ML20148A744
| ML20148A744 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 05/02/1997 |
| From: | Graham P NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NLS970091, NUDOCS 9705090130 | |
| Download: ML20148A744 (3) | |
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NLS970091 May 2,1997 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 Gentlemen:
Subject:
Confirmation of Commitment Cooper Nuclear Station, NRC Docket 50-298, DPR-46 During a conference call (Safety Relief Valves (SRVs),09:00 CDT, April 30,1997), you requested that Nebraska Public Power District (District) confirm on the docket the commitment to a mid-cycle shutdown at Cooper Nuclear Station to ensure SRV performance is meeting Technical Specification limits. This letter confirms the District's commitment to this action.
Data obtained during the previous refueling outage (RE-16) indicated that, after nine (9) months of operation, the four (4) SRVs with new Platinum-Stellite pilot discs all performed within the Proposed CNS Improved Technical Specification (ITS) tolerance of +/- 3%. Three of the SRVs performed within the currem Technical Specification (TS) Safety Setting limits of +/- 1%, with the fourth valve exceeding the TS setpoint by +2.4%.
Data obtained during the current refueling outage (RE-17) indicates that three of the four valves with Platinum-Stellite discs and with service times ranging from fifteen to twenty-four months exceeded the TS setpoint by less than +4.0%. The fourth SRV with a Platinum-Stellite disc exceeded setpoint by 8.72%.
Based on the past perfonnance of SRVs with 0.3% Platinum-Stellite pilot discs, the District has reasonable confidence that SRVs refurbished with new discs will perform within the Technical Specification Safety Setting limits of the ITS submittal for a period not to exceed approximately ten and one half (10.5) months. The 10.5 month period is based on a linear extrapolation of the data for the worst performing Platinum-Stellite disc (2.4% over setpoint), afler nine (9) months of service. This linear extrapolation shows that at 10.5 months, this worst performing SRV would have been less than 3% over the Tech Spec setpoint, with a small margin. Also, by assuming a linear extrapolation of the data for the other three Platinum-Stellite disc SRVs out to their f
performance after an additional fifteen (15) months of service, none of the valves would have exceeded 3% over the setpoint at 10.5 months.
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May 2,1997 Page 2 of 2 The District is currently refurbishing all eight SRVs with new Platinum-Stellite pilot discs prior to reinstalling the valves for the upcoming cycle. The District is also pursuing a TS change to 2
expand the tolerance of the Safety Setting limit for the SRV setpoint to +/- 3%. These actions 3
provide the District with a high level of confidence that the SRVs will perform within TS limits l
for the ten and one half month period. The District will continue to monitor the industry's efforts to resolve the SRV setpoint drift issue and implement appropriate actions during the mid-cycle shutdown. The shutdown will occur during a window that ensures the valves will be in service for no longer than the above specified period.
Should you have any questions concerning this matter, please contact me.
Sincerely,
(
P. D. Graham Vice President of Nuclear Energy
/rar cc:
Regional Administrator USNRC - Region IV v.
1 Senior Project. Manager i
USNRC - NRR Project Directorate IV-1 Senior Resident Inspector USNRC NPG Distribution l
,l ATTACHMENT 3 LIST OF NRC COMMITMENTS l
j Correspondence No:.NLS970091 The following table identifies those actions committed to by the District in this document.
Any other actions discussed in the submittal represent intended or planned actions by the i
District. They are described to the NRC for the NRC's information and are not regulatory commitments. Please notify the Licensing Manager at Cooper Nuclear Station of any questions regarding this document or any associated regulatory commitments.
COMMITTED DATE COMMITMENT OR OUTAGE Next outage of The District will conduct a mid-cycle outage at Cooper Nuclear sufficient duration Station to ensure Safety Relief Valve performance is meeting within the window Jan-1 Technical Specification limits.
Apr 1998 1
l 1
l PROCEDURE NUMBER 0.42 l
REVISION NUMBER 4 l
PAGE 8 OF 9 l