ML20084C535

AO 251-74-6:on 741013,analysis of Boron Injection Tank Boron Content Revealed Concentration Below Tech Spec Limit.Caused by Insufficient Recirculation Coupled W/Minor Inleakage. Boron Injection Tank Recirculated

ML20084C535
Person / Time
Site:	Turkey Point
Issue date:	10/23/1974
From:	Schmidt A FLORIDA POWER & LIGHT CO.
To:	Case E Office of Nuclear Reactor Regulation
References
AO-251-74-6, NUDOCS 8304080096
Download: ML20084C535 (3)

Text

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g P.O. MX 3500 MIAMS, FLOelDa $3501 NN FLORIDA POWER & UGHT COMPANY October 23, 1974 Mr. Edson G. Case, Acting Director Directorate of Licensing Office of Regulation U. S. Atomic Energy Commission Washington, D. C. 20545

Dear Mr. Case:

ABNORMAL CCCURRENCE NO. 251-74-6 OCTOBER 23, 1974 OCCURRENCE DATE: OCTOBER 13, 1974 TURKEY POINT UNIT NO. 4 '

BORON INJECTION TANK BORON CONCENTRATION BELOW LIMITING CONDITION FOR OPERATION A. Condition Prior to Occurrence:

The reactor was in routine power operation at 98% power.

B. Description of Occurrence:

At 2:46 P.M. on October 13, 1974, analysis of the Unit No. 4 Boron Injection Tank (BIT) boron content revealed that the concentra. in as measured at the inlet sample point was 19,100 ppm. This was below the Technical Specification lower limit of 20,000 ppm.

The contents of the BIT are recirculated daily through the boric acid storage tank to assure that the boron concentration of the tank is not degraded by minor inleakage of water.

During the recirculation, it was noted that no flow was indicated on the recirculation line flow indicator. Investigation re-vealed that the flow indicator was operable and there was no flow. The Plant Supervisor determined that it was necessary to sample the boron injection tank to assure that the boron concentration had not been degraded. This sampling revealed that while the outlet sample point provided an acceptable concentration of 20,600 ppm boron, the inlet sample point was 19,100 ppm. A resample of the inlet verified the low concentra-tion.

The BIT is routinely sampled for boron concentration twice a month as opposed to the monthly requirement of the Technical Specifications. In addition, it is sampled before and after 8304080096 741023 DR ADOCK 05000 g,

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o Mr. Edson G. Case, Acting Director Page Two

. October 23, 1974 1

4 i running the Safety Injection System monthly test. Sampling l

for the latter reason was performed on October 3, 1974. The

results were 21,600 ppm and 21,300 ppm boron respectively.

, Performance of the routine sampling on October 2, 1974, showed a concentration of 21,100 ppm boron.

) C. Cause of the Occurrence:

i

The investigation to determine the cause of the occurrence has revealed that the dilution is due to insufficient recircula-J tion coupled with minor inleakage. The contents of the boron injection tank could not be sufficiently recirculated because i of a blocked or partially blocked recirculation supply line to

, the boric acid storage tank.

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{ D. Analysis of the Occurrence:

The role of the boron injection tank is to provide a source of negative reactivity to alleviate the consequences of the postulated steam break accident described in the FSAR. The safety analysis is conservative in that credit is only taken

for the amount of boron in the boron injection tank itself and no credit is taken for the amount of boron in the safety injection system piping. In addition, the actual rate of boron 4

injection, in the unlikely event of a steam break, would be j greater than utilized in the FSAR because actual safety injec-

, tion flow rates would be higher than those analyzed in the FSAR. These factors coupled with the amount of dilution that

- occurred indicate that the consequences of a steam line break would have been within the limits presented in the FSAR. There-fore, neither reactor safety nor the health and safety of the public were jeopardized by this occurrence.

E. Corrective Action:

The immediate corrective action consisted of: 1) Initiating an orderly reactor shutdown, and 2) Initiating recirculation of the boron injecticn tank through a boric acid storage tank utilizing a temporarf line connected between the two tanks.

' Daily sampling of the tank was maintained while the temporary recirculation line w6s utilized.

A BIT concentration cf >20,000 ppm was achieved before reaching shutdown, and the reactor was returned to normal power opera-i .

tion' .

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The recirculation line was unplugged and returned to service, f

However, as a precautionary measure, the frequency of recirculating

. %the contents of the boron injection tank has been increased.

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Mr. Edson G. Case, Acting Director l Page Three-October 23, 1974 Evaluation of the boron injection tank concentration problem and methods of recirculation and sampling was initiated as,a result of a similar abnormal occurrence on June 27, 1974 (see Failure Data), and is continuing.

F. Failure Data:

This is the second abnormal occurrence at Turkey Point result-ing from a blocked boron injection tank recirculation line.

The first occurrence was reported on July 5, 1974, as Abnormal Occurrence No. 251-74-1.

Very truly yours, i ee L 1.

yh A. D. chmidt' Y^

Director of-Power Resources DWR/cpc cc: Mr. Norman C. Moseley Jack R. Newman, Esquire l

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