ML19260D312
| ML19260D312 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 10/31/1979 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19260D310 | List: |
| References | |
| SECY-79-594, NUDOCS 8002080302 | |
| Download: ML19260D312 (16) | |
Text
<J,
3 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 2o5s5 INFORMATION REPORT FOR:
The Comissioners FROM:
Harold R. Denton, Director
,0ffice of Nuclear Reactor Regulation THRU:
Executive Director for Operations
SUBJECT:
CLASS 9 ACCIDENT CONSIDERATIDNS PURPOSE:
To inform the Comission of staff activities relating to consideration of Class 9 accidents in NEPA and Safety Reviews.
BACKGRDUND:
'By memorandum dated September 14, 1979 from Samuel J. Chilk, Secretary, to Lee V. Gossick, Executive Director 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 Commissioners:
(1) how it intends to define Class 9 and design basis accidents, (2) how these accidents will be included in reviews (am 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 recuest.
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 recommendations on how the proposed Annex to Appendix D,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 Comission's attention, any individual cases in which the staff believes the environmental consecuences of Class 9 accidents should be considered.
SCOPE:
To be fully responsive to these requests the staff concluded that its approach to these questions should encompass Commission responsibilities under both the Atomic Energy Act (i.e., protection of the public health and safety) and the National Environmental Policy Act (NEPA). A brief sumary of staff practices and devel-opments in cealing with accident considerations in 19'38 325 contac'
- n.,nayne Hous:cn, Nnn-800208o 3 O A
2 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.
Classifyino and Definino Accidents (a) NEpA Reviews (Environmental Impact Statements)
The proposed Annex to Appendix D 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 ccn now be made c3 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 environmental consequences based upon work which has been carried on by the 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. The 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.
1938 326
DISCUSSION:
(b) Safety Reviews and Design Basis Accidents (continued)
As described more fully in part A. of Enclosure 1 many different kinds of events (failures) are postulated for the purpose of safety evaluations and to assure acceptability of design features.
A traditional methodological approach has been the identification of accident events or scenaric*,
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 carriad out for every new case. A recent example of this latter approach is found in the report of the NRC/ EPA Emergency Planning Task Force (NUREG-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 determinations.
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.
Acolication 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 withhold completion of any unissued Environmental Impact Statements on cases currently under review.
M38 327
DISCUSSION:
(b) Safety Reviews (continued)
Thestaff(LessonsLearnedTaskForce) expects to recomend rulemaking to establish specific requirements for all plants for design features associated with core melt accidents.
3.
Siting Revision In Licht 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 Recomendation 1 of this report were implemented in revised siting criteria regulations, population criteria 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 Sit-ing 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 current inves'.igations regarding Three Mile Island, viz., the Kemeny Comission and the NRC/TMI Special Investigation Group.
The staff recomends, therefore, that a rulemaking be undertaken, considering the above inputs, to restructure and revise 10 CFR Part 100.
It is anticipated that this effort would require about two years to complete and would involve 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 (5.562) might result in a substantially speeded up time table for at least a portion of this effort.
1938 328
5 DISCUSSION:
Sumary:
(Continued)
The staff is pursuing the following:
Preparation of an interim policy statement on accident risks under NEPA which include consideration of core melt events and which would withdraw the 1971 proposed Annex.
Preparation of recomendations for design features for all plants associated with core melt accidents.
Preparation of recomendations for rulemaking to revise 10 CFR Part 100, to encompass considerations of the risks. associated with core melt, events.
/
Harold R. Denton, Director Office of Nuclear Reactor Regulation
Enclosure:
1.
Accident. Considerations in Safety
. vs Environmental Reviews - Staff Practice and Developments 1938 329
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 given plant-site combination, as well as in determining the adequacy and effectiveness 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 follows:
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 failure is the loss-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 r? vised regulations (39 FR 1001, January 4, 1974), and con-tainment are provided to mitigate the consequences of such accidents.
The Commission's regulations in 10 CFR Parts 50, " Licensing of Pro-duction and Utilization Facilities," and 100, " Reactor Site Criteria,"
are complementary elements of this third 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 1938 330
2"-
categories - " credible" and " incredible." The former (" credible")
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 "ineradible". 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 reruit in potential hazardi; 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 f ashion 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 exposed and the performance of other systems available to mitigate the release 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 each 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 Commission's regulations. For further details regarding staff prac-tices in safety reviews, reference is made to SECY 78-111, " Current Acci-dent Evaluation Practices in Siting and Licensing of Nuclear Power Plants,"
and NUREG-0525, " Report of the Siting Policy Task Force."
