ML20293A289

NAC International 10 CFR Part 72 Inspection Pre-Decisional Enforcement Conference Presentation Slides

ML20293A289
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Issue date:	10/20/2020
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NRC & NAC 10 CFR Part 72 Inspection PreDecisional Enforcement Conference October 20, 2020 Kent Cole President & CEO, NAC International George Carver VicePresident Engineering & Support Services Wren Fowler Director of Licensing Marc Griswold Senior Project Engineer Ryan Bailey Senior Project Manager The Skills and Experience to Deliver Nuclear Excellence

PURPOSE Demonstrate NAC used the existing FSAR design control measures for incorporating CC5 into the MAGNASTOR FSAR, relative to the tipover evaluation.

Demonstrate that the method of evaluation (MOE) used by NAC to incorporate CC5 into the FSAR was not a departure per the regulations, relative to the tipover evaluation.

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OUTLINE - PART 1 Part 1 of the presentation will be conducted as follows:

Apparent Violations (AVs)

NonMechanistic TipOver Event FSAR NonMechanistic TipOver Licensing Basis FSAR Design Control Measures 10 CFR 72.48 Design Control Process 10 CFR 72.48 Determination for CC5 Summary 3

OUTLINE - PART 2 Part 2 of the presentation will be conducted as follows:

MAGNASTOR Amendment 9 NAC Comments on the NRC Inspection Report Palo Verde NRC Inspection vs. NAC NRC Inspection NAC Corrective Actions Following the Palo Verde Inspection NAC Actions Following AVs Presentation Conclusion 4

APPARENT VIOLATIONS 10 CFR 72.146(c) - Design control NRCs Position (

Reference:

AV A, Enclosure 1, NRC Choice Letter)

NAC implemented a design change for the MAGNASTOR spent fuel cask without ensuring that design control measures were commensurate with those applied to the original design.

Specifically, NAC failed to use the nonlinear LSDYNA computer model (identified in the MAGNASTOR FSAR Sections 3.7.3.7 and 3.10.4.4 as the method of evaluation for concrete cask tipover analysis applied to the original design) for the assessment of acceleration values for a design basis tipover accident of the MAGNASTOR CC5 spent fuel cask.

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APPARENT VIOLATIONS (CONTD) 10 CFR 72.48(c)(2)(viii) - Changes, tests, and experiments departure from a method of evaluation NRCs Position (

Reference:

AV B, Enclosure 1, NRC Choice Letter)

NAC failed to obtain a CoC amendment from the NRC pursuant to 10 CFR 72.244 prior to implementing a design change for the MAGNASTOR CC5 spent fuel cask that resulted in a departure from a method of evaluation described in the MAGNASTOR FSAR.

Specifically, NAC failed to utilize LSDYNA, a nonlinear analysis methodology that was described in the MAGASTOR FSAR Section 3.7.3.7, when implementing a design change for the MAGNASTOR CC5 spent fuel storage cask.

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NONMECHANISTIC TIPOVER EVENT The following is a detailed discussion about the nonmechanistic tipover event and subsequent evaluations:

The tipover event is a hypothetical accident condition in which the concrete cask tipsover onto an ISFSI pad.

In the absence of a credible hazard that induces tipover, it is evaluated as a nonmechanistic event (i.e., an event with no identifiable cause).

During a nonmechanistic tipover, the cask is postulated to rotate from a position with its center of gravity (CG) over its lowest corner to a horizontal orientation, which results in an impact with the ISFSI pad.

When the cask impacts the pad, kinetic energy is transferred to the pad and the cask experiences a rapid deceleration (measured in gloads).

The casks confinement boundary (canister) and internal basket structure are evaluated for the inertial loads experienced during this deceleration to confirm stress levels are below limits.

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NonMechanistic TipOver Event (Contd)

Position A Position B Position C Position D Vertical Orientation CG Over Corner Horizontal Orientation Horizontal Orientation Normal Storage Condition Zero Velocity Prior to Impact Impact/Deceleration R

CG H h R

Cask at rest Cask CG at its highest point Cask is completely tipped over, just prior to Cask has impacted the ISFSI Pad (maximum potential energy) contact with the pad. The value h and is decelerating. Cask corresponds to a change in potential energy (PE) decelerations are governed by which is assumed to be completely transformed the structural characteristics of CG - center of gravity R - cask radius into rotational kinetic energy (KE). Using the the cask, ISFSI pad, and LCG - CG height from cask bottom H - cask height law of conservation of energy, this relationship underlying soil.

dCG - CG height at Position B is expressed as:

h - change in CG height mgh = (EQ 1) m - cask mass g - acceleration of gravity I - mass moment of inertia - angular velocity 8

FSAR NonMechanistic TipOver Licensing Basis The FSAR (Section 3.7.3.7) uses a computer code known as LSDYNA in the original licensing of MAGNASTOR to calculate the cask content gloads (i.e., decelerations at the top of the canister lid and top of the fuel basket).

