05000280/LER-1978-033-03, /03L-0 on 781015:heat Tracing Circuit Failed. Caused by Old Boric Acid Buildup & Penetration of Heat Leakage

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/03L-0 on 781015:heat Tracing Circuit Failed. Caused by Old Boric Acid Buildup & Penetration of Heat Leakage
ML18113A605
Person / Time
Site: Surry 
Issue date: 11/06/1978
From: Baucom T
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML18113A601 List:
References
LER-78-033-03L-01, LER-78-33-3L-1, NUDOCS 7811090219
Download: ML18113A605 (2)
v • d • e


LER-1978-033, /03L-0 on 781015:heat Tracing Circuit Failed. Caused by Old Boric Acid Buildup & Penetration of Heat Leakage
Event date:
Report date:
2801978033R03 - NRC Website
v • d • e

text

NF~C*FORM 3~6 17-77) e

  • . NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT CONTROL BLOCK: I I G)

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) 1 6

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tracing circuit 24C (Panel 8), serving Unit 1 boric acid-to-blender flow transmitter.

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!This event _is contrary to T.S. 3.2.B.5 and is reportable as per T.S. 6.6.2.b.(2).

The health and safety of the general public were not affected.

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check of t~e ~e2t tracing circuit revealed that failure was caused by old boric acid OJJJ !buildup a::::.c. -p-2-.rle~rat:ia:::. o:: the heat tracing strip heater.

The strip heater was rrm \\replaced. ::~o source c= l22kage was found at the time the heater was replaced *.

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(Attachment, Page 1 of 1)~

Surry Power Station, Unit 1 Docket No: 50-280 Report No: 78-033/03L-0 Event Date:

10-15-78 Low Current Heat Tracing

1. Description of Event

With the unit in normal operation at**rated power, routine surveillance indicated that heat tracing circuit 24C (Panel 8) was operating at less than the current specified:in the surveillance document.

No low temperature alarm was indicated.

Verification was ob.tained that the redundant circuit 24C (Panel 9) was operable.

Investigation for faulty heat tracing was initiated on the affected circuit. Faults were found on circuit 24C (Panel 8) serving Unit 1 boric acid-to-blender flow transmitter, *and was* identified as boric acid buildup on strip heater.

The strip heater was replaced, load checked, and the current value was verified to be within limits delineated in the surveill~nce document.

The event constitutes a condition contrary to Technical Specificationr 3.2.B.5 and is reportable in accordance with Technical Specification 6.6.2.b.(2).

2. Probable Consequences/Status of Redundant system:

At all tiwes during the event, the temperature in the piping, served by the af;fected circuit, was above minimum limits e The;~reduni:lant piri.cuit *was operable, Therefo=e, the health and safety of the public were not affected.

3.

Cause

T'~e lD"* cu..---rent reading was due to boric acid buildup on the strip heate~ 52-~i~g t~ £low transmitter *. No source of the leakage leading to buildup on the s~ri? heater was evident. All potential sources had been corrected previously.

4.

Immedia~e Co~e~ti7e Action:

It wa.s verified that the redundant circuit 24C (Panel)) was operable.,

The defective strip heater was replaced.

5.

Scheduled Corrective Action:

The problem was corrected by heate*r r~p1acement and no furhher ac tioii *...

is required.

6.

Action Taken to Prevent Recurrence:

Routine periodic surveillance is carried out on the heat tracing systems as required for unit operation.

This surveillance has identified problems for timely connection, therefore no additional measures are considered necessary.

7.

Generic Implications:

This failure, as with others in the system, is considered random since no specific circuit or panel has exhibited repeated failure.

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