ML19275A655
| ML19275A655 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 09/27/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 7910180070 | |
| Download: ML19275A655 (1) | |
Text
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'o, UNITED STATES 8 'yh,'ff[ d 7.
... g '7' NUCLE AR REGULATORY COMMISSION 5 -
REGION V
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1990 N. CALIFORNIA BOULEVARD o, h N
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d SUITE 202, WALNUT CREEK PLAZA WALNUT CREE K, CALIFORNIA 94596 September 27, 1979 Docket No. 50-312 Sacramento Municipal Utility District P. O. Box 15830 Sacramento, California 95813 Attention:
Mr. John J. Mattimoe Assistant General Manager 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, n
lL' ((")~pi(A-,.
R. H. Engelken Director
Enclosures:
1.
Designated Applicants for Operating Licenses cc w/ enclosures:
R. J. Rodriguez, SMUD L. G. Schwieger, SMUD 1185 061 y 91o180 6 70
Accession tio. 7908220114 SSINS tio:
6820 UNITED STATES t;UCLEAR REGULATORi COMMISSION OFFICE OF INSPECTI0tl AllD ErlFORCEMENT WASHIrlGTON, D.C.
20555 September 27, 1979 IE Bulletin flo. 79-24 FR0 ZEN LINES Summary:
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 hiah 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 Circunstances:
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 ounps, there was no flow through the recirculation line from the pump discharge to the Borated Water Storage Tank (BNST).
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 connon 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 alarn 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 nalfunction 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 prevent possible damage to the pump in the event it is operated against a closed discharge valve or a reactor coolant systen pressure greater than the maxinum 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 imediate action was taken to thaw the frozen section of the line.
On January 5, 1979, the line was thawed ar' "'
was successfully completed.
DUPLICATE DOCUMENT 1185
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