ML19257B491
| ML19257B491 | |
| Person / Time | |
|---|---|
| Issue date: | 10/31/1979 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| SECY-79-594, NUDOCS 8001160418 | |
| Download: ML19257B491 (16) | |
Text
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UNITED STATES October 31, 1979 NUCLEAR REGULATORY COMMISSION SECY-79-594 WASHINGTON, D. C. 20555 The ComINFORMATION REPORT FOR:
FROM:
Harold R. Denton, Director Office of Nuclear Reactor Regulation THRU:
Executive Director for Operations
SUBJECT:
CLASS 9 ACCIDENT CONSIDERATIONS PURPOSE:
To inform the Comission of staff activities relating to consideration of Class 9 accidents in NEPA and Safety Reviews.
BACKGROUND:
By memorandum dated September 14, 1979 from Samuel J. Chilk, Secretary, to Lee V. Gossick, Executive Of rector for Operations, subject "SECY-78-137-Assessments of Relative Differences in Class 9 Accident Risks In Evaluations of Alternatives to Sites With High Population Densities,"
the staff was requested to discuss with the Comissioners:
(1) how it intends to define Class 9 and design basis accidents, (2) how these accidents will be included in reviews (and possibly re-reviews for existing plants),
and (3) how siting should be revised in light of Three Mile Island.
This paper is the initial response and outline of approach of the staff to this request.
It has also been structured as a response to the related requests to the staff by the Comissioners which is contained in their Memorandum and Order dated September 14, 1979, "In the Matter of Offshore Power Systems." There the staff was requested (a) to provide recomendations on how the procosed Annex to Appendix 0,10 CFR Part 50, might be modified, on an interim basis, to reflect developments since its publication in 1971 and to accord more fully with current staff policy in this area, until rulemaking on the subject of the proposed Annex is completed, and (b) also in the interim to bring to the Ccmmission's attention, any individual cases in which the staff believes the environmental consequences of Class 9 accidents should be considered.
SCOPE:
To be fully responsive to these requests the staff concluded that its acproacn to these questions should encompass Comissicn responsibilities under both :ne Atomic Energy Act (i.e., protection of the public health and safety) and the National Environmental Policy Act (NEPA). A brief su:r: nary of staff practices and devel-opments in dealing with accident considerations in
Contact:
1753 095 s.
aayne Houston, NRR
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8001160 DISCUSSION:
safety reviews as reported in staff Safety Evaluation (continued)
Reports and in environmental reviews as reported in Staff Environmental Impact Statements is given in Enclosure 1.
The following discussion treats in succession the staff approach to the three questions raised in the September 14th Chilk memorandum.
1.
Classifying and Definino Accidents (a) NEPA Reviews (Environmental Impact Statements)
The proposed Annex to Appendix 0 incorporated a system of classifying postulated accidents for NEPA purposes. As noted therein, "Since it is not practicable to consider all possible accidents, the spectrum of accidents, ranging in severity from trivial to very serious, is divided into classes." The staff now believes that the classification system employed in the proposed Annex should probably be abandoned.
The principal reason for this is that the staff feels that more realistic assessments of accident risks can now be made as a result of developments in quantitative risk assessment techniques and in the light of the Three Mile Island accident.
Therefore, the staff is giving serious con-sideration to the utilization of a continuum representation of the probability of exceeding selected envi'.onmental consequences based upon work which has been carried on by tha Office of Nuclear Regulatory Research, Probabilistic Analysis Staff. This approach would reflect characteristics specific to classes of plants, e.g., BWR's, PWR's, various containments, and site specific population and atmospheric dispersion characteristics.
De range of accident possibilities would include core melt events.
In future Environmental Impact Statements, such a representation of accident risks would be accompanied by a suitable qualitative dis-cussion of a range of possible accidental events as well as the uncertainties associated with the risk computations.
