ML18153D376
| ML18153D376 | |
| Person / Time | |
|---|---|
| Site: | Surry, North Anna  |
| Issue date: | 06/29/1993 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 93-333, GL-89-10, IEB-85-003, IEB-85-3, NUDOCS 9307070389 | |
| Download: ML18153D376 (3) | |
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e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 June 29, 1993 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Serial No.
NL&P/MAE:
Docket Nos.93-333 R10 50-339 50-280 License Nos. NPF-7 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT 2 SURRY POWER STATION UNIT 1 GL 89-10 RESPONSE REVISION SAFETY-RELATED MOV TESTING AND SURVEILLANCE DPR-32 The Virginia Electric and Power Company (Virginia Power) Motor Operated Valve (MOV) Program was implemented to address the requirements of IEB 85-03, "Motor-Operated Valve Common Mode Failures During Plant Transients Due To Improper Switch Settings". The scope of affected systems was increased by Generic Letter 89-1 O, "Safety-Related Motor-Operated Valve Testing and Surveillance" and committed to by our letter dated December 26, 1989 (Serial No.89-530). Generic Letter 89-1 O requires the testing, inspection, and maintenance of safety-related MOVs as well as position-changeable MOVs. This program is to provide assurance that the valves will function when subjected to the design-basis conditions during both normal operation and abnormal events.
Our current schedule commitment to complete the recommendations of Generic Letter 89-1 O is June 28, 1994, for both North Anna Unit 2 and Surry Unit 1. The upcoming North Anna Unit 2 refueling outage is currently scheduled for September 4, 1993, and the upcoming Surry Unit 1 refueling outage is currently scheduled for February 1, 1994. These are the last plant outages before June 28, 1994. In accordance with item I of Generic Letter 89-10, Virginia Power is revising its commitment. Our commitment for Generic Letter 89-1 O is rescheduled for 30 days after the completion of the subsequent refueling outages, which are schedu*led for April 1995 for North Anna Unit 2 and September 1995 for Surry Unit 1. The revised commitment will also enable Virginia Power to address the butterfly valves as discussed in the NRC letter dated May 24, 1993.
Substantial progress has been made in the areas of design basis reviews and initial valve set-up. By the end of the current commitment schedule, it is our intent that the rising stem valves will have been evaluated and initially set-up using diagnostic equipment to establish correct torque, torque bypass, and position limits. The thermal overloads will be replaced by the end of the revised Generic Letter 89-1 O schedule.
Thermal overloads are currently set conservatively to assure the motors function I,,--
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e during a design basis accident.
At Surry, the Generic Letter 89-1 O evaluations resulted in modifications which replaced limit switch rotors, motors, spring packs, and actuators, to allow for proper adjustment of the valves. These modifications are complete.
During the course of implementing the recommendations of Generic Letter 89-1 O, Virginia Power, as well as the industry, has incurred several significant setbacks to completing this work on schedule.
Of particular note are the 1 O CFR Part 21 notifications on diagnostic equipment manufactured by MOVATS Inc. and Liberty Technologies (VOTES).
Virginia Power has procured and utilized both of these diagnostic systems. Each notification required some degree of operability review and retest of i 64 MOVs and i 22 MOVs in safety related systems at North Anna and Surry, respectively. Static and differential pressure tests that were performed with MOVATS equipment were repeated with VOTES equipment.
Differential pressure tests performed with VOTES test equipment have the potential of being invalidated and may require re-testing, based on the torque effect identified in the 1 O CFR Part 21 notification.
Virginia Power has performed differential pressure testing on approximately 32% of the rising stem testable valves for North Anna and 46% at Surry. In order to meet the recommendations of Generic Letter 89-10, Virginia Power intends to continue differential pressure testing at or near design basis conditions during the upcoming outages to further demonstrate the adequacy of our valve sizing and switch setting methodology. A grouping methodology is being developed for each station which is based on the similarity of the valves between Units. This methodology will be used to determine test candidates. Groups are to be defined by the manufacturer's model, type and size of valve as well as the application of the valve in the system. This will provide reasonable assurance that the valves are not generically susceptible to a common mode failure due to design deficiencies in application or uncertainties in the industry sizing equation. It is our intent to perform an instrumented or uninstrumented differential pressure test on nominally 30% of each definable group of testable rising stem, butterfly or plug valves by the end of the revised Generic Letter 89-1 O schedule.
Currently implemented engineering, maintenance and testing programs at Virginia Power have resulted in an increase in the reliability of the MOVs at both North Anna and Surry Power Stations. Safety related MOV failures reported to the Nuclear Plant Reliability Data System (NPRDS) have decreased from 8% in 1989 to less than 1 % in 1992 at North Anna and have decreased from 10% to 2% at Surry in the same time frame.
If you have any questions or require additional information regarding our change in schedule commitment or intent to utilize grouping methodology, please contact us.
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W. L. Stewart Senior Vice President - Nuclear
I cc:
U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, N.W.
Suite 2900 Atlanta, Georgia 30323 Mr. D. R. Taylor NRC Resident Inspector North Anna Power Station Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station e