ML19210C885

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Responds to IE Bulletin 79-24.Problem of Frozen Sensing Lines Corrected W/Permanent Insulation Around Steam Generator Pressure Transmitter Sensing Lines.All Fluid Lines in Facades Heat Traced & Monitored on Regular Basis
ML19210C885
Person / Time
Site: Point Beach  NextEra Energy icon.png
Issue date: 10/29/1979
From: Fay C
WISCONSIN ELECTRIC POWER CO.
To: James Keppler
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-79-24, NUDOCS 7911200258
Download: ML19210C885 (2)


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l WISCONSIN Electnc eona coupaur 231 W MICHIGAN. P O BOX 2046 MILWAUKEE. WI 53201 October 29, 1979 Mr. J. G. Keppler, Regional Director Office of Inspection and Enforcement, Region III U. S. NUCLEAR REGULATORY COMMISSION 799 Roosevelt Road Glen Ellyn, Illinois 60137

Dear Mr. Keppler:

DOCKET NOS. 50-266 AND 50-301 RESPCUSE TO IE BULLETIN 79-24 POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 On October 1, 1979 we received IE Bulletin 79-24 which described an unusual event involving the freezing of water in a portion of a high pressure coolant injection system recirculation line. The bulletin mentioned that similar events involving frozen instrument and sampling lines have also occurred at other facilities.

All licensees were requested to review their plants to determine that adequate protective measures have been taken to assure that safety related proce s, instrument, and sampling lines do not freeze during extremely colt weather.

As indicated in the bulletin, Point Beach Nuclear Plant has experienced two incidents of frozen sensing lines. Both these events involved the same Unit 1 steam pressure sensing line. The initial event occurred in 1976 when a gap in the insulation allowed subfreezing air to contact the line. The gap was filled with insu-lation to prevent further cold air contact. This line froze again at the same spot in 1977 when the insulation which had been added after the initial occurrence was dislodged by pressure fluctuations caused by unrelated repairs to the auxiliary building air conditioning unit. In both of these cases the outside ambient air temperature was below 0*F.

Following the second line freezing incident, a number of corrective dated January actions were taken as discussed in our LER 266/77-13/03L-1 12, 1978. The immediate problem was corrected by placing permanent insulation around the steam generator pressure transmitter sensing line. As a precaution against other lines 1373 101 tt0V 1**

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Mr. James G. Keppler October 29, 1979

' being exposed to freezing temperatures, all other similar penetra-tions of sensing and instrument lines were checked and insulated as necessary to assure that no previously unnoticed insulation gaps existed. In addition, an annual check of these penetrations was added to the plant cold weather call-up list.

All fluid lines in the facades at Point Beach Nuclear Plant can be exposed to subfreezing temperatures during winter weather.

These lines are heat traced for freeze protection and monitored on i a routine basis. This monitoring includes a multichannel recorder located in the auxiliary building which tracks the status of each of the heat tracing channels. Trends and gradual changes in the performance of the heat tracing circuitry can be determined by observing these point recordings. If any freeze protection channel suddenly fails, a common alarm is annunciated in the control room.

The heat tracing monitor can then be checked to determine exactly which channel has caused the alarm. Additionally, a cold weather call-up card and check list is used to prepare for cold weather conditions each year to assure the operability and integrity of these heat tracing and insulating measures. We believe that these measures will continue to provide reasonable assurance that process, instrument, and sampling lines will not freeze during extremely cold weather.

Very truly yours, s

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C. W. Fay, Director Nuclear Power Department

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