Text

Attachment 2: HI-STORM FW Amendment 7 RAI Responses Part 4 (Non-Proprietary)
	ML23006A266
Person / Time
Site:	07201032
Issue date:	01/06/2023
From:	; Holtec
To:	; Office of Nuclear Material Safety and Safeguards
Shared Package
ML23006A263	List: ML23006A264; ML23006A266; ML23006A267; ML23006A268; ML23006A270; ML23006A274;
References
	EPID L-2021-LLA-0053, 5018101, CAC 001028
	Download: ML23006A266 (1)
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Page 1 of 3 Holtec Response to Request for Additional Information (Part 4)

Docket No. 72-1032 Holtec International HI-STORM FW Multipurpose Canister Storage System Certificate of Compliance No. 1032 Amendment No. 7 RAI 4-14 Clarify the meaning of, A minor deviation from the prescribed loading pattern in an MPCs permissible contents to allow one slightly thermally-discrepant fuel assembly per quadrant []., (e.g., the change in decay heat) and provide a bounding thermal analysis to show that the peak cladding temperature limits in interim staff guidance ISG-11 Rev. 3 and the important to safety (ITS) component temperature limits are met.

CoC No. 1032, appendix B, section 2.3.2, Fuel Loading Decay Heat Limits for UNVENTILATED OVERPACK, states, Tables 2.3-9A and 2.3-9B provide the maximum allowable decay heat per fuel storage location for MPC-37. Tables 2.3-10A and 2.3-10B provide the maximum allowable decay heat per fuel storage location for MPC-89. Table 2.3-13 provides the maximum allowable decay heat per fuel storage location for MPC-44.

The per cell limits in these tables apply to cells containing undamaged fuel or damaged fuel in DFCs/DFIs or fuel debris in DFCs. A minor deviation from the prescribed loading pattern in an MPCs permissible contents to allow one slightly thermally-discrepant fuel assembly per quadrant to be loaded as long as the peak cladding temperature for the MPC remains below the ISG-11 Rev 3 requirements is permitted for essential dry storage campaigns to support decommissioning.

It is not clear to staff what the actual meanings of: 1) a minor deviation, or 2) one slightly thermally-discrepant fuel assembly are, or 3) how it has been demonstrated through a bounding thermal analysis that the peak cladding temperature limits and ITS component temperature limits are still met should thermally-discrepant fuel assemblies be loaded in the multipurpose cask as described.

This information is needed to determine compliance with 10 CFR 72.236(f).

Holtec RAI Response:

These statements were originally approved for the Ventilated Overpack in HI-STORM FW CoC-1032 Appendix B Amendment 5 Section 2.3.1. In the Amendment 5 SER (ML20163A701) Section 4.6 it is explained that the Staff accepted this Clarification E4 as it would have a negligible impact to the thermal performance of the System since the PCT will be below the limits in SFST-ISG-11. The currently proposed changes to the FW CoC-1032 Appendix B Section 2.3.2 apply the same statements to the Unventilated Overpack. There is no difference between the application of these CoC statements to the Ventilated versus the Unventilated Overpacks.

This text allows for a minor deviation from the prescribed loading patterns approved in the CoC. A slightly thermally-discrepant fuel assembly is an allowable fuel assembly type with a decay heat of few watts more than that allowed in the CoC. This could be due to miscalculation of the decay heat or inadvertent placement in the wrong basket storage cell. Additionally, allowance of such deviations is requested to be permitted in no more than one location per quadrant to limit this flexibility. The minor deviation is not quantified in the CoC because ultimately the overall acceptance criteria on the PCT and other ITS components in the FSAR will still Holtec Letter 5018101 Attachment 2

Page 2 of 3 have to be satisfied. The ultimate goal in such a case is to demonstrate that the safety of the system is assured.

In order for this deviation to be acceptable, thermal analysis using the approved model in the FSAR will be performed to compute its impact of any such minor deviation in the heat load(s). Such a deviation will only be acceptable if the result of this analysis demonstrates that the peak cladding temperature (PCT) and other components are below the temperature limits in the FSAR.

The thermal model and principal methodology will also remain applicable to an MPC with a thermally-discrepant fuel assembly (or assemblies). Irrespective of the minor deviations in decay heat, the PCT and component temperatures are limited to those prescribed in the FSAR. The acceptance criteria can be considered self-limiting. Additionally, the thermal model developed following the methodology presented in the FSAR is robust to capture the physical phenomenon even with minor deviations in the decay heat.

RAI 9-2