ML13333A576
| ML13333A576 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/13/1987 |
| From: | Medford M SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| GL-83-28, NUDOCS 8711190183 | |
| Download: ML13333A576 (2) | |
Text
00 Southern California Edison Company P 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD. CALIFORNIA 91770 M.O.MEDFORD TELEPHONE MANAGER OF NUCLEAR ENGINEERING (818) 302-1749 AND LICENSING November 13, 1987 U. S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Generic Letter 83-28 On-Line Testing of Reactor Trip Breakers San Onofre Nuclear Generating Station Unit 1
Reference:
Letter from R. F. Dudley, NRC, to K. P. Baskin, SCE, dated July 20, 1987, same subject In response to SCE's submittal dated November 28, 1983 regarding Generic Letter 83-28, the referenced letter requests SCE to submit additional information on Item 4.5.3 relating to on-line testing of the reactor trip system. Specifically, the referenced letter requests detailed information regarding the impracticality of implementing on-line testing in relationship to the associated benefit gained through increased availability and reliability of the Reactor Protection System (RPS).
The following information outlines the extent of plant modifications necessary to implement on-line testing, including an estimated cost. A discussion regarding the incremental benefit in RPS reliability that may be gained with this capability is also provided.
At San Onofre Unit 1, the design of the Reactor Trip Breaker (RTB) switchgear is two Westinghouse DB-50 breakers in series. With this configuration no capability exists to bypass a single breaker, consequently tripping one breaker results in a reactor trip. Implementation of on-line testing of the RTBs would require installation of two additional bypass breakers. Due to space considerations adjacent to the existing breakers within the 4 kV switchgear room, installation of two additional breakers would require relocation of several large non-safety related equipment cabinets. The optimal method of installing two additional breakers would be to locate these breakers immediately adjacent to the existing breakers and relocate the non-safety related equipment currently at that location to another location within the 4 kV room. The cost of these relocations and the purchase of two bypass breakers is estimated to be $2.5 to $3.0 million.
8711190183 871113 PDR ADOCK 05000206 P
Document Control Desk November 13, 1987 In regards to the benefit associated with implementing on-line testing, it is SCE's position that the current maintenance and testing programs ensure adequate reliability of the reactor trip system, and plant modifications to implement on-line testing will not provide a significant increase in reliability. As indicated in SCE's letter dated April 27, 1984, the San Onofre DB-50 Reactor Trip Breaker Maintenance program is in full conformance with the Westinghouse Owners Group (WOG) maintenance recommendations. As indicated in your SER dated March 6, 1987 for Items 4.2.1 and 4.2.2 of Generic Letter 83-28, the refueling outage maintenance interval for the RTB's was determined to be acceptable. Further, measurement of undervoltage trip attachment dropout voltage, trip force and insulation resistance is performed in accordance with the WOG guidelines. SCE letters dated May 14, 1985 and June 3, 1987 each provide a detailed discussion of this issue. It is also noted that historical breaker performance data provided in our letter dated October 1, 1984 demonstrates a high degree of breaker reliability in that the breakers have never failed to open on demand. The data is based on breaker actuations from an "as found" condition (i.e., no breaker manipulations were performed prior to the actuation). Based on the breaker performance and demonstrated reliability, coupled with the thorough maintenance program designed to detect degradation of components that could inhibit breaker performance, there is no significant benefit to implementing on-line testing.
Based on the above, SCE believes the cost associated with implementing on-line testing at San Onofre Unit 1 does not provide sufficient increase in RPS reliability to justify the expenditure. The demonstrated reliability of the existing configuration ensures system operability without necessitating additional breaker testing. Consequently, SCE maintains the existing reactor trip system is acceptable with a two breaker configuration and the capability to perform on-line testing is not necessary.
If you have any questions or require additional information, please let me know.
Very truly yours, cc: J. Bradfute, NRR Project Manager, San Onofre Unit 1
- 3. B. Martin, Regional Administrator, NRC Region V F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3