ML19210A289
| ML19210A289 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 11/24/1976 |
| From: | Arnold R METROPOLITAN EDISON CO. |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| GQL-1605, NUDOCS 7910290527 | |
| Download: ML19210A289 (4) | |
Text
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- 4ETROPOLiiAN EDISON COMPANY POST OFF!CE BOX 542 REAOlNG, PENNSYLVANI A 19603 TELEPHONE 215 - 9294C01 November Eh, 1976 GQL 1605 S
OL c ~ Director of Nuclear Reactor Regulation gggl k e Attn: R. 'd. Reid, Ch' ef Pq ,h(// Operating Reacters E anch No. h r " 8848 U. S. Nuclear Regula cry Cc==ission g '4ashington, DC 20555 -{p 41 \\
Dear Sir:
Decket No. 50-289 Cperating License No. DPR-50 Attached is the information concerning the Loose Parts Mcnitoring Syste requested in your letter of October h, 1976. I trust you vill find all the necessary informaticn. However, shculd you need any additional information on this subject plesse contact either myself er D. G. Mitchell of cur Licensing staff. Sincerely, / R. C. Arnold Vice President RCA:DGM:daf Attachment M S T I 1487 170 $.2.D4
- 1) Two events have occurred in which a icose part was identified within the~reacter ecolant system of Three ? Ele Island, Unit dl.
Late in the 1976 refueling cutage, a notched pin measuring 1.288" long and 0.5LS" in diameter was found in the lower grid section of the core support assembly. A design review was ccnducted of key reactor ecolant system ecmpenents and interconnecting system compcnents. The review found that none of the major cceponents of the examined systems contained a pin of the type, or of the dimensions noted. It was further concluded that the loose pin did not occur due to deteri-oration of any system or ccmponent important to continued operation cr nuclear safety. The presence of this pin was not identified by the Vibration and Loose Parts Monitoring System. However, the unscoured condition of the pin indicated it had not =cved and therefore the L.P.M.S. would not detect it. Earlier in the 1976 refueling cutage, ancmalies were identified with the reacter vessel surveillance specimen holder tubes. Details of the event have been documented and submitted to the U3:EC. The vibrating specimen holder and resulting fractured holder tube were not identified by the Vibration and Loose Parts Monitoring System. In this case the noise created by the vibrating specimen holder was so slight ecmpared to the background noise that it could not be identi-fled by our system or any other system now in use.
- 2) Vibration and Loose Parts Monitoring of the reactor coolant system components in which a loose part could be entrapped, is provided by eight vibration and two nuclear plant channels. The two nuclear plant channels, placed on oppcsite sides of the re ctor core,.use a vide frequency range nuclear power channel to moritor for anchalcus cyclic differences in the core and provide reactivity related indicaticns of fuel pin, control red, and core structure motion. The vibration channels provide accustics indication of vibraticn throughcut the primary loop using pier.celectric crystal accelercneter. The locaticn in the reactor coolant system of the eight accelercmeters provide optimum effectiveness of the system. Two accelerometers are pcsitioned on in-core instrument guide tubes and two more are mounted on the lower flange of the centrol rod protection shroud. Cn each steam generator, two accelerometers are located near the inlet tube sheet.
The piescelectric crystal acceleremeters, which are used for accustic monitoring, have special purpose preamps for vide band operation. The alarm signal activates a lieht and a solid-state switch when the - aration level exceeds a preset level for a specified period of time. The nuclelr plant channel circuits operate in the same manner with the addition of a special filter to discriminate against hydraulic noise. However, the nuclear plant filter circuit is more sencitive than the vibration channels. 1487 171
-2_ Cnce each shift, when any of the reactor ecolant pumps are operating, the lecse parts =cnitoring cabinet is inspected fcr any alarm lights which would be repcrted to shift supervision. Also, ence each shift, the vibration and loose parts =cnitoring channels are monitored audibly for abnormal noise, or an increase in noise level. A power spectral density analysis is per formed on a =cnthly basis by plant personnel. Additionally, the data handling and data analysis subsystems provide for reccrding, audio evaluation, and spectral analysis of selected inputs. The use of the vibraticn and loose parts =cnitoring system was intreduced during 1973, approximately one year prier to ec=nercial cperation. 3) The alarm set points for the vibration and loose parts channels are each set for anticipated noise levels within the reactor ecclant system when cperating at 1005 pcuer. During start-up and ccc1down, various internal and extranecus noises frequently exceed the alarm set points. At full power operation spurious alarms have been experi-enced, but were deternined to be incensequential. There were two occasicns, described in Part 1, when the Vibration and Icose Parts Mcnitoring System did not detect a loose or vibrating part, b) A cost / benefit analysis has not been applied to the Vibration and Loose Parts Monitoring Systen at Three Mlle Island, Unit 1. It is the opinion of Metropolitan Edisen that the existing system vill provide adequate warning in the case of a vibration or loose parts problem that would be important to safety. 1487 172}}