IR 05000224/2003001
| ML20214A327 | |
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| Site: | Berkeley Research Reactor |
| Issue date: | 02/24/1985 |
| From: | Grill R, Martin J, Soffer L NRC |
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| RTR-NUREG-1150 NUDOCS 8705190392 | |
| Download: ML20214A327 (85) | |
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Q mga,3 i ANS/ ENS International Topical Meeting on Probabilistic Safety Methods-and Applications Volume 2: Sessions 9-16 Volume 2 San Francisco, California February 24-March 1,1985 Sponsored by American Nuclear Society Nuclear Reactor Safety Division Northern Califomia Section Cosponsored by
.l Atomic Energy Society of Japan '
Canadian Nuclear Society < Electric Power Research Institute European Nuclear Society
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Society for Risk Analysis i' 1 System Safety Society - Taiwan Section ANS in cooperation with l Intemational Atomic Energy Agency oECD Nuclear Energy Agency 'I
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Paper 128 3 AN EXAMINATION OF A GRADED RESPONSE STRATEGY IN ' I EMERGENCY PLANNING AND PREPAREDNESS L. Soffer, J. A. Martin, Jr., and R. P. Grill ( j U.S. Nuclear Regulatory Comission
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AN EXAMINATION OF A GRADED RESPONSE STRATEGY IN EMERGENCY PLANNING AND PREPAREDNESS Leonard Soffer, James A. Martin, Jr. and Richard P. Grill U.S. Nuclear Regulatory Commission Washington, D.C. 20555 INTRODUCTION AND BACKGRO'UND NRC Emergency Planning regulations, which were significantly upgraded in 1980 (1,1, continue to be a source of some controversy. This may arise in part from the misperception of uniform accident risk within the plume exposure Emergency Planning Zone (EPZ). Since promulgation of the regulations, additional risk studies have been performed (2_, 3, 4) showing significant spatial variation in risk over the EPZ, which implies that phased or graded planning and responses, implicitly recognized in the documents (5_, 6) which formed the basis for the present regulations, may be a reasonable strategy. The present study was initiated to investigate thi An objective of the present study was to ascertain a protective action strategy capable of dealing with a wide spectrum of accidents. Such a strategy should be flexible, depending on the nature of the accident, and should provide a i priority ranking of desired actions, rather than a pre-selected fixed risk objective, or dose criterion, regardless of accident severity. The priorities, l
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in order, should be to avoid early fatalities, reduce early injuries, and reduce other health effect This study also made use of the severe accident releases referred to as the Siting Source Terms (SST) (3, 4). Core-melt releases range from the very severe SST1 release with an estimated probability of about 1 x 10-5 per reactor-year, to the more moderate SST2 release with an estimated probability of about 2 x 10'0 per reactor-year, and the relatively benign SST3 release with an estimated probability of about 10-4 per reactor-year. These source terms employ the same methodology and are analogous to those used in WASH-140 Although an intensive research effort is underway to reassess accident source terms. NRC efforts are presently incomplete at this time (November 1984).
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. TIME FROM INITIATING EVENT TO START OF RELEASE-While the spatial variation in dose or risk, showing a sharp initial decrease is well known (5, 4), another important factor in emergency planning is the time from initiation of.an accident sequence until start of an actual release, sincethisaffects" warning" time. Reference 5 indicated this to be from "0.5 ' hours to one day," without further elaboration. More recent work (2) has
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generally confirmed this range for the most severe releases (SST)), but-provides additional insight by indicating that for most releases, time from initiation to start of release is about 2 hours or more. Tables 1 and 2 shows results (2) for the Grand Gulf and Sequoyah reactors.' For the reactors studied, the conditional probability of a severe sequence being a e fast-developing one, that is, where the time prior to release is less than 2
hours, ranged from about 3 to 30 percent, with a typical value of 15 percent.
[ Hence, an important conclusion arising from this work is that most (about 85 percent) severe accident releases would take longer than about 2 hours from initiation to releas . Table 1
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TIMING 0F SEVERE RELEASES FOR GRAND GULF PROBABILITY OF CORE-MELT SEQUENCES GIVING RISE TO SST1 RELEASES = 3.4 X 10-5 EVENT TIME OF RELEASE SEQUENCE PRO (MIN.) PROBABILITY
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j Table 2 TIMING OF SEVERE RELEASES FOR SEQUOYAH PROBABILITY OF CORE-MELT SEQUENCES GIVING RISE TO SST1 RELEASES = 3.6 X 10-5 , EVENT TIME OF RELEASE SEQUENCE PRO (MIN.) PROBASILITY V 5 x 10-6 38 mi .14 5 H- 3 2 x 10-5 110 mi .55 S HF- 8 S x 10-6 197 mi .14 S HF-8,f, 3 x 10-6 219 mi .085-8 3 x 10-6 238 mi .085 TIME VERSUS DISTANCE TO RECEIVE A DOSE AFTER RELEASE I Also of interest is the time for an individual at a given location to receive a given dose after a release comences. Such a time-dose-distance relationship provides insight as to the relative degree of urgency for response at different distances. This information was developed by generating data Q) on whole body dose as a function of distance with time after release as a parameter. This
! was replotted to show dose as a parameter. Examples for SST1 and SST2 releases for adverse weather conditions are shown in Figure 1 and 2. For the most severe release under adverse meteorological conditions, an individual at a ~
distance of 1 mile would receive a potentially life-threatening dose of 200 rem to the whole body about one-half hour after the beginning of the release. In contrast, individuals located 5 and 10 miles away would require exposure times of 3 to 10 hours, respectively, to receive the same dose. For less severe releases consisting primarily of noble gases (SST2) for the same meteorological i conditions, doses of 50 rem to the whole body (the threshold for early injury) would be received by an individual at 1 mile about I hour after release, while an individual at 4 miles would require 8 to 10 hours to receive the same dos For the least severe releases (SST3) doses (not shown) above the lower level
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Protective Action Guide (PAG) value of 1 rem whole body would not be expected i beyond distances of about 2 miles. These results show that individuals at
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!. RISK INSIGHTS A major conclusion is that the 10-mile plume EPZ represents a region not only l where risk varies significantly in magnitude, but where the need for protective L actions at close in distances would have a gree'9r degree of urgency, as well, in the event of an accident.-because of timing considerations. In particular, 5 .the region within about the first two miles of a reactor and a time frame q within about two hours after accident initiation appear to have some-significanc g A distance of about 2 miles has significance since: ;
N p e For many core-melt releases ($$T3), projected doses would not exceed the l j Protective Action Guide (PAG) levels beyond this distance; 1 L e For most core-melt releases (SST2 and SST3), projected doses would be i [ unlikely to result in early injuries beyond this distance.
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~ It should be noted that an early evacuation within a distance of two miles l would not be sufficient to avoid life-threatening doses beyond this distance for the most severe core-melt releases (SST1) under adverse meteorological h , h conditions, and that actions beyond two miles would be necessary in such cases, A time frame of about 2 hours has significance since:
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e For $$T3 core-melt releases, response times well in excess of this value f would be available before projected doses would be expected to exceed EPA Protective Action Guide (PAG) levels.
[: o For most core-melt releases, an evacuation within this tine would avoid
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o For the worst core-melt releases, warning times (prior to release) of about 2 hours or more are predicted for most (about 85 percent) severe q accident sequences.
ii ], PROPOSED PROTECTIVE ACTION STRATEGY j [h;- d Because of the significant spatial variation of risk as well as timing ] considerations given above, a protective action strategy taking these into .! consideration should more nearly meet the desired protective action objective d listed earlier. An emergency planning and response strategy intended to emphasizepromptactionsinthehighestriskportionoftheEPZ,whilesti{.1 , maintaining planning as well as the flexibility to carry out actions in the remainder of the EPZ, has been given the term " graded response." Since the.
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i i magnitude of a given release can vary significantly in severity but cannot be readily predicted prior to its actual occurrence, a precautionary evacuation to reduce the risk within-the highest risk portion of the_EPZ shows the greatest urgency and ought to be carried out within a time frame considered likely to avoid non-stochastic health effects. Protective ai:tions (both evacuation and sheltering) may be necessary beyond two miles, but appear to have a somewhat , lesser urgenc A graded response strategy based upon these risk insights appears to be a ' two-step strategy as follows:
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, In the event of a molten or degraded core condition, or upon declaration of a
j General Emergency: The imediate evacuation by everyone within about 2 miles, to be
accomplished within about two hours or less as an objective, should d be reconnended unless local weather or institutional concerns make ~ i
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evacuation infeasible; everyone within the remainder of the 10-mile <
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EPZ should be advised to seek available shelter and await further instruction . Accident assessment should continue, with monitoring of both plant and field conditions, and additional actions, including evacuation or relocation, as necessary, should be reconnended for persons in the
remainder of the EP l . q EVALUATION OF STRATEGY The graded response strategy outlined above was evaluated by determining the dose consequences to an individual from a spectrum of core-melt releases. The probabilistic dose distribution to individuals located 1, 2, 3 g5, 7 and 10 miles away from the reactor were obtained using one year of meteorological data to display the full variation of meteorology and distance over the EP Results show that for most core-melt releases (SST2 or SST3), an early evacuation out to 2 miles and sheltering elsewhere in the remainder of the EPZ (in a one or two story wood-frame house without a basement) with relocation 3 within 4 hours of ground exposure results in no early fatalities and very low risk of early injuries, as shown in Figure 3. For'the most severe releases, shown in Figure 4, early evacuation to 2 miles is insufficient to preclude early fatalities; however evacuation out to about 5 miles (necessary only in ! the downwind sectors), with sheltering elsewhere and relocation withth 4 hours , of ground exposure, would generally do s . l '
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It is concluded that the proposed graded response strategy takes suitable accoiant of the spatial and temporal risk variation within the plume EPZ. It places priority of response on the highest risk portion of the EPZ, while retaining flexibility in the remainder to accommodate a complete spectrum of accident releases.
> Although the specific response strategy outlined in this paper is based t solely upon WASH-1400 releases, it is clear that the conceptual approach arises fromfundamentalconsiderationsofriskpriorjtizationandisthereforereadily amenable to possible revisions in accident source terms. Hence, the concept of graded response is under serious consideration within NRC as a means by which emergency planning and response requirements may be evaluated, depending upon , the outcome of source term development ,
. REFERENCES Code of Federal Regulations Title 10 Part 50.47, " Domestic Licensing of
Production ana ut111zation Facilities," January 1984.
- Reactor Safety Study Methodology Applications Program (RSSMAP),
" nuntu/CR-Itsy, Vols.1-4, sand 14 National Laboratories, FeDruary 1981 - May 198 ' 4 'R. Blond, et al., The Development of Severe Reactor Accident Source Terms:
- 1957-1981, NUREG-uits, U.s. nuclear Regulatory GoMR1ss1on, NovemDer IV5 l D. C. Aldrich, et al., Technical Guidance for Siting Criteria Development, NUREG/CR-2239, Sandia National LaDoratories, DecemDer IVuZ.
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- Planning Basis for the Development of State and Local Government i Radiological Emergency Response Plans in support of Light Water Nuclear
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Power Plants, nuREu-uJVe, U.s. Nuclear Regulatory commission, Environmental Protection Agency, December 197 ; Criteria for Preparation and Evaluation of Radiological Emergency Response Plans and Preparedness in support or Nucisar Power riant, Nuntu-oose, Nuclear Regulatory Commission, Federal Emergency Planagement Agency,
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November 1980.
l D. Alpert, Private Comunication, Sandia National Laboratories, Oct.ober
- 1983.
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TECHNICAL BASES FOR A GRADED RESPONSE [. IN EMERGENCY PLANNING AND PREPAREDNESS i by " Leonard Soffer James A. Martin, J Richard P. Grill i 4'
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Manuscript Completed: November 1984 Date Published: December 1984
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FOREWORD
Although the NRC Emergency Planning regulations were significantly upgraded in
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1980 as a result of the Three Mile Island accident, this area continues to be a controversial and often misunderstood aspect of nuclear safety regulation.
! While .nany are aware of the requirement for planning within the 10-mile plume Emergency Planning Zone (EPZ), a significant source of misunderstanding arises . from the mis perception that all individuals in this zone are at an essen-tially equal degree of risk, without a clear understanding of the spatial variation of such risk or to what extent potential accident and release timing
affect ris As more recent research has become available, therefore, it becomes important to emphasize in a more explicit fashion the basis and insights associated with
, the concept of a " graded" or " phased" approach to emergency preparedness or response. This approach, implicitly recognized within the original planning documents, allows planners to concentrate and focus their efforts and resources l on those areas likely to require priority protective actions in an emergency, '
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while also permitting the flexibility of extending such actions, as neede l The information presented in this report provides a valuable basis for re- ! emphasizing the concept of " graded response", and should be considered as , supplementing the insights contained in the original planning document ' It must also be emphasized that the dose calculations presented herein rely ' upon projected radioactivity releases (" source terms") essentially the same as those from the 1975 Reactor Safety Study, WASH-1400, and do not reflect the ' considerable research effort which is underway, but presently incomplete, to reassess such potential accidental releases. Hence,.this report contains no '3 new source term information. If the " source term" research effort leads to a F technically defensible reduction of accident source terms, as many believe it a, will, it will make some of the accident consequences discussed herein more - pessimistic or conservative than warranted.' When such new source term informa- :
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tion becomes available, consideration will be given to revision of this report, '
- if the results so warran l Frank P. Gillespie, Director I
! Division of Risk Analysis and Operations Office of Nuclear Regulatory Research "
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A85 TRACT Additional risk studies performed since the current NRC emergency planning regulations were adopted in 1980 were examined to ascertain the individual variation of risk with distance and time and the potential need for protective actions within and beyond the 10-mile plume exposure emergency planning zone (EPZ). These studies used accident source terms essentially the same as those of the Reactor Safety Study since recent research on source term re-assessment - is presently incomplete. Timing of release of severe accident sequences as well as time-dose-distance relationships were examined to assess the potential degree of urgency of emergency response, and hence the relative priority required in planning. The results show that both individual risk as well as
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the potential degree of urgency is highest closest to the reactor, declines rapidly within about the first two miles, and then declines more slowly with increasing distances. The risk does not become zero at 10 miles, however. A graded or phased protective action response scheme which emphasizes priority for those members of the public at greatest risk is proposed and evaluated as a flexible strategy capable of dealing with a spectrum of accidental release .
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Table of Contents
.P_agg Foreword ........................................................... i Abstract ...... .................................................... iii >
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Table of Contents .................................................. v List of Figures .................................................... vii
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List of Tables ..................................................... ix
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Summary and Conclusions ............................................ x1 1. 0 Introduction .............................................,..... 1 2.0 Accident Source Terms ......................................... 3 3.0 Risk Profiles Within the 10 Mile' Plume Exposure > l Emergency Planning Zone and Beyond ............................ / ~ 3.1 Dose Variation vs. Diatance .............../.............. 7 3.2 Variation in the Risk of Indivicual Health Effects .......