The staff intends to develop for Commission consideration a policy statement as an interim measure reflecting the above approach; such statement to be transmitted to the Commission by January 1,1980. It is anticipated that the policy statement would withdraw the 1971 proposed Annex, and also address the need for continuation of the rulemaking on this matter.
1753 096
3 DISCUSSION:
(b) Safety Reviews and Desion Basis Accident _s, (continued)
As described more fully in part A. of Enclosure 1 many different kinds of events (failures) are postulated for the purpose of safety evaluatians ar.d to assure acceptability of design features.
A traditional methodological approach has been the identification of accident events or scenarios that are then analyzed to establish functional or performance requirements of design features.
[cf.10 CFR Part 50.2(a)] When such events are analyzed on a specific case by case basis they are considered design basis accidents. (DBA).
Composites of such analyses may also be used to establish generic design requirements so that plant specific analyses need not be carried out for every new case. A recent example of this latter approach is found in the report of he NRC/ EPA Emergency Planning Task Force (NUFEG-0396) that led to the generic emergency planning zone (EPZ) concept.
A similar approach, that would specifically include core melt accidents, has been recommended by the Siting Policy Task Force in NUREG-0625 to establish population distribution criteria for site suitability detenninations.
The Lessons Learned Task Force is recomending for all plants several new design features associated with degraded cooling and core melt events.
Implementation of these recomendations through a rulemaking will require consideration of whether or not the desired result can be better achieved by a generic approach or a DBA approach.
2.
Aoplication of Accident Considerations to Plant Reviews and Re-Reviews (a) NEPA Reviews Pending consideration and guidance by the Commission on the proposed policy statement referred to in 1 (a) above, the staff plans to eithnold completion of any unissued Environmental Impact Statements on cases currently under revf-w.
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DISCUSSION:
(b)SafetyReviews (continued)
The staff (Lessons Learned Task Force) expects to recommend rulemaking to establish specific requirements for all plants for design features associated with core melt accidents.
3.
Siting Revi fon In Light Of Three Mile Island As pointed out in the Abstract of the Siting Policy Task Force Report (NUREG-0625), one of the Task Force's goals was "To take into consideration in siting the risk associated with accidents beyond the design basis, Class 9, by establishing population density and distribution criteria."
Thus, if Recommendation 1 of this report were implemented in revised siting criteria regulations, population criteric would act as a surrogate for Class 9 risks.
It is the judgment of the staff that the accident at Three Mile Island has added further emphasis to the importance of siting factors discussed in the Siting Policy Task Force Report, particularly those relating to population matters and to liquid pathway considerations. The staff also believes that additional important insights into this question may come out of the carrent investigations regarding Three Mile Island, viz., the Kemeny Commission and the NRC/TMI Special Investigation Group.
The staff recommends, therefore, that a rulemaking be undertaken, considering the above inputs, to restructure and revise 10 CFR Part 100.
s It is anticipated that this effort would require about two years to complete and would 'nvolve about 10 man-years effort.
In view of the dearth of CP applications at this time, this appears to be a reasonable time interval.
The staff is aware however, that proposed legislation (S.562) might result in a substantially speeded up time table for at least a portion of this e# fort.
DISCUSSION:
Sumary:
(Continued)
The staff is pursuing the following:
Preparation of an interim policy statement on accident risks under NEPA which include consideration of ccre melt events and which would withdraw the 1971 proposed Annex.
Prep. ration of recomendations for design features for all plants associated with core melt a,ccidents.
Preparation of recomendations for rulemaking to revise 10 CFR Part 100, to encompass considerations of the risks associated with core melt events, g7
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' Harold R. Denton, Director
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Office of Nuclear Reactor Regulation
Enclosure:
1.
Accident Considerations in Safety vs Environmental Reviews - Staff Practice and Developments DISTRIBUTION Comissioners Comission Staff Offices Exec Dir for Operations ACRS Secretariat 1753 099
ENCLOSURE 1 ACCIDENT CONSIDERATIONS IN SAFETY VS.
