ML20138F580
| ML20138F580 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 04/29/1997 |
| From: | Hill W NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9705060007 | |
| Download: ML20138F580 (2) | |
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Northem States Power Company April 29,1997 Tech Spec Table 3.14.1 US Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22
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30 Day Special Report Inoperable Reactor Buildino Wide Ranae Gas Monitor This special report is being submitted as required by Monticello Technical Specification Table 3.14,1 for a reactor building vent wide range radiation monitor (WRGM) being inoperable for more than seven days. Although the WRGM was repaired the same day it was determined to be inoperable, investigation of the event indicated it had been inoperable for greater than seven days.
1 Attachment A of this letter provides results of our investigation into this event. This letter therefore fulfills the above notification requirements.
This letter contains no new NRC commitments, nor does it modify any prior commitments.
Please contact Sam Shirey, Sr Licensing Engineer, at (612) 295-1449 if you require further information.
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Plant Manager Monticello Nuclear Generating Plant i
cc: Regional Administrator-Ill, NRC NRR Project Manager, NRC Resident inspector, NRC J Silberg 1
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Inoperable WRGM Attachment A Apr!! 29,1997 BACKGROUND AND ACTION TAKEN On 4/1/97 the Superintendent of Chemistry was informed of abnormal indications on the A train of the reactor building vent wide range radiation monitor (WRGM). Specifically, when the WRGM filter papers were removed as part of weekly procedure 0356, " Stack / Vent lodine / Particulate Dose Rate Limits" the A train filter appeared lighter than the B train filter.
i The Superintendent of Chemistry relayed this information to the system engineer as a possible indication of inleakage downstream of the filter.
On 4/2/97, a work order (WO) was initiated to investigate if any air inteakage was present at the WRGM sample skid, and a 7-day LCO was entered per Technical Specification Table 3.14.1. Once the problem was identified as a leaking WRGM pump, new WOs were written to replace the pump, and to repair / refurbish the removed pump and determine the cause of the failure. The replacement pump was insta; led and declared operable on 4/2/97.
Also on 4/2/97, Condition Report 97001053 was initiated to further investigate the failure.
Review of previous filter samples indicated that failure of the pump diaphragm had occurred in February 1997.
CAUSE Investigation determined the cause of the leakage to be a ruptured pump diaphragm. Previous sample pump failures have invariably resulted in loss of flow which is continuously monitored and therefore immediately indicated. This particular failure was not easily detected as sample flow remained within specification. Also, the radiation levels in the plenum duting normal operation are approximately the same as the room which contains the WRGM skids.
Therefore, no difference was noticed in the indicated count rate.
PLANS AND SCHEDULE This type of failure can be detected by looking for different levels of discoloration on filter papers from the two trains. Procedure 0356, " Stack / Vent lodine / Particulate Dose Rate Limits" has been revised to compare the two filters for unequal discoloration.
SAFETY SIGNIFICANCE The reactor building ventilation WRGMs are not safety related, nor do they provide any trip function. They are a Reg. Guide.1.97 accident monitoring system. Channel B was operable at all times during the period that Channel A was suspected of being inoperable. Therefore ti:e safety significance is minimal.
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4/26/97 SIS J: \\ LICEhS E\\ N RCCORRWRGM. p FT I