ML20198L234

Forwards Documentation of AP600 Informal Correspondence to W Re Shutdown Probabilistic Risk Assessment & Severe Accident Issues

ML20198L234
Person / Time
Site:	05200003
Issue date:	01/07/1998
From:	Joseph Sebrosky NRC (Affiliation Not Assigned)
To:	NRC (Affiliation Not Assigned)
Shared Package
ML20198L239	List: ML20198L234 ML20198L256
References
NUDOCS 9801150205
Download: ML20198L234 (7)

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,f g* January 7,1998 APPLICANT: Westinghouse Electric Corporation PROJECT: AP600

SUBJECT:

DOCUMENTATION OF AP600 INFORMAL. CORRESPONDENCE TO WESTINGHOUSE CONCERNING SHUTDOWN PROBABil.lSTIC RISK ASSESSMENT (PRA) AND SEVERE ACCIDENT ISSUES On September 30,1997, and October 16,1997, the staff provided Westinghouse with the e questions in Attachment 1 and 2 respectiv ely. Westinghouse responded to this information informally. Their responses to tho issues can be found la Attachment 3 and 4 respectively.

Subsequent to this information transfer the staff has determined the questions that need to be answered for the final saftty evaluation report (FSER). These questions were sent to Westinghouse in a November 7,1997, letter. The staff considers allissues in Attachment 1 and 2 resolved with the exception of the issues that are identified in the November 7,1997, letter. The November 7,1997, items ?ppear in the open item tracking system (OITS'.f Therefore, no additionalitems from attachment 1 or 2 need to be added to the OITS.

Attachment 5 contains information that was sent to Westinghouse on December 10,1997, concerning what the staff believed were l% functional requirements that needed to be incorporated into the Inspections, Tests, Analyses, and Acceptance Criteria (ITAAC) for the reactor vesselinsulation design. The resolution of this issue will be documented in the ITAAC and will be %cked under the corresponding FSER open item number in OITS. Attachment 6 contains information that was sent to Westinghouse on December 19,1997, concerning Westinghouse's response to severe accident open items. The resolution of these questions will be tracked with the corresponding FSER open item number in the OITS.

original signed by:

Joseph M. Sebrosky, Project Manager Standardization Project Directorate Division of Reactor Program Management Office of Nuclear Reactor Regulation Docket No.52-003 Attachments: As stated )

cc w/atts: See next page DISTRIEL)JJQ.[f i See next page g i

DOCUMENT NAME: A:\FA(PRA. SUM To receive a copy of this document, Indicate in the box: *C"

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waswewetow, o.c. seeewem January 7. 1998 APPLICANT: Westinghouse Electric Corporation PROJECT: AP600

SUBJECT:

DOCUMENTATION OF AP600 INFORMAL CORRESPONDENCE TO WESTINGHOUSE CONCERNING SHUTDOWN PROBASILISTIC RISK A68ESSMENT (PRA) AND SEVERE ACCIDENT ISSUES On September 30,1997, and October 16,1997, the staff provided Westinghouse with the questions lil Attachment 1 and 2 respectively. Westinghouse responded to this information Informally. Their responses to the issues can be found in Attachment 3 and 4 respectively.

Subsequent to this information transfer the staff has determined the questions that need to be answered for the nnel safety evaluation report (FSER). These questions were sent to Westinghouse in a November 7,1997, letter. The staff considers allissues in Attachment i and 2 resolved whh the exception of the issues that are identified in the November 7,1997,

~ letter. The November 7,1997, Hems appear in the open hem tracking system (OITS). Therefore, no additional hems from attachment 1 or 2 nood to be added to the OITS.

Attachment 5 contains information that was sent to Westinghouse on December 10,1997, concerning what the staff believed were the functional requirements that needed to be incorporated into the inspections, Tests, Analyses, and Acceptance Criteria (ITAAC) for the l

reactor vesselinsulation design. The resolution of this issue will be documented in the ITAAC and will be tracked under the corresponding FSER open item number in OITS. Attachment 6 contains information th41 was sont to

• Vestinghouse on December 19,1997, concoming Westinghowe's respon6e to severe accident open items. The resolution of these questions will be tracked with the corresponding FSER open item nu bor in the OITS.

jJ eph M. Sobrosky, Pr et Manager s Standardization Project Directorate Division of Reactor Program Management Office of Nuclear Reactor Regulation Docket No.52-003 Attachments: As statwd cc w/atts: See n9xt page -

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Westinghouse Electdc Corporation Docket No. 52 003 l i

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oc: Mr. Nicholas J. Liparuto, Manspor Mr. Frank A. Ross  !

Nuclear Safety and Repuistory Analysis U.S. Department of Energy, NE-42 l 4

Nucear and Advanced Technology Division Offloe of LWR Safety and Technology i Westinghouse Electric Corporation 19901 Germantown Road l P.O. Box 355 - Germantown, MD 20074  :

PMtsburgh, PA 15230 l Mr. Russ Bell i Mr. B. A. McIntyre Senior Project Manager, Programs ,

Advanood Plant Safety & Lloonsing Nuclear Energy institute  !

Westinghouse Electric Corporation 1776 i Street, NW  !

Energy Systems Busines6 UnN SuNe300 t Box 365 Washingten, DC 20006 3708 l PWtaburgh, PA 15230  :

Ms. Lynn Connor  !