The tipover is simulated in LSDYNA by applying an initial angular velocity to the entire cask as described in the FSAR (Section 3.10.4.4).

Note that the simulation starts with the cask on its side on the generic ISFSI pad.

The method of evaluation (MOE) used in the FSAR (Section 3.10.4.4) for determining the angular velocity input for LSDYNA (and checking the LSDYNA output kinetic energy) is the following classical mechanics equation which relates the casks potential energy at CG over corner to the kinetic energy (angular velocity) at impact on the storage pad.

Where m is the mass of the system; g is the acceleration due to gravity; h is the CG height change; I is the casks moment of inertia; and is the resulting angular velocity at impact.

The potential energy needs to match the kinetic energy and vice versa to ensure the LSDYNA results for gload accelerations are accurate.

The key variable is the angular velocity, which is the energy being imparted to the cask during impact.

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FSAR NonMechanistic TipOver Licensing Basis (Contd)

The gloads from LSDYNA are used to justify the acceptance of the values used in the subsequent structural evaluations in the FSAR, which are performed using ANSYS.

LSDYNA is not the licensing basis program used to structurally evaluate the cask system. It is a simplistic model used to validate that the gloads (used in ANSYS) bound the loads seen during the event.

The ANSYS evaluations can be found in FSAR Sections 3.7.1, 3.7.2, and 12.2.12.4.

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FSAR NonMechanistic TipOver Licensing Basis (Contd)

Verification Basket & TSC Design Attributes Conservation of Energy accelerations ANSYS Detailed Canister Analysis with dynamic amplification Stress are bounded <

by those used ASME IIINB in the static structural 40g analysis for tipover Initial KE

> PE CC1/CC2 ANSYS Detailed Basket Analysis LSDYNA Bounding TipOver Analysis Acceleration Time History Stress TSC <

29.6g 35g ASME IIING, Basket App. F 26.6g 11

FSAR NonMechanistic TipOver Licensing Basis (Contd)

The cask is simplistically modeled as two concentric right circular cylinders An inner steel liner surrounded by concrete.

Discrete volumes of the cask model are assigned appropriate densities to represent the mass and relative distribution (i.e., CG) of all cask components.

Fine design details such as the rebar, vents, pedestal, lid, canister, etc. are not explicitly modeled.

The liner is modeled as a rigid body.

The loaded canister is represented by including its mass in a strip of elements at the ID of the cask.

Cask is in the horizontal orientation above the pad and soil.

An initial angular velocity is applied to the entire CC1/CC2 LSDYNA Cask & Pad Model cask about the point of rotation.

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FSAR DESIGN CONTROL MEASURES For the tipover evaluation, the following are the design control measures:

Simplistic LSDYNA model of a cask and a generic pad & soil.

Application of an initial angular velocity on the cask.

An evaluation that ensures the conservation of energy is preserved in LSDYNA.

Verification that the resulting LSDYNA gloads are bounded by the gloads used in the subsequent ANSYS structural evaluations.

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10 CFR 72.48 CHANGE CONTROL PROCESS 10 CFR 72.48 allows the cask designer to make changes to their licensing basis design, provided certain conditions are met.

Per the regulation (72.48(c)(2)(viii)) a certificate holder shall obtain a CoC amendment for a proposed change that would (viii) Result in a departure from a method of evaluation described in the FSAR (as updated) used in establishing the design bases or in the safety analyses.

A departure from an MOE is defined in 72.48(a)(2), and a cask designer can change any of the elements of an MOE (72.48 (a)(2)(i)) or change to another MOE (72.48(a)(2)(ii)) provided certain conditions are met.

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10 CFR 72.48 CHANGE CONTROL PROCESS (CONTD)

The most recently published (September 22, 2020) NRC guidance is Regulatory Guide 3.72, Revision 1, Guidance for Implementation of 10 CFR 72.48,Changes, Tests, And Experiments. Page 3 of RG 3.72 Rev. 1 states that:

The statement of considerations (SOC) for the final rule states that a departure from an MOE as described in the FSAR (as updated) used in establishing the design bases or in the safety analyses means (1) changing any of the elements of the method described in the FSAR (as updated) unless the results of the analysis are conservative or essentially the same or (2) changing from a method described in the FSAR to another method unless that method has been approved by the NRC for the intended application.

