ML19346A364

LER 81-043/03L-0:on 810521,boron Concentration in Refueling Water Storage Tank Fell Below Tech Spec Limit.Caused by Dilution from Returning RCS Water to Tank Following ECCS Flowpath Test.Blended Makeup Performed to Tank

ML19346A364
Person / Time
Site:	North Anna
Issue date:	06/15/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19346A362	List: ML19346A361 ML19346A364
References
LER-81-043-03L, LER-81-43-3L, NUDOCS 8106190216
Download: ML19346A364 (3)

Text

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dllk' U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT CONTROL BLOCK /_/ / / / / / (1) (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

[0[1[ -[V/A/N/A/S/2/ (2) /0/0/-/0/0/0/0/0/-/0/0/ (3) /4/1/1/1/1 (4) / / / (5)

LICENSEE CODE L" CENSE NUMBER LICENSE TYPE CAT

/0/1/ REP 0R g [L (6) -/0/5/0/0/0/3/3/9/ (7) /0/5/2/1/8/1/ (8) /0/6/1/5/9/1/ (9)

DOCKET NUMBER EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES (10)

/0/2/' / On May 21, 1981, during Mode 1 operation, it was determined that the boron con- /

/0/3/ / centration in the Refueling Water Storage Tank (RWST) had fallen below the T.S. /

'/0/4/ / 3.5.5 limit of 2000 ppm (1958 ppm). Since the concentration was restored to /

/0/5/ / greater than 2000 ppm within the time required by the act,<n statement, the '/

/0/6/ / health and safety of the public were not affected. This event is reportable /

/0/7/ / pursuant to T.S. 6.9.1.C.b. /

/0/8/ / /

SYSTEM CAUSE- CAUSE COMP. VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE

/p/9/ /S/H/ (11) /A/ (12) [A/ (13) /Z/Z/Z/Z/Z/Z/ (14) [Z/ (15) [Z/ (16)

SEQUENTIAL OCCURRENCE REPORT REVISION LER/R0 EVENT YEAR REPORT NO. CODE TYPE NO.

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(17) REPORT ___

NUMBER /8/1/ /-/ /0/4/3/ /\/ /0/3/ /L/ L-[ [0/

ACTION FUTURE EFFECT SHUTDOWN AITACHMENT NPRD-4 PRIME COMP. COMPONENT TAKEN ACTION ON PLANT METHOD HOURS SUBMITTED FORM SUB. SUPPLIER MANUFACTURER

/X/ (18) /X/ (19) /Z/ (20) /Z/ (21) /0/0/0/0/ (22) [Y/ (23) /N/ (24) /A/ (25) /Z/9/9/9/-(26)

CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27) 4

/1/0/ / The dilution of the RWST was caused by returning RCS water to the-RWST following /

/1/1/ / a test of the ECCS flowpath. The si.tuation was further complicated by an inade- /=

/1/2/ / quate boric acid make-up and non-representative chemistry samples. The concen- / ~

[1/3[ / tration was restored by performing a blended make-up to the RWST. /

/1/4/ / /

FACILITY METHOD OF STATUS  % POWER OTHER STA*US DISCOVERY DISCOVERY DESCRIPTION (32)

/1/5/ [El (28) /1/0/0/ (29) / NA / (30) /B/ (31) / OPERATOR OBSERVATION /

ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITY (35) LOCATION OF RELEASE (36)

/1/6/ /Z/ (33) /Z/ (34) / NA / / NA /

PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION (39)

/1/7/ /0/0/0/ (37) /Z/ (38) / NA /

PERSONNEL INJURIES NUMBER DESCRIPTION (41) l /1/8/ /0/0/0/ (40)'/ NA /

LOSS TYPE OF OR DAMAGE TO FACILITY (43)

DESCRIPTION

/1/9/ /Z/ (42) / NA /

PUBLICITY ISSUED DESCRIPTION (45) NRC UbE ONLY

/2/0/ /N/ (44) / NA /////////////

NAME OF PREPARER W. R. CARTWRIGH' PHONE (703) 894-5151 8.10 61*S 08/ b

>/ - s di Virginia Electric and Power Company North Anna Power Station, Unit 2

Attachment:

Page 1 of 2  :

Docket No. 50-339 '

Report No. LER 81-043/03L-0 Description of Event On May 21, 1981 it was determined that the RWST boroc concentration was 1950 ppm. The T.S. 3.5.5 requires that the minimum concentration in the RWST, while in Modes I through 4, be greater than 2000 ppm. Samples taken following the ECCS test showed an adequate boron concentration in the RWST. Samples taken several days later showed low boron concentration in the RWST after complete mixing had occurred. Subsequent boration of the RWST restoted the concentration to greater than 2000 ppm as verified by reanalysis within the time specified by T.S. 3.5.5.

Probable Consequences of Occurrence Boron is maintained in the RWST to iasure that the reactor will remain suberitical, in the iold condition following a LOCA. Since the required concentration was restored within the time required by the action statement, the health and safety of the public were not affected.

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Cause of Event -~

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The cause of the RWST dilution was initia'te'd by a flow test from the RWST via the LHSI pumps to the Reactor Coolant System to verify the operability of the ECCS flow-path. After completing this test, the RCS water, (approximately 10,000 gal with 1500 ppm Boron) was returned to the RWST via the RHR system. This occurred while in Mode 5. Prior to entry into Mode 4, the RWST was borated using a blended make-up to restore concentration to greater than 2000 ppm. However, the calculation ,

to determine the blanded make-up necessary to achieve 2000 ppm was based ,

on graphs that were inaccurate for the range used. Following the completion of the boration, the concentration measured, showed 2063 ppm boron. The boron sample was not representative of tank contents since the RWST volume had not thoroughly mixed. __

The unit entered Mode 1 operation on May 20, 1981. The boron analysis on May 21, 1981 showed that the boron concentration was actually 1958 ppm. This decrease occurred when the RWST became properly mixed.

s Immediate Correceive Action The RWST boron concentration was restored by performing a blended make-up. This corrective action was verified by reanalysis after properly recirculating the tank.

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Attachment:

Page 2 of 2 Scheduled Corrective Action No scheduled corrective action. <

Actions Taken to Prevent Reccurrence At the present time, a change to the Technical Specification limits on RWST- boron concentration is under review. In addition, following changes in water volumes to the RWST, samples will not be taken ur.til the RWST is thoroughly mixed. ,

Generic Implications This event is generic to North Anna Units 1 and 2.

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