ML20080H389

Special Rept SP-N1-84-01:on 840109,following Unit Rampdown, I-131 Dose Equivalent Specific Activity Exceeded 1.0 Mci/G. Caused by Minor Fuel Element Defects in Reactor Core. Reactor Power Change Rates Administratively Limited

ML20080H389
Person / Time
Site:	North Anna
Issue date:	02/01/1984
From:	Harrell E VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
N-84-01, N-84-1, SP-N1-84-01, SP-N1-84-1, NUDOCS 8402140186
Download: ML20080H389 (6)

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s VIRGINI A ELECTRIC AND POWER COhP ANY NORTH ANN A POWER ST ATION P.O. BOX 402 MINE R A L, itRGINIA 23117 February 1, 1984 Mr. James P. O'Reilly, Regional Administrator Serial No. N-84-01 U. S. Nuclear Regulatory Commission N0/JRR: 11 Region II Docket No. 50-338 101 Marietta Street, Suite 2900 Atlanta, Georgia 30303 License No. NPF-4

Dear Mr. O'Reilly:

Pursuant to North Anna Power Station Technical Specifications, the Virginia Electric and Power Company hereby submits the following Special Report applicable to North Anna Unit No. 1.

Report No. Applicable Technical Specifications Special Report SP-N1-84-01 T.S. 6.9.2.f This report has been reviewed by the Station Nuclear Safety v.nd Operating Committee and will be forwarded to Safety Evaluation and Control for their review.

Very Truly Yours,

/*

E. Wayne e Station anager Enclosures (3 copies) cc: Document Control Desk (1 copy) 016 Phillips Bldg.

U.S. Nuclear Regulatory Commission Washington, D. C. 20555 2 Ngo[

OFFICIAL COPY w..... . 4dd "

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Virginia Electric and Power Company North Anna Pcwer Station, Unit No. 1 Page 1 of 2 Docket No. 50-338 Special Report No. SP-N1-84-01 Description of Event On January 9, 1984 at 0603 following a unit rampdown, the 1-131 Dose Equivalent specific activity exceeded 1.0 microcurie / gram. The 7

specific activity returned to within the T.S. 3.4.8 limit by 0345 on January 10, 1984. This event is reportable as a Special Report pursuant to T.S. 6.9.2.f.

l- Probable Consequences of Occurrence Primary coolant I-131 Dose Equivalent specific activity peaked at 1.64 microcurie / gram at 1110 on January 9, 1984, and returned to within limits .by 0345 on January 10, 1984. Daily samples taken prior ' to the rampdown were consistently less than 0.1 microcurie / gram Dose Equivalent I-131. The primary coolant Dose Equivalent I-131. exceeded - the 1.0 microcurie / gram limit for a time period less than or equal to 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br />.

The 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. sampling surveillance frequency required by T.S. Table 4.4-4

- was maintained throughout the event. The health and safety of the.

public were not affected.

Cause of Event t

. On January 8, 1984 at approximately 2318.. a . unit rampdown was t

initiated as a result of a suspected unidentified Reactor Coolant System leakage. greater than 1 gallon / minute. At 0516 on January 9, 1984 the turbine was manually tripped ' while the reactor .was maintained critical at 1 percent power. The reactor was maintained at this power level until 2200 when it was shutdown by manually inserting control rods.

The increase in Dose Equivalent..I-131 activity occurred as,a result-

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of known, _but not specifically identified, minor fuel element defects present in-the reactor core. The diffusion of -iodine into the reactor-coolant was enhanced. by the rapid decrease in L reactor power. Iodine spiking with power changes is a well documented and accepted phenomenon.

Immediate Corrective Action  !

.The primary coolant ~ was - sampled and analyzed at the accelerated frequency required by . Item 4a - of Technical Spacification ' 3.4.8, ' Table 4;4-4.

l Scheduled Corrective Action l ~

(- None are required.

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1 Special Report SP-N1-84-01 Page 2 of 2 Action Taken To Prevent Recurrence Iodine spiking from minor fuel defects following rapid power.

changes is expected. Unit I reactor power change rates during normal

- operation -have been administratively limited to reduce the probability of recurrence.

Generic Implications

-Iodine spiking as a recurring phenomenon in Unit 1 and has been

. previously reported.

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Attachment:

Page 1 of 3 Supplemental Information This event is reportable as a "Special Report" pursuant to T.S.

6.9.2. In addition the supplemental information required by T.S. 3.4.8 is included as follows:

1. Reactor Power History 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> prior to the event:

DATE TIME POWER MWe COMML'NTS 01-06-84 0000-2400 100% 940 a 01-07-84 0000-2200- 100% 940 a 01-08-84 0000 93% 877 b 01-08-84 0100 91.5% 866 b 01-08-84 0300 98.2% 921 b 01-08-84 0500-2300 100L 940- a 01-09-84 0000 92% 869 c 01-09-84 0300 42.1% 376 c 01-09-84 0511 5.4% 24 c 01-09-84 0521 1.0% 0 J 01-09-84 1200 1.0% 0 e-01-09-84 2151 1.0% 0 f 01-09-84 2200 0% 0 .g a) Steady state power operation.

b) -Reactor / Turbine power decrease. in order- to perform Turbine Valve Freedom Test.

c) Began rampdown at 2318 due to _ suspected Unidentified

. Reactor Coolant System leakage >1.0 gallon / minute.

d) Turbine manually tripped at 0516 while maintaining reactor critical in Mode 2.

e) Reactor maintained critical in Mode 2.. '

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Attachment:

Page 2 of 3 f) Reactor shutdown commenced by manually inserting control rods.

g) Reactor shutdown.

2. Fuel Bernup by Core Region - As of January 8,1984:

FUEL BATCH BURNUP (MWD /MTU) 4A2 32,092.9 5A 25,186.7 6A 11,027.5

3. One edxed bed demineralizer was in service from 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> prior to the event until 1615 on January 8, 1984. At that time the demineralizer was bypassed in an effort to locate the cause of the unidentified RCS leakage. The demineralizer was returned to service at 2325 on January 8, 1984 and remained in service during and following the event. The average flowrate throuth the demineralizer when it was inservice was 127 gpm.

4. No de-gassing operations were performed.

5. Duration of Dose Equivalent I-131 above 1.0 microcurie / gram:

DOSE EQUIVALENT DATE TIME I-131-(MICR0 CURIES / GRAM) 01-07-84 0212 0.0769

, 01-08-84 0148 0.0985 01-09-84 0158 0.176 01-09-84 0603 1.14 01-09-84 0915 1.53 01-09-84 1110 1.64

.01-09-84 '1355' 1,41

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4 Atta-hment: Page 3 of 3 01-09-84 1545 1.16 01-09-84 1945 1.24 01-09-84 2345 1.10 01-10-84 0345 0.989 01-10-84 0742 0.844 01-11-84 0052- 0.413 l

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