ML20086D421

AO 50-261/76-3:on 760128,high Level Alarm Received on Safety Injection Accumulator B.Caused by Check Valve 875 Leaking Resulting in Dilution.Accumulator Partially Drained & Refilled

ML20086D421
Person / Time
Site:	Robinson
Issue date:	02/09/1976
From:	Mcgirt J, Utley E CAROLINA POWER & LIGHT CO.
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20086D424	List: ML20086D421 ML20086D427
References
AO-50-261-76-3, NG-76-177, NUDOCS 8312010466
Download: ML20086D421 (3)

Text

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February 9, 1976 File: NG-3513 (R) Serial: NG-76-177 Mr. Norman C. Moseley, Director U. S. Nuclear Regulatory Commission Region II, Suite 818

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Dear Mr. Moseley:

A.,g f* 0/ A H. B. ROBINSON UNIT NO. 2

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DOCKET 50-261 yf // LICENSE NO. DPR-23 BORON CONCENTRATION BELOW LIMITS IN Q

                              "B"  SAFETY INJECTION ACCUMULATOR In accordance with 6.6.2.a of the Technical Specifications for H. B. Robinson Unit No. 2, the attached Abnormal Occurrence is submitted for your information.           This report fulfills the' requirement for a written report within ten days of an Abnormal Occurrence and is in accordance with the format set forth in Regulatory Guide 1.16, Revision 1.

Yours very truly, 7 /

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Vice President Bulk Power Supply CSB:jwk Attachment cc: Messrs. D. C. Knuth W. G. Mcdonald l 8312010466 760209 PDR ADOCK 05000261 a ceLU n S PDR .Lv

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v .O . Abnormal Occurrence Recort

1. Report No. 50-261/76-3 2a. Report Date February 4, 1976 2b. Occurrence Date January 28, 1976

3. Facility H. B. Robinson Unit No. 2 s Hartsville, South Carolina 29550

4. Identification of Occurrence t

I While operating at.100% power a high level alarm was received on "B" Safety Injection Accumulator. The level was lowered and subsequent sampling revealed the boron concentration to be below limits. This constitutes a violation of Technical Specification 1.8.d.

5. Conditions Prior to Occurrence The reactor was operating at 100% power with all conditions normal.

6. Description of Occurrence At 2140 hours a high level alarm was received on "B" Safety Injection Accumulator. The accumulator was drained from 80 to 77% at 2143 hours and a boron sample taken. Result of the sample at 2155 hours was 1939 ppm which is below the 1950 ppm minimum requirement. The sample was verified at 2205 hours to be 1942 ppm.

7. Designation of Aoparent Cause of Occurrence "B" Safety Injection Accumulator check valve 875E was determined to be leaking through slightly, resulting in dilution. As the inleakage resulted in small level increases, operators adjusted the level by equalization with other accumulators, resulting in dilution of the accumulation with reactor-coolant at a very gradual rate.

8. Analysis of Occurrence There were no personnel injurisa, nor was there.a release of radioactive materials involved in this occurrence.

A maximum of 11 ppm boron below Technical Specification was experienced.

                    "A" and "C" Accumulator were 2345 and 2337 ppm, respectively. Resultant reduction in shutdown capability in the event of accumulator discharge would have been insignificant.          "B" Accumulator boron concentration was adjusted and returned to within specification in one hour and twenty minutes. One accumulator may be isolated for four hours per Technical Specification 3.3.1.2.a.

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9. Corrective Action .

The accumulator was partillly d, rained and refilled from the refueling water storage, tank twice. .fhe first evolution resulted in an' increase in boron concentration to.1981 ppm at 2315 hours. The second drain and

                    " refill' sample was 2017 ppm boron.

Repair of the leaking check valve will require primary system depressuri-zation and flushing the seat or complete draindoun and disassembly. In the meantime, accumulator horon sanples will be taken daily (6-days a week) for'two weeks to develop the' dilution trend, then three cines a week until repairs are implemented. Operating personnel have been in-structed to drain and refill the accumulator when boron concentration is reduced te-2050 ppm. All level adjustments are to be documented in the operator's log.

10. Failure Data 4

1. December 11, 1975 "B" Safety Injection Accumulator boron out i of specifications low due to dilution.

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