ML20198F107

Forwards Realistic Accident Section for Des

ML20198F107
Person / Time
Site:	Satsop
Issue date:	10/11/1974
From:	Harold Denton US ATOMIC ENERGY COMMISSION (AEC)
To:	Muller D US ATOMIC ENERGY COMMISSION (AEC)
References
CON-WNP-1238 NUDOCS 8605280414
Download: ML20198F107 (10)

Text

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D. Muller, Assistant Director for Environmental Projects, L WPPSS 3 & 5 REALISTIC ACCIDEFr ASSESSMDrr Plant Name: UPPSS Nuclear Project Nos. 3 and 5 Liesasing State: CP Docket Number: 50-508/509 Responsible Branch: LUR 1-3 4 Requested Completion Date: October 11, 1974

Applicant's Response Date Necessary for Mext Action Planned on Project: N/A Descr$ption of Rasponse: Realistic Accident Assessment

! Review Status: Accident Analysis Branch Input Complete l Enclosed is the Realistic Accident section for the UPPSS 3 and 5 Draft Environmental Statement prepared by K. Murphy of the Accident Analysis Branch.

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Harold Denton, Assistant Director j for Site Safety Directorate of Licensing

Enclosure:

DISTRIBUTION:

As stated Docket (50-508/509 L Readig cc: v/o enclosure SS Reading A. Cianbusso AAB Reading U. W. Donald SS BC's A. Kenneka J. Panzarella v/ enclosure S. Unnauer P. .'!chroeder >

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Environmental Impact of Postulated Accidents .

A high degree of protection against the occurrence of postulated accidents in the WPPSS; Foclear Project Nos. 3 & 5 is provided through correct design, manufacture, and operation, and the quality assurance program used to establish tha necessary high integrity of the reactor system, as will be considered in the Cocnission's Safety Eval [iation. Devia-tions that =ay secur are handled by prot:ctive systems to place and hold the plant in a safe condition. Notuithstanding this, the con-servative postulate is made that serious accidents might occur, even though they may be extremely unlikely; and engineered safety features are installed to citigate the consequences of those postulated events which are judged credibia.

The probability of occurrence of accidents and the spectrum of their consequences to be considared from an environmental effects standpoint have been analyzed using best estimates of probabilities and realistic fission pr: duct release and transport assumptions. For site evaluation in the Co==ission's safety revieu, extremely conservative assumptions are used for the purpose of conparing calculated doses resulting from a h pothetical release of fission products froa the Ca21 against the 10 CFR Part 100 .*1 ting guid*1ines. pealistically couputed doses that would be received by the population and environ =ent- from tha accidents -

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• which are postulated uould be significantly less than thooe to be precented in the Safety Dialuation.

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. The Consission issued guidance to applicants on Septeeber 1,1971, requiring the consideration of a spectrus of accidents with assumptiona as realistic as the state of knowledge permits. The applicant's response was contained in the WPPSS Nuclear Project No. 3 Environmental Report dated September 10, 1974.

The applicant's report has been evaluated, using the standard accident

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assumpticas and guidance issued as a proposed anendcuent to Appendi:: D

of 10 CFR Part 30 by the Conz1ssion on Dace.cbar 1,1971. Ilice classes

! of postulated accidents and occurrences ranging in severity from trivia).

to very serious were identified by the Concission. Irt general, cccidents in the high potential consequenca end of the spectru:t have a low occur-h rence rate and those on the low potential consequance end have a highee occurrence rate. The exampics colected by the applicant for these cases are shotm in Table I. The e::anples selected are reasonably homogeneous in t, erns of probability within each class.

