05000219/LER-1981-014, Forwards LER 81-014/01T-0.Detailed Event Analysis Encl

Forwards LER 81-014/01T-0.Detailed Event Analysis Encl

ML19347E310
Person / Time
Site:	Oyster Creek
Issue date:	04/15/1981
From:	Finfrock I JERSEY CENTRAL POWER & LIGHT CO.
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19347E311	List: 05000219/LER-1981-014, Forwards LER 81-014/01T-0.Detailed Event Analysis Encl 05000219/LER-1981-014-01, /01T-0:on 810401,containment Oxygen Concentration Was Not Reduced to Less than 5% within 24-h After Placing Reactor Mode Switch in Run.Caused by Inerting at Significantly Reduced Rates
References
NUDOCS 8104240558
Download: ML19347E310 (4)

LER-1981-014, Forwards LER 81-014/01T-0.Detailed Event Analysis Encl

Event date:
Report date:
2191981014R00 - NRC Website

text

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Q OYSTER CREEK NUCLEAR GENERATING STATION c%.~'*J c,gga$?"1bc uum sa.m (609)693-6000 P.O. BOX 388

• FORKED RIVER

• NEW JERSEY

• 08731 c

April 15, 1981 r. - n I =j s.1 4

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Mr. Boyce H. Grier, Director y

Office of Inspection and Enforcement 7

Region I

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United States Nuclear Regulatory Ccmnission p'

631 Park Avenue gr King of Prussia, Pennsylvania 19406

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Dear Mr. Grier:

SUBJECT: Oyster Creek Nuclear Generating Station Docket No. 50-219 Licensee Event Report Reportable Occurrence No. 50-219/81-14/01T-0 This letter forwards three copies of a Licensee Event Report to report Reportable h ence No. 50-219/81-14/0lT-0 in cmpliance with paragraphs 6.9.2.a(2) and 6.9.2.b(2) of the Technical Specifications.

Very truly yours, MP#

Ivan R. Finf J

Vice President - JCP&L Director - Oyster Creek IRF:dh Enclosures cc: Director (40 copies)

Office of Inspection and Enforement United States Nuclear Regulatory Comission Washington, D.C.

20555 Director (3)

Office of Managment Infonnation and Program Control United States Nuclear Regulatory Camtission Washington, D. C. 20555 NRC Resident Inspector (1)

Cyster Creek Nuclear Generating Station Forked River, N. J.

8104OA -

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.i OYSTER CREEK NUCIEAR GENERATING STATION Forked River, New Jersey 08731 Licensee Event Report Reportable Occurrence No. 50-219/81-14/0lT-0 Report Date April 15, 1981

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Occtutarca Date April 1, 1981 Identification of Occurrence The primary contairmEnt atRosphere 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 /> after the reactor mode selector switch was placed in the PUN mode as required by Technical Specifications paragraph 3.5.A.6.

'Ihis 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 conhirmmt, the Drywell-Suppression Chamber differential 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 /> after the mode switch was placed in the BUN mode as required by Technical Specificaticr.3 paragraph 3.5.A.9.a.

This is considered a limiting condition for operation reportable in accordance with Technical Specifications, paragraph 6.9.2.b(2).

Conditions Prior to Occurrence Load Changes during Boutine Power Operations Plant parcaeters at the time of oaurrence were:

Power:

Reactor 1484 MWt Electrical 473 NNa Flow:

Recirculation 12.2 x 104 p Feedwater 5.4 x 106 lb/hr Description of Occurrence On Wednesday, April 1,1981, at approximately 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-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 switch in FUN) the Drywell and Torus oxygen concentrations were greater than 5.0%. (5.1% and 3.4% respectively).

Contalment inerting was in progress at the time and had been since about 0710 l

hours that day. While inerting the Torus it became necessary to reduce the l

Nitrogen flow significantly since it was observed that the Torus was pressurizing.

Inerting was shifted over to the Drywell at about 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> when the Torus l

~ Oxygen concentration indicated less than 5%. A ealibration of the 'Ibrus Oxygen analyzer was performed which indicated 4% oxygen in the Torus.

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Reportable Occurrence Page 2 Report No. 50-219/81-14/OlT-0 Drywel: inerting was not affected by venting problems, however, the purge rate was limited by Nitrogen temperature at the purge inlet due to a faulty block of heaters in the Nitrogen vaporizer.

During this time it was noted that the Torus oxygen concentration was rising slowly and had exceeded 5%.

At 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> with Drywell Oxy-gen concentration indicating 5.1% and Torus Oxygen concentration indicating 5.4% a reactor shutdown was commenced while inerting con-tinued.

At 2054 hours0.0238 days <br />0.571 hours <br />0.0034 weeks <br />7.81547e-4 months <br /> both Drywell and Torus oxygen concentrations were below 5% and the Drywell to Torus differential pressure had been established within the acceptable range at which time the shut-down was terminated.

Apparent Cause of Occurrence The major contributing factor in this event was the inability to vent the Torus fast enough during inerting.

The purge rates were significantly restricted, in order to avoid pressurizing the Torus, which extended the inerting process.

Since the Drywell was vented without experiencing similar difficulties it is believed that the Torus vent valves V-28-17 and V-28-18 are suspected as being the source of the problem.

These valves were among those modified, during the 1980 refueling outage, to restrict their opening to less than 30 degrees.

Another contributing factor was that the Nitrogen vaporizer was operating in a reduced status; possibly with up to half of the heaters inoperable or having faulty elements.

This, independent of venting problems, necessitated restricting the purge rate to maintain accept-able Nitrogen temperatures at the purge inlet.

The delay in commencing inerting after placing the mode switch in l

RUN was caused by several events.

A drill required as part of im-l plementing the new Emergency Plan was held after the plant reached a stable condition.

The drill preparation, conduct, and recovery de-i layed other plant operations until after midnight on March 31.

A i

test necessary to determine whether a primary relief valve was leak-ing slightly had to be performed three times before the valve seated satisfactorily.

After the relief valve test, a surveillance of pri-mary containment vacuum breakers was required before power increase could continue.

The test was completed by 0615 and preparations for inerting were begun.

l l

Analysis of Occurrence l

l The containment atmosphere 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 postu-l l

E

i R:portablo Occurrencs Page 3 Report No. 50-219/81-14/0lT-0 lated loss of coolant accident which could jeopardize the integrity of the containment.

Conservative estimates of the hydrogen pro-duced following the postulated loss of coolant accident with the operation of either core spray system show that the hydrogen pro-duced from the metal-water reaction would result in a hydrogen con-centration 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 pos-

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sibility of an energy release within the primary containment from a hydrogen-oxygen reaction under more severe conditions than could be foreseen.

In addition, considering that the Drywell and Torus Oxygen concen-trations were only slightly above 5% for a relatively short time the safety significance is considered minimal.

Corrective Actions

Immediate corrective actions taken were to commence a reactor shut-down and continue inerting the containment.

The shutdown was ter-minated when the containment oxygen concentration was reduced to less than 5% and the required Drywell to Torus differential pressure had been established.

Future corrective actions will include checking the opening stroke of the Torus vent valves V-28-17 and V-28-18 during the next scheduled outage and repairing the vaporizer heater block prior to the next startup.