ML20042E534

Special Rept 1-SR-90-005-00:on 900404,positive Moderator Temp Coefficient Noted During Low Physics Testing Due to High Boron Concentration in Moderator.Rod Withdrawal Limits Imposed Per Tech Spec 3.1.1.3a,Action a.1

ML20042E534
Person / Time
Site:	Comanche Peak
Issue date:	04/16/1990
From:	Guldemond W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	Martin R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
1-SR-90-005-00, 1-SR-90-5, TXX-90147, NUDOCS 9004230549
Download: ML20042E534 (4)

Text

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I.""". .- Lo # TXX 90147

" "" " "l: F1 e # 10250 C. = 903.1 2 C 904.2 nlELECTRIC 904 3 Ref. # 10CFR50.36(c)(5)

I,$,%3i[,*f,'l,i'; Apr11-16, 1990 Mr. R. D. Martin, Region IV U. S. Nuclear Regulatory Comission 611 Ryan Plaza, Suite 1000 Arlington, Texas 76011

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)

DOCKET NO. 50 445 POSITIVE MODERATOR TEMPERATURE LOEFFICIENT SPECIAL REPORT NO. 1-SR 90-005-00 Gentlemen:

Enclosed is a 10 day special report submitted in accordance with CPSES Unit 1 Technical Specification 3.1.1.3, " Reactivity Control Systems Moderator Temperature Coefficient."

Sincerely, By:

SilTiam G. e nd

/

Manager, Sit L ensing JRW/daj Enclosure c - Documeist Control Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Resident Inspectors, CPSES (3) 00 $bObb bO . $5 400 North Olive Street LB. 81 Dallas, Texas 75201

... Enclosure to TXX-90147 April 16, 1990 i Page 1 of 3 l TU Electric  !'

Comanche Peak Steam Electric Station, Unit 1 Docket No. 50-445 i Positive Moderator Temperature Coefficient I

Special Report No. 1-SR-90-005-00 t

1.0 REPORT REQUIREMENT This Special Report is submitted in accordance with )

Comanche Peak Steam Electric Station (CPSES) Unit 1  ;

Technical Specification 3.1.1.3a., ACTION a.3 and ,

Specification 6.9.2. Specification 3.1.1.3a, ACTION a.3 l allows operation in Modes 1 and 2 to proceed with a Moderator Temperature coefficient (MTC) more positive than the limit of Specification 3.1.1.3a provided a Special {

Report is prepared and submitted to the Commission within- ,

10 days, describing the value of the measured MTC, the  !

interim control rod withdrawal limits, and the predicted f

average core burnup necessary for restoring the positive-MTC to within its limit for the all rods withdrawn t condition. Specification 3.1.1.3a requires the MTC to be l less positive than 0 /S k/k/ degrees F for the1all rods j withdrawn, beginning of cycle life, hot zero THERMAL POWER condition in Modes 1 and 2.

2.0 EVENT DESCRIPTION ,

On April 4, 1990, during low power physics testing in Mode -

2 for the initial fuel cycle of CPSES Unit 1, the.MTC was-measured pursuant to Technical Specification 4.1.1.3a. The measured value of the MTC was positive 0.835 percent millirho/ degrees F (or 8.35 E-6 es k/k/ degrees F) . Special Test Exception (STE) 3.10.3 was in effect at the time of the MTC measurement. STE 3.10.3 suspended-the Limiting Condition for Operation of Technical Specification 3.1.1.3a requiring a negative MTC.

k 3.0 CAUSE OF EVENT The reactor core contained more excess reactivity than design calculations predicted. As a_ result, the critical e all rods out configuration required more boron to suppress '

this excess reactivity. This resulted in a positive-moderator temperature coefficient due to.the high boron '

concentration i.n the moderator. ,

1

... Enclosure to TXX-90147 April 16, 1990 Page 2 of 3 4.0 CORRECTIVE ACTIONS Rod Withdrawal Limits (RWLs) were imposed pursuant to Technical Specification 3.1.1.3a, ACTION a.1. to establish and maintain a negative MTC. A copy of the Rod Withdrawal Limits is attached.

The RWLs shall remain in effect until a subsequent calculation verifies that the MTC has been restored to within its limits for the all rods out, hot zero power, xenon free condition. The predicted core average burnup required to restore the MTC to its limit is 4450 MWD /MTU.

I

Rod Withdrawal Limits  ;

CPSES Unit 1, Cycle 1 Control Bank D Position (steps) 0% 10 % 20 % 30% 401 50% Power

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Boron Concentration (ppm) ";;

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