Regulatory Guide 3.72, Rev. 1 formally endorses NEI 1204, Rev. 2.

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10 CFR 72.48 DETERMINATION FOR CC5 To incorporate CC5 into the FSAR, NAC evaluated the new cask via the 72.48 process to determine if prior NRC approval was needed.

NAC confirmed that:

The FSAR contains a licensing basis MOE (a simplistic LSDYNA cask model) used to justify ANSYS gloads.

The FSAR also contains a licensing basis MOE for determining the angular velocity input for LSDYNA (and checking the LSDYNA output kinetic energy).

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10 CFR 72.48 DETERMINATION FOR CC5 (CONTD)

NAC used the licensing basis MOE for determining the angular velocity input for LSDYNA.

As previously discussed, this can be found in the FSAR (Section 3.10.4.4) and is shown below:

Where m is the mass of the system; g is the acceleration due to gravity; h is the CG height change; I is the casks moment of inertia; and is the resulting angular velocity at impact.

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10 CFR 72.48 DETERMINATION FOR CC5 (CONTD)

By taking the licensing basis MOE equation for determining the angular velocity input for LSDYNA (and checking the LSDYNA output kinetic energy), the terms can be rearranged to solve for the angular velocity.

The angular velocity for CC5 can then be compared to CC1 by solving for their ratio to determine the extent that they are different.

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10 CFR 72.48 DETERMINATION FOR CC5 (CONTD)

Thus, the relative difference in angular velocity between CC5 and CC1 was determined.

The difference in angular velocity between CC5 and CC1 is less than 1%.

In this case, the licensing basis LSDYNA model angular velocity input was verified to be applicable to CC5.

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10 CFR 72.48 DETERMINATION FOR CC5 (CONTD)

Before building any new LSDYNA model, NAC determined whether the previous model was relevant to CC5.

Since the generic FSAR pad and soil remained unchanged and the casks are similar in design and materials, the licensing basis LSDYNA model for CC1 is applicable to CC5 after confirming that the angular velocities are essentially the same.

A substantial difference in angular velocity would preclude the ability to use the previous LSDYNA results for CC5. In that case, a CC5 specific LSDYNA model would need to be built and run to ensure the subsequent ANSYS structural evaluations were bounding.

This is the licensing basis design control process.

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10 CFR 72.48 DETERMINATION FOR CC5 (CONTD)

The FSAR licensing basis MOE for determining the angular velocity input for LS DYNA contains both input parameters and elements.

Industry guidance on these key terms is provided in NEI 1204, which is endorsed by Reg. Guide 3.72, Rev. 1 as follows:

The input parameters are the physical dimensions of the system and constants of nature (i.e., the mass, gravity, and center of gravity for the system).

The elements are the moment of inertia and the angular velocity.

In order to verify the licensing basis LSDYNA model was applicable to CC5, NAC followed the licensing basis design control process and determined the relative difference in angular velocity between CC5 and CC1.

For the moment of inertia, NAC elected to derive the moment of inertia via a hand calculation instead of using LSDYNA, which is the method described in the FSAR.

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10 CFR 72.48 DETERMINATION FOR CC5 (CONTD)

NAC recognizes that calculating the moment of inertia by hand rather than using LSDYNA is a new method.

However, NAC can do this provided it is not a departure.

The regulation allows NAC to change to another method provided the method has been previously approved by the NRC for the intended application.

NAC previously received NRC acceptance to use hand calculations for deriving the moment of inertia for a cask in the tipover evaluation.

The NACMPC (721025 FSAR Section 11.2.12.2.1) and NACUMS (721015 - FSAR Section 11.2.12.3.1) systems are licensed by the NRC this way.

This is consistent with the regulation and the NRCs guidance (Reg. Guide 3.72, Rev. 1), which endorsed NEI 1204, Rev. 2.

Therefore, a departure has not occurred, and NAC is allowed to use hand calculations in lieu of LSDYNA.

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SUMMARY

NAC used the licensing basis design control measures in the FSAR.

NAC used the licensing basis methods of evaluation in the FSAR except for the moment of inertia for CC5.

NAC did change the way the moment of inertia was derived but it did not constitute a departure because the method had been previously approved by the NRC for the intended application.

