ML20058L162
| ML20058L162 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 03/29/1974 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9105080336 | |
| Download: ML20058L162 (2) | |
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NORTHERN STATES POWER C O M P A e4 Y M I N N E A PO LI S. M IN N E S CTA 55401 1
March 29, 1974 s
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Mr. J F O' Leary, Director
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Dear Mr. O' Leary:
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MONTICELLO NUCLEAR GENERATING PLANT 3
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1 Docket No. 50-263 License No. DPR-22 q
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Reactor Low Low Water Level-ECCS Initiating Switch Malfunctio.
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A condition occurred at the Monticello Nuclear Generating Plant which ve' are reporting to your office in accordance with Section 6.7.B.1, Abnormal Occurrence Reporta, of Appendix A, Technical Specifications, of Provisional Operating License DPR-22.
On March 22, 1974, while performing a routine surveillance test, one of two switches on one of the four " Reactor Low Low Level-EcOS Initiation" instruments was found failed in the untripped state. At the time the switch malfunction was discovered, the plant was in a cold shutdown condition for reactor refueling operations.
The cause of the malfunction has not been identified; however, as a precautionary measure, the switch was replaced, and the instrument was calibrated.
Satisfactory repeatable operation of the switch was demonstrated in subsequent testing of the instrument.
The irstrument involved has been placed on an accelerated eight week surveillance test schedule.
The switch malfunction did not result in an unsafe plant condition since redundant instruments were found to trip at the desired trip setting and would have provided the required ECCS initiation function at the desired trip setting.
9105080336 740329 CF ADDCK 05000263
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t N O R*. _ERN CTATED POWER Co.
'ANY Mr. J F O' Leary I
March 29, 1974 Page 2 here have been three previous malfunctions of similar level switches at Monticello.. The latter two of these were due to conditions unrelated to this occurrence.
he cause of the first such malfunction, as in this occurrence,could not be determined.
The frequency of occurrences of such malfunctions is not felt to be excessive.
Yours very truly, b
L 0 Mayer, PE Director of Nuclear Support Services LOM/kn cc: J G Keppler G Charnoff Minnesota Pollution Control Agency Attn.
E A Pryzina
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