ML19275A640
| ML19275A640 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 09/27/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 7910180047 | |
| Download: ML19275A640 (1) | |
Text
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September 27, 1979 Docket No. 50-267 Public Service Company of Colorado ATTN:
Mr. C. K. Millen Senior Vice President P. O. Box 840 Denver, Colorado 80201 Gentlemen:
The enclosed IE 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,
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Karl V Seyfrit Director
Enclosures:
1.
Designated Applicants for Operating Licenses 3.
List of IE Bulletins Issued in Last Six Months cc:
D. W. Warembourg, Nuclear Production Manager Fort St. Vrain Nuclear Station P. O. Box 368 Platteville, Colorado 80651 L. Brey, Manager, Quality Assurance
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Accession No. 7908220114 SSIMS 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 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 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 tM 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 initir.1 review of the event on January 3, 1979 the licensee concluded that the pumps were still operable witt no immediate action was taken to thaw t January 5, 1979, the line was thawed at DUPLICATE DOCUMENT was uccessfully completed.
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IE Bulletin No. 79-24 Date:
September 27, 1979 Page 2 of 2 Cause of Causes:
This event is attributed to an inadequate design. The heat tracing provided on this recirculation line was unable to prevent freezing when the line was exposed to sub-freezing temperatures for a prolonged period of time. The temperature sensors which control the heat tracing and which trigger the low-temperature alarm were located in an area not exposed to the coldest temperatures to which the piping is subjected.
Corrective Action:
To prevent recurrence, the licensee increased the temperature setting of the thermostat for the heat tracing on the recirculation line. Further, a temporary enclosure was built around the line and additional heat tracing was installed.
Af ter the line was thawed and blown down, surveillance testing to verify pump operability was performed. An engineering evaluation was initiated by the licensee to develop long-term corrective action.
Other Frozen Lines:
In addition to this event at Davis-Besse, there have been many events involving frozen instrument and sampling lines. During the last five years, facilities experiencing events of this kind include:
Arkansas Nuclear One Oconee Davis-Besse Pilgrim Duane Arnold Point Beach Hatch Salem Fitzpatrick Surry Haddam Neck Troj an Indian Point Zion Millstone Action To Be Taken:
All licensees and construction permit holders receiving this Bulletin for action are requested to review their plants to determine that adequate protective measures have been taken to assure that safety-related process, instrument, and sampling lines do r.at freece during extremely cold weather.
The results of these reviews should be reported to the Regional Director by October 31, 1979.
Approved by GAO (R0072); clearance expires 7/31/80.
Approval was given under a blanket clearance specifically for generic problems.
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