ENVIRONMENTAL REVIEWS - STAFF PRACTICE AND DEVELOPMENTS A.
Accident Considerations in Safety Reviews Since 1955, 10 CFR Part 50 has served as the heart of the Commission's safety regulations governing nuclear power reactor design. From the outset, there has been a recognition of the need to consider the risks associated with possible accidents both in making a determination of the suitability of a givan plant-site combination, as well as in determining the adequacy and effect.iveness of the performance of the various engineered safety features, such as the containment or filter systems, in mitigating the consequences of potential accidents.
The interim statement of policy published by the Commission in the Federal Register on August 21, 1974, in discussing the " defense-in-depth" concept and the role of postulated accidents in safety reviews, said as folicws:
The third level of safety is unique to nuclear power plants. A series of highly unlikely major failures of plant components is postulated as a set of design basis accidents, and safety systems are required to be installed to control all such postulated events.
An example of such a postulated f ailure is the less-of-coolant ac-cident used as a design basis for light water power reactors; emer-gency core cooling systems, whose requirements were recently strength-ened in revised regulations (39 FR 1001, January 4, 1974), and con-tainment are provided to mitigate the consequences of such accidents.
The Comission's regulations in 10 CFR Parts 50, " Licensing of Pro-duction and Utilization Facilities," and 100, " Reactor Site Criteria,"
are complementary elements of this 2hird level of safety.
Part 100 requires in effect, that stationary nuclear power reactors be so designed that no design basis accident will result in calculated offsite doses exceeding specified guideline values. These guide-line values are well below levels at which serious injury or death would be expected to occur.
In the approach to safety reflected in the Commission's regulations, postulated accidents, for purposes of analysis, are divided into two 1753 100
i 2'-
categories - " credible" and " incredible." The former ("c edible")
are considered to be within the category.of design basis accidents.
Protective measures are required and provided for all those postu-lated. accidents falling within that category, and proposed sites are evaluated by taking into account the conservatively calculated consequences of a spectrum of severe postulated accidents.
Those accidents falling within the " incredible". category are considered to be so improbable that no such protective measures are required.,
Although the postulated fission product release assumed for judging site suitability is directed by 10 CFR Part 100 to be of such a magnitude that it "would result in potential hazards not exceeded by those from any accident considered credible," it has become staff practice to treat all postulated accidents in the safety review in a very conservative fashion. That is, the totality of assumptions including the accident severity and the magni-tude of the radioactivity released, the meteorology assumed to occur at the time of the accident, the location of the individual assumed to be ayposed and the performance of other systems available to mitigate the reisase have been such as to provide assurance that the predicted dose to an actual indi-vidual would not be likely to be exceeded by the occurrence of an actual similar event. The results of the staff's reviews, including dose conse-quences from selected postulated accidents, are routinely reported for eacn plant in the staff's Safety Evaluation Report.
Actual staff practice regarding accident considerations in safety reviews is contained today in a large number of the staff's Standard Review Plan sections, and various Regulatory Guides, as well as in Parts 50 and Parts 100 of the Comission's regulations. For further details regarding staff prac-tices in safety reviews, reference is made to SECY 7S-111, " Current Acci-dent Evaluation Practices in Siting and Licensing of Nuclear Power Plants,"
and NUREG-0625, " Report of the Siting Policy Task Force."
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3 9.
Accident Considerations in Environmental Reviews In fulfillment of the requirements of NEPA, and the Comission's regulations given in 10 CFR Part 51, applicants are required to file an Environmental Report with the Comission. The staff, after review of this report, pre-pares an Environmental Impact Statement, first in draft form, and then in final form, after circulation to appropriate public agencies and interested members of the public for coment. A portion of both the applicant's Environmental Report and the staff's assessment concerns the environmental impact of potential accidents.
