ML16342C075
| ML16342C075 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 10/22/1998 |
| From: | Steven Bloom NRC (Affiliation Not Assigned) |
| To: | Rueger G PACIFIC GAS & ELECTRIC CO. |
| References | |
| GL-97-05, GL-97-5, TAC-MA0462, TAC-MA0463, TAC-MA462, TAC-MA463, NUDOCS 9810290114 | |
| Download: ML16342C075 (6) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055$ 4001 October 22, 1998 Mr. Gregoiy M. Rueger Senior Vice President and General Manager Pacific Gas and Electric Company Diablo Canyon Nuclear Power Plant P. O. Box 3 Avila Beach, CA 93424
SUBJECT:
EVALUATIONOF PACIFIC GAS & ELECTRIC RESPONSE TO NRC GENERIC LETTER 97-05 FOR DIABLOCANYON UNITS 1 AND 2 (TAC NOS. MA0462 AND MA0463)
Dear Mr. Rueger:
The NRC issued Generic Letter (GL) 97-05, "Steam Generator Tube Inspection Techniques,"
on December 17, 1998. The focus of GL 97-05 was to verify that licensee steam generator tube inspection practices were consistent with existing regulatory requirements and plant licensing bases.
Pacific Gas and Electric Company (PG&E), the licensee, submitted a response to this GL on March 17, 1998, as supplemented on September 8, 1998, that included a description and technical basis for all inspection techniques used to size the depth of steam generator tube degradation at Diablo Canyon Nuclear Power Plant, Units 1 and 2.
In these responses, the licensee stated that one tube (R14C64) with a volumetric indication as.
determined from eddy current inspections was currently in-service based on the application of a qualiTied sizing technique for pit indications.
Upon reevaluating the technical basis for concluding that the one indication was a pitting flaw, the licensee determined that it was unable to definitively conclude that the indication in tube R14C64 was, in fact, a pit. Consequently, the licensee stated that it willpreventively repair tube R14C64 in the upcoming refueling outage scheduled for February 1999.
It was also noted that the volumetric indication in tube R14C64 was initiallyidentified in the third refueling outage for Diablo Canyon Unit 1 and no apparent growth (based on eddy current signal amplitude and phase) has been detected for the last five cycles of operation.
The NRC staff has completed its review of the licensee's response to GL 97-05. The NRC staff has concluded that the licensee may have improperly applied a sizing technique qualified for pitting to estimate the depth of a volumetric indication in one tube currently in service in Steam Generator 1-4. As such, the licensee's decision to preventatively plug tube R14C64 at the next refueling outage is appropriate.
Based on Industry experiences with sizing volumetric degradation, the impact on the structural and leakage integrity of steam generator tubing due to this damage, mechanism, and information provided by the licensee concerning the estimated depth and past history for the indication in tube R14C64, there is a low likelihood that the volumetric indication currently in-service could challenge the structural integrity margins of the tube under normal and postulated accident conditions. The NRC staffs review of the GL 97-05
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Mr. Gregory M. Rueger October 22, 1998 responses did not identify any additional concerns with other steam generator tube inspection techniques employed at Diablo Canyon that would indicate the licensee is not in compliance with the current licensing basis for this facility.
Sincerely, l
I Original Signed By Docket Nos. 50-275 and 50-323 cc: See next page
'teven,D. Bloom, Project Manager Project Directorate IV-2
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Mr. Gregory M. Rueger October 22, 1998 CC:
NRC Resident Inspector Diablo Canyon Nuclear Power Plant clo U.S. Nuclear Regulatory Commission P. O. Box 369 Avila Beach, California 93424 Dr. Richard Ferguson, Energy Chair Sierra Club California 1100 11th Street, Suite 311 Sacramento, California 95814 Ms. Nancy Culver San Luis Obispo Mothers for Peace P. O. Box 164 Pismo Beach, California 93448 Chairman San Luis Obispo County Board of Supervisors Room 370 County Government Center
- San Luis Obispo, California 93408 Mr. Truman Burns Mr. Robert Kinosian California Public Utilities Commission 505 Van Ness, Room 41 02 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 ATIN: Robert R. Wellington, Esq.
Legal Counsel 857 Cass Street, Suite D Monterey, California 93940 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Harris Tower 8 Pavillion 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Christopher J. Warner, Esq.
Pacific Gas 8 Electric Company Post Office Box 7442 San Francisco, California 94120 Mr. David H. Oatley, Vice President Diablo Canyon Operations and Plant Manager Diablo Canyon Nuclear Power Plant P.O. Box 3 Avila Beach, California 93424 Telegram-Tribune ATTN: Managing Editor 1321 Johnson Avenue P.O. Box 112 San Luis Obispo, California 93406
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