ML20133G144

Forwards RAI Re AP600 Shutdown Internal Fire Risk Analysis to Support June 1992 Application for Design Certification of AP600

ML20133G144
Person / Time
Site:	05200003
Issue date:	12/02/1996
From:	Joseph Sebrosky NRC (Affiliation Not Assigned)
To:	Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
References
NUDOCS 9701150185
Download: ML20133G144 (5)

Text

. _ _ . _ , .

December.2, 1996 i.

i Mr. Nicholas J. Liparulo, Manager i- Nuclear Safety and Regulatory Analysis j Nuclear and Advanced Technology Division o -Westinghouse' Electric Corporation i

P.O. Box 355 Pittsburgh, Pennsylvania 15230

SUBJECT:

'FOLLOWON QUESTIONS REGARDING THE SHUTDOWN INTERNAL FIRE RISK ANALY-SIS FOR THE AP600.

Dear Mr. Liparulo:

As a result of its review of documentation to support the June 1992 applica- >

tion for design-certification of the AP600, the staff has determined that it needs additional information. Specifically, the enclosed questions concern the shutdown internal fire risk analysis for the~ AP600.

You have requested that portions of the information submitted in'the June 1992 application for design certification be exempt from mandatory public disclo-sure. While the staff has not completed its review of.your request in, .

accordance with the requirements of 10 CFR 2.790, that portion of the submit-ted information is being withheld from public disclosure pending the staff's  :

final determination. The staff concludes that these followon questions do not i contain those portions of the information for which exemption is sought.

However, the staff will withhold this letter from public disclosure for  :

30 calendar days from the date of this letter to allow Westinghouse the opportunity to verify the staff's conclusions. If, after that time, you do not request that all or portions of the information in the enclosures be wi%hald from public disclosure in accordance with 10 CFR 2.790, this letter ,

will be placed in the Nuclear Regulatory Commission's Public Document Room. "

If you have any questions regarding this matter, you can contact me at (301) 415-1132.

Sincerely, original sianed by Joseph M. Sebrosky,: Project Manager Standardization Project Directorate Division of Reactor Program Management Office of Nuclear Reactor Regulation i Docket No.52-003

Enclosure:

As stated

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Mr. Nicholas J. Liparulo Docket No.52-003 Westinghouse Electric Corporation AP600 4

cc: Mr. B. A. McIntyre Mr. John C. Butler Advanced Plant Safety & Licensing Advanced Plant Safety & Licensing Westinghouse Electric Corporation Westinghouse Electric Corporation Energy Systems Business Unit Energy Systems Business Unit P.O. Box 355 Box 355 Pittsburgh, PA 15230 Pittsburgh, PA 15230 Mr. M. D. Beaumont Mr. S. M. Modro 1 Nuclear and Advanced Technology Division Nuclear Systems Analysis Technolog;;s Westinghouse Electric Corporation Lockheed Idaho Technologies Company One Montrose Metro Post Office Box 1625 11921 Rockville Pike Idaho Falls, ID 83415 Suite 350 Rockville, MD 20852 Enclosure to.be distributed to the following addressees after the result of the proprietary evaluation is received from Westinghouse:

Mr. Ronald Simard, Director Ms. Lynn Connor ,

Advanced Reactor Programs D0C-Search Associates J Nuclear. Energy Institute Post Office Box 34 1776 Eye Street, N.W. Cabin John, MD 20818 Suite 300 Washington, DC 20006-3706 Mr. Robert H. Buchholz GE Nuclear Energy Mr. James E. Quinn, Projects Manager 175 Curtner Avenue, MC-781 LMR and SBWR Programs San Jose, CA 95125 GE Nuclear Energy 175 Curtner Avenue, M/C 165 Mr. Sterling Franks San Jose, CA 95125 U.S. Department of Energy NE-50 Barton Z. Cowan, Esq. 19901 Germantown Road Eckert Seamans Cherin & Mellott Germantown, MD 20874 600 Grant Street 42nd Floor Pittsburgh, PA 15219 Mr. Charles Thompson, Nuclear Engineer AP600 Certification Mr. Frank A. Ross NE-50 U.S. Department of Energy, NE-42 19901 Germantown Road Office of LWR Safety and Technology Germantown, MD 20874 19901 Germantown Road Germantown, MD 20874 Mr. Ed Rodwell, Manager PWR Design Certification Electric Power Research Institute 3412 Hillview Avenue Palo Alto, CA 94303

REQUEST FOR ADDITIONAL INFORMATION i

RAIs ON THE AP600 SHUTDOWN INTERNAL FIRE RISK ANALYSIS 720.353 On page 57-38 of the PRA, the PRA states, "the remote shutdown workstation will remain operational during shutdown and will be utilized in the event that conditions make the control room uninhab-i tabl e. " However, TS 3.3.4 states that the Remota Shutdown i

Workstation shall be operable in Modes 1, 2, and 3 only. Histori-cally, licensees have used TS to dictate when equipment can be taken out of service for maintenance. Therefore, the staff is requesting 4

Westinghouse to consider requiring the Remote Shutdown Workstation to be operable during shutdown modes or remove credit for the Remote Shutdown Workstation from the shutdown fire PRA.

i' 720.354 When fire areas are breached during shutdown to support maintenance or testing activities, how are additional compensatory measures like l fire watches controlled (i.e., TS, etc.) to support the 0.01 failure

of a fire barrier?

, 720.355 How will transient combustibles be controlled during shutdown?

720.356 The analysis takes credit for automatic suppression, stating that I compensatory actions are taken when parts of a suppression system are rendered unavailable. The staff is requesting Westinghouse to clarify in the PRA how these actions will be controlled (i.e., TS, administrative controls, etc.)?