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3.2.1 General ...........................................- 11 i 3.2.2 E a rl y Fa ta l i ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.2.3 Ea rly I nj u ry . . . . . . . . . . . . . . . . . . . c . . . . . . . . . . . . . . . . . . 14 3.2.4 Latent Cancer Fatality ...........'................. 17 3.2.5 Total Latent Heal th Ef fects . . . . . . . . . . . . . . . . . . . . . . . 17 3.3 Variation in Accident Timing vs. Distance ................ 17 3.3.1 Int Noduc ti o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.3.2 Release Delay Time of Severe Accident Sequences ... 17 3.3.3 Time Dose Distance Relationships .................. 19
, 3.3.4 Conclusions ....................................... 28 . .
4. 0 Protective Action Strategies .................................. 30 t
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4.1 Selection of a Protective Action Strategy ............... 30 4.2 Probabilities of Consequences'for Various Protective
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4.2.1 Introduction 36 , 4.2.2 Details of Protective Action Assumptions and Consequence Calculations......'................. 36
;! . .4. Results and Discussion ............................ (
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l 5.0 R e f e ren c e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . '. . . . . . . . . . . . . . . . 59
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List of Ficures PSSE 3.1-1 Average plume centerline whole body dose vs. distance, given an SST1 release (no protective action,1 day ground exposure) .................................................. 8 3.1-2 Average plume centerline whole body dose vs. distance, given an SST2 release (no protective action,1 day ground exposure) .................................................. 9 3.1-3 Average plume centerline whole body dose vs. distance, given an SST3 release (no protective action,1 day ground ' exposure) .................................................. 10 3.2-1 Individual risk of early fatality vs. distance given an '
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SST1 release ............................................... 12 3.2-2 Individual risk of early fatality vs.. distance given an SST2 release ............................................... 13 ; 3.2-3 Individual risk of early injury vs. distance given an SST1 release ............................................... 16 3.2-4 IndiviCJa1 risk of early injury vs. distance given an SST2 release ............................................... 18 3.3-1 Time-dose-distance relationship given SST-1 release and ,
"D" stability with 10 mph wind ............................. 23 3.3-2 Time-dose-distance relationship given SST-1 release and a "F" stability with 5 mph wind .............................. 24 3.3-3 Time-dose-distance relationship given SST-2 release and
"D" stability with 10 mph wind ............................. 25 3.J-4 Time-dose-distance relationship given SST-2 release and .
"F" stability with 5 mph wind .............................. 26 3.3-5 Time-dose-distance relationship given SST-3 release and i
"F" stability with 5 mph wind .............................. 27 4.2-1 Probability of an individual at a given distance receiving l a whole body dose in excess of the value shown, conditional
'
upon occurrence of an SST1 release and shelter plus 4 hr ; and exposure ............................................... 40 4.2-2 Probability of an individual at a given distance receiving a whole body dose in excess of the value shown, conditional upon occurrence of an SST1 release and evacuation at 2 mph P at time = 0 ................................................ 41 4.2-3 Probability of an individual at a given distance receiving a thyroid dose in excess of the value shown, conditional upon occurrence of an SST1 release and shel ter pl us 4 hrs. ground exposure . . . . . . . . . . . . . . . . . . . . . . . . 4.2-4 Probability of an individual at a given distance receiving a thyroid dose in excess of the value show conditional upon occurrence of an SST1- release and
,
evacuation at 2 mph at time of release . . . . . . . . . . . . . . . . . . . . . 4.2-5 Probability of an individual at 3 miles receiving i a whole body dose in excess of the value shown, conditional upon occurrence of an SST1 release and shelter plus I hr. ground exposure . . . . . . . . . . . . . . . . . . . . . . . . . 47 vii
, ..
. . .
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-
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, -
; List of Figures !
" *
(cont.)
Pagg
,
4.2-6 Probability of an individual at 3 miles receiving a thyroid dose in excess of the value shown, conditional upon occurrence of an SST1 release and shelter plus I h ground exposure ............................................ 48 4.2-7 Probability of an individual at a given distance receiving a whole body dose in excess of the value shown, conditional upon occurrence of an SST2 release and shel ter plus 4 hrs. ground exposure . . . . . . . . . . . . . . . . . . . . 49 4.2-8 Probability of an individual at a given distance L receiving a thyroid dose in excess of the value shown, conditional upon occurrence of an SST-2 release and shelter plus 4 hrs. ground exposure ........................ 50
4.2-9 Probability of an individual at a given distance receiving a whole body dose in excess of the value shown, conditional upon occurrence of an SST2 release and shelter plus 8 hrs, ground exposure .................... 53 4.2-10 Probability of an individual at a given distance receiving a thyroid dose in excess of the value shown, conditional upon occurrence of an SST2 release , and shelter plus 8 hrs. ground exposure .................... 54 , 4.2-11 Probability of an individual at a given distance receiving a whole body dose in excess of the value , shown, conditional upon occurrence of an SST2 release and shelter plus 12 hrs. ground exposure ................... 55 4.2-12 Probability of an individual at a given distance ,
~
receiving a thyroid dose in excess of the value shown, conditional upon occurrence of an SST2 release and shelter plus 12 hrs. ground exposure ................... 56 4.2-13 Probability of an individual at a given distance receiving a whole body dose in excess of the value shown, conditional upon cccurrence of an SST3 release and shelter plus 12 hrs. ground exposure . . . . . . . . . . . . . . . . . . . 57 4.2-14 Probability of an individual at a given distance receiving a thyroid dose in excess of the value shown, conditional upon occurrence of an SST3 release and , shel ter pl us 12 hrs. ground exposure . . . . . . . . . . . . . . . . . . . . . . . 58
,
viii ,
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,
LIST OF TABLES
.
P,,agg t
! Accident categories covered by the NRC siting source 2. 2 - terms ......................................................... 4 .
NRC source terms for si ting analysi s . . . . . . . . . . . . . . . . . . . . . . . . . . 5
- Sensitivity of fatal and injury distances to release i magnitude ..................................................... 15 3.3-1 Timing of severe releases for- Oconee . . . . . . . . . . . . . . . . . . . . . . . . . . 20
- ) 3.3-2 Timing of severe releases for Calvert Cliffs .................. 20
] 3.3-3 Timing of severe releases for. Grand Gul f . . . . . . . . . . . . . . . . . . . . . . 21~ i 3.3-4 Timing of severe releases for Sequoyah ........................ 21 1~ j Recommended protective action strategies and rationale ........ 32-35 b
:
4.2-1 Protection factors used in the calculations ................... 37 4.2-2 Key individual whole body dose distribution values, SST-1 and
.
relocation after 4 hours ...................................... 42 4.2-3 Key individual whole body distributions values, SST-1 and evacuation at time of release (2 mph) ......................... 42 4.2-4 Key individual thyroid dose distribution values, SST-1 and relocation after 4 Hours ...................................... 4.2-5 Key individual thyroid dose distribution values, SST-1 and evacuation at time of release (2 mph) ...............,.........
' 4.2-6 Key individual whols body dose distribution values, SST-2 and relocation af ter 4 hours ground exposure . . . . . . . . . . . . . . . . . . . . . . 51 4.2-7 Key individual thyroid dose distribution values, SST-2 and relocation after 4 hours.plus 4 hours ground exposure ......... 51
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Summary and Conclusions A re-assessment of accident risk within the 10 mile plume exposure emergency planning zone (EPZ) (NUREG-03961, 10 CFR Part 503, NUREG-06544) and the protec-a tive actions to be taken within this zone has been performed. This re-assessment has been based upon extensive additional risk studies that were not available at the time the NRC emergency planning regulations were~ promulgated in 198 (See NUREG-0773s, NUREG/CR-1659s, NUREG/CR-22397, NUREG/CR-23268, NUREG/CR-29258 a recent Final Environmental Impact Statements for nuclear power plant operating licenses issued since June 1980 (See NUREG-0974, for example) and testimony j before the Commission on reactor risk such as that concerning the Indian Point - plant in February, 1983).
k The re-assessment has made use of analyses which have considered a full spectrum of potential accidents, up to and including a range of core-melt event ] Among these were very severe releases resulting from a core-melt and an early
} breach of containment directly to the atmosphere. The release characteristics r "
used to describe the range of accidents considered have made use of the " Siting ". Source Term" (SST) terminology (SST1, SST2, etc.) described in NUREG-0773s and the Sandia siting study (NUREG/CR-2239)7 It must be emphasized that the g re-assessment in this report is based solely upon these existing source terms, l essentially those of WASH-1400 (NUREG/75/014)2 Although an intensive research-
. '
effort is underway to re-assess the potential magnitude and timing of accidental radioactivity releases (" source terms"), this effort is presently incomplet , If the " source term" research effort leads to a technically defensible reduction 1 of accident source terms, as many believe it will, it will make some of the "I accident consequences discussed herein more pessimistic or conservative than 1 warranted.
- 4 .
A major objective of this assessment was to determine a protective action - j[ strategy capable of dealing with a wide spectrum of accidents. The basic
; radiation protection objectives associated with such a strategy must be flexible, l depending upon the nature of the accident, and must provide a priority ranking -
!;l of desired objectives, rather than providing a single pre-selected fixed risk ., objective, or dose criterion, regardless of accident severity. A set of such ! !j objectives nas recently been stated in succinct fashion by the ICRP17 These
'
- establish differing priorities in establishing strategies to prevent
< non-stochastic health effects, i.e., those that can appear in identifiable i individuals above a threshold dose such as early fatalities or early injuries,
and reduce stochastic health effects, i.e., those that exhibit no threshold
:) effect and which can be expected to appear randomly among the exposed populatio ; These objectives are: )
j (a) " Serious non-stochastic effects should be avoided by the introduction of
: countermeasures to limit individual dose to levels below the thresholds for these effects.
- j (b) The risk from stochastic effects should be limited by introducing counter- l i measures which achieve a positive net benefit to the individuals involve l (c) The overall incidence of stochastic effects should be limited as far as I
!i
- '
reasonably practicable by reducing the collective dose equivalent." l ,.
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The reassessment examined risk as well as dose variation with distance, accident - severity, timing considerations (from sequence initiation to estimated time of release), and time after release in which a given dose would be received at a given distance (time-dose-distance relationship).
Both individual risk and dose are highest close to the reactor, decline rapidly at first, and then more slowly with increasing distance. At a distance of two'
~
miles the average radiation dose from a given release would-be about 20 percent of its value at one-half mile. This behavior is the result, primarily, of
' '
increased atmospheric dilution or dispersion with distance which is inherent
' in nature and which reduces the atmospheric concentration, and hence the dose, of any released radioactivity. While the individual dose from a given release
- would be lower by about a factor of 50 at a distance of ten miles vs. that at a
[ a distance of one-half mile (the nearest boundary of typical LWR exlusion areas), the effects become magnified for those health effects where a high f' threshold dose is required before an effect is observed, i.e. early injuries '
and fatalities. Hence, for the most severe release without protective actions, the individual risk of early fatality would be reduced by about a factor of a more than one hundred at a distance of ten miles vs. its initial level at i one-half mile. Because the risk decreases continuously with distance, however, 1 they do not become zero at a distance of ten miles.
Accident timing considerations were also reviewed, based upon additional risk
studies performed since WASH-1400 (NUREG/75/014)2 These indicate that for the most severe releases (SSTI), the estimated time from accident sequence initiation to radioactivity release ranges from values significantly less than
; one hour to times on the order of one day, with times of 2 to 3 hours being q typica These studies also showed that the conditional probability of a
.i severe release sequence being a fast-developing ~one, that is, where the time from initiat4on to release would be less than 2 hours, ranges from 3 to 30 f percent, with a typical value of 15 percen Risk studies were also performed to assess the time after a release begins for c an indi'vidual at a given distance to receive a given dose. Such parametric curves, displayed as time-dose-distance relationships, provide insight as to
: the relative degree of urgency for response at different distances. For the most severe core-melt releases (SSTI) under adverse meteorological conditions, an individual at a distance of 1 mile would receive a potentially life-threat-aning dose of 200 rem to the whole body about one-half hour after the beginning . of the release. In contrast, individuals located 5 and 10 miles away, respec- l
' tively, would require exposure times of 3 and 10 hours, respectively, to l receive the same dose. For less severe releases (SST-2) consisting primarily l
'
of noble gases and under adverse meteorological conditions, doses of 50 rem to '
, the whole body (taken as the threshold value for early injury) would be received by an-individual at 1 mile in about I hour after release, while an individual ; at 4 miles would require 8 to 10 hours to receive the same dose. These results l show that individuals at close-in distances within the plume EPZ not only ;l would receive higher doses, but that they would do so within a shorter period i of time, as well.
.t
! Based upon these results, the major conclusion emerging from this study is that the 10-mile plume EPZ represents a region not only where risk varies significantly in magnitude with distance but where the need for protective
'e Xii
.- - . - - , 7.- _ ___ _ 3 3-
- - _ _ _ _ _ - . - - - _ - _ - _ _ - - .
q jm actions at close-in distances would be a greater degree of urgency (given a
~
declaration of a General Emergency).as well, because of accident timing consid-
.
erations, Consequently, emergency planning as well as response strategies a should appropriately reflect such a variation in the magnitude and timing of g risk with distance.
a l It is recommended, based on these risk considerations that emergency planning
- i - and protective actions to be taken should be graded or phased within the EPZ -
with ' respect to both distance and timing.
y Since core-melt releases (" source terms") can vary significantly in severity,
- but the magnitude of a given release cannot be readily predicted prior to its actua1' occurrence, primary attention or priority should be given to the early initiation of pre planned actions in the event of a core melt accident to reduce the risk within the highest risk portion of the EPZ. This is judged to y;, be that region within about the first 2 miles of an LW l This difficulty in determining the ultimate severity of an accident once plant l conditions have gone so far beyond the design basis that core degradation is j indicated, plus the possibility that this highly unlikely accident sequence
, may also be fast developing, led to a. primary recommendation in NUREG-06544
!
This recommendation was, and is, that nuclear power plant emergency. plans ], develop predetermined indicators of core degradation precursors, called Emer-1 gency Action Levels (EAL's). When these are exceeded, a General Emergency
: should be declare This declaration, in turn. should initiate preplanned emergency action ; The preplanned action of choice should be a precautionary evacuation of-the highest risk region to be commenced prior to any plant release.