Guidance on the discussion of accidents in the environmental review, for both applicants and staff, appeared in the proposed Annex to 10 CFR Part 50, Appendix D, which was originally published in the Federal Register on December 1, 1971.
This proposed Annex divided the spectrum of accidents ranging in severity from trivial to very serious into nine categories or classes.
It directed that "for each class, except Classes 1 and 9, the environmental conse-quences shall be evaluated as indicated." Class 1 events were not to be considered because of their trivial consequences, whereas in regard to Class 9 events the proposed Annex stated as follows:
The occurrences in Class.9 involve sequences of postulated suc-cessive failures more severe than those postulated for estab-lishing the design basis for protective systems and engineered safety features. Their consequences could be severe. However, the probability of their occurrence is so small that their environ-mental risk is extremely low. Defense-in-depth (multiple physical barriers), quality assurance for design, manufacture, and operation, continued surveillance and testing, and conservative design are all applied to provide and maintain the required high degree of assur-ance that potential accidents in this class are, and will remain, sufficiently remote in probacility that the environmental risk is 1753 102 f
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4 extremely low. For these reasons, it is not necessary to discuss such events in applicants' Environmental Reports.
For the remaining classes of accidents, the proposed Annex provided sets of assumptions, principally in regard to the radioactive source term and the assumed meteorology, whose objective, as stated in the proposed Annex, was to provide " assumptions as realistic as the state of knowledge permits."
Consequently, the major difference between accident considerations for environmental reviews vs. safety reviews is the emphasis upon a discussion of the impact of accidents "as realistic as the state of knowledge permits" for the environmental review, while the safety reviews has focused upon a conservative evaluation to judge the adequacy of the site and the various plant design features.
It has been staff practice to use the assumptions, as given in the proposed Annex, and to report the consequences of postulated accidents, except Classes 1 and 9 ir. the staff's Environmental Statement.
An example of a portion of a recent staff Environmental Statement discussing the environmental impact of accidents is included as Attachment A.
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5 C.
Recent Develcoments l
A number of developments have occurred since the publishing of the proposed Annex in December 1971 which have had significant bearing on accident consideration for both safety and environmental reviews.
These are briefly discussed.
(1) WASH-1400:
The publishing of the Reactor Safety Study (WASH-1400),
first in draft form in August 1974 and in final form in October 1975 has had a profound effect upon accident considerations with regard to nuclear power reactors. Although this was not the first study that examined consequences of large radioactive releases, it was the first study to examine such events probabilistically and that attempted to arrive at an actual estimate of the probability of a core melt event. Staff practice, in regard to the environmental review, has been to refer to the WASH-1400 study as a generic study made to assess the risks of severe accidents in a more quantitative fashion, but, in keeping with the guidance of the proposed Annex, not to discuss site-specific Class 9 events in the environmental statements.
(2) Risk Assessment Review Grouo:
In July 1977, the NRC organized the above group primarily to clarify the achievements ar.c limitations of the Reactor Safety Study (RSS).
The results of this study, issued in September 1978, to the effect that Review Group was unable to determine whether the overall probability of a core-melt given in the RSS was high or low, have also been included in recent environmental assessments issued by the staff.
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(3) Agency and public Coments The staff's environmental statements have generally received a much wider circulation among other governmental agencMs and the general public than the Safety Evaluation Reports.
A large number of the coments received from other agencies as well as the public have been very negative with regard to the non-consideration of Class 9 accidents in the staff's environmental statements.
These negative coments appear to have arisen as a result of the discussion of such accidents in the Reactor Safety Study coupled with a desire for a full disclosure of the site specific consequences discussed as part of the environmental review as well as a skepticism regarding the supposedly low pnbability of such events.
(4)
SECY-78-137 As a result of considerations arising out of the staff's review of alternative sites in the Perryman case, the staff recomended to the Commission on March 7,1978 that:
(a) Pending completion of the Comissions review of its reactor siting policy, that the staff perform quantitative assessments of the relative differences in Class 9 accident consequences and risks in the review of alternative sites where the population density exceeds the values given in Regulatory Guide 4.7.
