ML23076A274

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

ML23076A274
Person / Time
Site:	Holtec
Issue date:	03/17/2023
From:	Holtec
To:	Office of Nuclear Material Safety and Safeguards, Document Control Desk
Shared Package
ML23o76A271	List: ML23076A274
References
5014960, CAC 001028, EPID L-2021-LLA-0039
Download: ML23076A274 (1)

Text

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 e xplicitly 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 belo w 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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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 3-3

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

Holtec RAI Response:

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

The 3-D LS-DYNA modelling approach, methodology, assumptions, and pad size for tip-over analysis of HI-STORM 100 UVH are same as the licensing basis model [per HI-2188448, ANALYSIS OF THE NON-MECHANISTIC TIPOVER EVENT OF THE LOADED HI -STORM 100S VERSION E STORAGE CASK under HI-STORM 100 Licensing Amendment Request 15, LAR 1014 -15] previously approved by NRC.

Questions on RAI 3-3 raised during the clarification call

The NRC asked for some clarification on RAI 3 -3 during a clarification call with Holtec on 3/2/2023 (ADAMS Accession Number ML23076A113). The NRC requested clarification on the following points:

1. provide explanation of what has changed in the LS-DYNA tipover model to reduce the maximum concrete pad penetration,

2. provide the updated LS-DYNA model files for the MPC-32M tipover analysis, and

3. verify the average basket deflection of the MPC-32M (which had a higher maximum fuel basket strain during tipover than the MPC-68M) is acceptable or bounded by the example MPC-68M calculation provided in the updated calculation package.

Holtec RAI Response:

1) In revision 1 of the calculation HI-2210290, the finite element model of the target including the concrete pad for both designs of MPCS (MPC-32M and MPC-68M) is updated in order to correspond to the licensing basis model. The finer mesh with better hourglass control is used for concrete pad. It is also ensured that the hourglass energy for the ISFSI pad is well below (less than 3%) the total internal Page 2 of 3

energy. These enhancements to the tipover model improved ISFISI pad deflection result.

2) LS-DYNA simulation files (input and result) for the MPC-32M tipover analysis and the MPC-68M tipover analysis will be provided separately.

3) The dimensionless parameter of basket deformation for the MPC-32M is also evaluated and is shown to meet the basket deflection limit. The same measure is also added in calculation package (HI-2210290R2). The proposed FSAR changes are updated to reflect the correct revision of the calculation package.

RAI 3-4

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

Holtec RAI Response:

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

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