] The evacuation of the first two miles should be planned with the objective of
,. being accomplished within about 2 hour The capability to carry out additional protective actions, including evacuation, l as necessary, should be retained throughout the remainder of the plume EPZ, l l but should receive lower priority. To enhance this capability, members of th '
l public located beyond 2 miles should be advised to seek available shelter and
-
to stay informed of additional developments. It should also be recognized
-
that protective actions might be warranted at distances beyond ten miles, in M unusual circumstances.
a j At the time of an accident, decisionmakers should, of course, take into consid-eration actual local conditions that may make an evacuation temporarily infeasible, l ' such as impassable road conditions due to adverse weather, and that might present a greater risk to the general public, if attempted, than radiological conditions warrant. Under such conditions, authorities should encourage sheltering and should also consider the auxiliary benefits provided by ad hoc j
,
respiratory protective measure A distance of about 2 miles has significance for the following reasons:
" - For many core-melt accidents (those without a direct release to the i atmosphere), projected doses would not exceed the Protective Action Guide (r (PAG)11 levels beyond this distance;
, xiii
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For most core-melt accidents (those without early failure of. containment), projected doses would be unlikely to result in early injuries beyond this ; distance; !
-
Early precautionary evacuation by people within this distance, and immediate sheltering beyond, would provide a large reduction in risk to the highest risk group. It would also provide additional time to assess the developing situation further'and to decide upon and implement any required protective actions beyond this distanc It should be specifically noted that an early evacuation within two miles l would not be sufficient to avoid life-threatening doses beyond this distance under adverse meteorological dispersal conditions, for the most severe core-melt accidents (those involving prompt failure of containment) and that actions beyond two miles should be necessary in such cases. During such an event it is expected that emergency planning authoritiies would recommend immediate' l , evacuation, from shelter, of people within about five miles in a downwind i direction even though a release were taking plac A time frame of about 2 hours has significance for the following reasons:
.
Since about 1% to 2% of all core-melt accidents (or 10% to 20% of the most l severe sequences) are estimated to result in severe releases that will also be !
,
fast-developing (warning time less than 2 hours), an evacuation time of 2 ' hours for individuals within the first two miles can provide a high, but not
absolute, degree of assurance that life-threatening doses would not be received in the event of a core-melt. For this reason, the recommended planning goal
-
of 2 hours should not be construed to mean that individuals at risk could not i be expected to evacuate more quickly or that they should not be encouraged to
,
do so. In other words, it is strongly recommended that the 2 hour evacuation
] goal be used as criteria for evaluating the level of preparedness only, and y should not be used during an actual accident, as that might lead to an unwar- ,
ranted lack of urgenc For many core-melt accidents, response times well in excess of this value , would be available before projected doses would be expected to exceed EPA l Protective Action Guide (PAG)11 level For most core-melt accidents, an evacuation within this time would avoid l . doses capable of producing early injuries in the populatio l
' -
For the worst core-melt accidents, warning time (prior to releases) of 2 hours or more are predicted for acst (about 80% to 90%) severe accident , sequence ' ' l Based upon the above results of the risk studies, a two-step protective action strategy is proposed as follows:
:
T IN THE EVENT OF A PLANT CONDITION WHERE A MOLTEN OR DEGRADED CORE' CONDITION IS OBSERVED OR PROJECTED, OR WHERE ADEQUATE CORE COOLING CANNOT BE REASONABLY fo ASSURED, OR UPON THE DECLARATION OF GENERAL EMERGENCY: REC 0 MEND IM EDIATE PRECAUTIONARY EVACUATION BY EVERYONE WITHIN ABOUT TWO MILES. THIS EVALUATION TO BE ACCOMPLISHED WITHIN ABOUT TWO HOURS OR LESS WHERE AT ALL FEASIBL xiv
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EVERYONE WITHIN THE REMAINDER OF THE TEN MILE EPZ SHOULD BE ADVISED TO SEEK AVAILA8LE SHELTER AND REMAIN INDOORS UNTIL FURTHER NOTIC ' ACCIDENT ASSESSMENT SHOULD CONTINUE, WITH MONITORING OF BOTH PLANT AND FIELD CONDITIONS. AS THE ASSESSMENT CLARIFIES THE SITUATION, FURTHER J ACTIONS SHOULD BE TAKEN, SUCH AS INFORMING THE SHELTERED POPULATION PROMPTLY AS 10 THE NEED FOR CONTINUING TO SHELTER OR RECOMMENDING THAT THEY PREPARE TO EVACUAT The potential benefits of this strategy was evaluated by examining individual consequence estimates (as measured in whole body and thyroid doses) for a spectrum of postulated core-melt events. For most core-melt releases, an early evacuation out to 2 miles and sheltering beyond this distance (in a one or two story wood-frame house without a basement) followed by a relocation of
-
people before they accumulate the equivalent of 4 hours of ground exposure
. i results in no early fatalities and very low risk of early injuries or long term health effects. For the most severe releases postulated, an early evacuation , out to 2 miles, followed shortly (within about I hour after an actual major .
release) by evacuation out to 5 miles in the downwind sectors only, with shel-
-
tering elsewhere and relocation from contaminated areas within 4 hours of ground exposure, would avoid early fatalities and provide a. low risk of early injuries or long-term health effect ,
!
h' l A distinction should be noted throughout this report in the discussion of ' evacuation stategies recommended by the authors, between the early precautionary
'
"j evacuation of the first two miles and the best evacuation strategy to be , followed when an actual severe release is expected or in progress. The first, ' l early, precautionary evacuation should be an automatic, preplanned response to
'
the severely degraded plant conditions that would trigger declaration of a
.
General Emergency. The second, subsequent strategy that might involve evacuation J should be followed only after the plant situation has clarified, and as a more ,j accurate assessment of the poteatial magnitude of the threat can be made. -The j first strategy would provide for a major reduction in individual risks of , severe non-stochastic and stochastic health effects. It also would clear the ' s) way for the second phase of preplanned but more flexible protective action ! decisions by authorities on the scene that consider actual conditions at the l
, tim .
It is concluded that the proposed strategy can be very effective in meeting the basic radiation protection objectives and is flexible enough to accommodate
-
a complete spectrum of core-melt events. It can be effective because a) those l at greatest risk would be given the most immediate (early) attention, b) emergency response resources can be used most effectively by concentrating response in a graded, or phased manner and c) its simplicity can lead to a high confidence that it can be well understood and that it would wor . a i
.
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j , 1.0 Introduction The NRC Emergency Planning regulations were.significantly upgraded in 1980, largely as a result of the Three Mile Island' accident. These regulations required that emergency planning be instituted around every nuclear power plant in the U.S. for a plume exposure pathway planning zone having a radius l of about ten miles, and an ingestion exposure pathway p14nning zone, having a radius of about 50 miles (10 CFR Part 50, Appendix E)3 The bases for these recommendations were given in a report by a joint NRC/ EPA Task Force entitled
" Planning Basis For the Development of State and Local Government Radiological Emergency Response Plans in Support of Light Water Reactor Nuclear Power ;
Plants", NUREG-0396, published December, 1978.1 Further elaboration was also ( published in " Criteria for Preparation and, Evaluation of Radiological Emer- l gency Response Plans and Preparedness in Support of Nuclear Power Plants", ! NUREG-0654/ FEMA-REP-1, Rev. 1, publ.ished November, 198 ' l Theroleofemergncyplanninghasbecomeincreasinglycontroversialsincethe accident at TMI In practice, virtually all of the controversy has centered around the 10 mile plume exposure pathway zone (EPZ), and may have arisen largely because of misperceptions regarding the nature of accident risk within this zone. These misperceptions, simply stated, are that:
(1) All individuals within the 10 mile plume EPZ, regardless of their loca-tion, are exposed to an essentially equal degree of risk, and (2) An expeditious evacuation of this entire area is the only effective .
protective action to be planned or carried ou ! In addition, some have claimed 22' that a 10 mile planning radius is simply i inadequate and should be extended outwards, perhaps to 20 mile I
' '. It is clear from a perusal of the reference documents leading to the regula-tion that there was a clear awareness of the significant spatial variation in i ; risk (see NUREG-03961, page 118, for example), as well as an awareness (see l NUREG-06544, page 9, for example), that actions should be concentrated first j ,
in the near or close-in regions and extended outward, as necessary. There was
,
also a clear recognition that protective actions might be required beyond 10 l miles, in unusual circumstances (see NUREG-03961, pp. 16 and I45, for example).
, Since the Emergency Planning regulations have been promulgated, a number of addi-
; '
tional risk studies and licensing assessments have been performed.s.s.7.s.sexo As a result, it was felt that a re-assessment of the nature and timing of 1 accident risk within the plume EPZ, using the results of these recent studies, might provide additional insight for emergency plannin l It should be emphasized that only existing accident source teams, essentially l the same as those used in the Reactor Safety Study, WASH-1400,2 have been i employed in this study. Although an intense research effort is underway to
, re-assess these accidental radioactivity releases, this effort is presently
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.
incomplet If the " source ters" research effort leads to a technically defensible reduction of accident source terms, as many believe it will, it
will make some of the accident consequences discussed in this report unduly pessimistic and more conservative than warranted.
j In the sections that follow,.this report' discusses risk as well as dose varia- -! tion with distance, projected accident timing considerations from sequenc initiation to estimated time of release, and the time-dose-distance relation-
; ships that would exist after a given release. From these observations, a .. proposed protective action strategy is derived and examined which is intended to place priority where risk is highest while still providing for a flexible - response to a wide range of possible accidents. This is referred to as the i' concept of " graded" response. It should be emphasized that the material and -
conclusions presented in this report should be viewed as supplementing, and j , not replacing, those given in NUREG-03961 and NUREG-06544
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i ! j 2.0 Accident Source Terms )
'
Since a major objective of this report is to examine and assess individual )
- accidentriskwithinthe10-mileplumeEPZinsomedetail,asuitable{ tarting !
, point for examining such accident risk is needed. Although NUREG-0396 - l
- examined risks from both design-basis as well as severe ac
- idents, this study
-
will focus only upon potentially severe accidents since the consequences of l such events, although less probable than the design-basis accidents, are : generaly conceded to _ dominate the risk as well as to have a " reach" which
, extends a greater distance.
- i The starting point for assessing consequences from severe accident sequences j are accident " source terms." These comprise a set of values representing the ,
3 possible quantities and types of radioactive materials that could be released .j to the environment from a sequence or group of similar possible accident 1 sequences. Tabulations of source terms, in addition to the data mentioned
'
above, may also contain additional information such as the probability of the q release, the estimated warning time prior to release, the release duration and
. the energy content.
![ Sets of source terms for severe accident sequences were first given in the
'
Reactor Safety Study, WASH-14002, which provided a tabulation of severe acci-- i dent releases ranging from PWR 1 to PWR 9 for a Pressurized Water Reactor , .l (Surry) and ranging from BWR 1 to BWR 5 for a Boiling Water Reactor (Peach ' Bottom). As additional' Probabilistic Risk Assessment (PRA) studies were
- , performed after WASH-1400, additional plants and severe accident sequences , were investigated. These developments ~are discussed in more detail in j NUREG-0773s which also detailed.a suggested generic set of source terms that j would be suitable for providing insight for siting and emergency planning i studies. These have been referred to as the " siting source terms" (SST), and I range from the very severe SST-1 release to the relatively benign SST Table 2.1 provides a delineation and qualitative distinction between these 'j releases, while Table 2.2 provides data on the quantities and types of isotopes released as well as the release duratio , , The siting source tert.s (SST's) were applied in the Sandia Siting Study (NUREG/CR-2239)7 to examine the consequences of such releases at each of 91 j U.S. sites. The insights gained from this study are of value for emergency j planning, as wel , Accident source terms in the form of the siting source terms (SST) were used , for this study both because they incorporate the research effort on additional plants and postulated accident sequences beyond those of WASH-1400. The SST :' grouping are somewhat easier to conceptualize than those of WASH-1400. At the same time, the reader should bear in mind that the SST's are highly synthetic }I and that different severe accident sequences, each of which might be reason-j ably categorized as leading to an SST 1 release, for example, might neverthe-
.] less differ in some degree from the values in Table 2.2. It should be noted
- j that the postulated consequence models in this report are conditional upon a i -
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* .
Table 2.1 Accident categories * covered by the NRC siting source terms
SST1 Severe, early direct breach of containment. Core Melt. . Essentially ! involves loss of all installed safety feature Propulsion of large fractions of the core inventory of radionuclides into the atmospher Similar to PWR-2 of the Reactor Safety Stud SST2 Containment fails to isolate. Core Melt. Containment fission product release mitigating systems (e.g. , sprays, suppression pool, fan coolers) operate to reduce the release. Small fractions
[ of the core inventory released to the. atmosphere. Similar to PWR-5 of the Reactor Safety Study.
'
!! SST3 Containment fails to isolate by late basemat melt-throuch. Core
- 1 l
Melt. All other release mitigation systems function as designed, Very small fractions of the core inventory leak into the atmos-phere.' Long-term leakage of radionuclides into the hydrospher i SST4 Containment systems coerate but in a somewhat degraded mod Limited to moderate core damage. Containment is not breache ' Similar to PWR-9 of the Reactor Safety Stud l SSTS Containment functions as desianed. No failures of engineered safety features beyong those postulated pursuant to 10 CFR i Part 100 (siting criteria) are assumed. The most severe acci-dent in this group includes substantial core mel ~
*The accident at TMI-2 March 28, 1979 does not fit neatly into any of these categories. Although severe core damage was experienced, such as in SST3,
. the operation of the containment safety features severely restricted j' releases to the environment. Offsite consequences falls into the SST4 or SST5 categor i
'
i
..
- i .
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- !
,
,
- i ii
- !,
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. _ . . _ . - -- - -
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.
-t-
.;
*
Table 2.2 NRC Source Terms for Siting Analysis . ..
Release Characteristics a Source Term
: I j SST1 SST2 SST3 SST4 SSTS l
.
.; ~ Accident Type Core Melt Core Melt Core Melt Gap Release Gap Release Containment Failure Mode Overpressure H2 Explosion -
'
- -
,
or Loss of i' Isolation ,
,
Containment Leakage Large Large 1%/ day 1%/ day 0.1%h !
!l .5 ' .j l Time of Release (hr) 3 1
Release Duration (hr) 2 2 4 1 1 ] ' '
, Warning Time (hr) .5 - -
t
'
Release Height (meters) 10 10 10 l'0 10 ,
*
Release Energy 0 0 0 0 0 Inventory Release Fractions f'
.l Xe-Kr Group , x 10 8 3 x 10 8 3 x 10 7
- ) . ,
I Group 0.45 , 3 x 10 8 2 x 10 4 1 x 10 7 1 x 10 s ,,
.' Cs-Rb Group 0.67 9 x 10 3 1 x 10 s 6 x 10 7 6 x 10 s .
