the risks and constraints involved in taking the action. In addition, the decision will likely be ande under difficult emergency conditions, 3
probably with little detailed information available. Therefore, l
considerable planning is necessary to reduce to annageable levels the 4
pagfans leading g*gve 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 t
responsible pisaning office can be shown in a brief description of the factors involved. Baszcallh the officer must balance problems l
l involving identification of the magnitude of the release, possible l
i 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==a11 releases having no asasurable consequences offsite to large scale releases possibly involving large populations and areas. Responses must be appropriate to the incident reported.
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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 insediately 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.
.i The magnitude and duration of the release may be estimated by l
site personnel from plant conditions or from knowledge of the type of incident t. hat 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
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be based on accident scenarios from WASH-1400 Q), design basis acci-dents evaluated in the IntC 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.
Cun=nt meteorological conditions can be observed directly at the site and relevant locations. However, complete meteorological data will c
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 l
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Geography is important both in its influence on meteorology and on demography sad in its influence on value judgments to be made.
The p1m==1=g for a coastal site or a river valley site any be different due to road patterns and methods for communicating or applying protec-tive actions.
Demography is a variable to be considered during the p1=-4==
f 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.
j Providing for the ability to detect and measure a release are j
important factors for p1=aa4==.
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 onsite measurements. Detection and measurement at locations offsite are necessary to update and/or confira predictions about the I
movement of the release in the ecA.ronment. 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.
l The source tera, meteorology, and geography parsmeters are utilized in making a prediction of the path and time profile for the
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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.
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1.3.3 Exposure Pathwavs The next decision after the determination of an accident situs-tion will probably concern identification of important pathways of radionuclides to the population. Exposure pathways of immediate importance and the tim'a 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
,r-is probably by air. The air pathway will be via inhalation of
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either gases or particulates and whole body exposure to the plume.
b 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.
Re-Water is a pathway for expcsure by ingestion or inumersion.
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 fa orobably only a minor pathway 1.11 t
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S of exposure in the short run. However, the gastrointestinal system must be considered for longer term ingestion of contaminated drinking water.
Ingestion of food is an important exposure pathway. However, with the possible exception of drinking water, milk, and conta=f nated 2.
leafy vegetables, entry of released materials into food and passage
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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 race 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 cont==4 nation, in addition to providing part of the direct whole body exposure, also provides a contribution to the air pathway.
i Released material deposited on soil can be resuspended, thus possibly i
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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 decov amination 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 pisaning based ou the geography and demography of the area around the site and on critical pathways are essential to identifying populations at greatest risk.
The average 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.
l Children, including the fetus and unborn children, are generally more sensitive than healthy adults. For this i
reason, such members of the population may be selected i
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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 4
ji are engaged in public service activities durtag or after
, the accident are voluntarily placing themselves under different criteria for protection than the general popula-I tion. Finally, sous persons are involuntarily included I
under different criteria because the risk of taking action I
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.
,i 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, any include fatalities, symptoms of radiation sickness, or clinically detectable changes. Efforts to protect selected populations will extend to prevention of fatalities, minirization of 1.14
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effects is not hard to justify because of the inuminence 3,'
of such effects. However, they must be made rapidly under conditions of competing needs to protect the public.
(2) Delayed statistical effects (i.e., biological effects which i
can only be observed on a statistical basis) will occur i
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 r
of epidemiological studies in groups of people who had been exposed to radiation. Decisions concerning statistical affacts on populations will be nore difficult because of the 1sek 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 pathvey are shown in table 1.2 for a typical population.
I Effects on==1==1s, vegetation, or real estate are also possible l
but may be controlled or alleviated to the extent that decontamination is employed or that destruction of the affected items is employed.
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Table 1.2 Action and Health Effects Versus Exposure Pathways Exposure Responsa Action Public Pathway Time Available Health Effects Air - Particulate Min - Er P
D Gas Min - Er P
F E.D Water - Particulate
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Dr4 akin? Water Hr - Me PER D
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Foodstuffs Da - Mo PER D
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D Direct Min - Da P&R E 12,F Direct - Facility Min PER F E.D Air Min - Er P
F.E. D, Water Er PER D,y,E Actions: P - Protective R - Restorative Effects: F - Rapid Fatality E - Early D - Delayed 1,
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1.4 Response Plan Action Times A typical sequence of events for developing emergency plans and 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.
1.4.1 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 prepara emergency response plans according to the legislative mandates or needs within a given State.
E' (2) Then basic plans should be developed using appropriate G
guidance from this manual and the AEC " Guide and Checklist" (2).
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.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 6
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i NUCLEAR
RESPONSE
IM DENT i
PL ANNING
RESPONSE
j EMERGENCY PROTECTION RESTORATION t
i Preliminary evalu-Develop emergency response atton of incident P an i and projected doses l
rafnpe Fleid monitoring and continuing evaluation o
of e8Posure pathways, population at risk, dose and test plan projections. PAGs. and protective actions Activate State
- I'"##
Protective action decision Review of Protective Action Restorative Initiated laplemented Action i
plan fi e
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u Notify State Radiation Decision to Acceptance authorttles returns to prepare emer-of 9"I* I"'I S 9ency response plan I
plan
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=
=
=
=
Projected Dose flee Notification time
~
Response time implementation time Ilme 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 evolded by protective action Partial accumulation of projected dose during restoration FIGURE l.1 SEQUENCE OF EVENTS FOR RESf0NSE PLAlall:14G AND RESPONDING To NUCLEAR INCIDENTS
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k 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 e fective.
8
~-
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 i
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 characterised by urgency in deter =4ninF the need i
for protective action and getting the action initiated. In general, 4
this may be considered to be the first few hours following notification of an incident and deals primarily with protection of the population
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1.19
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a 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 min 4 - time loss in starting implementation of protective action in the offsite area. Proper planning must include incentives l
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 onsite and offsite Q). Ideally, this notification should occur as soon as conditions in the facility are such that an impending accidental release potentia 3 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.1 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 inpending releases would not involve disincentives to the facility operator.
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I I - M ately upon becoming aware that an incident has occurred i
I that any result in exposure of the offsite population, e 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 from monitoring data at the point of radionuclide release j
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 a
predesignated areas or in the areas indicated by projected dose based.
I on facility operator information. In the absence of detailed informa-tion from the facility operator as indicated above, the emergency plans
.v should provide for action in the insiediate 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 1evels in the environment, meteorology, wl environmental conditions.
Further actions or modifications to actions already taken should be based on these data and Protective Action Guides considering constraints 1
discussed in section 1.6 of thia chapter.
The State should continue to seek information on radionuclide releases and environmental monitoring data. In fact, an evaluation of 1
1.21 i
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o 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 acdify pro-r;ttive 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 wacuation would
~
be implemented before any population exposure. However, the action may not be initiated in time to avoid all of the projected dose, 1
and some dose may be received during implementation of the action.
The restoration phase includes those actions takan to restore conditions to " normal". Restorative actions inchde the halting of protective actions, the lifting of restrictions, and possible decon-e==ination procedures.
J 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 actw n would usually be taken by State authorities if the risk of undesirable radiation effects is anticipated to l
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 l
public information provided dur:fsg an accident situation.
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Voluntary action may be valid in the gray area where the l
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1.22 l
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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 n
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homes or civil defense shelters, controlling food and water V
distribution, prophylaxis (e.g., thyroid protection), or individual protective actions (e.g., gas masks, protective clothing, etc.); and (2 b storative action where everything is returned to " normal".
This action includes lifting restrictions or halting activities initiated as protective actions. It also includes decone==4 nation where necessary.
The actions to be taken should be evaluated and set in priority or sequence -ith identification of ranges for appropriate action and of l'
decision points during planning. Based on prior judgment of which l
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actions may be effective in any given situation, scenarios can be
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prepared which will indicate which actions or six 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. How$ver, various constraints any prevent att=ining 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 nortality or increased probability of hereditary defects in future l
generations.
1 l
The =in4=4 ration 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 be very large as compared to the avoidable dose, different protective actions might be warranted.
1.24
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.6.1 Balancing Factors to Achieve Protection Coals
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The ideal goal is==r4=um 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 1
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 balmacing of costs and risks will place constraints on the
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options available for action. This balancing also implies that in V
planning, certain cut-off points can be identified' e.g., a marginal increase in protection probably may not justify the required expendi-tures or extensive disruption of fanilies or daily activities.
These costs and constraints should be evaluated in planning by the l
I 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 ac' tion 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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-it 1.6.2 constraints on coal 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 may be restric-tad 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) l l
releases. After an incident, exposures of the population close to the i
l site may occur before control of the situation is established. Even af ter 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 l
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l access to utilities, food stores, crops, etc., will reduce the total 4
cost due to the accident.
Resources will be one of the largest constraints on viable t
options for 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 j
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 and practice in implementation of protective actions will limit the number of viable options for protecting the public.
In general, as the population to be protected increases, less protection is available for the s.ame total cost (equal levels of L.
protection require greater fiscal investment in large populations than in small populations). Likewise, as the level of preparedness increases, the cost of obtaining and maintain 4ng this preparedness increases. The cost of protective action, however, will probably be t
a step function. Each decision to take an action or extend an action l
l will cause an 1neramental step increase in the cost. All of these constraints must be considered in p1===4=g operations so that the optimum protection 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 pisas must be thoroughly informed on what protect!1ve 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
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response plan and should be specified during the p1=aning phase rather than at the time of the incident. There are, however, local i
constraints associated with each protective action which will influence the decision to implement a given protective action. The local planner
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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 persoective on a common scale. Since many of the constraints cannot be quantified, local planners must use rationaJ. 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-I siderations, etc., that relate to each protective action. This infor-l
(
mation should be valuable to the local planner in making the value judgments that are necessary to plan actions during an emergency.
i 1.6.3.1 Constraints on Evacuation While evacuation any seem to be the protective action of choice l
following a nuclear incident at a fixed nuclear facility, constraints 1.28 s
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..s Table 1.3 Protective and Restorative Actions for Nuclear Incidents Resulting in Airborne Releases Protection Phase
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Nuclear Incident Approximate Time of initation
,,(c p
0-4 hr.
4-8 hr.
l > 8 hr.
Puff Release * -Gaseous 1,2,3,4,5 3,4,5 3,4,5,6 9,10,11 or Gaseous and 7,8 Particulate continuous Release (b) 1,2,3,4,5 1,2,3,4,5 1,2,3,4, 9.10,11 Gaseous or Gaseous 5,6,7,8 and Particulate 1 Evacuation (a)hff rhee - las th 2 Shelter C'
3 Access control (b) h t h ous t h e -
2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> or more D
4 Respiratory protection for emergency workers (c) Restoration phase may begin 5 Thyroid protection for emersency workers j
6 Pasture control g,..g.,..
y,9g g 7 Milk control 8 Food and water control 9 Lift protection controls i
1 10 Reentry 11 Decont==4 nation i
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Table 1.4 Initiation Times for Protective Actions Approximate Exposure Pathway Action to be Initiated Initiation Time 4
0-4 hours inhalation of gases or evacuation, shelter, access control, respiratory particulates protection, prophylaxis (thyroid protection) direct radiation evacuation, shelter, access control 4-48 hours allk take cows off pasture, prevent cows from drinking surface water, quarantine contaminated milk harvested fruits and wash all produce, or impound produce
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vegetable drinking watc<-
cut off contaminated supplies, substitute from other sources
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I unharvested produce delay harvest until approved 2-14 days harvested produce substitute uncontaminated produce l
milk discard or divert to stored products, such as cheese i
drinking water filter, demineralize
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.sseociated 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.prutective 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 t
reasonable protective actions for each site.
A.
Effectiveness of Evacuation The effectiveness of evacuation in limiting radiation dose is j
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
,n.
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 minisize their impact, thus =mv4=4:ing the effectiven' ass of the evacuation.
The evacuation time, T(EV), at a particular site is defined as the time from the start of the nuclear inciden*. to the time when evacuees have cleared the affected areas. It may be expressed as:
T(EV) = TD+TN+Tg+TT where:
T = the dday af ter occmence of the Ment assochted 6 p
1.31
notification of responsible officials, interpretation of data, and
/
the' decision to evacuate as a protective action.
time required by officials to notify people to evacuat.e.
T
=
N time required for people to mobilize and get undervey.
T
=
g travel time required to leave the affected areas.
T
=
T T includes several separate time elements as defined above D
and all of them can be reduced by effective planning. Nominal values 4i for T may range fr a 0.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> up to 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> and possibly longer D
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 y
j influenced by local population, geographic ~ conditions, and planning.
l[
T has been postulated to be inversely proportional to population y
density; the closer people are together, the quicker it is to notify
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them to evacuate. For fast developing incidents, news media warnings I
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. The value of T under the best conditions of local planning y
is estimated to range from 15 minutes to 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> or more.
T, the time required for people to prepare to leave, depends on y
such parameters as:
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o (1) is the family together?
(2) Rural o: urban community? Some farms or industries require more shutdown time than others.
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(3) Special evacuations - special planning effort is required to evacuate schools, hospitals, nursing homes, penal institutions, and the lika.
(4) There vill be some people who will refuse to evacuate.
The best time for T for an urban f amily together might be 0.2 to g
0.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, while to shut down a farm or factory might take hours.
The evacuation travel time. T, is related to:
T (1) Total number of people to be evacuated.
(2) The capacity of a lane of traffic.
e (3) The number of lanes of highway available.
6V (4) Distance of travel.
(5) Roadway obstructions such as uncontrolled merging of traffic or accidents.
The total number of people to be evacuated depends on the popula-tion density and affected area. It is an advantage if good p1==4ag 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 l
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 1.33
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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 isne capacity by a factor of about 10 such that 100,000 persons /hr-lana could be moved. However, if buses are used, the increase fa time caused by getting the buess to the evacua-tion area and by return trips must be considered. If the average S p h,capacit gla pnhrysloweredin speed of traffic is les than proportion.
The number of lanes of traffic is ordinarily sufficient for evacu-ation from the low population zone around fixed nuclear facilities.
Ianes 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 the area.
Traffic control will be effective in reducing the evacuation travel time. If lanes ordinarily inbound are used for outbound traffic, traffic officers will be required to direct vehicles to them; otherwise j
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 cars dovetail through an intersection will significantly r
i 1.34 6
increase traffic flow. Access controls to keep unauthorized vehicles j
and persons out of the evacuated areas will be needed also.
f Fvn=ination of specific sectors around four different light-1 water power reactors indicates that T may range fr a 0.2 ter as much T
9 as 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> 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 jans.
Table 1.5 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 a one-hour evacuation might be the evacuation late in the 1
evening of a rural area including a small town (250 persons). In s/
such a case the population is==a11, concentrated, and at that time the families would be united. An evample 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 longer evacuation travel distances. Emergency plans for areas located near State boundaries would require interstate cooperation and planning. High 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 1.35
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'l Table 1.5 Approximate Range of Time Se s
Making Up the Evacuation Time
.,I Approximate Time Segment Range Hours T
0.5 - 1.5(b)
D T
0.2 - 1.0(*)
N T
0.2 - 2.0(d) 3 T
0.2 - 1.5(*)
T 1.1 - 6.0
(*}High populatics, high density areas such as those around ladian Point, present a different situatica, and eva nation. times are more couplex,
,J probably longer, trJ saast be analysed on a case by case basis.
(b)Marium time may occur when offsite radiation measurements and dose projections are required before protective action is taken.
4 (c) Maw 4== time may occur when population density is low an'. evacuation area is large.
l (d) Mar 4== time may occur when _ families are separated, a large number of, farms or industries must be shut down, and special evacuations are required.
(*) Mart== tima 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 per$oss involved in evacuation.
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B.
Risk of Death or Injury If evacuation were likely to greatly increase an individual's risk of death or injury, this would act as a significant constraint on the use of evacuation as a protective action for a nuclear incident.
Fortunately,===intion of numerous evacuations indicate that risk of death or injury is not likely to be increased when evacuation is ande l
by motor vehicle (3). Preasture childbirth is routinely encountered in energencies and subsequent evacum.l.ons, and in at least one State emergency plan, prior arrangements are made for this problem.
C.
Evacuation Costa For evacuations caused by storms or floods, cost is not usually j
a cot traint because hazard to life and limb is obvious and because i
h the evacuation cost is judged to be small. compared to the damage caused by the disaster. However, in the event of a nuclear incident 1
where there any be the strong inclination to evacuata even though the radiation dose to be saved is vanishingly small, the economic cost of the evacuation may act as a constraint. Therefore, the planner may wish to estimate this cost for various kinds of evacuation.
Evacuation costs any be broken into four categories:
(1) costs involving evacuees, (2) costs involving evacustors, (3) financial losses of farm areas, and (4) financial losses of urban and industrial areas.
1.37 l
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I Limit'ed information on estimated costs is given in reference (3_).
For a specific site,.the various costs probaoly 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-
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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 to 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 of 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 i
provided by dwellings with windows and doors closed and ventilation turned off would provide good protection from inhalation of gases and vapors for a short period (i.e., one hour or less) but would be generally ineffective af ter about two hours due to natural ventilation of the l
l 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 local 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 I
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Table 1.6 Parameters Affecting the Cost of Evacuation 1
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l Area 1
l Size of area affected i
Location I
Population l
Number j
Distribution Makeup Institutions T7Pe Population in Care required i
Farms Size T7Pa A
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Product v=1na,
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Business and Industry T7Pe Size Work force Product value Mode of Travel Number of Evacuators Required Shelters Norded i
Duration of the Evacuation j
Anti-looting Efforts 1.39
o to arrive at a decision.
j 1.6.3.3 Access Control Access control can be a very effective protective action to avoid exposure of personnel who might othg? vise enter high exposure areas unnecessarily. Whether or not it een be applied effectively at all sites will depend upon several cour!1derations which are site specific. For exsaple, the tras required to establish the necessary roadblocks may be longer than the exposure tira. The cost of main-taining the capability for roadblocks and control of access points may be prohibitive. Furthermore, personnel that would be used in mainemining reedblocks 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.
4 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 adult 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 realily available. The first constraint on the use of respirators, therefore, is whether suitable devices are available. Secondly, for respirators to be
/
1.40
o effective for the general population, they should be kept on hand by each person for inmediate use upon notification and they must have been individually fitted. This===n=
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 G.
respirators, it should be noted that use of such devices can only be f
e a short term action of 2 to 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. Therefore, they might best be used in conjunction with other protective actions such as seeking shelter or evacuation. It should also be kept in mind that respirators would not be of value where the exposure of concern was from direct radiation and not from inhalation of iodines or particulate material.
l Respirators may be most effective for emergency workers or other I
persons required to r== min in evacuation zones.
