Text

Attachment 2 - HI-STORM 100 Amendment 16 RAI Responses Batch 5 (Non-Proprietary)
	ML23013A340
Person / Time
Site:	Holtec
Issue date:	01/13/2023
From:	; Holtec
To:	; Office of Nuclear Material Safety and Safeguards
Shared Package
ML23013A337	List: ML23013A338; ML23013A340; ML23013A341; ML23013A342; ML23013A343; ML23013A344; ML23013A345; ML23013A346; ML23013A347;
References
	5014956, EPID L-2021-LLA-0039
	Download: ML23013A340 (1)
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Holtec Letter 5014956 Attachment 2 Holtec Response to Request for Additional Information (Batch 5)

Docket No. 72-1014 Holtec International HI-STORM 100 Multipurpose Canister Storage System Certificate of Compliance No. 1014 Amendment No. 16 RAI 4-5 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. 1014, appendix B, section 2.4.5, Fuel Loading Decay Heat Limits for UNVENTILATED OVERPACK, states, Tables 2.4-6a and 2.4-6b provide the maximum allowable decay heat per fuel storage location for MPC-68M in an UNVENTILATED OVERPACK. 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 MPC 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 100 CoC-1014 Appendix B Section 2.4.5 apply the same statements to the HI-STORM 100 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 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 Page 1 of 2

Holtec Letter 5014956 Attachment 2 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