- ! i
; '
Te-Sb Group 0.64 3 x 10 2 2 x 10 5 1 x 1 x 10 18
~!,
Ba-Sr Group 0.07 1 x 10 3 1 x 10 8 1 x 1011 1 x 10 2 ll Ru Group 0.05 2 x 10 3 2 x 10,a 0 0 l
:! ! ;j La Group 9 x 10 8- 3 x 10 4 1 x 10 s 0 0 l
- >
'
,j
' As defined in the Reactor Safety Study [2].
:1
-
l
. . . .-. - ._ . __ ._ --
_ . . _ _ _- . _ _ _ . _ _ _-- . . _ _ _ . _ _ . . _ .
- . .- ' , severe accident occurring. This is a highly unlikely event. Core melt events are estimated to have a probability of occurrence of once in every 10,000 reactor years. A core melt resulting in a severe release (SST-1) would be even I more unlikely with a probability estimated as once in every 100,000 reactor i L year ' - Only the accidents involving core melt releases, i.e. , SST-1, SST-2 and SST-3,
- are discussed in this report as they are the only ones with the potential for .
severe consequences. The probability of a core melt resulting in a relatively benign SST-3 release is estimated to be about 70%. About 20% are estimated to '
-result in SST-2 releases and 10% or less would be estimated to be the most i severe SST-1 variety. As a practical matter, it may be difficult or even !
impossible for a reactor operator to predict releases for an accident that has gone well beyond the design basis of the plant, particularly during the early stages of the acciden It is the staff intent that nuclear power plant emergency plans require that the operator declare a " General Radiolegical Emergency" at that point rather than waiting more precise assessment. This
*
prudent declaration would activate immediate emergency response procedures that would minimize possible consequences of even the most severe accident category. This has important implications for selection of an appropriate protective action strategy, as will be discussed later in _this repor l Finally, it must also be emphasized that the accident source terms used in this study do not reflect the considerable research effort which is underway, but presently incomplete, to reassess the potential for such accidental releases. If such a source term research effort leads to the conclusion that severe accident source terms have generally been overestimated, it will make some of the accident consequences (in particular, those for the SST1 release) more pessimistic or conservative than warrante .
.
n i t
6
! ! - . - :
'l
. . . . .. . - - - - _-.: . _ _ _ _ _ , _ - - n - .__. -- : , . - ~ . c x_n_ _ _ ___ .n
. _ _ _ . __ _ _ _ .__ -_ .. . . - - - . - - - - - - - - ~ - * ,
r " 1, -
~i :
i 3.0 Individual Risk Profile Within the 10-Mile Plume Exposure EPZ and Bayond t j * This section discusses the magnitude and variation of individual (conditional) risk that exists within the 10-mile plume exposure Emergency Planning Zone
. (EPZ), as well as beyond it. Section 3.1 discusses the variation of dose as a l function of distance. Sections 3.2 and 3.3 discuss the variation of health
- 3
'* effects and time-dose-distance relationships, respectively. It is emphasized that only risks conditional on accidents occurring will be discussed. Abso-j lute risks are not discussed or estimated.
'I 3.1 Dose Variation with Distance I.
- 1 The variation of projected dose with distance, given a severe accidental j release, has been analyzed and reported in NUREG/CR-22397 . Reference 7 dis-i played the mean whole body dose vs.' distance to an individual,* given an j SST1, SST2 or SST3 release, on a log-log plot. For clarity these have been
: replotted on a linear scale, as Figures 3.1-1,'3.1-2 and 3.1-3. Note that
,j these projected doses assume no emergency response. Although the absolute
; doses from these three different release categories differ by about a factor
,' I of one thousand, they all display the same general variation with distance; in fact, the natural effects of atmospheric dilution and dispersion would make j the effects of almost any release vary in the same relative wa j From an initial value at a distance of 0.5 mile (taken as the typical exclu-i sion boundary distance), these curves show that the individual dose drops off I sharply with distance at first, then the slope continues to decrease more D slowly. At a distance of two miles, for. example, the dose is about 20% of the lli value at 0.5 mile, while at a distance of ten miles, the mean whole body dose is about 2% of its initial value. This illustrates the important point that, - although the projected dose varies continuously with distance, most of the
!<
decrease over the 10 mile plume exposure emergency planning zone (EPA) occurs ! very close-in to the reactor, with about 80% of the decrease from 0.5 mile to j, 10 miles occurring within the first 1.5 miles.
I
- j It is also important to recognize that projected dose levels may still be
.; significant in absolute terms at distances of 10 miles and beyond, even though *
there has been a large decrease with distance. For example, at a distance of
- j 10 miles the whole body doses for an SST release is about equal to the pro-t posed Environmental Protection Agency (EPA) Protective Action Guide (PAG)11 I levels, i.e., 1 to 5 rem whole body and 5 to 25 rem thyroid. . For an SST1
! release, the while body dose is in excess of the upper PAG levels out to about i 40 miles. This was well understood at the time the 10 mile EPA was proposed in NUREG-0396 * ,
i l ,, *These doses apply to an individual directly downwind in the plume centerlin ; g l 4.
ii li ,!
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DISTANCE, MILES t Figure 3.1-1 Average Plume Centerline While Body Dose vs. Distance, Given
an SSTI Pelease (No Protectiva Action,1 Day Ground Exposure)
'
- _ - _ _ . . _ _ _ _ _ .
- .. . . . - - . . - - - . . . . =--...-.-.~.-..n----------- . - - - - - - - - , , - - - - - . - - - - - - - - - - -
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h DISTANCE, MILES ;
. !.
l Figure 3.1-2 Average Plume Centerline Whole Body Dose vs. Distance, Given i
: an SST2 Release (No Protective Action,1 Day Ground Exposure) ,
t
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I I I i l I i I i : I 5 7 8 9 0 ' ! 0 1 2 3 4 6 L DISTANCE, MILES -
- ,
j Figure 3.1-3 Average Plume Centerline Whole Body Dose vs. Distance Given
.
l,* an SST3 Release (No Protective Action 1 Day Ground Exposure) ,
_ . _ . ___ .__ . _ _ . _ _ - _ - . .__ ___
. - _ . . . . _ _ _ . _ _ - - - ~ . . - . . . .
. . . . _ ._____-____.--._..-
. . . - . . . . _ .
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,
3.2 Variation of Health Effects with Distance - 3.2.1 General This section discusses the distanca variation of some of the major radiation-induced health effects such as those fcr early fatality, early injury and latent cancer fatality, given various accidental releases. The intent is to
- examine distance relationships primarily for those non-stochastic effects having the highest priority or urgency for planning and response assumption It is not intended to be a complete discussion of all health effects associ-ated with radiation exposure and has knowingly omitted discussion of a number of these, such as genetic defects, sterility, fetal development, or mental retardation in utero which may manifest themselves. In addition, the discus-sion of health effects has also implicitly assumed dose-nealth effect relation-ships that are generally attribut
- ble to a normal, healthy adult populatio The reader should be aware that there are also sensitive elements in the population such as pregnant women, the sick and the elderly where such relation-ships may not be applicable. For a further discussion of health effects, the reader is referred to References 2,- 13, 22 and 2 It is also important to note that there may exist other adverse effects of accidents which would require later post-accident responses. In particular, deposition of particulate activity may cause significant land contamination requiring possible decontamination efforts and possibly involving interdiction of buildf 7gs and land and impoundment of milk and other crops. Such countermeasures may extend well beyond the ten mile plume-exposure EPZ and into the 50-mile ingestion pathway EPZ. Depending upon the severity of the accident and the countermeasures taken, significant numbers of latent cancer fatalities and other health effects may be predicted .to occur as a result of long-term habitatin of relatively low-level contaminated areas. I~ncreased efforts, and costs, of decontamination would result in a reduction of such ;
latent cancer fatalities. Such a cost vs. health-effects trade-off has been ; discussed in References 2, 7 and 24. These aspects of post-accident countermeasures ' are not discussed within this report, however, because the societal decisions required and the costs they impose vary from case to case and cannot be readily planned prior to an actual release, and because the relatively low level of contamination at greater distances would generally ease any urgency requirements and so permit sufficient time for such decisions to be made on an ad hoc basi .2.2 Early Fatality The individual risk of early fatality vs. distance, given SST1 and SST2 releases, is shown in Figures 3.2-1 and 3.2-2, respectively". The risk of early fatality from an SST3 release is zero for all distances, since the doses are not sufficient to produce this effect.
M * Notes: l p! 1) Data taken from Ref. 7 and replotted on linear scale. These effects apply j
- to the averace individual at this distance, rather than the maximally
!j exposed individual, whoe risk would be about one order of magnitude greate i n 2) The "No Evacuation" plot assumes that no protective measures are take '
3) All " Evacuation" scenarios assume that this protective measure extends to 10 mile . h 11 t S l _- -.
. . _ _ . _ .
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'
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Figure 3.2-1 Individual Probability of Early Fatality vs. Distance Given an SST1 Release ____ -- _ _ _ - _ - - - _ _ - _ _ - _ - _ _
. .-
_ ____ _ _ . . . - . . - . - - - - - . . - ~ - -
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, I I I O 1 2 3 4 5 DISTANCE, MILES Figure 3.2-2 Individual Probability of Early Fatality vs. Distance Given an SST2 Release
. . _ . . .. .. . . . . . . . . - . . . . -- -- = - - - --- --~~-
, _ ._ . _ _ . . _ . _ - _ . - - -
.
- - - - - -
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p.... -- - - - - . --- - -
*
i *
.
1? tt *, l[ Figure 3.2-1 displays the risk of early fatality for four differing protective actions given an SST1 release. It is clear that the risk of early fatality is
- strongly dependent upon distance, the protective action taken, and the time
.; evacuation is initiate Even where no protective action is taken ("no evacua-
'; tion" case) and an individual is presumed to remain exposed to the plume -
(; during its passage plus 24 hours of exposure from ground contamination, the risk decreases by about a factor of over 100 over the 10 mile EPZ, with most of the decrease in risk in the first few miles. When evacuation to 10 miles !. is included in the calculations, the decrease in acute fatality risk with l' distance becomes even more pronounce Prompt evacuation (1 hour delay i t followed by. evacuation at 10 mph) reduces the probability of early fatalities , by a factor of over 4.5 at 0.5 miles and almost eliminates this risk beyond l
- !
. 1.5 miles even for the SST-1 accident case.
i! - '! Figure 3.2-1 also provides valuable insight on the degree of urgency with i! *which protective actions need to be taken at various distance Because of i increased dispersion as well as travel time, protective actions at shorter
. distances must be implemented more swiftly to significantly reduce risks. For 1 example, to assure an indivdual risk of early fatality of no greater than 0.005, given an SST1 release, an individual at a distance of 1 mile from the reactor needs to evacuate with a delay time of 1 hour, whereas individuals at distances.of 2.5 miles and 4 miles can delay evacuation for 3 hours and 5
- - hours, respectively, with the same degree of risk.
! Figure 3.2-2 shows the risk of early fatality vs. distance for an SST2 release with no protective actions taken. Clearly, the risk is much lower for an-SST2 !; release and becomes very small beyond about 1 mile.
'i .
- It is also important to recognize that the risk of early fatality can extend beyond 10. miles, in unusual circumstances. Table 3.2 shows that, when no protective actions are taken, early fatalities could occur beyond 8 miles .in about 10% of SST1 releases and could occur beyond 12 miles in about 1% of such releases. Realistically, these percentages would be much lower since it is highly unlikely that no protective actions would be taken, even beyond the j' plume exposure EPZ, given a severe release at a nuclear power plant in the -
.
,
i, .2.3 Early Injury i Ear'y injuries, which would be manifested by symptoms such as nausea and loss
:
of appetite, are generally presumed to commence at whole body doses of above about 50 res.** The individual risk of early injury as a function of dis-
.l tance, given an SST1 release, is shown in Figure 3.2-3*. Although the risk , for this effect varies both with distance and the protective action taken, . reduction with distance *is not as abrupt as for early fatality in Figure 1 3.2-1. For example, for the no evacuation scenario, the reduction in indivi- ; dual early injury risk between 0.5 miles and 2 miles is about a factor of ; For early fatality it is about a factor of When protective actions are ! included, the reduction in risk of early injuries is greater, dropping by a j factor of-16 between 0.5 and 2 miles. As in the case of early fatality, at It -
I[ * Note: Data taken from Ref. 7 and replotted on linear scal ** Note: For a fuller discussion of health effects, the reader is referred to
,_
i! References 2, 13, 22 and 23.
i' j, ,
iF , !, . i i
*
. .. . . _ . .. . .. -- . . - . . . -.-- . .-. . _---
-
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,y.,_, m ._p ,_,,_.,_m.,,,-g ._.y,-- .,,,,..g.,__,,.,._ _ ,
, . . . . . . . . +.- - - - . . - . . .....:.. :: .. .. . . - -
-
.. p
. O i
,
.-
.-
Table 3.2 Sensitivity of Fatal and Injury Distances to Release Magnitude ;; ; q
;t ASSUMPTIONS: NEW YORK CITY METEOROLOGY, 3412 MW(t) PWR, AND NO EMERGENCY RESPONSE ,
.
,.
.t' * SOURCE: NUREG/CR-2239, NOV. 1982
,
I C
' FATAL DISTANCE (MI) INJURY DISTANCE (MI) I
,
ACCIDENT RELEASE * HEAN 90% 99% MEAN 90% 99% l ., i'
, SSTI .0 12 11 20 35 l
.
., 1/2 SST1 .0 10 l
:!' .
l
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1/10 SST1 .0 .8 /20 SST1 . 2 .9 .0 ! 1/100 SST1 -0 <1 .9 2. 0 - f.
