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Forwards Latest Update of Status of Issue Papers & Format to Be Used Decided Upon in Jan 1984 Sarp Meeting
ML20214W743
Person / Time
Issue date: 02/23/1984
From: Ross D
NRC - SARP REVIEW GROUP
To: Marino G, Mattson R, Ross D
Office of Nuclear Reactor Regulation, NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
Shared Package
ML20213E209 List:
References
FOIA-87-113, FOIA-87-60 NUDOCS 8706160166
Download: ML20214W743 (14)
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t UNITED STATES NUCLEAR REGULATORY COMMisslON y * *g

,g .. WASHINGTON, D.C. 20555 February 23, 1984 o%,

f MEMORANDUM TO: Multiple Addressees FROM: Denwood F. Ross, Chainnan SARP Review Group

SUBJECT:

ISSUE PA*PER STATUS Enclosed is the latest updati of the status of the Issue Papers (Attachment 1).

Please check your IP against the status shown and call G. P. Marino on 74266 if there is an error on your IP status. Also enclosed are copies of the fonnat to be used that was decided upon in the SARP meeting in January 1984, a copy of the signoff sheet that must be completed and attached as a cover before issuance to the SARP Senior Management Group, and a copy of the NRC/IDCOR Position Summary sheet to be attached after the corresponding NRC/IDCOR meeting on the issue. Due dates to SARP will be negotiated with myself by the cognizant Divisional Technical Leader.

fk N .

Denwood F. Ross, Chairman SARP Review Group

Enclosures:

As stated I

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ATTACHMENT 1 CURRENT FORMAT OF NRC ISSUE PAPERS ISSUE PAPER TITLE

1. Description of Issue - This has generally been done well.
2. Implications of the Issue to Regulatory Questions - Generally 0.K.
3. Subissues - Generally 0.K.
4. Status of Understanding - Generally 0.K. - should contain IDCOR methodology and understanding as well as that of the NRC without critical comment.
5. NRC Position - This section should contain the NRC position for end of FY 1984 viz-a-viz the ASTP0 studies, the ASEP studies (if applicable) and the SARRP work (if applicable). Dr. Mattson suggested, and it was

......."Our agreed, that a sentence or two should be included such as evaluation of this issue relative to the source term. ASEP, and SARRP re sul ts i n the current NRC posi tion of . . . . . . . . . . . " "This position requires IDCOR to do the following ..........." and soggests the conduct of the confimatory work discussed below."

6. Continuinc Confirmatory Work - Single out on those programs useful and needec .

If work may not be necessary, say so.

I e

e

1 Issue Number

- Title Prepared by: Signature of Author:

Draft i Date Contractor / Consultants Revisi *-9 cess (List here contractor who will supply a statement on issue relative toIDCORwork)

Initial Date Branch Chief 7"'.. Div. Dir. ,

Division Dir.

Tech. S: ries Div. Director flate sent to ACRS -

Datt fant to IDCOR ,

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SARP DISTRIBUTION LIST i

GPMarino, RES DFRoss, RES "

RJMattson, NRR ,

TSpeis. NRR <

ZRosztoczy, NRR l RVollmer, NRR MErnst, RES RBernero, RES GArlotto, RES OEBassett, RES JTlarkins, RES RDenning, BCL DJGarner, OCM JKJoosten, OCM ,

JAustin, OCM JMeyer, OCM SHChesnut. OCM AWang, ACRS JTHan, RES MSilberberg, RES RCurtiss, RES RWright, RES '

JRosenthal, NRR TWalker, RES -

CTinkler, NRR BBurson, RES VNoonan, NRR WButler, NRR JCostello, RES WFarmer, RES LSoffer, RES JMartin, RES PBaranowsky, RES '

BAgrawal, RES

!- C0verbey, RES ,

JMurphy, RES

! FRowsome, NRR GBurdick, RES

( JWermiel, NRR l MJankows.ky, RES WPasedag, RES LChan, RES '

JTelford, RES RBarrett, NRR l _

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  • 12.3.1 Design and Operation Changes to Prevent Severe Accidents Including

~ Sabotage Protection m

1. Implication of the Issue to Regulatory Questions This issue is directly associated with the fourth regulatory -

I question: how can the level of protection for severe accidents be increased? As-its name indicates, this issue relates to ways of protecting against severe accidents by the prevention of these accidents. This prevention can occur either by improving the use  ;

of existing equipment (e.g. by improved operational reliability, procedures, testing and maintenance) or by providing additional equipment (e.g. dedicated shutdown heat removal systems). Of interest here are both the identification of the various ways of preventing severe accidents and the measurement of the benefit achieved by these ways, individually and in combinations. i

2. Subissues Measure of benefit (core melt frequency reduction, risk reduction, improvement in defense-in-depth)

Generic applicability of measured benefit Relative importance of prevention vs. mitigation Benefit already achieved by TMI-fixes l

Impact of uncertainties poorly understood, unknown sequences (e.g. seismic, sabotage) component, common-cause failure data (e.g. human error rates)

Relationship to unresolved safety issues (e.g. USI A-45, Alternate Decay Heat Removal Requirements)

If cost / benefit is about one, are changes mandated or not?

l 3. Approach to Resolution In order to address this issue, three types of data are needed:

(1) prevention options of potential merit; (2) an assessment of the risk from the specific or generic plants (including dominant sequences, system models, important systems, failure modes, consequences of specific sequences); and (3) cost information on plant modifi-cation options. With this data and measures of associated un-certaintief., the core melt frequency or risk reduction ciM=

benefit can be calculated as well as cost-effectiveness value.

