B11889, Forwards Confirmation of Resolution to Request for Addl Info Re Application for Increased Spent Fuel Storage Capacity Based on Series of Telcons

Forwards Confirmation of Resolution to Request for Addl Info Re Application for Increased Spent Fuel Storage Capacity Based on Series of Telcons

ML20137R881
Person / Time
Site:	Millstone
Issue date:	11/25/1985
From:	Opeka J NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	Butcher E Office of Nuclear Reactor Regulation
References
TASK-2.E.4.2, TASK-TM B11889, TAC-44864, TAC-59294, NUDOCS 8512060107
Download: ML20137R881 (3)

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HARTFORD. CONNECTICUT 06141-0270 L L j [ *' [ '," [ ' g " (203) 665-s000 November 25,1985 Docket No. 50-336 Bi1889 Director of Nuclear Reactor Regulation At tn: Mr. Edward J. Butcher, Chiei Operating Nuclear Reactors Branch No. 3 Division of Licensing U.S. Nuclear Regulatory Commission Washington, D. C. 20555 Gentlemen:

Millstone Nuclear Power Station, Unit No. 2 Followup to Request for Additional Information on Spent Fuel Storage Capacity During thq review process of the Northeast Nuclear Energy Company (NNECO) response ((l) to a Request for Additional Information sent by the Staff in October 2), five followup questions were posed by the Staf f and resolved dui.ng a series of telephone conference calls.

The purpose of this letter is to document the resolution established during those calls and to provide the Staff with written answers to each of the questions discussed.

Attachment A contains a summary of the questions and responses. We trust that this information is satisfactory to the Staff.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY h . F. &d_

J. F. Opdka U Senior Vice President (1) 3. F. Opeka !ctter to E. J. Butcher, " Millstone Nuc! car Power Station, Unit No. 2 Reply to Request for Additional Information on Spent Fuel Storage Capacity," dated October 28,1985.

(2) E. J. Butcher letter to J. F. Opeka, " Request for Additional Information on Spent Fuel Storage Capacity for Millstone Unit No. 2," dated October 3,1985.

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,r Docket No. 50-336 Bf1889 Attachment A Summary of Question Responses Provided Verbally in Connection with the Review of Millstone Unit No. 2 Application for increased Spent Fuel Storage Capacity November,1985

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Question 1: Were non-symmetric fuel loadings in the racks considered?

Answer: Non-symmetric fuel loadings were considered by analyzing partially loaded modules. The most severe cases considered were those modules with a single row of cells along an edge of the module loaded with fuel.

Question 2: Describe what constitutes the worst case for tipping.

Answer: The worst case for tipping was a Region 117x8 module, partially loaded with fuel, excited by the East-West seismic component (7 cell direction). The worst case for shear load was a Region 11 7x9 module fully loaded with fuel, excited by the North-South seismic component (9 cell direction).

Question 3: Describe the analyses done to show that adjacent modules do not contact during a seismic event.

Answer: The maximum horizontal displacement of the top of a module, including tipping, is determined from a non-linear time history analysis of an individual module. Separate analyses are made for a number of different modules with varying degrees of fuel loading, including empty, partially loaded, and fully loaded modules. In these individual module time history analyses, all the modules in the pool are assumed to move in-phase when determining the rack-to-pool hydrodynamic characteristics.

Question 4: How is the tipping calculated by the CESHOCK non-linear analysis accounted for in the three dimensional stress analysis?

Answer: The horizontal non-linear CESHOCK analyses determine the tipping associated with fully and partially loaded fuel racks.

Load factors are used to transfer the vertical and horizontal base loadings from the two dimensional CESHOCK non-linear analyses to the linear three-dimensional model which has been modified to represent the tipped condition. A separate load factor is calculated to represent the base movement developed during tipping of the racks.

The vertical tipping displacement from the horizontal non-linear analysis is used as the input to a separate vertical non-linear CESHOCK model that is used to calculate vertical impact loads. These loads are used to determine the adequacy of the foot / rack design.

Question 5: Was the normal loading stress of the rack on the concrete of the pool floor considered?

Answer: The local loading under the rack feet and the total pool load due to the rack loads were considered in the evaluation of the concrete spent fuel pool structure. The concrete stresses due to the rack loads were compared to the allowable concrete stresses set forth in the American Concrete Institute's " Code Requirements for Nuc! car Safety Related Concrete Structures (ACI 349 80) and found to be within code allowables. The detailed procedure which discusses the application of the rack loads when investigating the concrete was presented in the response to question lic.