ML19344D509
| ML19344D509 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 03/03/1980 |
| From: | Walbridge W SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8003120557 | |
| Download: ML19344D509 (1) | |
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SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S Street. Box 15a30. Sacramento, California 95813; (916) 452-3211 Starch 3, 1980 Director of Nuclear Reactor Regulation ATTN:
Str. Robert W.
Reid, Chief Operating Reactors, Branch No. 4 U. S. Nuclear Regulatory Commission Washington, D. C.
20S55 Docket No. 50-312 Rancho Seco Nuclear Generating Station, Unit No. 1
Dear >!r. Reid:
During the 1980 refueling snubber functional test program, all 53 of the Bergen-Paterson units were tested.
Seven units failed, Six of these failures were due to marred poppets or bent or broken poppet springs.
These problems are similar to those seen during the 1978 test program during which 10 failures occurred.
(Reference November 30, 1978 letter.)
A comparison was made between the ITT Grinnell units, which showed excellent reliability during the 1978 and 1980 testing, and the Bergen-Paterson units.
The long guide poppet design used in the ITT Grinnell valve limits poppet movement and is the key to their superior performance.
This precludes the valve failures seen with Bergen-Paterson units.
Based on the above program, the Sacramento Municipal Utility District asks the NRC for concurrence with this analysis within the requirements of Technical Specifications Section 4.14.4 Respectfully submitted, W. C. Walbridge General Manager WCW:RWC:jr cs.
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SACRAr.tEaTO f.'UNIC; PAL UTILITY O!STR:CT C 62')1 S Str'cet. Box 15830. Socramento. California 95813; (916) 452 3211 November 30, 1978 Director of Nuclea'r Reactor Regulation '
ATTN:
Mr. Robert W. Reid, Chief Operating Reactors, Branch No. 4 U. S. Nuclear Regulatcry Commission Washington, D. C.
20555 Docket No. 50-312
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Rancho Seco Nuclear Generating Station, Unit No. 1
Dear Mr. Reid:
Preliminary to this letter, R. Colombo and J. Field from my staff contacted Mr. J. Zwetzig, our Section Chief, on November 29, 1978.
Mr. Zwetzig asked for a written state =ent explaining the' circumstances under which an appropriate detercination can be made to provide the District with a letter of concurrence.
The Snubber Test Program for the 1978 refueling outage was started with a representative' sample of 10 snubbers as called for in the-Rancho Seco Unit No. 1 Technical, Specifications. There was one failure in the first sampling. The failed unit was a Bergen-Paterson snubber.
A second group of 10 snubbers was selected and tested. There were three failures in this group.
All of the failures were Bergen-Paterson units.
Only Bergen-Paterson units were selected in the succeeding groups of 10.
With 54 units tested, 10 failures have occurred.
Nine of these Bergen-Paterson snubbers failed in the same : code. The spring is entrapped between the poppet and seat on the retraction side of the valve block damaging the sest surfaces.
The responsible engineer, having reviewed these failures, hypothesizes that these nine failures have been caused by abusive handling during reinstal-lation after the 1977 test program. The engineer states that he discovered that when thesc units were being reinstalled af ter the 1977 test program, the shaft end of Fergen-Paterson units were being sla!..med against floors and walls in order to shorten them for reinstallatien.
All units were reset to their proper 3cngth in the test stand af ter testing; however, the spring loaded, accumulator in Bergen-Patersen units causes the units to grow if not installed
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soon after retting.
When the engineer found that the units were being mishandled, he stopped that procedure and selected sonc units f or retest. No failures were found in this sampling, so no further action wa,s taken.
He now believes that '
the failures presently observed are a result of the mishandling in 1977.
The singic fatture of the remaining Bergen-Paterson unit was a broken pisten ring and this isolated case has ni t been observed en any of the subsequent inspections.
Of the S ITr Grinnell units subject to testin;;, five have been tested and have perferned satisfactorily.
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Mr. nuhert W. Reid Page 2 November 30, 1978 The District believes that within the' rc,quirements of Technical Specification 4.14 4, this situation is clearly defined as isolated to Bergen-Faterson snubbers.
L.*ithin this specification, a letter is required from :;RC concurring that additional inspections of ITT Grinnell units are not necessary. The reply is required prior to completion of reactor building work which is scheduled for December 9, 1978.
Respectfu ly submitted,
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J. J. Mattimoc Assistance General M,anager and Chief Engineer JMM:RWC: jim cs: Region V Maggied bcs.
R. Rodriguez R. Oubre' R. Col'ombo J. McColligan P. Saito Rancho Seco File 4th floor Files b
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