ML19275A692
| ML19275A692 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 09/27/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Dunn C DUQUESNE LIGHT CO. |
| References | |
| NUDOCS 7910180125 | |
| Download: ML19275A692 (1) | |
Text
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UNITED STATES y, 3 s, g
NUCLEAR REGULATORY COMMISSION j
REGION I 3.? '
O c
631 PARK AVENUE s
- 4, ' b' KING OF PRUSSIA, PENNSYLVANIA 19406 Docket No. :i0-334 SEP 2 713D Duquesne Light Company ATTN:
Mr. C. N. Dunn Vice President Operations Division 435 Sixth Avenue Pittsburgh, Pennsylvania 15219 Gentlemen:
~
The enclosed Bulletin 79-24 is forwarded to you for action. Written responses are required.
If you desire additional information regarding this matter, please contact this office.
Sincerely,
_T oyceH.b-
? Grier
~ Director
Enclosures:
1.
List of IE Bulletins Issued in the Last Six Months cc w/encls:
F. Bissert, Technical Assistant Nuclear R. Washabaugh, QA Manager J. Werling, Station Superintendent G. Moore, General Superintendent, Power Stations Department J. J. Carey, Nuclear Technical Assistant R. Martin, Nuclear Engineer 1185 128 7910180 3m
ENCLOSURE 1 Accession No. 7908220114 SSINS No:
6820 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Bulletin No. 79-24 Date:
September 27, 1979 Page 1 of 2 FR0 ZEN LINES Summary:
On January 3, 1979, an unusua' event occurred at Davis-Besse, Unit 1.
The event involved the freezing of the water in a portion of the high pressure coolant injection (HPCI) system recirculation line that is common to both high pressure coolant injection pumps.
The li.le was not thawed until January 5, 1979, and the event was not reported to NRC until March 12, 1979.
In addition, over the past five years, there have been several events involving frozen instrument and sampling lines.
Description of Circumstances:
The condition was discovered on January 3, 1979, while the reactor was operating at approximately 96 percent power.
During a monthly surveillance test of the HPCI pumps, there was no flow through the recirculation line from the pump discharge to the Borated Water Storage Tank (BWST).
Investigation revealed that water in a portion of the line exposed to the outside weather was frozen.
This portion of the line to the BWST is common to both HPCI pumps.
The line has redundant heat tracing (a heated wire to prevent freezing); it is insulated; and it has a low-temperature alarm system to warn of freezing conditions.
Water in the line froze apparently because of prolonged sub-freezing temperatures and a defect in the insulation.
There was no apparent malfunction of the heat tracing or temperature alarm circuits, although the temperature sensing elements are located in an area not exposed to the coldest temperature conditions.
This recirculation line serves two purposes:
One is to provide a flow path for surveillance testing, and the other is to provide a minimum flow path to preverit possible damage to the pump in the event it is operated against a closed discharge valve or a reactor coolant system pressure greater than the maximum discharge pressure of the pump (approximately 1600 psig).
In the initial review of the event on January 3, 1979, the licensee concluded that the pumps were still operable with i no immediate action was taken to thaw the January 5, 1979, the line was thawed and was successfully completed.
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