ML19282A720
| ML19282A720 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 02/02/1979 |
| From: | Gilleland J TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 7903050584 | |
| Download: ML19282A720 (3) | |
Text
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CH ATTANOOGA. TENNES3EE 37401 500C Chestnut Street Tower 11 c!MS FEB 2 1979 Mr. James P. O'Reilly, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region II - Suite 3100 101 liarietta Street Atlanta, Georgia 30303 Daar Mr. O'Reilly:
OFFICE OF INSPECTION AND ENFORCEMENT BULLETIt: 78 RII:JP0 50-259,
-260, -296 - BROWNS FERRY NUCLEAR PLAST In response to your December 19, 1978, letter which transmitted IE Bulletin 78-14, enclosed are the results of our investigations for Browns Ferry Nuclear Plant.
Very truly yours,
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c3 J. E. Gilleland Assistant Manager of Power Enclosure 79030505b C06 9
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4 ENCLOSURE RESPONSE TO IE BULLETIN 78-14 DATED DECEMBER 19, 1978,
" ACTION TO BE TAKEN BY LICENSEE" 1.
A review was conducted of the Buna-N material applications in the control
, rod serem system at Browns Ferry Nuclear Plant. As requested the results of this review are reported in item 2 below.
2.
The control rod scram system on each unit contains 370 scram pilot valves, 2 backup scram valves, 2 scram discharge volume vent and drain pilot valves, and 1 scram discharge volume test valve, all of which contain Buna-N naterial.
In accordance with General Electric (CE) Company SIL 128, Revision 0, the diaphragms and body gaskets were replaced in the 370 CRD scram pilot valves on all three units during the fire restoration outage.
This work was coepleted on unit 1 on January 27, 1976; unit 2 on December 4,1975; and unit 3 on tby 24, 1976.
Based upon the three-year maintenance interval recommended in CE SIL 128, Revision 0, all Buna-N material in the unit I scram pilot valves with the exception of the two diaphrages and their associated body gaskets was replaced during the recent refueling outage ending January 1979. The new material used for this most recent replacement was packaged in November 1978.
Of the remaining five valves in the control rod scram system only a very small number of random failures have been experienced and replacenent of Buna-N material has not been done. The Buna-N material in the unit 2 scram system, with the exception of the diaphrages and associated body gaskets in the 370 scram Tilot valves, has been in service only since commencing operation in September 1976, subsequent to completion of the fire restoration.
Storeroom records are insufficient to determine the packaging date for the material presently installed in units 2 and 3.
It is our plan to replace all Buna-N material in the scram pilot valves every three years with the exception of the two diaphrages and their associated body gaskets. The diaphrages and gaskets in ten percent of the scram pilot valves will be inspected every three years. A wholesale changcout will depend on the condition of the ones sampled. The diaphragms and body gaskets on all scram pilot valves will be replaced every six years. Also, every three years, all the Buna-N material will be replaced in the other five valves in the control rod scram system. We plan to perform the three-year maintenance program on unit 2 during the May 1979 refueling outage and on unit 3 during the September 1979 refueling outage. This progran will also address the packaging date of n11 replacenent parts to ensure that the recommended shelf life plus service time is not exceeded.
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Our replacement schedule is consiste:.r. with the more recent CE SIL 128, Revision 1, with the exception of the replacement of the diaphragms and their associated body gaskets.
It has been our experience that within a three-year period, problems with the scram pilot valves arise from the heat generated by the coil. This heat appears to be the cause of the material hardening.
Consequently, the Buna-N material in the coil area needs replacing every three years. However, because the diaphragms and body gaskets are located where they receive no heat from the coil we anticipate no significant hardening of the Buna-N material in a six-year period.
During all previous replacements, we have never found a diaphragm to be hard and brittic. Also, during the recent unit I refueling outage ending in January 1979, a sampling of the diaphragms and body gaskets in 10 percent of the scram pilot valves revealed that the material had not deteriorated but remained soft and pliable.
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