05000369/LER-1981-085, Forwards LER 81-085/03L-0.Detailed Event Analysis Encl

Forwards LER 81-085/03L-0.Detailed Event Analysis Encl

ML20009F731
Person / Time
Site:	McGuire
Issue date:	06/11/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20009F732	List: 05000369/LER-1981-085, Forwards LER 81-085/03L-0.Detailed Event Analysis Encl 05000369/LER-1981-085-03, /03L-0:on 810513,while in Mode 5 Initial Fuel Loading,Concentration of Oxygen & Hydrogen in Waste Gas Shutdown Tank Exceeded Tech Spec Limits.Caused by Personnel Error.Concentrations Brought to Acceptable Limits
References
NUDOCS 8107310471
Download: ML20009F731 (3)

LER-1981-085, Forwards LER 81-085/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3691981085R00 - NRC Website

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Qgumcor, DUKE POWER COMPANY Powra Unit.ntxo 422 SocTis Cucacis STurtT, CnAHtDTTE. N. C. 28242 Ii wituAu o. pan atn. sn.

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Mr. James P. O'Reilly, Director g

U.S. Nuclear Regulatory Conmission 3.

Region 11 JUL 3 01981 ~ -

101 Marietta Street, Suite 3100 16-u mmu autou Atlanta, Georgia 30303 5

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8 Re: McGuire Nuclear Station Unit I r

Docket No. 50-369 N

Dear Mr. O'Reilly:

Please find attached Reportable Occurrence Report R0-369/81-85. This report concerns the concentrations of oxygen. and hydrogen in the Waste Gas System exceeding Technical Specification ilmits.

This incident was considered to be of no significance with respect to the health and safety of the public.

Ve ' truly yours, j

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William O. Parker, Jr.

RWO:pw Attachment cc:

Director Mr. Bill Lavallee Office of Management & Program Analysis Nuclear Safety Analysis Center U. S. Nuclear Regulatory Commission Post Office Box 10412 Washington, D. C.

20555 Palo Alto, CA 94303 Ms. M. J. Graham Resident Inspector - NRC McGuire Nuclear Station f

' 'f) 8107310471 810611 PDR ADOCK 05000369 S

PDR

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McGUIRE NUCLEAR STATION INCIDENT REPORT Report Number:

81-85 Report Date: June 1, 1981 Occurrence Date: May 13, 1981 Facility: McGuire Unit 1, Cornelius, N. C.

Identification of Occurrence:

The concentration of oxygen (0 ) and hydrogen (H )

2 2

in the Waste Gas (WG) System exceeded the limits set forth as a limiting con-dition for operation.

Conditions irior to occurrence: Mode 5:

Cold Shutdown.

Prior to initial criticality.

Description of Occurrence: Vent gases were being transfeired from the Pressurizer Relief Tank (PRT) which were high in oxygen concentration to the WG Shutdown Tank B (SDT-B); hydrogen was being added to this volume of gas and this gas was passed through the Hydrogen Recombiner System to reduce the 0, concentration.

Too much H, was added, however, and this high H c nc ntration {10%) in conjunction with 2

efie concentration of 02 (7 ) already present in the system.. constituted a degraded mode of operation and was reportable pursuant to Technical Specification 3.11.2.5.

Apparent Cause:

The high 0 concentration was caused by venting the Reactor Coolant (NC) System during $1111ng operations into the PRT and then into the WG System.

H fr a the Hydrogen Bulk Storage (GS) System was added to the WG System 2

so that the gaseops mixture could be passed through the hydrogen recombiner.

Analysis of Occurrence: Following the escalation of the plant from Mode 6 to Mode 5 the NC System was being refilled.

The area under the reactor head con-tained a " bubble" of air which was entrapped in the NC System.

This and other pockets of air were vented into the PRT, using an approved procedure, Filling and Venting of Reactor Coolant System.

This volume of gas was, in turn, transferred to the WG System into the SDT-B between 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> atd 0330 hours0.00382 days <br />0.0917 hours <br />5.456349e-4 weeks <br />1.25565e-4 months <br /> on May 13, 1981.

The concentration of 0 was 7% by volume.

The bulk of gas within the WG System 2

was composed of nitrogen (N )*

2 Preparations were being made to add hydrogen to SDT-B from the GS System.

The re-sulting mixture would than be passed through one of the hydrogen gas recombiners to convert the 0., and H2 gases into water. A mixed volume of gas with a 10% con-centrationofH[byvolumewasobtainedinadvertently.

The resulting mixture of gases was diluted with nitrogen and processed through the recombiner. At 0525, the H and the 0 c neentrati n were ea h 2.5% by volume.

2 2

[

Report Number 81-85 Page 2

Safety Analysis

The Specification, 3.11.2.5, is provided to ensure that the concentration of potentially explosive gas mixtures contained in the WG System is maintained below the flammability limits of H and 0 ; The lower flammability is 4.5%.

Anycixturewitdinthelimitsofflammn-2 limit for H, is 4% and for 02 bility is cInssified as explosive. Maintaining the concentration of H and 0 2

2 below their flammability / explosive limits provides assurance that the release of radioactive materials will be controlled in conformance with the requirements of General Design Criterion 60 of Appendix A 10CFR Part 50.

Since analysis of the NC and WG Systems proved that no radiation was present at the time of this incident and no ignition source was present to ignite'the mixture of gases, the health and safety of the public were not affected by this incident.

Corrective Action

The immediate corrective action was tu reduce the H and 0 concentration to acceptable levels.

This was accomplished by introducing ad 2 2

ditional nitrogen into the process stream and passing this diluted mixture through the recombiner.

This action brought the concentration within acceptable limits within 35 minutes.

Changes were made to the operating procedure to allow the excess gases trapped in the NC System to be released from the PRT into containment atmosphere.

This would prevent putting such an 0 -rich load into the WG System and would, in 2

turn, reduce the need for adding H '

2 i