ML19254D168
| ML19254D168 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse, Prairie Island, North Anna  |
| Issue date: | 10/05/1979 |
| From: | Ross D NRC - TMI-2 BULLETINS & ORDERS TASK FORCE |
| To: | Reed C COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 7910220460 | |
| Download: ML19254D168 (2) | |
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OCT 5 1979 Cordell iteed, Chaiman Westinghouse Operating Plants Owner's Group Comonwralth Edison P. O. Box 767 Chicago, Illinois 60690
Dear Mr. Reed:
The NRC staff is reviewing the responses to bulletins79-05C and 79-06C on the subject of the need for tripping of reactor coolant pumps for certain small break loss-of-ccolant accidents. The conclusions reached by the PWR vendors in those responses vary to a considerable degree, and are highlighted in Table 1.
To a degree these differences may be attributed to design differences. However, our present judgment is that the major differences are attributable to model differences, which are highlighted in Table 2.
The various RCP trip criteria that have been proposed or are believed to be in place are presented in Table 3.
A variety of model features have been developed without the use of relevant experiments to support model justification, and no model has been demonstrated to ba overall conservative by integral test comparison. There is apparent 1ick of agreement between vendors as to whether individual assumptions are c onservative. Given these model variations, it is not surprising that the con-clusions reached vary.
We have done some calculations with RELAP-4, Mod 7, and these are sumarized in Table 4.
These calculations, while useful to us, are not definitive, and cannot guide us as to what is a suitably conservative set of model assumptions.
Our concern is that during the pendency of traditional interactions between you and us (i.e., questions, positions, analyses, rebuttals, appeals, etc.) events are forcing a more prompt solution.
I refer to the RCP trip at North Anna (a non-LOCA transient) the RCP trip at Prairie Island (a steam generator tube failure) and the Davis-Besse transient of September 27, 1979 which nearly set in motion the requirements of 79-05C.
The second half of the concern I have relates to HPI tennination criteria. Table 5 lists several criteria proposed, in place, or thought to be in place. There is no apparent reason why the same set of safety considerations would lead us into more than one, unifom criterion for temination of HPI. Your assistance in achieving this desired state of unifomity is needed.
If the NRC were to adopt a Q&A approach to solving the problem separately, some candidate questi:ns are enclosed in Table 6.
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s OCT 5 1979
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Instead of withdrawing to the Table 6 approach, I suggest we meet soon and discuss, in an administrative sense, how the PWR regulated industry can close on these two issues. For further details regarding the issues described herein, as well as the planned meeting, Mr. Brian Sheron (301-492-7588) is available for further discussion.
Sincerely, h
D. F. Ross, Jr., Director Bulletins and Orders Task Force Office of Nuclear Reactor Regulation
Enclosures:
Table 1 - Conclusions Reached by PWR Vendors in Response to Bulletins79-05C and 79-06C Table 2 - Differences During SBLOCA with Pumps Running Table 3 - RCP Criteria Proposed or In-Place at Plants Table 4 - Staff Calculations for PWR Vendors Table 5 - HPI Temination Criteria Proposed or Ir.-Place at Plants Table 6 - Typical Questions on RCP Trip and HPI Temination Identical letters sent to:
George E. Liebler, Chaiman Ed Scherer, Manager, Licensing CE Owner's Group CE Power Systems CE Operating Plants Conbustion Engineering, Inc.
Florida Power and Light Company 1000 Prospect Hill Road P. O. Box 529100 Windosr, Connecticut 06095 Miami, Florida 33152 James H. Taylor Robert Gill, Chaiman Manager, Ltcensing TMI-2 Effects Subcocmittee Babcock and Wilcox B&W Owner's Group P. O. Box 1260 P. O. Box 2178 Lynchburg, Virginia 24505 422 South Church Street Charlotte, North Carolina 28242 Tom Anderson, Manager Nuclear Safety department Westinghouse Electric Corporation Box 355 Pittsburgh, Pennsylvania 15320 2 2C A
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