ML20141M545
| ML20141M545 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 08/18/1992 |
| From: | Rosenblum R SOUTHERN CALIFORNIA EDISON CO. |
| To: | Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| NUDOCS 9209010114 | |
| Download: ML20141M545 (3) | |
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23 PAOKER STHEET IRVINE. CALIFORNIA 92718 August 18, 1992 NUCtF AA flECat it AT(WW aft AsF4G U. S. Nuclear Regulatory Commission, Region V Attention: Mr. J. B. Martin 1450 Maria Lane, Suite 210 Walnut Creek, CA 94596-5368 f
Gentlemen:
Subject:
Docket No. 50-361 j
Temporary Facility Modification sn Onofre Nuclear Gerorating Station Unit 2
Reference:
SCE letter to J. B. Martin dated August 4, 1992.
" Temporary Facility riodification" This letter provides a correction to our letter of August 4,1992,
- Temporary.
Facility Modification," referenced above.
The August 4,1992, letter informed the NRC of a modification to the containment mini purge system on Unit 2 which was installed due to difficulties experienced with using containment mini purge isolation exhaust valve 2HV9825.
In paragraph 4 of the " Background" section, we stated, " Subsequent to a-failure of the qualterly LLRT on March 30, 1992, as e conservative measure, we began performing an LLRT immediately after every purge or vent using the mini purge lines."
The March 30, 1992 date was incorrect and the letter shauld have provided t:ie correct date of June 9,1992.
The Local Lenk Rate Test (LLRT) failure on March 30, 1992 was for the main purge isolatior. valve not the mini purge isolat:on valve. The timeline for the implementation of special leak rate testing on valve 2HV9825 is as follows:
1)
On March 30, 1992, the main purge valve f ailed the quarterly LLRT.
2)
On June 9,1992, penetration 19, which includes tb main purge nhaust line and the mini parge exhaust line, failed the quarterly LLRT.
The leakage was corrected by Llowing off the valve seats of mini purge isolatien valves 2HV9825 and 2HV9824. A second LLRT was performed on the penetration which resulted in essentially no leakage. At this time, the leakage was suspected to be from mini purge isolation valve 2HV9825, although there was insufficient data to prove this. Therefore, we decided to perform an LLRT on the mini purge isolation valve following the next vent operation to determine the source of the elevated leakage.
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Mr.'J. 8. Martin 4 3)
On June 16-17, 1992, the mini purge valve was tcsted prior to a containment vent and exhibited virtually no leakage.
Elevated leakage was found during the test following containment ventirg.
The valve seat of the inboard mini purge isolation valve 2HV9824 l
was blown off, but the penetration continued to exhibit elevated leakage. The valve seat of outboard valve 2HV9825 was blown off, and the subsequent LLRT confirmed essentially no leakage.
i 4)
On June 29, 1992, valve 2HV9825 was stroked +hree times and an l
LLRT was performed after each stroke to evaluate L;ie possibility that the previous instances of elevated leakage were the result of valve stroke problems. This testing demonstrated that the leakage experienced during the previous LLRTs was not a valve stroke problem.
5)
To continue the investigation of the valvo operation, on July 2, 1992, an LLRT was narformed before and after a contair. ment vent.
Essentially no ierkage was found pd or to venting contcinment.
Elevated leakage was found after venting containment. After blowing off the valve seat of 2HV9825 a second LLRT was performed i
with essentially no leakage.
Based on elevated leakage being corrected by blowing off the seat of the outboard valve and not the inboard valve we postulated that particulate matter was originating within the penetration and becoming entrained on the valve seat.
6)
On July 1 1992, an LLRT was performed before and after a containst..t vent with a reduced containment pressure.
Estimations cf air velocity over the v61ve seat when venting was performed at the normal containment pressure of 1 psig showed that very high air velocities occurred. Performing the vent at reduced containment air pressure substantially reduced the flow relocity and was therefore believed to be a possible solution to the elevated leakage prob'em. Because the LLRT performed subsequent to the reduced pressure vent demonstrated elevated leakage and because only the outboard valve required correction, this i
confirmed that particulate matter was coming from inside the penetration rather than from containmert.
7)
Because the valve had exhibited elevated leakage-on four l
consecutive occasions and efforts to correct the problem had i
been ineffective, use af the mini purge valve was ceased and on l
July 30-31, 1992 the temporary facility 'aodification was placed in service.
Based on this information, the referenced letter should have stated that LLRTs were performed on the mini purge isolation valve after every vent following the quarterly LLRT performed on June 9,1992.
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p Mr. 'J. B. Hartin If you have any questions concerning this matter, please let me know.
Very Truly Yours YM cc:
J. B. Martin, Regional Administrator, NRC Regior. V C. W. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2&3 H. B. Fields, NRC Project Manager, San Onofre Units 2 and 3 I
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