1938 331
3 B.
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 f ailures 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, manuf acture, 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 probability that the environmental risk is 1938 332
s 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 prohided 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 prohide " assumptions as realistic as the state of knowledge permits."
Consequently, the major difference between accident considerations for environmentalrehiewsvs.safetyreviewsistheemphasisuponadiscussion 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 harious 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 in 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.
1938 333
5 C.
Recent Developments 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 fom in August 1974 and in final fom 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 su:h 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 stvly as a generic study mada to assess the risks of severe accilents in a more quantitative fashion, but, in keeping with t' a guidance of the proposed Annex, not to discuss site-specifi. Class 9 events in the environmental statements.
(2) Risk Assessment Review Grouo:
In July 1977, the NRC organized the above
'oup primarily to clarify the achievements and 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 detemine 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.
1938 334
~
(3) Agency and P.iblic Comments The staff's environmental statements have generally received a much wider circulation among other governmental agencies and the general public than the Safety Evaluation Reports. A Targe number of the comments 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 comments 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 probability of such evt.nts.
(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 recommended to the Commission on March 7, 1978 that:
(a) Pending completion of the Commissions 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.
(b) ThLt the Commission consider the appropriateness of issuing some clarifying statement to the effect that the 1938 335
-7.
proposed Annex to 10 CFR Part 50 Appendix D 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) R'eport of The Siting Policy Task Force (NUREG-0625)
In August 1979, the Siting Policy Task Force recommended that siting policy changes be made "To take into consideration in siting the risk associated with accidents beyond the design basis (Class 9) by establishing population density and distribution criteria." The recommendations 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 Commission issued a policy statement concurring in and endorsing the guidance contained in the Task Force Report.
The'Connission 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."
ATTACHMENT A
- g 9
9 t
7.
ENVIRONMENTAL IMPACT OF POSTULATED ACCIDENTS 7.1 POSTULATED ACCIDENTS INVOLVING RADICACTIVE MATERIALS A high degree of protection against the occurrence of postulated accidents in the Greene Cc:anty 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 Comission'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 ectur, even though they may be extremely unlikely; and engineered safety features are installed to mitigate the conse-quences of those postulated events that are judged credible.
[
The probability of the occurrence of accidents and the spectrum of their Lonsequences to be considered from an environmental effects standpoint have been analyzed using best estimates of 4
For site evalu-probabilities and realistic fission product release and transport assumptions.
I ation in the Commission's safety review, extremely conservative assumptions are used to compare calculated doses resulting from a hypothetical release of fission products from the fuel with 7
the 10 CFR Part 100 siting guidelines. Realistically computed doses tnat would be received by the population and environment from postulated accidents would be significantly less than those to be presented in the Safety Evaluation.
The Comissien 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 assumotions and guidance issued as a proposed amendment to Appendix D of 10 CFR Part 50 by the Commissica on December 1.
Nine classes of postulated accidents and occurrences ranging in severity from trivial to
~ -
1971.
very serious were identified by the Comission. In general, accider.ts in the high-potential-consequence end of tt.e spectrum have a law occurrence rate, and those on the low-potential-The examples selected by the applicants for consequence end have a higher occurrence rate.The examples selected are reasonably homogeneous in terms these cases are shown in Table 7.1.
of probability within each class.
Comission estimates of the dose that might be received by an assumed individJal standing at -
the site boundary in the downwind direction. Using the assumptions in the proposed Annex to Estimates of the integrated exposure that might ce Appendix 0, are presented in Table 7.2.
The delivered to the 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 represent occur-rences that are anticipated during plant operation; and their consequences, which are very Except for small, are considered within the framework of routine effluents from the plant.
a limited amount of fuel failures and some steam generator leakage. the events in classes 3 through 5 are not anticipated during plant operation; but events of this type could occur Accidents in classes 6 and 7 and small accidents sometime during the t.0-year plant lifetime.
in class 8 are of similar or lower probability than accidents in classes 3 through 5, but are The probability of occurrence of large class 8 accidents is very small.
still possible.
