05000281/LER-1978-040-03, /03L-0 on 781116:routine Testing Revealed Failure of Heat Tracing Circuit 4C Unit 2 Boron Injection Tank Top Recirculation Return.Caused by Boric Acid Damage to the Heat Tracing Circuit

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/03L-0 on 781116:routine Testing Revealed Failure of Heat Tracing Circuit 4C Unit 2 Boron Injection Tank Top Recirculation Return.Caused by Boric Acid Damage to the Heat Tracing Circuit
ML18113A689
Person / Time
Site: Surry 
Issue date: 12/11/1978
From: Baucom T
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML18113A687 List:
References
LER-78-040-03L-01, LER-78-40-3L-1, NUDOCS 7812140234
Download: ML18113A689 (3)
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LER-1978-040, /03L-0 on 781116:routine Testing Revealed Failure of Heat Tracing Circuit 4C Unit 2 Boron Injection Tank Top Recirculation Return.Caused by Boric Acid Damage to the Heat Tracing Circuit
Event date:
Report date:
2811978040R03 - NRC Website
v • d • e

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!During normal operation, routine testing revealed the failure of heat tracing circuit I (filJ 14c (Panel 11) Unit 112 Boron Injection Tank Top Recirc. return.

This is a degraded lm:J 1mode of ope_ration permitted by T.S. 3.3.B.5 and is reportable as per T.S. 6.6.2.b. (2)]

@I[J 1The health and safety of the general public were not affected.

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~7 o:::::t]J JA review of the heat tracing circuit showed that fail~ was caused by boric acid J

IJ]JJ.,damage of the heat* tracing cirucit.

The corrective action taken was to replace the fJ.:]II !heat tracing tape~.

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. Atta~hment,

  • 6 Surry.Power Docket No:

Report No:

.Event Date:

Page 1 of 1 Station, Uni~*

50-281 78-039/03L-0 11-15-78

- Title of Report:

Failure of Loop B Hot Leg Temperature Sensor

.1. Description of Event:

During normal operation it was found that* the "B" loop hot leg temperature sensing element TI-2-422A was drifting low.* This resulted in the inability of TI-2-422A to supply a reliable signal to Channel II Overpower~ Overtemperature Delta-T Protection.

The required degree of redundancy was no.t maintained and this is contrary to Technical Specifications 3.7.B and is reportable per T~ch-nical Specifications 6.6.2.b.(2).

2.
  • Probable Consequences and Status of;Redundartt*Systems:

. Channel II Overpower - Overtemperature Delta-T Protection was placed in the trip mode.

All other overpower - overtemperature instrumentation remained operable.

Because the required immediate corrective action was taken and the degree of redundancy regained, the health and safety of the general public.were.

not affected.

  • 3.

Cause

This event was caused by a packing leak in-a_RTD 11..oop isolation valv~ (RC-52)

. which sprayed on the Loop B hot leg temperature sensors.

The sensing element insulatio.n resistance decreased causing the output to drift.

4.

Immediate Corrective Action

Channel II Overpower - Overtemperature Delta~T Protection was_placed in the trip mod_e.

This restored the required degree of redundancy.

5.

Subsequent Corrective Action:

  • The insulation :resistance was monitored and when it returned to:its normal range, the instrumentation was calibrated, tested aad returned to service.

6 *. Actions Taken to Prevent Recurrence:

No further corrective action will be required to prevent recurrence.

The packing leak will be rectified during the next outage.

7.

Generic Implications:

None

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_..J '(A:tt;_achment, page 1.)

Surry Power Station; Unit 2 Docket No: 50-281 Report No: 78-040/03L~O Event Date: 11-16-78 Low Current on Heat Tracing

1. * -_Description of Event:
2.
3.

With the unit in normal operation at rated power, routine surveillance indicated that heat tracing circuit 4C (Panel 11) was operated at less than the current specified in the surveillance document.

No low temperature alarms were indicated.

Investigation for faulty heat tracing tape was initiated on the affected circuit. Faults were found on circuit 4C (Panel 11) Uriit #2 Boron Injection Tank Top Recirc. Return, and were identified as being the result of boric acid attack on tape *. The tape was. replaced and circuit current verified to be within spec~ of the surveillance document.

This is a degraded mode of operation permitted by T.So 3.3.B.5 and is reportable in accordance with T.S. 6.6.2.b.(2).

Probable Consequences/Status of Redundant Systems:

At all t-imes during the event, the temperature in the piping served by the affected.circuiti was maintained as required.

The redundant circuit was operable.

There were at all times two operable flow paths for boric acid to the reactor. Therefore, the health and safety of the public were not affected.

Cause

The reduc~d currents were due to boric acid damage.to the heat tracing tape on affected circuits.

4.

Immediate Corrective Action

The heat tracing tape was replaced.

5.

Scheduled Corrective Action:

The problem was corrected immediately and no further action is required.

6.* Action Taken to Prevent Recurrence:

Continuous surveillance is maintained on the heat tracing systems.

No additional action is 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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