ML23321A249

Attachment 3: Holtec International - HI-STORM FW FSAR Proposed Revision Ioj, Changed Pages (non-proprietary)

ML23321A249
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Site:	07201032
Issue date:	11/17/2023
From:	Holtec
To:	Office of Nuclear Material Safety and Safeguards
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5018111, EPID L-2021-LLA-0053, CAC 001028
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Holtec Letter 5018111 Attachment 3 The ASME Code service limits are used in the structural analyses for definition of allowable stresses and allowable stress intensities, as applicable. Allowable stresses and stress intensities for structural analyses are tabulated in Chapter 3. These service limits are matched with normal, off-normal, and accident condition loads combinations in the following subsections.

The MPC confinement boundary is required to meet Section III, Class 1, Subsection NB stress intensity limits. Table 2.2.10 lists the stress intensity limits for Design and Service Levels A, B, and D for Class 1 structures extracted from the ASME Code. Table 2.2.12 lists allowable stress limits for the steel structure of the HI-STORM FW overpack and HI-TRAC VW transfer cask which are analyzed to meet the stress limits of Subsection NF, Class 3 for loadings defined as service levels A, B, and D are applicable.

2.2.6 Loads Subsections 2.2.1, 2.2.2, and 2.2.3 describe the design criteria for normal, off-normal, and accident conditions, respectively. The loads are listed in Tables 2.2.7 and 2.2.13, along with the applicable acceptance criteria.

2.2.7 Design Basis Loads Where appropriate, for each loading type, a bounding value is selected in this FSAR to impute an additional margin for the associated loading events. Such bounding loads are referred to as Design Basis Loads (DBL) in this FSAR. For example, the Design Basis External Pressure on the MPC, set down in Table 2.2.1, is a DBL, as it grossly exceeds any credible external pressure that may be postulated for an ISFSI site.

2.2.8 Allowable Limits The stress intensity limits for the MPC confinement boundary for the design condition and the service conditions are provided in Table 2.2.10. The MPC confinement boundary stress intensity limits are obtained from ASME Code,Section III, Subsection NB. The displacement limit for the MPC fuel basket is expressed as a dimensionless parameter defined as [2.2.11]

=

w where is defined as the maximum permanent deflectiontotal deflection sustained by the basket panels under the loading event and w is the nominal inside (width) dimension of the storage cell.

The limiting value of is provided in Table 2.2.11, and it is also used conservatively to inform the criticality analysis model for the MPC fuel baskets, as described in Subsection 6.3.1. In addition to the deflection based criterion, the maximum primary membrane plus bending stress in the fuel basket panels, within the active fuel region, shall not exceed 90% of the ultimate strength of Metamic-HT material, at the applicable temperature and on a true stress basis, when evaluated HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Revision 10JH 2-93 1 of 17

Holtec Letter 5018111 Attachment 3 using plastic analysis. Both the maximum permanent deflection limit and the primary stress limit must be satisfied to insure overall structural integrity of the fuel basket.

Finally, the steel structure of the overpack and the HI-TRAC VW must meet the stress limits of Subsection NF of ASME Code,Section III for the applicable service conditions.

The following definitions of terms apply to the tables on stress intensity limits; these definitions are the same as those used throughout the ASME Code:

Sm: Value of Design Stress Intensity listed in ASME Code Section II, Part D, Tables 2A, 2B and 4 Sy: Minimum yield strength at temperature Su: Minimum ultimate strength at temperature HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Revision 10JH 2-94 2 of 17

Holtec Letter 5018111 Attachment 3 3.1 STRUCTURAL DESIGN 3.1.1 Discussion The HI-STORM FW system consists of the Multi-Purpose Canister (MPC) and the storage overpack (Figure 1.1.1). The components subject to certification on this docket consist of the HI-STORM FW system components and the HI-TRAC VW transfer cask (please see Table 1.0.1). A complete description of the design details of these three components are provided in Section 1.2. This section discusses the structural aspects of the MPC, the storage overpack, and the HI-TRAC VW (including Versions V and V2) transfer cask. Detailed licensing drawings for each component are provided in Section 1.5.

(i) The Multi-Purpose Canister (MPC)

The design of the MPC seeks to attain three objectives that are central to its functional adequacy:

• Ability to Dissipate Heat: The thermal energy produced by the stored spent fuel must be transported to the outside surface of the MPC to maintain the fuel cladding and fuel basket metal walls below the regulatory temperature limits.

• Ability to Withstand Large Impact Loads: The MPC, with its payload of nuclear fuel, must withstand the large impact loads associated with the non-mechanistic tipover event.

• Differential Thermal Expansion (DTE): The stress arising from the differential thermal expansion between the fuel basket and the MPC shell is mitigated by providing a prescribed nominal gap at their interface locations. The radial gap is selected to produce modest local compatibility stresses at the basket panel-to-shell junction, if not eliminate them.

