ML23005A004

Attachment 2 - HI-STORM 100 Amendment 16 Response to Request for Additional Information (Batch 4)

ML23005A004
Person / Time
Site:	Holtec
Issue date:	01/04/2023
From:	Holtec
To:	Office of Nuclear Material Safety and Safeguards
Shared Package
ML23005A000	List: ML23005A001 ML23005A002 ML23005A004 ML23005A006
References
EPID L-2021-LLA-0039, 5014954
Download: ML23005A004 (1)

Text

Holtec Letter 5014954 Attachment 2 Holtec Response to Request for Additional Information (Batch 4)

Docket No. 72-1014 Holtec International HI-STORM 100 Multipurpose Canister Storage System Certificate of Compliance No. 1014 Amendment No. 16 RAI 3-1 Provide justification that no structural issues will occur due to not tightening the overpack lid bolts of the HI-STORM 100 unventilated with high density concrete (UVH) overpack.

The proposed safety analysis report (SAR) changes in section 2.IV.0 indicate that the overpack lid bolts are not tightened and retain a small axial clearance to allow any developed overpack cavity pressure to release by lifting the overpack lid off the gasket. The SAR does not provide discussion on how this design feature may affect structural performance under off-normal or accident conditions.

The untightened bolts could be subjected to more lid motion and impact forces during dynamic events.

Provide explanation of what bolt clearance is imposed, justification that the untightened lid does not provide additional structural demands on the lid bolts under earthquake or other dynamic loads, and that the overpack lid remains attached after tip-over to perform its shielding safety function.

This information is required to determine compliance with 10 CFR 72.236(c), 72.236(d), and 72.236(l).

Holtec RAI Response:

The most critical structural load on the HI-STORM cask and its internals, i.e. the MPC and the fuel basket, results from the non-mechanistic cask tipover accident. All of the component parts of the HI-STORM cask including the closure lid bolted joint are explicitly represented in the finite element model used for the cask tipover analysis. The finite element (LS-DYNA simulation) model does not consider any preloading on these bolts reflecting the actual design wherein the closure lid bolts are not tightened.

Likewise, all other structural analyses including lifting, missile impacts, snow load, etc. do not rely on closure lid bolt tightening (preloading) to demonstrate structural adequacy of the HI-STORM closure lid system.

The HI-STORM UVH cask design calls for a small axial clearance at the bolting location, as noted on the Dwg. 12233, in order to relieve any pressure build up in the cask cavity. The axial clearance is expected to be less than 1/2. This has no adverse effect on the structural function of the cask. The tipover analysis demonstrates that the MPC does not come in contact with the closure lid during the event, so the bolts are only required to resist the inertial load of the closure lid, which is a small fraction of the total cask weight. Morevoer, during the cask tipover accident event in case the closure lid opens, this small opening (< 0.5 inch) will not adversely affect the shielding performance of the cask. This is largely because the cask internals, i.e. the MPC and the fuel, remain far below the closure lid bottom surface. In addition, the shielding limit during an accident event is significantly higher than the normal condition limit.

Therefore, not tightening the lid bolts during HI-STORM loading and leaving a small axial clearance, has no adverse structural effects.

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Holtec Letter 5014954 Attachment 2 RAI 3-2 Provide complete licensing drawing information for the HI-STORM 100 UVH in the FSAR.

The applicant provided drawing 12233 revision 0 for HI-STORM 100 UVH in the application. Additional details on the critical dimensions requiring quality inspection, tolerances, and welds were provided in the proprietary report HI-2210277, HI-STORM 100 UVH Critical Dimension Report. However, drawing 12233 does not include these details.

Update licensing drawings to include the details from the critical dimension report or reference the report in the FSAR.

This information is required to determine compliance with 10 CFR 72.230(a).

Holtec RAI Response:

Reference to the HI-2210227 HI-STORM 100 UVH Critical Dimension Report has been added to HI-STORM 100 FSAR Section 1.IV.5. Furthermore, upon review of the Critical Dimension Report in response to this RAI, Holtec has identified several errors where items listed in Table 4.1 of the Critical Dimension Report are listed as shown in the corresponding licensing DWG-1223. The HI-2210227 Critical Dimension Report has been revised to list those items as Not Shown in the licensing DWG-12233.

RAI 5-3

[ PROPRIETARY INFORMATION WITHHELD IN ACCORDANCE WITH 10CFR2.390 ]

Holtec RAI Response:

[ PROPRIETARY INFORMATION WITHHELD IN ACCORDANCE WITH 10CFR2.390 ]

RAI 5-4

[ PROPRIETARY INFORMATION WITHHELD IN ACCORDANCE WITH 10CFR2.390 ]

Holtec RAI Response:

[ PROPRIETARY INFORMATION WITHHELD IN ACCORDANCE WITH 10CFR2.390 ]

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