ML20126L172
| ML20126L172 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 07/25/1985 |
| From: | Mihalcik J BALTIMORE GAS & ELECTRIC CO. |
| To: | Jaffe D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8507310090 | |
| Download: ML20126L172 (2) | |
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B ALTIMORE G AS AND ELECTRIC COMPANY P.O. BO X 14 7 5 B A LTIM O R E'. M A R Y L A N D 21203 LVERT CL FS NUCLEA WER PLANT LussY. MARYLAND 20657 July 25,1985 Mr. D. H. Jaffe Operating Reactors Branch 3 Division of Licensing U.S. Nuclear Regulatory Commission Washington, D.C. 20555
SUBJECT:
Large Break LOCA ECCS Performance Evaluation
REFERENCE:
A. E. Scherer (CE) to G. W. Knighton (NRC) letter, LD-85-031, July 2,1985 Dear Mr. Jaffer This letter is to inform you that we have been notified by Combustion Engineering (C-E) of a potential non-conservatism in one element of the C-E large break loss-of-coolant accident (LOCA) evaluation model. The particular element in question is the treatment of axial power distribution and peaking factor. C-E further stated that this potential non-conservatism applied to all plants for which C-E had performed ECCS performance evaluations using their large break LOCA model. C-E also notified the Commission of their finding via the referenced letter.
During a meeting at the NRC offices in Bethesda on July 10,1985, C-E provided detailed information on this subject as well as a status summary for those plants for which C-E still provides the large break LOCA evaluations. Of particular importance was their i
estimate of an increase in peak clad temperature due to the non-conservatism (for their System 80 Standard Design) of approximately 34 F. While a plant speelfic sensitivity has not been determined for Calvert Cliffs, estimates are that the increase would be of the same order of magnitude.
The reported peak clad temperature calculated for Calvert Cliffs Unit 1 (without 0
consideration of the subject non-conservatism) is 1896 F.
This provides a margin of 0
304 F to the 2200 F acceptance criteria value of 10 CFR 50.46. A more recent LOCA l
analysis (still without consideration of the subject nonconservation) for Unit 1 which fully implements the credit obtainable from using the PARCl! code calculates the LOCA peak 0
clad temperature at 1836 F. This provides an even larger margin of 369 F.
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July 25,1985 i
Mr. D. II. Jaffe l
Fage 2 The reported peak clad temperature calculated for Calvert Cliffs Unit 2 is 2038"F. This provides a margin of 102 P to the 2200 F acceptance criterin. The LOCA analysis just completed for Unit 2 Cycle 7 without consideration of the subject non-conservatism calculates a peak clad temperature of 1945, which provides a margin of 255 F.
With this much margin on both units, incorporation of a more ndverse axlat power distribution would not be expected to increase peak clad temperature to a value approaching the regulatory limit. For this reason we believe that the current ECCS performance evaluation continues to demonstrate compliance with the acceptance criteria of 10 CFil 50.40.
Since the current C-E Evaluation Model used to perform the ECCS cynluntion may not strictly comply with the requirement of Appendix K for use of an axial power distribution and peaking factor which produces the most severe eniculated consequences, the NIIC Indicated (in the July 10 meeting) that it is not deemed as an neceptable tool for demonstrating compliance to 10 CFit 50.46.
Ilecause of this position we will be discussing this issue further with C-H and, if necessary, a schedule for submitting new analyses employing an evaluation model thnt is in full compliance with the regulations will be determined.
Due to the need to allow C-E time to talk with each of its nffceted utility customers and efficiently schedule the work to be done, while at the same time necommodating the needs and reload schedules of Individual utilities, we ennnot provide a schedule date for l
this effort at this time. We do, however, expect to provide that Information to you l
within forty-five days from the date of this !ctter.
(MAi g.j A. Mihalcik Edel Cycle Management JAM /Imt
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