ML20128E806
| ML20128E806 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/01/1992 |
| From: | Haynes H, Scace S NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| MP-92-1264, NUDOCS 9212080184 | |
| Download: ML20128E806 (2) | |
Text
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- Docket No. 50-423 Re: 10CFR50.37 December 1, 1992 MP-92-1264 U.S Nuclear Regulatory Commission Document Control Desk Washincton. D.C. 20555 Gentlemen:
Millstone Nuclear Power Station, Unit No 3 Loose Parts Detection Svstem This Special Report update is being submitted to update a Special Report submitted pursuant to Millstone Unit 3 Technical Specification 3.3.1.8.a. Loose Parts Detection System.
Plant Technical Specification 3.3,3.8.a requires that a Special Report be submitted to the NRC 10 days following one or more channels of the Loose Parts Detection System being declared inoperable for more than 30 days while in Mode 1 (Power Operation) or Mode 2 (Startup). This update provides additionalinformation to the June 14,1992 submittal.
On February 4,1992, at 1057 hours0.0122 days <br />0.294 hours <br />0.00175 weeks <br />4.021885e-4 months <br /> with the plant entering Mode 2 (Startup), at 3Fc power,2250 psia and 558 degrees Fahrenheit, the Loose Parts Monitoring System (LPM) was declared inoperable per plant Technical Specifications based on low level alarms on all channels.
Loose parts impacts in the Reactor Coolant System (RCS) are detected by accelerometers attached to major RCS components. An impact generates a signal from one or more accelerometers, which triggers a High Alarm annunciation on the Main Control Board. The Hich Alarm sienal causes information to be recorded from 12 channels onto a computei disk. Low' Alarm setpoints are used to detect and annunciate channel failures.
The system low alarms were fixed through the replacement of several system cards.
The system operational channels were declared sanctional on July 3,1992.
All functional channels were surveilled and considered capable of detecting loose parts. The following measures were established to verify channel operability. Disks were analyzed fcr degradation or failure on a monthly frequency, Contiw.ty checks of LPM cables to verify open. grounded or shorted circuits were performed on a monthly frequency.
These compensatory checks were performed in addition to the normal surveillances until the low level alarms were returned to service on Ju_ly 3,1992.
On September 2,1992, at 1410 hours0.0163 days <br />0.392 hours <br />0.00233 weeks <br />5.36505e-4 months <br />, with the plant in Mode 1 (Power Operation), LPM channel 12 went into alarm.
Channel 12 monitors loose parts activity in Steam Generator D, upper level. LPM channel 12 was taken out.of service at that time due to spurious low level vibration alarms.
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- 1 On September 2,-1992, at 1410 hours0.0163 days <br />0.392 hours <br />0.00233 weeks <br />5.36505e-4 months <br />, when channel 12 was declared inoperable, ten 1
'(10) of-the remaining eleven-(11) channels were operating properly and providing-
. redundant verification.
The remaining ino,erable channel was channel 10, Steam Generator - B, upper 'evel l
which was declarec inoperable on Niay 5,1992, and the subject of Special Report Docket Number 50-423, dated June 10,1992. Durine the extended outace which commenced on September 2,1992, channel 10 was invesligated further. It'was determined that channel 10 could not be repaired at this time.
On September 30,1992 at 0036 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> with the plant in hiode 1 (Power Operation) the plant commenced down power operations for an extended cold shutdown. During this a
period channels 10 and 12 were imestigated. Channel 12 was repaired; Channe.10 still
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remains inoperable. It was determined that the circuitry outside of the containment and extending to the hiain Control Room was functioning properly, further testing concluded -
that the channel failure was within containment.
Restoration of channel 10 has been scheduled for the next cold shutdown of sufficient--
duration or the next refueling outage.
The Licensee contact for this Special Report is Burtel N. Porrest, who may be contacted -
at (203) 444-5442.
Very truly yours, NORTHEAST NUCLEAR ENERGY-COh1PANY FOR: Stephen E. Scace Vipe President - hiillstone Station '
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hiillsto66 nit 1 Director SES/13NF:bjo-cc:
T, T. hlartin, Recion 1 Administrator P. D. Swetland Senior Resident inspector, hiilistone Unit _ Nos.1, 2 and 3 V. L. Rooney. NRC Project h1anager, hiillstone Unit Nos. I and 3-d f
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