720.357 For the safe shutdown analysis, all of the conditional core damage probabilities (CCDPs) are identical (2.6E-8), although the damage states differ. The staff is requesting Westinghouse to explain these results in the fire PRA.

720.358 In the at-power containment analysis, the dominant contribution comes from Fire Zone 1100 AF 11500 (see Table 57-14). The fire leads to damage category CM3, i.e., a medium LOCA, loss of two divisions (A&C) of power and control, and loss of IRWST/recirc train B. The CCDP is 1.2E-2; the scenario frequency is 2.lE-7/yr.

In the safe shutdown analysis, only one division of PXS is lost (see Table 57-24, Sheet 2). The CCDP is 2.6E-8, the CDF is 8.0E-12. The staff is requesting Westinghouse to explain the difference.

720.359 Similar to Question 6, the staff is requesting Westinghouse to explain why the midloop analysis assumes that only one division of power and control is lost due to a fire in Fire Zone 1100 AF 11500 (see Table 57-27, Sheet 2).

720.360 The staff is requesting Westinghouse to explain why the CCDP for containment fire scenarios during midloop that fail only one divi-sion of power and control (e.g., Fire Zone 1100 AF 11300B) have a higher CCDP (SE-4) than fires that fail two divisions of power and control (e.g., Fire Zone 1100 AF 11207), whose CCDP is 2.7E-4.

Enclosure

a .

72d.361 The discussion in the second paragraph of page 57-45 indicates that

the greater importance of midloop fires as compared with safe shutdown fires is due to the increased access required to perform necessary activities. The instantaneous containment fire frequen-cies for both conditions appears to be about the same. (This can be i

seen by dividing the safe shutdown fire frequencies by 0.0715 and the midloop fire frequencies by 0.0177.) The staff is asking Westinghouse to explain this statement in the PRA.

720.362 The staff is asking Westinghouse to document in the shutdown PRA the minimum separation between the cables for the 4 IRWST squib valves in containment.

720.363 For a number of midloop scenarios (e.g., see Fire Areas 1100 AF11206, Table 57-27, Sheet 1 and 1202 AF 05, Table 57-27, Sheet 3),

the scenario frequency is lower than the fire ignition frequency.

, The reduction factor appears to be 0.06, the hot short probability 4

i used elsewhere in the study, although it appears that no hot shorts have been postulated. The staff is requesting Westinghouse to explain the difference.

720.364 In order for the staff to understand the differences between the safe shutdown and midloop fire results, the staff needs the top 100 cutsets for both analyses (such as that provided in Table 57-12 for the at-power results).

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720.365 Based on Section 9A of the SSAR, it is understood that each of the  ;

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' four divisional I&C rooms houses the IPC, ESFAC, PLC,125 Vdc l distribution panel, and 125 Vdc MCC for that division. It appears l 1

that a cable leaving the room provides DC power to each component of i

interest (e.g., a squib valve, an A0V, or an MOV). In order for ,

' this cable to be energized, it further appears that an appropriate contact (in the distribution panel or MCC) must be closed within the room. (This contact receives an actuation signal from an EPO board). It is not clear, therefore, how a fire outside of the room can cause a " hot short" leading to the spurious actuation of a l component. Please explain the mechanism leading to the fire-induced hot shorts postulated to cause spurious opening of the ADS valves.

E

DISTRIBUTION: Letter to Nicholas J. Liparulo. Dated: December 2.1996 j

(* Docket: File

• HOLD FOR 30 DAYS

• PUBLIC PDST R/F TMartin DMatthews TRQuay TKenyon WHuffman JSebrosky DJackson WDean, 0-17 G21 ACRS (11)

JMoore, 0-15 B18 RPalla, 0-8 H7 JFlack, 0-8 H7 MSeimien, OGC EJordan, T-4 D18 GHolahan, 0-8 E2 I NSaltos, 0-10 E4 l MPohida, 0-10 E4 JHolmes, 0-8 D1  !

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MOVENFORCEMENT CONFERENCE Root Causes/Long Term Corrective Actions l l Lack of Management Oversight e Resources o Use of QA i

i

e Training 1

o Closure Review i i

e Program Knowledge RG&E 11/13/%

MOVENFORCEMENT CONFERENCE Root Causes/Long Term Corrective Actions I I Management Oversight Corrective Actions e Individual v Emphasize importance of Design Margins v Counsel in Modification vs Analysis e Independent Verifiers

_ v Training v System Engineer involvement v Key Individual Full Scope Training e Supervisors v Workload Management v Technical Knowledge v Training v Provide Enhancect Tools e Quality Assurance l v Perform Comprehensive MOV Program Audit j v Perform Other Program Audits l

e Management RG&E v Define Program Expectations "'j"

1 MOVENFORCEMENT CONFERENCE Root Causes/Long Term Corrective Actions l 1 t

o Lack of Management Oversight

~

o Lack of Systematic Approach e Program Quality RG&E 11/13/96 31

MOVENFORCEMENT CONFERENCE Root Causes/Long Term Corrective Actions ,

i i Lack of Systematic Approach e Feedback v In-house Testing v Industry Data i

v Research Efforts e Justification of Design inputs e CATS ,

RG&E III I

MOVENFORCEMENT CONFERENCE Root Causes/Long Term Corrective Actions i I Lack of Systematic Approach Corrective Actions e Develop Integrated Database (Smart Book) e Resumption of Industry Forum Participation

! e Broaden Participation in Industry Forums e Modify CATS Procedure RG&F, 11/13/96

MOVENFORCEMENT CONFERENCE Root Causes/Long Term Corrective Actions i i Program Quality e Program Administration e Documentation e Trending e Tools III RG&E

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