ML20058K736

AO 263/74-21:on 740722,while Performing Calibr of Off Gas Radiation Monitors,Steps of Off Gas Monitor Calibr Procedure for Insertion of Channel Trip When Channel Removed from Svc Not Performed.Procedure Revised

ML20058K736
Person / Time
Site:	Monticello
Issue date:	08/01/1974
From:	Mayer L NORTHERN STATES POWER CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
AO-263-74-21, NUDOCS 9102130544
Download: ML20058K736 (2)

Text

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I MSP NORTHERN STATES POWER COMPANY _

' s M IN N E A PO LI S. M I N N E S OTA 5 S4 01 Mr. J F O' Leary, Director 3' -

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Directorate of Licensing t

Office of Regulation U S Atomic Energy Cor:nnission ,

Washington, D C 20545

4 ABN0EMAL OCCURRENCE REPORT TO THE AEC 2 / -

Off Gas Radiation Monitoring System Disabled During Calibration

1. Report Ntnuber: A0 263/74-21 2a. Report Date: August 1, '.974 K

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2b. Occurrence Date: July 22, 1974

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Facility: Monticello Nuclear Generating Plant .-

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Monticello, Minnesota 55362 $ ,k ph.1' A

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4. Identification of Occurrence:

This occurrence concerns the failure to insert a protectio ch signal for the off gas radiation monitors when the individual channels were made inoperable for calibration. .

5. Conditions Prior to Occurrence Steady State Power - the plant was at approximately 85 of rated power.

6. Description of Occurrence:

While performing a calibration of the off gas radiation monitors, steps of the off gas monitor calibration procedure which call for the insertion of a channel trip, when a channel is removed from service for calibration, were i not perfor=ed.

7. Desienation of Apparent Cause of Occurrence:

Operator - Personnel performing the test erroneously assumed that certain steps of the off gas monitor calibration procedure pertained only to the off gas holdup system, and that those steps were not required since the off gas holdup system was not in service. Contributing to the cause of the occurrence was the fact that the off gas calibration procedure used was a recent revision which had not been used previously.

As such, personnel were not familiar with the requirements of the new procedure.

REGULATORY DOCKET (over) FILE COPY. gg 9102130544 740B01 CF ADOCK 05000263 CF .

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NORTHERN OTATEC) POWER COMPANY ,

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8. Analysis of Occurrence:

The upscale and downscale trip outputs of the two off gas monitors are combined such that one upscale trip and one downscale trip, two upscale trips, or two downscale trips will initiate a closure of the off gas line isolation valves. As a result of the failure to trip the off gas monitor channel that was made inoperable for calibration, the off gas line high radiation isolation protective function was defeated for a total of approx-imately fifteen minutes. No changes in off gas radiation level were observed during the time the high radiation isolation protective functi on was inoperable.

9. Corrective Action: [

A letter discussing the recent changes made to the off gas monitoring system was circulated to operations person 2el. In addition, the off gas monitor calibration procedure has been revised to identify the steps which insert a channel trip for calibration as requirements which must be met to consider the off gas monitoring system operable.

10. Failure Data:

Not applicable to this occurrence.

L 0 Mayer, PE /

Director of Nuclear Support Services LW/kn cc: J G Keppler G Charnoff Minnesota Pollution Control Agency Attn. E A Pryzina k

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