ML20072L390
| ML20072L390 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 03/28/1983 |
| From: | Mihalcik J BALTIMORE GAS & ELECTRIC CO. |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| NFM-83-124, NUDOCS 8303310270 | |
| Download: ML20072L390 (3) | |
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'B ALTIMORE G AS AND ELECTRIC COMPANY P.O. B O X 147 5 B A LTIM O R E. M A R YL A N D 21203 HUCLEAR POWER DEPARTMENT CALVERT CLIFFS NUCLEAR POWER PLANT LUSEY, M ARYLAND 20657 March 28,1983 NFM 83-124 Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 ATI'ENTION: Mr. R. A. Clark, Chief Operating Reactors Branch #3 Division of Licensing
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit 1, Docket No. 50-317, DPR-53 Application of HERMITE Methodology to the Steam Line Break Analysis for Cycle 7 Gentlemen:
The sixth refueling outage for Calvert Cliffs Unit 1 will begin October 1,1983, with a j
planned startup date of late November 1983.
We anticipate providing the reload submittal within the normal 90 day lead time. In line with our goal of obtaining bounding l
cycle design parameters such that future reloads can be done on a 10 CFR 50.59 basis, we have contracted witt our vendor to apply the HERMITE computer code to the steam line break (SLB) analysis. Although HERMITE will be new on the Calvert Cliffs docket, it is not new to the NRC technical reviewers. The following paragraphs will review the need for HERMITE and its development. This discussion will include how it has been applied to other dockets. We ask you,to concur with our conclusion that HERMITE methodology applied to SLB can be folded in to a routine reload license submittal.
Need for HERMFFE The need to apply the HERMITE methodology to steam line break (SLB) analysis is attributed to recent design and analysis changes at the Calvert Cliffs plant. Specifically, l
the requirement to trip reactor coolant pumps (RCPs) following an accident and a design that uses more negative moderator temperature coefficient have made the consequences of the SLB more severe. The requirement to trip RCPs is a TMI modification and the more negative temperature coefficient results from longer cycle lengths. Because of these added constraints, the current steam line break analysis which relies on 2D PDQ or ROCS to develop an isothermal reactivity versus temperature curve with a stuck CEA will not provide a bounding analysis for future cycles.
1 In the past submittals of the SLB analysis used a core average density reactivity. With this method the local moderator temperature is not related to the local power generated in the vicinity of the stuck control rod and no Doppler or moderator feedback is OO 8303310270 830328
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DR ADOCK 05000317 p
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s March 28,1983 NF M 83-124 o
Page 2 credited. Since the assumed stuck rod and moderator inlet temperature tilt tend to concentrate power in one part of the core, the greatest moderator temperature increase I
occurs under the stuck rod where it has the most effect on reactivity. Since distributing these effects uniformly over the core results in too small a negative reactivity " benefit" from a return to power, three dimensional methods were developed to more accurately model this effect.
HERMFTE I
2 IIERMITE was approved for use by the NRC in June of 1976. As originally presented it was a three dimensional time dependent four group diffusion theory code which solved the neutronics by use of finite element methods and included feedbacks of fuel temperature, coolant temperature, coolant density and control rod motion. The code initially assumed closed channels. The thermal hydraulle portign of the code was 4
upgraded three or four years ago by incorporation of the TORC 8 computer model.
TORC is an open channel thermal hydraulic model which takes into consideration the channel cross flows. This ersion was applied to the St. Lucie 2 steam line break which you have already approved 6
The recently approved ROCS /DIT topica1 introduced the nodal expansion method (NEM) of solving the neutronics equation. The new nodal expansion method has proved to be much faster and more accurate than the finite difference technique originally used in HERMITE to solve the neutronics equations.
Conclusion We anticipate that after review of this letter along with the referenced documents you will concur that the use of the HERMITE code in the SLB accident does not constitue new methodology and can be folded into a routine reload license application.
Very truly yours, 00 k
.(. %. Mihalcik Nticlear Fuel Management JAM /Imt ec: J. A. Biddison, Esquire G. F. Trowbridge, Esquire D. H. Jaffe - NRC R. R. Mills - CE R. E. Architzel-NRC/CC l
March 28,1983 NFM 83-124 Page 3 Footnotes 1.
CENPD-188-A "HERMITE Space-Time Kinetics", June 1976.
2.
O. D. Parr to A. E. Scherer letter dated June 10, 1976, Staff Evaluation of CENPD-188.
3.
CENPD-161-P " TORC Code, A Computer Code for Determining the Thermal Margin of a Reactor Core", July 1975.
4.
CENPD-206-P ' TORC Code, Verification and Simplification Methods", January 1977.
S.
St. Lucie 2 FSAR Ch.13.
6.
CENPD-266-P "The ROCS and DIT Computer Codes for Nuclear Design", December 1981.
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