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OUTLINE - PART 2 Part 2 of the presentation will be conducted as follows:

MAGNASTOR Amendment 9 NAC Comments on the NRC Inspection Report Palo Verde NRC Inspection vs. NAC NRC Inspection NAC Corrective Actions Following the Palo Verde Inspection NAC Actions Following AVs Presentation Conclusion 24

MAGNASTOR AMENDMENT 9 Contrary to the IR, the NRC staff has substantiated and approved the adequacy of the 72.48 tipover approach taken.

The NRC IR states that NACs 72.48 approach would likely not be approved by the technical staff (see Choice Letter Enclosure 2 Page #15, 3rd paragraph).

However, the NRC through the MAGNASTOR Amd. 9 Safety Evaluation Report (SER) concludes the approach is acceptable to the NRC (see SER Pages 7 and 8)

Amd. 9 included an alternative cask known as CC6.

NAC could have incorporated it via the 72.48 process, but elected to include all cask design changes in a comprehensive amendment for a specific project.

This cask was evaluated by NAC for tipover in the same manner as CC5.

The Amd. 9 SER has already been approved by the NRC Staff.

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MAGNASTOR AMENDMENT 9 (CONTD)

The following is from the SER (Page 8, last paragraph; emphasis added)

However, despite having not performed a more indepth tipover analysis, the staff has concluded that no additional nonmechanistic tipover analysis of the CC6 is needed, in this instance, because there is reasonable assurance that the CC6 will perform its intended safety functions under a nonmechanistic tipover event. This is due to conservatism and similarity of the CC6 to other applicants concrete casks as shown in Table 3.3 of this SER below. Specifically:

(i) CC1 was designed with an additional 50% margin with the gloads calculated by LSDYNA tip over analysis (i.e., designbasis of 35.0g and 40.0g at the top of the fuel basket and cask, respectively, compared to calculated gloads); (ii) both the CC1 and CC6 are evaluated on the same pad; (iii) the CC1 and CC6 are of similar construction; (iv) the CC6 is shorter and has a slightly shorter center of gravity as compared to the CC1, therefore it is more stable; and (v) the initial angular velocity of CC6 is within 2% of the CC1.

Table 3.3 - g-load at Top of the Fuel Basket and Cask Fuel Basket Cask Cask Type Method (Design Basis = 35g) Design Basis = 40g CC1 LS-DYNA 26.4g 29.5g 26

MAGNASTOR AMENDMENT 9 (CONTD)

There are several important takeaways from this SER:

A LSDYNA model for CC6 was not built and run.

The NAC cask tipover approach for CC3, CC4, CC5 and CC6 are the same.

The NRC SER concludes CC6 is similar to the applicants other concrete cask, CC1.

The NRC SER paragraph on the previous slide presents the basis of the NRCs acceptance of CC6; the following presents how CC5 compares to the same NRCs criteria:

i. Significant design margin exists in the licensing basis (CC1).

ii. Same ISFSI pad and soil.

iii. Similar construction and materials.

iv. CC5 is not shorter than CC1 (like CC6) but is essentially the same (<0.3%)

v. The angular velocity relative to CC1 is acceptable (<2% difference)

Note, CC5 is <1% different than CC1 NRC staff approved the approach NAC used for CC5 when it approved Amendment 9 demonstrating it as an acceptable technical basis without the need to reperform LSDYNA 27

NAC COMMENTS ON THE NRC INSPECTION REPORT The NRC staff represents in the IR that LSDYNA is the MOE for tipover evaluation.

However, the MOE for tipover also includes:

The predecessor calculation of potential energy and angular velocity prior to impact. These are inputs to the LSDYNA model that can be developed from classical formulas through application of the conservation of energy equation and basic cask physical parameters and are elements of the MOE in NACs licensing basis.

LSDYNA is used to perform dynamic analysis of structures, but it does not calculate initial potential energy, or angular velocities resulting from a tipover.

The NRC IR did not acknowledge significant conservatism in gload inputs into the subsequent ANSYS stress evaluations for determining whether the canister and basket stresses resulting from the tipover gloads are within applicable stress limits.

GLoads resulting from a tipover calculated by LSDYNA are NOT subject to specified regulatory limits or criteria.

NAC utilized bounding acceleration values of 35g (basket) and 40g (canister) in its downstream ANSYS structural evaluations.

NRC staff asserts that NAC changed its MOE for tipover from LSDYNA to linear scaling, but it is clear from NACs 72.48 evaluation and supporting calculations that NAC did not estimate any gloads for CC5.

Any MOE that replaces LSDYNA for dynamic analysis of tipover events would, like LSDYNA, need to produce gload outputs.

