ML19308D056
| ML19308D056 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 02/15/1980 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8002260662 | |
| Download: ML19308D056 (1) | |
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- EMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 s street. Box 15830, sacramento. California 95813; (916) 452 4 11 February 15, 1980 Mr. Robert W. Reid, Chief Operating Reactors, Branch 4 Division of Operating Reactors Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Docket 50-312 Rancho Seco Nuclear Generating Station, Unit No. 1 Guide Tube Wear Measurements - Preliminary Results
Dear Mr. Reid:
A preliminary analysis of the results from the control rod guide tube wear measurement program has been completed showing some wear in the upper span corresponding to the control rod park positions.
A summary of the loca-tions of fuel assemblies measured as well as the approximate percentage of wear indications is presented in Attachment "A".
These wear indication measure-ments were calibrated to a standard that approximates a concentrated wear on one side of the tube.
A comparison between localized wear and uniform wear around the circumference shows that for the same eddy-current indication, the actual depth of wear will be smaller by as much as fifty percent.
A statistical analysis of the data has been performed to determine the probability of a control rod guide tube wearing to 100 percent and to determine the probability of any fuel assembly having an average of 55 percent wear during 150 weeks of full power operation. The average uniform wear of 55 percent ir an assembly is the value to retain pnsitive margin under worst case loading condition.
The results of this analysis indicate the probability of 100 percent wear for a guide tube or an average of 55 percent wear for a fuel assembly is very low, and is not expected.
The probability that 100 percent wear will not occur in 150 weeks of full power operation is 0.999989.
The probability of a fuel assembly not exceeding 55 percent average wear is 0.9999990 for 150 weeks of full power operation.
These results are preliminary and a final analysis and report will be issued at a later date.
Respectfully submitted,
/ h.sNx ohnI.Mattimoe Assistant General Manager
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and Chief Engineer Attachments ErCoJMOGGR
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