ML20084R639
| ML20084R639 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 02/24/1975 |
| From: | Stephenson B COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20084R637 | List: |
| References | |
| 112-75, RO-50-249-75-06, RO-50-249-75-6, NUDOCS 8306150261 | |
| Download: ML20084R639 (2) | |
Text
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Com vnith Edison One Firs. aonal Plaza Cnicago, lihnois g
Address Reply to: Post Ofhce Box 767 CNcago, imnois 60690 g BBS Ltr. #112-75 Dresden Nuclear Power Statien r-b.%
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February 24, 1975 V
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Mr. James G. Keppler, Regional Director Directorate of Regulatory Operations-Region III U. S. Nuclear Regulatory Com ission 799 Roosevelt Road Glen Ellyn, Illinois 60137
SUBJECT:
REPORT OF UNUSUAL EVDTI' PER SETION 6.6.C OF THE TEENICAL SPECIFICATIONS EXCESSIVE LEAKAGE THROUGH VALVE A0'r'1601-21
References:
- 1) Regulatory Guide 1.16 Rev 1 Appendix A
- 2) Notification of Region III of U. S. Nuclear Regulatory Comission Telephone:
P. Johnson,1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br /> on February 18, 1975 Telegram:
J. Keppler, 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on February 18, 1975
- 3) Drawing Number: M-356 Report Number: 50-249/1975-6 Report Date: February 24, 1975 Occurrence Date February 14, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinois IDDiTIFICATION OF OCCU'tREJCE Leakage in excess of the Technical Specification limit of 5% Lto (29.381 sof/hr) was found to exist through isolation valvo A0 3-1601-21. Following the occurrence i
it was felt that this leakage rate was in excess of allowable total integrated i
leak rate. Subsequent investigation showed the total integrated leak rate to be 350 SCFH which is below the Technical Specification TMt of 588 SCFH. For the above reason the event has been classified as an Unusual Event rather than an Abnomal Occurrence.
CONDITIONS PRIOR TO OCCURRDICE At the tin:e the condition was found, Unit 3 was operating at a power level of 1230 MWT and a load of 396 M4e.
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DESCRIPPION OF OCCURIL%'CE At 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> on February 14, 1975, a local leak rate test was being performed on a section of pipe in the nitrogen inerting line bounded by valves 3-1601-21, -22,
-55, -56 and 3-8502-500. A leakage of about 350 SCFH was obtained which is above the 29 381 SCFH leak rate allowed by Technical Specifications.
The following day, at 0500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br />, primary containment integrity was returned when valve 3.-1601-21 was blind flanged.
DESIGNATION OF APPARINP CAUSE OF OCCURRENCE (Component Failure)
Following installation of the blind flange, the valve was removed from the system and inspected. This inspection showed tha't the valve seat was cracked in the area adjacent to the shaft.
The cause of the cracked seat is not known at this time, but the valve has been sent to the manufacturer for a further evaluation. A followup letter will be sent after the manufacturer has made his evaluation.
ANALYSIS OF OCCURRDICE This occurrence did not represent any threat to the health and safety of the plant personnel. The total integrated leakage, including the leakage through the 3-1601-21 valve, was 350 SCn! which is below the Tech Spec limit of 588 SCFH. Therefore, in the event of a loss of coolant accident. the allowabin intnerataa m imwv laavaga rate would not have been exceeded.
CORREL'TIVE ACTICN Valve 3-1601-21 was replaced. The temperature element which alarms on low temperature will be relocated so that it is in the nitrogen flow stream during the inertity; process.
Liquid nitrogen has reached some of these butterfly valves in the past and, if this was the cause, this action will help prevent repetition of the occurrence.
Any further action to prevent repetition of the occurrence will be delayed until the manufacturer has studied the valve.
I FAILURE DATA l
Leakage through the rubber seated butterfly valves has been a recurring problem on both units 2 and 3 Many of the valve failures have been linked to either cryogenic deterioration or improper assembling of the valve operator.
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W. B. Stephenson Superintendent BBS smp File /AEC A