ML16342E041
| ML16342E041 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 03/27/1998 |
| From: | Steven Bloom NRC (Affiliation Not Assigned) |
| To: | Rueger G PACIFIC GAS & ELECTRIC CO. |
| References | |
| TAC-M99237, TAC-M99238, NUDOCS 9804020105 | |
| Download: ML16342E041 (8) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSlON WASHINGTON, D.C. 20555-0001 Harch 27, 1998
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Mr. Gregory M. Rueger, Senior Vice President and General Manager Pacific Gas and Electric Company Nuclear Power Generation N9B P. O. Box 770000 San Francisco, California 94177
SUBJECT:
REQUEST FOR ADDITIONALINFORMATION-ECCS MANUALAND AUTOMATICSWAPOVER (TAC NOS. M99237 AND M99238)
Dear Mr. Rueger:
By letter dated April7, 1997, Pacific Gas and Electric Company (PG8 E), submitted Final Safety Analysis Report (FSAR) update pages to close an open issue on Diablo Canyon regarding ECCS swapover.
The issue was raised in NRC Inspection Reports (IR) 96-21, dated December 4, 1996, and IR 96-24, dated February 26, 1997. The issue originated in the NRC Safety Evaluation Report (SER) for Diablo Canyon dated October 16, 1974.
In the SER, the staff stated that manual switchover of the residual heat removal (RHR) pump suction from the refueling water storage tank (RWST) to the containment sump was accepted.
The staff further stated that the switchover should be fullyautomated in the longer term to reduce operator manual actions needed subsequent to a loss-of-coolant accident (LOCA).
Since the original SER was written, the staff issued NUREG-0933, Rev. 3, "APrioritization for Generic Safety Issues," dated December 31, 1995, in which the staff stated generically that installation of a fullyautomatic ECCS swapover system was not justified on a cost/benefit basis and stated that the issue was to be resolved with no new requirements.
Recently the licensee discovered that the procedure for manual swapover at the plant was not adequate since the required volumetric margin in the RWST might not be met. This was reported in Licensee Event Report (LER) 1-97-002 on March 28, 1997.
The licensee revised the manual ECCS swapover procedure to ensure that 32,500 gallon margin remained in the RWST upon completion of the swapover.
The revised procedure and associated FSAR update pages were sent in for staff review in the April7, 1997, letter.
Although the licensee requested our review and approval based on the availability of the 32,500 gallon margin at the end of the swapover, they did not inform the NRC how the margin was calculated.
We understand that credit was taken for time dependent flow in the various ECCS VB04020i05 980327 PDR ADCICK 05000275 P
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Mr. Gregory M. Rueger March 27, 1998 systems by the details were not provided.
In order to complete our review, our request for additional information is attached.
Please submit your response within 60 days of receipt of this letter.
Sincerely, Original Signed By Steven D. Bloom, Project Manager Project Directorate IV-2 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket Nos. 50-275 and 50-323
Enclosure:
Request for Additional cc w/encl: See next page I.
Information MIMta Docket
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Document Name:
DC99237.rai OFC NAME PDIV-2 loom PDIV-2 EPeyto DATE 3/2 I/98 3 6&98 OFFICIAL RECORD COPY
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Mr. Gregory M. Rueger March 27, 1998 cc w/encl:
NRC Resident Inspector Diablo Canyon Nuclear Power Plant
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cjo U.S. Nuclear Regulatory Commission P. O. Box369
'vila Beach, California 93424 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Harris Tower & Pavillion 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Dr. Richard Ferguson, Energy Chair Sierra Club California 1100 11th Street, Suite 311 Sacramento, California 95814 Christopher J. Warner, Esq.
Pacific Gas & Electric Company Post Office Box 7442 San Francisco, California 94120 Ms. Nancy Culver San Luis Obispo Mothers for Peace P. O. Box 164 Pismo Beach, California 93448 Mr. Robert P. Powers Vice President and Plant Manager Diablo Canyon Nuclear Power Plant P. O. Box 56 Avila Beach, California 93424 Chairman San Luis Obispo County Board of Supervisors Room 370 County Government Center San Luis Obispo, California 93408 Telegram-Tribune ATTN: Managing Editor 1321 Johnson Avenue P.O. Box 112 San Luis Obispo, California 93406 Mr. Truman Burns Mr. Robert Kinosian California Public Utilities Commission 505 Van Ness, Room 4102 San Francisco, California 94102 Mr. Steve Hsu Radiologic Health Branch State Department of Health Services Post Office Box 942732 Sacramento, California 94232 Diablo Canyon Independent Safety Committee ATTN: Robert R. Wellington, Esq.
Legal Counsel 857 Cass Street, Suite D Monterey, California 93940
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RE UEST FOR ADDITIONALINFORMATION ECCS MANUALAND AUTOMATICSWAPOVE PACIFIC GAS AND ELECTRIC COMPANY DIABLOCANYON POWER PLANT UNITS 1 AND 2
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DOCKET NOS. 50-275 AND 50-32 Draft FSAR page 6.3-5 states: "The changeover sequence can be completed, with single failure, and the remaining useable RWST volume exceeds the licensing basis of 32,500 gallons." Based on the times and flow rates given in draft Table 6.3-5, the staff is unable to verify that the volume of water that you state will be available in the RWST at the end of the swapover procedure willindeed be present.
Please provide detailed accounting of all flows leaving the RWST during the post LOCA injection and during performance of manual swapover to justify that the stated margin of 32,500 gallons will remain. Ifcredit is taken for the effect of elevated reactor system pressure or containment pressure in reducing pumped flowfrom the RWST justify that these pressures are calculated to be conservatively low for this purpose.
2.
FSAR paragraph 6.2.2.2 describing the containment spray system states: "Following a LOCA, water from the RWST is used for containment spray.
Later water circulated from the containment sump supplies the spray pumps." Draft Table 6.3-5 states that the containment spray pumps are stopped after receipt of a low-.low level alarm in the RWST and the spray header is supplied by pump RHR-P1 rather than the containment spray pumps.
Please explain this apparent discrepancy.
3.
Action statements regarding sump-to-RHR-pump valves 8982A and 8982B in draft Table 6.3-5 appear to be in error.
The April 7, 1997, letter revised the manual ECCS switchover procedure to ensure that 120,650 gallons of water volume with a 32,500 gallon margin will be available in the RWST for the successful completion of manual switchover to cold leg recirculation. The worst case minimum water inventory available in the RWST between the low-low level and empty level setpoints should be more than the stated required amount ofwater.
Therefore, the licensee should use the total instrument loop uncertainty (TILU)from the sensor to the bistable output for calculating the minimum available water between the "Iow-low"alarm and "empty" alarm setpoints.
Please provide the TILUcalculation methodology that was used in deriving the worst minimum water available in the RWST.
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