ML20127B708
| ML20127B708 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 02/23/1971 |
| From: | Duncanson R NORTHERN STATES POWER CO. |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9102110263 | |
| Download: ML20127B708 (2) | |
Text
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/bn, NORTHERN STATE 5 POWER COMPANY f/inneapolis, f/innesota 55401 to Fetrvary 23, 1971 g
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c Dr. Peter A. Mor r is, Dir ector k [4 m
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g[cbn D Division of Peactor Licensirt 4
,w United States Atomic Energy Commission 5
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g Washirgton, D.C.
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Dear Dr. M'rris:
MONTICELLO NUCLEAk GENET ATlfG PLANT E-5979 g
8 Docket No. 50-263 License No. DPR-22 C
Unsuccessful E f fie f ency TestinE of a Siandby Gas Treatment System Pariiculate Filter Efficiency tests of the Standby Gas Treatment System particulate filters at the Monticello Nuclear Generat ing Plant revealed that one HEPA filter did not meet Te r emoval of ficiency requirements.
We interpr et ibis occur rence to te
- porlable to your office in accor dance with Sect ion C.6.C. I of Appendix A, Specificat ions, of the Provisional Oper at ing License DPh-22.
The ec ht.c<
Fegion lli Compliance Of fice has teen previously notified of the occur rence.
Srcury Descr iot ion of Oenurrence On January 27, 1971, Nuclear Contairment Systems, Inc. personnel performed DOP ef ficiency tests on the Standby Gas Treatment System (SGTS) HEPA filters.
All of the SGTS filters were founo to be greater than 99 percent efficient with the exception of the upstream HEPA filter, F-34B-2, for SGTS Train B which was found to be between 96 and 97 percent ef ficient.
The downstream HEPA filter was tested at 99.92 percent ef ficient.
An inspection of filter F-348-2 revealed that there were small burn holes l
on the upstream side of the filter.
It is believed that these burn holes l
were caured by sparks fr om a cuttirg torch or pr inding wheel which were used when the Train B air heater was modified since DOP test ing pr ior to the modification work showed that the filter per formed as required.
At the time of the air heater modification work i t was not recognized that this work could effect the filter system ef ficiency.
Two of the eight filter units of the upstream HEPA filter, f-34B-2, were replaced and, wher e necessary, ihe of her filier uniis were r itched wiih a silicone sealant.
A retest of filter F-34B-2 on January 27 1971 showed 3
the filter to be 99.97 percent efficent.
Also, for yout information, one of the two parallel of f-gars system HEPA rilters, F-3A, was found to be only 91% efficient as revealed by DOP testing N
9102110263 710223
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PDR ADOCK 05000263 d
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' 1 on January 28, 1971.
T he second of f-gas system filter, F-3B, was tested at 99.99 percent ef ficient.
Investication of the F-3A filter did not reveal any reason for ihe irefficienty (moisture damage is suspected) and sult.cquent retests of the filter wer e not successf ul.
The F-3B filter has teen valved in service for operation of the off-gas system.
Prior to the initial need for the off-gas system, which tegan on February 19, 1971, the F-3B filter was successfully DOP tested on February 18th.
Two new of f-gas system car tr idges, with charcoal teds included, have been ordered for immediate delivery.
Following the necessary review of the planned installation of these cartrid es, the E
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cartr idges will te installed and DOP and Freon ef ficiency tests will be perfortred.
An on-site Unusual Occur rence investigation of the unsuccessful DOP filter ef ficiency tests has been completed and a report has been written. This information will be available to the Region ill Compliance Inspector for review during his rext site inspection.
Your s ver /att uly,
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&dbP 0 F.
U. vuncanson, Jr., j. L.
Gen. Supt. of Power Plants '/e hanical Chairman-flonticello Safety Audit Committee EOD/mm 3
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