ML16341D145

Informs That 840905 Request That Operation Be Permitted in All Operational Modes W/Power Removed from RHR Sys Suction Valves Unacceptable Because Proposal Does Not Address auto-closure Devices.Info Listed on Encl Requested

ML16341D145
Person / Time
Site:	Diablo Canyon
Issue date:	01/23/1985
From:	Knighton G Office of Nuclear Reactor Regulation
To:	Shiffer J PACIFIC GAS & ELECTRIC CO.
References
NUDOCS 8502110550
Download: ML16341D145 (10)

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,UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, O. C. 20555 JAhl 2g ~g Docket Nos.:

50-275 and 50-323 Mr. J.

D. Shiffer, Vice President Nuclear Power Generation c/o Nuclear Power Generation, Licensing Pacific Gas and Electric Company 77 Beale Street, Room 1451 San Francisco, Cali,fornia 94106

Subject:

RHR. Isolation Valves In a letter dated September 5,

1984 (DLC-94-301), Pacific Gas and Electric Company (PG&E) requested that operation of Diablo Canyon Units 1 and 2 be permitted in all operational modes with power removed from the RHR system suction valves.

The basic concern is the potential inadvertent closure of the valves.

PGEIE has stated that the Unit 1 RHR pumps have actually been damaged as a result of an RHR suction valve closure.

The removal of power from the RHR suction valves was recommended hy Westinq-house Technical Bulletin NSD-TB-77-1 dated July 15, 1977.

The bulletin expressed concern that when the reactor cnolant system pressure is lower than the shutoff pressure of the RHR pumps (approximately 200 psig), inadvertent closure could cause pump damage.

For pressures higher than the shutoff pres-

sure, the pump could operate satisfactorily on bypass flow.

The Westinghouse technical bulletin did not address the effect of inadvertent closure on loss of decay heat removal or low temperature overpressurization.

Should the RCS be in a water solid condition, a 'pressurization would occur due to the loss of letdown flow from the RCS.

Thus, although the RHR pump miqht operate satis-

.factorilyy if inadvertent isolation occurred above 200 psig, undesirable conse-quences might occur.

Based on the information submitted in your letter we are not yet able to conclude that your proposal is acceptable for two reasons.

First, the proposed removal of power from the suction valves alleviates the concern, but does not 50 850i23 5000275 PDR ADOCK 0 P

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1'I address the root cause of the problem, that is, the auto-closure devices.

Second, the proposed removal of power would totally defeat the operator 's ability to rapidly 'isolate the RHR system, should it be necessary.

For example, should a break in the RHR system occur while in Mode 5, valuable time would be lost while returning power to the isolation valves.

We therefore request that you provide the information listed in the enclosure in order for us to complete our evaluation of this issue.

It is our understanding that, in the mean time, power is applied to the valves in accordance with the current, Technical Specifications for Unit I and the same will apply for Unit 2.

In order to expedite the resolution of this issue we are ready to discuss this matter with you in a meeting here in Bethesda at your request.

53 Originai stre '.-. -i:

Gqotgo VJ. Knighton

Enclosure:

As stated cc:

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'George W. Knighton, Chief Licensing Branch No.

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Mr. J.

D. Shiffer, Vice President Nuclear Power Generation c/o Nuclear Power Generation, Licensing Pacific Gas and Electric Company 77 Beale Street, Room 1451 San Francisco, California 94106 Philip A. Crane, Jr.,

Esq.

Pacific Gas 5 Electric Company Post Office Box 7442 San Francisco, California 94120 Mr. Malcolm H. Furbush Vice President - General Counsel Pacific Gas 5 Electric Company Post Office Box 7442 San Francisco, California 94120 Janice E. Kerr, Esq.

California Public Utilities Commission 350 McAllister Street San Francisco, California 94102 Mr. Frederick Eissler, President Scenic Shoreline Preservation Conference, Inc.

4623 More Mesa Drive Santa Barbara, California 93105 Ms. Elizabeth Apfelberg 1415 Cozadero San Luis Obispo, California 93401 Mr. Gordon A. Silver Ms. Sandra A. Silver 1760 Alisal Street San Luis Obispo, California 93401 Harry M. Willis, Esq.