Accordingly, the maximum interference between the fuel basket and the MPC enclosure vessel due to DTE must not exceed the limit values specified in Table 3.1.15. These limits ensure that no significant distortion occurs and any resulting interference stresses are peak stresses per NB-3213.11 and NB-3213.13(b), which are important only in determining the cyclic fatigue life of the component. Since the temperature fluctuations inside the cask storage cavity are relatively minor, as discussed in Paragraph 3.1.2.5, fatigue failure is not a credible concern for the MPC canister or the CBS basket. The DTE between various cask components at maximum design basis heat load is evaluated in Section 4.4.6 of Chapter 4.

which are classified as peak stresses in NB-3213.11 and NB-3213.13(b) that produce no significant distortion, and are important only in determining the cyclic fatigue life of the component. The magnitude of the peak stress will vary at the different basket panel-to-shell interface locations and with the canisters heat generation rate. At low heat loads and ambient conditions, a positive gap will exist at most interface locations. The progressive reduction in the gap with increasing heat load ensures improved heat transmission across the basket-to-shell interface which enhances the thermal capacity.

As stated in Chapter 1, the MPC Enclosure Vessel is a confinement vessel designed to meet the stress limits in ASME Code,Section III, Subsection NB. The enveloping canister shell, baseplate, and the lid system form a complete Confinement Boundary for the stored fuel that is referred to as HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10J9 3-3 3 of 17

Holtec Letter 5018111 Attachment 3 Table 3.1.14 KEY INPUT DATA FOR ANSYS MODEL OF MPC ENCLOSURE VESSEL Item Value Overall Height of MPC 195 in (for maximum length BWR fuel) 213 in (for maximum length PWR fuel)

Outside diameter of MPC 75.75 in MPC upper lid thickness 4.5 in MPC lower lid thickness 4.5 in MPC shell thickness 0.5 in MPC baseplate thickness 3.0 in Material Alloy X Ref. temperature for material properties Figure 3.4.27 (implemented in ANSYS)

Table 3.1.13 (implemented in LS-DYNA)

Table 3.1.15 ALLOWABLE INTERFERENCE BETWEEN FUEL BASKET AND MPC ENCLOSURE VESSEL DUE TO DIFFERENTIAL THERMAL EXPANSION UNDER NORMAL STORAGE CONDITIONS Direction Limit Value Radial 0.030 max.

Axial 0.000 max.

Nominal cold gap must exceed DTE in axial direction. No interference is allowed.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10J9 3-42 4 of 17

Holtec Letter 5018111 Attachment 3 3.4.3.3 Safety Evaluation of Lifting Scenarios As can be seen from the above, the computed factors of safety have a large margin over the allowable (of 1.0) in every case. In the actual fabricated hardware, the factors of safety will likely be much greater because of the fact that the actual material strength properties are generally substantially greater than the Code minimums. Minor variations in manufacturing, on the other hand, may result in a small subtraction from the above computed factors of safety. A part 72.48 safety evaluation will be required if the cumulative effect of manufacturing deviation and use of the CMTR (or CoC) material strength in a manufactured hardware renders a factor of safety to fall below the above computed value. Otherwise, a part 72.48 evaluation is not necessary. The above criterion applies to all lift calculations covered in this FSAR.

3.4.4 Heat The thermal evaluation of the HI-STORM FW system is reported in Chapter 4.

a. Summary of Pressures and Temperatures Design pressures and design temperatures for all conditions of storage are listed in Tables 2.2.1 and 2.2.3, respectively.

Differential Thermal Expansion The effect of differential thermal expansion among the constituent components in the HI-STORM FW system is considered in Chapter 4 wherein the temperatures necessary to perform the differential thermal expansion analyses for the MPC in the HI-STORM FW and HI-TRAC VW casks are computed. The material presented in Section 4.4 demonstrates that a constraint to free expansion due to differential growth between discrete components of the HI-STORM FW system (e.g., storage overpack and enclosure vessel) will either not develop or not lead to significant thermal stresses.

i. Normal Hot Environment Results presented in Section 4.4 demonstrate that initial gaps between the HI-STORM FW storage overpack or the HI-TRAC VW transfer cask and the MPC canister, and between the MPC canister and the fuel basket, will not lead to significant thermal stresses in any components due to DTE under normal operating conditions. In most cases, the initial gap is greater than the calculated DTE, which eliminates the possibility of thermal stresses related to restraint of thermal expansion. Only the DTE results for the MPC-37 CBS and MPC-89 CBS fuel baskets exceed the minimum combined radial gap at maximum design basis heat load. The maximum interference, however, is quite small, as reported in Table 4.4.6, and it is less than the prescribed limit in Table 3.1.15, as discussed in Subsection 3.1.1. The magnitude of the peak stress will vary at the different basket panel-to-shell interface locations and with the canisters heat generation rate. At low heat loads and ambient conditions, a positive gap will exist at most interface locations. The progressive reduction in the gap with increasing heat load ensures improved heat transmission across the basket-to-shell interface, which enhances the heat removalthermal capacity and mitigates the interference stresses. Therefore, HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10J9 3-85 5 of 17