1753 105 (b) That the Comission consider the appropriateness of issuing some clarifying statment to the effect that the
-1.
proposed Annex to 10 CFR Part 50 Appendix 0 applies to land-based LWR's of the type licensed during the last decade or-so, and that more detailed consideration of Class 9 accidents may be warranted for other types of sites or designs.
(5) Report of The Siting Policy Task Force (NUREG-0625)
In August 1979, the Siting Policy Task Force recomended that siting policy changes be made "To take into consideration in siting the risk associated with accidents beyond the design basis (Class 9) by estabibhing population density and distribution criteria." The recomendations of this report intended that population criteria would act as a surrogate for Class 9 risks, and that site-specific Class 9 accidents should not be analyzed and weighed in the decisional process.
(6) Commission Policy Statement on the Recommendations of the NRC/ EPA Task Force on Emergency Plannina (NUREG-0396 On October 5,1979, the Comission issued a policy statement concurring in and endorsing the guidance contained in the Task Force Report. The Comission stated that "In endorsing this guidance, the' Commission recognizes that it is appropriate and prudent for emergency planning guidance to take into consideration the principal characteristics (such as nuclides released and distances likely to be involved) of a spectrum of design basis and core melt accidents."
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ATTACHMENT A I
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7.
ENVIRONMENTAL IMPACT OF POSTULATED ACCICENTS p
i 7.1 POSTULATED ACCIDENTS INVOLVING RADI0 ACTIVE MATERIALS A high degree of protection against the occurrence of postulated accidents in the Greene County Nuclear Power Plant is provided through correct design, manufacture, and operation, and the quality assurance program used to establish the necessary high integrity of the reactor system, as will be considered in the Czinission's Safety Evaluation. Deviations that may occur are Notwithstanding handled by protective systems to place and hold the plant in a safe condition.
?
this, the conservative postulate is made that serious accidents might occur, even though tney I
may be extremely unlikely; and engineered safety features are installed to mitigate the conse-j cuences of thcae postulated events that are judged credible.
a The prooability of the occurrence of accidents and the spectrum of their consequences to be considered from an environmental effects standpoint have been analyzed using aest estimates of For site evalu-probabilities and realistic fission product release and transport assumption 3 L
ation in the Comission's safety review, extremely conservative assumptions are used to compare calculated ooses resulting from a hypothetical release of fission products from the fuel with Realistically computed doses that would be received by the 10 CFR Part 100 siting guidelines.
the population and environment from postulated accidents would be significantly less than those to be presented in the Safety Evaluation.
The Comission issued guidance to applicants on September 1,1971, requiring the consideration of a spectrum of accidents with assumptions as realistic as the state of knowledge pemits.
The applicant's response was contained in the Environmental Report.
The applicant's report has been evaluated, using the standard accident assumptions and guidance issued as a procosed amendment to Appendix 0 of 10 CFR Part 50 by the Comission on December 1, Nine classes of postillated accidents and occurrences ranging in severity from trivial to
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1971.
In general, accidents in tne high-potential-very serious were identified by the Comission.consecuence end of the spectrum have a low occu The examples selected by the applicants for consecuence end have a higher occurrence rate.The examples selected are reasonably homogeneous in tems these cases are showr in Table 7.1.
of probability within each class.
Comission estimates of the dose that might be received by an assumed individual standing at the site boundary in the downwind direction, using the assumptions in tne proposed Annex to Estimates of the integrated exposure that mignt be Appendix 0, are presented in Table 7.2.
The delivered to tne population within 50 miles of the site are also presented in Table 7.2.
man-rem estimate was based on the projected population within 50 miles of the site for the year 2020.
