ML20066A497
| ML20066A497 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 12/21/1990 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.D.1, TASK-TM 90-778, NUDOCS 9101030314 | |
| Download: ML20066A497 (2) | |
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1 VilMIINI A l$1.UCTHIC AN D l'OWUll COhfl%NY
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United States Nuclear Regulatory Commission Serial No.
90 778 Attention: Document Control Desk NAPS /JHL Washington, D.C. 20555 Docket No.
50 338 License No, NPF 4 Gentlemen:
VIRGINIA ELECTRIC AND POWER-COMPANY NORTH ANNA POWER STATION UNIT 1 PRESSURIZER SAFETY AND RELIEF _ VALVE MODIFICATIONS In response to NUREG 0737, Item II.D.1, Virginia Electric and Power Company installed renective metal thermal insulation " ovens" on the pressurizer safety valve (PSV) loop seals and is modifying the PSV discharge pipe support systems on North Anna 1 and 2.
The combination of loop seal ovens and discharge piping system support modifications was designed to accommodate the effects of the discharge of the water in the loop seals into the discharge piping system when the PSV's are actuated.
The loop seal evens have been insta!!ed in both units. Due to the complexity of the support modifications, the modifications were to be Installed in three phases. Pipe support modifications are complete for North Anna Unit 2. For North Anna Unit 1, the final phase was scheduled to be completed during the 1991 refueling outage which is 4
scheduled to begin January 11,1991.
This lettor is to inform you that the completion of the support modifications planned for l
the upcoming Unit 1 outage is being deferred. We are currently planning to add continuous drains to the loop seal piping. This will change the medium in the loop seal piping to steam and is being pursued as a solution to the issue of PSV setpoint shift which has recently been identified in the industry. The change to a drained loop seal will require new discharge piping system analysis and will result in a change to the discharge piping suppnrt configuration. Optimization of the support designs for the steam discharge conditio.i could eliminate the need for many of the supports which l
were scheduled to be installed.
Deferment of implementation of the support modifications until we have evaluated the effect of eliminating the water seals is cost effective and will promote ALARA poals by eliminating unnecessary radiation exposure.
We are currently developing the project scope and schedule for implementation of the loop beal drain modification. A final scope and schedule will be completed by October 31,1991. We willinform you at that time of the details of the project.
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If you have any questions, please contact us.
Very truly yours, fff$
/fW. L. Stewart i
Senior Vice President - Nuclear cc:
U.S. Nuclear Regulatory Commission Region ll 101 Marietta Street, N.W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. S. Lesser NRC Senior Resident inspector North Anna Power Station l
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