Holtec Letter 5018111 Attachment 3 2

IA d (1 ) = Mgr sin 1

2 d1 which can be integrated over the limits 1 = 0 to 1 = 2f (Figure 3.4.8). The final angular velocity 1 at the time instant just prior to contact with the ISFSI pad is given by the expression 2 Mgr 1 ( t B) = (1 - cos 2 f )

IA where, from Figure 3.4.8, d

2 f = cos-1 2r This equation establishes the initial conditions for the final phase of the tip-over analysis; namely, the portion of the motion when the cask is decelerated by the resistive force at the ISFSI pad interface. Using the data germane to HI-STORM FW (Table 3.4.11) and the above equations, the angular velocity of impact is calculated as 1 ( t B) = 1.45 rad/sec The LS-DYNA analysis to characterize the response of the HI-STORM FW system under the non-mechanistic tipover event is focused on threetwo principal demonstrations, namely:

(i) The permanent lateral deflectiondeformation of the basket panels in the active fuel region is less than the limiting value in Table 2.2.11.

(ii) The maximum primary membrane plus bending stress in the fuel basket panels, within the active fuel region, shall not exceed 90% of the true ultimate strength of Metamic-HT material at the applicable temperature per Subsection 2.2.8.

(ii)(iii) The impact between the MPC guide tubes and the MPC does not cause a thru-wall penetration of the MPC shell.

ThreeFour LS-DYNA finite element models are developed to simulate the postulated tipover event of HI-STORM FW storage cask with loaded MPC-37, MPC-44, MPC-89 and MPC-32ML with standard fuel baskets, respectively. The three LS-DYNA models are constructed according to the dimensions specified in the licensing drawings included in Section 1.5; the tallest configuration for each MPC enclosure type is considered to ensure a bounding tipover analysis. Because of geometric and loading symmetries, a half model of the loaded cask and impact target (i.e., the ISFSI pad) is considered in the analysis. The LS-DYNA models of the HI-STORM FW overpack and the MPC are described in Subsections 3.1.3.1 and 3.1.3.2, respectively. The tipover analysis for MPC-44 is HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10J9 3-103 6 of 17

Holtec Letter 5018111 Attachment 3 As shown in Figure 3.4.15 and [3.4.31], the fuel basket does not experience significant plastic deformation in the active fuel region to exceed the acceptable limits; plastic deformation is essentially limited locally in cells near the top of the basket beyond the active fuel region for the MPC-37, MPC-44, MPC-89 and MPC-32ML standard baskets. Nonetheless, to insure compliance with the allowable limit in Subsection 2.2.8, the maximum permanent deflection of the most heavily loaded basket panel, at any elevation within the active fuel region, is obtained from the LS-DYNA solution and reported in Table 3.4.19 for the MPC-37, MPC-89 and MPC-32ML fuel baskets. The fuel basket is considered to be structurally safe since it can continue maintaining appropriate spacing between fuel assemblies after the tipover event. The MPC enclosure vessel experiences minor plastic deformation at the impact locations with the overpack guide tubes; the maximum local plastic strain (10.9%, see Figure 3.4.16) is well below the failure strain of the material and smaller than the plastic strain limit (i.e., at least 0.2 for stainless steel) recommended by [3.4.6] for ASME NB components. Similarly, local plastic deformation occurs in the overpack shear ring near the cask-to-pad impact location as shown in Figure 3.4.17. However, the shielding capacity of overpack will not be compromised by the tipover accident and there is no gross plastic deformation in the overpack inner shell to affect the retrievability of the MPC. In addition, the cask closure lid bolts are demonstrated to be structurally safe after the tipover event, only a negligibly small plastic strain is observed in the bolt near the impact location (see Figure 3.4.18). Therefore, the cask lid will not dislodge after the tipover event. Finally, Figures 3.4.19 and 3.4.20 present the deceleration time history results of the cask lid predicted by LS-DYNA. The peak rigid body decelerations measured for the HI-STORM FW lid concrete are shown to be 65.4 gs in vertical direction and 19.3 gs in the horizontal direction. Note that the deceleration time histories are filtered using the LS-DYNA built-in Butterworth filter with a cut-off frequency of 350 Hz; the same filter was used for the HI-STORM 100 non-mechanistic tipover analysis [3.1.4].