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;; Figure 3.2-3 Individual Probability of Early Injury vs. Distance Given j '
an SSTI Release i I
;
. . -. -- . _ . .. --. -- . . . - . . . - . . . - . .. . .. - .- . . - ... - - -
j- .,- =! . l'. '1 distances less than 2 miles the only protective action strategy that would be
.
highly effective in reducing the risk of early injury is early evacuatio \ ll - The individual risk of early injury without protective action, given an SST2 1 !j release is shown in Figure 3.2-4*. The risk reduction with distance is seen ! j to be very large and occurs primarily within about the first 2 miles. Risk l ,, decreases from a value of about 10 2 at a distance of 1 mile, given an SST2 i ij release, to a value of 10 8 at 2 miles, and to about a value of 10 4 at mile l ![
- t
.
ji 3.2.4 Latent Cancer Fatality j The individual risk of latent cancer fatality as a function of distance was also examined7 . It was determined that the SST1 release dominates the risk of latent cancer fatality being about one order of ragnitude greater than that for an SST2. release. The reduction in individual risk between 0.5 miles to 10
' miles was about a factor of 20, given an SST1 release. From 0.5 to 2 miles ,
the risk reduct' ion was about a factor of two. Since the studies were only for
'
the case of an evacuation with an average delay time of about three hours, the
.
effect of different protective action strategies was not clear. Unlike the ~ risk of early fatality or early injury, there is no sharp dropoff in risk of latent cancer beyond some distance, but the risk drops off monotonically and smoothly with distanc It is clear, however, that although monitonically decreasing with distance, individual latent cancer fatality risk extends out to large distance Section 3.3 Variation in Accident Consecuence Timinc vs. Distance
3.3.1 Introduction
., This section discusses the relationsh,fp of the time of release of radio-ll activity following an accident in a reactor and time-dose-distance relation-
: ships after this release has occurred. Discussions combined with graphic presentation allows conclusions to be drawn about how these factors affect variation of potential accident consequences and emergency planning, jj 3.3.2 Time of Release of Severe Accident Sequences N The time from accident sequence initiation to a release f radioactivity is i{ important because it provides insight into the degree of urgency with which
, protective actions, such as evacuation or sheltering, need to be initiated to provide an effective response.
lt A major study since the Reactor Safety Study (WASH-1400)2 which has investi-
! gated potential severe accident sequences, including their timing, is the ni Reactor Safety Study Methodology Appifcations Program (RSSMAP).s This study,
!j using the methodology employed by the Reactor Safety Study, examined risk dominant accident sequences for four specific light-water reactor (LWR)
- plants. These plants were Sequoyah Unit 1, a pressurized water reactor (PWR)
ji with an ice condenser containment and emmploying a Westinghouse-designed
{ nuclear steam supply system (NSSS); Oconee Unit 3, a PWR employing a Babcock d
! and Wilcox NSSS in a large dry containment; Calvert Cliffs Unit 2, a PWR with
'i I
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. I i 0 1 2 3 4, 5 i' DISTANCE, MILES
. Figure 3.2-4 Individual Probability of Early Injury vs. . Distance Given 1
'
an SST2 Release xt 18-
'
l
.
.
, . web . -n.- %-
-- - - - - - - -
__ _ . - --______ _____ _ _ - . . . - - - - _
~* .
' s, a Conbustion Engineering NSSS in a large dry containment; and Grand Gulf Unit 1, enploying a General Electric designed boiling water reactor (BWR) NSSS and l a GE Mark III pressure-suppression containment. The RSSMAP study analyzed the probabilit of occurrence of key core-melt sequences and also made use of the ! MARCH'and CORRAL codes, developed from the Reactor Safety Study, to examine the timing of these sequences as well as the magnitude and type of radioactive fission products released. The results of the RSSMAP study have been pub-lished in four volumes as NUREG/CR-1659s from February 1981 to May 198 Results on the timing of severe releases for each of the four plants are shown l in the accompanying tables (3.3-1, 3.3-2, 3.3-3, 3.3-4). The tables list for each plant the probability of core-melt sequences which would lead to a severe radioactivity release (taken as equivalent to an SST1 release, using the nomenclature of NUREG/CR-22397, or a PWR 1, 2, 3 or a BWR 1 or 2 release, using the terminology of WASH-1400)2 Each. table also lists the dominant accident sequences for each plant as estimated by reference 7, the estimated annual probability of occurrence for.each sequence, the time after the l sequer.cn commences when the release-would begin, and the relatve contribution of each sequence to the total probability of a severe releas From these tables, it can be seen that the time when release begins can range l from values significantly less than one hour to times on the order of one day l with a large fraction of the sequences estimated to have release delay times l of about two to three hours. Also of iterest is the fraction of sequences for whicn the time of release is less than two hours after accident initiatio Thes'e sequences are considered to be fast-developing. The fast-developing , sequences were estimated to constitute about 3 percent of the total sequences I a for the Calvert Cliffs plant and range to a high of-about 30 percent for the l Oconee plant, with the two other plants having values of about.15 percen l
\
Conclusions
. Estimates of the release delay time for severe accident sequences ranges from values significantly less than one hour to times on the order of one !
day, with two to three hours considered to be typica l
.
Estimates of the probability of a severe sequence being a fast-developing one, that is, where the release delay time is less than two hours, ranges from 3 percent to 30 percent, with about 15 percent considered to be typica F 3.3.3 Time-Dose-Distance Relationships In addition to the time when a release of c severe accident sequence begins, discussed in the previous section, one must also assess the rate at which an individual would accumulate a given radiation dose after a release commences, assuming a fixed location and release characteristics; in other words, the time required to receive a specified dose at a given distance. This type of " information is often displayed in a curve or a set of curves known as a , time-dose-distance relationship since it shows time plotted along the ordinate l vs. the observer's distance along the absicissa, with values of constant dose
: as a parameter. This information was not available from the published litera-ture for core-melt releases, and was therefore specifically developed for this stud I
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*' .. * Table 3.3-1 TIMING OF SEVERE RELEASES FOR OCONEE ;_ .
PROBABILITY OF POSTULATED CORE-MELT SEQUENCES GIVING RISE TO SST1 RELEASES
'
' i I
' CONDITIONAL ,.]
_ , . , SEVERE
'
t . EVENT' TIME OF RELEASE RELEASE SEQUENCE PCB/YR (MIN.) PROBABILITY TMKU y 3.9 x 1 a 60 mi .11 V 4.0 x 1 mi .11 i i 50 y '2.4 x 10 s 79 mi ' O.066 TM00 y 7.5 x 10 7 79 mi .020 . ' TMLU y 2.7 x 10 s 202. si .074 TMQ-H y 5.5 x 10 s
-
3 202 mi .15 . TMW-FH y 2.5 x 1 > 202 mi .069 l "
. SH y 5.0 x 10 8 'i
> 202 mi .137 . I SFH y 2.1 x 1 > 202 min.' O.058 i TMLUD y 7.4 x 1 > 202 mi .20
- , y 3.6 x 10.s/g.YR**
'
,. SOURCE: NUREG/CR-1659 Table 3.3-2 TIMING OF SEVERE RELEASES FOR CALVERT CLIFFS
, PROBABILITY OF POSTULATED CORE-MELT SEQUENCES GIVING RISE TO SST1 RELEASES
'
,f CONDITIONAL
/ *
SEVERE EVENT TIME OF RELEASE RELEASE SEQUENCE PROB /YR (MIN.) PROBABILITY
'
TKML y, 6 4.2 x 1 k 60 mi .028 2. 0 x 1 , TMQ-0 6, y 120 mi .014
,
TMQ-H y, 6 2.3 x 1 mi .016 8. 4 x 10 5
'
TMQ-FH y6 120 mi .057
, . TML y, 6 1.21 x 10 3 149 min. - 0.82 ' TMLOO1 6 1. 0 x 10 4 319 mi .068 1. 5 x 10 8/R/YR**
SOURCE: NUREG/CR-1659
, " Probability of SST-1 release given accident sequenc l ., ** Summation assumes sequences are independent. 3.6 x 10 s/g.YR = 3.6 events p- per 100,000 reactor years.
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Table 3.3-3 TIMING OF SEVERE RELEASES FOR GRAND GULF ]' i PROBASILITY OF POSTULATED CORE-MELT SEQUENCES GIVING RISE TO SST1 RELEASES CONDITIONAL t- SEVERE
'
EVENT TIME OF RELEASE RELEASE l SEQUENCE PROS /YR (MIN.) PROBA8ILITY*
; TC-6 5.4 x 1 mi .16 TPQI-6 5.3 x 10 8 1190 mi .16 : TQW-6 1.8 x 10 s 1340 mi .54 i SI-6 4.6 x 1 * 1400 mi .14
' 3.3 x 10.s/g.YR**
:l SOURCE: NUREG/CR-1659 , :l d Table 3.3-4 TIMING OF SEVERE RELEASES FOR SEQUOYAH l
l PROSABILITY OF POSTULATED CORE-MELT SEQUENCES GIVING RISE TO SST1 RELEASES
,! ! CONDITIONAL i SEVERE j EVENT TIME OF RELEASE RELEASE l,
SEQUENCE PROS /YR (MIN.) PROBABILITY" i l V 5 x 10 s 38 mi .14 j l 52 H-6 2 x 1 mi .55 1 52HF-6 5 x 1 mi .14 1 52 HF-6, 6 3 x 10 s 219 mi .085 i
, TML-6 3 x 10 s 238 mi .085 l . I 3.6 x 10.s/R-YR** l i
SOURCE: NUREG/CR-1659
.] * Probability of SST-1 relsade given accident sequenc .} ** Summation assumes sequences independent. 3.6 x 10.s/R-YR = 3.6 events per 100,000 year :.
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q Sandia National Laboratories was requested to perform an analysis to determine the cumulative whole-body dose vs. distance with the time from the beginning
-
of the release shown as a parameter. This information was generated for each of three core-melt releases, namely, SST1, SST2 and SST3, and for two constant . weather conditions for each release: 1) a Pasquill "0" stability with a 10 mph windspeed, 'which corresponds approximately to a 50 percentile or " average" atmospheric dispersion condition; and 2) a Pasquill "F" stability with a 5 mph windspeed, which corresponds to about the worst to be 10 to 15 percent in terms ' of atmospheric dispersion. . Parametric curves of dose vs. distance were developed for times after release of 0.5, 10., 1.5, 2, 3, 5 and 10 hour i The data were cross plotted to show time from the beginning of the release v distance with dose as a parameter. These curves, the time-dose-distance relationships, are presented in Figures 3.3-1 through 3.3-5. Only one curve is shown for tha SST3 release, since the reach of this release, in terms of distance, does not extend beyond about 2 miles, even for the lower level whole
;
body PAG (1 rem) and for adverse meteorolog ; An examination of the time-dose-distance relationships shown in Figures 3.3-1 to 3.3-5 indicate that, for a given dose, each of the curves displays a similar general characteristic in that the time to accumulate that dose increases mono- , tonica11y with distance, with the slope of the curve also increasing with dis- l tance. At some particular distar.:e the slope of the curve becomes essentially vertical. The significance of that distance is that, beyond it, it becomes virtually impossible to receive a dose in excess of the given amount, since ! ,i essentially an infinite time would be raquired to receive i ; O With these general characteristics in mind, it becomes possible to reach some i 1;
,
conclusions after examination of these figure ' From an examination of Figure 3.3-5, for an SST3 release, it is clear that at distances beyond about 2 miles, times well in excess of 12 hours would be required before an individual would receive a dise in excess of the lower ~l level PAG (1 rem whole body), for the assumed adverse weather condition l
*
From Figures 3.3-3 and 3.3-4, for an SST2 release it can be seen that at i distances beyond about 1 mile, very long accuculation times would be required !
-
before an individual would receive a life-threatening dose (200 rem or more, ,, whole body). At distances of about 2 miles and beyond, an exposure time of ': 2 hours or more from the beginning of the release would be required to produce a dose sufficient to produce early injuries (50 rem or more, whole body).
3 For the most severe core-melt releases (SSTI) Figures 3.3-1 and 3.3-2 show q
'
that poeple within 2 miles.can receive life-threatening doses within short time periods after the beginning of a release (time periods of I hour or 1 less). Consequently, individuals in these locations would be at the greatest degree of risk and urgent protective actions, particularly evacuation, should be commended as early as practicable when a General Emergency is declared to maximize the available time prior to the occurrence of a releas For these most severe core-melt releases, the degree of urgency for people i located from 2 to 5 miles away is somewhat eased. Figures 3.3-1 and 3.3-2
:l show that for average weather conditions, the time required to receive a l
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:i' ' life-threatening dose is from 3 hours to well beyond 12 hours after the
.j beginning of a release; while for adverse weather conditions an exposure time {;i of 1 to 3 hors after the beginning of release would be require M For these same most severe core-melt releases, the degree of urgency for 1 people located from 5 to 10 miles away would be eased even more. For average !! weather conditions, times well beyond one day are required to receive life 3 threatening do'ses; while for adverse weather conditions exposure times ranging from 3 to 10 hours after the beginning of release would be require :
[ 3.3.4 Conclusions q
9 An examination of the time of release for severe accident sequences as well as i the time required for an individual to accumulate a given dose at various U distances leads ~to the following conclusions: a d . The estimated release delay times for severe a'ccident sequences, that is, ' y
'
the time between accident initiation and when the release would commence, ranges from significantly less than one hour to delay times on the order y of one day; 2 to 3 hours are considered typica . The probability of a severe sequence also being a fast-developing one, j that is, where the time of release is less than 2 hours, ranges from 3 j percent to 30 percent; with about 15 parcent cor.isidered to be typica i il . For a majority of core-melt releases (SST3) individuals located beyond P about 2 miles from the reactor would require an exposure time after the beginning of the release of well in excess of 12 hours before receiving a dose that exceeds the lower level PAG value (1 rem whole body). Hence, very eary protective actions beyond about 2 miles do not appear to be warranted for these event . For most cere-melt releases (SST2 and SST3), individuals located at about 2 miles and beyond would require an exposure ;ime after the beginning of release of at least 2 hours before receiving a dose likely to produce .{ {, early injuries (approximately 50 rem whole body).
.
. . For the most severe core-melt releases (SSTI), individuals within 2 miles , can receive life-threatening doses (200 rem or more, whole body) within time periods of 1 hour or less after the beginning of a release. Indivi-j duals in these locations would be at the greatest degree of risk, given ;l this typ J of release, and an early precautionary evacuation * should be d commenced as early as practicable when a general emergency is declared to a maximize the available time prior to the occurrence of a release. Since a
about 1 to 2 percent of all core-melt releases (or about 10 to 20 percent of SST1 releases) are also fast-developing, an evacuation time of up to 2
! hours for people within 2 miles can provide a high degree of assurance l that life-threatening doses would be avoided in the event of even the j most severe core-melt accident e . For these same severe core-melt releases, the degree of risk and, there-fore the urgency for evacuation by individuals located from 2 to 5 miles j away would be somewhat less than for individuals within 2 miles. For
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average weather conditions, the time required to receive a life-threatening dose would be from 3 hours to well beyond 12. hours after the - beginning of a release. Unlikely adverse weather conditions, however, could reduce this time to 1 to 3 hours in a narrow downwind secto . During these releases, the early risk of life-threatening doses for individuals located from 5 to'10 miles away would be much less. For average weather conditions, exposure times well beyond 1 day would be , required; while for adverse weather conditions exposure times ranging i from 3 to 10 hours after the beginning of release would be require . d .
.
.
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"An evacuation before a release would be precautionary since at such a time the release magnitude would not be known. Indeed, a release mic ,t never occur after the precautionary evacuatio .. _ -
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9 4.0 Protective Action Strategies
j 4.1 Selection of a Protective Action Strategy i 2 Based on the preceding discussion of the variation of risk with distance as j well as considerations of release delay time, it is possible to devise a simple, reasonable, protective action strategy that is capable of meeting the
~
j basic radiation protection objectives," given a core melt accident, for the a full spectrum of potential consequences, from the relatively more probable a small-scale accidental releases to the less likely large-scale releases.