To rigorously establish a realistic annual risk, the calculated doses in Table 7.2 would have to be multiplied by estimated probabilities. The events in classes 1 and 2 represint occur-rences that are anticipated during plant operation; and their consecuences, which are very Exceo for small, are considered witnin the framework of routine effluents from the plant.
a limited amount of fuel failures and some steam generator leakage, the events in classes 3 througn 5 are not anticipated during plant cperation; but events of this type could occur Accidents in classes 6 ano 7 and small accicents sometime curing the 40-year plant lifetime.
in class 3 are of similar or lower probacility than accidents in classes 3 througn 5, but are The procability of occurrence of large class 8 accicents is very small.
still possible.
Therefore, when the consequences indicated in Table 7.2 are weignted by probabilities, the environeental risk is very low.
The postulated occurrences in class 9 involve secuences of successive failures more severe tnan those recuired to be considered in the design bases of protection systems and engineered 1753 107 7-i
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I Tatde 7.1. Classefication of poetulated assidents and osmurrences 71 f
Cass N RC descristson Apolicant's eaamples M
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Trivial encioents inciuced en the evasuation of routsne reteasas 2
small releases outs.de inesuded in the evWuation of mntainment routune reteases 3
Radioactive weste system Raisanes from the oorces recovery y
fa*4ure tant, process pas system. and hyl-level waste drain tank a
Fession products to primary "f at &=cl:cse'e g) syster=i (BW R)
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s Fiss.on oroducts to creary steam generator tube leaks or tuae rupture 7
and so.ndary symn.
(PW R) 7t:
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6 Refuehng accident Fuel assemotv dron: heavy otnect drop onto s.on c,e n
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7 scent fuel handling Fuel assembiv drop in the fuel 1
acodent poca: heavy otnect drop onto fuse storage rum: bet cask droo
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Accent initiation events Pios teesk:: roa efecteon accident:
3
.n cons.de.d.n des,.eas.
mom une ereaks evaluation en the safety
'd Anadysis Reoort (sAR)
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Hypotnatical sequence of Not considered f aiiures more wvere than ciass 8 g
S safety features. Their consequences could be severe. However, the probability of their L*'
occurrence is judged so small that their enviror. mental risk is extremely low. Defense in depth (multiple pnysical barriers); quality assurance for design, manufacture, and operation; y
continued surveillance and testing; and conservative design are all applied to provide and maintain a high degree of assurance that potential accidents in this class are, and will y
remain, sufficiently small in probability that the environmental risk is extremely low.
b The NRC has performed a study to assess these risks more quantitatively. The initial results of these efforts were made available for coment in draft form on August 20, 1974,1 and released EG I in final fem ori October 30, 1975.2 This study, called the Reactor Safety Study, was an effort
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to develop realistic data on the probabilities and consequences of accidents in water-cooled q
power reactors in order to improve the quantification of available knowledge related to nuclear
- .d reactor accident probabilities. The Comission organized a group cf about 50 specialists under
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the direction of Professor Noman Rasmussen of MIT to conduct the study. The scope of the study V9y has been discussed with the EPA and described in correspondence with the EPA, which has been Q
placed in the NRC Public Document Room (letter, Ocub to Dominick, dated June 5, 1973).
91 7 f' In July 1977, the NRC organized the independent Risk Assessment Review Group to (1) clarify the achievements and limitations of the Reactor Safety Study (RSS), (2) assess the peer Q d c:cr:ents thereon and the responses to the cocinents, (3) study the current state of such risk assessment xethodology, and (4) recomend to the Comission how and whether such methodology a
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- 1 can be used in the regulatory and licensing process. The results of this study were issued k',h September 1978.3 This report, called the Lewis Report, contains several findings and recom-
=endations conceming the RSS. Some of the more significant findings are sumarized below.
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A number of sources of both conservatism and nonconservatism in the prooability M
calculations in RSS were found, which were very difficult to balance. The Review Grcus V
was unable to detemine wnether the overall probability of a core-melt given in the RSS was high or low, but they did conclude that the error bands were understi.ted.
