ML20056B744
| ML20056B744 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 11/16/1971 |
| From: | Duncanson R NORTHERN STATES POWER CO. |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9102080477 | |
| Download: ML20056B744 (2) | |
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NORTHERN STATES POWER COMPANY l
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l Dr. Peter A. Morris, Di rector 9
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Dear Dr. Morris:
9 Sw Lc r:n LONTICELLO TOCLEAR GENERATi fG PLAfd 0
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/,g (' 1 Docket No. 50-263 License No. DPR-22 Failure of an ECCS Pump Start Permissive Switch to Trip Within the S ecified Settings p
During the performance of a conthly surveillance test on October 20, 1971, it was discovered that an ECCS pump start permissive pressure switch tripped below the trip settings specified in the Technical Specifications. This occurrence is being reported in accordance wi th Section 6.6.B.3, of the Technical S ecifications. The Region t il Compliance Office has been notified p
of the occurrence.
Sumarv Des-rint inn nr 0-merenm On October 20, 1971, a trip setting of a low reactor pressure pump start permissive switch (switch #2 of PS 2-3-53A) was found to be approximately 1
12.5 psig below the trip setting of t 450 psig specified in Table 3.2.2 of the Technical Specifications.
(The allowable deviation for this trip setting, as specified in Table 3.2.5 of the Technical Specifications is
-10 psi..) The #2 switch of PS 2-3-53A is used in the LPCI start permissive logic; however, automatic initiation of the LPCI system would have occurred, if requi red, at the specified reactor pressure by action of the redundant pump start permissive switch PS 2-3-533.
The investication of the occurrence shows that switch PS 2-3-53A operates p rope rl y.
As a result of this finding the low setpoint problem has been attributed to setpoint drift andfo,r calibration inaccuracies.
To prevent similar occurrences from happening, the low reactor pressure pump start permissive switches will be set at 460 psig prior to further plant operations.
Increasing the setpoint will not present any operational difficulties since the core spray and RHR pumps are provided with minimum flow i.nes so that the pumps will not be damaged by early starts.
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l The unusual occurrence report has been written for this occurrence and will be available to the Region iIl Compli ance i nspector for revier: during his next visit.
Yours very truly, l
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R.O. Duncanson, Jr. P. E.
Manacer of Power Production Chai rman Monticello Safety Audit Committee F0D/CEL/ car l
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