ML20214L338
| ML20214L338 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 05/07/1987 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 86-179D, NUDOCS 8705290277 | |
| Download: ML20214L338 (2) | |
Text
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VINGINIA ELHcTHIC AND POWHH COMi%NY H ICit M ON D, VIHO INI A 2852 61 W. L. Sta waser Vara Passinant N.,u man or...rion.
May 7, 1987 United States Nuclear Regulatory Commission Serial No.
86-179D Attention: Document Control Desk NAPS /JHL:jmj Washington, D.C.
20555 Docket Nos.
50-338 50-339 License Nos.
NPF-4 NPF-7 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 EMERGENCY DIESEL CENERATORS This letter is to clarify our commitment related to the inspection interval for measuring the clearances between the upper piston pin bushings and the insert bushings on the North Anna 1 and 2 emergency diesel generators and also address Colt's. recommendation to lower the governor load limit setting during surveillance of the emergency diesel generators (EDG).
EDG Gap Measurement In the March 25, 1986 letter that transmitted the emergency diesel reliability action plan we indicated that the clearances between the bushings would be measured approximately every six months or every 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> of emergency diesel generator operation, whichever came first.
In the July 14, 1986 letter that transmitted the emergency diesel generator initial engineering evaluation we indicated that the clearances between the bushings would be measured every six months or 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> of accumulated emergency diesel generator operation, whichever came first.
The intent of the bushing gap measurement program was to complete the gap inspections every sixth month in conjunction with the monthly emergency diesel generator surveillances. This schedule would be subject to the condition of Technical Specification 4.0.2.
We intend to proceed with this clarified understanding for future gap measurement inspections.
EDG Load Limit Setting In a June 7, 1985 letter from Colt that was provided to you as a part of our EDG initial engineering report dated July 14, 1986, Serial No. 86-1798, Colt indicated that they were developing a modification that wculd limit fuel rack travel during normal surveillance testing. This modification was to be 8705290277 870507 DR ADOCK 05000338 PDR Q
available by August 1985.
However, Colt recommended manually lowering the governor load limit to 3000 Kw (2000 hour0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> rating) during surveillance as an interim solution.
We reiponded to Colt on July 18, 1985, stating that any action to lower the rack stop setting for non-emergency operation should have the capability of automatically returning the setting to its normal value if an emergency start signal is received. Therefore, we chose at that time not to implement Colt's interim recommendation;
- but, rather wait for the design modification to be completed by Colt. Colt has not completed the design of the load limit modification to date. When Colt has completed the design we will consider its implementation under the auspices of our Diesel Generator reliability task force.
Due consideration will be given to overall diesel
" safety function" as well as surveillance testing concerns.
We are presently evaluating methods that will prevent overloading the North Anna EDGs; specifically, during non-emergency operation when the EDG is parallel to the system.
In early 1986, we reconsidered adjusting the diesel governor load setting to 3000 Kw for purposes of surveillance testing. A special test was performed to determine the appropriate setting.
Periodic test procedures were revised to adjust the load limiter setting to 3000 Kw.
Following several periodic tests, we determined that the possibility of operator error in resetting the limit was too great and therefore elected to prohibit load limiter adjustments during periodic tests.
Until a more permanent solution is found we will continue to use a dedicated operator to monitor the generator's load during non-emergency operation.
Further, we have previously implemented a Technical Specification amendment that reduced the required EDG loading during surveillance tests by approximately 200 Kw.
This decreases the potential that a load swing will result in the EDG exceeding its 2000 hour0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> load rating.
Very truly yours, A
w.
s,
\\
W. L. Stewart ec:
U.S. Nuclear Regulatory Commission 101 Marietta Street, N.W.
Suite 2900 Atlanta, GA 30323 Mr. J. L. Caldwell NRC Senior Resident Inspector North Anna Power Station