05000219/LER-1982-021, Forwards LER 82-021/01T-0.Detailed Event Analysis Encl

Forwards LER 82-021/01T-0.Detailed Event Analysis Encl

ML20052E646
Person / Time
Site:	Oyster Creek
Issue date:	05/03/1982
From:	Fiedler P GENERAL PUBLIC UTILITIES CORP.
To:	Haynes R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20052E647	List: 05000219/LER-1982-021, Forwards LER 82-021/01T-0.Detailed Event Analysis Encl
References
NUDOCS 8205110305
Download: ML20052E646 (4)

LER-1982-021, Forwards LER 82-021/01T-0.Detailed Event Analysis Encl

Event date:
Report date:
2191982021R00 - NRC Website

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GPU Nuclear h.'

U GM P.O. Box 388 Forked River, New Jersey 08731 609-693-6000 Writer's Direct Dial Number:

May 3, 1982 Mr. Ronald C. Haynes, Administrator Region I U. S. Nuclear Regulatory Comrnission 631 Park Avenue King o f Prussia, PA 19406 Dea r Mr. Haynes :

Subject:

Oyster Creek Nuclear Generating Station Docke t No. 50-219 Licensee Event Report Reportable Occurrence No. 50-219/82-21/01T This letter forwards three copies of a Licensee Event Report to report Reportable Occurrence No. 50-219/82-21/01T in compliance with paragraphs 6.9.2.a(2) and 6.9.2.b(2) of the Technical Specifications.

Very truly yours, Peter B. Fiedler Vice President & Director Oyster Creek

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20555 NRC Resident Inspector (1)

Oyster Creek Nuclear Generating Station Forked River, NJ 08731 8205110305 820503 PDR ADOCK 05000219 G

PDR GPU Nuclear is a part of the General Public Utihties Systern

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OYSTER CREEK NUCLEAR GENERATING STATION Forked River, New Jersey 08731 Licensee Event Report Reportable Occurrence No. 50-219/82-21/01T Report Date May 3, 1982 Occurrence Date April 16,1982 Identification of Occurrence The primary containment atmosphere was not reduced to less than 5.0% oxygen concentration within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> af ter the reactor mode selector switch was placed in the RUN mode, as required by Technical Specifications, paragraph 3.5.A.6.

This event is considered to be a reportable occurrence as defined in the Technical Specifications, paragraph 6.9.2.a(2).

Additionally, due to the delay in inerting the containment, the Drywell-Suppression Chamber dif ferential pressure. limit was not established within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> af ter the mode switch was placed in the RUN mode as required by Technical S peci fications, paragraph 3. 5. A.9.a.

This event is reportable in accordance with Technical Specifications, paragraph 6.9.2.b(2).

Conditions Prior to Occurrence Po wer :

Reactor 1390 MWt Electrical 319 MWe De scription of Occurrence On Friday, April 16,1982 at 1409 hours0.0163 days <br />0.391 hours <br />0.00233 weeks <br />5.361245e-4 months <br /> (24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after placing the reactor mode selector switch into the RUN mode), the Drywell oxygen concentration was greater than 5% and the Drywell/ Torus pressure differential was less than 1 psid.

Containment inerting was in progress at the time and had been since 1650 hours0.0191 days <br />0.458 hours <br />0.00273 weeks <br />6.27825e-4 months <br /> the day before. At 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> on 4/15/82, the Torus was inerted to approximately 4.5% oxygen, there fore, inerting of the Drywell was commenced.

At approximately 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br /> on 4/16/82, an emergency nitrogen order was placed when it was realized that there was insufficient nitrogen to complete Drywell ine rting.

The inerting had been started with a level of 180 inches in the nitrogen supply tank which is above the procedure minimum for commencement of inerting of 170- inches. At 0436 hours0.00505 days <br />0.121 hours <br />7.208995e-4 weeks <br />1.65898e-4 months <br />, inerting of the Drywell was stopped l'

- because a level of 50 inches was reached in the nitrogen supply tank as a j

minimum level of 50 inches is required by procedure. At 0845 hours0.00978 days <br />0.235 hours <br />0.0014 weeks <br />3.215225e-4 months <br />, the l

nitrogen inerting system was restarted which immediately blew the rupture disc in the nitrogen supply line to the Drywell.