In the Severe Accident Risk Reduction Program (SARRP) and with _

input from supporting programs, such calculations are being made _

in an iterative manner, consistent with the phases identified in the Severe Accident Research Plan (SARRP).

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. . _ _ . _ ~ _ . . . . __ _ . _ _. ..... ... . . . . . . . _ . _ .

Phase I

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Tim sets ,of cost-benefit calculations are being performed in the 1 SARRP phase I work. In the first set: j

.a relatively broad spectrum of prevention options was identi.fied;

- six existing PRAs (Reactor Safety Study, RSSMAP) were used-as the risk assessment base; and

- very rough cost measures were assessed. ,

With this supporting data, methods were developed for calculating and displaying risk reduction benefit and cost-benefit, as well as important sensitivities and uncertainties.

The second set of phase I calculations will be using:

a narrowed list of options and combinations (with less promising options screened out);

an expanded base of risk studies for generic classes of plants, using data on accident sequence likelihoods synthesized from

a broader set of PRAs, and consequence data reflecting up-to-date understandings of the phenomena involved; and nere detailed cost estimates, with support fran an architect-engineering firm. ,

With this data the risk reduction and cost-benefit calculations __

described abov,e will be redone, on a schedule consistent with the mid-84 severe accident commission paper.

Phase II The phase II SARRP evaluation of core melt frequency or risk reduction benefit and cost-benefit of accident prevention options is oriented with the completion of a further evaluation of accident sequence likelihoods (which includes consideration of external events) and with the completion of most of the severe accident experimental programs. Using this new data on accident probabilities and consequences, the^ cost-benefit, sensitivity, and uncertainty calculations will be redone.

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4

4. Status of Understanding At this time, the potential risk reduction benefit of preventio'n ~~

options is relatively well understood for a set of specific plants, based on the RSS and RSSMAP risk assessments. More robust and generic information is not available because of incomplete study of the competing risks of option installation and use, the costs-of such options, and the more generic extension of these plant-specific results. Many of these issues will be accounted for in the second set of phase I calculations, either by refined calcu-lating or by sensitivity studies. Issues assessed by these sensi-tivity studies in phase I will be the focus of phase II work.

5. NRC Position .

From the calculations made to date, it appears that major modifi-cation to prevent severe accidents (e.g. dedicated shutdown heat removal systems) will be difficult to justify on the basis of quantitative cost-benefit calculations. Combinations of lesser modifications, however, can be expected to be marginally cost-effective. In addition, consideration of uncertainties and poorly-quantified sequences (e.g. , seismic events, sabotage),

or less quantitative (probabilistically) methods (e.g. ensuring defense-in-depth) could lead to recommendations for requiring . . -

modifications which are, at best,ss_qs_t effective; maFginally)'if o,nly quantitative best-estimate analysts was used.

6. IDCOR Position Little is known about the IDCOR analyses at this time. However, general statements have been by IDCOR management that their analyses indicates very low risk from existing LWRs. Because of this assessment and the corollary ,that no further risk reduction is needed, little quantitative evalaution '

of measures to reduce risk has been made.

l

" Prortet Number

@Battelle Columbus Laboratones

- om December 9. 1983 ~ " - 4 To Writers of Issue Papers Author: M. Cunningham

/ / Area Leader: R. Bernero

' Frrm Richard S. Denning Q.J. ) -Reviewers: M. A. Wal tiers ,

b R. S. Denning Subject Comments on Issue Paper 2.3.1 Issue-2.3.1 Design and Operation Chanoes to Prevent Severe Accidents ,

Including Sabotage Protection This is a well written paper but it should provide more information, particularly under status of understanding.

1. Description of the Issue

.You did a good job of defining the issue in your Section 1. It has been decided that a new introductory section should be included in each paper to describe the issue. At some point you should list the options under consideration, either in this section or under Status of Understanding. How about a few nice motherhood statements about prevention vs. mitigation?

2. Implication of the Issue to Regulatory Questions Good.
3. Subissues We have some additional subissues:

e Which design changes should be considered?

e What operational changes are possible?

e How much reduction in accident likelihood or risk do alternatives provide?

i e What are the costs of alternatives?

e What are the possible deleterious side effects?

e What changes are suggested by a review of operating history?

f Since there is a separate class of technical issues that addresses decision-making, n we think that you should delete your last subissue or mention it in Section 1 as a related issue.

