ML25167A213
| ML25167A213 | |
| Person / Time | |
|---|---|
| Issue date: | 09/06/1984 |
| From: | Asselstine J Advisory Committee on Reactor Safeguards |
| To: | Ebersole J Advisory Committee on Reactor Safeguards |
| References | |
| Download: ML25167A213 (1) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555 September 6, 1984 tffliORANDUti FCR:
Jesse C. Ebersole Chairman, ACRS FROM:
//?
Jomes K. Asselstinr-~ /.~~A
SUBJECT:
SEVERE ACCIDENT POUCY STATH1ENT Or; July 10, l9f.t, I wrote to you requesting the ColTlffiittee's comments on several questions related to the staff's proposed Severe Accident Policy Statement.
Following my me,~1orandum, y('u and several other members of the Cor:1nittee met with me to discuss my questions regarding the policy staterr~nt.
In light of our discussion, we agreed that it would be useful for me to refine and clarify my questions to the Committee.
Acccrdingly, I \\o;OUl d apprHi ate the Comr.1ittee 's thoughts on the foll ow-ing:
- 1.
It seems to r.ir that it wol!ld be helpful to the Commission, in consic'u*ing the acequacy and cc,r.1pleteness of the Severe Accident Polit} ~tatement, to have at least a general under-st2rding of the likelihood o~ the occurrence of a severe accidt~t in the fcrPseeable future, assuming the continuation of our rresent regulatory approach and program.
I would therefore appreciate the Committee's views on the likelihood, giver. our present understanding of current LWR technology, thE present c:apabilit_y, qualificc:tions and attitudes c,f the utilities ore:n1ting nuclear powerp1a11ts and our present regulatory program aric approach, that an accident involving larg~-scale de£radation or melting of the reactor core will occur between no~ and the year 2GOO.
I should emphasize that I am net askin~ for some precise, numerical probabilistic judgffie~t, which I think we agree is not possible. Rather, I am interested in a ~ore qualitative judpment, such as whether such ar, accident is highly unlikely, some~hat unlikely, not unlikely, or highly likely, given our present knowledge of the factors listEd above.
- 2.
It seems to me that the occurrence of a severe accident {i.e.,
an accident involving large-scale degradation ~r melting of the reactor core) within the next 16 years would have very serious adverse consequences on public confidence both in our regulatory prograM and in the safety of the plants, even ;f the actual immediate health effects from the accident were limited. would the Committee agree, and is this a factor that the: Contnission should consider in its evaluation of the 1992
2 proposed Severe A~cicer.t Policy Statement? For example, would it be useful, in light of your answer to question one, to include in the policy stateMent a statement to the effect that it is a fundamental objective of the Commission's severe accident policy to ta~e all reasonable steps to minimize the occurrerce of a severe accident involving large-scale degrada-tic~ or melti~~ cf the reactor core and to mitigate the consequences of such an accident should one occur?
- 3.
CJoe:~ the Comnittee believe that the occurrence of a severe accider,t is more likely at somt plants than at others? If so, what are the significant contributors at the plants where a severe accident is ~ore: likely? In particular, how signifi-cart a factor is the licensee's management and operating capa~ilities anc attitudes, and is a severe accident more likely at a plant with weak manapement and operating capabil-ities and attitudes?
- 4.
If a severe accir:~nt is not unlikely during the next 16 years, what further steps could be taken, beyond those described in the proposed Policy Statement to minimize the occurrence of such an accident or mitigate its ccnsequenc~s? I note, for example, that the Committee's July 18, 1984, letter to the Cor.1r1issior. ~cE:T.1s to recommend a systematic examination of each plant. Shculd the Commission require a plant-specific Pr..e. for c2ch plant? ~~at other m~asures mipht be useful? Would focusing attention or. weak perforriF.rs in the areas of manage-ment and operct.ing capabilities and attitudes be helpful?
- 5.
Cost-t.enefit analysis woulc! play a key role under the proposed policy statement in considering further measures to address severe acci~ents.
Does the policy statement over-emphasize cost-benefit analyses and PRA as a decision-making tool?
Given the substantial ~rcertainties in calculating risks, co~.1:5 c,nd benefits in this areas, shoulc the policy statement emphasize the us~ of more qualitative engineering judgment?
f..
The prcposed poliq statement includes son,c statemerits that cculd be read to mean that major hardware changes will not be needed to address severe accidents fer txisting plants.
Would it be mere accurate to say that w~ cennot now identify one or more specific changes which are necessary and appropriate on a generic basis, bt:t that such changes are possible depending upo~thc outcome of cur severe accident research program and cannot be ruled out at this time?
- 7.
How should the resolution of unresolve~ safety issue A-45, decay t,eat removal, fit in with the Severe Accident Policy Staten~nt? For exaMple, should the prograM to resolve A-45 be a broa~-based program that examines in detail alternatives such as a new, independent decay heat removal train, or should 1993
it be a limited progr*ar, aimed only at procedural changes to improve the reliability of e:xisting decay heat removal systems in the plants? Shoulc this be discussed in the policy staterr.ert?
I gr~ctly appreciate the Committee taking the tiRe to consider these questions.
I alsu want to express my appreciation to you and the other members rf the Co~~ittee who met with me to discuss this subject.
I founrl that meeting to be of exceptional value to me, and I hope that we can have similar r.ie:etings in the future or, other subjects of mutual interst. This ty(:P cf dialogue can only imrrove the quality of the:
C0nr;ission 1s decisions.
cc:
Chairmnn Palladinr.
Ccmrrissiorer Roberts Con1:ii ss i oner BernUc: ~
Ccr.:rnissioner Zech SECY rnr 1994