ML20058K629

AO 263/74-17:on 740615,while Maintaining Reactor at Low Power to Facilitate Repair of Small Leak in Reactor Feedwater Pump Warmup Line 11,reactor Mode Switch Placed in Startup Position for Approx 7 1/2 H

ML20058K629
Person / Time
Site:	Monticello
Issue date:	06/24/1974
From:	Mayer L NORTHERN STATES POWER CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
AO-263-74-17, NUDOCS 9102130395
Download: ML20058K629 (2)

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4 BY2tCT.VDocl;effjjg ggy NORTHERN STATES POWER COMPANY win N E Apou s. wiu s e sora e s4os s

Mr. J F O' Leary, Director 9- 7v Directorate of Licensing ,

Office of Regulation i, U S Atomic Energy Commission .,

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k'a shington , DC 20545 _

ABNORMAL OCCURRENCE REPORT TO THE AEC f '-

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Omission of IRM Heat Balance h*r/. .

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1. Report Sumber: 2:3/74-17 2A. Report Date: Jane 24, 1974

23. Occurrence Date. June 15, 1974

3. Facility: Monticello Juclear ':enerating Plant ( DPR- 22 )

Monticello, Minnesota 55362

~ r 4 Identification cf Occurrence:

This repert concerns the emission of an IR'i heat balance calibration. _ _ _

5. Conditions Prior to occurreace:

Hot Standby: The generator was off the line and reactor power was reduced to about 160 ' Nth to facilitate repairs to a reactor feedwater pump wer=up line.

6 Descrintion of necurrence:

On the morning of June 15, 1974. while maintaining the reactor at low power to facilitate the repair cf a small leak in the 70. Il reactor feedwater pump warmup line, the reactor mode switch was placed in the STARTUP position for a period of apprey.imately 7% hours. During the subsequent power escalation, engineering personnel discovered that an IE1 heat balance calibration had not been performed.

7. Desi gnation o f Apparent Cause of the occurrence:

Since the power reduction was forced by the warmup line leak, thorough planning of the power reduction was not possible. It had been thought that it would be feasible to remain in the RUS mode during the reduction, such that the IR"s vould not be used. Therefore. no orders were issued and no plans made to perform the IICI heat balance calibratten. i. l s o , at the time the mode switch was placed 1r the STARTCP mode, the requirements for the IRM heat balance were misinterpreted.

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NORTHERN OTATED POWER COMPANY S. Analvsis of Occurrence:

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The IRM's response has been found to be quite dependent on rod pattern in relation to any given power level. Therefore, it has been the practice to set the IRM's several percent above the actual power level to insure adequate  ;

conse rva tism. In addition, the operators are able to assess the approximate pewer by examining the APRM-IRM overlap prior to leaving the RUN mode.

Experience shows that the IRM gain does not have to be adjusted frequently, partially due to the conservatism cited cbove.

The emission of a single IRM heat balance is therfore not likely to lead to IRM's being out of calibration. Evaluation of the plant conditions that existed during the morning of 6/15/74, showed that al? IRMs had been properly ,

calibrated and would have fulfilled their intended function.

9. Corrective Action:

The operators have been reminded of the requirements and the IRM Heat Balance Procedure has been revised to facilitate its performance. The Shif t Supervisors have received training which will allow them to perform the balance should the need arise when appropriate engineering personnel are not available.

10. , Failure Data:

Not applicable.

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fDMAL L 0 Mayer, PE Director of Kuclear Support Services LOM/kn ec: J G Reppler G Charnoff Minnesota Pollution Control Agency Attn. E A Pryzina

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