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The methodology, which was an im ortant advance over earlier methodologies that had es been apolied to reactor risk, was sound.
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7-3 Tab:e 7.2. summary of radiolog.cas eennouenen of convieted no dents' Estimated fracta Estimated sose of 10 CRP 20 to populanon in Em limit at site Mde riosus boundary (man-reens) 8 e
e 1.0 Trivias mcidents c
e 2.0 Smad reintes outside containment i
3.0 Racicactive system fadures 0os2 8.2
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0,20 25
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3.1 Eouipment teamage or maifunction 3.2 Reeaw of waste gas storage tank contents 0.o06 o.68 3.3 Release of liquid waste storage contents N. A.
N. A.
'l 4.0 Fission products to pnmary system (3WR) 5.0 Fission products to onmary and secondary systems (PWR)
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$.1 Fuel cladding defects and steam generator leaka l
j 5.2 Off 4esign transients met induce fust fadure above 0.o01 0.14 i
thou poected, and steam generator leak 0.068 8.2 S.3 Steam generator tube ruoture 6.0 Refuence accidents 0.011 1J 8.1 Fues bundle droo 0.19 22 i
6.2 Heavy obiect droo onto fuelin core 7.0 Soent.8uei nandling accioent 0.o07 0.82 7.1 Fuet assemniv crop m fust storego pool 0.o27 3.3 7.2 Heavy obiect droo unto fuet reca 0.17 23 7.3 Fuei casa droo Accicent.mtietion events considered in cessgn-buis evaluanon m me SAR 8.0 8.1 1.osaef<oolant acendents 0.11 25 Small brum 0.10 3a Large break N. A.
N. A.
Brum in instrument line from onmary system mat onnetrates the containment 0.010 3.4
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8.11al k7 8.21a1 Rod eleccon acc2 dent (PW R1 N. A.
N. A.
8.2(bl Rod drop accident (SWR)
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8.3(as Steam kne brasas (PWR's outssce containtnent)
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<0.1 Small bruk
<0 001
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Large break N. A.
N. A.
8.3tbi steam line break (8WRI
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- The cosas caiculated as consecuences of the postulated accusents are based on aeroorne transport of radioactive materials. resultmg e notn
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a direct and an ennaiation oose. Our evaluacon of rne accioent doses assumes that the aconicant's environmental monitorme prog am and acoropriate sodiconal monitorreg lenien could be metated subseouent to a liowed reiease incident cetected by inciant monitoririgs wound g
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detect tne presence of radioacovity in tee environment in a timely manner sucn that remeaial action could be taken. if necessary. to limit
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esposure Prorn other poteritial patnways to man.
Represents the caiculated fraction of a wnoie-oaov dose of 500 mdhrems, or the eovivaient cose to an organ.
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eThese..om.cisoe,ein.es are considered in oeveioomg me gaseous and inouid source tenn resented in s.ct. 3 and a,e,nciudeo in.osesAi.
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in sect. 5.
$Ie NT In g.r It is very difficult to follow the detailed thread of calculations througn the RSS.
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particular, the Executive Surtnary is a poor description of the contents of the report.
should not be used as such, and has lent itself to misuse in the discussion of reacter
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risk.
On January 19,1Q79, tne Commission issued a statement of policy c:ncerning the RSS and tne The Corriission accepted the findings of tne Review Group.
Review Group Report.
Table 7.2 indicates tnat the realistically estimated radiological consecuences of :ns postulated accidents would result in exposures of an assumed individual at tne site bcundary that are less tnan tnose that would result from a year's exposure to the maximum permissible concentra:1cnsDe (MPO) of 10 CFR Part 20.
tien witnin 50 miles of the clant from each postulated accident. Any of these integrateo ex:o -
When c:nsidered sures would te mucn s= aller tnan that from naturally occurring radioactivity.
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