The rupture disc blew because of a miscommunication during the valve lineup. The rupture disc was replaced by 1045 hours0.0121 days <br />0.29 hours <br />0.00173 weeks <br />3.976225e-4 months <br /> and the inerting process was begun again at 1050 hours0.0122 days <br />0.292 hours <br />0.00174 weeks <br />3.99525e-4 months <br />.

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Licensee Event Report Page 2 Reportable Occurrence No. 50-219/ 82-21/01T At approximately 1230 hours0.0142 days <br />0.342 hours <br />0.00203 weeks <br />4.68015e-4 months <br />, the oxygen analyzer reading for the Drywell was less than 57, therefore, pressurization of the drywell was commenced. Between 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br /> and 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br />, the Drywell and Torus oxygen analyzers were recalibrated. The meters after calibration showed oxygen concentrations for the Drywell and Torus of 5.5% and 2.5%, respectively. As a result, inerting of the Drywell commenced again. At 1409 hours0.0163 days <br />0.391 hours <br />0.00233 weeks <br />5.361245e-4 months <br />, the oxygen concentration was greater tnan 5% (5.5%) in the Drywell and the Drywell/ Torus pressure differential was less than 1 psid (.54 paid).

Thus, a reactor shutdown was commenced while the inerting continued.

At 1521, the Drywell oxygen concentration was 4.8% and the Drywell/ Torus pressure dif ferential was 1.31 psid which were within the acceptable ranges; therefore, the shutdown process was terminated.

Appa rent Cause of Occurrence l

The major f actors in this event were the loss of over six hours of inerting time due to insufficient nitrogen a d a blown rupture disc. The insufficient supply of nitrogen was caused by the over inerting of the Torus to 2.5%

oxygen.

(The Torus was inerted to 4.5% at 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> on 4/15/82, but when the I

analyzer was recalibrated on 4/16/82, it showed 2.5% oxygen concentration. )

The over inerting occurred because of problems associated with the oxygen analyzer system.

Another contributing factor was the inability of the nitrogen vaporizer to make up for the time lost due to the low nitrogen supply and blown rupture disc.

Analysis o f Occurrence The containment a tmosphere control system is designed to maintain an inert atmosphere within the primary containment to preclude energy releases from a possible hydrogen-oxygen reaction following a postulated loss of coolant accident (LOCA) which could jeopardize the integrity of the containment.

Conservative estimates of the hydrogen produced following the postulated LOCA with the operation of either core spray system show that the hydrogen produced from the metal water reaction would result in a hydrogen concentration of 0.4%

in the primary containment. This concentration is significantly below the concentration at which hydrogen can be ignited in air.

However, inerting of the primary containment was included in the proposed design and operation to preclude the possibility of an energy release within the primary containment from a hydrogen-oxygen reaction under more severe conditions than could be foreseen.

Maintaining the Drywell to Torus dif ferential pressure greater than 1 psid assures the integrity of the Torus when subject to post LOCA Torus hydrodynamic f orc es.

Considering that the Drywell oyxgen concentration was only slightly above 5%

and the Drywell/ Torus dif ferential pressure was less than 1 psid for a relatively short period af ter the twenty-four hour Technical Specification time limit had been reached, the safety significance is considered minimal.

u Licensee Event Report Page 3 Reportable Occurrence No. 50-219/82-21/01T

Corrective Action

Immediate corrective actions taken were to commence a reactor shutdown and continue inerting the containment. The shutdown was terminated when the containment oxygen concentration was reduced to less than 5% and the required minimum of 1 psid Drywell/ Torus differential pressure had been established.

An engineering request has been made to upgrade the oxygen analyzer systems.

In the future, the resctor will not be placed in the RUN mode until the containment is inerted to less than 5% oxygen, unless specifically authorized by the Plant Operations Director.. This restriction will remain until:

(1) more reliable oxygen monitoring instruments are installed, (2) containment inerting and vent valve opening restrictions (30%) are removed, and (3) the capacity of the nitrogen evaporators is verified to be reliable and adequate.

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