ML19353A069
| ML19353A069 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 12/18/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Rich Smith VERMONT YANKEE NUCLEAR POWER CORP. |
| References | |
| NUDOCS 8101070060 | |
| Download: ML19353A069 (1) | |
Text
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UNITED STATES YA
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Docket No. 50-271 Vermont Yankee Nuclear Power Corporation DEC 181980 ATTN:
Mr. Robert L. Smith gj Licensing Engineer a
y 25 Research Drive N
Westborough, Massachusetts 01581 A
Gentlemen:
The enclosed Supplement No. 4-to IE Bulletin No. 80-17, " Failure of Control Rods to Insert During a Scram at a BWR" is forwarded to you for action.
A written response is required.
In order to assist the NRC in evaluating the value/ impact of each Bulletin on licensees, it would be helpful if you would provide an estimate of the manpower expended in conduct of the review and preparation of the report (s) required by the Bulletin.
Please estimate separately the manpower associated with corrective actions following identification of problems through the Bulletin.
If you desire additional information regarding this matter, please contact this office.
Sincerely, ktYl/Q-Na hYAn ce H. Grier irector
.a
Enclosures:
1.
Supplement No. 4 to IE Bulletin No. 80-17 2.
List of Recently Issued IE Bulletins CONTACT:
D. L. Caphton (215-337-5265) l cc w/encis:
Mr. Warren P. Murphy, Plant Superintendent i
Mr. W. F. Conway, Vice President and Manager of Operations Mr. J. E. Griffin, President t
Mr. L. H. Heider, Vice President 1
810107o O@
c SSIHS No.:
6820 Accession No.:
8006190074 UNITED STATES IEB 80-17 Sup. 4 NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCENENT WASHINGTON, D.C.
20555 December 18, 1980 IE Supplement 4 to Bulletin No. 80-17:
FAILURE OF CONTROL ROUS TO INSERT DURING A SCRAM AT A BWR NRC staff evaluation of failures of the continuous mor;itoring system (CMS) for the scram discharge volume (SDV) at an operating BWR has identified the need for licensee actions in addition to those requested by IEB 80-17 and Supplements 1-3.
The purpose of these actions is to provide assurance that the CMS has been tested to demonstrate operability as installed, remains operable during plant operation, and is periodically surveillance tested to demonstrate continued operability.
The occurrence of CMS failures at Dresden Nuclear Power Station was discussed in IE Information Notice 80-43, which was issued on December 5,1980 to those operating BWR's with CMS recently installed.
Subsequently, investigation into the cause of the failure to receive the alarm with the SDV essentially full revealed several items which required correction, including:
1.
Excess portions of transducer cable were placed in physical positions which would increase external noise sensitivity.
2.
The UT transducers were not placed in a physical position to optimize system sensitivity.
3.
A certain amount of " cross-talk" was occuring between redundant trans-ducers located a few feet apart on the same run of 4" pipe.
Station and vendor personnel shortened and rerouted transducer cables to improve noise rejection.
Vendor specialists optimized transducer placement and synchronized both transducers to the same ultrasonic instrument internal clock to minimize cross-talk and improve signal to noise characteristics.
Following these actions the CMS appeared to faction properly.
Further difficulties were encountered when apparently minor quantities of water leaked into the SDV as a result of control rod drive scram valve maintenance activities and minor scram outlet valve leakage.
It appears that the trans-ducers are located on a section of SDV piping which forms a local low point.
Accordingly, small amounts a depth which triggers the high level alarm (at t
volume. The licensee in it specific analysi:; for a e arm point to 2-1/2".
The sys DUPLICATE DOCUMENT alarm time delay was also Entire documenti previously entered into system under:
ANO _ SQQ(#N dC~lM No. of pages: _
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