1.6.3.5 Prophylaxis (Thyroid Protection)
The uptake of inhaled or ingested radiciodine 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 W*
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in sufficient accumulation of stable iodine in the thyroid to prevent significant uptaka of radiciodine. The main constraint in the use of this manna of thyroid protection is that potassium iodide is normally ad=inistered only by prescription and would have to be dis-tributed in accordance with State health lave. Potassium iodide as l
a prophylaxi:' '
only effective if the exposure o' concern is from radioiodine and only if the stable iodine is ad=inistered before or shortly af ter the start of intake of radiciodine. All emergency workers for areas possibly involving radiciodine conramination should receive this kind of thyroid protection, especially if appropirate respirators are not available. The cost constraint would net be significant for potassisa iodide itself, but the cost for administering this material abould be considered, including the cost of testing emergency workers for sensitivity to iodine prior to issue or use.
The use of stable iodine as a protective action for emergency workers has been rec ded 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 action for the general population is still under consideration
~
by government agencies and should not be construed to be the policy of EPA at this tima.
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:
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(1) Cow-feed or pasture control to prevent *the ingestion of
' radioactive materials by dairy cattle, or (2) Yilk control either by diverting the milk to other uses i
tu t allow the radioactivity to decay before ingestion or by destroying the milk and substituting uncone==4nated milk from other areas.
The optimum action would be to prevent, through pasture and feed i.
control, cornmination of the milk. This would be follt,wed up by milk control only in conemminated 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 protectiv2 actions.
The alternatives to *=1 ring these actions include:
(1) Permitting the population to receive higher dosage.
m (Thyroid cancer is generally not fatal.)
v (2) Suggest voluntary avoidance of the use of cone==inated milk by children and pregnant women. (Children are more sensitive than adults because o? greater intake of milk and greater concentration within the thyrcid.)
(3) Administer stable iodine as discussed earlier under thyroid protection (section 1.6.3.5).
The local constre.ints on the control of dairy cow feed or pasture may include the following:
(1) A shortage of uncontaminated feed.
1.43
{
o i
(2)
A shortage of personnel to carry out feed and pasture controls in evacuated areas.
(3) The short time available to implement feed and pasture con-a trols over a large area (possibly hundreds of square miles) may create e - miention problems and uncertainties as to the areas where pasture and feed control should be implemen-ted.
(4) The cost -f the stored feed and the cost of transporting it to needed areas might be prohibitive.
Local constraints on the control of milk may include:
d; (1) The shortage of nearby processing plants.
- j (2) Inadequate storage capacity to wait for radioactive decay.
(3) Objections to shipment of contaminated milk to other juris-i dictions for processing.
(4) Pollution frca disposal of large volumes of milk.
(5) Shortage of monitoring personnel and equipment for il milk producers.
(6) Shortage of milk for critical users.
(7) Costs associated with transporting, storage, or disposal of milk.
The dose - the thyroid of a child from drinking, milk contaminated with radiciodine through the atmosphere-pasture-cow-milk exposure path-way may be hundreds af times the thyroid dose that would be received 1
by the same child from breathing the air that caused the contamination of the pasture. Therefore, the size of the area over which milk might 1.44
~
-1 i
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 control in all directions from the plant out to five times the distance planned for evacuation and in predom bantly downwind directions out to about 50 to 100 miles. Controls over greater distances could i
be needed if the wind persisted in a single direction for an extended i
period. If pasture and feed control actions have been implemented (even if only partially implemented), nonconemminated milk supplies may be available at least for critical users.
i All milk producers in the affected area should be restricted from using or distributing milk until monitored. If monitoring of all afik l
supplies is a constraint, monitoring afforts could be concentrated on s.,
i milk supplies where pasture and feed control had been implemented and on the fringes 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 a,e access.
Resistance by milk producers to protective actions for milk may 8
be reduced by the planner having answers to questions regarding rain-
~
bursements of costs incurred by the producer.
1.45
7 o
1.6.3.7 Food Control Food exposed to airborne radioactive materials may become cone==4nated by deposition of radiciodine 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 potencia11y contaminated food such ll as field and orchard crops and substitution from uncontamina-il ted supplies.
(2) Decont==ination.
The primary constraint on the use of these controls will be the
-1 availability of adequate substitute supplies at a reasonable cost.
I If other supplies are not available or the cost is high, then it may he necessary to laplement decontamination procedures. For protection beyond a fsw days where availability and cost constraints would be i '}
more critical. then decontamination may be even mora cost effective.
l The primary===na of decontamination would be through vashing and peeling (where appropriate) of fresh fruits and vegetables. The con-straints on such procedures would be the ability to monitor the decon-taminated items to assure adequate decone==ination. Monitoring of food will likely be a much d.==r.ded service both by the individual farmer-consumer and by the distributor.
Other alternative controls would be to impound food stor.ks and store them to allow decay of radiation levels or destroy them to prevent consumption. The main constraint on these alternatives would be spoilare
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I af the value of the food stocks in relation to the costs of storage or destruction.
1.6.3.8 Water Control 1
Water may be contaminated either by direct release of radio-nuclides to surface waters or by depositiori from an atmospheric release. Water reservoirs supplied by land surface run-off or cisterns supplied by roof r.,7: :#f would be mo-t sesst.ly affected by atmospheric deposition, whereas reservoirs supplied jrom streams and lakes would be most affected by conemminated 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 O
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 coner.mina-tion or decentaminatior, of the water supply or to condemn the use of the water for consumption.
In the case of reservoirs supplied from surface or roof run-off, prevention of reservoir contamination would not be possible unless methods existed for diverting the run-off. Raservoirs receiving their supp1r 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.
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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
=micipal systems through a filtration plant. Such a plant would tend to decontaminate the water supply, and monitoring of water after filtration would provide data that should be taken into considerati:en 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 water supplies. If the planner determines that these protective actions nay be appropriate for particular water systems, he should also identify the hardships that may result and plan methods for alternative supplies. These may include rationing of uncontaminated supplies, substitution of other beverages, importing water from other uncone==inated areas, and the designation of certain critical users that could be allowed to use cont==inated supplies. These might be fire-water systems and process cooling systems.
1.6.3.9 Re torative Actions I
A.
Lifting Protection Controls l
The lif ting of controls for protective actions may be justified 1
(
on the basis of cost savings when the corresponding health risks have been adequately reduced. For example, the costs to the public and the E ate in maintaining access control, pasture control, milk control, i
or food and water control will exceed the rick reduction value of 1.48 d
-*mgm
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o these controls after some periot and then the controls should be lifted..The costs for maintaini g these controls will be relatively constant with respect to time while their significance in reducing risk will decrease as the source of radionuclides is-halted and the released nuclides 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 lerein 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 may need to return to their homes or.'%s.
The criteria 1
l for reentry will require a balancing of remaining radiation risk i
l I
such as from ground contamination and the cost of disruptea services, I
glo,sging; pas,, etc rg Q the evacuation. Time is not a constraint on reentry except as a factor in the cost of remaining out of the evacuated area.
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C.
Decontamination 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 contmainants 1.49 g---------w=-we-t
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I CHAPTER 2 Protective Action Guides for Exposure
[
to Airborne Radioactive Materials r
l 2.0 Introduction Following an incident involving a release of radioactive material to the atmosphere, there may be a need for rap'd action to protect the public from radiation exposure from inhalation 7
j snd/or from whole body external radiation. This chapter provides Protective Action Guides (PAGs) for whole body external gama radiation and for inhalation of radiotetive material in an air-1 borne plume. A person who is exposed to the plume of airborne
{
radioactive materials may also be exposed at a later date from A-cont==4n=ted food, water, or other pathways. However, the PAGs in this chapter refer only to the exposure received directly U
i from the airborne plume. The emergency response situation addressed in this chapter is the period from initiation of an atmospheric release until perhaps,two to four days after the event occurs.
During this period, the principal effort would be directed toward protection of the public from direct exposure to the plume or from l
inhalation of radioactive material in the plume.
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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 the population if no protective action were taken. For i
(
t 2.1 l
I l
l
i these PAGs, the projected dose does not include dose that may have been received prior to the time of estimating the projected dose.
j For protective actions to be most effective, they must be instituted i
before exposure to the plume begins. PAGs should be considered aandatory values for purposes of planning, but under accident con-ditions, the values are guidance subject to unanticipated conditions I
sad 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 gassna exposure to whole body dose requires a correction factor of approximately 0.67.
However, due to the many uncertain-ties in projecting dose from exposure to a plume, it is generally conservatively assumed that ga m exposure and whole body gamma dose are equivalent.
Recosamended PAGs for emergency response in the case of whole body external exposure to radionuclides in the atmosphere are l
summarized in table 2.1.
These guidelines represent nu:aarical 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 M
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- able 2.1 Protective Action Guides for Whole Body Exposure to JLirborne Radioactive Materials Projected Whole Body Population at Risk Gamma Dose (Rem)
General population 1 to 5(*)
Emergsucy workers 25 Lifesaving aecivities 75 I
(
j (a)When ranges are shown, the lowest value should be used if L'
there are no major local constraints in providing protection at that level, especially to sensitive populations. Local con-straints may make lower values impractical to use, but in no case should the higher value be exceeded in determining the need for protective action.
O e
2.3
o lowest value should be used if there are r.o major local constraints m
in providing protection at that level, espeHm1'y to sensitive popu-lations. Local constraints may maka lower values impractical to use, but in no case abould the hi her value be exceeded in deter =4nfne the.
t 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 rec h ed that anyone responsible for applying these guides in a nuclear emergency become f=414=e with the rationale on which the guidance was based.
2.2 Inhalacion Dose
-.M
-*-Tit @ousfportion of a radioactive ' plume may consist of 49 so-noble gases and/or vapors such as radiciodines. The noble gases will not cause as much dose from fnhalation as from whole body external exposure and therefore need not be considered as a D
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 Rar'toiodines in a Plume Due to the ability of the thyroid to concentrate iodines, the thyroid dose due to inh =14a! radiciodines may be bundreds of times grearn than the corresponding whole body external gamma dose tha:. 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 refarence (4) and is summarized in Appendix C.
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o Table 2.2 Protective Action Guides for,Thryoid Dose Due to Inhalation from a Passing Plume l
Projected Thyroid Dose Population at Risk ren 5-25(*)
General population Emergency workers 125 i
I Lifeasving activities (b)
-O'.-
(a)When ranges are shown, the lowest value should be used if D-there are no major local constraints in providing protection at that level, especially to sensitive populations. Local con-strain _ts may maka lower values impractical to use. but in no case saoula une nignet vaAun be exceacea 2n ueterman2.ng we need for protective action.
(b)No specific upper limit is given for thyroid exposure since in the extreme casa complete thyroid loss might be~an accep uple penalty for a life saved. However, rhis should not be necessary if respirators and/or thyroid protection for rescue personnel are available as the result of adequate p1=n=4ne.
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2.2.2 Exposure to Particulate Material in a Plume This section is being developed.
2.3 Interpretation of PAGs The guides for tb, general population listed in tables 6
2.1 and 2.2 were arrived at in consideration of protection of
- l the public from early affects of radiation and main *=4=4ag the I I l
delayed biological effects at a low probability. Consideration i
has been made of the higher sensitivity of th41dren and pregnant women and the need to protect all members of the public. Con-sideration has also been made that personnel may continue to be exposed via some pathways af ter the plume passes, and that additional PAGs may have to ha applied to these exposure pathveys.
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 taka 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-t l
tion doses be kept as low as possible as long as the effects of 2.6
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action are not more hasardous than the projected dose. The concept of voluntary action and the types of action that any be considered were discussed i'n 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
~
j greater risk. Public safety and nuclear plant personnel will be 3
assential to provide services for the public even though they may receive a greater radiation exposure.
In the event greater exposures to salacted populations are i
required to save lives, these should be t,kan.
However, if the 4
?
radiation injury in these lifesaving activities is excessive,
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1
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the harm may excead the good, so some restrictions must be nada.
v Because of the variations in sensitivity of the population to radiation effects and in local conditions (weather, etc.), a a
range of values is ree - nded for the general population. Where salective protective actions (i.e. evacuation) for the general population is possible, children and women of chiIdbearing 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 and of the range whereas it is mandatory that plans be ande to implement protective action at the upper end. However, if no constraints existed, the lower range should 2.7
o
- t i
3 always be used. Since constraints exist on a local basis under different conditions, the range allows adjustment by local.
officials during the p1 - 4a= 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 i
and the benefits derived. In such cases, precautions should be taken to =4n4=4*e 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 workars, 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 p1-ime.
For example, respiratory protection and/or stable iodine for blocking thyroid uptake of radiciodine should be ave.ilable 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.
k 2.8
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CHAP 1Z1 3 Protective Action Guidas for Exposure from Foodstuffs or Water I
3.1 Whole Body External Exposure D
3.2 Ingestion 3.2.1 Milk 3.2.2 7<M 3.2.3 Watr2r (Guidance to be Developed)
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GAPTER 4 y
1 Protective Action Guides for Exposure from Material Deposited on Property or Equipment 4.1 Raantry and Ralsase i,
4.2 Decontassination 4.3 Land Use (Guidance to be Developed)
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o CHAPTER 5 Appliostice of Protective Action Guides for Exposure to Airborne Radioactive Materials frca an Accident at a Nuclear Power Facility 50 Introduction
^
This chapter deals with methods for estimating population dose
~
free plume exposure based ce release rates and meteorological
~
conditiens or based m offsite radiological measurements. It also provides guidance for comparison of projected dose with PAGs for decisicais on protective actions. These dose projection methods are recosmonded for use by State and local officials for development of operational plans for responding to incidents at nuclear power facilities.
Following a radiological incident involving an atmospheric release that may require protection of the public, State authorities will need informatica to make decisicuts on what protective actions to implement and where they should be implemented. The information needed includes (1) Protective Actica Guides adjusted for local situations and (2) projected doses in specific areas for comparison to the Guides. Protective Actica Guides were provided in j
Chapter 2.
Projected doses must be determined on the basis of data
~
available following the incident. These data may coes frca (1) plant conditions, (2) miease rates and meteorological conditions, or (3) offsite radiological measurements, or combinations thereof.
i Revised 6/79 5.1 y
y-
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The methods presented in this Chapter for relating data at the time of the incident to projected dose are recommended for use in development of operational respcase plans for atmospheric Mleasee at nuclear power facilities.
Planners are encouraged to improve on the methods where possible and to alter them as necessary to respond to special cirouastances. State pisaners should specifically consider the use of any improved dose projection methods developed by the nuclear facility operator.
5.1 Release Assumptions The guidance in this Chapter is directly related to esleases to l
the atacephere that have been postulated for nuclear power facilities. WASH-1400 (1) indicates that should there be an accident at a nuclear power station, there is an extremely wide I
spectrum of different kinds of possible releases to the atmosphere j
and different time frames fe releases depending on the severity and the exact sequence of the failure modes.
A nuclear poteer reactor may suffer a lose of coolant hut, without a meltdown of the reactor core. For this class of accident, the release to the atmosphere should be mostly radioactive noble saaes and iodines. Accidents of increasingly larger environmental impact would occur in associatics with a meltdown of the reactor oore and eventual loss of containment integrity. This class of 1
l I
Revised 6/79
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5.2
~-v--*w-,-
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accident could release quantities of radioactive particulate material as well as the radioactive noble gases and iodines.
i However, for planning purposes, it is recoamended that radiciodines 1
be assumed to repmsent the principal contributor *4 inhalation dose, and for situations where whole body dose from the plume would I
~
be the contmiling exposure pathway, it should be assumed that noble
]
l, gases would be the principal contributors.
Guidance on time frames for releases cannot be very specific because of the wide range of time fmmes that could be associated with the potential spectra of accidents that could occur.
Therefcre, it will be necessary fer planners to consider the possible different time periods between the initiating event and arrival of the plume and possible time periods of releases in c
relationship to time needed to implement protective actions. The Reactor Safety Study indicates, for example, that major releases may begin in the range of one-half hour to as such as 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> after an initiating event and that the dure.c:. in of the releases may range from one-half hour to seveml days with the major portien of the release occurring within the first day. In addition, significant plusse travel times are associated with the most adverse meteorological conditions tnat might nault in large potential exposures far from the site. For example, under poor dispersion conditicos associated with low windspeeds, two bours or more might Revised 6/79 5.3
/
., _, _ _ - ~,,, _,
l l
1 9
be required for the plume to travel a distance of five ails.s.
Higher windspeeds would MSult in shorter travel times but would provide acre dispersion, making high exposurs at ices distances such less likely. Additional infomation on time frames for releases any be found in Reference Q).
5.1.1 Radioactive Noble Gas and Radiciodine Releases For an atmospheric release at a uclear power facility that involved caly noble gases and radioicdines, it would usually be conservative to atsume that 100 percent of the equi'ibrium noble gas inventory and 2f percent of the equilibrius radiciodine inventory would be available for release froa containment. In the absence of more accurate inforantion from the facility operator regarding the miease composition, it should be assumed that this composition is misased to the environment. The relative abunriance of radioicdines and noble gases in m 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.
l This assumption is in agnement with NRC guidance Q,5,6,) on assumptions that any be used in evaluating the radiological consequences of a loss of coolant accident at a light water cooled nuolear power facility.
Revised 6n9
-d 5.4
o i
l t
i l
Table 31 of Appendix D summarizes the total quantities of radiologically significant gaseous radionuclides that would be in inventory under m.1"brium conditions for a 1000 Igie plant.
Calculations of the projected population dose based on a release l
aixtum consisting of 1005 of the noble gases and 255 of the radioiodines indicate that the thyroid dose fica inhalation of radioicdine ranges up to 400 times greater than the whole body gamma l
dose from noble gases and radiciodines. However, if the engineered safeguarsis functica as Nsigned, they should reduce the iodine concentration such that the whole body ganea radiation exposum from noble gases would be the controlling pathway.
j 5.1.2 Radioactive Particulate Material Releases l
Except for the most severe and improbable accidenta postulated i
c.
by WASH-1400, protective actions (prophylaxis iodine excepted) chosen on the basis of assuming the iodine exposure pathway is l
critical (figure 5.2) should be sufficient to provide protection f
free radioactive particulate material. This particulate material will deliver an additional dose to the lung and to the whole body from material located in the lung. However, it is not anticipated j
i that lung expcaure would represent the controlling exposure patbusy for accidents at nuclear power facilities.
5.2 Sequence of Events Following an inc? dent at a nuclear power facility involving a l
release to the atmosphere, the most urgent protective acticca in torna of response time will be those needed to protect the Revised 6/79 5.5
o N.
/
population from inhalation of radioactive materials in the plume and fmm direct whole body exposum to games radiation fmm the plume.
The time of exposure to the plume can be divided into two periods; (1) the period immediately following the incident when little or no environmental data are available to confirm the seriousness of population exposures, and (2) a period when enviromental levels and/or concentrations are krzawn. 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 PACS are postulated to be exceeded. Furthermore, enviramaestal measurements made during this period may have little meaning because of uncertainty concoming-plume locatim when measurements vem made or uncertainty concerning changes in release mte due to changes in pressum and radionuclide concentrations within containment.
Therefore, it would generally be advisable to initiate early predetermined protective actions en the basis of dose projections provided by the facility operator. During the recond period when environmental levels are known, these actions can be adjusted as appropriate.