] Because of the risk variation and timing considerations noted earlier, a
-
distance of about 2 miles and a time frame of about 2 hours has significance for the implementation of early prompt evacuation, where at all possible, for all core-melt events. Consequently, the authors recommend that the 10-mile y plume exposure EPZ be divided into 2 zones. The first or inner zone would ?! extend from the reactor out to about 2 miles. A design objective or goal l would be to establish the capability for essentially all persons within this
.j area to evacuate it within about 2 hours. The second, outer, zone would be i the remainder of the 10 mile emergency planning zon The size (about 2 miles radius) of the inner prompt action area is to be based primarily upon the following considerations: -
For many core-melt accidents, projected doses would not exceed the Protective Action Guide (PAG)12 levels beyond this distance;
-
For most core-melt accidents, projected doses would be unlikely to result in early injuries beyond this distance;
-
Prompt evacuation by the population within this distance and immediate .J ' sheltering beyond would provide a large reduction in risk to the highest risk group and would also provide additional time to assess the developing H situation further to decide upon and implement required additional protective actions, as necessary, beyond this distanc The design objective to have the capability fcr evacuation by essentially all E persons within the inner prompt action zone within approximately 2 hours is
; based upon the following consideration:::
-
For many core-melt accidents, a response time of about a day or more would be available before projected doses are expected to exceed the j Protective Action Guide (PAG) level For most core-melt accidents, an evacuation within this time would be unlikely to result in doses capable of producing early injurie For the worst core-melt ao:idents, warning times (prior to release) of 2 hours or more are predicted for about 80% to 90% of severe accident sequence Since about 1% to 2% of all core-melt accidents (or 10% to 20% of SST1 releases) , are estimated to result in severe releases that would also be fast-developing
l,
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(warning times less than 2 hours), an evacuation time of 2 hours for' individuals
~
san provide a high, but not absolute, degree of assurance that life-threatening doses would not be received in the event of a core-melt. Realistically,.it-
- would be* expected that the pre-instructed populations living close to a reactor could and would evacuate the 1.5 mile distance from the edge of the exclusion zone to 2 miles in significantly less than 2 hours. This early, prompt, rapid movement should be encouraged by planner .
i This protective action strategy and its rationale are illustrated in detail in the accompanying Table .
, The uncomplicated, understandable, recommendations to be public' that result from this strategy and rationale can be summarized as follows: '
.
SUMARY RECOPMENDATIONS IN THE EVENT OF A PLANT CONDITION WHERE A MOLTEN OR DEGRADED CORE CONDITION IS OBSERVED OR PROJECTED, OR WHERE ADEQUATE CORE COOLING CANNOT BE REASONA8LY ASSURED, OR UPON THE DECLARATION OF GENERAL EMERGENCY: RECOMMEND IMMEDIATE PRECAUTIONARY EVACUATION BY EVERYONE WITHIN ABOUT TWO MILES. THIS EVACUATION TO BE ACCOMPLISHED WITHIN ABOUT TWO HOURS OR LESS WHERE AT ALL FEASIBLE. EVERYONE WITHIN THE REMAINDER OF THE TEN MILE EPZ SHOULD BE ADVISED TO SEEK AVAILA8LE SHELTER AND REMAIN INDOORS UNTIL
FURTHER NOTIC , ACCIDENT ASSESSMENT SHOULD CONTINUE, WITH MONITORING OF BOTH PLANT AND FIELD CONDITIONS. AS THE ASSESSMENT CLARIFIES THE SITUATION, FURTHER ACTIONS SHOULD BE TAKEN, SUCH AS INFORMING THE SHELTERED POPULATION g' PROMPTLY AS TO THE NEED FOR CONTINUING TO SHELTER, OR RECOMMENDING THAT THEY PREPARE TO EVACUAT ,
(NOTES: 1) At the time of an accident, decisionmakers should, of course, take : into consideration actual local conditions that may make evacuation temporarily infeasible (for example, impassable roadways due to severe snowfall or floods)
4 and that might present a greater risk to the general public, if attempted, than potential radiological conditions warrant. Under such conditions authori-ties should encourage sheltering and should also consider the auxiliary benefits of ad hoc respiratory protection (breathing through handkerchiefs, pantyhose, etc.) by those elements of the public potentially affected.
. 2) Since early evacuation within two miles would not be sufficient to avoid , life-threatening doses beyond this distance for the most severe core-melt f releases (those involving prompt failure of containment) under adverse meteoro-i logical dispersal conditions, prompt actions beyond two miles would be necessary 4 in such cases. In such a situation, it is expected that emergency authorities would recommend immediate evacuation, from shelter, of people within about o five miles in a downwind direction even though a release were taking place.
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- TABLE 4.1 REC 0 MENDED PROTECTIVE ACTION STRATEGIES AND RATIONALE ,
h DISTANCE INPACT AND TINING ACTION (S) TO BE PLANNED AND RATIONALE n , 0-2 miles SST3 (70% of core melt accidents) ACTION (S): Prompt evacuation (within 2 hours) ;
*
-
exceed lower level PAG (I rem) upon declaration of a general emergency in a i
*
2-12 hours after release complete 2 mile circl (Expected to be carried l-
.: out for all core-melt events, SST1, 2 or 3.) [t i
] SST2 (20% of core melt accidents) I All persons instructed tn take best shelter a Average dispersion:* available, preferably that provides facilities for ;. [ receiving further instructions, within the complete circle from 2 to 10 alles, F
-i
'
I
'
RATIONALE: For most core-melt events, have about 9 - no life-threatening doses 2 hours from accident initiation to beginning of i .
'
release. Offficult to distinguish between SST1, 2, !'
- injury producing doses 1.5-8 hours
*
or 3 at early stages of event. Want to start people I " after release moving promptly as a precaution prior to release, t This buys time to assess situation at greater [ Poor dispersion:** - distances. Even though this evacuation will j,
, o probably be only precautionary, it should start ;
M - life-threatening doses.2-8 hours as quickly as possible and proceed rapidly in s.
I after release the event the accident develops quickly and an , early release result ;'
- injury producing doses 0.5-2 hours i 1 after release f Nl it ! SST1 (10% of core melt accidents) * Average dispersion taken as Pasquill "0" ;
P stability with 10 mph windspeed (50 percentile -
- Average dispersion:* conditions).
,
- Ilfe-threatening doses 0.5-3 hours ** Poor dispersion taken as Pasquill "F"' stability q after release with 5 mph windspeed (90 percentile conditions). ; ;
;
N - injury producing doses 0.25-1 hour j ] ! after release L k H +
'
a t If L i r i _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - - . - -- __ _ __
- . -. . :. .
-
-- ..- .
;.. p - = : . =. . .. : . . u - -.. .+. ..._.:.,.... ,. u .a.. = ..;, .
- - .
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'l J
..
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[ TABLE 4.1 RECOMENDED PROTECTIVE ACTION STRATEGIES AND RATIONALE (Continued) i DISTANCE INPACT AND TIMING ACTION (S) TO BE PLANNED AND RATIONALE ,l
F Poor dispersion:** h
- life-threatening doses 0.25-1 hour j! after release
- injury producing doses 0.1-0.5 hours ll after release 2-5 alles SST3 (70% of core melt accidents) ACTION (S):
-
.:
;.
- does not exceed lower level PAG Immediate sheltering upon declaraton of general emergenc (Expected to be carried
['
- SST2 (20% of core melt accidents) out. for all core-melt events, SST1, 2, or 3.)
,
" Average dispersion:* II. Evacuation, as necessary, for down- ! wind sectors after assessment of situatio I, !
- no injury producing doses (Expected to be carried out for 30% of core-melt events, SST1 and 2.)
l!
,
i
- ,
w
- exceeds upper level PAG (5 rem)
1-3 hours after release l'
:
;. ;
'
Poor dispersion:** RATIONALE:- Have additional time to assess i situatio ' 4 - no life-threatening doses " For SST3, no additional protective actions .
;
- injury producing doses 2-12 hours neede ,1 after release .
' . '
For SST1 and 2 hayL about I hour,after release,
!
SST1 (10% of core melt accidents) -or 3 hours after accident initiation, before y serious effects experienced. For poor dispersion 9 Average dispersion:* conditions, for rapidly developing accidents or T, actual releases, shorter response time is i y' necessar life-threatening doses 3-12 hours- .l
. ,i ~
after release i f
.
?
'
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.
_ __ - - - .- __--- - . - - _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ - _ _ -
,
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*
.
! i ~
- ,
0 8 TABLE 4.1 RECOMENDED PROTECTIVE ACTION STRATEGIES AND RATIONALE (Continued) )~ DISTANCE INPACT ANG TINING ACTION (S) TO BE PLANNED AND RATIONALE ! l
- injury producing doses 1-3 hours ;,
!!
:
after release {' i
'
Poor dispersion:** f 1 - Ilfe-threatening doses 1-3 hours 1 after release !
,
- injury producing doses 0.5-1.2 hours j t after release >
,
5-10 miles SST3 (70% of core melt accidents) ACTION (S):
,
j' - does not exceed lower level PAG Immediate sheltering upon declaraton of
'
general emergency (expected to be carried i SST2 (20% of core melt accidents) out for all core-melt events, SST1, 2, or 3.)
j [ m Average dispersion:* II. Delayed evacuation, as necessary, for down -
* wind sectors after assessment of situation d - no injury producing doses (expected to be carried out for 10% of core-melt events, SSTI). '
- - exceeds upper level PAG (5 rem)
3-12 hours after release
.
Poor dispersion:** RATIONALE: Have additional time to assess situatio no injury producing doses For SST3 no additional protective action ..; - exceed upper level PAG (5 rem) neede ll 8 1-3 hours after release 9' For SST2, sheltering provides significant dose '
'SST1 (10% of core melt accidents) savings.
- Average dispersion
- " For SST1, have about 3 hours after release, or
- l 5 hours after accident initiation, before serious
.! - no life-threatening doses effects experienced.
!! l
. .
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- -
, :, .m - u ; . y =. ... . . n..,
-
,--- : p .: .. . . . . . . . .
.
..
i
'
' '-
I TA8LE 4.1 REC 009 TENDED PROTECTIVE ACTION STRATEGIES AND RATIONALE (Continued) l
' ;
DISTANCE IMPACT AND TIMING ACTION (S) TO BE PLANNED AND RATIONALE }~ l
# - injury producing doses 3-11 hours For poor dispersion conditions shorter response l
'
-
after release time is necessary
,
!
. Poor dispersion:** !
- i i
- Iffe-threatening doses 3-10 hours
'I after release . 3 injury producing doses 1-3 hours ; after release :
'
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( l
*
l .-. I
- . '
[ 4.2 Probabilities of Consecuences for Various Protective Action Strategies
,
.
' 4.2.1 Introduction
- Previous section's have suggested that a protective action strategy which
- incorporates provisions for early precautionary evacuation within about 2 miles, i with immediate sheltering, ~possibly followed by relocation beyond 2 miles can
) be very effective in consequence mitigation for a spectrum of severe accidents.
l In order to test this as well as other alternatives, the calculated consequences j for these and other response strategies were examined using the CRAC code.s A* i number of calculations were performed to estimate the relative worth of various ! shelter, evacuation and relocation emergency response strategies for a spectrum , of accidental release scenarios. Use of the CRAC code provided a means to
;, investigate the chance or probability of accident consequences conditional on i j the accident and emergency response assumption *
l
'
Three accident source terms (SST1, SST2 and SST3) were used for the calculations.
d Please refer to Section 2.0 for additional discussion of these accident source terms.
a , N 4.2.2 Details of Protective Action Assumptions and Consequence Calculations h b Emergency response assumptions included combinations of evacuation, shelter l- and relocation from shelters after plume (puff) passage. Here, evacuation 1 y means the early movement by people, preferrably before plume exposure. Relo-h cation means later movement from contaminated areas after plume passage.- p' Results for an evacuation speed of two miles per hour (2 mph) are presente * Estimates of consequences for slower speeds would produce results close to or
: coincident with the shelter / relocation results. For early evacuation speeds faster than 10 mph, consequences in the evacuation area would be rare because j evacuees would outrace most releases (wind speeds average 5 to 10 mph), i.e.,
the results are predictable. An' assumed evacuation speed of 10 mph would 1 . produce optimistic results in that the evacuation duration would be very ;
- short, i.e. , only one hour or less for evacuations within the entire 10 mile
!
EPZ. A speed of 2 aph corresponds to an evacuation duration of one hour for i persons within 2 miles and two hours for persons within four miles. Thus, a ! 2 mph evacuation speed analysis provides neither unduly conservative, nor h unduly optimistic overall results, even though actual individual and group , d evacuation speeds would be expected to be much more rapid. Further, results ; y are presented for evacuations which occur commencing at the beginning of a j U release. Results for evacuations commencing much later would again approach l I' the shelter / relocation results. Results for evacuations commencing much , earlier or proceeding more rapidly are also predictable in that the analysis 1 M would much lower doses received by fewer people and few, if any, health effect ) !! A distinction should be noted throughout this report in the discussion of
'
evacuation stategies recomunended by the authors, between the early precaution- 1 lL ary evacuation of the first two miles and the best evacuation strategy to be q followed when an actual severe release is expected or in progress. The first, early, precautionary evacuation should be an automatic, preplanned response to ill the severely degraded plant conditions that would trigger declaration of a l General Emergency. The second, subsequent, strategy that might involve evacu-j l; ation should be followed only after the plant situation has clarified, and as l5 !
!
- .
{t'
,8 * *
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'r - " *" ~
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;
.. . _ _ _ _ . . . . _ , _ _ _ . - _ ___ '
'
.,
, s' a more accure assessment of the potential magnitude of the threat can be mad l j' The first strategy would provide for a major reduction -in individual risks of , severe non-stochastic and stochastic health effects. It also would clear the
'
- , way for the second phase of preplanned but more flexibile protective action 1 decisions by authorities.on the scene that consider actual conditions at the y time.
