ML20212F730
| ML20212F730 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 09/21/1999 |
| From: | Rich Smith NIAGARA MOHAWK POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NMP1L-1472, NUDOCS 9909280347 | |
| Download: ML20212F730 (2) | |
Text
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NiagarahMohawk' September 21,1999 NMPIL 1472 l
U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 RE:
Nine Mile Point Unit 1 Docket No. 50-220 DPR-63
Subject:
Special Report Gentlemen:
In accordance with Nine Mile Point Unit 1 Technical Specification Table 3.6.11-1, " Accident Monitoring Instrumentation," and associated Action Statement 4.a, Niagara Mohawk Power Corporation (NMPC) is submitting the following special report concerning the inoperability of the #12 Containment Hydrogen Monitoring System.
In addition, NMPC is submitting this Special Report as a supplement to the Special Report, dated March 1,1999, in the March 1,1999, Special Report, NMPC stated that a low flow condition would be investigated, and the cause would be reported in a supplemental report.
Dewrlption of Event On September 7,1999, at 1259 hours0.0146 days <br />0.35 hours <br />0.00208 weeks <br />4.790495e-4 months <br />, with the reactor mode switch in the "RUN" position during normal operations, control room operators declared #12 Containment Hydrogen Monitoring System inoperable for planned maintenance. This planned maintenance was to troubleshoot a low flow condition, replace parts in the sample pump with redesigned parts, and calibrate support instruments.
As stated in the Special Report dated March 1,1999, a flow switch failed to initiate an alarm for a low flow condition. The cause of the failed flow switch was a degraded encapsulated reed switch within a flow switch. The cause of the low flow condition was unknown at that time. As part of the plarmed maintenance performed on September 7,1999, the flow control l
valve, rotameter and the flow switch were cleaned and rebuilt. During this maintenance, the Ig-l maintenance technicians discovered foreign material in the piping downstream of the sample pump. A sample of this foreign material was taken and the sample revealed that the foreign material was a ferrous material. NMPC concluded that the foreign material was from degradation of the sample pump valve discs, since the valve discs were found in a degraded y
condition and are the only parts of the system that are ferrous. Based on this conclusion,
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NMPC replaced the sample pump valve discs with redesigned valve discs that will make them less susceptible to degrad,atiog.{
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l This planned maintenance on the #12 Containment Hydrogen Monitoring System is continuing with a scheduled completion date of September 24,1999.
Cance of Event The cause of operators declaring the #12 Containment Hydrogen Monitoring System I
inoperable was planned maintenance as described above.
The cause of the low flow condition was determined to be foreign material. Over time, the sample pump valve discs degraded which resulted in this foreign material being released downstream of the sample pump. This foreign material being lodged on the o-ring and needle valve of the flow control valve diminished the sample flow causing the low flow condition.
4 Corrective Actions 1
1.
The sample pump valve discs were replaced with a redesigned valve discs less susceptible to degradation.
I 2.
The system is being flushed with freon and compressed air to remove the foreign material. This action is scheduled to be completed by September 24,1999.
I 3.
Work Order 99-04831 has been written to perform identical maintenance on #11 Containment Hydrogen Monitoring System. This maintenance is scheduled to start on 1
October 10,1999.
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4.
Maintenance will establish a preventive maintenance task to clean and monitor the condition of the flow switches and flow control valves on a periodic basis by February 25,2000.
Very truly yours, I
l Robert G. Smith Plant Manager - NMP1 RGS/CES/ kap xc:
Mr. H. J. Miller, Regional Administrator, Region I Mr. G. K. Hunegs, NRC Senior Resident Inspector Records Management
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