I For accidents involving a release to the atmosphere at a nuolear power facility, the following sequence of events is suggested to minimise population exposure.
l Revised 6/79 j
5.6 l
I I
(1) Notification by the facility operators that an incident bas occurred with potential to cause offai*a projected doses that exceed the PAGs. This notification should be provided as som as possible following the incident and prior to the misase if possible.
(2) Immediate evacuatim or shelter of populations in predesignated areas without waiting for confirming release rate measurements or environmental radiation measurements.
(3) Monitor gamma escsure rstes (and iodine concentraticca if possible) in the environment. The facility operator should monitor release rates and plant conditions.
(4) Calculate plume centerline agosure rate at various F
distances downwind from the release point, or use prepared isopleths to estimate egosure rates in downwind areas.
v' (5) Use eg oeure rates, airborne concentrations, and estimated exposure duratice to convert to projected dose.
(6) Compare projected dose to PAGs and adjust areas for protective actions as indicated.
l (7) Continue to make adjustments as more data become available.
5.2.1 Accident Notification The first indicatien that a nuclear accident has occurred should coes to State authorities from the facility operator. The notification frca a nuclear power facility to the State and local l
Revised 6/79 5.7 i
4 m,
m respcase organi:atiens should include an estisate of the projected dose to the population at the site boundary and at more distant locations alcog with estimated time frames. The State emergency response planners should :nake arrangements with the facility operster *a assure this informatien will be made available en a timely basis (within 1/2 hour er less follcwing the incident and price to the start of the release) and that it will be provided in units that can be ecmpared to PAGs (i.e., projected dose in rem to the whole body or thyroid).
5.2.2 I= mediate Actions The Planning Basis (7) reco= mends that States designate an Emercancy Planning Zone (EPZ) for protective actions fcr plume exposure out to about 10 miles from a nuclear pcwer facility.
Within this distance it may also be practical to plan an arsa for i= mediate respmse price to the availability of infor=ation for making dose projections. This could be a circular area described by a desigrated radial distance frca the facility. Acticos would be taken within approximately a 90 degree secter dcunwind cut to the designated distance based en cotification frca the facility operster that plant conditions exist which present a potential ter offsite l
doses in excess of the PAGs. The remaining area cut to the IPf.
1 l
would be placed en alert pending som intematien.
~4 hen additional l
infermaticn er ferecasts en wind directica and meteorology became I
available, decisiens could be made en additierM. areas for l
3evised 6/79 5.s e
r
-w
protective _acticns. With good meteorological and wind cirection inforsatien, it signt be possible to reduce the width of the sector for protective actions. Ecwever, if wind direction is variable or if the start of the release is delayed, or if the release duration is lmg, the width of the sector may increase or possibly extend to a complete circle. The importance of good informatim and forecasts on wind directim cannot be overemphasized.
The designated distance for 1smediate actions would be used mly in situations where the facility operator could not estimate offsite projected doses. If the facility operator provides projections of populatim dose, then these should be 'Amed by the State to determine the downwid distance for 1:ssediate ation in lieu of the predesignated distance. The outer edge of the low population :ene is a suggested radial distance for insediate actions w
in the absence of reasons fer other distances.
5.3 Establishment of Excesure Rate Patterns 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 reevaluating the need for additional protective actions or terminaticn of those actions altsady taken. Planning guidance for the collection of these data is provided in Appendix A.
(Note: Appendix A is still under development. Reference Q) will form the basis for Appendix A and is reconnended as an alternate source of information.)
Revised 6/79 5.9 O
D After obtaining exposure rates er concentrations at selected locations in the environment, these must be translated to additional locaticas to identify the pattern of the expcsed area. Exposure rate patterns based n a few downwind seasurements can be esti:nated in a variety of ways. Cne simple way is to measure plume centerline exposure rate at ground level at some known distance from the release point and use these data to calculate exposure rates at other designated distances dcwnwind by assu:ning that the cloud centerline exposun rate is inversely proportional to the fistance from the release point.
The following relationship can be used fer this calculation:
fa )*
,l D s D,1 g
A\\ 2/
9 exposure rate sensured at distance 3 Where: D 3
D2 = exp sure mte at distance 32 x = rate of diffusion as a functica of distance.
This relationship can be used to develop a crude pattern of estinated exposure rates by assuming that x = 1.5 and that the 2The centerline exposure rate can be determined by traversing the plume at a point sufficiently far dcwnwind (usually greater tre one sile from the site) while taking centinuous exposure rate seasurenants. The highest reading should be at the centerline of the plune.
s Revised 6/79
,j 5.10 4
_-----m,
~ - - - _ - _,
exposure rate calculated for the plu:ne centerline would also exist at points equidistant frca the source in the general downwind direction.
To use this method, one must be sure Wat the expcaure rate measurement is taken at or near the plume centerline.
A second and easier method for estimating exposure rate patterns is to use a series of prepared exposure rate isopleths (maps with lines connecting points of equal exposure rates) plotted m transparencies. These isopleth plots are frequently available from the licensee, thus eliminating the need for the State to develop them. Since both the meteorological stability class and the windspeed existing at the time of the release affect the shape of the exposure rate isopleth curves, several sets of curves would be needed to represent the variety of stability conditions and windspeeds likely to exist at that site. The appropriate transparency can be selected on the basis of windspeed and meteorological conditions at the time of the incident. The transparency can then be placed over a map of the area that has the same scale as the isopleth curves such that the curves are properly oriented with regard to wind direction. The isopleth curves are 3The value of 1.5 for x is for average meteorological conditions. If the meteorological stability cooditica is known, it would be more accurate to use x = 2 for stability classes A and B; x = 1.5 for classes c and D; and x = 1 fo-classes E and F.
Revised 6/79 5.11 e
D l
used to estimate agosure este by plotting the escsun estes known at specific locations en the curves. F.gesure rates at ether locatic=s an simple sultiples of the known egesure estes as indicated by the multipliers associated with each curve.
A third alternative fcr determining egesure rate patterns is to obtzin ganna exposure rate measurements at a large number of locatiens and pict these data en a ssg of the area. This method would 7rovide the nost accurate data but would require a large number of radiation inst:uments and trained persens to make the measurements as well as a method for ccantunicating the data to the centrol center cc a centinuing basis. This sethod is primarily recocatended for developing informatica for determining the need to revise previous protective action roccantendations. Protective acticas for plume egooure should be taken price to plume arrival, it possible.
5.4 Dese P ofectica The projected dose (ce dose commitment in the case of iraaled l
l radiccuclides) seculd be calculated caly fer the early phase of an i
emergency. F.arly phase includes the curstien of the plume exposure fer inhalatico PACS and up to 2 to 4 days folicwing the accident for wnole body exposure. F.xposures that may have occurred before the dose projectica is made an not nor nally to be used for evaluatiras j
the need for protective actions. Radiatica doses that sight be l
t i
Revised 6/73 s
3.L2
~
received at later times following an accident also should not be included within the projected dose for this guidance. These latter doses, whicts may be from reentry operatices, food pathways, or long tem groundshine are committed over a longer time poried and will require different kinds of protective actions. *herefore, they will mquire separate guidance reconumendations to be addressed in Subsequent chapters.
The best method for early determination of the need for protective actices immtediately folicwing an incident and prior to the start of the release is for the facilf ty operator to estimate potential offsite dose based cc inferisation in the control rooc usi=g relationships developed during the planning stage that relate abnomal plant conditions and meteorological conditions to potential
^
offsite doses. After the release starts and the release rate is measurable and when plant conditions or instrumentation can be used to estimate the :haractaristics of the release and release rate as a functim cf time, geo they gtprs, al,ong wjtgetegrological conditicas and windspeed and direction, can be used with techniques presented here to estimate projected dese. Projected dose can also be detercined on the basis of environmental measurements when these are available. Procedures are provided herein to use either release rates or environmental measurements to project dose. Supporting documentatica fc? the procedures is provided in Appendix D.
I Revised 6/79 l
5.13 l
1 i
4
m 1
5.4.1 Duratien of Excesure Dose pmjection is a function of the time lategrated exposure rate er of the time integrated ccacentration. Although exposure rate would mest likely vary with time, this relationship cannot be predic ted. Fer purposes of these calculations, exposure rate is assumed to be ccustant over the expcaure period. Therefore, projected dose beccmes a product of exposure rate, duration of exposure, and a dose ccaversica factor.
The time period of exposure may be difficult to predict.
Exposun would start at a particuir
.e when the plume arrived and would be ended by a change in wind directim er by an end to the release. It is very important that arrangements be made fer the State er local weather forecast center to provide information en
~
current meteorological and wind ecnditiens and predicted wind directim persistence during the incidents in additicri *4 information received fmm the facility operator. If neither wind change nce the time until the end of the release can be predicted, the period of exposure could be conservatively assumed to be equal to the 995 probable maximum duratien of wind direction persistence i
l for that site and for existing meteorological stability conditicas.
Historical data en wind direction persistence as a function of l
atmospheric stability class for a particular site are available in the Final Safety Analysis Report prepared by the facility operatcr.
I Revised 6/79 j
5.14 l
l O
L-
5.4.2 } hole Body Dose Projection Having establisbad exposure rate patterns in the environment and having determined (e estimated) the time period of exposure, the next task is. to estimate the projected whole body and thyroid doce to members of the populatical so that the projected dose can be compared with appropriate PAGs.
An airborne release from a light water reactor would be expected to consist primarily of radioactive noble gases and iodines. If engineered safeguards operate as designed, they may reduce iodine concentrations to levels such that the whole body gamma radiation dose from noble gases will be the controlling pathway. Otherwise, the controlling pathway will be inhalation of radiciodines resulting in committed thyroid dose ranging up to m
hundreds of tines 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 recomumended that dose projection noeograms be developed, yigures 5.1 and 5.2 (pages 5.17 and 5.19) are examples of such nomograms. Appendix D provides details regarding their development. Other shortcut dose projection methods may have been developed by the facility operators that are fully as accurate as these methods and should be used if appropriate.
Revised 6/79 5.15 9
N, The projected whole body gama dose can be estimated by simply multiplying the gama exposure rate at a particular location by the time period of exposure. (The dose conversicn factor is assumed to r
be 1).
'igure 5.1 pmvides this multiplication. This figure also provides a relationship between exposure rate in 2R/hr and the noble gas concentration based en the :sixture of radioactive noble gases that would be expected to exist at about 4.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after shutdown.
If the coble gases have decayed for a longer time, these curves would signfficantly overesticate the projected dose as determined from concentrations and exposure time. If the gama expcaure rate from a semi-infinite cloud of airectne noble gases is to be determined from known sixtures other than those assumed, the following relationship may be uted:
n R = 9 x 10' I C,E, 1
where: R = expcsure rate (mR/hr) 3 C, a concentration in air (C1/m ) for radionuclide "n" E, 3 average gama energy per disintegration (.MeV) for radionuclide "n".
See table 31 of Appendix D fcc values of E for specific radienuclides.
? x 10' = a dimensicx21ess constant.
Rev:.sec 6/79 d
5.16
4
\\Nl l lllil o esZ m s c M
-1.0
) jg l
Flot the point representing gamma l e t I
radiation exposure rate (aA/hr) and
-7
\\
'N projected duration of exposure (hrs).
g-N\\
\\
Istimate the projected whole body dose
\\
\\
\\
from the ev vos above and below the X x q _ X point.
s s
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10 0.1
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.7 1
'2 4'
7 10 2.'O Ad 7'O 100 l
projected exposure duration (hours)
Figure 5.1 Projected wtmle body gamma dose as a function of gamrna exposure rate and projected duration of exposure.
t l
Revised 6/79 l
7 i
l 1
S is equatics is the familiar expressica fer gamma exposure rate frca a semi-inf*. nite cicud, R 3.25CE, with the units for R changed from h,sec to mR/hr.
5.4.3 S w dp Dese Prefectien Byroid dose ccamitment from inhalatica is pri=aril,y a function of the ccacentratiens of radicactive iodices in the air integrated
~
cver the duratica of expcaure. This sectica provides techniques for projecting the thyroid dese using a variety of types of data that say be available. S e bases for these techniques are provided in Appendix D.
N t,1 sic data,'conce b....% b t iodines in the air and s -
e p
tica dut?tien of expcaure, =ay bc. stained frca a fariety of Ocurces.
The concentration =ay be =easured either as g-ess iodines er as specific isotopes. The concentratica may also be calculated based en release rates and characteristics and meteorolegical conditices er based cas measured gn=ma exposum rates. Se duratica of exposure may be predicted as discussed in section 5.4.1.
Figure 5.2 provides a family of curves for projected thyroid dose as a functicn of airbcrne ecceentratien (right crdinate) and duratien of exposure (abscissa).
To estimate pro ected thyroid dess fe.- a particular site, plot d
the point en figure 5.2 correspending to the radicicdine ccncentratiens in C1/2 and the expected tine period of exposure fer persens at that 1ccatien. Using a icgarittmic faterpolatien, Revised 5/79 S.13 s
9
10' -
--7 x
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TO USE TE15 GEAFRa Flotthepointrepresenciastheexposurel 2-
- race or concentration and exposare time
'N
- 10.;
l and estimate the projected thyroid dose by interpolation.
- I-
.' ' ' e
-.- e : 10 10 e
e e
i a
e 0.1
.2 4
.7 1.0 2 34 7 10 20 30 Projected Exposure Time (Hours) t g
l l
Figurs 5.2 Projected thyrcid dose as a fu:iction of either gamma exposure rate or radiciodine concentration in air and the projected exposure time.
1 t
l l
3.19 Revised 6/80 e
m estimate the projected thyrsid dose f. A the dose values en the curves below and above the poist. For example, if the iodine concentration is 10 Ci/m3 and is expected te last two hcurs, thes the pzmjected adul* thytmid dose would be approxi=ately 6 mm, and the child thyroid dose would be approximately 12 rem. Note that the child thyroid dose is two times the.dult thyroid dese. The
~
child dose would apply to general pcpulaticas wnile the adult dose would apply to emergency tasas ce to other adults.
Dose conversim factors to ccnvert f.ma time integrated airborne concentratiens to projected dose would vary as a functica of the time after reactor shutdown that cencentrations were determined.
"he dose ccaversica facters fer icdire concentratiens used in figure 5.2 are based en a =ix of radiciodines that would be expected to exist at about 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after reacter shutdown. If the concentratice were determined at some other time, the dose conversica factor (acd thals the proje kted dose) would be in error.
This errer would be less than 305 for measurements =ade in the ra=ge of 1 to 12 hcurs as shown in figure 4.4 of Appeedix D.
Itis errer l
1s censidered too small to justify the use of a ccrrecticn facter, L
but figure 4.4 from Appendiz D cculd be used fer this purpose, if l
desired.
Air samples would provide the best source of cencontratico data f:r use in figure 5.2.
Ecwever, wits ; resent day equipment, field actsurements of envircewtal radiciodine eencentratiens may be Revised 6/73,
5.20 9
l
difficult and too time censuming fo* quick decisions en implementatien of protective acticas. In the absence of =easured iodine cencentrations in air, one may calcula*a the concentrations based on release rates and meteorological conditix.s or based on gama exposure rate measurements in the envirenment.
5.4.3 1 Concentratiens Based en Release Rates If information is available on the total curies released er nn the release rate and duration of release, one can use these data with meteorological informatien to calculate concentrations at specific locations downwind. Similarly, this information can be used to determine the dcwnwind distance at which a particular concentration would occur. These methods are discussed below.
U Figure 5 3 provides the atmespheric dilutice facter, X /Q, as a functice of downwind distance and fer different atmospheric stability classes. This factor is the concentration (x) in C1/m3 that would exist fcr an average windspeed (0) of 1 m/see and for a misase rate (Q) of 1 curie /sec. To find the downwind concentratica (x) for a specific windspeed and release rate, divide the value of X /Q by the windspeed in m/sec and multiply by the release rate in U
C1/sec.
To find the projected thyrcid dose associated with a particular concentration, find the point corresponding to the concentration and the estimated duratica of exposure en the nomegram in figure 5.2.
Interpolate logarithmically between the cose lines as necessary.
Revised 6/79 S.21
=
=
'\\
10'3 N
These values assume e
an inversion lid at 4
1000 meters altitude and a ground level e
release.
2 9
\\c 9 Y.
10 l
6 4
's 2
3 Y
i e
(
sk
\\,
10-5 4'd
~
6 s,
[
d 4
1 2 -
9 10-6 g
6 l
4.
1 2 e l
l 7
10~0.5 1
5 10 kilometers 100 l
1 s
s n
0.5 1
2 5
10 20 62 Distance Ocwnwind (Miles)
Figure 5.3 Typical values for %$/Q as a function of atmospheric stability class and dcwnwind distance l
5.22 s
l 9
If the release is expressed in total curies as opposed to Ci/sec, any release period can be assumed for purposes of using figure 5.2. to estimate the projected dese. Assuming a release period of one hour, the total release in curies can be converted to release rate in C1/see by dividing by 3600 sec/hr.
A more common problem may be to determine the downwind distance at which a particular dose wculd occur. The following steps would be appropriate for solving this problem.
~
1.
F.ma figure 5.2 (page 5.19) determine the icdine 3
concentration in C1/m that would cause tne thyroid dose of cencern for the estimated duration of the exposure.
2.
Multiply this ccacentration "X" by the windspeed "U" in m/sec and divide by the release rate "Q" in C1/sec. This provides a
.m dilution factor, xD/Q (m-2), which can be applied in figure 5.3 s._.
(page 5.22).
U 3
Using figure 5.3, follow the value for X /Q across to the existing stability class and follow this point down to find the corresponding distance. This is the downwind distance where the dose of concem should occur at the plume centerline.
Example Problem Assume an accident involves a puff release of 20,000 curies of iodines. The release occurs at two hours af ter reacter shutdown, the windspeed is 8 mph = 4 m/sec, and the atmospheric stability class is D.
Determine the downwind distance at which the projected dose would be 5 rem to the child tnyroid.
Revised 6/79 5.23
N Solutten Since no duratien of exposure was given, one can assume ene hour = 3600 seconds fer purposes of calculat.icns.
From figure 5.2 (page 5.19) note that the cencentration, X, corresponding to a 5 rem dese to the child thyroid frem a one hour 3
exposure would be about 3 x 10 C1/s,
The release rate, Q, can be assumed to be 20.000 euries = 5.5 Ci/sec 3,000 seconds
<sm. qq,
Therefore:
~0 3
f,3 x 10 C1/m x u /sec = 5.3 x 10-0 i m
2 Q
3 2 C1/sec From figure 5.3 (page 5.22) the distance corresponding to a dilutien factor of 5.8 x 10-6 g2 under stability class D is about 3 Is
~
cr 5 miles.
5.4.3.2 concentrations Based on Oamma Excesure Rate Measure =ents If envircemental cencentrations of radioicdines are determined from air samples at selected locaticns, it would be useful to obtain simultaneous average gama expcsure rate measurements at the sa=e locatices in accordance with recommendaticas of the Task Force en Instrumentatien (3,). The ratio of ga=a exposure rate to iodine Revisec 6/79 5.24 t
l
concentration should be approximately constant for different locations if the measurements are not spread out over more than about 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. The process of collecting and analyzing a few air samples and estimating concentratims based on gama exposure rate measurements at other locations could save considerable monitoring time.
