ML023290411
| ML023290411 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 11/04/2002 |
| From: | Forbes J Nuclear Management Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML023290411 (3) | |
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NMCe Commtted to Nuclear Exclece Monticello Nuclear Generating Plant Operated by Nuclear Management Company, LLC November 4, 2002 US Nuclear Regulatory Commission Tech Specification 3.14.1 Washington, DC 20555 Attn: Document Control Desk Monticello Nuclear Generating Plant Docket No. 50-263 License No. DPR-22 30-Day Special Report Inoperable Offgas Stack Wide Range Monitors This special report is being submitted as required by Monticello Technical Specification Table 3.14.1 for both Offgas Stack Wide Range Radiation Monitors being simultaneously inoperable.
Attachment A provides the results of our review of the event. Appropriate entries were made into the Corrective Action Program in response to this event.
This letter contains no new NRC commitments or modifications to prior commitments.
Please contact Paul Hartmann, Senior Licensing Analyst, at 763-271-5172 with any questions or comments.
effrey S. Forbes Site Vice President Monticello Nuclear Generating Plant Attachment c: Regional Administrator-lIl, NRC NRR Project Manager Resident Inspector, NRC Minnesota Dept of Commerce
,.1 2807 West County Road 75 . Monticello, Minnesota 55362-9637 Telephone: 763-295-5151 . Fax: 763-295-1454
7: s4-Inoperable Radiation Monitors Attachment A BACKGROUND AND ACTION TAKEN Technical Specification (TS) Table 3.14.1, Instrumentation for Accident Monitoring, includes the Offgas Stack Wide Range Radiation Monitors (also known as Wide Range Gas Monitors or WRGMs). The TS Table requires two instrument channels, and a minimum of one operable channel. Since both channels of Offgas Stack WRGMs were inoperable, a 30-day special report is required.
On October 8, 2002 a control room operator observed indications indicative of a momentary loss of sample flow to the A Channel Offgas Stack WRGM. The sample pump flow lamp de-energized and the Low/Mid/Highi/Effluent lamps began flashing when the INOP alarm was received. Without operator intervention, the sample flow pump lamp re-energized. The chart recorder indication was observed to remain normal.
A work order was initiated in response to the apparent interruption of sample flow on Channel A, requiring removal of the Channel from service. During performance of the work order on Channel A, similar indications were received on the B Channel sample flow system. A similar work order was written in response, requiring removal of the second Channel (B) from service. With both A and B Channels of the Offgas Stack WRGMs out of service, the preplanned alternative method of Stack monitoring was initiated by performing grab samples as required by plant Technical Specifications, and this 30-day special report was initiated.
CAUSE OF INOPERABILTY Work crews pursued a reason for the momentary loss of sample flow and fourid sample flow filters unobstructed. Additional investigation found evidence of moisture in sample flow lines for both channels due to an abnormal stack dilution line-up for unrelated maintenance. This line-up resulted in a larger proportion of dilution flow from the plant Steam Jet Air Ejector (SJAE) room. The Offgas Stack WRGM sample flow paths were purged to remove moisture and the stack dilution flow line-up was restored to normal.
On October 21, 2002, further investigation disclosed that a piping leak in the SJAE-room was creating high levels of vapor in the room. On October 22, 2002 the leak was isolated.
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Inoperable Radiation Monitors Attachment A PLANS AND SCHEDULE FOR RESTORING THE SYSTEM TO OPERABLE STATUS Both Channels of the Offgas- Stack WRGMs were returned to service within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of the initial occurrence.
SAFETY SIGNIFICANCE The Offgas Stack WRGMs are not safety related. They are Category 2, Regulatory Guide 1.97 accident monitoring systems. Initially both channels were declared inoperable with moisture in the sample flow lines. Additional review determined that the instruments would have operated satisfactorily with the levels of moisture found in the sample flow lines. Thus; the majority of the time both Channels of the Stack WRGMs were declared inoperable for maintenance, the Stack WRGMs would have provided accurate indication (when the sample flow pumps were operating).
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