Therefore, when the consequences indicated in Table 7.2 are weighted by probabilities, the environmental risk is very low.
The postulated occurrences in class 9 involve sequences of successive failures l 1
}h)h h37 7-1
7-2 Tehle 7.1. Clas:sf.cet.on of posiulated onesdents and ocunerreness C2 ass NRC descripison Appicant's examspes 1
Trreeni irodents incNdad in the evehaeoon of routens re4 eases 2
small reeenses outods Inchased in tre evakaatson of contasament routone rummes 3
Rad oectrve wasis system Reesases from the hormi recovery faibre tar *. prcorns pas sptern, and higP>
4evel vueste drain tank 4
Finwon products to prwnery
.Not apphcable system (BWR) 5 Fasen products to prwnary steam generator aabe tasks or tube rupture and secondary systews (PWR) 6 Refusiing aszadent Fuel assembty drop; heavy ob,ect drop I
onto fuel in core I
7 spent fuse handhng Fuel assemedy drop in the fuel g
aczadent pood; hoevy otgecs drop onto fuel storage rock; fuel cask drop l
8 Accadent initetson events Pee breaks; red etecreon acadent, consedered in desagn-basas steam lene breaks evakatson in the safety-I Anaeynes Report ($AR) 9 Hypothetcal seosence of hot considered failures more seveee than dass a safety features. Their consequences could be severe. However, the probability of their occurrence is judged so small that their environmental 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 a high degree of assurance tnat potential accidents in this class are, and will remain, sufficiently small in protability that the environmental risk is extremely low.
~ The NRC has performed a study to assess these risks more quantitatively. The initial results of these efforts were made available for corsnent in draft form on August 20, 1974.1 and released in final fom ori October 30, 1975.2 This study, called the Reactor Safety Study, was an effort to develop realistic data on the probabilities and consequences of accidents in water-cooled power reactors in order to improve the quantification of available knowledge related to nuclear reactor accident probabilities. The Commission organized a group of about 50 specialists under the direction of Professor Norman Rasmussen of MIT to mnduct the study. The scope of the study has been discussed with the EPA and described in corrtspondence with the EPA, which has been placed in the NRC Public Document Room (letter Doub tu Dominick, dated June 5,1973).
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 cmrnents thereon and the responses to the corrrnents, (3) study the current state of such risk assessment methodology, and (4) recorrrrend to the Corrlission how and whether such methodology can be used in the regulatory and licensing process. The results of this study were issued September 1978.3 This report, called the Lewis Report, contains several findings and recom-mendations concerning the RSS. Some of the more significant findings are surraarized below.
1.
A number of sources of both conservatism and nonconservatism in the probability calculations in RSS were found, which were very difficult to balance. Tne Review Group was unable to detemine whether the overall probability of a core-melt given in the RSS was high or low, but they did conclude that the error bands were understated.
2.
The methodology. which was an important advance over earlier methodologies that had been applied to reactor risk, was sound.
1938 338
- g. amen..
~
'%="~~'~
IN i
7-3 k
7,oss of posa, Land seculents*
Tatde 7.2. ! - m of._ _ P _
E.T.~.= cow y;
Estimated frm.
of toCRP 20 to populat on in pp h
Shine raceus limit at one 2
tsound s waa.roma 3'
l c
lh e
c la Trwini sneidents e
s W
Smaf t rotessas outs de contamnunt
'j -
2A
-6.2 3D Rad.oactrue system fa.4ures o.oS2 25
- {,
Eouipment teakage or malforction oJo 11 o.68 Release of waste gas storage sank contents 0406 96!
12 N. A.
Reksase of legund meste storage contsats N. A.
@]
3J Fiss.on prooucts to primary system (BWR) h ah Fampon prooucts to pnmary erus seconcery systems (PWR) c y
e Eo Fuel ciaodeng oefects and staam generator ieds y
5.1 s
0.14 oef.dm.gn trans. ants met inouce fusi fe sure soove 04o1
/
s.2 8.2 those espectac. and steam generator seek o.068 5.3 Seeam generator tube rurture p
bj 13 Eo Refusiing anocents 0411 22 El Fuel tiundw drop oas weeiy ob,eci oreo onto fu.a in cor, ei s2 c.82 74 Spent fuel haruSeng accroent olJo7 M
3J Fued assemtsy orop in fuel stcrage pool 0427
'nM 7.1 2D sewy on.ect drop unto fuel rock od7 M
7.2 Acocent enetistion events cons.oered in ces gn basis evnavation in the SAR h(
Fue6 cask crop 7J 8o 25 SJ Lossef coolant acesoants o.11 Smasi treak o.1o 34
]'