Connission es:irates of the dose which night be received by an assured individual standin3 at the cite ovo. Mary in the dotinuind direction, using the asme.ptions in the proposed Anne:: to Appandix D, are prosent.ed in Table II. Catimates of the integrated exposure that might be deliverad to the population within 50 niles of the site are also pre-seated in Table II. The can-ren ostinate was based on tha projacted populatic'n within 50 miles of the site for the. year 2021.-

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f l To rigorously cawblish a realistic annual risk, the calculated i

doses in Table II would have to be r:ultiplied by entic:ated probabili-ties. The events in Classes 1 and 2 represent occurrences which are anticipa:ed during plant operatiogs; and their consequences, which, are very s=all, are considered within the framenork of routine effluents from the plant. Er. cept for a limited a::ount of fuel failures and sose steas generator leakage,, tha events in Classes 3 thrcush 5 are not anticipated during picnt; operation; but events of this type could occur sonetice during t.ha 40 year plant lifeti=e. Accidents in Classes 6 and 7 and small accidents in class 8 are of similar or lover probability than accidents in Classes 3 through 5 but are still possible. The probability of

-occurrence of large Class 8 accidents is very small.. The refore, when tha consequences indicated in Table II are weighted by probabilities, the environmental risk is very low. The postulated occurrences in Class 9 involve sequences of successive failures core severe than those required to be considered in the design bases of pro:2ction systees and engincared safety features. Their consequencas could be severe. However, the probab L11ty ef their occurrence is judgel so scall that their environmental ri.sk is crtremely loi. Defensa in depth (nultiple physical barr t.srs), qual-ity assuranca for desi;n, nanuf acture and operation, cent Lnued sur-vaillance and testing, end coa 3crvative design arn all applied to

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provide and maintain a high degree of assurance that potential .

accidents in this class are, and will remain, sufficiently small l in probability that the environmental risk is extremely low.

The AEC is currently performing a study. co assess more quantitatively l

these risks. The initial results of these efforts were made available

, for coccant in draft form on August 20, 1974. This study is called l the Reactor Safety Study and is an effort to develop realistic data on the probabilitics and ccquences of accider.ts in water-cooled power i

reactors, in ordce to improve the quantificatica uf available knowledge related to nuc1 car reactor accidentsprobabilities. The Commission organized a special group of about 50 specialists under the dite: tion

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of Professor Normed Rasmussen of flit to conduct ~the study. The scope i ..

of the study has baen discussed with EPA aad described in correspondence i

, with EPA which has been placed in the AEC public Document Room (letter, Doub'tp Dominick, dated June 5, 1973).

i' As with all new information developed which might hava an effect on the hea1th and cafety of the public, the resulta of these studies will be made public and ulll be assussed on a timely baats within the Regulatory proccas on gencric or npocific bases an n:y bc *iarranted.

s Tabic II indicates that the realisticall> catinated radiologicti i

conocquences of the postulated accidents would result in exposures

• " Reactor Satcty Study: An [uiacsse:ent of Accident Rinko tu U. S.

Cumercial Nuclear ' Pouer l'1 ants, Draf t," 11ASit-1400, August 1974 4

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~5-of an assumed individual at the site boundary sthich are icss than those which would result fron a year's exposure to the Maximum Permissible Concentrations (!IPC) of 10 CFR Part 20. The table also cl.ows tha estimpted intestated exposure of the population within 50 miles of the plant fron each postulaced accident. Any of these integrated exposures vould be nuch scaller than that from naturcily occurring 6

radioactivity. When considerec with the probability of occurrence, the annual potential radiation exposure of the population from all the postulated accidents is an even s= aller fraction of the c::posure from natural background radiation and, in fact, 4s wc]l within naturally ocettrring variations in the natural background. It is concluded f rom the results of the realistic analysis that the environmental ricks due to postulated radiological accidents are exceedingly small and need not be considered further.

