ML20214F510

Forwards List of Questions Re Plant Pra,Per 850512 Telcon. Statement of Work, Review of PRA for Seabrook Nuclear Power Plant, Encl

ML20214F510
Person / Time
Site:	Seabrook, 05000000
Issue date:	03/13/1985
From:	Khatibrahbar BROOKHAVEN NATIONAL LABORATORY
To:	Lyon W Office of Nuclear Reactor Regulation
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FOIA-87-6 NUDOCS 8705260124
Download: ML20214F510 (8)

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9 b BRO.JKHAVEN hnh0NAL lABOi.n,Oii r' ASSOCIATED UNIVERSITIES, INC.

(l(ll Upton. Long Island New York 11973 Depoiment of Nucleo Energy (516) 282' 2626 FTS 666' If 'W March 13, 1985 Mr. Warren t. yon

\f Reactor Systems Branch Division of Systems Integration U.S. Nuclear Regulatory Commission Mail Stop P-1132 Washington, D. C. 20555 g

Dear Warren,

Pursuant to our telepSone conversation yesterday. enclosed please find a list of questions related to the Seabrook PRA.

If you have any questions, please don't hesitate to call me.

Sincer ely ,

M Nhsen Khatib-Rahbar Accident Analysis Group MKR:tr Encl.

cc: W. Y. Kato (w/ enclosure)

R. A. Bari " "

W. T. Pratt l~t 1 /) - 8 7 - 00 5 8705260124 870515 PDR FO!A PDR U/1 SHOLLYU7-6 j '$'l

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! Questions Related to Seabrook PRA

' i M. Khatib-Rahbar H. Ludewig, A. Agrawal, and W. T. Pratt l

. 1. What is the reason for the low frequency of occurrence for Steam Generator ,

Tube Rupture (SGTR) plant damage states?

p er g g p - _y

2. The frequencies of occurrence for plant damage states SE and TE are about l

an order of magnitude higher for Seabrook-1 as compared to Zion and Mill-  :

stone-3 plants. Why? l

3. For the case of pump seal leakage, the applicant assumes leak rates of 20 i

)

a gpm/ pump for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> and 300 gpm/ pump thereaf ter. What is the rationale

! behind these leak rates? f 1,

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4. How realistic are the Seabrook source terms as compared to the BMI-2104- '

1 based results? (Specifically,thecore/concreteinteractioninadry i cavity situation.) ,

j 5. Using the BMI-2104 methodology, one can show that the choice for some of ,

the OPD's is unrealistic. What are the implications?

! 6. The long release time for T6V, TE7, and associated source terms imply an

! exten.e4 core / concrete interaction time. Using WASH-1400 methods this j phase of the release is limited to two hours. How should one resolve this  ;

I seemingly contradictory timing and source terms? f i

j 7. What is the applicability of the recent test results on containment failure characteristics performed at Sandia National Laboratory to the Seabrook containment?

i r 8. It has become apparent from the review that the contribution to risk from leakage before gross failure of the containment is insignificant. Further.

more, the PRA clearly demonstrates that the risk dominant release cate-  !

gories T2V and T3V result from the gross failure of the containment build.  ;

ing. Therefore, what is the benefit of this approach? l l 9. The C-matrix for Seabrook-1 is in general agreement with other recently re-j viewed PRA's. However, the late overpressurization release category for  ;

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Seabrook is about 60% of the total core melt frequency as compared to only

- a very small fraction in the case of Zion. Why is this so (see Q.2 above)?

