ML20151K092

Forwards Response to 970515 RAI Re TS Change to Moderator Temp Coefficient

ML20151K092
Person / Time
Site:	Calvert Cliffs
Issue date:	07/31/1997
From:	Cruse C BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-M95181, TAC-M95182, NUDOCS 9708050333
Download: ML20151K092 (5)

Text

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CH ARLES II. CHUSE Baltimore Gas and Electric Company Vice President Calvert Cliffs Nuclear Power Plant Nuclear Energy 1650 Calven Cliffs Parkway Lusby, Maryland 20657 410 495-4455 July 31,1997 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: Document Control Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Response to Request for Additional Information Regarding the Technical Specification Change to the Moderator Temperature Coefficient (TAC Nos. M95181 and M95182)

REFERENCE:

(a) Letter from Mr. A. W. Dromerick (NRC) to Mr. C. H. Cntse (BGE),

dated May 15,1997, Request for Additional Information Regarding the Technical Specification Change to the Moderator Temperature Coefficient (TAC Nos. M95181 and M95182)

In response to Reference (a), we are providing the additional information you requested.

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. Document Control Desk July 31,1997 Page 2 t

Should you have questions regarding this matter, we will be pleased to discuss them with you. '

Very truly yours, I

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STATE OF MARYLAND  :

TO WIT:

COUNTY OF CALVERT

1 I, Charles H. Cruse, being duly sworn, state that I am Vice President, Nuclear Energy Division, i Baltimore Gas and Electric Company (BGE), and that I am duly authorized to execute and file this l License Amendment Request on behalf of BGE. To the best of my knowledge and belief, the statements -  ;

contained in this document are true and correct. To the extent that these statements are not based on my ,

l personal knowledge, they are based upon information provided by other BGE employees and/or  :

l- consultants. Such information has been reviewed in accordance with company practi e and I believe it to be reliable. ,

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( AAk)bscribed andJMday

, this swornof before me, a Notary

/At&# .1997. Public in and for the State of Maryland a; i 0 i WITNESS my Hand and Notarial Seal: / 8 14 ) /h R Notary Public My Commission Expires: b Date CHC/ PSF / dim

Attachment:

(1) Response to Request for AdditionalInformation cc: R. S. Fleishman, Esquire H. J. Miller, NRC J. E. Silberg, Esquire Resident Inspector,NRC A. W Dromerick, NRC R. I. McLean, DNR Director, Project Directorate 1-1, NRC J. H. Walter, PSC

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ATTACHMENT (1) l Y

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,s RESPONSES TO REQUEST FOR ADDITIONAL INFORMATION l

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Calvert Cliffs Nuclear Power Plant July 31,1997

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ATTACHMENT (1)

RESPONSES TO REQUEST FOR ADDITIONAL INFORMATION l i

Ouestion 1:

l l On page 2 of the Afarch 28,1996, submittal, under the heading of the Licensing Basis, it is stated that the AfTC [ moderator temperature coefficient} value atfullpower and equilibrium xenon is negative. In the secondparagraph under the same heading, it is stated that since BGE [ Baltimore Gas and Electric Company} has installed the Diverse Scram System as a long term solution to A DVS (anticipated transient i without scram}. it is no longer necessaryfor BGE to design cores with a negative Af7C. Is it the intent of BGE to conduct an ADVS analysis with an Afic value different (more positive) to thet used in the original (present) CE [ Combustion Engineering} ADVS analysis?

Response

, in the March 28,1996 submittal (Reference 1) BGE requested that the maximum allowed positive full 4

power MTC in the Technical Specifications be reduced from +0.3 x 10" ApfF to +0.15 x 10 ApFF.

Baltimore Gas and Electric Company incorporated the more restrictive MTC in the analyses for the Calvert Cliffs Design Basis Events where appropriate. Baltimore Gas and Electric Company does not

, intend to conduct a revised ATWS analysis with a more positive MTC. Anticipated transient without scram is not a Design Basis Event for Calvert Cliffs, and an ATWS analysis has not previously been performed for Calvert Cliffs using the maximum positive MTC allowed by Technical Specifications.

The installation of a Diverse Scram System, Diverse Turbine Trip, and Diverse Auxiliary Feedwater i

Actuation System as required by the ATWS rule (10 CFR 50.62) maintains the probability and  !

consequences of an ATWS low. These plant modifications eliminate the need to consider ATWS a Design Basis Event. The Calvert Cliffs updated Probabilistic Risk Assessment demonstrates that ATWS is a relatively small contributor to the overall core melt risk for Calvert Cliffs. Therefore, a revised ATWS analysis is not necessary or required.

Ouestion 2: I Is the new Af7C value used in the ADVS analysis compatible uith the ADYS analysis performed to

, providefor the ADVS Rule. (i.e., is the new Af7C value compatible with the value CE used at the time the analysis was done to support the A DVS Rule?)

Response

A generic ATWS analysis for the Calvert Cliffs class of CE plants was performed in 1979 by CE at the

, Nuclear Regulatory Commission's (NRC's) request to support resolution of the ATWS issue. This analysis is documented in Reference (2). This analysis assumed an MTC more negative than -0.2 x 10" l AprF for 95% of the time. This analgis predicted a maximum Reactor Coolant System pressure of 4220 psia for an MTC equal to -0.2 x 10 ApfF.

The NRC reviewed Reference (2) as documented in Reference (3). Reference (3) lists numerous NRC comments on the Reference (2) analysis. As a result, both References (3) and (4), which was later used by NRC as a basis for the final ATWS rule, assume that the value of MTC for CE plants is such that the Service Level C limit (3200-3400 psia) will not be exceeded 50% of the time. Based on parametric studies contained in the Combustion Engineering Owners Group Best Estimate ATWS Scenarios and Success Criteria, BGE estimates the value of MTC for Calvert Cliffs that just causes the Service Level C limit to be exceeded is approximately -1 x 10" ' ,rF.

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ATTACHMENT (1) i RESPONSES TO REQUEST FOR ADDITIONAL INFORMATION l

The expected operating MTC under the proposed, more restrictive, Technical Specification requirement in Reference (1) is compatible with References (2) and (4). The normal operating full power MTC at the beginning-of-cycle for Calvert Cliffs is expected to remain negative. Since MTC decreases with time in cycle, this will cause the normal MTC to be more negative than -0.2 x 10" ApFF for approximately 95%

of the cycle, and more negative than -1 x 10" ApfF for approximately 50% of the cycle.

REFERENCES:

1. Letter from Mr. C. H. Cruse (BGE) to NRC Document Control Desk, dated March 28,1996, License Amendment Request: Change to the Moderator Temperature Coefficient

2. Combustion Engineering Repon CENPD-263-P, ATWS Early Verification, November 1979

3. NUREG-0460, Volume 4, Anticipated Transients Without Scram for Light Water Reactors, March 1980

4. SECY 83-293, Amendment to 10 CFR 50 Related to ATWS Events, Enclosure D,

" Recommendations of the ATWS Task Force", July 19,1983 W

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