If no air sample measurements.re available, it is possible to obtain a crude estimate of radicioc e air cencentrations from gamma exposure rate measurements. Because Jf the large potential for errors, this would be the last choice of methods for estimating airborne iodine concentrations.
The left ordinate in figure 5.2 (page 5.19) provides a relationship between the gama exposure rate from airborne i
radioactive noble gases plus iodines and the radiciodine v
concentration (right ordinate) that would contribute to this dose.
This relationship changes with the ratio of iodines to noble gases l
in the release, the atmospheric stability class, time after shutdown, the gama exposure coming from material already deposited on surfaces, and the gama exposure fmm airborne particulate 3
material.
Because of the assumptims that were made in the development of figure 5.2, its use to estimate thymid inhalation dose solely en the basis of gama exposure rates without confirmatory concentration Revised 6/79 5.25 i
a-w
,yw--e.-
--%e+.-,
-,w,.--,-,w w
iw
m measurements er without correction factors would generally result in projected thyroid deses higher than those that would actually occur. The relaticeships in ficare 5.2 between sama exposure rate and iodine concentration are based on the folicwing assumptions:
1.
The ratio of ceneentrations of iodices to noble gases would be about 0 3 which is the ratio that corresponds to a sixture consisting of 25% of the iodines and 100% of the noble gases in a nuclear power reacter at full power equilibrium conditiens. Figure
~
5.4 provides correction facters that can be multiplied times the gama exposure rat.a befoM its use in figure 5.2 in situations where actual values are provided for iodine to noble gas activity ratio.
2.
The atmospheric stability class would be "A".
Figure 5.5 provides correction factors as a functico of downwind distance and atsespheric stability class for use in situations where these data -
are known.
3 Measurements would be made within the range of 1 to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> af ter reacter shutdown. Concentrations based on seasurements
=ade during the first 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after shutdown would be slightly lower than estimated, thus causing a conservative dose estimate.
Concentraticas based en seasurements made 6 or scre bours after the l
reacter shutdewn would produce low dose estimates. Hewever, this
- cncenservative erece would be sczewhat ec=pensated by the censervative errer introduced by the assumpticn that there would be l
i t
.9evised 6/79 5.26 1
i
a
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tem y
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9 s
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. s
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10 USE TH4$ GHAPit u
o 3
f N
s
/
CORRESPONDING TO THE KNOWN g
2 F6NO THE CORRECTION FACTOR RAD 40 LOD 4NE/NO8t E GAS ACTIVliY O.0
,I
~
1
- RATE TO DE USED IN EsisteAisNG -
RATIO.neutTIPLY THet CORRECitON 7
FACTOR BY THE GA4eadA EMPGstNIE -
f' I
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THE PROJECTED TilVROtp DOSE 6
d IN FIGURE 5.2 j
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5.23 Revised 6/80
~
no contributien to gamma exposure, rate frca radiciodines deposited at the ground. Both of these errtrs would increase in intensity with time after the start of the release.
Caution should be exercised in this method of estimating thyroid dose to avoid projecting thyroid inhalation doses on the basis of gama exposure coming entirely from deposited material after the plume has passed. Fcr this situation the gama exposure O
rate would increase as the detector approached the ground.
Example Problem No iodine concentration measurements have been made, but gamma exposure rate measurements indicate maximum levels of 10 mR/ hour at 2 =iles downwind. The stabQ ity class is D, and the nuclear utility What reports the iodine to noble gas ratio in the release is 0.1.
is the projected child tnyroid dose for a 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> exposure?
Solution Referring to figure 5 2 (page 5.19) the projected dose without correction factors for 10 mR/hr and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> is about 8 rem to the child thyroid. From figure 5.5 (page 5.28) the correction factor for D stability and 2 miles = 1.6.
From Figure 5.4 (page 5.27) the correction factor for iodine to noble gas ratio of 0.1 s 0.45.
10 mR/br x 1.6 x.45 s 7.2 mR/hr. Referring to figure 5.2, the corrected thyroid dose is projected to be slightly more than 5 res for a 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> exposure.
Revised 6/79 5.29 O
5.5 Protective Actien tecisiens The most effective protective actions for the plume exposure pathway an evacuatim and shelter. Access control is also effective and appropriate but generally would be taken in ccnjunctice with cce of the other two acticas. When centamination of the skin is suspected, protective actions such as washing and changes of clothing are justified without the need fcr planned procedures because these acticns are easy to take and involve little e no risk. Chapter 1 provides a general discussica of protective acticas, and Appendix 3 vill provide planning guidance with regard to evacuation and shelter. ( Appendix 3 bas not been published as of this revisica).
After dose projecticas are made and ccnstraints are identified, respcasible officials must decide what protective actices should be implemented and in wtat areas. They must also decide which of *h emergency acticas that were take price to having release informatica fnm tM facility or env1.~:nmental sensurements shculd be expanded, saintained, ce canceled.
Table 5.1 provides broad guidance fer these decisiens en the basis of ecmparing pmcected doses to PAGs. This guidance is primarily fer planning purposes. Acceptable values fer emergency l
deses to the public under actual conditiens cf a nuclear accident cannot be predetermined. Protec'.ive actica recc=cendaticms in any icdividual case nust be based en the actual conditices that exist and are projected at the tine of the accident.
Revised 5/79 3.30 i
a
e Table 5.1 seacaended prutective sottone to reduoe whole body and thyroid dose free esposure to a geseous plume Projected Dose (Seel to the Population Beoompended Actionsfa)
Coemments h is body 43 No planned protective actione.Ib)
Freviously recommended State may issue an advisory to seek shelter and await protective actions may Thyreld
<5 further instruottons.
be reconsidered or Monitor environmental radiation levels.
terminate 1.
h ie body I to e5 Seek shelter as a minimum.
If constraints v11st.
Consider evacuation. Evacuate unless constraints make spoolal consideration Thyroid 5 to <25 it impractical.
should be given for Monitor environmental radiation levels.
evacuation of children Control access.
and pregnant women.
sa b le body 5 ene above conduct mandatory evacuation.
Seeking shelter would be U
Monitor environmental radiation levels and adjust erea en alternative if Thyrwid 25 and above for mandatory evacuation based on these levels.
evacuation were mot Control access.
tamediately possible.
Projected Dose (Rea) to Emergency Team Workers I
h is body 25 Control suposure of emergency team members to these Although respirators and levels except for lifesaving elssions. (appropriate stable lodine should be Thyrmid 125 controle for emergency workers, include time used where effective to llettations, respirators, and stable lodine.)
control done to 4
se I
seergency team workers.
[
h le body 75 control esposure of emergency team members performing thyroid dose may not be lifesaving missions to this level. (Control of time a lletting factor for of esposure will be most effective.)
lifesaving alastons.
en 3
(a)yhese actions are twoommended for planning purposes. Protective action dectetone at the time of the incident must take estating conditions into conalderation.
(b)At the time of the inoldent, offlotale may implement low-lapact protective actione in keeping with the prinolple of maintaining rsdiation esposures se low as reasonably aohlevable.
A
PACS cannot be used to assure that a given level of exposure to ir.dividuals in the population is prevented. In any particular response situation, a range of doses may be experienced, depending
)
i l
mcstly m the distance from the point of release. Sese of these
=
l doses may be in excess of the PAG 1evels and clearly warrant the initiation of any feasible protective actions. This does not mean, however, that all doses above PAG 1evels can be prevented.
Furthermore, PAGs represent caly trigger levels and are not intended to represent acceptable dose levels. PAGs are tools to be used in plaming and as decisim aids in the actual response situation for purposes of dose savings.
Under emergency conditions all reasonable measures should be taken to minimize raciatim exposures to the Zeneral public and to emergency workers. In the absence of significant constraints and in censideratice of the generally accepted public health practice of limiting radiatim exposures to as low as reasonably achievable i
i levels, responsible authorities may want to implement low impact protective acticca a pmjected doses belcw the PAGs.
The recomendations provide a range of PAG values bracause
[
implementation of the guidance will al.-ys require the use of good l
judgment and a considerstica of local ccastraints. ne icwst value should be used if there are no major local ccnstraints in providing protectim at that level, especially to sensitive populaticas.
ReviJed 6/79 5.32 s
Local ecastraints say =ake icwer values impractical to use, but in no case should the higner value be exceeded in determining the need for protective action. The questim inevitably arises, then, at what projected dose below the minizan PAG values should protective actions no lenger be considered. This is a value judgment en the i
part of the emergency coordinator but should be based on the following considerations:
Are the risks associated with taking protective actica at a.
low projected deses greater than the risks associated with the icw projected radiatien doses?
Is there a reasonable probability that the protective b.
action being censidered can be successfully implemented without unreasonable ecst er hardsnip on the participants?
At very low projected deses, efferts to protect the c.
- y..-
population say do scre bars than good.
The intent is to allow fcr flexibility in the implementation of the guidance because local conditions will vary and because special
.w& 4 mf orsar.ico say be available. But above the upper PAG range, there is significant risk to *he exposed populaticris, and responsible t
agencies should consider it sandatory to plan to implement effective protective actims, recognining that when an accident actually occurs, unfereseen conditions or constraints may prevail such that l
l professional judgment will be required with regard to priorities fer protecting the pud 1ic.
Revised 6/79 5.33
.~
\\
~
Guidance for emergency workers is given as dese limits because it is recognized that critical civil functions mat continue while protective actions are taken for the genersi population, and this say require emergency workers to receive radiation exposures during emergencies that otherwise would not be permitted. Exposure of emergency workers to any aose level iJ not justified unless it is determined tnat benefits to society are being achieved and efforts
~
are being made to limit their doses to levels a:: ice as reasonably i
achievable. Emergency workers should coelist of healthy adults and should not include women that could potentially be pregnant.-
Emergency response planning should provide for specialized protection for emergency workers during energency activities. This would include respiratory protection, if needed, to reduce internal organ and thyroid doses fram inhmiation and perhaps prophylactic drugs that prevent thyroid exposures from inhaled radiciodine.
There should be appropriate instrumentation to verify exposures and comununication techniques to prevent overexposurbs by warning emergency workers when to withdraw frca radiation fields.
I The health risk associated with dose limits recommended for lifesaving missions are extremely hig% and such high doses should be received only on a voluntary basis by individuals aware of the
~
risks involved. Literaving actions should be performed by persons I
in good health whose normal duties have trained them for such missions.
i i
Revised 6/7o
/
5.34 e
,..---,--_,+,,nn,._,..,
REFERENCES (1)
U.S. NUCLEAR REGULATORI CCMMISSICN. An Assessment of Accident Risks in U.S. Commercial Nuclear Power Plants. (WASH-1400),
~
U.S. Nuclear Regulatcry Commission, Washington, D.C.,
October 1975.
(2)
U.S. NUCLEAR REGULATCRf CCMMISSION. Guide and Checklist for the Development and Evaluation of State and Local Government Radiclegical Emergency Response Plans in Support of Fixed Nuclear Facilities (WASH-1293).
U.S. Nuclear Regulatory Ccamission, Washington, D.C.
December 1974.
(J) HANS, JOSEPH M., JR., AND THOMAS C. SELL. Evacuation Risks -
an Evaluatien (EPA-520/6-74-002).
U.S. Environmental Protection Agency, Washington, D.C.
June 1974.
Q) NELSCN, 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).
Q)
U.S. ATCMIC ENERGY CCMMISSION. Regulatory Guide 1.3 Assumptiens Used for Evaluating the. Potential Radiological e
Consequences of a Loss of Coolant Accident for Boiling Water.
Reactors. Directorate of Regilatory Standards, Nuclear Regulatory Constission, Washington, D.C.
June 1973 v'
(6)
U.S. ATCMIC ENERGY CCMMISSION. Regulatory Guide 1.4.
Assumptions Used for Evalua, ting the Potential Radiological Consequences of a Loss of Coolant Accident for Pressurized Water Reactors. Directorate of Regulatory Standards, Nuclear Regulatem Connnission, Washindton, D.C.
June 1973 Q)
U.S. NUCLEAR REGULATCRT CCMMISSIUN AND U.S. ENVIRONMENTAL PROTECTICN A M CT.
Task Force Report. P M e %g. Basis for the Develcpment of State and Local Government Radiological Emergency Response Plans in Support of Light Watsr Nuclear Power Plants, NUREG-0396 or EPA-520/1-78-016, Washington, D.C.
20460, November 1978.
@)
U.S. NUCLEAR REGULATORY CCMESSICN. Interim Guidance on Offsite Radiation Measurement Systems, A Report to Developers of State Radiological Emergency Response Plans by the Feceral Interagency Task Forcs on (offsite) Emergency Instrumentatica for Nuclear Incidents at Fixed Facilities, U.S. Nuclear Regulatory Commission, Washington, D.C., August 1977 Revised 6/79
f CHAPTER 6 Application of PAGa for Foodstuffs and Water Contamination 6.1 Eslocation 6.1.1 Whela Body 6.1.2 Organ Exposure 6.2 Shalter 6.2.1 Whole Body 6.3 Access Control 6.4 Milk Control 6.5 Food Control u
6.6 Water Control l
l (Guidance to be Developed) i a
e 6.1
. _=.
i CHAPTER 7 Application of PAGs for Cone==4nated Property or Equipment 7.1 Release and Reentry 7.2 Decontamination 7.3 Land Use e
1 (Guidance to be Developed)
/
d l
e.9& 4
%%j. f_ m *.i e
7.1
CHAPTER 8 Application of PAGs for Transportatica Incidents (Guidance to be Developed) r i
e e
O O
O 8.1
APPENDIX A Sumary of Interim Guidance on Offsite Emergency Radiation Measurement Systems (to be developed)
A.
' w. '
e 9
6 se*
A-1 l
a APPENDIX B
^
Planner's Evaluation Guide for Protective Actions (to be developed)
S
%d e
e t
1 I
I l
t l
l l
B-1 l
APPENDIX C Summary of Technical Bases for Protective Action Guides (to be developed)
O V
l 8
(
l I
i C-1
{
/
APPENDII D to the Manual of Protective Action Guides and Protective Actions for Nuclear Incidents 3 CHNICAL BASES FOR DOSE PROJECTICN ME 30CS r
January 1979 v
Environmental Protection Agency Office of Radiation Programs Environmental Analysis Division Washington, D.C.
20460 S
e e
,nn-,---
/
Contents 2 ate
? m nical Bases for Methods that Estimate the Projected Thyroid Dose u.a Projected Whole Body Gamma Dose from Exposure to Airborne Radiciodines and Radioactive Noble Gases................. D-1 1.0 Introduction............................ D-1 1.1 Approach............................ D-3 2.0 Units................................ D-6 2.1 Radionuclide Concentration in Air............... D-7 2.2 Dose Calculations
..................... D-11 2.2.1 Whole Body Cloud Gamma Doses.............. D-11 2.2.2 Thyroid Inhalation Doses................ D-15 2.2.3 Finite Cloud Correction................. D-22
, '-~' 3 0 Input Parameters
..................... D-24 31 Radienuclide Source Terms................... D-24 3.2 Thyroid Dose Conversion Factors for Radiciodino Inhalation... D-27 3.2.1 Dependence of Thyroid Mass and Breathing Rate on Age D-28 3 2.2 Uptake of inhaled Radiciodine into the Thyroid..... D-30 323 Effective Decay Energies of I-131, I-132, I-133.
I-134, and I-135 in Erman Thyroid............ D-31 3 2.4 Effective Decay Constants of Iodine Isotopes I-131 through I-135 in the Human Thyroid as a Function of Subj ect Age....................... D-35 i
3 2.5 Dependence of Thyroid Dose Conversion Factor cn Age... D-39
\\
4.0 Results............................... D-39 4.1 Whole Body Dose
.................... D 43 4.2 Thyroid Dose.......................... D 45 i
9
Contents (continued)
Page 5.0 Accuracy of Dose Projection Methods.
. D-61.
5.1 calculational Errors Associated with Release Race Assumptions
. D-61 5.2 calculational Errors Associated with Assumptions on Release Characteristics
. D-62 5.2.1 Errors in Whole Body Dese.
. D-6 2 5.2.2 Errors in Thyroid Dose
. D-63 5.3 Errors Associated with In7ut Data
. D-64 5.3.1 Duration of Exposure
. D-65 5.3.2 Errors in Release Race Data..
. D-65 5.3.3 Errors in Data on Release Characteristics.
. D-66 5.3.4 Errors in Environmental Measurements and I'sformation
. D-66
. D-67 5.4 Summary References................................ D-69 l
+
I
(
r r
l 11-l
\\
Tables
/
2.agg Section 3 31 Radionuclide source data.................... D-25 32 Body mass, thyroid mass, and breathing rate as a function of age............................. D-29 33 Abscrbed fractions (4) in the thyrcid as a function of age and iodine isotope
..................... D-36 3.4 Effective decay ener:1es for I-131 through I-135 present in the thyroid as a function of age.................. D-37 3.5 Effective decay constants of I-131 through I-135 in the human thyroid as a function of age.................. D-38 3.6 Thyroid dose eenversion facter as a function of age and iodine isotope..
......................D40 Section 4 4.1 Noble gas and iodine inventory in the reacter core and containment as a function of time................ D-41 4.2 Iodine to noble gas activity ratio as a function of iodine v
release fractim and time after shutdown............ D 42 4.3 Ratio of noble gas gamma dose rate to noble gas concentration, RGC", as a functice of time after shutdown........... D A4 4.4 Ratio of a child thyroid inhalation dose to radiciodine concentration, RIC, as a function of time after reactor shutdown at whi h exposure begins and the inhalation exposure
...................... D 37 duration [C1/m 3
\\
4.5 Radiciodine concentration in air which would result in a 5 rem thyroid it alatim dose to a child as a function of time after h
reactor shutdown, ta,3).....posure begins and the................ D 49 at which ex inhalatim time (Ci/a 4.6 Ratio of iodine concentration to total iodine and. noble gas gamma dose rate as a function o iodine release fractica and time after shutdown Ci/m3
................ D-53 Yest nr Section 5 5.1 Estimated errors associated with dose calculatica nethods.... D-68 111
<~
G
Figures Page Section 3 3.1 Radiciodine and noble gas decay chains
. D-26 Section 4 4.1 Projected whole body gsassa dose as a function of gasuna radiation dose rate and projected time period of exposure.
. D-46 4.2 Five res isodose line for child thyroid as a function of radiciodine concentration at the start of exposure, exposure duration time and time af ter shutdown at which exposure begins, t
. D-50 a
4.3 Projected thyroid dose as a function of either gasmaa exposure rate or radiciodine concentration in air and the projected exposure time D-54 4.4 Correction factors for thyroid inhalation dose as a function of time af ter reactor shutdown that radiciodine cencontration is measured.. D-56 4.5 Canma exposurs race finite cloud correction factor
. D-58 4.6 Radiciodine release correction ractor.
