ML19317F451

RO 270/77-01:on 770111,one Channel of Borated Water Storage Tank (Bwst) Level Indication Found Inoperable.Caused by Frozen Process Line Between Bwst & Bwst Level Transmitter. Line Thawed & Insulated

ML19317F451
Person / Time
Site:	Oconee
Issue date:	01/31/1977
From:	DUKE POWER CO.
To:
Shared Package
ML19317F447	List: ML19317F446 ML19317F451
References
RO-270-77-01, RO-270-77-1, NUDOCS 8001140686
Download: ML19317F451 (2)

Text

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DUKE POWER COMPANY (3

L/ , OCONEE UNIT 2 Report No.: R0-270/77-1 Report Date: January 31, 1977-Occurrence Date: January 11, 1977 Facility: Oconce Unit 2, Seneca, South Carolina Identification of Occurrence: One channel of borated water storage tank level indication inoperable Conditions Prior to Occurrence: Unit at 100 percent full power Description of Occurrence:

On January 11, 1977 one of two redundant channels of the Oconee Unit 3 borated water storage tank (BWST) 1cvel instruments indicated a fluctuating tank water level. The remaining instrument indicated that the level of borated water required by Technical Specifications was being maintained.

Investigation was promptly initiated and revealed that the fluctuating water level indication was erroneous due to a faulty level indication channel.

This condition is considered to be reportable since it constituted operation in a degraded mode permitted by a Limiting Condition for operation. Techni-cal Specification 3.3.5 makes provision for the removal from service for test or monitoring of any component of high pressure injection, low pressure injection or reactor building spray for a period of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> provided not more than one train of each system is afflicted. The BWST level channel was restored to operable status within five and one-half hours.'

Apparent Cause of Occurrence:

This occurrence was caused by the freezing of the process line between the Oconee Unit 2 BWST and the BWS1 'evel transmitter. Due to an installation deficiency the wire connection tees associated with the Dekoron heat tracing system had not been insulated which allowed the process line to be exposed to below freezing temperat"re= and resulted in the frozen line and faulty indication.

Analysis of Occurrence:

This occurrence resulted in the loss of one of two redundant channels of BWST level indication for approximately five and one-half hours. During this period, the redundant level transmitter properly indicated the true level in the BWST. The conditions of the BWST required by Technical Speci-fication 3.2 were maintained and the emergency core cooling systems would have performed as required in the unlikely event they were needed. It is concluded that the health and safety of the public was not affected by this incident.

8001140 $ %

9 Corrective Action:

The process line was promptly thawed and insulation was placed around the wire connection tees of the Dekoron heat tracing lines. The level instru-mentation was checked and verified operable. The insulation surrounding the process lines has also been examined..

, The present Dekoron heat tracing system surrounding the process lines will be replaced by a Nelson heat tracing system b/ October 3, 1977. The new

. system will add an extra emergency heat trace line on the piping which will be powered by a separate power supply. In addition, a cold weather checklist has been created. The checklist requires inspection of the insu-lation on the impulse lines and heat tracing of the BWST level instrumenta-tion when the temperature is below 350F.

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