The structural integrity of the HI-STORM FW lid (standard, Version XL, domed, and Version E) cannot be ascertained from the LS-DYNA tipover analyses since some components of the lid, namely the lid outer shell and the lid gussets, are defined as rigid members in order to simplify the modeling effort and maintain proper connectivity. Therefore, separate structural analyses have been performed for the HI-STORM FW lid (standard, Version XL, domed, and Version E) using ANSYS, wherein a bounding peak rigid body deceleration established based on LS-DYNA tipover analysis results is statically applied to the lids. The finite element model is identical to the one used in Subsection 3.4.3 to simulate a vertical lift of the HI-STORM FW lid (Figures 3.4.5A, 3.4.5B, 3.4.5C, and 3.4.5D), except that the eight circumferential gussets are conservatively neglected (i.e.,

deleted from the finite element model for the standard lid).

The resulting stress distributions in the HI-STORM FW lids (standard, Version XL, domed, and Version E) are shown in Figures 3.4.21A through 3.4.21G Per Subsection 2.2.3, the HI-STORM FW lids should not suffer any gross loss of shielding as a result of the non-mechanistic tipover event. To satisfy this criterion, the primary membrane stresses in the lid components are compared against the material yield strength. The most heavily loaded component in the standard lid is the upper shim plate closest to the point of impact (Figure 3.4.21A). In order to determine the primary membrane stress in the upper shim plate, the stresses are linearized along a path that follows the outside vertical edge of the upper shim plate (see Figure 3.4.21A for path definition). Figure 3.4.22A shows the linearized stress results. Since the membrane stress is less than the yield strength of the material at HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10J9 3-105 7 of 17

Holtec Letter 5018111 Attachment 3

• Case 1: HI-STORM FW loaded with MPC 37 fuel basket, without corner welds, all basket panels have matching tabs and notches for interlocking perpendicular panels at the basket corners.

• Case 2: HI-STORM FW loaded with MPC 37 fuel basket, without corner welds, basket panels are made with straight edges so a flat contact interface is formed between any two perpendicular panels meeting at the basket corner.

As shown in the tipover analysis [3.4.11], the standard fuel basket does not experience significant plastic deformation in the active fuel region to exceed the acceptable limits. The maximum panel displacement due to the tip-over event is located beyond the active fuel region for both MPC-37 and MPC-89 baskets (tipover of MPC-89 is not analyzed here but the results are bounded by MPC-37),

which is considered to be acceptable from the perspectives of shielding and criticality. Note that the basket corner welds are not considered in the tip-over analysis for conservatism. The maximum permanent deflections of the heaviest loaded fuel basket panel for both analyzed cases are reported in Table 3.4.21. In addition, the maximum primary membrane plus bending stress in the fuel basket panels, within the active fuel region, does not exceed 90% of the true ultimate strength of Metamic-HT material. The fuel baskets in both Case 1 and Case 2 corner configuration are considered to be structurally safe as they can continue to maintain appropriate spacing between fuel assemblies after the tipover event. The MPC enclosure vessel experiences minor plastic deformation at the impact locations with the overpack guide tubes; the maximum local plastic strain (9.0%, see Figures 3.4.16D & 3.4.16E) is well below the failure strain of the material and smaller than the plastic strain limit (i.e., at least 0.2 for stainless steel) recommended by [3.4.6] for ASME NB components.

Similarly, local plastic deformation occurs in the overpack shear ring near the cask-to-pad impact location as shown in Figure 3.4.17D and 3.4.17E. However, the shielding capacity of overpack will not be compromised by the tipover accident and there is no gross plastic deformation in the overpack inner shell to affect the retrievability of the MPC. In addition, the cask closure lid bolts are demonstrated to be structurally safe after the tipover event, only a small plastic strain is observed in the bolt near the impact location (see Figures 3.4.18D & 3.4.18E). Therefore, the cask lid will not dislodge after the tipover event. Finally, the peak rigid body decelerations, measured for the HI-STORM FW lid concrete, are shown to be 60.91 gs for Case 1 and 62.82 gs for Case 2 in the vertical direction (see Figures 3.4.19D & 3.4.19E) and 17.80 gs for Case 1 and 17.75 gs for Case 2 in the horizontal direction (see Figures 3.4.20D & 3.4.20E). Note that the deceleration time histories are filtered using the LS-DYNA built-in Butterworth filter with a cut-off frequency of 350 Hz; the same filter was used for the HI-STORM 100 non-mechanistic tipover analysis.

The non-mechanistic tipover analysis for HI-STORM FW Version E cask is performed in [3.4.30]

using the same method used for HI-STORM FW cask in [3.4.11] and it is demonstrated in [3.4.30]

that all of the acceptance criteria, discussed above, are satisfied. The maximum permanent lateral deflection of the most heavily loaded basket panel, at any elevation within the active fuel region, is obtained from the LS-DYNA solutions and reported in Table 3.4.20 for the various fuel basket types.