10. What are the plant damage frequencies for the internal events only?  !

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Enclosure STATEMENT OF WORK

Title:

Review of the Probabilistic Risk Assessment for the Seabrook Nuclear Power Plant f FIN No.: A3778 B&R No.: 20-19-40-41-3 NRC Project Manager: WarrenC.Lyon(FTS 492-9405)

BACKGROUND '

The Reactor Systems Branch (RSB) has the responsibility to assist the Reliability and Risk Assessment Branch (RRAB) within the Office of 4

Nuclear Reactor Regulation (NRR) in review of Probabilistic Risk Assess-r,ents (PRAs) submitted to NRC by license Applicants and licensees. A PRA ha: heen submitted to NRC by Public Service Company of New Hamp-shire, an operating license applicant, pertaining to the Seabrook i

Nuclear Power Plant.

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OBJECTIVE The objective of the present task is to provide a limited review of those aspects of the Seabrook PRA leading to estimates of risk corres-2 I

ponding to various plant damage states to determine the accuracy of the estimates. The investigation will be directed toward differences between phenomenological behavior of the Seabrook plant and other largo dry containment plants such as Zion and Indian Point. In addition, unique features of the Seabrook PRA will be audited.

WORK REQUIREMENTS i

Perform a limited review and evaluation of the risk assessment submitted by the 1 gansee for the Seabrook PWR power plant to determine if esti-mates plant / of siteaisk reflect appropriate use of risk assessment methods and information. Compare the Seabrook containment and other

! severe accident mitigation features to those at Zion and Indian Point.

Since the review is te be limited, maximum utilization will be made of results from evaluation of other large dry containment plant PRAs, and emphasis Seabrook PRA.

will be placed on differences between those plant FRAs and the I

The defensibility of the licensee's submittal of the risk and associated uncertainty spread with respect to (1) use of state of-the-art risk 4

i assessment methods. (2) thoroughness and comprehensiv ing assumptions, will be considered, fgA - 8 7-ot'6 D//

The review will focus on the calculation of risk given the frequencies of the plant damage states, including methodology, assumptions, data, information sources, models, plant understanding, completeness of the analysis, and any other area which could affect the quantitative or qualitative results. A limited sensitivity analysis will take alterna-tives identified in the review in appropriate combinations and determine the incremental change in risk resulting from the use of alternatives in the dominant sequence. In general, these alternatives should be eval-uated by performing separate effects /phenomenological calculations within the overall analysis.

The work to be performed in accord with this Statement of Work is to be based in part upon the " front-end' work to be performed by the Lawrence Livermore National Laboratory under NRR/ DST funding (FIN No. A-3754-4),

and is to be fully coordinated with that effort.

The work described herein consists of one task which is divided into several parts to be consistent with the A-3754-4 effort. These are:

1. Evaluation of Risk Due to Internal Events

2. Evaluation of Risk Due to External Events

3. Draf t Final Reports 4 Final Reports

5. Questions to Licensee Each item is discussed below.

Contract Task: Perfom "Back-end" evaluation of the Seabrook PRA.

Estimated level of effort FY 84 0.4 staff years FY 85 0.3 staff years Estimated completion date: Aug. 30,1985 The following items are to be accomplished to complete the contract task:

(1) Evaluation of Risk Due to Internal Events (a) Perform a limited review and evaluation of the scope, assump-tions, and systems analysis aspects of risk due to internal event plant damage states, and other items identified as a result of the initiating events review and provided to BNL by the NRC Program Manager.

(b) Compare such items as risk, methodology, assumptions, data, information sources, models, plant understanding, completeness of the analysis, and other areas which could affect the results. Provide a compilation cf significant similarities and differences.

1 (c) Develop a table of assumptions used in the analysis and make a finding on the validity.

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(d) Identify omissions and deficiencies in the pnenonenological

, analysis and estimate the impact where reasonable, considering the scope and depth of the Task effort. Include the technical basis for these estimates.

(e) Incorporate NRR technical review coments as provided by the NRC Program Manager.

(f) Perfonn a limited assessment of the uncertainty analysis.

Consider propagation and completeness in treatment of uncer-tainty, data uncertainty, and modeling sensitivity / uncertainty.

(g) Maintain close contact with Lawrence Livermore National Laboratory in regard to the front-end analyses which serve as the starting point for the above work.