. D-60 l
iv
/
l.
l l
l
Appendix D Technical Bases for Methods that Estimate the Projected Thyroid Dose and Projectec Whole 3ody Camma Dose from Excesure to Atraorne Raciotoctnes anc Radioactive Neole Gases 1.0 Introduction If an incident were to occur at a reactor resulting in mobilization of the fission product inventory, the radioactive isotopes of iodine and the noble gases plus a smaller quantity of O
particulates might be released to the environment in quantities exceeding normal operating limits. Under these conditions, it would be necessary for responsible public officials to quickly determine whether protective actions should be taken to protect the public.
The decision to implement protective actions would be based, in part, en the projected radiation dose that might be received by
,_s individuals in the population. Dose projections may be determined from one of three information bases or ecubinations thereof:
(1) reactor system status, (2) release race of radioactive materials, and (3) environmental measurements. Dose projection l
based on reactor system status will be primarily the responsibility of nuclear facility officials and will not be discussed here. The I Projected radiation dose is defined as the dose the exposed persona would receive in the absence of protective actions and includes couaitted dose that may be received as a result of ingested or inhaled radioactive material.
e
{
l1.,.-
'N estimation of projected dose based on release races and environmental measurements will to some extent be the responsibility of State and local gover= ment officials. Procedures for making these estimates were given in Chapter 5, and this Appendix provides the technical bases for those procedures.
Two exposure pathways are considered: (1) whole body gasuna exposure from radioactive noble gases and iodines in the plume, and (2) inhalation of radiciodines in the plume. Additional whole body external exposure would occur from deposited radioactive particulates and iodines. Over an extended period of days to weeks or months this source could be significant or even dominant.
However, during the period of plume passage, exposure from deposited materials is not expected to be significant compared to exposure from the plume. Therefore, separate procedures for estimating the whole body dose from deposited materials are not provided in this I
i Appendix.
The environmental measurement techniques considered are ganmaa exposure race measurements and gross radiciodine concentration measurements. Methods are developed for estimating the projected thyroid dose conniement from either of these measurements. Although the estimation of thyroid dose commit:nent from gamea exposure rate measurements is recognized as a crude approximation, it is a currently implementable and rapid method. Field instrumentation
/
D-2
/~.
capable of measuring gross radiciodine concentration in the presence of noble gases is under development. This method should replace or
~
supplement the gamma exposure rate method for estimating projected thyroid dose commitment as soon as possible. Projected whole body gamma dose from external exposure to the plume is simply the integral of dose rate over the duration of exposure.
1.1 Accroach Calculated values for projected thyroid dose consaiement and projected whole body dose are a function of the isotopic composition of the radionuclide bearing cicud. This cloud composition is, in turn, determined by the respective release rates of specific radiocuclides from the reactor containment and the age of the e
fission products. In addition, tha projeccad dose from inhalation among human receptors will vary as a function of the pertinent l
physiological and metabolic characteristics ascribed to the l
l individual incurring the dose.
Given sufficient time, one could project the thyroid dose commitment by measuring or calculating the airborne concentration of each isotope of radiciodine, integrate these concentrations over the period of exposure, multiply by the appropriate dose conversion factor for each isotope, and then sum these values. However, during the emergency period following an incident, such analyses would be too time-consuming, and more simple methods must be used.
D-3 L
~
ne recommsended simplified approach for dose projection is to make use of charts er nomograms to translate calculated or measured environmental parameters into estimated projected dose. Estimating the whole body external dose is caly a matter of integrating the gamma exposure rate over the estimated duration of exposure. De corresponding method for projecting thyroid dose is similar with the addition of factors to convert f ca time integrated concentration to dose and correction factors to adjust for variables that may be known.
2is Appendiz is a presentatica of the processes and assumptions used to develop nosq.. ens for projecting both thyroid inhalacion dose coussiement and whole body gammaa dose. De nomograms are based on releases defined for a design basis accident without the benefits of engineered safeguards to reduce concentrations in containment. Correction factor charts are provided for adjusting the dose projections for (1) different release characteristics, (2) time for radioactive decay, and (3) actual meteorological conditions at the ti:ne of the accident. Other methods involving different types of charts and nomograms for projecting dose have been developed by nuclear facility operators and others. Such methds may be fully as accurate and acceptable as those developed in this Appendiz.
D-4 J
e
,~.
The charts and nomograma developed in this Appendix allow one to quickly estimate projected whole body dose or projected thyroid dose commaitment from any of the following data when these data are
~
used with the estimated duration of exposure:
i Whole Body Profseted Dose i
1.
Calculated gross concentrations of iodine and/or noble j
gases.
2.
Measured gamma exposure rates.
Thyroid Dese Ccamitment 1.
Calculated gross concentration of iodines.
2.
Measured gross concentration of iodines.
3 Measured gamma exposure rate.
^.
Because the dese projection comograms (1) are based on gross f
'v concentrations, (2) consider only a specific time for radioactive decay, and (3) do not consider differing dimensional characteristics of the plume, the resulting dose projections are subject to gross errors. However, the methods are based on generally conservative v.N& 4
- C: m ~ -
assumptions, and therefore, the dose projection errors are likely to be conservative. Correction factor curves are provided for use in situations where actual data are available to substitute for these assumptions so that dose projection estimates can be more accurate.
D-3
2.0 Units All radiation units used are those defined by the ICRU (1).
However, the ICRU has yet to define the concept of dose commitment and propose a symbol for it even though the ICRP utilizes the ConcepC.
Richardson (2,) has traced the history of the dose conniement concept; the following definition is taken from his work. "Dese Coussiement is a future dose implied by a specific event in the past."
Mathesacically, this concept is defined by the following integral equation:
t "o[
D,(t)de (1.1) 3=
m where D is the dose coussitzent in rad and D, is an inicial or reference dose rate.
As shown here, dose conumitment and dose rate are averages.
9
-l These average value(s) result from application of the assumption that radioactive material is deposited uniformly throughout the target organ.
I will be determined by the values selected for the limits of integration. The lower value, c,, is taken as zero which defines a reference time or starting point at which time a value for D, is known. The ICIP has suggested upper limits of 50 years as the value D-6 s'
6
.-..,,-.,-~,.
,.a-
m b
to be used for, occupational considerations and 70 years for mem ers EPA uses 100 years Q) when computing of the general public.
In selecting an upper limit for use environmental dose connaiements.
in calculating the dose couitments correlated with iodine concentration, it is recognized that due to the short half lives for
_~
to the the radiciodines of concern, most of the dose comeitsent Therefore, the thyroid will be delivered in less than one month.
difference in dose delivered in 50 or 100 years or infinity is The effectively 0, and infinity is used for convenience.
calculational formula becomes:
~
g (1.2) f D,e" dc = f D=
,m O
e v
1, is the effective removal coefficient in reciprocal time units.
Radionuclide Concentration in Air _
2.1 The air concentration of fission products downwind from the point of release is determined by their rata of release from the reactor contaitunent, their manner of dispersal in the atmosphere, yor a given inventory and the elapsed time since reactor shutdown.
of radionuclides in the reactor core at the time of shutdown, the containment release rate of a particular radionuclide depends on (1) the fraction of the core inventory of the three factors:
D-7 F *e
/
9
nuclide which is released to the containment; (2)"the rate of its removal from the containment aczosphere by the engineered safety systems and by such mechanisms as precipitation, surface deposition, and radioactive decay; and (3) the containment leakage rate. These three factors can vary widely depending on the magnitude of the accident and the functional status of the engineered safety systems. 'Hewever, if one assumes that a given fraction of the core inventory of a specific radionuclide is available for release to the containment i:mnediately after reactor shutdown (4,5) and that the engineered safety systems act to reduce the containment inventory of the radionuclide by some fixed factor within a short time after the radionuclide release into containment, then the analysis of the radienuclide release frem the containment can be simplified. Under those assumptions, the removal of a radionuclide from the containment atmosphere by the engineered safety systems can be i
j regarded as an additional barrier, or filter, affecting the fraction of the core inventory of the radionuclide which is released to the c ontainment. If F is the fraction of the core inventory of the ik kth radionuclide which is released to the containment, F is the 2k l
fractien of the released radionuclide which is not removed by the engineered safety systems, and A., is the activity of the keh l
radionuclide in curies, then the containment inv..cory of the kth radienuclide at time e, C (c), is given by k
l l
D-C
-j l
i l
- A (*}
""#I'**
(2*1}
C (t) = F k
ik 2k k
Combining the product of F and F I"*
- * **l #*l****
ik 2k fraction F 'k C (c) = F A.(t) curies.
(2.2) k k
Assuming that 100 percent of the containment inventory is available for release to the environment via containment leakage, the radionuclide release rate from the containment is determined by the product of the radionuclide core inventory, its total release fraction, and the containment leakage rate. In these terms, the r
release rate from the containment of the kth radionuclide may be
~w written as:
d(c')-A(*'}
r
- L(*'}
(2*3}
i g
k k
where:
d(c')=containmentreleaserateofthekthradionuclide k
(Ci/s) t' = time of release after reactor shutdown (s) time c' (Ci)
A.g(c') = core inventory of kth radionuclide at T = total release fraction of the kth radionuclide k
L(c') = containment fractional leakage rate at time t' (s" ).
D-9 l
l l
After the fission products have been released to the environment, their concentration, as a function of downwind distance, is dependent on the atmospheric conditions at the time of release and on their respective deposition velocities. However, if the deposition velocity of the radionuclides is neglected and the containment leakage rate is assumed to be constant, the air concentratica of the keh radionuclide is given by the following equation:
4m u
-. m g* % 3.;
o X.,(r,t)=h(E)*/(#}
k
=A.(t)
F L
X/4(r)
(2.4) sc k
where:
X, (r,t) = concentration of keh radionuclide at point r relative to the point of release and time e after 3
reactor shutdown (Ci/m ).
X/d(r) = time invariant atmospheric diffusion function relative to the point of release (s/m ), and A., is evaluated at the same time as Xk ** *11
- f*'
~
fission product decay and ingrowth during time of flight.
D-10
/
9 8 e
The total radionuclide concentration of a cloud consisting of M cadionuclides is given by the stan of concentrations of its individual components. Thus, l
H l
x(r c) = I A (t) F k II (#)
g k
l k=1 M
= L x/k(r) k=1,(t)F I A.
(2.5) k 2.2 Dose Calculacions The dose projection methods developed in this Appendix are limited to consideration of thyroid doses due to inhalation of
^-
radiciodines and whole bo'dy cloud gansna doses duc to radioiodines i
and noble gases which might be released in a potential nuclear w-reactor accident. Deses to other organs are not considered.
2.2.1 Whole Body Cloud Cannas Doses The cloud gamma dose is a dose which is received as a
- WiA.. *: w.-
m.A consequence of external exposure to gsama radiation emitted by the airborne radioactive fission products. In some cases, the whole body dose would be projected based on measurements of exposure race in the environment and an estimated duration of exposure. In other cases, projected whole body dose may be based on. calculated concentrations in the environment and estimated duration of exposure. Sinca ganmaa rays can travel great distances in air, p.11 9
calculations of whola body gasma doses from airborne concentrations must consider the radionuclide composition and concentration special distributions within the cloud. Rigorous calculations of cloud gamma doses require three dimensional integration of appropriate dose attenuation kernels with respect to space, as vall as with respect to time. However, if the cloud can be considered to be semi-infinite in excent (reference (6), section 7.4.1.1), then, for a point located on the ground, the ganana dose rate in air from the kth radionuclide is given by 5[,(r,t)=0.25I.[X.,(r,t)
(2.6) m where:
5[(r,t)=gasssadoseratefromthekthradionuclide distributed in a semi-infinite cloud (rad /s)
( = average gasma energy per disintegration of the keh radionuclide (MeV/ disintegration), and X.,(r,t),
which has been defined previously, has the units of Ci/m.
Using Eq. (2.6), and assuming that the whole body gasma dose rate is equal to the gsama exposure rate in air, cue could calculate the whole body gasmaa dose that would be received by an individual
./
D-12
?
[
exposed to an infinite cloud of gaseous fission products by integrating the dose rate with respect to time over the duration of
~
exposure. However, since it is expected that the cloud ganmaa exposure rate would be measured at a given location within a short ti:ne af ter plums arrival, the dose at that location can be conservatively estimated by simply multiplying the measured gaussa exposure rate by the expected duration of exposure. This dose projection method would tend to be conservative because the radiological decay of the fission products after the measurement would be neglected. Other factors such as changes in plume direction, changes in meteorological conditions, or changes in release raci could cause either high or low dose projections.
c 5
\\
A method cad also be developed for projecting whole body gammaa doses b.ssed on known"or calculated fission product concentrations.
l Since th gasuna dose rate from a semi-infinite cloud consisting of M l
l gaseous fission products is equal to tite stan of the doses from the l
various rahionuclides, the total whole body dose rate is defined by:
4 bk=1((r,t) 6 P(r,t) =
M 0.25Y.[x(r,t) rad /s.
(2.7)
=~:
k kal i
i i
D-13 l
4
/
Since X.,(r,t) is given by Eq. (2.4), substitution of that expression into Eq. (2.7) yields the fe;1owing:
M 5 (r,t) = 0.23 k=1, A.,(t) 7., L X/d(r)
- E M
k=1(A(t)E I2 rad /s.
(2.8) 0.25 L X/q(r)
=
g k
Furthermore, since the total radionuclide concentration at s
(r,t) is given by Eq. (2.5), the ratio of the semi-infinite cloud grama dose rate to the total radionuclide concentratien, (RGC"), is given by M
0.25LX/d(r) IY(A.,(t)T,,
RGC"(t) =
3 LX/d(r) r A (t) F g
g k=1 M
k=1[A.,(t)T,g E1 0.25 rad /see (2.9) bA.
Ci/a
^
k=1,(c) Fk Thus, given a knowledge of gaseous fission product concentration at a given location soon ef ter plume arrival, the whole body cloud gamr.? dose to en individual at that location may be projected by multiplying the concentration by the factor' RCC"(c) and s
D-14 k
6
by the expected duration of exposure. This method may also be used to project whole body cloud games doses from noble gases which might 4
be released in a reactor accident.
2.2.2 Thyroid Inhalation Doses The thyroid inhalation dose is an internal dose cousaitment which is received as a consequence of inhaling radiciodines present in the air at the point of exposure. (The term inhalation dose or l
thyroid dose as used in this report means thyroid dose cousaitment.)
The inhalation dose due to the exposure to air containi.s the keh iodine isotope is given by the integral of the concentration over the period of exposure, r
- y. -
t, + t, (r t, t,) =
DCy X (r c) de (2.10)
E D
e k
l t,
l i
where:
D (r,t,,t,) = thyroid inhalation dose resulting from k
exposure to the keh iodine isotope (rad) e, = time after reactor shutdown at which exposure causences (s) 1 e, = duration of exposure, or the inhalation time (s)
DC7f=thyroidinhalationdoseconversionfactorforthe kth iodine isotope,
, and X(r,t) 1se been Ci/m l
defined previously.
n-u I
i
1 If the radiciodine concentration in air is composed c f N iodine isotopeJ. then the inhalacion dose is equal to the sta of the doses received from inhaling the individual iodine isotopes. Thus, the combined dose is N
D"h(r.e,,t,) = k=1(h,,,
I g
,)
t, + t, p 4, i -
.., y y. % at; DCF,'th X(r,t) de rad.
(2.11) i
=
r k=1
'a Substituting the expression for X,,(r,t) from Eq. (2.4) into Eq. (2.11), one obtains t, + t, N
D* (r,c,,c,) =
DCF,f A.,(c) T L X/ (r)dt I
k k=1
'a e, + t, N
=LX/d(r) I
- DCF, A.,(t) F.,de rad.
(2.12) k=1 c,
d D-16 e
The ratio, RIC(t,,t,,t,), of the combined thyroi/
inhalacion dose, D(r,t,,c,), to the total radiciodine concentration, X(r,t,), at point r, and time t,, where e, < t, < e, +
t,, can be obtained by dividing Eq. (2.12) by Eq. (2.5).
It esa be vricten as t, + t, N
L X/Q(r) I DC7 A (t) F de kg k
k=1 RIC(t,,t,,t,) =
3 L X/Q(r) E F A (E )
kk c k=1 N
['
E DCF I A (t) de k
kk k=1 sv a
rad gg,g3)
=
F A (E }
kk c k=1 S
I Since RIC(t,,c,,t,) is the ratio of thyroid inhalation dose to radiciodine concentration, given a knowledge of the total radiciodine concentration at a given location, at time t, after reactor shutdown, one can project the thyroid innalation dose resulting from an exposure beginning at c, seconds after reactor shutdown, and lasiing for a period of t, seconds, by simply multiplying RIC(t,,t,,t,) by the known radiciodine concentration.
D-17 e
Expressed nathematically, D( r, t,, c,) = RIC( t,, t,, t,)
X (r, t,)
rad.
(2.14)
Since RIC(t,,c,,t,) is independent of position, this procedure may be used anywhere within the tadioactive plume, provided that the total radiciodine concentration in air is determined at the location for which the thyroid inhalation dose is projescted, and that the temporal parameters t,, c,, and t, are known.
Using a similar method, it is also possible to estimate projected thyroid inhalation doses on the basis of environmental measurements of cloud gamma dose races. To do this it is necessary to develep a relationship between gamma dose rates and iodine concentrations in the plume and then to use this to determine the projected thyroid dose.
If the gaseous fission product concentration at a given position is composed of N radiciodines and M noble gases, then the ratio of total iodine concentration to the semi-infinite cloud gn===
dose rate, IIG"(t), is given by N
J A.(t)F (2.13)
RIG"(t) =
=
1+.4 ractsec Uy=(#' )
I.[A.(t)7.,
0.25 :
a=1
/
D-13 e
Since the ratio of thyroid inhalation dose to radioiodine concentration is given by the factor RIC(t,c,,c,), the thyroid inhalation dose
~
rad.
(2.16)
(r,t,,c,) = (RIC(c,,c,,t,)
RIG"(t,)}
- 6Y*(r,t )
E D
g e
Thus, if the time that has elapsed since reactor shutdown is known, the radiciodine thyroid inhalacion dose can be projected at a given location for an expected inhalation period by measuring the cloud gamma dose rate at that location and by multiplying it by the expression in parentheses in the above equation.
A While the factors RIC and RIG were expressed as functions of w.-
radionuclide core inventories and, release fractions, in view of Iq. (2.4), it should be recalled that they are actually functions of I
Sinca the fission product release rates from the containment.
release rate of the kth radionuclide from the containment is given by 6 (c'), the factor RIG, in particular, can be expressed in k
terms of release races as N
kIC}
i (2.17) t=1 RIC"(t) =
gg l(g 4g(t) 0.25 :
l k=1 l
l l
D-19 1
e
s or, in terms of containment radiciodine and noble gas inventories, as N
I c (t) g RIc"(t)
- i"l (2.18) 3,3 Y c.,(t) 0.25 I g
k=1 where6,,andc are evaluated at eine t to allow for g
radiological decay during time of flight.