The structural analyses of the HI-STORM FW lids [3.4.13] are performed using bounding peak rigid body deceleration forces; therefore, the results are applicable to the non-mechanistic tipover event with target foundation concrete strength specified in Table 2.2.9. It is concluded that the lids will not HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10J9 3-107 8 of 17

Holtec Letter 5018111 Attachment 3

i. The permanent lateral deflection of the most heavily loaded basket panel in the active fuel region complies with the deflection criterion in Table 2.2.11.

i.ii. The maximum primary membrane plus bending stress in the fuel basket panels, within the active fuel region, does not exceed 90% of the true ultimate strength of Metamic-HT material.

ii.iii. [

PROPRIETARY INFORMATION WITHHELD PER 10CFR2.390

]

iii.iv. The plastic strains in the MPC enclosure vessel remain below the allowable material plastic strain limit.

iv.v. The cask closure lid does not dislodge after the tipover event, i.e., the closure lid bolts remain in-tact.

v.vi. The structural analyses of cask closure lids are performed in [3.4.13] using bounding peak deceleration values; therefore, the lids do not suffer any gross loss of shielding.

3.4.4.1.4c Load Case 4: Non-Mechanistic Tipover of MPC-44 Basket Design The tipover analysis for MPC-44 is postulated only in the HI-STORM FW Version E overpack. The same modelling approach described in subparagraph 3.4.4.1.4a is used to construct the tipover model in LS-DYNA, except that the standard HI-STORM FW overpack is replaced by the Version E overpack, and the MPC-44 replaces the MPC-37. The fully assembled tipover model for the MPC-44 inside the HI-STORM FW Version E overpack is shown in Figure 3.4.9D. The tipover analysis is performed for the MPC-44 basket design using the existing design basis tipover model in LS-DYNA where the MPC-37 standard basket and aluminum shims are replaced with a fully articulated MPC-44 basket. The finite element model of the MPC-44 CBS basket is shown in Figure 3.4.12E. The continuous basket shims are modelled using the same approach employed for the MPC-89 CBS, which is described in subparagraph 3.4.4.1.4b. Lastly, the finite element model of the ISFSI is the same as described above in subparagraph 3.4.4.1.4a. For the ISFSI pad, the bounding target foundation properties per Table 2.2.9 are utilized.

Like other basket designs, the response of the MPC-44 CBS basket during the tipover event is predominantly elastic with very localized areas of plasticity, as shown in Figure 3.4.15E.

Nonetheless, to insure compliance with the allowable limit in Subsection 2.2.8, the maximum lateral deformation of the most heavily loaded CBS basket panel, at any elevation within the active fuel region, is obtained from the LS-DYNA solution and reported in Table 3.4.19.

The complete details of the finite element model, input data and results are archived in the calculation package [3.4.30]. In summary, the results of the tipover analysis The following conclusions demonstrate that all safety criteria are satisfied for the cask system with MPC-44 basket design, which means:

i. The permanent lateral deflection of the most heavily loaded basket panel in the active fuel region complies with the deflection criterion in Table 2.2.11.

ii. The maximum primary membrane plus bending stress in the fuel basket panels, HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10J9 3-109 9 of 17

Holtec Letter 5018111 Attachment 3 within the active fuel region, does not exceed 90% of the true ultimate strength of Metamic-HT material.

iii. The CBS remain attached to the basket maintaining their physical integrity. The stresses in the basket shims are mainly below the yield strength with only limited permanent deformation, as shown in Figure 3.4.46B.

iv. The plastic strains in the MPC enclosure vessel remain below the allowable material plastic strain limit.

v. The cask closure lid does not dislodge after the tipover event, i.e., the closure lid bolts remain in-tact.

vi. The structural analyses of cask closure lids are performed in [3.4.13] using bounding peak deceleration values; therefore, the lids do not suffer any gross loss of shielding.

3.4.4.1.4d Load Case 4: Non-Mechanistic Tipover of MPC-37P Basket Design A non-mechanistic tipover of HI-STORM FW Version E cask with MPC-37P basket inside is not explicitly analyzed because it is bounded by the tipover analysis of MPC-37 CBS basket. The reasons areThe tipover analysis of the following reasons:

a. MPC-37P basket panels are thicker than that of MPC-37 CBS basket per licensing drawings in Section 1.5.

b. MPC-37P basket cell width is smaller than that of MPC-37 CBS basket per licensing drawings in Section 1.5.

c. Weight of MPC-37P fuel assemblies is conservatively bounded by MPC-37 fuel assemblies per Table 2.1.1.

d. Temperature distribution of MPC-37P basket panels is bounded by MPC-37 CBS basket panels per thermal analyses supporting Chapter 4.

The details of the comparative evaluation, as well as the calculated results for the MPC-37 CBS tipover analysis, are documented in [3.4.30]. The maximum permanent deflection of the heaviest loaded fuel basket panel for the MPC-37/37P CBS basket is reported in Table 3.4.19. In addition, the maximum primary membrane plus bending stress in the fuel basket panels, within the active fuel region, does not exceed 90% of the true ultimate strength of Metamic-HT material. The stress distribution in the basket shims is plotted in Figure 3.4.46C, which shows that the stresses in the CBS are mainly below the material yield strength with only limited permanent deformation. Therefore, as the results demonstrate, the acceptance criteria defined in Paragraph 2.2.3(b) are satisfied for HI-STORM FW Version E cask with MPC-37P basket.