G Protection factors for cloud gamma, inhalation and ground shine pathways, used . l h for the calculations, are realistic for evacuees in automobiles and somewhat y conservative for people in single wood frame houses without basements. These ' [ are listed in Table 4.2-1. It was recognized that sheltering protection [ , factors would be greater in other types of buildings, but that single wood frame dwellings are abundant and are common in the near vicinity of reacto ,
'
H sites. Thus, the calculations pertain to near worst case-sheltering. Since i M the protection factors are relatively large (poorer protection), the risk : J estimates made would not be grossly underestimated for persons without shelte ; e l N TA8.LE 4.2-1
, " . PROTECTION FACTORS USED IN 11 THE CALCULATIONS Cloud Ground I, Gamma Inhalation Shine Autos . r! ] Residences .75 0.43
!; M Slightly different protection factors were used for evacuees and persons in ! shelters. Very little or no protection was provided for either group for ' exposures to external gamma rays from the passing plume (puff).. No inhalation protection was provided to early evacuees. An inhalation protection factor of , 0.75 (twenty-five percent dose reduction) was used for shelterees in recognition j! of the fact that air turnover rates in small dwellings average about one per ij hour, which would reduce doses inside the shelter (WASH-1400, App VI).2
.: Conservative protection factors for ground shine (gamma rays emitted by radio- '
i: nuclides deposited on the ground) were used for small vehicles and small ji isolated dwellings with contaminated wa11s.14,1s , 21 l
- It is noted, however, that the potential exists for much better protection l i factors for most people. Future risk studies should include the most realistic j
[, factors available, where they can be justified. Since the purpose here is to ' M investigate the relative worth of various evacuation and sheltering schemes, j; and since timing of protective actions is the most important' parameter, by far, the higher protection factors used should not warp the relative perspec-j tives to a major degree. The most pronounced effect of better protection a factors would be in the reduction of the estimates of early fatalities, because lA of the high threshold of dose required to induce this consequence.
i Relocation from contaminated areas after plume (puff) passage was assumed to u occur after 4 hours within ten miles and after 8 hours outside ten miles, unless noted otherwise. There is no experience on which to base these esti- $ !I 1 ) l 37 \t ! .: ,
' . -
l lt
- _
. -- - . .
l ! l _--..=.=a--;--:. : = :- : --~ ~ -- . == _ , -~= r ~ x
_ _ _ _ - _ _ _ __ _ __ __ .. . - - _ . _ _ _ _ _ _ . _ _ . _-- -
. . - --. - ,
11 4
* . '
z
- "
mate They were chosen as reasonable estimates of the time it would require for environmental monitoring teams to locate areas of " hot spots" and notify
. people to leave. Identification of areas in which ground level dose rates
exceed, say,1 R/hr (i.e. , " hot spots") would be a simple matter. Although these highly contaminated areas could be long, they should be narrow1 *'17, !i such that relocation times would be short and the dose accumulated while
- l relocating would be a small fraction of the total dose. The conservative l'
shielding factors used for the calculations (see.above) account, in part, for
~
l} the small dose that would be accumulated while outside, relocating. This
- } method of accounting for outside exposures during relocation was necessary
- because the CRAC code does not provide a separate calculation of the dose while relocating. Further,thewaythecodeisstructured,all,personsoutside
!j! the 10 mile EPZ were relocated after eight hours, whereas in an actual emergency
- response situation only persons in actual " hot spots" would have to relocate.
'; These code restrictions do not affect the principal c~onclusions of this stud A slightly modified version of the CRAC2 codes was used fc-r the calculations.
- This version provides for three emergency response zones rather than the two
. zones provided in earlier version In this version, evacuation is modeled in 3 the first zone, nearest the release point. The radius of this zone is an d
option of the use In the second and third zones people are assumed to be 'I always exposed to the full plume. In these two zones the user may vary both the time of exposure to ground shine from deposited radioactivity and protec-4 tion factors for cloud (external) gamma, inhalation and ground shine pathway : The washout coefficient for rainfall in CRAC2 was changed from 10 3/sec per 'i mm/hr of rain (for unstable meteorology sequences) to 10 4/sec per mm/hr of
'
rainfall to realistically model measurements of this parameter.28 No other
;l revisions of the CRAC2 code wer,e made for these calculations, j The weather sequences used for these calculations is the New York City National ij Weather Service data set which is available with the CRAC2 code. This selection h was somewhat arbitrary, but it has been used in the recent past for numerous consequence calculations performed for the NRC, which have been widely reporte Thus, there is a tie point for previous consequence calculation It is noted that the average (" expected" in the statistical sense) consequence
'. estimates are dominated by normal daytime and nighttime wind speeds of 5-10 l ! ;, mph, which are the norm across the U.S. Low probability " peak" consequence ); l estimates are associated with rare weather sequences, which may be different !! in different climates and places. Thus, the selection of different weather !! tapes would lead to significantly different estimates of peak consequences, i j both in terms of magnitude and probability. In brief, there is much greater ! ,- confidence in the average result than in the peak of the calculated distri- i d bution of consequences, regardless of which weather tape is used for the l j * estimates.
if l' It is noteworthy, also, in this regard, that the New York City weather tape j' includes rainfall some eight percent of the time. Rainfall has been associ-ated very strongly with peak consequence estimates. Thus, the peak consequence ,
estimates should be on the worst case side of the uncertainty bound.
i! hl il 38 !o! !! !! . l i
'
il
-- . -- -. _
.- - _ - -. .-. ...
. . . - . . -- -. -- - . - .. - - - - - - - - -
'
.
.
'
Section 4.2.3 Results and Discussion ' The results of the calculations have been plotted as whole body and thyroid dose probability distributions for an indiviudal; that is, the probability of an individual receiving a given dose vs. dose, conditional upon the occurrence of an SST1, an SST2 or an SST3 release. The whole body dose distributions for an individual located at various distances between one mile and ten miles from the reactor, given an SST1 release, and assuming sheltering in a one story wood-frame house without a basement and relocating after exposure to the plume
plus 4 hours of ground contamination, are shown in Figure 4.2-1. Whole body i ' dose distributions for an individual assumed to evacuate at an effective speed of 2 miles per hour starting at the time of the release are shown in Figure 4.2-2.
3 For convenience, key valves from these figures are also tabulated in Tables 4.2-2 and 4.2-3, for sheltering and evacuation, respectively.
< Comparison of the dose distributions in these figures indicates that an evacuation ' of persons located within 10 miles, commencing at the time of release and at . an effective speed of 2 miles per hour, results in lower individual doses at all distances, both in terms of mean or expected values, as well as lower values at comparable levels of probability, than sheltering in a one story wood-frame house and relocating after 4 hours. However, it is worth noting
-
that the differences in dose, and more importantly, differences in acute 9 health effects, is greatest close-in to the reactor and diminishes with increasing < distance. At a distance of 1 mile, for example, the dose differences are such that acute fatality would be expected for the sheltering followed by relocation
[ strategy, but early fatalities would not be expected for early evacuation.
F However at distances of about 5 miles and beyond, the dose differences are a such that acute fatality would be highly unlikely for either response. Since o the first priority in a release of this magnitude would be to save lives, it
-
is clear that for individuals located beyond about 5 miles either evacuation j or sheltering followed by relocation within about 4 hours would be about-y equally effective in this regard, even for the most severe releases.
ld For individuals located at closer distances, and especially within about the ? first 2 miles, it is clear that evacuation would be far more beneficial than
,. sheltering. However, it must again be noted that even the evacuation strategy H examined here cannot provide assurance of no acute health' effects. Since the
time-dose-distance relationships discussed in section 3.3.3 showed that the . B dose is accumulated very rapidly (of the order of hundreds of rem per hour) to 0 individuals very close to the reactor for an SST1 release once it begins, it ); is clear that to be effective, an evacuation of close-in individuals should p commence prior to any release, and should be as rapid as practicabl . F The calculated thyroid dose distributions * for an SST1 release, assuming sheltering and relocation after 4 hours exposure to ground contamination are
- .
g . I H *An artifact of the CRAC code significantly influences the thyroid dose calcu- , lations. In esssence, shelterees are exposed to the full plume in CRAC. In reality, exposures to only part of the plume, e.g., the leading edge, would !i be expected for a long duration release. In this sense, the thyroid dose
- estimates are unrealistically high, for early evacuee ; -
,
,
l, 39 !i li-l
' _ _ - _ . _ =, . - , _ . _ - ,. =~ , __ -- ,n~ -- r----------- ,-- . . -
.. - . . . . . . - - - . ---..-----;-. = - - - - ' -: - = - - - - - - - - - - - - ' = ~ - - -
' ~
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, , , -
i i t 10-2 i ie ie : ais, , , , , ,,, . 10 2 3 10 10 10 j l WHOLE BODY DOSE, Rem Figure 4.2-1 h /robability of an Individual at a Given Distance Receiving a Whale Body Dose in Excass of tha Val Shown, Conditional Upoa Occurrence of an SST1 Release and Shelter * Plus 4 Hrs. Groum! Erposure'I
!>
_ - _ _ _ _ _ _ _ _ _ _ _ _ - _ - _ _ _ _ _ _ __ _ __ _ _____-_ _ _ __ _ . _ _
. _ _ _ . _ - . - - - . _ _ . .
_ . _ _ . . _ . . . . . - _ . . _ _ _ - . . - _ _ . .-_ _ _.
l .-
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s l : s u sg i i s 8 s s s3 3-8 i t l . s s u sl
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, Arrows indicate mean values '
i -
,
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i 10-2 s a i aais I a i Isl a a a e a a si 10 2 10 103 * t '
. Figure 4.2-2 WHOLE BODY DOSE Rem l Probability of an Individual at a Given Distance Receiving a Whole Body Dose in Excess of the Value Shown, Conditional Upon Occurrence of an SSTI Release and Evacuation at 2 MPil at Time 0
I
- - _ _ _ - - _ _ _ _ _ _ _ _ _ _ . _ _ _ - _ _ _ - - - _____ _ _ _ _ _ _ _ _ _ - _ _ _ - _ _ - _ _ _ _ _ _ _ _ _ _
__ . _ _ . _ . _ _. . _I . _ . ... $ - h. E-. -._.-[ _ _- . i
- . .
a .. Table 4.2-2 l
.
KEY INDIVIOUAL DOSE DISTRIBUTION VALUES - CONDITIONAL UPON SST1 RELEASE, SHELTERING * AND RELOCATION AFTER 4 HOURS GROUND EXPOSURE I DISTANCE WHOLE 800Y 00SE (REM)
(MILES)
MEAN DOSE 90 PERCENTILE 95 PERCENTILE 99 PERCENTLE 1 55 . 700 1000 1700 3 140, 400 600 1000 5 7 * 7 4 , 10 2 .
* Sheltering in 1 story wood-frame house, without basement I
Table 4.2-3 KEY INDIVIOUAL DOSE DISTRIBUTION VALUES CONDITIONAL UPON SST1 RELEASE AND EVACUATION AT 2 MPH STARTING AT TIME OF RELEASE
'
DISTANCE WHOLE BODY 00SE (REM) l
'
(MILES)
'
MEAN DOSE 90 PERCENTILE 95 PERCENTILE 99 PERCENTLE
*
1 12 . 250 350 500
3 5 . 100 140 200 7 2 . 40 55 90
,
5 < i 42 > l .
. . .
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. . . - . . . ..
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. . . . - . . ~ - . - - . ~ - ~ ~ - - -
~
.
-
0' shown in Figure 4.2-3, while those for evacuation at 2 miles per hour starting at the time of release are'shown in Figure 4.2-4. Again, for convenience, key e I values from these figures are tabulated in Tables 4.2-4 and 4.2-5, for shel-taring and evacuation, respectively. Comparison of the thyroid dose distribu-
! tions reveals once again that evacuation results in the lower thyroid doses, 1 but that differences in acute thyroid effects, such as ablation of the thyroid
.j (highly likely at doses in excess of about 3500 ree) become taall for indi-viduals located beyond about 5 mile * ] In order to ascertain whether a shorter relocation time than 4 hours might prove effective in mitigating acute effects for non-evacuees- at distances less than 5 miles for the most severe releases, a calculation was performed where an individual at 3 miles was assumed to be sheltered and then relocated after being exposed to the plume plus 1 hour of ground contamination. The whole body and thyroid dose distributions are shown in Figures 4.2-5 and 4.2-6, respectively. These results indicate that although both whole body and thyroid , doses are reduced somewhat, they are still higher than the doses where evacuation y t was performed. Since sheltering followed by relocation after only 1 hour of ground exposure is virtually indistinguishable from evacuation, it is concluded that evacuation would be the preferted strategy for individuals located at distances less than 5 miles, in the event of an SST1 releas For an actual SST1 release, consequently, the major objective would be to avoid early fatality. For individuals located from 0 to 5 miles from the reactor, the preferred response would be an early evacuation, which should commence prior to any releas For individuals located from 5 to 10 miles, either evacuation or sheltering followed by relocation within about 4 hours would be about equally effective. Since doses in excess of the PAG 1evels can extend beyond 10 miles, protective actions may be necessary for members of the public at distances beyond 10 miles in the event of a release of this magnitud * i However, as shown by Figure 4.2-1, early evacuation beyond ten miles would not ' be warranted, since sheltering in a 1 story wood-frame house without a basement followed by relocation after 4 hours of ground exposure essentially precludes
- early fatality and makes early injuries unlikely as well.
, We now consider the relatively smaller SST2 releas From Figures 3.2-2 and 3.2-4, it is clear that the risk of early fatality to an individual shows a very rapid decrease with distance, with a value of about 10 4 at a distance of ,~ 1 mile. Similarly, the risk of early injury also shows a rapid falloff with . distance, although it displays a greater reach in terms of distance. Figure 3.2-4 shows that the risk of early injury, given an SST2 release, is very low beyond about 2 miles with a value of about 10 3 at this distance. Based on these L individual risk variations, a prompt evacuation is considered to be the preferred 1 response for individuals located within about 2 miles from the reactor, in the q event of an SST2 release.
Y To examine the impact to individuals beyond 2 miles, calculations were performed p to examine both evacuation and shelter by individuals beyond 2 miles. The i i ' whole body and thryoid dose distributions for an individual located at various ' distances from 1 to 10 miles, given an SST2 release, and assuming shelter in a one story wood-frame house without a basement and relocating after exposure to ; e the plume plus 4 hours of ground contamination, are shown in Figure 4.2-7 and ' 4.2-8. For convenience, key values from these figures are also tabulated in Tables 4.2-6 and 4.2-7, for whole body and thyroid deses, respectively.
lI L 43
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P i L Figure 4.2-3 . THYROID DOSE, Rem i i; Probability of an Individual at a Given Distance Receiving a Thyroid Dose in Exce s of t - Value Shown, Conditional tipon 0ccurrence of an SSTI !!alease and Shelter * Plus 4 Hrs.
, . _ _ _ _ _ - - - _ _- _ _ - _ _ _ - _ _ -
1_ - _ - , .- . c ! i
-
I I I I I IIIg I I I I IIIIl I I I l I I IJI l u I 9 ! - 1 ;
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c
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g -; - n -. nl m ii 4 ; h , m . l . u o 10 7 5 3 2 1 Mile
; I re 10-1 g -
_
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N' i a i e isial a a aaa l a a a a e n s. ' , 10-2 i 2 103 4 a . 10 10 1
-
I Ii THYROID DOSE, Rom o Figure 4.2-4 Probability of an Individual at a Given Distence Receiving a Thyroid Dose in Excess of the Value Shoun, Conditional Upon Occurrence of an SSTI Release and Evacuation at 2 MPH at Tiir.e of Release *
____ _ ___ _ _ . . - _ _ _ _ _ _ - _ - _ _ _ _
- _ _ . - - _ _ _ .- . - . . - . - . . - - - - . . . - . - . - . . - . . ~ - - . . - - -
.