1 l

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4. Approach to Resolution -

- Good. In Phase II, on what timescale will these be done? Will the reanalysis involve MELCOR? If so, the tie-in is.important. --

5. Status of Understanding

.I would like to see a concise presentation of SARRP results to date.

- 6. NRC Position This'is pretty good, but I would like to see it even more specific. I do not think

-we should have a separate IDCOR position section. We should indicate what the IDCOR position is and how our position differs. We must show that we have considered the IDCOR position in our deliberations.

RSD:erc 1

e e

i

2.3.1 Design and Operation Changes to Prevent Severe Accidents Including Sabotage Protection

1. Implication of the Issue to Reculatory Ouestions This issue is directly associated with the fourth regulatory question: how can the level of protection for severe accidents be increased? As its name indicates, this issue relates to ways of protecting against severe accidents by the prevention of these accidents. This prevention can occur either by improving the use of existing equipment (e.g. by improved operational reliability, procedures , testing and maintenance) or by providing additional equipment (e.g. dedicated shutdown heat mmoval systems). Of interest here are botih the identification of the various ways of preventing severe accidents and the measurement of the benefit achieved by these ways, individually and in combinations.
2. Subissues Measure of benefit (core melt frequency reduction, risk reduction, improvement in defense-in-depth)

Generic applicability of measured benefit Relative importance of prevention vs. mitigation Benefit already achieved by TMI-fixes Impact of uncertainties poorly understood, unknown sequences (e.g. seismic, sabotage) component, comnon-cause failure data (e.g. human error rates)

Relationship to unresolved safet Decay Heat Removal Requirements)y issues (e.g. USI A-45, Alternate If cost / benefit is about one, are changes mandated or not?

3. Aporoach to Resolution In order to address this issue, three types of data are needed:

(1) prevention options of potential merit; (2) an assessment of the risk from the specific or oeneric plants (including dominant sequences, system models, important systems, failure modes, consequences of specific sequences); and (3) cost infomation on plant modifi-cation options. With this data and measures of associated un-certainties, the core melt frequency or risk reduction ni: tim benefit can be calculated as well as cost-effectiveness value.

In the Severe Accident Risk Reduction Program (SARRP) and with -

input from supporting prograns, such calculations are being mace -

in an iterative manner, consistent with the phases identified in the Severe Accident Researcn Plan (SARRD).

Phase !

Two sets of cost-benefit calculations are being perfonned in the - m SARRP phase I work. .

In the first set:

a relatively broad spectrum of prevention options was identified; six existing PRAs (Reactor Safety Study, RSSMAP) were used -

as the risk assessment base; and very rough cost measures were assessed.

With this supporting data, methods were developed for calculating and displaying risk reduction benefit and cost-benefit, as well as important sensitivities and uncertainties.

The second set of phase I calculations will be using:

a narrowed list of options and combinations (with less promising options screened out);

an expanded base of risk studies for generic classes of plants, using data on accident sequence likelihoods synthesized from

, a broader set of PRAs, and consequence data reflecting up-to-date understandings of the phenomena involved; and more detailed cost estimates, with support from an architect-engineering firm.

With this data the risk reduction and cost-benefit calculations described abov,e will be redone, on a schedule consistent with the mid-84 severe accident commission paper.

Phase II The phase II SARRP evaluation of core melt frequency or risk reduction benefit and cost-benefit of accident prevention options is oriented with the completion of a further evaluation of accident sequence likelihoods (which includes consideration of external events) and with the completion of most of the severe accident experimental programs. Using this new data on accident probabilities and consequences, the cost-benefit, sensitivity, and uncertainty calculations will be redone.

o I e i

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4 Status of Understandinc ,

At this time, the potential risk reduction benefit of prevention. .

options is relatively well understood for a set of specific plants, -

based on the RSS and RSSKAP risk assessments. More robust and generic information is not available because of incomplete study of the competing risks of option installation and use, the costs-of such options, and the more generic extension of these plant-specific results. Many of these issues will be accounted for in the second set of phase I calculations, either by refined calcu-lating or by sensitivity studies. Issues assessed by these sensi-

! tivity studies in phase I will be the focus of phase II work.

5. NRC Position From the calculations made to date, it appears that major modifi-cation to prevent severe accidents (e.g. dedicated shutdown heat removal systems) will be difficult to justify on the basis of quantitative cost-benefit calculations. Combinations of lesser modifications, however, can be expected to be marginally cost-

. effective. In addition, consideration of uncertainties and poorly-quantified sequences (e.g. , seismic events, sabotage),

or less quantitative (probabilistically) methods (e.g. ensuring defense-in-depth) could lead to reconnendations for requiri_ng modifications which are, at best,1 cost effectivermarginally if only quantitative best-estimate analysis was used.

6. IDCOR Position Little is known about the IDCOR analyses at this time. However, ~

general statements have been by IDCOR management that their analyses indicates very low risk from existing LWRs. Because of this assessment and the corollary that no further risk reduction is needed, little quantitative evale6tidn of measures to reduce

  • risk has been made. "'

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