Defining the average gamma energy released per disintegration of a radioicdine atom to be N [gd(t)
I g
f(t) = i"1 I
- s I k(t) g i=1 and the average ganna energy released per disintegration of a noble gas accm to be M
I I h (t)
< (t>, 4-1 j
~Na n
Q)(c)
E J-1 J
D-20 e
Eq. (2.18) may be written as N
I Q.(t)
- la 1"I aIc"(t) =
3 3
6(t)+Q(t) 4)(c)
Y I
Y (t),I t
g z=1 3-1 (2.19)
=
M Q)(c)
I I (t) +
g(t) y 3
I Qg(t) i=1 Eq. (2.19) illustrates the obvious fact that the ratio of p
iodine concentration to gasssa dose rate depends on the relative
,w.
release rates of the iodines and noble gases from the reactor containment or, asstasing a radionuclide independent containment leakage rate, on their relative inventeries in the containment.
Thus, in order to be able to project thyroid inhalacion doses on the basis of cloud gsamma dose rates, it is only necessary to know the relative containment release rates of radiciodines and noble gases and not their absolute magnitudes. Furthermore, since release from the containment would reduce the radiciodine and noble gas inventories by the same fractional amounts, their depletion by leakage into the environment need not be considered in assessing their relative release rates.
l l
D-21 e
L
~
2.2.3 Finite Cloud Cor-m:tien The above =ethod for projecting thyroid inhalation deses by measuring cicud gamma dose rates was based en the assumption that the cloud is semi-infinite in extent. Ifewever, for a particular concentratica, the actual gama dose rate from a finite plume would tend to be s= aller than that frca an infinite cloud. Thus, projections of whole bcdy gamma deses based en calculated radienuclide concentraticas in the plume would tend to overestimate the doses. Ccnversely, projectices of thyroid inhalatica doses based en measurements of gasmia dose rates would tend to toderestimate the inhalatien doses because of reduced gar.ca dose rates.
The ratio of gamma dose rate in a finite cloud to the gama dose rate in an infinite cloud having the same concentration as the centerline.cf the finite cloud for 0.7 MeV gannia photons is shown in figure 7.14ofreference(1). It depends only slightly on gamma photon energy and may be assumed to be valid for the gamma energy spectr*.mt of radiciodines and noble gases.
- his ratio is plotted as a function of e, the standard deviation of the cloud concentration for the cloud centerline and fer locatiens off the centerline. For a ground level release, the value of a can be replaced by e average which is (c o).
Figures 3 10 and 3 11 of reference (1) 7 g
provide values for e and o as a function of downwind distance y
g D-22 e
for the Pasquill stability classes A through F.
The resulting valites for o can be used in figure 7.14 of reference (6) to determine the ratio of the gasma dose race in a finite cloud to the gassna dose rate in a semi-infinite cloud for the different stability classes and at different downwind distances.
This functional dependence can be expressed mathematically as a
$T (2.20) g (o, x, KK)
D where:
fY e
~
7 = ratio of gasma dose race from a finite cloud to that from an infinite cloud i
x = downwind distance of exposed location from point of release i
KK = atmospheric stability class (A, 3 C, D, E, or F) e = average radionuclide concentration standard deviation.
f 3y dividing the measured cloud gasma dose rata by the ratio y
s,-
, or by multiplying it by its inverse, 7, one c.2n compensate D
D for the reduced gasma dose rate from a finite cloud in projecting radiciodine thyroid inhalation doses based on environmental measurements of gasma dose rates in air.
~
>U e
~
i
~
30 Input Parsneters 3.1 Radienue11de seure Terms Table 3.1 gives the fission product source inventory and associated data which was used in this Appendix to develop whole body and thyroid inhalation dose p.Njection methods.
The radionuclide source terms are essentially the same as those given in WASH-1400, Appendix 77 (I,), except for the inventories of
=etastable Ie-133m and Ie-135m, which are based en asAc ecde calculaticas Q). They are also in good agreement with source terms calculated by Anno, et al. (1), and represent the equilibrium core inventory of radiciodines and noble gases in a typical 1,C00 MWe (3,200.'Nt) power reacter. These initial core inventeries were used to calculate radienuclide activities as a function of time accceding to decay relationships presented in figure 3.1.
Since cs-135 can be 6
regarded as stable (half-life 2 3 x 10 years), eleven decay 2
chains are of sufficient length to describe the temporal behavice of radienuclides listed in table 3 1.
2Eleven cha1=s were used to acecunt fer nultiple decay
= odes. The fraction of a nuclids in a decay chain is determined by the branching fractica for decay within that chain.
.,/
D-24 e
i
- able 3.1.
Radionuclide source cat.
b Nuclide Half-life
- Initial Inventory Average Beta Energy" Average Gamma Energy" (br)
(108 C1),
per Disintegration per Disintegration IS (MeV)
EY (MeV) l Kr-85 9.4 x 10' O.0056 0.251 0.0022 l
Kr-85m 4.48 0.24 0.225 0.18 o
Kr-87 1.27 0.47 1.33 0.79 Kr-88 2.8 0.68 0.249 2.2 Ka-133 127 1.7 0.102 0.030" Ze-133m
$3.5 0.04 0.0 0.020" i
Ie-135 9.17 0.34 0.310 0.26 Ka-135m 0.27 0.19 0.0 0.53 t
I-131 193 0.85 0.185 0.39 v
I-132 2.29 1.2 0.5 25 2.2 I-133 20.8 1.7 0.417 0.60 I-134 0.877 1.9 0.691 2.6 ed I-135 6.59 1.5 0.394 1.5 "From table VII, reference (R).
b3ased on references (7_) ~and (8_).
" corrected for internal conversion (table VI, reference (g)).
D-25 e
3 55m (0. 21)
_ g; 5 I0
- 19) 3 g
5 (stable)
Er
- Eb (stable) 8 88 9"
_ 3,88 (stable)
~
g;88
_g 1
--h131 (st e le) 131 3
I
- Ia (scable)
~
133 (0.14) 8
- y,132m 7
(0* 86) g ~
1:
1 Ia
- Cs (stable)
I-
- Za (stable)
~
135 (0.15) g,135m 7
I a ),.
s 1:
7,135 d
135 9
_3,135 (stable)
~
g Eased a data in referanca (10).
IT = isomeric transition.
3 ranching ratios in parentheses.
Figure 3.1.
Radiciodine and noble gas decay chains.
s D-26 e
3.2 ':tvreid Dese Cenversten Faeters for Radiciedine Inhalation To use'the thyroid inhalation dose projection nothods discussed in section 2.2.2 cf this Appendix, it is necessary to determine th<
appropriate dose conversion factors for the individual radioiodine isotopes which =ight be present in air at the point of exposure.
The thyroid inhalation dose cenversion facter, DCF*h, has been defined to be equal to the 1 thalation dose to the thyroid resulting from the exposure to a unit integrated activity in air of the kth radiciodine isotope. It may be written as
- E(-AZK*)d'*
BR f E
ak k DCT'*h = 5.92 x to2 0
k a
m Y
2 BR '* k k (3 1) a
= 5.92 x 10 m ^Ek i
where:
DCF'*h a thyroid inhalation dose ccaversion factor for the 3
kth icdine isstope (rad-m /Ci-s) 3 BR = breathing rate (m f,)
f a fraction of inhaled activity of the kth ak raciciodine isotope which deposits in the thyroid
\\
m a mass of the thyroid (g)
D-27 l
s I., = effective energy absorbed in the thyroid per disintegration of the kth radiciodine atos (MeV/ dis)
~0 10 5.92 x 10 = 1.6 x 10 rad-g/MeV x 3.7 x 10 dis /s-ci (rad-g-dis /Mev-s-Ci)
A
= effective decay constant of the kth radiciodine Ek in the thyroid (s-1)
,0.693 0.693 hNk
'h3k where:
b Nk = nuclear half-life of the kth radiciodine (s) s
- sBk = biological half-life in the thyroid of the keh radiciodine (s).
3.2.1 Dependence of Theroid Mass and 3reathing Rate en Age Since the thyroid mass, as well as metabolic activity, depends en a person's age, the dose conversion factor can be expected to be a function of age, and, to properly evaluate it, the age dependence of the parameters 3R, f,, I, m, and 1 must be determined.
3 1
j Table 3.2 presents values of total body mass, thyroid mass, and 1
l breathing rate as a function of age. All values are based on data in reference (11,).
The values of breathing rate are characteristic of cha ' light activity" phase, which is greater than the daily
~
l average breaching rate, especially in the case of a newborn. The i
breaching rates of the 5 year old and 15 year old vues determined uy graphical interpolation en the basis of body mass.
l l
D-28
Table 3.2.
Sody mass, thyroid mass, and breathing race as a function of age Age Body Mass Thyroid Mass Breathing Race Years kg g
,3,
j Newbo rn 3.5 1
2.5 E-05 1
10 1.8 6.9 E-05 5
19 3.6 1.3 E-04(*)
10 33 7.4 2.2 E-04 15 60 12.1 3.2 E-04 *)
I n
Adult 70 16 3.3 E-04
(* Interpolated on the basis of body mass.
1 D-29 i
l 1
l
.s 3.2.2 Uocake of Inhaled Radiciodine into the Byroid Byroidal iodine uptake is dependent to a large extent on the total lodine in the diet. De Federation of American Societies for Experimental Biology prepared a report on " Iodine in Foods" for the Food and Drug Administration (g). In t.his report, (odine was noted as coming from diet with a range of 382 to 454 ug 1/ day; and frem the atmosphere, 5 to 100 ug I/ day. The total estimated intake is more than twice the recommended daily allowance of 35 to 150 us I/ day.
De reflection of variation in duit.ary intake of iodine in the fractional uptake of iodine is well known (g,M,g). The effects of the changing dietary iodine values have been reflected in the 24-hour thyroid uptake values recently reported for iodine-131 (12,16-22). The new values reported include 21.5% : 6% (3),
12.1% : 6.1% (19), 19% : 8% (20), 15.6% : 4.5% (21), 15.4% : 6.8%
(22), 20.0% : 6.5%(3),and17.4%: (%)7.2%(3). The average of these val'es is 17.3% uptake.
u Karhausen, et al. (2]) reviewed the reports in the literature l
and compared the 24-hour I-131 uptake values reported in children from birth to 20 years of age with their own data. The results l
l support the thesis that from birth to about 1 year of age there is a I
reduction in the thyroid uptake value. At birth, thyroid uptake is i
D-30 j
e
,, - ~
t from 1.5 to 2 times higher than the adult value, but by 1 year of age it has dropped down to about the adult value (in Karhausen, et al. ( g), from 40 to 70% uptake at birth down to s 30 uptake at 1 year of age and older). The particularly high values (60-70%) have beenobservedinthefirstfewdaysafterbirth(g).
I1'in, et al.
s (M),foundintheirreviewoftheliteraturethatafter2yearsof age the thyroid uptake value was relatively constant. Wellman, et al. ( M), reported similar findings.
On the basis of this literature survey, the fraction of ingested radiciodine activity which deposits in the thyroid, f,,
is assumed to be 30 percent for individuals less than 1 year old and 17 percent for it.dividuals above the age of 1 year. Since this e.
value is based ca data for I-131, it should be conservative for the shorter lived iodine isotopes. If the fraction of inhaled radiciodine which reaches the thyroid, f,, is assumed'to be 75 percentoff,(2]),thenf,isequalto23percentfer individuals under 'l year of age and 13 percent for individuals 1
.wp.ast
- h. 4 m * -
year old and older.
3.2.3 Effective Decav Energies of I-131, I-132. I-133. I-134, and I-d5 in Human Thvrota Nuclei of iodine isotopes I-131 through I-135 all decay by the emission cf beta (S) particles. In general, when a nucleus emits a beta particle, it is left in an excited state and sheds its excess energy by either emitting a gamma (Y) ray ur by internally convertinganorbitalelectron(3).
D-31
- _ _. - _ _ _ _. _, _ _ _ _ - _ _. ~, _. _ _, _. _. ~, _ _,,,. -. - - _ _ _
' Conservatively assuming that the total beta and electron energy is locally abscrbed in the thyroid, the effective' decay energy of each radionuclide is the sum of the average beta energy, the energy of the converted and Auger electrens, and the faaetica of emitted x-ray and gn=ma-ray energy which is absorbed locally 4 the thyroid.
Thus, the effective decay energy 5=I+E + :: %E (3.2) 3 e
Y g
g where:
I the average beta energy 3
2, a the energy of the ccaverted and Auger electrons E
a the energy of the ith x ce gamma-ray, and
$1 = the fraction 3 which is locally absorbed in the 7
thyroid.
For radionuclides which have complicated decay schemes, rigoreus calculatica of I can beceme quite tedious. Hence, an approximate method of calculating the effective decay energies of I-131 thecugh I-135 was develcped which, at a substantial savings in effort, yields values of I which are believed to be sufficiently accurate for accident dose calculations.
l D-32
./
i s
Table 3.1, in section 3.1, presents the radioactive half-lives and average beta and gamma energies emitted per disintegration by nuclei of I-131 through I-135. The value of E in table 3.1 is the 7
total transition energy sad includes any internal conversion energy as well as the average gansna energy emitted per o
disintegration.
In radionuclides under consideration, the process of internal conversion is relatively uninportant. England, et al. QO) (tables VI and VII), indicate that in I-131 and I-135 the internal conversion energy (energy of ejected electrons and associated x-rays) accounts for only 0.0104 and 0.0236 of the total transition energy of the two radionuclides, respectively. Conservatively assuming that all of the internal conversion energy is imparted to
'^
ejected electrons, the energy of these electrons would account for
'~
only about 2 percent of the average I-131 beta energy and approximately 9 percent of the average I-135 beta energy. Dillman, et al. (28), indicate that the sum of the energies of the converted and Auger electrona accounts for as much as 5 percent of the average l
I-131 beta energy and for about 1 percent of the average I-133 beta f
energy. Considering the relative contributions of the five iodine isotopes in a reactor grade isotopic mixture to the thyroid l.
3 Energy liberated in transition from an excited state to the ground state.
l l
D-33 i
l l
4
inhalation dose (figure 7I 13-4, reference (1)) and the degree of accuracy required for projecting doses in accident situations, internal conversica can cisarly be neglected in calculating the effective decay energies of I-131 througn I-135 in the human thyroid.
As indicated in Eq. (3.2), the absorbed frsction, 4, is a fccction of gama photon energy.. However, as a first approximatica, $ nay be taken to be a constant, equal to its value at the average photon energy, 5. Ihen, the effective decay 7
energ7 is E=E
+
- E (3 3) 3 7
where $ s $(E7 ), and E7:IE7 1
i i
Values of E f r I-131 tru ough I-135 are presented below and, Y
g except for I-134, were all taken fecm table I, reference (8). Ihe value of E for I-134 was estimated from decay data in table 1, 7i reference (2_g,).
Iodine Isotope I-131 I-132 I-133 I-134 I-135 5
(Mev/photen) 0.4 0.79 0.56 09 1.5
~
7i D-34 l
l r
~'r-r r
- -., _. - ~
Values of e as a function of individual age and iodine isotope, which were determined by this method, are presented in table 3.3.
Table 3.4 presents the calculated effective disintegration energies of the five iodine isotopes in the thyroid as a function of age.
The accuracy of this method of calculating effective decay energies was tested by comparing the values of II for I-131 and I-133, for a five year old, to values of I calculated rigorously according to Eq. (3.2).
The conversion process was fully considered, decay data in reference (28,) was used, and values of $
as a function of thyroid mass and photon energy were obtained by graphical interpolation of data in table 22.1, reference (30).
To within two significant figures, the values of I were found to be 0.20 Hev and 0.42 for I-131 and I-133, respectively. The 5
differences are mainly due to slight discrepancies in decay energies in ref erences (10,) and (28), and to round off errors.
8 3.2.4 Effective Decav Constants of Iodine Isotones I-131 throueh I-135 in ene Human Thyroid as a Function or Sunject Age Table 3.5 shows the age dependence of the effective decay constants (X 's) of the five iodine isotopes under consideration g
in the human thyroid. These values were calculated using the nuclear Jmes) half-lives in table 3.1 and estimates of biological half-lives in ?Aference (3 ).
O D-35 b
m 4
4 Table 3.3.
Absorbed fractions ($) in the thyroid as a function of age and iodine isotope Thyroid Age Mass Absorbed Fraction (6)(a) for Years s
I-131 I-132 I-133 I-134 I-135 I
Newborn 1
0.0048 0.0048 0.0050 0.0047 0.0043 1
1.8
.0060
.0060
.0062
.0059
.0054
? 4+ ~
-. m 2 =1 ~.an; 5
3.6
.018
.017
.018
.017
.013 10 7.4
.025
.023
.025
.023
.021 15 12.1
.028
.027
.028
.026
.023 Adult 16
.031
.029
.031
.029
.026 l
t (a)This information was derived from information in table 22.1, reference (3,0).
The absorbed fraction for a 1 gram thyroid was obtained q
by siltiplying the value of $ for a 2 gram thyroid by the ratio of cube roots of the masses. Values of $ for rpecific photon energies and thyroid masses were obtair.M by either choosing the closest values presented in the referetxe o+: by interpolation.
4
Table 3.4.
Effective decay energies for I-131 through I-135 present in the thyroid as a function of age Effective Decay Energy E (MeV) for Age Years I-131 I-132 I-133 I-134 I-135 Newborn 0.19 0.54 0.42 0.70 0.40 1
.19
.54
.42
.70 40 5
.19
.56 43
.74 42 10
.19
.58
.43
.75 42 r,
15
.20
.59
.43
.76 43 Adult
.20
.59
.44
.77
.43
.%-~
=
l e
D-31 l
l G
w Table 3.5 Effective decay constants of I-131 through I-135 in the human thyroid as a function,of ale Effective Decay Constant (sb Age Years I-13 1 I-132 I-133 I-134 I-135 Newborn 1.4E-06 8.5E-05
- 9. 7E-06
- 2. 3-04 3.0E-05 l
1 1.3E-06 8.5Z-05 9.5E-06 2.2 -04 3.0E-05 5
1.3E-06 8.5Z-05 9.5E-06 2.2E-04 3.CE-05 1
10 1.1E-06 8.4E-05 9.4E-06 2.2I-04 2.9E-05 15 1.12-06 8.4E-05 9.4E-06 2.2E-04 2.9E-05 Adult 1.1I-06 8.4E-05 9.3E-06 2.2Z-04 2.9E-05 e
e 3-38
3.2.5 Denendence of Thyroid Dese conversion 7 actor en Aee The age dependent thyroid dose conversion factors for iodine isotopes I-131 through I-135 have been calculated according to Eq. (3.1) and are presented in table 3.6.
The age group which would receive the greatest thyroid inhalation dose from an exposure to a given radiciodine activity concentration in air appears to be comprised of newborn babies whose dose conversion factor is from 1.6 to 2 times greater than the dose conversion factor for adults.
Table 3.6 also indicates that the variation of the dose conversion factor with age is rather small, especially below to the age of 10 years.
