ML19275A323
| ML19275A323 | |
| Person / Time | |
|---|---|
| Site: | La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 09/27/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Linder F DAIRYLAND POWER COOPERATIVE |
| References | |
| NUDOCS 7910040046 | |
| Download: ML19275A323 (1) | |
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,o SEP 2 7 :979 Docket No. 50-409 Dairyland Power Cooperative ATTN:
Mr. F. W. Linder General Manager 2615 Erst Avenue - South La Crosse, WI 54601 Gentlemen:
The enclosed IE Bulletin No. 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,
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[a'm A G. Q ler Director
Enclosures:
1.
Designated Applicants for Operating Licenses cc w/ encl:
Mr. R. E. Shinshak, Plant Superintendent Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Anthony Roisman, Esq.,
Attorney 1099 098 7f10040'O b
Accession No. 7908220114 SSINS No:
6820 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 September 27, 1979 IE Bulletin No. 79-24 FROZEN LINES Se;<ary:
On January 3,1979, an unusual 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 hi0h pressure coolant injection pumps. The line 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 frczen.
This portion of the line to the BWST is common to both HPCI pumps.
ihe 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-freering 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 coi.ditions.
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 prevent 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 the recirculation line frozen.
Therefore, no immediate action was taken to thaw the frozen section of the line.
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