ML20084P954
| ML20084P954 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 03/21/1974 |
| From: | Kalivianakis N COMMONWEALTH EDISON CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084P957 | List: |
| References | |
| NJK-74-6, NUDOCS 8306130082 | |
| Download: ML20084P954 (2) | |
Text
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50-265
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Post Ohed Box 216 '
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z.g'.gnV,g$i March 21, 1974 Q',
Mr. John F.
O' Leary, Director
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Directorate of Licensing Regulation U.
S.
Atomic Energy Commission Washington, D.
C.
20545 i
Reference:
Quad-Cities Nuclear Power Station, Unit Two License DPR-30, Docket 50-265, Appendix A, Se'ction 1.0.A.2, 3.7.A.S.a, 6.6.B Dear Mr.
O' Leary:
The purpose of this letter is to inform you of the details concerning an abnormal occurrence which took place on March 15, 1974 uhereby the Unit Two primary containment oxygen concen-tration increased to approximately 5.5 percent, exceeding Technical Specification 3.7.A.5.a.
This abnormal occurrence was reported to you by telegram on March 15, 1974.
PROBLEM AND INVESTIGATICN At 1205 on March 15, 1974, with Unit Two operating at 778 "We, the primary containment oxygen concentration was confirmed to be'5.5 percent oxvgen as indicated by the Primary Contain-ment Oxygen Analyzer System Control Converter, 2-8741-5, on panel 912-7.
Radiation protection department made this con-firmation based on primary containment atmospheric samples that showed the primary containment oxygen concentration to be 5.2 percent oxygen.
The primary containment nitrogen make-up regulator byoass valve 2-8799-21 was opened to admit more nitrogen into the primary containment.
The primary containment oxygen concentration was reduced to 5.0 percent oxygen by 1630.
EVALUATION Effects of this abnormal occurrence are minimal.
The total
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increase of the primary containment oxygen concentration a-mounted to 0.5 percent oxygen in excess of the Technical Snec-ifications limit.
Exceeding-this limit by 0.5 per, cent, oxygen 8306130002 740321 L'
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Mr. J.
F. O' Leary March 21, 1974 for a short time has a relatively insignificant effect since power operation is allowable for twenty-four hours after going into the RUN mode and twenty-four hours before going out of I
the RUN mode without significant effects on plant safety.
DETER'4INATION OF CAUSE AND CORRECTIVE ACTION The cause of this abnormal occurrence has been determined to be~ air in-leakage into the drywell pneumatic system.
This was determined by Radiation Protection department taking atmospheric samples from the drywell pneumatic system receiver.
It was found that the oxygen concentration in the receiver was 6.0 percent oxygen.
In comparing the results of these samples to the primary containment atmospheric sample taken previously (5.2 percent oxygen), air in-leakage into the drywell pneumatic system was resolved as the cause of the primary containment oxygen concentration increase.
Acting upon this conclusion, all flange bolts and other fit-tings on the drywell pneumatic system uere tightened.
As a result, comparative atmospheric samples taken from the drywell pneumatic receiver and the primary containment on March 18, 1974 indicated 4.0 percent oxygen and 4.3 percent oxygen re-spectively.
It appears that the air in-leakage into the dry-well pneumatic systen has been stopped and the probability of further primary containment oxygen concentration problems has been reduced.
CU:'ULATIVE EXPERIENCE For several weeks prior to this occurrence it had been necessary to run with the nitrogen make-up bypass valve open quite fre-l quently in order to maintain the primary containment oxygen I
concentration within the Technical Specifications limit.
The repairs that were made subsequent to this occurrence appear to have cased this problem.
Since the repairs were made it has been possible to operate with the bypass valve open at less frequent intervals than before the occurrence.
It is felt that the probability of repeating this occurrence has been i
reduced by the above actions.
Very truly yours,
3 COMMONWEALTH EDISON COMPANY QUAD CITIES NUCLEAR POWER STATION
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N.
Kalivianakis Station Superintendent NJK/lk
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