ML19269E873
| ML19269E873 | |
| Person / Time | |
|---|---|
| Issue date: | 06/06/1979 |
| From: | Snaider R Office of Nuclear Reactor Regulation |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7906290754 | |
| Download: ML19269E873 (3) | |
Text
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UNITED STATES
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Jane 6, 1979
's, MEMORANDUM FOR:
D. G. Eisenhut, Deputy Director, Division of Operating Reactors, NRR THRU:
D. K. Davis, Chief, Systematic Evaluation Program Branch, 00R FROM:
R. P. Snaider, Systematic Evaluation Program Branch, 00R
SUBJECT:
SUMMARY
OF MAY 30, 1979 MEETING WITH GENERAL ELECTRIC TO DISCUSS RESOLUTION OF GENERIC BWR FEEDWATER N0ZZLE ISSUES On Wednesday, May 30, 1979, representatives of the General Electric Company (GE) met with members of the NRC staff and a representative of Brookhaven National Laboratory (BNL), a consultant for the NRC, to discuss the major unresolved issues regarding the generic BWR feedwater nozzle cracking problem. A list of attendees is attached.
The three major areas in which resolution is required are new sparger/
thermal sleeve vibration testing and analysis, fracture mechanics margins to failure, and itemization of benefits accrued from system changes with or without the removal of clad and installation of the GE sparger/ thermal sleeve.
The question of vibration was dis ~ cussed at length; the original sparger problems had begun with cracking because of sparger arm vibration. GE has determined that the forged-tee modification is a major improvement over the original junction-box design and their experimental evidence gives weight to this conviction. However, BNL expressed concern that no analysis was. performed to determine the natural frequency of the sparger/
thermal sleeve and that all external. driving forces inherent to reactor operation may not have been included. GE responded by noting that the experimental flow sweep technique was sufficiently slow to allow any resonant frequencies to peak in amplitude. Also, the GE plan and model upon which the testing was based took into account all known. reactor condi-tions and in fact increased the severity of these conditions. The NRC staff noted that the NRC's inservice inspection program, to be published with the forthcoming NUREG document, would take into account the need to periodically examine those component locations deemed most susceptible to cracking by vibration.
2142 086 79062907 O C
D. G. Eisenhut June 6, 1979 Regarding the margins of safety inherent in the GE linear elastic fracture mechanics analysis, GE has revised what had been previously submitted in their generic program reports. The revision was acceptable to the NRC staff in that the bases for a fracture mechanics margin to failure, denoted A, are now explained, as is the derivation of this margin.
The NRC had questioned whettier feedwater system physical modifications and changes to operating procedures, by themselves, might result in benefits which wc,uld equal or outweigh those of combined clad removal and installa-tion of the new thermal sleeve /sparger.
In response, GE demonstrated that the fatigue usage factors, by analysis, are such that the system changes alone will not protect the plant. However, these changes may be necessary tologertheusagefactorstoacceptablevaluesonplantswhichhavelow
(%340 F) feedwater temperatures during operation.
The last portion of the meeting was devoted to additional comments.from the BNL representative. One particular area of concern was the GE hypothesis of " leak before break", which,.although now supported lay limited experimental data, appears to be non-conservative because of recent theoretical informa-tion on the shape of the crack-propagation front. The NRC noted that this is a moot point, for in practice the allowable crack depths are substantially less than those which would challenge the theories; the NRC's inspection program reflects this fact and is conservative.
The GE representatives noted all of the areas on which minor disagreement remains or on which additional clarification is necessary and stated that GE will provide a revision to the already-submitted generic documents.
Such a revision will be processed by GE as rapidly as possible.
Richa
. Sna der Systematic E,aluation Program Branch Division of Operating Reactors
Attachment:
As stated O
2142 087
ATTENDANCE LIST R. P. Snaider, NRC R. Mattu, NRC R. Johnson, NRC S. MacKay, NRC N. Randall, NRC
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M. Subudhi, BNL H. Watanabe, GE C. Dillmann, GE O
2142 088
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DISTRIBUTION FOR MEETING SUMMARIES
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NRC PDR Central Files
-:TEBA-SEPB Reading NRR Reading H. Denton E. Case
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V. Stello D. Eisenhut R. Vollmer W. Russell B. Grimes T. Carter T. Ippolito R. Reid G. Knighton V. Noonan A. Schwencer' D. Ziemann D. K. Davis G. Lainas J. Scinto, OELD OI&E (3)
ACRS (16)
Licensees NRC Participants J. McEwen, KMC R. Schaffstall, KMC R. Klecker W. Hazelton M. Hum S. Hanauer R. P. Snaider C. Hofmayer R. Mattu R. E. Johnson S. MacKay N. Randall
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M. Subudhi, BNL A. Watanabe, GE C. Dillman, GE 2142 089
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