AECM-85-0272, Forwards Response to NRC 850726 Request for Addl Info Re Amend to License NPF-29,allowing Installation of High Density Spent Fuel Racks.Tech Spec Section 4.5 Changed to Conform to Ref Design Used in Analysis

Forwards Response to NRC 850726 Request for Addl Info Re Amend to License NPF-29,allowing Installation of High Density Spent Fuel Racks.Tech Spec Section 4.5 Changed to Conform to Ref Design Used in Analysis

ML20134N267
Person / Time
Site:	Grand Gulf
Issue date:	08/30/1985
From:	Dale L MISSISSIPPI POWER & LIGHT CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
AECM-85-0272, AECM-85-272, TAC-57619, NUDOCS 8509050066
Download: ML20134N267 (3)

Text

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• t MISSISSIPPI POWER & LIGHT COMPANY Helping Build Mississippi EsIhMhMMdB P. O. B O X 164 0, J AC K S O N MIS SIS SIP PI 39215-1640 August 30, 1985 NUCLE AR LICENSING & $AFETY DEPARTMENT U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, D. C. 20555 Attention: Mr. Harold R. Denton, Director

SUBJECT:

Grand Gulf Nuclear Station Unit 1 Docket No. 50-416 License No. NPF-29 File: 0260/M-181.1 High Density Spent Fuel Racks -

Response to Criticality Question AECM-85/0272 By letter dated May 6, 1985 (AECM-85/0143) Mississippi Power & Light (MP&L) requested an amendment to License NPE-29 to allow for the installation of high density spent fuel racks at Grand Gulf Nuclear Station Unit 1. By letter dated July 26, 1985 the NRC staff requested additional information regarding the criticality acceptance criterion presented in the amendment request.

MP&L's response to the staff's request is provided as an attachment to this letter. MP&L considers the attached clarification to be responsive to the staffs concern. If there are additional questions, please contact this office.

Yours truly, L. F. Dale Director MLC/JGC:vog Attachment cc: (See Next Page) 8509050066 G50830 PDR ADOCK 05000416 P PDR I\

J13AECM85082902 - 1 Member Middle South Utilities System

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AECM-85/0272 Page 2 y

ec: Mr. J. B. Richard (w/a)

Mr. O. D. Kingsley, Jr. (w/a)

Mr. R. B. McGehee (w/a)

Mr. N. S. Reynolds (w/a)

Mr. H. L. Thomas (w/o)

Mr. R. C. Butcher (w/a)

Mr. James M. Taylor, Director '(w/a) -

-Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission

-Washington, D.'C. 20555 Dr. J. Nelson Grace, Regional Administrator (w/a)

U. S. Nuclear Regulatory Commission

. Region II 101 Marietta St., N. W., Suite 2900 Atlanta, Georgia 30323 r

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REQUEST FOR ADDITIONAL INFORMATION -

GRAND GULF SPENT FUEL POOL EXPANSION (TACS 57619)

QUESTION:

The proposed acceptance criterion for storage in the racks is that the Kee of a fuel assembly shall not be greater than 1.395 when calculated at the most reactive point in the assembly life in the core geometry at a temperature of 20 C. This Koo value is based on a calculation with a fresh 8 X 8-2 water rod assembly having uniform enrichment in the remaining rods. There are two sources of bias or uncertainty in this calculation which have not been treated. First is the effect on the rack Koo of different assembly designs having the same value of Koo as calculated for the core geometry.

The second source (presumably a bias) arises from the fact that the values of K co assigned to the reload fuel will presumably be those provided by the fuel vendor (General Electric, e.g.) and calculated by their methods, which are different from the ones used to obtain the 1.395 value.

Please provide a discussion of these phenomena to address the magnitude of the uncertainties involved or to support a conclusion that the analyses provided are conservative.

RESPONSE

In Section 4.5, " Acceptance Criteria for Criticality," the criteria as originally submitted was believed to be a very conservative limit since (1) no credit for the presence of gadolinium or reduction in reactivity due to burn-up was claimed (see page 4-2) and (2) the reference reactivity of the spent fuel storage rack was expected to be conservative (overpredicted) by as much as 0.034 K (see page 4-6). Thus the limiting fuel assembly Koo of 1.395 in the standard core geometry was to have been evaluated for fresh unburned fuel withoat gadolinium present. The gadolinium burnable poison actually present would reduce the true reactivity by an amount adequate to compensate for any uncertainty in assembly design or bias in vendor calculations. Other evaluations (i.e., CASMO-2E and SCALE calculations) indicate that with gadolinium present, the true reactivity, at the most reactive point in the assembly life, would be less than 0.95 by 4% A K or more depending upon the gadolinium loading.

Nevertheless, to preclude the potential confusion of different assembly designs and reliance upon vendor calculations, Section 4.5 is changed to conform to the reference design used in the analysis and to read as follows:

"4.5 Acceptance Criteria for Criticality The USNRC letter of April 14, 1978, to all Power Reactor Licensees, and the draft revision to Regulatory Guide 1.13 specify that the neturon multiplication factor in spent fuel pools shall be less than or equal to 0.95, including all uncertainties, when fully loaded with fuel of the highest anticipated reactivity. For BWR type fuel (8 X 8 array),

with an average enrichment (uniform) of 3.5 wt% U-235 or less, the spent fuel storage rack described herein satisfies this criterion, with a maximum reactivity conservatively estimated to be 0.937 including all uncertainties."

J14NMEREP 035 SPENT FUEL POOL - 1