Seymour 5 Willis 601 California Street, Suite 2100 San Francisco, California 94108 Mr. Richard Hubbard MHB Technical Associates Suite K

1725 Hamilton Avenue San Jose, California 95125 Mr.'ohn Marrs, Managing Editor San Luis Obis o Count Tele ram Tribune 13 1 Jo nson Avenue P. 0.

Box 112 San Luis Obispo, California 93406 Diablo Canyon Resident Inspector/Diablo Canyon NPS c/o US Nuclear Regulatory Commission P. 0.

Box 369 Avila Beach, California 93424 Ms.

Raye Fleming 1920 Mattie Road Shell Beach, California 93440 Joel

Reynolds, Esq.

John R. Phillips, Esq.

Center for Law in the Public Interest 10951 West Pico Boulevard Third Floor Los Angeles, California 90064 Mr. Dick Blankenburg Editor 5 Co-Publisher South County Publishing Company P. 0.

Box 460 Arroyo Grande, California 93420 Bruce Norton, Esq.

Norton, Burke, Berry'-5,French, P.C.

202 E.'sborn Road=-

P. 0.

Box 10569 Phoenix,'rizona 85064 Mr.,W.'. -Gangloff, Westinghouse Electric Corporation

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Box 355 Pi'ttsburgh',

Pennsyl.vania, 15230 1

5)avid F. Fle'ischaker, Esq.

P. O.,Box 1178

'klahoma City, -Oklahoma

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Snell 8 Wilmer 3100 Valley Center Phoenix, Arizona 85073 Mr. Lee M. Gustafson, Director Federal Agency Relations Pacific Gas 5 Electric Company 1050 17th Street, N.W.

Suite 1180 Washington, DC 20036 Regional Administrator - Region V

US Nuclear Regulatory Commission 1450 Maria Lane Suite 210 Walnut Creek, California 94596 Michael J. Strumwasser, Esq.

Special Counsel to the Attorney General State of California 3580 Wilshire Boulevard, Suite 800 Los Angeles, California 90010 Mr. Tom Harris Sacremanto Bee 21st and 0 Streets Sacramento, California 95814 Mr. H. Daniel Nix California Energy Commission 1516 9th Street, MS 18 Sacramento, California 95814 Lewis Shollenberger, Esq.

US Nuclear Regulatory Commission Region V

1450 Maria Lane Suite 210 Walnut Creek, California 94596 Mr. Thomas Devine Government Accountability Project Institute for Policy Studies 1901 gue Street, NW Washington, DC 20009

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Enclosure DIABLO CANYON UNITS I AND 2 REQUEST FOR ADDITIONAL INFORMATION In order to complete our evaluation of your request for removal of power from the RHR system suction valves, you should address the following to support a

removal of the auto-closure interlock:

1 1.

Means available to minimize a LOCA outside containment.

2.

Alarms to alert the operator of an improperly positioned RHR isolation valve.

Verification of the-adequacy of RHR relief valve capacity.

Means other than the auto-closure inter locks to ensure both isolation

,valves are closed (e.g., single switch actuating both valves).

5.

Assurance that the open permissive circuitry is neither removed or affected bg, the proposed change.

6.

Assurance that isolation valve position indication will remain available in'the.control room, regardless of the proposed change.

7.

Assessment of the effect of the proposed change on RHR availability, as well-as low temperature ov'erpressure protection.

C The staff is also evalu'ating the 'removal'of the auto-closure interlocks from a regulatory perspective and-wishes to work, with PG8E in arriving at a solution to this problem.

3.

4, The concern raised in the PGSE letter of September 5,

1984 should be addressed by both the industry and the NRC.

The staff required RHR auto-closure interlock was originally intended to minimize Event V concerns, but the effects of the interlock on RHR availability and low temperature overpressurization were not previously known.

Recent studies performed by EPRI (NSAC-52) indicate the need to study in more detail the combined effects of the RHR system auto-closure interlocks.

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