3.4.4.1.5 Load Case 5: Design, Short-Term Normal and Off-Normal MPC Internal Pressure The MPC Enclosure Vessel, which is designed to meet the stress intensity limits of ASME Subsection NB [3.4.4], is analyzed for a bounding normal (design, long-term and short-term) internal pressure (Table 2.2.1) of 120 psig using the ANSYS finite element code [3.4.1]. Except for the applied loads and the boundary conditions, the finite element model of the MPC Enclosure Vessel used for this load case is identical to the model described in Subsections 3.1.3.2 and 3.4.3.2 for the HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10J9 3-110 10 of 17

Holtec Letter 5018111 Attachment 3 Table 3.4.19 PERMANENT LATERAL DEFLECTION OF FUEL BASKET PANELS DUE TO NON-MECHANISTIC TIPOVER OF STANDARD HI-STORM FW OVERPACK Fuel Basket Type Max. Calculated Allowable Limit (in) Safety Factor Deflection (in)

MPC-37 0.0115 0.045 3.91 MPC-89 0.0141 0.030 2.13 MPC-32ML 0.0252 0.0479 1.90 MPC-89 CBS 0.021 0.030 1.43

The following steps are taken to calculate the maximum permanent deflection of fuel basket panel from the results of the non-mechanistic tipover simulation for each basket type:

1) The effective stress and the plastic strain contours for the fuel basket are plotted in LS-DYNA at the time instant of maximum loading. The maximum load demand essentially corresponds to the time instant when the top end of the MPC and stored fuel assemblies bottom out inside the HI-STORM cavity after primary impact and begin to rebound in the upward direction.

2) The contour plots are visually examined to identify the specific panel locations and fuel basket elevations where the stresses/strains are maximum. Both horizontally and vertically oriented panels are considered.

3) At each of the identified locations, a row of elements spanning the width of the cell is selected.

4) For the selected row of elements, the total lateral displacement (elastic + plastic) at the middle of the span and at both ends of the span are obtained from the LS-DYNA solution. The relative deflection between the midspan of the panel and its two support ends is taken as the largest difference between the three absolute displacement measurements.

5) To separate the permanent deflection from the combined deflection, step (4) is repeated for the same row of elements for an earlier solution time step when the maximum stress in the limiting element (among the row of selected elements) is just below the yield strength of the material.

6) The maximum permanent deflection, for each panel location identified in step (3), is conservatively computed by subtracting the elastic deflection determined in step (5) from the total deflection (elastic +

plastic) determined in step (4).

Equal to 0.005 times the cell inner dimension per Subsection 2.2.8 and Table 2.2.11. Cell inner dimension obtained from drawing package in Section 1.5.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10J9 3-148 11 of 17

Holtec Letter 5018111 Attachment 3 Table 3.4.20 PERMANENT LATERAL DEFLECTION OF FUEL BASKET PANELS DUE TO NON-MECHANISTIC TIPOVER OF HI-STORM FW VERSION E OVERPACK Fuel Basket Type Max. Calculated Allowable Limit (in) Safety Factor Deflection (in)

MPC-37 0.017 0.045 2.65 MPC-89 0.011 0.030 2.73 MPC-32ML 0.0287 0.0479 1.67 MPC-89 CBS 0.025 0.030 1.20 MPC-44 CBS 0.011 0.0405 3.68 MPC-37/37P CBS 0.036 0.045 1.25

Maximum permanent deflection is calculated following the steps outlined in Table 3.4.19.

Equal to 0.005 times the cell inner dimension per Subsection 2.2.8 and Table 2.2.11. Cell inner dimension obtained from drawing package in Section 1.5.

Tipover analysis performed based on MPC-37 CBS basket geometry. Results are also bounding for MPC-37P CBS basket per discussion in subparagraph 3.4.4.1.4d.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10J9 3-149 12 of 17

Holtec Letter 5018111 Attachment 3 Table 3.4.21 PERMANENT LATERAL DEFLECTION OF FUEL BASKET PANELS DUE TO NON-MECHANISTIC TIPOVER USING BOUNDING CONCRETE COMPRESSIVE STRENGTH Case No. Max. Calculated Allowable Limit Safety Factor Deflection (in) (in)

Case 1 0.0041 0.045 10.98 Case 2 0.0022 0.045 20.45

See 3.4.4.1.4a for description of cases analyzed.

Maximum permanent deflection is calculated following the steps outlined in Table 3.4.19.

