ML19270B895
| ML19270B895 | |
| Person / Time | |
|---|---|
| Site: | Columbia, LaSalle, 05000000 |
| Issue date: | 03/23/1984 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Asselstine, Bernthal, Gilinsky, Palladino, Roberts NRC COMMISSION (OCM) |
| References | |
| TASK-AS, TASK-BN84-062, TASK-BN84-62 BN-84-062, BN-84-62, NUDOCS 8403140242 | |
| Download: ML19270B895 (3) | |
Text
s' CENTRAL FILES ONLY V.AR 2 31984 Docket Nos.: 50-373 50-374 50-397 MEMORANDUti FOR:
Chairman Palladino Comissioner silinsky Commissioner Roberts Commissioner Asselstine Commissioner Bernthal FROM:
Darrell G. Eisenhut, Director Division of Licensing
SUBJECT:
BWR CORE THERMAL HYDRAULIC STABILITY (B0ARD NOTIFICATION NO.84-062)
In accordance with NRC procedures for Board Notifications the enclosed infonnation is provided to the Comission. The enclosure is a description of recent thermal hydraulic stability tests at a foreton boiling water reactor. As stated in the enclosed memo current US BUR Technical Specifications place restrictions on US BWR single loop operation.
In addition, the GE calculations show that considerbble margin exists even with the large neutron flux oscillations. The staff is presently working with applicants and with BWR owners group in the review of BWR Technical Specifications regarding this issue.
By copy of this memorandum we are also informing all applicable BWR Atomic Safety and Licensing Boards, the appropriate BWR Atomic Safety and Licensing Appeal Boards and the corresponding parties.
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ar - but Darrell G. Ei.4enhut, Director Division of Licensing cc: See Next Page
Enclosure:
February 27, 1984 Memo Mattson to Eisenhut
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SECY (2)
OPE OGC EDO Clinton ASLB (Clark, Ferguson, Paris)
Perry ASLB (Block, Bright, Kline)
Perry ASLAB (Kohl, Buck, Edles)
Shoreham ASLB (Brenner, Ferguson, Morris)
Shoreham ASLAB (Rosenthal, Edles, Wilber)
Zimer ASLB (Frye, Hooper, Livingston)
Parties to the proceedings
Branch service lists of addresses receiving material on the following dockets for BN 84-067:
CLINT0H DOCKET Mr. Daniel I. He. corn Mr. D. P. Hall Mr. George Wuller Mr. Julius Greier Resident Inspector Mr. R. C. Heider Mr. F. C. Downey PERRY DOCKET Mr. Murray R. Edelman Donald H. Hauser, Eso.
Resident Inspector Regional Administrator, Pegion III SHOREHAM DOCKET Pr. M. S. Pollock Pesident Inspector Energy Research Group, Inc.
Mr. James Rivello Ezra 1. Bialit Dr. M. Stanley Livingstone ZIMMER DOCKEi Mr. Edwin.1. Wagner Mr. Gregory C. Ficke Mr. Robert Burger Mr. 'ohn E. Dolan George E. Pattison, Esq.
Mr. Waldman Christianson Mr. John Youkilis Pegional Administrator, Pegion 111 Fr. James P. Fenstermaker
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DISTRIBUTION LIST FOR BOARD NOTIFICATION Clinton Unit 1, Docket No. 50-461 Perry Units la2, Docket Nos. 50-440/441 Shoreham Unit 1, Docket No. 50-322 Zimmer Unit 1, Docket No. 50-358 Vernon Adler Gustave A. Linenberger, Jr.
ACRS Members Martin Bradley Ashare, Esq.
Mr. Herbert H. Livermore Dr. Robert C. Axtmann Edward M. Barrett, Esq.
Terry J. Lodge, Esq.
Mr. Myer Bender Lynne Bernabei, Esq.
David K. Martin, Esq.
Dr. Max W. Carbon Howard L. Blau, Esq.
Mr. Brian McCaffrey Mr. Jesse C. Ebersole Peter B. Bloch Janine M yden, Esq.
Mr. Harold Etherington Ms. Nora Bredes William J. Moran, Esq.
Dr. William Kerr Lawrence Brenner, Esq.
Dr. Peter A. Morris Dr. Harold W. Lewis Mr. Glenn 0. Bright Chris Nolin Dr. J. Caron Mark Herbert H. Brown, Esq.
Fabian G. Palomino, Esq.
Mr. William M. Mathis John G. Cardinal, Esq.
Dr. Oscar H. Paris Dr. Dade W. Moeller Brian Cassidy, Esq.
Spence Perry, Esq.
Dr. David Okrent Hugh K. Clark, Esq.
Mr. Samuel H. Porter Dr. Milton S. Plesset Hon. Peter Cohalan W. Taylor Reveley, III, Esq.
Mr. Jeremiah J. Ray Troy B. Conner, Jr., Esq.
Dr. Peter F. Riehm Dr. Paul C. Shewmon Gerald C. Crotty, Esq.
Ken Robinson, Esq.
Dr. Chester P. Siess Andrew B. Dennison, Esq.
Alan S. Rosenthal, Esq.
Mr. David A. Ward James B. Doegherty, Esq.
Alan Samelson, Esq.
Mr. Jay Dunkleberger Cherif Sedky, Esq.
Anthony F. Earley, Jr.
Ralph Shapiro, Esq.
Gary J. Edles, Esq.
Mr. Frederick J. Shon Peter S. Cverett, Esq.
Jay Silberg, Esq.
Donald T. Ezzone, Esq.
Mr. Robert F. Warnick Jonathan D. Feinberg, Esq.
Mrs. Deborah Webb, Esq.
