B12383, Submits Addl Clarification of Util 861030 Response to NRC Request for Addl Info Re Proposed Amend to License DPR-65, Allowing Storage of Consolidated Spent Fuel in Spent Fuel Storage Pool,Per NRC 861208 Request

Submits Addl Clarification of Util 861030 Response to NRC Request for Addl Info Re Proposed Amend to License DPR-65, Allowing Storage of Consolidated Spent Fuel in Spent Fuel Storage Pool,Per NRC 861208 Request

ML20207L591
Person / Time
Site:	Millstone
Issue date:	01/02/1987
From:	Mroczka E NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	Thadani A Office of Nuclear Reactor Regulation
References
B12383, TAC-61658, NUDOCS 8701120248
Download: ML20207L591 (3)

Text

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General Offices

• Seiden Street, Berlin. Connecticut E Ev'vi7d N eo-a~= P.O. BOX 270

• * **'Na wa HARTFORD. CONNECTICUT 06141-0270 L L j ((^ "j' Z"","," ',",

, (203) 665-5000 January 2,1937 Docket No. 50-336 B12383 Office of Nuclear Reactor Regulation Attn: Mr. Ashok C. Thadani, Director PWR Project Directorate #8 Division of PWR Licensing - B U.S. Nuclear Regulatory Commis'sion Washington, D.C. 20555 Gentlemen:

Millstone Nuclear Power Station, Unit No. 2 Storage of Consolidated Spent Fuel In May,1986,(1) Northeast Nuclear Energy Company (NNECO) submitted to the NRC Staff a request to amend its operating license, No. DPR-65, for Millstone Nuclear Power Station, Unit No. 2, to allow the storage of consolidated spent fuel in the Unit No. 2 spent fuel storage pool. As a result of the NRC Staff review of this proposal (2)the NRC responded NNECO Staff forwarded to thistorequest NNECO in aa Request letter dated for Additional Information.

October 30, 1986.(3) On December 8,1986, the NRC Staff provided a draf t of the results of the review of NNECO's response and requested additional clarification to one of the responses. The purpose of this letter is to provide the NRC Staff the requested information.

Review of Response to Request for Additional Information (RAI)

In the response to RAI Question #3.2.1, NNECO assumes that no lateral deformation results from a 100,000 lb load impacting the fuel assembly. This assumption is not justified and seems invalid since they have determined that the guide tubes are yielded due to the load. A random drop is likely to create an (1) 3. F. Opeka letter to A. C. Thadani, dated May 21,1986, " Millstone Nuclear Power Station, Unit No. 2 Proposed Change to Technical Specifications Storage of Consolidated Fuel."

(2) D. H. Jaffe letter to 3. F. Opeka, dated August 27,1986, " Technical Evaluation Report Millstone Unit No. 2 - Storage of Consolidated Spent Fuel Technical Specification Change Docket No. 50-336."

(3) 3. F. Opeka letter to A. C. Thadani, dated ' October 30,1986, " Millstone Nuclear Power Station, Unit No. 2 Storage of Consolidated Spent Fuel."

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eccentric load and th'us increase the likelihood of buckling occurrmg in the guide tubes and the fuel rods. In addition, crushed guide tubes could conceivable damage and exert lateral loads on adjacent fuel rods. .The response to the question is thus inadequate.

Response to Review Based on geometric constraints and available maximum clearances, an eccentric drop of the consolidated fuel cannister (CFC) is not possible. Due to the length of the CFC (155%"), the length (10") the CFC has to travel in the cell prior to impacting the fuel assembly, and the available clearances between the CFC and cell wall (max clearance = 0.375"), a non-axial drop would result in rigid body rotation of the CFC. Rigid body rotation results in the CFC impacting the cell walls. An impact onto the cell walls has been analyzed and found to be acceptable. An axial drop of the CFC onto a stored fuel assembly will result in the floor of the CFC impacting the upper end fitting posts of the fuel assembly.

The C-E analysis considered this impact condition.

The analysis performed by C-E ev'aluated the maximum dynamic impact load in the stored fuel assembly due to a 28" drop of a fully loaded consolidated fuel storage box. The analysis was conservative because it did not take credit for the following factors that reduce the. magnitude and minimize the effect of lateral loading on the fuel rods:

1) Under dynamic loading conditions the effective strength of the guide tube and fuel rod are increased.

2) At any instant in time, the maximum impact load is not distributed throughout the entire fuel assembly.

3) Significant fuel rod loading can only occur after the guide tube axial length is reduced by 1.262" (close axial gap between upper end fitting and fuel rods); and all the lateral gaps in a row of fuel rods and the gap between the fuel assembly and CFC are closed.

4) Spacer grid cell wall deformation dissipates lateral load. The spacer grids fail in bending rather than buckling therefore minimizing the transfer of load to the fuei rods.

5) Lateral deformation of the fuel storage cell wall dissipates lateral load.

6) The drop analysis of the consolidated fuel storage box neglected energy losses occurring in the storage box.

3 We trust you will find the above information satisfactory and we remain available to assist in your review.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY E.J.A)ffczka (/

SeniorLVice President 1

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