ML20057B366

Requests for Addl Info as Result of Review of June 1992 Application for Design Certification of AP600.Response Should Be Submitted within 90 Days of Ltr Receipt

ML20057B366
Person / Time
Site:	05200003
Issue date:	08/26/1993
From:	Kenyon T Office of Nuclear Reactor Regulation
To:	Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
References
NUDOCS 9309210250
Download: ML20057B366 (4)

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August 26, 1993 Docket No.52-003 i

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Mr. Nicholas J. Liparulo Nuclear Safety and Regulatory Activities Westinghouse Electric Corporation P.O. Box 355 Pittsburgh, Pennsylvania 15230 i

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SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION ON THE AP600 As a result of its review of the June 1992 application for design certification of the AP600, the staff has determined that it needs additional information in order to complete its review. The additional information is i

needed in the area of probabilistic risk assessment (720.261).

Enclosed is l

the staff's question.

Please respond to this request within 90 days of the date of receipt of this letter.

i You have requested that portions of the information submitted in the June 1992 l

application for design certification be exempt from mandatory public disclosure. 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 -

submitted information is being withheld from public disclosure pending the staff's final determination. The staff concludes that this request for-additional information does not contain those portions of the information for j

which exemption is sought.. However, the staff will withhold this letter from i

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 l

that time, you do not request that all or portions of the information in the J

enclosures be withheld from public disclosure in accordance with 10 CFR 2.790, this letter will'be placed in the NRC's Public Document Room.

1 This request for additional information affects nine or fewer respondents, and L

therefore, is not subject to review by-the Office of Management and Budget -

under P.L.96-511.

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• The numbers in parentheses designate the tracking numbers assigned to.

3 the questions.

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B C R E M M W Y.c 11 9309210250 930826 PDR ADOCK 05200003, m

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Mr. Nicholas J. Liparulo August 26, 1993 If you have any questions regarding this matter, you can contact me at (301) 504-1120.

Sincerely, l

(Original signed by F. Hasselberg for)

Thomas J. Kenyon, Project Manager Standardization Project Directorate Associate Directorate for Advanced Reactors and License Renewal Office of Nuclear Reactor Regulation i

Enclosure:

As stated cc w/ enclosure:

See next page DISTRIBUTION:

• Central File PDST R/F TMurley/FMiraglia DCrutchfield

• PDR RBorchardt TEssig TKenyon FHasselberg TGody, Jr., ED0 JMoore, 15B18.

HSiemien, 15B18 PShea Alevin, 8E23 ACRS (11) w/o encl.

WTravers MPohida, 10E4 RPall a, 10E4 AEl-Bassioni,10E4 GSuh (2), 12E4 1

0FC LA:PDST:ADAR PM:PDST:ADAR PM:PDST:ADAR SC:PDST:ADAR NAME PShea piD$

TKenyon b h FHasselberg M TEssig (k -

DATE 08/hl/9b 08/th/93 08/24/93 08/t4/93 0FFICIAL RECORD COPY: AP600RAI.TK 1

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

Mr. B. A. McIntyre Advanced Plant Safety & Licensing Westinghouse Electric Corporation Energy Systems Business Unit P.O. Box 355 Pittsburgh, Pennsylvania 15230 i

Mr. John C. Butler Advanced Plant Safety & Licensing Westinghouse Electric Corporation Energy Systems Business Unit Box 355 Pittsburgh, Pennsylvania 15230 Mr. M. D. Beaumont Nuclear and Advanced Technology Division Westinghouse Electric Corporation One Montrose Metro 11921 Rockville Pike Suite 350 Rockville, Maryland 20852 1

Mr. Sterling Franks U.S. Department of Energy NE-42 Washington, D.C.

20585 Mr. S. M. Modro EG&G Idaho Inc.

Post Office Box 1625 Idaho Falls, Idaho 83415 Mr. Steve Goldberg Budget Examiner 725 17th Street, N.W.

i Room 8002 Washington, D.C.

20503 Mr. Frank A. Ross U.S. Department of Energy, NE-42 Office of LWR Safety and Technology 19901 Germantown Road.

Germantown, Maryland 20874 l

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REQUEST FOR ADDITIONAL INFORMATION ON THE WESTINGHOUSE AP600 DESIGN PROBABILISTIC RISK ASSESSMENT 720.261 address the following concerns related to pressurizer safety valve operation:

a.

Based on the PRA, it appears that the pressurizer safety valve will lift following a turbine trip.

Failure of such valves to reseat has been the source of several events in operating plants.

Confirm and t

justify the value used in the PRA for (1) the probability of the valve to lift, and (2) the probability of the valve to reseat.

b.

It is the staff's understanding that the I&C system is able to distinguish between a safety valve lifting and a LOCA, so that the ADS is not unnecessarily actuated.

Explain how the I&C logic responds to (1) a safety valve opening and reseating, and (2) a safety valve opening and failing to reseat. Describe any protection logic that would prevent spurious ADS actuation.

c.

Discuss whether and how safety valve setpoint miscalibration or drift (e.g., due to loosening of bolts, or changes in spring tension or temperature) could affect I&C initiation of an SI signal, recognizing that safety valve actuation would cause a temporary loss of pressurizer level information.

(The pressurizer level indication would appear to be higher that the actual level while the valve is open.)

d.

In view of the potential for safety valves to fail to reclose, explain what considerations were given to trying to reduce the frequency of safety valves lifting during transients, such as turbine trips, as part of the AP600 design process.

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Enclosure

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