(2) Evaluation of Risk Due to External Events (a) Perform a limited review of each type of external event considered and concur with or modify the risk information for each plant damage state which is significantly affected by the review.

(b) Review and evaluate assumotions of the external events risk analysis.

(c) Identify omissions and deficiencies in the external event risk l

analysis, and estimate the impact where practical with respect to the effort funded under this task. For omissions and deficiencies for which evaluation is believed to be beyond the state-of-the-art, provide a list and the basis for this belief.

(d) Assess the uncertainty analysis. Examine propagation and completeness in treatment of uncertainty, data uncertainty, and modeling sensitivity / uncertainty.

(c) Maintain close contact with Lawrence Livermore Laboratories in regard to the front end analyses which serve as the starting point for the item (2) work.

(3) Draft Reports A Draft Report is to be provided which covers the effort accomp-lished in FYS4 and a second Draft Report is to be provided which covers the effort accomplished in this program. The reports are to include, at a minimum, the following:

(a) for each of the PRA areas reviewed, define the basis for acceptability and describe what was considered in the review.

The findings will include selected reestimates of risk infor-mation corresponding to plant damage states, identification of areas which were not pursued, and identification of grey areas where sensitivity studies might be used to bound a central estimate.

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(b) Describe areas of incompleteness determined in the review.

l Quantify, where consistent with the funded depth of the I review, the potential impact of these areas. Discuss the basis for quantification values.

l

) (c) Based on reviewer audits, discuss the accuracy, uncertainty, I and adequacy of the PRA author's risk quantification$,

l (d) An approximate outline of the reports is given below:

I $

1. Sumary

2. Introduction

2.1 Background

2.2 Scope 2.3 Assumptions

3. Internal Events Risk 4 External Events Risk

5. Sumary and Conclusions 5.1 Dominant Risks Corresponding to Each Plant Damage State

. 5.2 Important Problems and Omissions l 5.3 Treatment of Uncertainties l 5.4 Overall Evaluation of Seabrook Risk Assessment l 6. Appendices (asrequired)

This outline is similar to the outline to be followed by Lawrence Livermore in their accomplishment of FIN A-3754-4. Although the BNL and Lawrence Livernere reports are to be " stand alone" reports, the contents are to be coorcinateo so that complete coverage of the technical tcpic is providec if one has both the BNL and the Lawrence Livermore reports.

(4) Final Reports The final reports will take into account pertinent comments on the craf t final reports by NRC and other interested parties. They will be published as NUREG/CR reports. The first final report is to be provided by November 30, 1984; and the second. which covers the entire program, is to be providec by August 30, 1985, (5) Questions to Licensee Provide questions for forwarding to the licensee covering all aspects of the analysis on a schedule that is to be mutually agreeable between BNL and the NRC Project Manager.

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LEVEL Or EFFORT AND PERIOD OF PERFORMANCE Tne estimatec level ef effort is 0.7 professional staff years with the effort te be completec by August 30, 1985.

TECHNICAL REPORTING REOUIREMENTS:

All technical products which are required from this contract have been identi-i fied specifically in the above discussion. BNL shall submit six copies of draf val. t NUREG/CR reports to the NRC Project Manager, for staf f review and appro-For NUREG/CR reports, within sixty days of receipt of the staff's comments on these reports, the contractor shall submit one (1) reproducible and six (6) reproouced copies of the final reports in accordance with NRC Manual Chapter 3202.

by NRC " Publication Contractors."of Unclassified Regulatory and Technical Reports Prepared BUSINESS LETTER REPORTS A monthly business letter report will be submitted by the 20th of the month to the NR: Project Manager with copies provided to the Director, Division of Systems Integration, ATTN: S. Boyd, R. W. Houston, 2. Sheron 051, and Mr. L.

