ML18038B693
| ML18038B693 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 05/20/1996 |
| From: | Salas P TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEIN-96-007, IEIN-96-7, NUDOCS 9605230210 | |
| Download: ML18038B693 (10) | |
Text
CATEGORY 1 REGULAT..
INFORMATION DISTRIBUTION YSTEM (RIDS)
.ACCESSION NBR 9605230210 DOC.DATE: 96/05/20 NOTARIZED:
NO FACIL:50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 50->9( 'Browns Ferry Nuclear Power Station, Unit 3, Tennessee AUTH.NAME AUTHOR AFFiLIATION SALAS,P.
Tennessee Valley Authority RECIP.NAME RECI'PIENT AFFILIATION Document Control Branch (Document Control Desk)
DOCKET g
05000260 05000296
SUBJECT:
Informs NRC of corrective actions taken by plant w/regard to slow five percent scram insertion times associated w/scram solenoid pilot valves equipped w/viton diaphragms,per NRC Info Notice 96-007.
DISTRIBUTION CODE:
D030D COPIES RECEIVED:LTR i ENCL I
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TITLE: TVA Facilities Routine Correspondence NOTES:
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NOTE TO ALL "RIDS" RECIPIENTS:
PLEASE HELP US TO REDUCE WASTEl CONTACT THE'OCUMENT CONTROL DESK, ROOM OWFN SD-5(EXT. 415"2083')
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Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609 May 20, 1996 U.S. Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of Tennessee Valley Authority Docket Nos.
50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN)
UNITS 2 AND 3 - NRC INFORMATION NOTICE 96-07~
SLOW FIVE PERCENT SCRAM INSERTION TIMES CAUSED BY VITON DIAPHRAGMS IN SCRAM PILOT VALVES TVA is issuing this letter to inform NRC of the corrective actions taken by BFN with regard to the slow five percent scram insertion times associated with Scram Solenoid Pilot Valves (SSPV) equipped with Viton diaphragms.
On January 26,
- 1996, NRC issued the subject information notice to alert licensees of the potential for slow five percent scram insertion times associated with the Automatic Switch Company's Viton "Dual type" SSPV supplied by General Electric (GE) for use in the Control Rod Drive (CRD)
System Hydraulic Control Units (HCU).
As noted in the information notice, it was determined that the slow five percent scram insertion time was attributed to adherence of the Viton type diaphragm to the valve seat in the body of the pilot valve.
l Unit 3 was returned to service on November 29, 1995, after an extended outage utilizing the Viton type SSPVs supplied by GE in all of the 185 CRD HCUs.
BFN performed base line testing of the CRDs and found that the five percent scram insertion times were within the Technical Specification (TS) limits.
- However, because the industry noted a progressive increase in the five percent scram insertion times, BFN replaced the Viton diaphragm in the exhaust port of the SSPVs.
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U.S. Nuclear Regulatory Commission Page 2
May 20, 1996 The Viton type diaphragm and valve body bonnet were replaced with a BUNA-N type diaphragm and a valve body bonnet designed for use with the BUNA-N diaphragm.
The replacement of the diaphragm and the bonnet along with the required post modification testing was completed on March 3, 1996.
The inlet port of the SSPVs is unaffected by this issue and therefore, the Viton diaphragm was not replaced.
BFN Unit 2 had Viton diaphragm equipped SSPVs installed in the HCUs for two CRDs during the Cycle 7 refueling outage.
After approximately six months of operation, BFN noted a progressive increase in the five percent scram insertion time of these SSPVs.
Accordingly, the Viton diaphragms in the exhaust port of the affected valves were replaced during the Cycle 8
refueling outage.
Due to,the service life experienced by the BUNA-N diaphragms in the Unit 2 CRD HCUs, the diaphragms will require replacement at the end of this operating cycle (Cycle 9).
There is only a limited supply of the qualified replacement BUNA-N kits available.
If the issue regarding the long-term qualification of replacement a diaphragm has not been
- resolved, and no diaphragm design has been approved, TVA may be required to utilize Viton diaphragms for Unit 2 Cycle 10 operation.
If we return to the use of the Viton diaphragm, we will notify the NRC.'FN's current TSs require verification of the scram insertion time for all operable control rods after each refueling outage prior to exceeding 40 percent power.
Additionally, the TS require testing of 10 percent of the operable CRDs at 16-week intervals during the operating cycle.
TVA will continue to follow the requirements and periodicity established in.the TSs.
The enclosure contains the commitment made in this letter. If you have any questions, please contact me at (205) 729-2636.
Sincer ly Pe ro Salas Manager of Site Licensing Enclosure cc:
See page 3
Qi
H U.S. Nuclear Regulatory Commission Page 3
May 20, 1996 Enclosure N
cc (Enclosure):
Mr. Mark S. Lesser, Branch Chief U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 NRC Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road
- Athens, Alabama 35611 Mr. George Stramback, Project Manager Regulatory Services General Electric Company
.175 Cutner Avenue San Jose, California 95125 Mr. J.
F. Williams, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852
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ENCLOSURE Tennessee Valley Authority Browns Ferry Nuclear Plant (BFN)
NRC Information Notice 96-07 If TVA returns to the use of the Viton diaphragm for Unit 2 Cycle 10 operation, TVA will notify the.NRC.
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