As in the case of whole body gamma dose calculations, it is assumed that the thyroid dose equivalent in reas is equal to the absorbed dose in rads.
4.0 Results Table 4.1 presents the ceabined core and containment inventory, A.,(t), of noble gases and halogens as a function of time after shutdown. The containment leakage rata is assund to be zero, and thus, the decrease of the radiciodine and noble gas inventories with time is due only to radioactive decay.
Based on data in table 4.1, table 4.2 presents the ratio of iodine to noble gas inventory in the containment as a function of time af ter shutdown and the iodine release fraction. Assuming a D-39
s S
~
Table 3.6.
Thyroid dose conversion factor as a function of age a.2d iodina isotope l
Inhalation Dose For Unit Activity Exposure, rads Age C1-sec/m3 Years I-131 I-132 t-133 I-134 I-135 Newborn 450 22 15 0 11 45 1
430 19 130 9.7 39 5
400 18 130 9.4 39
^~P 10 400 16 110 7.7 33 15 380 14 93 7.0 30 Adult 290 11 '
76 5.6 23 ~~
6 Maximus Age Group 450 22 15 0 11 45 Newborn c
Ratio of Mm=d- =
1.6 2.0 2.0 2.0 2.0 Age Group to Adult p'
s=
=
.)
D-40 g
s" 9
--,,--r
,,_m...
~
,,..-w-.
,,,.,,,v-.
,,,----,,- ~, ----.,
-.w--,-
--,,,k
a.
Table 4.1.
Moble gas and iodine inventory in the reactor core a
and containment as i function of tima Time After Total Iodine Total Noble Gas Shut' dan,
Inventory Inventory (108 C1)
(108 C1)
_(hr)
~ '
0.0 7.2 3..
1.0 5.6 3.4 2.0 4.7 3.2 3.0 4.1 3.0 C..
'b 4.0
~
3.8 2.9 6.0 3.2 2.8 12.0 2.4 2.5 3ased on the shutdown equilibrium core inventory of a typical
- 8 1;000 MWe (3,200.We) power reactor and zero containment leakage rate.
s t
I i
>c
'd W
D-41 ~
I e
4 J
ha
-~
~
F',$4" 5 --,se
+-
---i----67
-.QI, %,,, _
..y
=
R ci 6
~
, )
s
- k f
4
/
j w
- s.,
e.
, i
,1 Table 4.2.
Iodine to nome Sam activity ratio as m' function of j
fodina release fraction and time after shutdown 1,
ij l
Time after Shutdown (br)
Iodina Release Fre e.t ion 0.0 1.0 2.0 3.0 4.0 6.0 12.0
?,
1.0 2.0 1.6 1.5 1.4 1.3 1.1
.96
)'
O.5
. 0.98 '
8.2
. 73
.68
.66
.57-
.48 0.25 A9
.41
.37
.34
.33
.29
.24 0.1
.20
.16
.15
.14
.13
.11
.096 0.05
.098
.082
.073
.068
.066
.057 048 n
L N
0.025
.040
.041
.037
.034
.033
.029
.024 0.01
.020
.016
.015
.014
.013
.011 0096 0.005
.0098
.0082
.0073
.0068
.0066 0057
.0048 0.0025
.0049
.0041
.0037
.0034 0033
.0029
.0024 0.001
.0020
.0016
.0015
.0014
.0013
.0011
.00096 0.0005
.00098
.00082
.00073
.00068
.00066
.00057
.00048 0.00025
.00049
.00041
.00037
.00034 00033
.00029
.00024 0.0001
.00020
.00016
.00015
.0001
.00013
.00011
.000096
radionuclide independent containment leakage rate and X/U, this would also be the ratio of iodine to noble gas release rates and concentrations in air.
The release fraction of noble gases is taken to be equal to one. Because of their similar chemical
~
properties, all iodine isotopes are assumed to have equal release fractions.
The values in table 4.2 indicate that the ratio of total iodines to noble gases varies from approximately 2 at shutdown to 1 at 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. At an iodine release fraction equal to 0.25, corresponding to a design basis accident (4,5), this ratio varies from approximately 0.5 to 0.25 over the 12-hcur pericd after shutdown.
4.1 Whole Body Dese Table 4.3 presents the ratio of the semi-infinite cloud gamma dose rate to the noble gas cencentration (RGC,*) as a function of time after shutdown calculated in accardance with the methods presented in section 2.2.1 of this Appendix. Since they are highly volatile, noble gases resulting from decay of the core equilibrium "Although a particular iodine fraction may be released to containment, deposition of the iodines on surfaces and the operation of any engineered safeguards to reduce the airborne concentrations in containmect would reduce the fraction of radicJodines released to the environment. Tnese factors will influence the corrsction factors regarding the iodine to noble gas activity ratio as discussed later.
D-43
r N
Tabla 4.3.
Ratio of noble gas gamma dose rate to noble gas concentration, RGQ,asafunctionoftimeaftershutdown RG7n Time after Shutdown res/hr (br) c1/m3 0
5.3E+02 l
1.5 5.0E+02 2.5 4.3E+02 4
3.5 3.7E+02 4.5 3.1E+02 6.5 2.3E+02 12.5 1.2E+02 t
4 e
D-44
-s 4
inventory of radiciodines are assumed to contribute to the noble gas source te:-s, -and the ga ma dose rate also includes a cceponent feca Rb-88, which is a daughter product of Kr-88. Also, the time units in RGC, have been converted from seconds to hours.
Figure 4.1 (figure 5.1 of Chapter 5) presents a graph of the projected whole body gamma dose as a function of gamma dose rate in air and the projected duration of exposure. The projected whole body dose is simply the result of multiplying the gamma dose rate in air by the projected exposure duration. The projected exposure duration is in hours, and the gamma dose rate is in ares /hr (10-3 res/hr). The ordinate on the right, noble gas concentration in air, was added by assuming a gamma dose rate to noble gas 2 res/hr IDi* E*#*i*"l*# **1"* "**
concentration ratio of 3.1 x 10 3*
C1/s calculated to correspond to radionuclide mixtures that would exist
^
f at 4.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after reactor shutdown, as indicated in table 4.3 For shutdown times greater than 4.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, this choice of RGC" for noble gases will tend to overestimate the gannas dose rate relative to noble gas concentration. In instances of long decay periods where only the long lived noble gases remain, equation 2.7 and the gamma decay energies listed in table 3.1 may be used to calculate dose rate more accurately than those in figure 4.1.
l 4.2 Thyroid Dese
- be ratio of the thyroid inha?ation dose to the total radiciodine concentration in air, (RIC), calculated by methods presented in section 2.2.2 of this Appendix, is given in table 4.4 as a function of tile after shutdown at which exposure begins, t,,
t l
D-45 l
l
- /
4
i l
l l
i N
i 4
\\h' lltl l I TO USE T! TIS C1tAFM
.,,,,,. g, g lL Plot the point representing samina
=
\\
\\j llII radiation esposure rate (aA/hr) and
-7 f
2 g
projected duration of exposure (hrs).
N
\\
Zatiaste the projected whole body dose N\\
~
~
\\ \\
from the curves above and below the g+,
point.
~
m s
s s
x i v_.
7, xix x
m,x_
-2 x x
,y
... w_ w.
'ie i
N
. N i NJ iN i i e % \\ i. e isiis i
4,
\\l
\\ IN lR R Ro.! I i l lli l
I IIl 1
10-t N
1s NRt NT<d i Ill I!l!
II E
7 2-N y 4s 4
N N
N 4
tg -
g x
xg 7-
_2 3
x.
x,
.m s.s s
s x
.~...x x.
m s
,m
~
e x
.x i N i i l l W l\\ iN N 6 t i s \\8 8 8 Ut 2 N
,'i,
\\l \\ i 141 l '
\\ 11 i N NI
\\K lI 16:
'k N I N
. \\lVR \\\\llill E
I
\\ NS
-7
- ~
N N
N
- i N
a x
N N
d s
s s
x s
s 3
a to3-x s
s 1._
x x
x x
,~
ss
.~ -
s
~
m m
s 7-s s.
m s
s.
x
.s s
-2 m
s,
,m s
.x,
...s
~ s
~,..x I
x x
,,, v vi x
.., x
.x
,x
~ni I N{ l Mili
\\*') '\\l M ll
\\l1
\\j IN '
gg.3 [
l
\\\\ IMt _ N l'k IM N l 'sJW E 1-7 2-s s
s s
s l s N
s N
N N
N
- _d
.s x
s N
to2 s.
s s
xm s
,s s
s.
7-
'T '
fs'.'.'1
- -2 1
x, _
1 y
x.
t
.h
.st'e 6.il N
{ 6 s 4 se e
I 6 4 1't A i ?\\. 6iet \\
x! h 9 '
l' I N i h{ l il
\\ l Al i N l 4 I
II I
^
1M l lN l1 E I
l' l
s
_7 2-s i
s s
b
\\.
\\
- 4x10-3 N
(
\\
1 g
01
.2 4
.'7 1
2 4'
7 10 2.'O 4d 7'0 100 projected exposure duration (hours)
Figure 4.1 Projected wnole body gama dose as a function of gasuna exposure rata and projected duration of exposure 3-46 j
e I
_. ~,... _ _.....,....,.. _ _. -,... - _.. _. -... _,. -....
1
[ 'N) l 1
Table 4.4.
Ratio of a child thyroid inhalation dose to radiofodine concentration, l
RIC, as a function of time after reactor shutdown at which l
exposure begins and the inhalation exposure duration RIC, [ '*/m3/*kforinhalationperiodsrangingfrom1to12 hours Time after
\\C1 shutdown at which exposure starts (hr) 1.0/hr 2.0/hr 3.0/hr 4.0/hr 6.0/hr 12.0/hr l
1.0 5.0Et05 9.8E405 1.4E106 1.9E606 2.8Et06 5.2Et06 i
2.0 5.6Et05 1.1Et06 1.6E106 2.lEt06 3.2E406 5.9E106 9,
C 3.0 6.1E105 1.2E106 1.8E106 2.3Et06 3.4E606 6.5E+06 i
1 4.0 6.5E605 1.3Et06 1.9E106 2.5E106 3.7Et06 7.0E106 6.0 7.lE105 1.4E606 2.lEt06 2.8E+06 4.1E106 7.7E106 12.0 8.4E105 1.7Et06 2.5E406 3.3Ef06 4.9EfD6 9.3Et06 a
4 1
?
m and the inhalacion exposure duratien, t,.
The time c, is the sum of the time af ter shutdown at which release occurs and the plume travel time. The projected exposure duration would be determined by the functional status of the engineered safety systems or the wind
~
direction persistence at the time of the accident. It is assumed that monitoring personnel would be able to reach the projected exposure point such that environmental measurements could be taken within approximately 0.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> af ter plume arrival. A change in the time of measurement, c,, of 0.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> was found to change RIC by at most 10 percent at t, equal to I hour and by 2 percent at t, equal to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
Table 4.5 presents the values of radioiodine cescentration in air which would deliver a 5 rem thyroid inhalation dose to a newborn baby (critical age group) as a function of inhalacien time and six different times after shutdown when the exposure is assumed to be started. These values were obtained by dividing 5 rem by the ratio of projected thyroid dose to radiciodine concentration, RIC, and are plotted in figure 4.2.
As would be expected, the concentration of radiciodines l
required to deliver a 5 rea thyroid dose decreases with increase in time after shutdown since the short-lived isotopes decay, and only the long-lived isotopes I-131 and I-133 (with large dose conversion
~
l factors) remain in the radiciodine mixture.
I 3-48
_s l
l 1
l l
. ~ -..,........,
Table 4.5.
Radiolodine concentration in air which would result in a 5 rem thyroid inhalation dose to a child as a function of time after reactor shutdown, t, at which exposure begins and the inhalation time (C1/m3) r Inhalation Time Time after Shutdown, t.
1.0/hr 2.0/hr 3.0/hr 4.0/hr 6.0/hr 12.0/hr I
i (hr)
Radiolodine concentration yielding 5 rem thyroid dose to child (C1/.3) i
,5 l
1.0 1.0E-05 5.1E-06 3.5E-06 2.6E-06 1.8E-06 9.5E-07 2.0 8.9E-06 4.5E-06 3.1E-06 2.3E-06 1.6E-06 8.4E-07 4
I 1
3.0 8.2E-06 4.2E-06 2.8E-06 2.1E-06 1.5E-06 7.7E-07 e
i 4.0 7.7E-06 3.9E-06 2.6E-06 2.0E-06 1.4E-06 7.2E-07 i
i 6.0 7.1E-06 3.6E-06 2.4E-06 1.8E-06 1.2E-06 6.5E-07 1
12.0 5.9E-06 3.0E-06 2.0E-06 1.5E-06 1.0E-06 5.4E-07 i
i 5
.I e
1 1
1 10-5 9 7.
3 t. _
7 uc -
2
' ;,y.
_ m._, _ _
m
_- s--w - - w e
w_ _ -
+
u 4
1.'..
.M.
s t
s'.
3
.=.
._A_'_, '.._c-
.__v__
.o e
"o 2
u M
c u
,. ; _~ :.
9
'1 ' 2n 's 5
's N.'s'-A 's u
yw;x s
's x' A 's i
s.
s.
,ss
.x
-6 s
g 10 3
9 8
~-s g
m 7
=
.,'m 6
_'3 - -__
2 5
w%_.n,-__-_,_
l
-w.
t
. - _ _ ^m' u'u' u ' m 4 x 10,7 1
2 3
4 5
7 10 13 20 30 l
I 1
l Projected exposura duration (br) l l
Figure 4.2.
Five rem isodose line for child thyroid as a function of l
radiciodice concentration at the start of exposure.
l exposure duration and time after sintdown at which exposure begins, t,.
l t
I D-50 I
l l
Given.a knowledge of the time after reactor shutdown at which exposure begins and the projected inhalacion period, figure 4.2 may be used to determine the radiciodine concentration which would deliver a 5 rem dose to the thyroid by simply locating the ordinate of the appropriate e, line at the projected inhalation time e,.
For any different thyroid dose the iodine concentration can be scaled linearly. For example, if the plume arrival time at a given location were about 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and the projected exposure time were also 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, the radiciodine concentration which would deliver a 5 rem thyroid inhalation dose to a child would be equal to
-0 approximately 2 x 10 Ci/m of air.
Figure 4.2 can also be used to project thyroid doses based on n.
radiciodine concentrations estimated from containment release race and meteorological conditions at the time of the accident. However, s_.
figure 4.2 should not be used to project inhalation doses from I
single iodine isotopes because in its derivation a five component l
o p uquof radioiodines has been assumed. For that purpose, the b *.-
dose conversion f actors listed in cable 3.6 may be used (multiplied by 3.6 x 10 to convert units of time from secends to hours).
3 Similarly, figure 4.2 would not be suitable for projecting thyroid dose if the release occurred from a reactor that had been shut down f er a period such that the shorter-lived isotopes of iodine had I
In such a case, the dose conversion factor for iodine-131 decayed.
from table 3.6 would be more appropriate.
t l
D-31 l
l l
e
's The ratio of iodine concentration to the semi-infinite cloud gamma dose rate from iodines and noble gases, RIG", which was discussed in section 2.2.2, is presented in table 4.6 as a function of time af ter reactor shutdown and iodine release fraction. The increase of RIG" with time is due to the decay of the short-lived but energetic (in gamma energy) Kr-88, I-132, and I-134 The values in table 4.6 indicate that the ratio of iodine concentration to semi-infinite cloud gamma dose race from both noble gases and iodines varies from approximately 6 x 10 at shutdown
~3 to 1.3 x 10 at 12.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. For an iodine release fractien equal to 0.25, this ratio varies from approximately 4 x 10' to 9 x 10 ' over a 12.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> period af ter shutdown.
Figure 4.3 presents a graph of projected thyroid dose as a function of the projected time period of exposure and either the radioiodine concentration or the gammaa dose rate in air. The relationship between thyroid dose and radiciodine concentration was established by selecting the 5 rem line from figure 4.2 which corresponds to a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> period aft eactor shutdown at which exposure is assumed to begin. This line was chosen because over an inhalation period of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, all the other lines are within a : 33 percent range of the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> line. For different thyroid doses, the iodine concentration has been scaled linearly. For concentration s
D-52 2
/
~,
l
(
)
i Table 4.6.
Ratio of lodine concentration to total iodine and noble gas amma slose rate as a function of fodine release fraction and time after shutdown cifm3 rea/hr i
Time after Shutdown Iodine Release 0.0 (hr) 1.5 (hr) 2.5 (hr) 3.5 (hr) 4.5 (hr) 6.5 (hr) 12.5 (hr)
Fraction Iodine concentration to y Jose rete ratio C1/m3) rea/hr /
1.0 6.0E-04 6.9E-04 7.6E-04 8.4E-04 9.lE-04 1.0E-03 1.3E-03 l
0.5 5.lE-04 5.6E-04
- 6. 2 E-04 6.8E-04 7.4E-04 8.5E-04 1.lE-03 0.25 4.0E-04 4.lE-04 4.5E-04 4.9E-04 5.4E-04 6.4E-04 8.8E-04 0.1 2.4E-04 2.3E-04 2.5E-04 2.7E-04 3.OE-04 3.6E-04 5.2E-04 0.05 1.5E-04 1.3E-04 1.4E-04 1.6E-04 1.7E-04 2.lE-04 3.lE-04 2
0.025 8.2E-05 7.lE-05 7.6E-05 8.4E-05 9.3E-05 1.lE-04 1.7E-04 i
0.01 3.5E-05 3.0E-05 3.2E-05 3.5E-05 3.9E-05 4.8E-05 7.5E-05 0.005 1.8E-05 1.5E-05 1.6E-05 1.8E- 05 2.0E-05 2.4E-05 3.aE-05 0.0025 9.1E-06 7.6E-06 8.2E-06 9.0E-06 1.0E-05 1.2E-05' l.9E-05' O.901 3.7E-06 3.lE-06 3.3E-06 3.6E-06 4.0E-06 4.9E-06 7.8E-06 0.0005 1.8E-06 1.5E-06 1.6E-06 1.8E-06 2.0E-06 2.5E-06 3.9E-06 i
0.00025 9.2E-07 7.7E-07 8.2E-07 9.lE-07 1.0E-06' 1.2E-06 2.0E-06 0.0001 3.7E-07 3.lE-07 3.3E-07 3.6E-07 4.0E-07 5.0E-07 7.8E-07 h
+
i
?
t o' -
-.7 x
'.x 7-4 x
x
.ie i
.s+x i-
.. k k h
l' adult l l l l l
I l
-2 N
N
's carrott
(
x
\\
\\
dose I
\\
\\
N
- 3
-- to
\\
s 3
7 gg, (_
\\
s s
's 1
% w1 7-
-5 s
x s:, s.
s x
s x
..w w x i,.
x x
s i
y N As i i
6
\\
\\
l 4 !\\ ' K}
'l childi
--2
(
\\\\
\\
lit. h \\N ll 4U' E s
4 x s
J N s'\\ x yw_ s s
s N ft\\
\\
N N,
- g-te g z
-7
~
1
~
's '=
7-
~
-6 e
x m
.sm s
s; m
s 4
x x,
x-v
.x6
, 1,6
.u x, s 1
.x y
- s..-s.
w x,iu i
vx 1,_
N A,N N NN IX liN 44 N
\\ \\ \\ fhLN \\ lM 1 \\
2_
N N x x g\\
\\
x N.X
=-to-5 i
!w.