Equal to 0.005 times the cell inner dimension per Subsection 2.2.8 and Table 2.2.11. Cell inner dimension obtained from drawing package in Section 1.5.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10J9 3-150 13 of 17

Holtec Letter 5018111 Attachment 3 Table 4.4.6

SUMMARY

OF HI-STORM FW DIFFERENTIAL THERMAL EXPANSIONS Gap Description Cold Gap U (in) Differential Is Free Expansion Expansion i (in) Criterion Satisfied (i.e., U > i)

Fuel Basket-to-MPC 0.0625 0.082 No*

Radial Gap Fuel Basket-to-MPC 1.5 0.421 Yes Minimum Axial Gap MPC-to-Overpack 2.625 0.161 Yes Radial Gap MPC-to-Overpack 3.5 0.381 Yes Minimum Axial Gap

• While the free expansion criterion is not satisfied, the radial interference (i.e., - U) is less than the allowable limit specified in Table 3.1.15 and therefore acceptableresultant impact to the design is insignificant. See Subsection 3.1.14.4.6 for additional discussiondetails.

Table 4.4.7 THEORETICAL LIMITS* OF MPC HELIUM BACKFILL PRESSURE**

MPC Minimum Backfill Pressure Maximum Backfill Pressure (psig) (psig)

MPC-37 41.0 47.3 Pattern A MPC-37 40.8 47.1 Pattern B MPC-37 Figures 1.2.3a 43.9 50.6 Figures 1.2.4a 43.6 50.3 Figure 1.2.5a 44.1 50.8 MPC-89 Table 1.2.4a 41.9 48.4 Figure 1.2.6a 41.7 48.2 HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10B9 4-53 14 of 17

Holtec Letter 5018111 Attachment 3 The same ISFSI concrete pad material model used for the standard HI-STORM FW tipover analysis in Subparagraph 3.4.4.1.4 is adopted for the HI-STORM FW Version UVH tipover analysis. Specifically, the concrete pad behavior is characterized using the same LS-DYNA material model (i.e., MAT_PSEUDO_TENSOR or MAT_016) as for the tipover analysis of the standard HI-STORM FW cask in Subparagraph 3.4.4.1.4. Similarly, the subgrade is also conservatively modeled as an elastic material. Note that this ISFSI pad material modeling approach was originally taken in the USNRC approved storage cask tipover and end drop LS-DYNA analyses [3.4.5] where a good correlation was obtained between the analysis results and the test results.

To assess the potential damage of the cask caused by the tipover accident, an LS-DYNA nonlinear material model with strain rate effect is used to model the responses of all HI-STORM FW Version UVH cask structural members based on the true stress-strain curves of corresponding materials.

Note that the strain rate effect for the fuel basket material, i.e., Metamic-HT, is not considered for conservatism.

Figure 3.I.3.3 depicts the finite element tipover analysis model developed for the HI-STORM FW Version UVH cask configurations with loaded MPC-37. Identical models are prepared for the HI-STORM FW Version UVH cask loaded with MPC-89 and MPC-44. Table 3.I.3.9 summarizes the maximum plastic strain results for each MPC fuel basket, along with the corresponding material failure strains. The plastic strain contours are plotted in Figures 3.I.3.4 through 3.I.3.6 for all three fuel baskets. It is observed from these three figures that the strains within the active fuel region are mainly elastic, and the peak strains are below the material failure strain limit. Plastic deformation occurs only in localized areas of the peripheral cells of all three baskets (MPC-37, MPC-89 and MPC-44) near the top of the basket or in the bottom mouse hole region beyond the active fuel region. The MPC-44 is the limiting basket design from a tipover perspective based on the strain contours plotted in Figures 3.I.3.4 through 3.I.3.6. This is because the visible plastic strain regions are more widespread, and the strain values are also higher for the MPC-44. Nonetheless, all three basket types are further evaluated to determine the maximum permanent deformation of the heaviest loaded basket panel for direct comparison with the allowable limit in Table 2.2.11. The deflection results are summarized in Table 3.I.3.12.

The MPC enclosure vessel also experiences minor plastic deformation at the impact location with overpack inner shell. The maximum local plastic strain is well below the failure strain of the material and also smaller than the conservatively established plastic strain design limit (i.e., at least 0.2 for stainless steel) recommended by [3.4.6] for ASME NB components. Local plastic deformation occurs in the overpack inner shell due to the interaction with the MPC closure lid.

Similar local plastic deformation occurs in the top region of the overpack outer shell and in the overpack lid outer shell at the impact location with the ISFSI pad. The strains in the overpack (including the lid) remain below the material failure strain limit. Furthermore, the shielding capacity of overpack (including the lid) is not compromised by the tipover accident and there is no gross plastic deformation in the overpack inner shell to affect the retrievability of the MPC. In addition, the cask closure lid bolts are demonstrated to be structurally safe after the tipover event, only a negligibly small plastic strain is observed in the bolt.Figure 3.I.3.3 depicts the finite-element tipover analysis model developed for the HI-STORM FW Version UVH cask configurations with HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10IC 3.I-9 15 of 17

Holtec Letter 5018111 Attachment 3 loaded MPC-37. Identical models are prepared for the HI-STORM FW Version UVH cask loaded with MPC-89 and MPC-44. Table 3.I.3.9 summarizes the maximum plastic strain results, along with the corresponding material failure strains.