Sciancer. NER. These reports will identify the title of the project, the FIN, the Principal ]nvestigator, the period of performance, the reporting perioc ano will contair. 3 sections as follows:

Preject Status Section ,

For each task under this program, provide the following information:

1.

A list of the if missed, anefforts etmpleted explanation during the period; milestones reached, or provided.

2.

Any problems or delays encountered or anticipated and recommendation for resciution. }/

3.

A summaryfor completion cf progress each task).to date (this may be expressed in terms of percentage

4. Plans for the next reporting period.

1/ If the recommenced resciution involves a contract modification, i.e. ,

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changes work recuirements, level cf ef fort (costs), or period of performance, a separate letter should be prepared and submitted to the Director, Division of Systems Integration, ATTN: S. Boyd, and a copy provided to the Project Manager and L. Solander, NRF.

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• Finan:::ai Status Section

1. Provide the total cost (value) of the project as reflectec in the proposal and tne total amount of funds obligated to date, i 2. Provide tne total amount of f uncs expencec (costed) during the period and total cumulative te cate as follows:

l -- .

l Period Cumulative

a. Labor-related costs

b. Computer services I c. Travei

c. Subcontracts

e. Equipment Total ( %) 2/

3. Fee Recoverv Cost Status Section l

, Pursuant to the provisions of NRC Regulations,10 CFR 27C, provide the I total amount of funcs expended (costed) during the period and cumulative l to date for each task in the f ollowinc format:

l FIN: A3776 ,

TI1 LE: Review of the Probabilistic Risk Assessment for the Seabrook huclear Power Flant PERIOD:

Docket costs facility Name Number Ferioc Cumulative Seabrook 50 443 MEETINGS AND TRAVEL The contractor may attend a 2 day visit at an unspecified site with the licensee to discuss questions on the analysis and may attend six 1 day rnettings at NRC headquarters in Washington, DC.

Two 3-day visits to the Seabrook site.

NRC FURNISHED MATERIALS ,

The risk stud.v has been transmitted to the contractor. NRC will provide addi-tional information as needed.

2/ Provide percentage against total funds oblicated to date.

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UNIT *f1 STATES

((panog'g ,f 7 NUCLEAR REGU.aTCMY COMMISSION l wasHmotoN o. c. rosss

%...../ AP6101965 1

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) Docket No.: 50-458 a 1 l MEMORANDUM FOR: G rees aheson, Chief

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[

I Reactor Systems Branch i

Division of Systems Integration t

FROM: L. G. Hulman, Chief Accident Evaluation Branch

!g Division of Systems Integration l

SUBJECT:

REVIEW OF SEABROOK PROBABILISTIC SAFETY STUDY We understand that the subject review will not be continued, nor will we be expected to provide source tem evaluations or consequence calculations .

in support of the Seabrook review. We are, however, sumarizing our work l

and findings to date in the discussion provided below in response to the

( J. Rosenthal request for a brief sunut ry.

. We previously gave informal conenents to Warren Lyon on the pr liminary contairment response / source tem rt view report submitted by Brookhaven i

National Laboratories.

l s The rest of our review was restricted to consequence calculation J J methodology. It appeared that the evacuation model in the Seabrook

Probabilistic Safety Study was developed from a reasonable data base.

However, the complexity of the evacuation model and its interaction with l the meteorological model in CRACIT warrants a more lengthy review than was l  ! justifiable (given the cessation of the review). We note, however, that

. impaired evacuation during sumer weekends (because of tourists) that was an issue during licensing, was considered in the consequence analysis. No lM' gross deficiencies in this or other aspects of the consequence calculations were found before the review was teminated.

.. , i T.G.hulmaY, f

. net f, Accident Evaluation Branch i

,9 , ' , . . , ' ' '

dL Division of Systems Integration .

.;yIj,^**J{Q./p '

cc: D. Muller

[v.

R. W. Houston '

J. Rosenthal

, fgr y 27.ce6 i

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