Ms. Cindy L. Haag Doc Soarch Associates ,

Advanced Plant Safety & Licensing Post Office Box 34 Westinghouse Electric Corporation Cabin John, MD 20818  ;

Energy Systems Business UnN  ;

Box 355 Dr. Craig D. Sawyer, Manager Pittsburgh, PA 15230 Advanced Reactor Prcyems  ;

GE N# ear Energy l Mr. M. D. Beaumord 175 Curtner Avenue, MC 754 Nuclear and Advanced Technology Division San Joe, CA 95125 Westinghouse Electate Corporation One Montrose Metro Mr. Rober1 H. Suchheir 11921 Rockvil6e Pike GE Nuclear Energy  ;

Suite 350 175 Curtner Avenue. MC 781 ,

Rockvil64, MD 20852 San Jose, CA 95125  !

Mr. Storiing Franks Barton Z. Cowan, Esq. .;

U.S. Department of Energy Eckert Seamans Cherin & Mellott ,

NE50 600 Grant Street 42nd Floor i 19901 Germantown Road Pittsburgh, PA 15219 ,

Germantown, MD 20074 Mr. Ed Rodwell, Mana9er  :

Mr. Cheries Thompson, Nuclear Engineer PWR Design Certificatien  !

AP600 Certification Electric Power Research Instituto NE50 3412 Hillview Avenue  !

- 19901 Germantown Road Palo Aho, CA 94303 Germantown, MD 20874 4

, Mr. Robert Malers, P.E.-

Pennsylvania Department of

- Environmental Protection Bureau of Radiation Protection <

- Hachel Carson State Offlos Building P.O. Box 6469 Harrisburg, PA 17105-6469.

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Dl8TRIBUTION w/ attachments:

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Comments sent to Westinghouse on September 30,1997 Regarding the Shutdown PRA

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1. Based on item 1 of attachment 6 of the Sept 9mber 18th letter, we requested Westinghouse f to generate a revised shutJown CDF, a revised list of dominant cutsets, and revised  ;

importance analyses assuming the AP600 design changes assumed in Attachment 54A of the shutdown PRA and the new success criteria (incorporation of 4th stage ADS valves to preclude surge line flooding). As I look at the revised CDF estimate (case 1) dated .

September 26,1997, common cause failure of the IRWST MOVs appears in the second largest cutset. There are no IRWST squibs appearing in the dominant cutsets as in Appendix 54A.

2. Based on item 4 of attachment 6 of the September 18th letter, we requested Westinghouse to generated a revised shutdown CDF assuming minimal compliance with TS which assumes: 1 out of 2 IRWST gravity injection paths are inoperable,2 out of 4 ADS valves are inoperable, and RNS V 23 is inoperable. Instead, in case 3 (the TS case), RNS V 23 is credited, and it appears in the top cutset.

Attachment 1

P Comments sont to Westinghouse on October 18,1997, Concerning the Ootober 8,1997 Version of the Shutdown PRA TOPICS FOR DISCUSSION WITH WESTINGHOUSE [

SUCCESS CRITERIA ISSUES In Chapter 54 of the shutdown PRA, W reported that

• recirculation is not required within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> after gravity injection. Given 4th stege ADS actuation .

is required during reduced inventory conditions, W la requested to determine when recirculation  !

could be initiated.

REPORTING ISSUES j

1. The PRA resuHs confeined in Section 6.1 of the Shutdown Evaluation Report need to be  !

corrected because they are based on en old version of the shutdown PRA that excludes 4th stage ADS actuation during reduced inventory conditions.

2. The PRA results contained in Chapter 5g of the PRA need to be corrected for the same '

reason discussed above.  ;

3. Attachment 54B needs to document that this attachment contains a re quantification of the baseline and focused shutdown PRA. Given this new success criteria change, W should  ;

clearly document that the results of Attachment 548 should be used to derive insights as

^

opposed to the results reported in Attachment 54A or Chapter 54. -

4. The results given in 548.1.1 need to be identified as the Baseline Shutdown PRA CDF. It is not a sensitivity study. The results given in 54.b.1.2 need to be identified as the base line Focused Shutdown PRA CDF.

5. Two new ADS fault trees were constructed. The success criteria summary tables for these fault trees were provided in the package. However, the fault trees were not submitted. The etaff requests Westinghouse to provide the fault trees and a description of the basic events.

6. The description (on page 5 of Attachment B) of how the CCF failure estimates were derived is unclear. According to chapter 5g (page 2g 11), for sensitivity case 3, ADX EV SA should be 5.8E-4 * .1 = 5.8E 5. Westinghouse needs to document how the failure rate for the IWX MV G01 was estimated. Based on Chapter 5g,it appears that IWX MV G01 should be 5 8E-4 * .15 5.8E 5 Westinghouse needs to document how the IWX-CV AO was estimated. Based on the full power PRA, IWX CV AO should be 5.1E 5 per demand.

7. Westinghouse needs to document in $4B whether the truncation limits used for the baseline shutdown PRA and the focused shutdown PRA estimates reported in 54.B.1 were also used for the revision 6 of the shutdown PRA.

Attachment 2

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8. Westinghouse needs to document in Section M.b.2 that gravity ir#ction now requires IRC and power to operate during safe shutdown. Westinghouse needs to document in Section 54.5.2 why H is acceptable not to model this new dependency.

9. Westinghouse needs to document in Section 54.5. 2 that litWST MOVs 121A and B are no longer required to isolate the IRWST and operate to provide IRWST when called upon.

Squib valves 123a/b and 125/ab are now required to provide IRWST injection when called upon.

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