ML20084S259

AO 50-265/75-26:on 750725,oxygen Level of Unit 2 Suppression Chamber Exceeded Tech Spec Limit.Caused by Insufficient Nitrogen Available to Inert Primary Containment Due to Leaking Flange.Gasket in Nitrogen Line Replaced

ML20084S259
Person / Time
Site:	Quad Cities
Issue date:	08/04/1975
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Office of Nuclear Reactor Regulation
Shared Package
ML20084S261	List: ML20084S259 ML20084S264
References
AO-50-265-75-26, NJK-75-394, NUDOCS 8306160360
Download: ML20084S259 (3)

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' .[?N Com O  ?) Quad Citi alth Edison enIrating Station O

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NJK-75-394

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August 4, 1975 f[y d;lg.;'f g/

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Director of Office of Nuclear Reactor Regulation U.S. Nuclear Fegulatory Commission Washington, D.C. 20555

Reference:

Quad-Cities Nuclear Power Station Docket No. 50-265, DPR-30, Unit 2 Appendix A, Sections 1.0.A.2., 3 7.A.5.b, 6.6.B.I.a.

Enclosed please find Abno'rmal Occurrence Report No. 50-265/75-26 for Quad- .

Cities Nuclear Power Station. This occurrence was previously reported to ,

• • Region ill, Directorate of Regulatory Operations by telephone on July 25, 1975 and to you and Region lit, Directorate of Regulatory Operations by -

telecopy on July 28, 1975 This report is submitted to you in accordance with the requirements of Technical Specification 6.6.B.I.a.

Very truly yours,

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COMMONWEALTH EDISON COMPANY ,

QUAD-CITIES NUCLEAR POWER STATION Y /d%Z/Of N.J. Kallvianakis Station Superintendent NJK/JWS/vmb cc: Region Ill, Directorate of Regulatory Operations J.S. Abel i ,

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.. .a b'. N O O REP 0AT NUMBER: A0-50-265/75-26 Nic: +:

REPORT DATE: August 4, 1975 ) 'N OCCURRENCE DATE: July 25, 1975 NA'I 1 A.; * : .:

FACILITY: Quad-Cities Nuclear Power Station Cordova, 111inois 61242 h[..

7,g IDENTIFICATION OF OCCURRENCE: -

High oxygen level in the Unit 2 primary containment.

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CONDITIONS PRIOR TO OCCURRENCE: 9. f. t i

4 Unit 2 was in the RUN mode with a power level of 1374 MWT, a load of 421 MWE, and increasing 5 9. .

load at 3 MWE/ hour. a S

=0p DESCRIPTION OF OCCURREi!CE:

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At 4:00PM on July 24, 1975, Unit 2 was put in the RUN mode. At 4:00PM on July 25, 1975, the ,

oxygen level of the Unit 2 suppression chamber was 8%, and the drywell was 5%, thus exceeding .%;. Q .7 A

Technical SpectfIcatIon 3.7.A.5.b. *%.

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

Equipment Failure - The reason for the occurrence was that insufficient nitrogen was available to inert the primary containment. The deficiency occurred because a leak had developed at a flange in the nitrogen inerting system due to a gasket failure. . This leak was of sufficient size that there was an inadequate supply of nitrogen reaching the primary containment to complete the inerting operation.

472 ANALYSIS OF OCCURRENCE:

Since the unit was operating at approximately half power, the probability of the conditions 1.- / .

existing to allow combustion of any hydrogen liberated if a gross metal-water reaction occurred  ?,

during a loss of coolant accident was very small. This probability was sma11 because the containment atmosphere had been reduced from atmospheric oxygen concentrations to 57 oxygen @% ,7. . e N

and 8% oxygen in the drywell and suppression chamber respectively; and, because the amount of 7 %74 electrolytic oxygen being produced in the reactor which could have been available for recom-bination in the event of a loss of coolant accident was reduced from that being produced at #g'@

full power. Thus, the safety implications of this occurrence were minimal. [;5 There were no abnormal radiation exposures to plant personnel and no effects on the health .

and safety of the public resulting from this occurrence.

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CORRECTIVE ACTION: ig p

                                                                                                    %. - if The initial action taken was to take samples and confirm the control room readings, and to       kg?.O notify maintenance of the Icak. After the control room readings were confirmed, the inerting of the Unit 2 primary containment was stopped, the leaking flange was isolated and repairs       T;if -

were initlated. 'T.[J? y .? ,l

 ,At 11:15AM on July 26, 1975 the gasket in the nitrogen line had been replaced and repairs         7Qj ;;

were completed. Inerting of Unit 2 primary containment was then re-initiated. At 12:15PM on July 26, 1975 the Unit 2 oxygen analyzer was zerced and spanned and a sample of the sup- %h [y pression chamber atmosphere Indicated an oxygen content of 4.3%. By 12:40PM the drywell g @ .1 l t ' *- II lt'E b6

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                                                       -2 etmosphere contained 4.0% oxygen and the suppression chamber 3.6%. At 2:40PM on July 26, 1975, the inerting of Unit 2 was completed and load was being increased at 3 MWE/ hour.

FA! LURE DATA: Thare has been one previous failure to inert the primary containment in the time allowed by Technical Specifications; however, that occurrence was caused by late arrival of the nitrogen supply truck. This is the first occurrence of this type caused by an equipment failure; therefore, there are no safety implications based on past experience. The replacement of the damaged gasket was considered sufficient tc correct the problem.

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