From Figures 3.I.3.4 to 3.I.3.6 and Table 3.I.3.9, it is observed that the strains within the active fuel region are below the material failure strain limit. Local plastic deformation essentially develops only in a couple of peripheral cells of all three baskets (MPC-37, MPC-89 and MPC-44) near the top of the basket or in the bottom mouse hole region beyond the active fuel region. All three fuel baskets are structurally safe since they can continue maintaining appropriate spacing between fuel assemblies after the tipover event. The MPC enclosure vessel also experiences minor plastic deformation at the impact location with overpack inner shell; the maximum local plastic strain is well below the failure strain of the material and also smaller than the conservatively established plastic strain design limit (i.e., at least 0.2 for stainless steel) recommended by [3.4.6]

for ASME NB components. Local plastic deformation occurs in the overpack inner shell due to the interaction with the MPC closure lid. Similar local plastic deformation occurs in the top region of the overpack outer shell and in the overpack lid outer shell at the impact location with the ISFSI pad. The strains in the overpack (including the lid) remain below the material failure strain limit.

Furthermore, the shielding capacity of overpack (including the lid) is not compromised by the tipover accident and there is no gross plastic deformation in the overpack inner shell to affect the retrievability of the MPC. In addition, the cask closure lid bolts are demonstrated to be structurally safe after the tipover event, only a negligibly small plastic strain is observed in the bolt.

The complete details of the finite element model, input data and results are archived in the calculation package [3.4.31]. In summary, the results of the tipover analyses The following conclusions demonstrate that all safety criteria are satisfied for the Version UVH cask with MPC-37, MPC-44 and MPC-89 basket designs, which means:.

i. The lateral deflection of the most heavily loaded basket panel in the active fuel region complies with the deflection criterion in Table 2.2.11.

i.ii. The maximum primary membrane plus bending stress in the fuel basket panels, within the active fuel region, does not exceed 90% of the true ultimate strength of Metamic-HT material.

ii.iii. The CBSshims in MPC-44 basket remain attached to the MPC-44 fuel basket it maintaining theirits physical integrity. The stresses in the basket shims are mainly below the yield strength with only limited permanent deformation, as shown in Figure 3.I.3.13.

iii.iv. The plastic strains in the MPC enclosure vessel remain below the allowable material plastic strain limit.

iv.v. The cask closure lid does not dislodge after the tipover event, i.e., the closure lid bolts remain in-tact.

v.vi. The lid or the cask body do not suffer any gross loss of shielding.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10IC 3.I-10 16 of 17

Holtec Letter 5018111 Attachment 3 Table 3.I.3.10: STRESS RESULTS FOR HI-STORM FW VERSION UVH LID -

NORMAL HANDLING Calculated Value Allowable Limit Item Safety Factor (ksi) (ksi)

Maximum Primary Membrane 6.6 (conservative) 19.6 2.97 Stress Maximum Primary Membrane 6.6 29.4 4.45 Plus Bending Stress Lift Lug-to-Base Plate Weld 0.474 7 14.76 Lift Lug - Tear Out 2.177 4.20 1.93 Table 3.I.3.11: GOVERNING STRESS RESULTS FOR HI-STORM FW VERSION UVH

- NORMAL HANDLING AND PRESSURE LOADING Calculated Value Allowable Limit Item Safety Factor (ksi)* (ksi)

Maximum Primary Membrane 17.17 34.9 2.03 Stress (Overpack)

Maximum Primary Membrane 30.89 52.4 1.70 Plus Bending Stress (Overpack)

Maximum Primary Membrane 9.56 34.9 3.65 Stress (Lid)

Maximum Primary Membrane 17.16 52.4 3.05 Plus Bending Stress (Lid)

• All the tabulated stresses correspond to the governing load case i.e., pressure case 5 in Subsection 3.I.3.2 Table 3.I.3.12: PERMANENT LATERAL DEFLECTION OF FUEL BASKET PANELS DUE TO NON-MECHANISITC TIPOVER Fuel Basket Type Max. Calculated Allowable Limit (in) Safety Factor Deflection (in)

MPC-37 0.0216 0.045 2.08 MPC-89 0.0133 0.030 2.26 MPC-44 CBS 0.0233 0.0405 1.74

Equal to 0.005 times the cell inner dimension per Subsection 2.2.8 and Table 2.2.11. Cell inner dimension obtained from licensing drawing in Section 1.5.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Proposed Rev. 10IC 3.I-14 17 of 17