05000338/LER-1981-053-03, /03L-0:on 810710 & 12,post Reactor Trip Specific Activity Samples of RCS Indicated Dose Equivalent I-131 Level Greater than Tech Specs.Caused by Known Fuel Element Defect in Reactor Core

/03L-0:on 810710 & 12,post Reactor Trip Specific Activity Samples of RCS Indicated Dose Equivalent I-131 Level Greater than Tech Specs.Caused by Known Fuel Element Defect in Reactor Core

ML20009H596
Person / Time
Site:	North Anna
Issue date:	07/28/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20009H593	List: 05000338/LER-1981-053, Forwards LER 81-053/03L-0 05000338/LER-1981-053-03, /03L-0:on 810710 & 12,post Reactor Trip Specific Activity Samples of RCS Indicated Dose Equivalent I-131 Level Greater than Tech Specs.Caused by Known Fuel Element Defect in Reactor Core
References
LER-81-053-03L-02, LER-81-53-3L-2, NUDOCS 8108100282
Download: ML20009H596 (4)

LER-1981-053, /03L-0:on 810710 & 12,post Reactor Trip Specific Activity Samples of RCS Indicated Dose Equivalent I-131 Level Greater than Tech Specs.Caused by Known Fuel Element Defect in Reactor Core

Event date:
Report date:
3381981053R03 - NRC Website

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U.S. NUCLEAR REGULATORY COMMISSION L7CENSEE EVENT REPORT CONTROL BLOCK / / / / / / / (1)

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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

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/ On July 10, 1981 and J.11y 12; 1981, the post reactor trip specific activity samp-/

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/ ples of the reactor coolant system indicated a Dose Equivalent I-131 level great-/

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/ than the limit specified by T.S. 3.4.8.

Since the high iodine level existed for /

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/ only a short period of time and the specific activity level returned to within

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/ the T.S. 3.4.8 limit, the health and safety of the public were not affected.

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/ This event is reportable pursuant to T.S. 6.9.1.9.d and the special reporting

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SYSTEM

CAUSE

CAUSE COMP.

VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

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/ This event was caused by a known fuel element defect in the reactor core.

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/ trip conditions in the core enhanced the release of fission fragmeats to the

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FACILITY METHOD OF DISCOVERY DESCRIPTION (32)

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8108100282 810728 0F PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 PDR ADOCK 05000338 S

PDR

Virginia Electric and Power Company North Anna Power Station, Unit #1 Attachment: Page 1 of 3 Docket No. 50-338 Report No. LER 81-053/03L-0

Description of Event

On July 10, 1981, following a reactor trip from 100% power, the specific,ctivity sample of the reactor coolant showed a Dose Equivalent I-131 lesel of 1.34 microcuries/gm. On July 12, 1981, following another eactor trip from 100% power, the Dose Equivalent I-131 level reached 1.17 microcuries/gm.

In both of these events, the T.S. 3.4.8 limit f 5 1.0 microcuries/gm was exceeded. The I-131 levels and duration of the spikes are included in this report.

Probable Consequences of Occurrence The limitations on the specific activity of the primary coolant ensure that the resulting 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> doses at the site boundary will not exceed an appropriately small fraction of the Part 100 limits following a postulated accident.

Since the Dose Equivalent I-131 limit was exceedea for a short period of time and the Iodine level was monitored by sampling every 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> until the level returned to less than the T.S. 3.4.8 limit as required by the action statement, the health and safety of the public were not affected.

Cause of Event

The iodine spikes were caused by known, yet not specifically located, fuel element defects in the reactor core. Post trip conditions enhanced the release of fission fragments, specifically I-131, to the reactor coolant system which caused an increase in the coolant specific activity level.

Immediate Corrective Action

The immediate corrective action was to implement the actions required by T.S. 3.4.8.

Specifically, the level of Dose Equivalent I-131 was monitored every 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> until the level returned to less than the limit.

Scheduled Corrective Action No further corrective actions will be taken at this time.

Actions Taken to Prevent Recurrence The specific activity of the reactor coolant system will continue to be monitored as required by T.S. 4.4.8.

Generic Implications There are no generic implications associated with this event.

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Attachment: Page 2 of 3 Supplemental Information This event is reportable as a " Thirty-Day Written Report" pursuant to T.S. 6.9.1.9.d.

In addition the supplemental information required by T.S. 6.9.2 "Special Report" and 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 these events July 8, 1981 - 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> at 100% RTP July 9, 1981 - 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> at 100% RTP July 10, 1981 - 0025 Reactor Trip 0200-0800 Reactor Startup 2% to 9% RTP 0900 - 33% RTP 1000 - 64% RTP 1100 - 75% RTP 1200 - 86% RTP 1300 - 91% RTP 1400 - 98% RTP 1500-2400 - 100% RTP July 11, 1981 - 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> at 100% RTP i

July 12, 1981 - 0000-1300 - 100% RTP

~1323 - Reactor Trip 1400-1900 - 0% RTP

)

2000 - 7.6% RTP 2100 - 5.6% RTP 2200 - 11.6%'RTP 2300 - 32% RTP 2-1 2400 - 24% RTP

Attachment: Page 3 of 3 Supplemental Information (cont.)

2.

Fuel Burnup by Core Region - As of June 30, 1981:

Fuel Batch 1A3 - 16,790 MWD /MTU 3A2 - 25,179 MWD /MTU 4

- 13,286 MWD /MTU 3,278 MWD /MTU 5

Cycle 3 Burnup - 2,947 MWD /MTU 3.

Normal mixed bed demineralization 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> prior to and after each spike. Average flowrate of 82 gpm.

4.

No de-gassing operations were performed.

5.

Duration of I-131 spike:

July 10, 1981 - Post trip sample (0140) 1.34 microcuries/gm 0440 - 1.35 microcuries/gm i

0737 - 1.08 microcuries/gm

~I 1122 - 7.46 x 10 microcu-ies/gm Duration approximately 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> July 12, 1981 - Post trip sample (1435) 1.17 microcuries/gm l

1830 - 1.04 microcuries/gm l'

2235 - 0.678 microcuries/gm l

Duration approximately 11 hours1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br /> t

I