ML20133M247

Forwards Discussion Re History of Pipe Vibration Problems at Facility,Per 790314 Request

ML20133M247
Person / Time
Site:	Beaver Valley, 05000000
Issue date:	04/05/1979
From:	Harold Denton Office of Nuclear Reactor Regulation
To:	Gilinsky NRC COMMISSION (OCM)
Shared Package
ML20133M133	List: IA-85-301, Forwards Draft Temporary Instruction Providing Guidance for Inspecting & Evaluating Licensee & CP Holder Responses to IE Bulletin 79-14, Seismic Analysis for As-Built.... Comments Requested by 790723.Supporting Documentation Encl ML20133M130 ML20133M162 ML20133M174 ML20133M190 ML20133M211 ML20133M223 ML20133M232 ML20133M247 ML20133M261 ML20133M293 ML20133M428 ML20133M451 ML20133M483 ML20133M505 ML20133M523 ML20133M555 ML20133M575 ML20133M607 ML20133M621 ML20133M635 ML20133M646 ML20133M662 ML20133M685 ML20133M699 ML20133M722 ML20133M737 ML20133M757 ML20133M771 ML20133M786 ML20133M842 ML20133M853 ML20133M891 ML20133M908 ML20133M919 ML20133M959 ML20133M996 ML20133N121 ML20133N130 ML20133N148 ML20133N166 ML20133N203 ML20133N381 ML20133N390 ML20133N407 ML20133N418 ML20133N421 ML20133N434 ML20133N440
References
FOIA-85-301 NUDOCS 8508130057
Download: ML20133M247 (4)

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NUCLEAR REGULATORY COMM!sslON AI RECOR FCOPY y

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'APR 5 1979 i

MEMORANDUM FOR:

Comissioner Gilinskyt ' siened) T. A.PM THRU: xecutive Director for Operations FROM: , Harold R. Denton, Director Office of Nuclear Reactor Regulation

SUBJECT:

BEAVER VALLEY WATER HAMMER AND PIPE VIBRATION PROBLEMS Enclosed is a discussion of the history of pipe vibration problems at Beaver Valley in response to your March 14, 1979 request.

h Harold R. Denton, Director Office of Nuclear Reactor Regulation

Enclosure:

Vibration History at Beaver Valley Unit 1 cc w/ enclosure:

Chairman Hendrie Comissioner Kennedy Comissioner Bradford Comissioner Aheyne S. Chilk, SECY

. Policy Evaluation General Counsel

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1 i 8508130057 850703 PDR FOIA HERRMAN85-301 PDR

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RESPONSE TO COMMISSIONER GILINSKY ON VIBRATION HISTORY ,

AT THE BEAVER VALLEY UNIT 1 NUCLEAR POWER STATION During November 1976 through January 1977, the feedwater pipe system (the secondary side) of the Beaver Valley Nuclear Plant experienced large vibratory loads (approximate pressure oscillation 400 psi at 17HZ) on three occasions (November S. December 27,1976'and January 5, 1977). 'These vibratory loads were not due to water hammer caused by two phase flow instability at the steam generator feed ring but were generated by hydraulic instability due to unstable feedwater flow control during power changes. The feedwater pipes did not fail .during these incidents but damage to two snubbers, some pipe supports and instrumentation tubing lines was sustained.

Hydraulic instability was caused by an inadequate design of the internals of the feedwater flow control valves and these vibrations were not related to the errors in the design steming from incorrect pipe stress calculations. The problem of hydraulic instability was ,

resolved by changing the valve internals. Actual vibratory test data made available to the staff substantiated resolution of the problem.

Examination -

A stress analysis based on these. vibratory loads was performed- .

onkneaffectedpipes. The affected pipes were located both inside and outside containment. From the stress analysis the magnitude and O

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the location (on the pipes) of the three highest stressed areas were.

identified. These highest stress areas were radiographed for the pipes inside containment while the pipes outside containment were magnetic

, partical and liquid penetrant inspected. This examination showed no -

indication of damage.

As a result of the vibrations, the integrity of the piping system supports was questioned. Based on the original stress analysis performed i

when plant was being designed by Stone and Webster, the Architect Engineer (AE), a quality assurance check was made of the support of the main feedwater line. This quality assurance check revealed t' hat i

six hydraulic shock suppressors were undersized with respect to seismic load requirements established by the original pipe stress analysis.

The results of the original pipe stress analysis were not compared with the stress analysis performed at the time of the events (1977) because the dynamic loads used in the original stress analysis considered .

seismic loads while the latter considered loads due to hydraulic . -

instabilr.y that occurred during the event. As a result of the anomalies found in the pipe supports of the main feedwater line, the licensee and AE expanded the review to cover 2,000 support points tr'; aghout other category I pipe systems.

Of these 2,000 supports,' .

a :ctal of 29 could not be accepted based on the original stress analysis and the restraints at these points were either replaced or i

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3-modified in early 1977. Other supports, not on safety systems, were also examined at that time and found acceptable on the same basis.

All failed. (resulting from the event) or undersized pipe supports and snubbers were replaced or repaired.

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