ML19261B507
| ML19261B507 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay |
| Issue date: | 01/29/1979 |
| From: | Crane P PACIFIC GAS & ELECTRIC CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| NUDOCS 7902280091 | |
| Download: ML19261B507 (2) | |
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PACIFIC GAS AND E LE C T RI C C O M PANY 3
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R. H. Engelken, Director gg Office of Inspection and Enforcement V 7' e -
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Docket No. 50-133 License No. DPR-7
Dear Mr. Engelken:
This is in response to your letter dated December 19, 1978 which enclosed IE Bulletin 78-14.
IE Bulletin 78-14 requested that we review the Buna-N material applications in our control rod drive system and specifically identify the following:
- 1) time since in-stallation; 2) time since packaging for installed material; 3) sched-ule for replacement (both in response to this bulletin and for periodic maintenance) ; and 4) the basis for our schedule of replacement and justification for any proposed replacement time in excess of three years.
We have completed the required review which indicates that the last replacement of all Buna-N materials in the control rod scram system at Humboldt occurred in June 1975.
The time interval between packaging and installation is not known.
The replacement schedule for the Buna-N materials was established in 1975 at five years.
This in:erval was chosen based upon 12 years of operating experience and our maintenance experience with this type material that showed some scattered failures after an inservice period of six years.
In response to the problems identified and the recommendations made by IE Bulletin 78-14 and the referenced General Electric Company Service Information Letters, we propose to reduce our preventive maintenance interval to correspond to every third regularly scheduled refueling outage which is approximately every three years.
In no case will the interval be allowed to exceed 40 months.
We believe that this interval is con-cervative based upon our previous experience with Buna-N at Humboldt.
790228009{
r Mr. R. H. Engelken 2
January 29, 1979 To initiate this program, we will purchase new parts and replace all of the Buna-N materials in the control rod scram system shortly before startup following completion of the current seismic studies.
For all future replacemer_ ts we will continue our past practice, which has been to order replacement parts eight to ten months prior to the scheduled replacement, thus minimizing the shelf time.
Very truly yours, r
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CC:
Director Office of Inspection and Enforcement Division of Reactor Operations Inspection U.
S. Nuclear Regulatory Commission Washington, D. C. 20555