\\A 4
\\
%\\
- -7 5
1 s
xi
't n-7-
s
-6 s
,.i v s
s s
v x
I x
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. x,.x, x.
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2-. rate or toecentration and exposure time and estisete the projected thyroid dose b
" 10 7 by interpolation.,ee, g-1, e
i e e,
1 6 x 10 i
i e i e
i 0.1
.2
.r.
.7 13 2 34 7 to 20'30 Projected Exposure m e (Hours) msUas 4.3 PeeJECus nues nest As A FUNCTWu 0F ErnER SANWA IIPOSURE 4ATI. OR RAOWIBIMIE CONCDinAT1011 m As Amo ut PROJECTED EIPOSURE T30E.
- Twis cmamo sMouts as usao we comJuncTrom wem ricuats a a ano a s.
>54 Revised 6/80 h
o
-, - ~, -. - - - -,
.,,n.-.,--
- - ~ - - - - - - -
measurements made less than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> af ter reactor shutdown, figure 4.3 will slightly overestimate the thyroid dose; and for
~
measurements made more than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after reactor shutdown, the dcse will be underestimated. Figure 4.4 provides an indication of the i
error involved. The ordinate of this figure provides a correction factor.
Because of shif ts in wind direction, it is unlikely that thyroid inhalation doses would be projected for time periode beyond the range considered in table 4.3.
However, for those instances when that range might be exceeded, the lines have been extended from 0.1 to 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> in figure 4.3.
The adult thyroid inhalation doses which have been indicated in
(
'igure 4.3 have been obtained by dividing the newborn infant doses by a factor of two, in accordance with discussion in section 3.2.5 i
of this Appendix. The use of the same factor for I-131 as for tha other iodine isotopes (see table 3.6) introduces an error in the j
adult dose of at most 25 percent, which is well within the uncertainty range of the overall dose projection method.
l As discussed previously, the iodine release fraction would i
depend on the functional status of the engineered safety systems, and significant fractions of the core inventory of radiciodines would be expected to be released to the environment only in the most severe types of accidents. However, if, for the purpose of f
I l
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10 11 12 TIME (HR) AFTER SHUTCCWN FIGURE 4.4 CORRECTION FACTORS FOR THYR 0!O IMHALATION 0035 A3 A FUNCTION OF TIME AFTER REACTOR SHUTDOWN THAT RADICIODINE CONCENTRAT10N IS lAEASURED.
/
D-56 e.
analysis, a 0.25 iodine release fraction is assumed, then table 4.6 indicates that over a time period of 12.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after reactor
' shutdown the ratio of iodine concentration to cloud gansas dose race
-4 Ci/m is equal to 6 x 1C 50 percent This ratio has been re e r used to establish the functional dependence of thyroid inhalacion dose on the ganma srposure rate in air, in ares /hr, as indicated in figure 4.3.
Since the relationship between ganma exposure rate in air r.nd thyroid inhalation dose in figure 4.3 is based on the semi-infinite cloud assumption, the use of gaw=== exposure rate from a finite cloud to estimate thyroid dose by means of figure 4.3 vill tend to underestimate the thyroid dosa. To compensate for this effect, the measured cloud gs=mns exposure rate should be multiplied by the finite plume correction factor plotted in figure 4.5 before being l
l applied in figure 4.3 to estimate projected thyroid dose. This factor, which has been plotted as a function of distance from reactor and acnospheric stability class, is eg) toge,yrio of g
l gasuna exposure rate from an infinite cloud to that from a finite cloud, as discussed in section 2.2.3 of this Appendix. The finite cloud correction factor may also be used to reduce the whole body l
gasssa dose from a given noble gas concentration which has been l
5These assumptions are in agreement with AEC' guidance (4,5) on assumptions that may be used in evaluating the radiological-l consequences of an accident at a light water cooled nuclear power facility.
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DISTANCE (MILES)
FHiURE 4.5 GAMMA EXPOSURE RATE FINITE CLOUD CORRECTION FACTOR Revised 6/80 D-58
estimated by means of figure 4.1.
To do this, the estimated whole body dose should be divided by the finite cloud correction factor.
Obviously, whole body dose projections based on measurements of ga:mna expcaure rate in air should act be modified.
In the development of figure 4.3, the iodine release fraction was assumed to be 0.25, and the noble gas release fraction was assumed to be 1.0.
This corresponds to an iodine to noble gas ratio of about 0.3 For accidents in which the iodine release fraction or the iodine to noble gas ratio is known to be different from that which has been assumed in preparation of figure 4.3, a second nultiplicative correction factor could be used to correct the thyroid inhalation doses projected on the basis of measurements of L,
gamma dose rate in air and figure 4.3 This correction factor has been plotted in figure 4.6 as a function of the ratio of iodine to 0
noble gas activities, and has been obtained by dividing the ratio of iodine concentratica to gamma dose rate at iodine release fraction equal to 0.25 by the ratio of iodine concentration to gamma dose rate at other iodine release fractions. The iodine release correction factor varies by at most 25 percent over the 12.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> time period after reactor shutdown, and its value at 4.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> has been selected for figure 4.6.
6 Table 4.2 indicates that over a 12.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> period r.fter reactor shutdown, the iodine to noble gas activity ratio = 1 3 x iodine release fraction, f
D-59 I
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O H ATIO. Ml8LTIPLY Tills CORHECTION 302 FAC10H BY Tile GAMMA EXPOSUHE :
J HATE TO BE USED IN ESil&lATING -
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TiiE PROJEC f Ep il4VHOID DOSE
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'l HAD60lODANE TO NOllt E GAS ACIIVilY HATIO FIGURE 4.5 RA01040DWE RELEASE C04SEC14GN FACTOR 9
e
5.0 Accuraev of Dose Projection Methods The calculational methods that have been presented are intend 4d for use in estimating projected population dose from exposure to the plume. These dose projections would be needed very quickly following collection of the data on which the calculations would be based. Therefore, numerous assumptions have been nade to reduce the need for collection of different types of data, and with each assumption, the poteurial exists for introduction of error. Several correction factor curves have been provided to reduce the error for cases where data mighc be available to determine these factors.
In addition to errors associated with calculational assumptions, there is a potential for major errors in the data used as a basis for the calculations, Both types of errors are
( __
considered.
5.1 calculatienal Errces Associated with Release Rate Assumotions It has been assumed that the release will be continuous and at a constant rate. No calculational error would result from this assumption if the release actually occurred in this manner.
However, there are an infinite number of release race characteristics that could occur. This introduces a potential error in the input data which will be discussed later.
D D-61 4
5.2 calculational Errers Associated with Assumetiens en Release Characteristics Methods have been provided for projecting dose to both the thyroid and to the whole body based on two different types of data.
One type of data would be gross airborne concentrations, and the other would be gamma exposure rate =easurements. Data on concentration could be from either environmental measurements or from calculaticas based en release rates, distance, metecrological conditions,andwindspeep
,, y y
5.2.1 Errors in Whole Body Dese If whole body dose projections are based en ga:mna exposure rate measurenents, the caly assumptien affecting calculational error would be that of setting expcaure rate equal to dose rate, which is censervative, by a facter of about 1 33 If the exposure rate is based en noble gas concentraticas, a possible calculational error factor of :.6 over a time period of 1 i
to 12.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after shutdown may be encountered because of changes in the ccmpositicn of the plume resulting feca depletica of the shorter-lived isotopes frca radicactive decay.
The whole body gn=ma exposure rate associated with an airborne concentratica of noble gases anc iodines as shewn in figure 4.3 was provided to permit the use of gn=ma exposure rate measurements to l
estimate projected thyroid dose frem inhalation of radiciodines. It I
was not intended for estimating ga=ma exposure rate fece g-ess l
3-62
(
t
concentration measurements or calculations. However, by appropriate use of correction f actors provided in figures 4.4, 4.5, and 4.6, one could estimate exposure rate from gross concentration data. The error associated with the calculations would be primarily associated vien the accuracy of the data used to obtain correction factors and 4
not with assumptions regarding mixtures of iodines and noble gases in the release.
An additional consideration for whole body dose would be the contribution from particulate materials. Based on information in reference (32), airborne particulate materials would contribute about 20 percent of ths external dose from the plume with the remaining being contributed by iodines and noble gases. This could cause the whole body dose projections based on concentrations of iodines and noble gases in air to be about 20 percent low.
5.2.2 Errors in Thyroid Dose i
Two methods of projecting thyroid inhalation dose are provided. One method uses gross iodine cone.entration as a basis,
and the other uses gamma exposure race data as a basis.
The relative abundance of the different isotopes of iodine l
changes as a function of time after shutdown which changes the dose conversion f actor. If the correction factor curves are used to correct this error, chare should not be significant error associated with changing characteristics due to decay of short-lived isotopes l
D-63 i
l
i
)
_s-l prior to start of exposure. However, a gap release as opposed to a core melt release could cause the iodine six to have a relative concentration of iodine-131 higher than assumed due to the decay of short-lived isotopes during the process of leaching from the fuel pellets to the gaps. This could cause thyroid dose projections from gap releases to be underestimated by a maximum of about 30 percent.
The use of gamma exposure rate measurements to project thyroid done requires ' assumptions regarding the characteristics of the release, and if the characteristics are different than assumed, the resulting dose estimates could include large errors. This would not be the preferred data base for estimating thyroid dose but could be used if iodine concentration data were not available. To reduce the error involved, correction factor charts for isotopic composition have been included as figures 4.4 and 4.6.
If data are available to permit decerninacien of these correction factors, the only significant errors should be.a possible 30 percent underestinate associated with a gap release as discussed above and a possible 20 percent overestimate from particulate sacerial contributien to gauna exposure race.
i 5.3 Errors Associated with Input Data e
f l
Data will be collected under pressure of emergency conditions, and the associated errors may severely affect the accuracy of dose projection. Errors caused by inaccurate data relating to (1) l l
s' D-64 i
4
environmental levels as a function of time, (2) the duration of exposure, or (3) the radiological characteristics of the release could seriously affect the dose projection results. Additional errors can be associated with information on vindspeed and direction, atmospheric stability, precipitation, and with o
interpretation of instrumentation readings.
5.3.1 Duration of Exnosure
+
To project dose based on concentrations or exposure races, it is always necessary to know the duration of exposure. It has been assumed for purposes of these calculations that this parameter will be known, when in fact the duration might range from a value of zero due to errors in vind direction data or to a value enual to the r
I duration of release if wind direction is persistant in the predicted direction. The resulting error in the projected dose could be either positive or negative and would be proportional to the error in the estimated duration except as aff ected by the changes in concentration as a function of time. It is not possible to put bounds on this source of error.
5.3.2 Errors in Release Race Data The release rate could have many different characteristics due to pressure transients caused by changes in the core conditions, operation of engineered safeguards, or changes in containment e
integrity. These conditions could introduce one or more orders e.'
l l
magnitude errors in the projected dose depending on whether the data l
l l
D-oS O
l
~
forming the basis for dose projection were obtained from a high or low point in the transient. This error could be reduced by frequent updating of data.
5.3.3 Errors in Data on Release Characteristics s
If gamma dose rates are used to estimate projected thyroid e
inhalation doses, correctica factor curves are provided which utilize the relative amounts of iodines and noble gases in the release. If the data are not available to permit use of these correction factors, errors could be introduced is projected thyroid doses ranging frem a factor of 2 too low to a factor of 100 or more too high.
5.3.4 Errors in Environmental Measutteents and Information Environmental information would include gasuna radiation exposure race, airborne concentrations of radioactive material, atmospheric stability class, vindspeed, and predicted meteorological conditions.
Measurements of exposure rates and concentrations would be representative of a particular locatien at a particular tLne, and
^
they may not represent either the average er maximum conditions at 9
that location. Levels at a particular location will change as a function of time depending on vind direction stability, localized dispersica conditions, and fluctuations in release race. No limits can be assigned to the errors associated with such measurements, but they could easily vary over 1 or more orders of magnitude.
D-66
,.x
f 5.4 Summarv A summary of the potential errors associated with dose projection methods presented here is provided in cable 5.1.
The potential error factors are values that could be divided into the 6
calculated dose to get the true dose. Due to the many unknowns associated with input data and information, it is not possible to assign limits to the potential errors. However, it is apparent that the potential errors associated with inaccurate input data overwhelm those associated with calculational assumptions, and therefore, further refinement of assumptions does not appear to be necessary.
p YV i
l l
l t
a l
D-67 I
l L
-\\.
,rl
~.
s
/
-/.
/
Table 5.1.
Estimated errors associat'ed.rith dise calculation netbads _
4
~~
Calculational Assumpticas Input' Data 1
Assumptica Potential Type of Data
~
Potential
[
Error Error
)
Factor Facter j
ishole body dose rate 1 33 Duration of expcaure urJcnown i
s equals exposure rate estimates Whole body dose rate 20.6E
- ?.elease rate 0.1 to 10
,s frem noble gas scre or less w concentration is not a function of the mixture F.elease characteristics
.5 to 100 over a 1 to 12 he period more or less Whole body dose rate 1 to 0.3 Environmental.
'0.51 to 100 s
frem mixture of noble coesurements and more er 1_ ass gases and iodines is not information influenced by particulates in the plume s
Thyroid dose will not 1 to 0.7 be influenced by a concentration enriched in I-131 i
aThe use of these projection methods for noble gases which had decayed for weeks to scnths (as might be the case for accidental releases frem vaste gas decay tanks) could cause overestimates of the whole bcdy dese by a factor of 10 or more.
~
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REyERENCES (1) INTERNAT!0NAL CONMISSiCN CN RADIATION UNITS AND MEASUR..'.fENTS.
f.ICRU Report 19. Radiation Quantities and Units. International
~
? Camaission on' 'tadianca Units and Measurements, Washington, J,; C. 20014,(July 1, 1971).,
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~
Office of Radiation' Programs, Washington, D.C.
20460.
~ Published in':he P rceedings of the Eighth Midyear Topical g
Symposium 'pf the Health Physics Society (October 1974).
(3)
U.S. ENVIRONMENTAL PROTEC'*rCN AGENCI. 40 CFR 190, s ' ~
EnvironmenE41 Radiation. Protection Requirements for Normal Operations of Activities,iu. the ' Cranium Fuel Cycle, Final Environnantal Statement. ; Environmental Protection Agency, A
Office of Radiation ?rograms, h shington, D.C.
20460
)
(November 1976).
l 6
t.,
~
'(.4 ) ' U.S. ATOMIC ENERGT COMMISSION. Regulatory Guide 1.3.
Assumptions Used for Evaluating the Potential Radiological
~
, Consequences of a Loss of Coolant Accident for Boiling Water Reactors. Directorate of Regulatory _ Standards, Nuclear Regulatory Consission,' Washington, D.C.
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.(5)
U.S. ATOMIC' ENERGY COMMISSION. " Begulatory Guide 1.4.
Assumptions Used for Evaluating the Pccential Radiological
~~
Consequences' of a Loss of Coolant Accident for Pressurized Water Teactors. Directorate of_ Regulatory Standards, Nuclear
,[
Regulatory Commaission, Washington, D.C.
20555 (June 1973).
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~
Admi2istration.. A p.ecurces tabs (July 1968).
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~
Plants.1 WASH-1400'(N3 REC-75/014), Appendix VI Calculation of Reactor, Accident Oonsequences." Nuclear Regulatory Commission, Wa shing t on,'. D. C.
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~
IDO-17261, AEC Research and Degelopment Report, Mathematics and g
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/
r s
D-69
~
b O
g_
/
p' y
, ^ -- sar -.a
-,-..,,._.,f.,
r
F 4
\\
\\
+
v' w
(9) ANNO, G. 81. AND M A. DORE. The Effectiveness of Sheltering as
~
a P stective Measure Against Nuclear Accidents Involving Cazeous Releases. Pacific-Sierra Research Corporation, prepared for the U.S. Environmental Protection Agency, Contract No. 64-01-3223 (December 1975).
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of the Task Group on Reference Man, ICRP Publication 23 Pergamon Press, New York (1975).
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~
Methodology and Sources of Iodine in the Human Diet."
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~
No. FDA 71-294 prepared for Division of Nutrition, 3ureau of Foods FDA. Federation of American Societies of Experimental Biology, 3ethesda, Maryland (1974).
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~
Journal of Medicine, 2C:653-468 (1956).
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~
" Iodine Intake in the United States: A Reassessment, J. Clin.
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~
6 (1960).
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~
Thyroid Uptake yot Re' aced to the Ingestion of White 3 read,"
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Journal of Nuclear Medicine, s
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Iodine:
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"A
~
Reevaluation of I Thyroid Uptake " Radio 1. 105:611-614 (1972).
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x J
G 4
.m
.m
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~
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~
New England Journal of Medicine, 280:1431-1434 (1969).
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~
Radioactive Iodine," Journal of American Medi:a1 Association, 3
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C., D. T. KOPP, AND W. W. 30VII. "Further Observations on the Normal Radioactive Iodine Uptake," Journal
~
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~
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A., T. H. CDDIE, AND J. C. BURROUGHS. " Thyroidal Radiciodine Uptaks *.sta Measurement in Infants," American
~
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~
I. A. LIKHTAREY. " Radioactive Iodine in the Problem of Radiation Safety," Atomi:dat, Moscow, 1972. AEC-tr-7536, U.S. Atomic Energy Commiission, Office of Infomation Services (1974).
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Dosimetry Data " pp. 133-156 in Medical Radionuclides Radiation Dose and Effects, R. J. Cloutier, C. L. Edwards, and W. S. Snyder, editors, AEC Symposium Series'#20 U.S. Atomic i
(
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~
ICRP Publication 2. Pergamon Press, New York (1959).
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~
Estimation," MIRD Pamphlet No. 10. Society of Nuclear Medicine (September 1975).
1 l
D-71
m (29)'U.S. DEPARTME:fr OF HEALTH, EDUCATICN AND WELPARE.
~
" Radiological Health Handbook."
U.S. Public Health Service (January 1970).
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~
with Shape and Size of the Thyroid," Health Physics Division Annual Progress Report for Period Inding July 31, 1975.
Oak Ridge National Laboratory, ORNL-5046 (September 1975).
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~
of the Uranium Fuel Cycle Fart II - Nuclear Power Reac'Jors."
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Agency (November 1973).
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3.,
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" Overview of the Reactor Safety Study
~
Ccnsequence Model," NUREG-0340.
U.S. Nuclear Regulatory Commission, Washington, D.C.
20555 (october 1977).
I 1
s0 t
i' l
.v... =ve e mn ema. zm m.u-D-72 l
--