N. A.
Lsge treek N. A Breat en snatrunent ice from premory system that penetrates the containment 3.4 oD10
~
8.11a)
N. A.
Rod e,ect.on accioent (pwR)
N. A 8Jia)
. Rod crop accident (BWR) j SJfD)
Steam line treaks (PWR's outside conta.nment)
<D.ool j
C7 8.3tal
<o.1 Small tweak
<o. col
}
N. A.
Lary treak N. A.
S.3lb)
Sieam term treak (BWR)
- 9 e comes caaculated as consequences of the postulatec accidents are based on as.m tra a
f
?
a derect eno sn inhalation cosa. Our e=aisation of the aceicent doses assut ottected by m9 ant monitoring) would t
sopropriate additional monitormg (whicn criu6d be enetisted suoteouent to a leausd re6 ease incioem 3
if necessary. to limit otteet trbe presence of radioactwity en the environment en a teme*y manner such that remecial action couldf empcsure from omer potential perways to man.
Represents the calculated fract,or, of a whoie body dose of Soo m.iterems. or the ecuevaient cose to an organ,ntec i
)
y
[
8
- Thew raa.onuctice reemes am cons.oered in oeveco.ng tne gueous end t ou.d source term pree
[
e sect. L i
r l 4 In It is very difficult to follow the detailed thread of calculations through the RSS.
t 4
particular. the Executive Sumary is a pocr description of the conte In' 3.
D risk.
tre Comission issued a staterrent of policy concerning the RSS and the The Conrnission accepted the findings of the Review Group.
On slanuary 19. 1979, Reyiew Group Report.
the postulated Table 7.2 indicates that the realistically estimated radiological conse h t are less f
ible concentrations than those that would result from a year's exposure to the maximum permissThe ta l
F (MPC) of 10 CFR Part 20.
Any of these integrated expo-tion within 50 miles of the plant from each postulated accicent.sures would When considered
7-4 with the probability of occurrence, the annual potential radiation exposu ground radiation and, in fact, is well within naturally occurring variations in risks due to postulated radiological accidents are exceedingly small and need not be considered background.
further.
7.2 TRANSPORTATION ACCIDENTS The transportation of cold fuel to the plant, of irradiated fuel from the reactor to a fuel 1
reprocessing plant, and of solid radioactive waste from the reactor to burial grounds is within l
the scope of the AEC report entitled L%vironmental Survey of Transportation of RadioactiveThe environme Netmals to and from Nuciscr Power PIcncs, dated December 1972.
i accidents in transportation are sumarized in Table 7.3.
Tatde 7.3. Epowennental noks of accioents in wensport of fuel end marie to and from o typ.callightwater-coeded nummene poseer rosetor*
l Erweronmental risk sman*
Radioaog cal ef1 acts 1 f atal ineury in 100 reactor-Cearnen (nonredervogicall causes yevs: 1 nonf utal miury en to reactorwars: s*75 property damaae per reactoe year
- Data supoemne this tatge eve e.ven in the Commiss.on's Envuonmental5urvey of Transoortaten of Radeactne Waterats to and imm huenar Power Ptents.
WAs*1238, December 1972 and Suppl.1 (NUREG 7 slo 38). April 1975.
- Altnougm. the en..conmenter rak of rad.eJapcal effecu stemming from transportation accents es currently incapatne of be,ng numeecaHy cuantif.ed. the rnk remains small regardless of whether it is being apphed to a sangle-reactor or a muirireactor sets.
a REFERENCES FOR SECTION 7 An Assessment cf Accident Risks in U.S. Comercici Nuciect Pwer 1.
Reactor Scfety S:.dy:
Plants, traft, WASH-1400, August 1974 cf Accident Risks in U.S. Comericc1 Nucisar Pouer An Assessmen:
Reccter Safety St.dy:
2.
PIcncs, WASH-1400 (NUREG 75/014), 0:teber 1975.
3.
Rhk Assessment Revieu Croup Repcrt, NUREG/CR-0400, September 1978.
tD
%k 9@9 1938 340 N.