* *
1 ,
- .'
- )
i l '- Table 4.2-4
:
li KEY INDIVIDUAL DOSE DISTRIBUTION VALUES .t > ~! CONDITIONAL UPO.N SSTI RELEASE, SHELTERING * AND RELOCATION AFTER 4 HRS. GROUND ' ~i EXPOSURE
- i '
: DISTANCE THYROID DOSE (REM)
l1 (MILES)
- { . MEAN 90 PERCENTILE 95 PERCENTILE 99 PERCENTILE 2i
- { 1 14,20 ,000 42,000 70,000 3 2 6,00 ,000 23,000 30,000
-
- 3 3,30 ,000 13,000 16,000
- 1 5 1,50 ,100 6,500 10,000 7 88 ,200 3,800 7,000 .
l . 1,300 2,300 4,200 .l <
* Sheltering in 1 story wood-frame hcuse, without basement.
j] Table 4.2-5 !j 1 KEY INDIVIOUAL DOSE DISTRIBUTION VALUES CONDITIONAL UPON SSTI RELEASE AND EVACUATION AT 2 MPH STARTING AT TIME OF RELEASE i! jl DISTANCE THYROIO DOSE (REM) J (MILES) MEAN 90 PERCENTILE 95 PERCENTILE 99 PERCENTILE 1 4,90 ,000 14,000 20,000
- 2 2,80 ,500 10,000 13,000
'
3 1,90 ,600 6,800 9,000 . ' 5 1,00 ,600 4,200 6,500 j 7 66 ,600 2,5C0 4,200 , 10 36 ,400 2,000 ' i l i
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j DOSE, Rem . t Figure 4.2-5 Probability of an Individual at 3 Miles Receiving a ble Body Dose in Excess of the O>; Value Shown. Conditional Upon Occurrence of an SST) Release and Shelter * Plus 1 H Grcund Exposure i
!
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!i Figure 4.2-6 ;' .
Probability of an Individual at 3 Miles Receiving a Thyroid Dose in Excess of the Value i Shown, Conditional Upon Occurrence of an SSTI Release and Shelter * Plus l'Hr. Groumi Exposur ' ! ___ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . - . - _ . - - _ , - . - . - . - - . _ _-- . _ _ _ _ _ _ _
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DOSE Rem
, Figure 4.2-7 Probability of an Individual at' a Given 0[ stance Receiving a Whole Body Dose in Exec 2s of :! the Value Shown, Condition.il Upon Occurrence of an SST2 Release and Shelter * Plus 4 Iks.
!j , Groun.i Exposure 4 i _ _ _ _ _ _ _ - - _ _ .._ _____ - _ _ ______
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j THYROID DOSE, Rem -
' Figure 4.2-8 Probability of an Individual at' a Given Distance P,eceiving a Thyroid Dose in EFCeG of the j; i Value Shcfn, Conditional Upon Occurrence of en SST2 fielease and Shelter * Plus 4 Hr:;. Ground '
l Exposur.:
- __ __ ___ ._ ._ _ __ _
. - - . - . - - - . . - . . - . . - . . . . . . . - . . - - . . . - . . . .. - - - . , . - -. - * . . ' ; +. : Table 4.2-6 KEY INDIVIOUAL DOSE DISTRIBUTION VALUES '
CONDITIONAL UPON SST2 RELEASE, SHELTERING * AND RELOCATION AFTER 4 HOURS-i GROUNO EXPOSU2E 1 .
OISTANCE THYROID DOSE (REM) i
! * (MILES) ;
MEAN 90 PERCENTILE 95 PERCENTILE 99 PERCENTILE i t ,j 1 ji 2 1 3 1 . 45, 70.
- 5 . 24, 32.
? 7 . 1 . ,
-{ 10 .5 1 .
,
y * Sheltering in 1 story wood-frame house, without basemen ::
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*
EXPOSURE I-j DISTANCE THYROIO DOSE (REM)
' (MILES)
M 90 PERCENTILE 95 PERCENTILE 99 PERCENTILE 1.
.i 2 . -j 3 5 . 190 280
-
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Comparison of dose distributions indicate that an evacuation '(figures not shown), commencing at the time of release and at an effective speed of 2 miles per hour, results in lower individual doses at all distances, than sheltering
. '
in a one~ story wood-frame house and relocating after 4 hours. However, the differences in dose between these two strategies are such that acute health effects such as early injuries are unlikely for either strategy for the SST2 release. Both strategies result in individuals receiving doses above the PAG 1evels but below the level where any early injuries would be expected. However, p sensitive elements of the population (e.g. , the fetus) might be affected by i doses at these levels. Hence, while early evacuation beyond 2 miles for an
. SST2 release may provide no reduction in acute health risks for the general population, there could be such benefits for special elements of the populatio !
j It was also decided to evaluate the consequences of a delay in relocation, i given an SST2 releas Consequently, the dose distributions were obtained for j individuals beyonrf 2 miles who, given an SST2 release, were in shelters and j then relocated aftar' 8 hours and 12 h6urs of ground exposure as well. The whole body and thyroid dose distributions for sheltering with relocation after
, 8 hours of ground exposure, are shown in Figures 4.2-9 and 4.2-10, respec-
j tively. The corresponding dose distributions for relocation after 12 hours j are shown in Figure 4.2-11 and Figure 4.2-12. From these curves it can be
- i seen that there is a relatively small penalty, in terms of dose increase, if q relocation is not accomplished within 4 hours. For example, for an individual T located at 3 miles the mean or expected whole body dose is increased from 11 rem to 13 rem if relocation is delayed from 4 to 8 hours, and increased to i 15 rem for relocation after 12 hours. Similar percentage increases are noted
- at the other distances, as wel *
' ,t To summarize for an SST2 release, the major objective of emergency response ;
would be to avoid early fatalities and early injuries. For individuals located '! within 2 miles from the reactor, the preferred response would be a prompt
.. evacuation, which should commence prior to any release. For individuals 1 located from 2 to 10 miles, either evacuation or sheltering followed by relocation j within about 4 hours would be about equally effective. However, there would
be a relatively small increase in dose, of no significance for early health
- ! effects, if relocation were to be delayed up to 12 hours. For sensitive elements of the population (for example, pregnant women), evacuation out to '
about 5 miles may be advisable, however. Since doses would not be expected to l exceed the upper PAG 1evels beyond 10 miles, evacuation for members of the l 'i public beyond this distance would not be expected to be warranted for a release j
'
of this magnitud l ~: Finally, the SST3 release was also examined. From Figure 3.1-3, it is clear J that the doses would not be expected to exceed the PAG " levels at distances .' beyond about 2 miles, for this release. To evaluate this, the whole body and
:
i thyroid dose distributions for individuals located beyond 2 miles, were calcu-
! lated assuming sheltering in a one story wood-frame house without a basement .j and relocating after exposure to the plume plus 12 hours of ground contami-
- a nation. The results are shown in Figures 4.2-13 and 4.2-14. From these
!j curves it is clear that the doses are well below the PAG values for this
response strategy.
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, Ground Exposure
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's Ground Exposure
.- _ _ - _ _ - _ _ _ - - _ - _ - - _ _ - _ _ - -
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- . , . . . . . . . ... . . ., ..a - -
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. THYROID DOSE, Rem i Figure 4.2-12 Probability of an Individual at a Given Distance Receiving a Thyroid Dose in Excess of the i Value Shown, Conditional Upon Occurrence of an SST2 Release and Shelter * Plus 12 !!r Ground Exposure
' l __ _ _ _ _ _ _ - - _ - _ _ _ - - - - _ _ _ _ _ _ _ - --_ - .
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'! DOSE, Rem -
ii Figure 4.2-13 Probability of an Individual at a Given Distance Receiving a Whole Body Dose in Excess of
'!i the Value Shown, Conditional Upon Occurrence of an SST3 Release and Shelter * Plus 12 f!r Ground Exposure . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ - - _ _ - _ _ _ _ - _ _ _ ___
:a - ;-. .:.2u.- --
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.
t
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10 2 , e i i iieil i , , , e i. i l , , , ,,,, 10 2 10-1 a 3, THYROID DOSE, Ram Figure 4.2-14 Probability of an Individual at a Given Distance Receiving a Thyroid Dose in Excess of the Value Shoun, Conditional Upon Occurrence of an SST3 Release and Shelter * Plus 1,2 li Ground Fxnnsure
- - __ _ _ _ - - __ - - - _ -
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5.0 REFERENCES , . U.S. NRC and U.S. EPA, " Planning Basis for the Development of State and ' Local Government Radiological Emergency Response Plans *in Support of Light Water Nuclear Power Plants," NUREG-0396 and EPA 520/1-78-016. Nuclear Regulatory Commission, December 197 . U.S. Nuclear Regulatory Commission, " Reactor Safety Study, An Assessment if Accident Risks in U.S. Commerc:a1 Nuclear Power Plants," WASH-1400, r NUREG-75/014, October 197 * Code of Federal Regulations, Part 50 " Domestic Licensing of Production and Utilization Facilities," January 1,1984.
' U.S. Nuclear Regulatory Commission, " Criteria for Preparation and Evaluation of Radiological Emergency Respohse Plans and Preparedness in Support of Nuclear Power Plants," NUREG-0654 (FEMA-REP-1), January 1980.
' R. M. Blond, M. Taylor, T. Margulies, M. Cunningham, P. Baranowsky, . Denning, and P. Cybulskis, "The Development of Severe Reactor Accident Source Terms: 1957-1981," U.S. Nuclear Regulatory Commission, NUREG-0773, November 198 . NUREG/CR-1659, " Reactor Safety Study Methodology Application Program," Parts 1-4, Jan. 1982. (RSSMAP)
, D. C. Aldrich, et al., " Technical Guidance for Siting Criteria Development,"
NUREG/CR-2239, U.S. Nuclear Regulatory Commission, December 198 ' " Calculations of Reactor Accident Consequences Version 2 CRAC2 Computer
-
Code. Users Guide." Ritchie, L. T. ; Johnson, J.D. ; Blond, Sandia Laboratories, NUREG/CR-2326, April 198 ! "In-Plant Considerations for Optimal Offsite Response to Reactor Accidents," Burke, R. P.; Heising, C. D. Massachusetts I'nstitute of Technology, Cambridge, MA. Aldrich, D. C. .Sandia Laboratories, NUREG/CR-2925, March, 1983.
, 1 " Final Environmental Statement related to the' operation of Limerick Generating Station, Units 1 and 2, Docket Nos. 50-352 and 50-353," U.S. Nuclear Regulatory Commission, NUREG-0974, April 198 . "U.S. Nuclear Regulatory Commission 1984 Policy and Planning Guidance," NUREG-0885, Issue . U.S. Environmental Protection Agency, " Manual of Protective Action Guides
, and Protective Actions for Nuclear Incidents," EPA-520/1-75-001 , (September 1975), Revised June 198 j 1 I. 8. Wall, P. E. McGrath, S. S. Yaniv, H. W. Church, R. M. Blond, J. Wayland. " Overview of the Reactor Safety Study Consecuence Model," . Nuclear Regulatory Commission, NUREG-0340, Cetober 197 i
, 59 l : ! . l' . . _ . . . . . . . . . _ _ . . . . . . _ . . . _ _ . . . . . . . . . . _ _ . . . _ _ ._
. ._ .. . . _ _ _ ._ . ~ _ . _ . _ .. -
-- . .. _
O . ", o * 1 B. Laurisden and P. H. Jensen, " Shielding Factors for Vehicles to Gamma Radiations from Activity Deposited on Structures and Ground Surfaces."
lgg Health Physics, v. 45, m. 6, Dec. 198 . Z. G. Burson and A. E. Profio, " Structure Shielding in Reactor Accidents," Health Physics, v. 33, n. 4, September 197 . T. S. Marjulies and J. A. Martin, Jr. " Dose Calculations for Severe LWR Accident Scenarios." NUREG-106 ' May 198 . J. A. Martin, Jr. Dose While Traveling Under Well Established Plume Health Physics, v. 32, April 197 . Protection of the Public in the Event of Major Reactor Accidents: Principals for planning. ICRP/84/C4-5/2, Adopted by the Main Committee in May 198 . 1 "The Calculation of Wet Deposition for Radioactive Plumes," H.O. Brenk and K. J. Vogt, Nuclear Safety, Vol. 22, No. 3, May-June 1981 2 " Nuclear Power in an Age of Uncertainty" (Washington, D.C.: U.S. Congress, Office of Technology Assessment, OTA-E-216, February 1984).
2 " Basis for Selection of Emergency Planning Zones for the Shoreham Nuclear Power Plant, Suffolk County, New York," F.C. Finlayson, E. P. Radfor . 2 "In Utero Exposure to A-Bomb Radiation and Mental Retardation; A Reassessment." Masanori Otake, William J. Schull, The British Journal of Radiology. 57.409-414, 192 . 2 "The Effects on Populations of Expo'sure to Low Levels of Ionizing Radiation:1980" (BEIR III), National Academy of Sciences,198 . " Objectives of Emergency Response and the Potential Benefits of
'
Evacuation and Shelter," James A. Martin, Jr. , Proceedings of Topical Symposium of the Health Physics Society, January,198 .
-i -
. . . . . . . . . . - - - --- --- ,__ _ __ _ _ . _ _ . . _ _ _ _ _ . _ _ - . - _ _ -
r- _ . _ _ _ ... . . ..m . QUESTION At the NUREG-1150 briefing the staff indicated that Brookhaven National Laboratory is generating dose-distance curves for a variety of assumptions in emergency preparednes Please provide a enpy-of the contract (s) under which Brookhaven is conducting these studie Who are the principal investigators at Brookhaven on this project?. Please provide all documents, includino but not limited to working papers, interim reports, and other written materials, that the Commission has received from Brookhaven with regard to this wor ANSWE Enclosed is a copy of the NRC Form 189, Profect and Budget Proposal for NRC Nork for the Protective Action Decisionmaking orogram at Brookhaven National Laboratorv (RNL) which is responsible for generating some of the dose-distance curves which will be in NU1EG-115 Trevor Pratt is the BNL Principal Investigator. As of .be present BNL's only output relevant to NUREG-1150 are dose-dist.arce curves in the repor The reoort will be sent to you when publishe l
; ._ - _ r.r _ . _ ._ - . _. . _ _ . , _ _ . . , _ _ , . _ . . . . _ . . ___ . ~ _ _ _ _ _ _ . . _ _ _ _ _ _ _ _ . .
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