ML20086S963

AO-S2-74-03:on 740618,periodic Boric Acid Sample Determined Concentration in Boron Injection Tank & Boric Acid Storage Tank C to Be 10.7 & 10.8 Weight %,Respectively.Caused by Leakage Through Valves on Inlet Side of Tank

ML20086S963
Person / Time
Site:	Surry
Issue date:	07/12/1974
From:	Sstallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
AO-S2-74-03, AO-S2-74-3, NUDOCS 8403060057
Download: ML20086S963 (5)

Text

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e e-t!:4 VIRGINI A EI.ECTHIC AND POWER COh!PANY gh f 1 i T',r Ric u >t own. Vi noixtA cocot ,

July 12, 1974 2 h, ,

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H ru Hr. Norcan C. Mouc1cy, Director Serial Ho. 198 Diroctorate of Rei;ulatory Operations POSH /JTB:civ United States Atcaic Energy Corr.iocion i Rogica II - Suito 818 Docket No. 50-281 230 Peachtrao Street, Northwest Licenna No. DPR-37 Atlantn, Georgia .30303

Dear Mr. Mosoley:

Pursuant to Surry Power Station Technical Specification 6.6.B.1, tha Virginia Electric and Pcver Ccapauy hereby cubaita forty (40) copics of Abnormal Occurrence Report No. AJ-S2-74-03.

'Iha cubatanen of this report has been reviewed by the Station Nuclear Safoty and Operating Cornittee and vill be placed on the agenda for the next ineting of the Systm Zuclear 8sfety a id Opernting Committee.

Very truly youra,

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N/kW$c~<y C. M. Stallinga Vice President-Povar Supply 4 and Production Operations Enclocurca -

40 copies of A0-S2-74-03.

cc: lir. K. R. Coller, Assistent Director for Operating Reactors

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N bbO'I 8403060057 740712 ('1/./!*

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. s_/ V ABNORMAL OCCURRENCE REPORT REPORT NO. A0-S2-74-03 DILUTION OF BORON INJECTION TANK CONTENTS BELOW TECHNICAL SPECIFICATION LIMIT JUNE 18, 1974 DOCKET NO. 50-281 LICENSE NO. DPR-37 SURRY POWER STATION VIRGINIA ELECTRIC AND POWER COMPANY I

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• G G I. INTRODUCTION In accordance with Technical Specification 6.6.B.1 for Surry Power Station, Operating License No. DPR-37, this report describes an abnormal occurrence which was identified on June 18, 1974. The Directorate of .

Regulatory Operations, Region II, was notified on June 19, 1974.

The incident reported herein is classified as an abnormal occurrence pursuant to Technical Specification 1.0.I.2 which states that: "An abnormal occurrence is defined as: Any unit condition that results in -

violation of a limiting condition for operation as established in these s Technical Specifications." ,

11.

SUMMARY

OF OCCURRENCE Prior to the occurrence, Unit No. 2 was operating at 50 per ceng of rated over. Boric acid tank "C" was serving Unit No. 2 and tank "B" was not assigned.

A periodic boric acid sample taken at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br /> to determine the concentration in the boron injection tank and the "C" boric acid storage tank (which was lined up to the injection tank) indicated (

m that the respective boron concentrations were 10.7 and 10.8 weight q,.

per cent. Technical Specification 3.3.A.3 and 3.2.C.3 require the injection tank and the boric acid storage tank to be maintained between 11.5 and 13 weight per cent boric acid solution.

An orderly unit shutdown was initiated at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br />, while a DA .

new batch of boric acid solution was prepared in the batching tank. , .

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13 The batched solution was used to restore the required boron con- s .\{ / pJ 7

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centration in the two tanks. Sampling of both tanks at 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> L',

indicated a concentration of '11.7 per cent which is within the .

Technical Specification lin.its. The unit shutdown was then terminated

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and the return to power.was initiated. '

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III.ANALYS1SOFTHEOCCURRENCE e T

, The dilution of the boron injection tank was caused by leakage

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,s through one, or both, of the valves on the inlet side of the boron s (

Tinjc'c ion tat &., MOV 2867A and B. These valves are normally closed and operbautomatically upon receipt of a safety injection signal.

The valves are exposed to the discharge pressure of the charging

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pumps'..,(one,of which was running). The leakage through these valves

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I is primary coolant from the volume control tank (VCT) and contains the same boron co.ncentration as the RCS reactor coolant system-which was men ured to be 035 ppm, which is considerably less than the  ;

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approximately 20,000, ppm concentration in the boron injection tank'.

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i The "C"goric acid tank, which was assigned to Unit No. 2 and 4

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lined up with the boron' injection tank, also became diluted due.to I

T the recirculation flow between the two tanks. s I1 f r.

1 IV. ANALYSIS AND EVALUATION OF THE SAFETY IMPLICATIONS OF THE OCCURRENCE l

x :f y j The charging pumps'aormally take'suctionifrom the VCT to provide make-up'to the reactor coolant system through the charging line. Normally, only ona . (1) ' pump: runs. at a : time. The initiation w

t of fa safety, inj ction signal causes' the line up of the suction of -

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'o l the charging pumps to be diverted from the VCT. to the refueling i

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water storage tank (RWST) andrtha flow'is diverted.from the normal

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charging pa,th to the ' reactor [ coolant system yiaJthe b5ron ' injection: ,

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\l 1 ccident assumes'20,000'ppmL 4 Tne analysis 1of a steasAline trea p% ,

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e bolon) con' centration . in ' the boron ' injection ' tank'.

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. l boric acid- solution ensures; the shutdown: of; the freactor,' even in

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g the event one control cod remains stuck out of the core. The dilution of this solution would degrade the ability of the system to provide adequate shutdown margin. However, at this time in core life, with the reduced moderator temperat e coefficient, in the unlikely event of a safety injection, the reactor would have been maintained in a safe condition even with the reduced concentration in the boron in-jection tank. ,

The contents of the boric acid tank are used to maintain the concentration of the injection tank, and to borate the reactor core to -10 per cent AK/K. Although the concentration of the tank became lower than the technical specification limit, the actual volume of the tank was such that the total boron available was sufficient to meet the shutdown requirements.

V. CORRECTIVE ACTIONS TO PREVENT RECURRENCE The leaking valves have been refurbished. Increased surveillance, including monitoring of boric acid tank 1cvel and boron concentration and sampling, will be instituted whenever the valves are operated or maintenance is performed to assure there is no significant leakage.

VI. CONCLUSIONS The licensee concludes that:

1. The dilution of the boron injection tank was caused by leakage through its inlet isolation valves.

2. The occurrence described herein did not affect the safe operation of the station.

3. The occurrence described herein did not adversely affect the health or safety of thr-general public.