ML19254D014
| ML19254D014 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/27/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Proffitt W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| References | |
| NUDOCS 7910190288 | |
| Download: ML19254D014 (2) | |
Text
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UNITED STATES 8
NUCLEAR REGULATORY COMMISSION REGION ll o
101 MARlETTA ST N.W., SUITE 3100 e
ATLANTA, GEORGIA 30303 SEP 2 71979 In Reply Refer To:
RII:JPO 50-404 50-405
- c. _-.
s Virginia Electric and Power Company Attn:
W. L. Proffitt Senior Vice President, Power P. O. Box 26666 Richmond, Virginia 23261 Gentlemen:
The enclosed Bulletin 79-24 is forwarded to you for information.
If you desire additional infor=ation regarding this matter, please contact this office.
Sincerely, D
James P. O'Reilly Director
Enclosure:
IE Bulletin No. 79-24 1190 075-m + ;,
7010190 6 O
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SEP 2 71979 Virginia Electric and Power Company cc w/ encl:
V. R. Cartwright, Station Manager Post Office Box 402 Mineral, Virginia 23117 P. G. Peri
- Senior Resiuent Engineer Post Office Box 38 Mineral, Virginia 23117 1i90 076 f
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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 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 high pressure coolant injection pumps. The line wa 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 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 f--~~~
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January 5,1979, the line was thawed and tl was successfully completed.
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