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, Table 1. Classification of Postulated Accidents and Occurrences 2

Cirss AEC Description

• Applicant's Examples

1. Trivial incidents Not considered

- 2. Small releases outside containment Evaluated as routine releases

3. Radioactive vaste system Leakage or rupture of failure either the waste gas decay tank or the liquid radwaste storage tank

, 4. Fission products to pri-l- mary system (BWR) Not applicable 1

5. Fission products to pri- Fuel failure above those ex-mary and secondary systems pected in conjunction with (PWR) steam generator leak, steam generator tube rupture

6. Refueling accident Fuel bundic drop, heavy object drop onto fuel in core

7. Spent fuel handling Fuel assembly drop in fuel accident storage pool, heavy object drop onto fuel rack, fuel cask drop

8. Accident initiation events Small or large coolant pipe considered in design-basis break, control element assembly

, evaluation in the Safety ejection, instrument line Analysis Report break, small or large steam-line break

9. Hypothetical sequence of failures more severe than ,

Class 8 Not considered

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c TABLE II SU'O!ARY OF RADIOLOGICAL CO.'! SEQUENCES 0F POSTUL\TED ACCIDE!.T!L/

Estimated Fraction Esticated Dose of 10 CFR Part 20 to Population Class Event linit ae boundarygite 50 mile radius can-ren 1.0 Trivial I..cidents 3] 3/

2.0 Small releases outside

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3.0 Raduaste Systen failures 3.1 Equipnent leakage or mal- 0.02 1.2 functica 3.2 Release of vaste gas 0.079 4.7 storag3 tank contents 3.3 ' Release cf liquid waste 0.002 0.1 i

storags ccatants 4.0 Fission products to primary N. A.

systen (3'G)

N. A.

-1/ The doses calculated as consequences of the postulated accidents are based on airborne transport of radioac:ive natariala resulting in both a direct and an inhalation doso. Our evaluation of the accident doses assures that the applicant's environnental nonitoring progran and -

appropriate additional monitoring (uhich could be initiated subsequent to a liquid release incident detected by in-plant nonitoring) would detect the presence of radioactivity in,the environcent in a ticely

=anner such that remedial action could be taken if noccasary to limit exposure from othat potential pathways to man.

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3epresents the calculated fraction of a whole body dose of 500 nren, or the equivcicat dose to an organ.

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Tnese relcaces are expected to be in accord vitti propon 21 Appandix I for routi'n2 utfluents (i.e., 5 crem par yect to the whole body from either gasacus or liquid effluents).

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8' TABLE II - Continued

- Esticated Fraction Estinated Dose of 10 CFR Part 20 to population Class Event linit at rito in 50 mile boundhry 2 .

radius. man-ra 5.0- Fission products to primary ar.d secondary systems (PUR) '

5.1 Fuel cladding defects and 3/ 3/

steca gacerator leaks 5.2 Off-design transients that 40.001 40.1 induce. fuel failure abova-those c:cpected and stean generator leak 5.3 S,tcan generator tube rupturo 0.026 -

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6.0- Refueling accidents 6.1 ' Fuel bundle drop 6.2 0.004 0.3 Heavy cbject drop onto fuel 0.072 4.3 in core -

s 7.0 Spent fuel handling accident '

7.1 Fuel assenbly drop in 0.003 1.6 fuel' rack 7.2 . Heavy cbject drop onto 0.011 0.6 i

fuhl rcck 7.3 Fuel cesk drop 4

0.063 3.8 S.0 Accident initi tion events

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considerad in design basis .

evaluation in the SAR ,

8.1 Loss-of-Coolant Accidents '

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0.024 Large 3reck 3.9 0.038 5.2 '

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e TABLE II - Continued Esticated Fraction Estimated N3e of 10 CFR Part- 20 to population limit at in 50 nile Class Event boundary2 7. ite radius, can-re=

8.1(a)' Break in instrucent line from N. A. N. A.

Primary systen that penetrates the contain=ent 8.2(a) Rod ejection accidant (EfR) 0.004 0.55 8.2(b) Rod drop accident (E!G) N. A. N. A.

8.3(a) Stedine breaks (Eia's '

outside containment)

Small Break 40.001 40.1 Large Break 40.001 40.1 8.3(b) Stescline break (EIR) N. A. N. A.

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