ML19317G897
| ML19317G897 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 11/12/1976 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8004020555 | |
| Download: ML19317G897 (2) | |
Text
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n NRCac M 195 U.C. NUCLEAn REEULAT' T CCMMISSILN oOCKET NdMM R 50-312
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Sacramento Municipal Utility Dict.
11/12/76 Mr. Robert U. Reid Sacramento, California oATE RECEivEo J. J. Mattinoe 11/22/76 l
S[,ETTER ONGTCMt2Eo PROP INPUT FORM NU.MSER oF COPIES RECEIVEo MRiolNAL
%NCLASslFIEo One signed OCoPy i
1 oESCalPTioN ENCLoSU RE'
- i Ltr. te our 10/4/76 ltr.... furnishing information on operating experience with j
loose parts and the loose parts monitoring j
system at Unit No.1.
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' SACRAMENTO MUNICIPAL UTILITY DilhRICT O 6201 S Street. Box 15830, Sacramento, California 95813; (916) 452-3211 ll 1S November 12, 1976 o>
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,4 Director of Nuclear fb[toh Regu'lation
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Attention:
Mr. Robert W. Re13, Chief i-
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Operating Reactors, Branch 4 iOh M,'
U. S. Nuclear Regulatory Comission 22 JgM 1 Washington, D. C.
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C Docket No. 50-312 Rancho Seco Nuclear Generating Station, Unit No. 1 1~s
Dear Mr. Reid:
In response to your letter of October 4,1976, the Sacramento Municipal Utility District would like to provide the following infonnation on operating experience with loose parts and the loose parts monitoring system at Ranchs Seco Unit No. 1.
To the best of our knowledge, there has never been a loose part within the primary loop of Rancho Seco Unit No. 1.
However, during hot functional testing, prior to fuel loading, an unusual flow condition produced by the operation of only one reactor coolant ptanp resulted in a rotational motion of the core barrel assembly causing an impact of this assembly against the guide lugs in the lower vessel region.
This impacting was first heard over the loose parts monitoring system, however, it was also audible within the containment building. A detennination of the source of this noise was made using the loose parts monitoring system, supplemented with additional. sensors and high speed recording systems.
A triangulation technique based on the differences in time required for the sound to travel to different sensors was used to locate the origin of this noise.
The Rancho Seco Unit No.1 loose parts monitoring system was installed prior to hot functional testing and has been in continual operation since that time.
The system is designed for vibration and neutrun noise analysis as well as loose parts detection.
There are a total of 10 channels l
in the system, 8 of which are for vibration and loose parts monitoring and 2 of which are for neutron noise analysis.
The 8 vibration and loose parts monitoring channels utilize 8 high temperature accelerometers located on the primary system with 2 on the incore instrument guide tubes, 2 on the upper vessel region, and 2 on the inlet to each steam generator.
For loose parts detection, the signal from these 8 accelerometers will trip an alarm at a voltage level equivalent to approximately a 1 ft-lb., impact at the sensor location.
The alann annunciates in the reactor control room and automatically starts a cassette tape recorder which then records the signal from 4 preselected channels.
This tape recording can then be used for future analysis.
.A.JJ5 7 AN ELECTRIC SY!iE M S E RVIN G MORE THAN 600,000 IN THE HEART OF C ALIF0 R N I A