Dr. George A. Ferguson Howard A. Wilber Lawrence R. Fisse, Esq.
Philip L. Willman, Esq.
Ms. Jean Foy John D. Woliver, Esq.
Leon Friedman, Esq.
Gary N. Wright Eleanor L. Frucci, Esq.
Sheldon A. Zabel, Esq.
Mr. John H. Frye III Stewart M. Glass, Esq.
MHB Technical Associates Marc W. Goldsmith Norman L. Green, Esq.
Atomic Safety and Licensing Bruce L. Harshe Board Panel W. Peter Heile, Esq.
Atomic Safety and Licensing Susan Hiatt Appeal Panel
. Timothy S. Hogan, Jr.
Docketing and Service Section Dr. Frank F. Hooper Document Management Branch Dr. W. Reed Johnson Dr. Jerry R. Kline Christine N. Kohl Stephen B. Latham, Esq.
James A. Laurenson t
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2 7 1934 FEB MEMORANDUM FOR:
D. G. Eisenhut, Director Division of Licensing FROM:
Roger J. Mattson, Director Division of Systems Integration SU3 JECT:
30ARD NOTIFICATION - BWR CORE THERMAL HYDRAULIC STABILITY l.
Item for Notification The staff has been informed by General Electric (GE) of recent thermal hydraulic stability tests at a foreign reactor, a boiling water reactor with relatively high power density, which demon-strated the occurrence of limit cycle neutron flux oscillations at natural circulation and several percent above the rated rod line.
It was predicted that limit cycle oscillations vould occur at the operating state tested and the oscillations were observable on the APRMs and suppressed through control rod insertion. The charac-teristics of the observed oscillations, however, were different than those previously observed in other stability tests.
Excmi-nation of the detailed data of this test showed that some LPRMs oscillated out of phase with the APRM signal and at an amptitude as great as six times the core average measured by the APRMs.
These data are important since they confirm the possibility of local thermal-hydraulic instabilities which have been postulated but not observed in similar stability tests performed in the United States.
The staff is presently working with applicants and with the BWR Owners Group to review the standard Technical Specifications to assure that they properly protect against the potential for insta-bilities.
If changes are to be required, they would follow staff procedures for generic Technical Specification changes, including CRGR review.
2.
Relevancy and Materiality Stability tests on a BWR/4 reactor demonstrated that limit cycle oscillations can occur within permissable operating space below the rated rod line at natural circulation flow.
The high power level (120 percent) scram protection which is based on APRM signals would not necessarily prevent violation of critical heat flux (CHF) limits if local instabilities occur.
Contact:
G. Schwenk, DSI:CPB X-29421 MMCM D CF 3pp.
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or D. G. Eisenhut Core designs are known to decrease in thermal hydraulic stability with higher power density and with higher gap conductance which is associated with fuel designs having smaller fuel pin diameters.
The conditions which led to local instabilities in the foreign test rather than global oscillations with all fuel assemblies in phase are not clear. Until core stability behavior can be better pre-dicted and explained, the staff believes that the new information showing that local oscillations non-characteristic of the APRM signals may occur is relevant to all BWR designs, but is of greater significance to those having higher power density and lower damping characteristics as typified by the BWR/4, BWR/5, and BWR/6 designs.
3.
Significance of Test Information ihe test demonstrated that local thermal hydraulic oscillations which are out of phase with the APRMs can occur.
This raises the possibility of local oscillations occurring in the plant which might not be detected by the operator without monitoring of LPRM signals and/or LPRM upscale alarms.
It is unclear at this time how high a local oscillation could grow before detection by an operator using current monitoring procedures.
Since we cannot predict the limiting magnitude for such an oscillation, we can not be certain that CHF limits would not be exceeded.
It is for this reason that we will examine BWR Technical Specifications to assure that they provide adequate assurance that operating regions of potential instability are avoided and that neutron oscillations of unac-ceptable magnitude are detected and suppressed.
The staf f concludes that the uc* information from the foreign stability tests does nat pose an immediate safety concern for continued BWR operation prior to orderly examination and possible change of Technical Specifications for the reasons which follow:
(a) Current BWR Technical Specifications place restrictions on operation under conditions of natural circulation or single loop operation such that the frequency of operation in regions with low stability margin is very low.
In addition, the core designs for most operating reactors are sufficiently stable that limit cycle operations are believed to be unlikely even in the less stable permissible operating regimes.
Even if such oscillations should occur, it is believed that the high power level APRM scram protection would be adequate in most cases.
(b) The magnitude of thermal hydraulic instability induced neutron flux oscillations is considerably hi gher than the oscillations in the average cladding heat flux because of delays caused by the fuel thermal time constant.
General Electric Company
D. G. Eisenhut @ 2 719M calculations for the case where the neutron flux oscillates up to 120 percent of rated (RPS trip point) indicate that the surface heat flux has a peak oscillation amplitude of only 5 pt.rcent of its rated value. Thus, a considerable margin exists to safety limits even if very large neutron flux oscillations occur.
(c) The oscillations are readily detectable with proper monitoring and can be easi'y suppressed by inserting control rods.
(d) General Electric Company is in the process of providing to all its operating plants guidance on the proper methods to monitor for thermal hydraulic instabilities and on the actions that should be taken to suppress such oscillations if they shouid occur. BWR owners have been made aware of the problem and of pending actions.
4.
Relation to Projects The foreign stability test results relate to all BWR reactors.
It is recommended that appropriate boards be notified of the new information and of the staff's plans to work with the BWR appli-cants and licensees to assure that the Technical Specifications for all BWRs properly protect against the potential- {or instabilities.
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/'G. Sex O al m Roger J. P ttson, Director Division of Systems Integration