ML20058L320
| ML20058L320 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 05/24/1974 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| AO-263-74-10, NUDOCS 9105140453 | |
| Download: ML20058L320 (3) | |
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MSP NORTHERN STATES POWER COMPANY MIN N E A PO LIS. MIN N E SOTA SS40%
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U S Atomic Energy Commission Wathington, DC 20545
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Dear Mr. O' Leary:
MONTICELLO NUCLEAR GENERATING PIR;T Docket No. 50-263, License No. DPR-22, A0 263/74-10 Primary Containment Leakage A condition occurred at the Monticello Nuclear Generating Plant which we are reporting to your office in accordance with Section 6.7.B.1, Abnormal Occurrence Reports, of Appendix A, Technical Specifications, of Provisional Operating License DPR-22.
On May 13, 1974, during the primary containment integrated leak rate test, leakage was observed from the vent port of the three-way solenoid valve which controls the air supply to the test operator for torus-to-drywell vacuum breaker "G".
The leakage, at 41 psig, was found to be approximately 3.0 weight percent of the contained air per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, which is 2\\ times the acceptance criteria for the integrated leak rate test.
On May 16, 1974, following a torus entry, it was confirmed that the 3/8" cir supply tubing for the test operator had been left uncapped when the "G" vacuum breaker was removed on September 30, 1973, for off-site dynamic tests. At that time it was not recognized that the air supply line and solenoid valve provided a leakage path.
Prior to plant startup the air line was capped inside the torus. Also, manual block valves have been installed between the torus and the solenoid valves for all ten vacuum breaker test operator., (see attached figure).
These valves will be kept closed except while conducting routine exercising of the vacuum breakers.
There have been no previous similar occurrences at Monticello. All other items of equipment inside primary containment which require air for testing or operation are supplied by a common instrument air header inside the 9105140453 740524 CF ADOCK 05000263 CF
NO)..'HERN CTATED POWER CLMPANY Mr. J F O' Leary May 24, 1974
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Page 2 containment.
Solenoid valves for such equipment are located inside primary containment and vent to containment atmosphere.
If a line were to fail or become disconnected from the solenoid, it would not vent outside of pr'. nary containment.
Yours very truly, L 0 Mayer, PE Director of Nuclear Support Services LQ4/kn l
cc:
J G Keppler G Charnoff Minnesota Pollution Control Agency Attn. E A Pryzina Attachment
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