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NAC COMMENTS ON THE NRC INSPECTION REPORT (CONTD)

The NRC IRi has presented concerns over the nonlinear behavior of the tipover model parameters and inputs, specifically with respect to the storage pad and underlying soil.

NAC used identical pad & soil (these have not changed in the FSAR since CC1/CC2) properties in the 72.48 evaluation.

The NRC IR indicated a scaling method resulted in errant determination that each cask had a uniform density cylinder.

The use of an approximation of the casks moment of inertia using a hand calculation for a uniform density cylinder is appropriate for the evaluation of the casks relative angular velocity.

The NRC IR indicated many differences in cask designs.

There are no significant differences in CC1/CC2 and CC5 cask designs.

General geometry, materials and design of both casks are very similar. Weight is slightly higher, but the general effect on the tipover is a reduction of decelerations with a similar angular velocity.

i. The NRCs Choice Letter considers the pad and soil properties have changed with the incorporation of CC5 (see Choice Letter Enclosure 2 Page #15) 29

NAC COMMENTS ON THE NRC INSPECTION REPORT (CONTD)

Similarities of CC5 to CC1/2 There are substantial similarities that will control the casks behavior in a tipover event.*

All Materials of cask construction are the same.

Concrete Cask outside and inside diameter are the same.

Cask height is essentially the same - 0.6 0.3%.

Cask center of gravity is essentially the same - 2.1 <2%.

Shielding enhancements Loaded cask weight increased by ~17,500 lbs., this is less than 6% and is largely comprised of distributed masses with little impact on the CG of the system including:

Rebar spacing of the outer cage is slightly denser but distributed (~900 lbs. - 0.3%).

Cask liner is 1.25 thicker and, although a more significant contributor to the system weight increase (14,900lbs ~4%), is distributed.

Cask lid thickness (1,630lbs) and inlet vent steel bars (580 lbs.), are more local masses but contribute a very small percentage (0.7%) to the system weight.

• The NRC Choice Letter states many characteristics are different (see Choice Letter Enclosure 2 Page #12, 2nd Paragraph) 30

NAC COMMENTS ON THE NRC INSPECTION REPORT (CONTD)

Uniform Density Cylinder Approximation The mass moment of inertia calculation is only used in calculating the relative difference of the cask systems response to motion in the determination of relative angular velocities.

The approximation for mass moment of inertia for the uniform density representation results in a CC5 to CC1 ratio of 1.073.

To demonstrate the suitability of simplified uniform density representation, which the IR described as errant, NAC subsequently developed highly detailed 3D design models of the CC5 and CC1 casks to obtain inertial properties to a high level of accuracy. The 3D models result in a CC5 to CC1 ratio of 1.062.

The small difference in these two ratios demonstrates the Detailed 3D Model of CC1 Detailed 3D Model of CC5 suitability of the uniform density cylinder representation of a moment of inertia.

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PALO VERDE NRC INSPECTION VS. NAC NRC INSPECTION Palo Verde (PVGS) Transition from NAC UMS to MAGNASTOR First customer to utilize the CC5 Concrete Cask Design The NRC Inspection at Palo Verde was ongoing during the scheduled triennial NAC February 2020 inspection.

In September 2019, Region IV Inspectors had concerns related to the linear scaling of gloads for the sitespecific condition.

Prior to the loading of the first MAGNASTOR system at Palo Verde, NAC performed a sitespecific LSDYNA evaluation (300322010) which resolved the Inspection Teams questions .

Results were inline with our previous calculational results.

Why is the PVGS Inspection relevant to todays conference? Because the IR commingles facts between the NAC Inspection and the PVGS Inspection. For example:

IR states that NAC compared hand calculated acceleration results to the previous nonlinear LSDYNA acceleration results" i IR states that linear scaling or ratioing would likely not be approved by the technical staff because so many variables such as the concrete and soil material properties, pad and soil configurations (e.g., compressive strength) can change ii These PVGS 72.212 support activities were completely separate from, and long after NACs licensing efforts which incorporated CC5 into our FSAR.

i. NRC Choice Letter Enclosure 2 Page #13, 3rd Paragraph ii. NRC Choice Letter Enclosure 2 Page #15, 3rd Paragraph 32

PALO VERDE NRC INSPECTION VS. NAC NRC INSPECTION (CONTD)

Timeline of Significant Events NAC Inspection Related Events Palo Verde Inspection Related Events November 7 - PVGS / NAC Respond to NRCs questions by revising ED20190048 and providing written responses to the inspectors questions March 2 PVGS begins MAGNASTOR Cask Loading September 4 NAC September 12 - NRC Receives Choice December 26 - NAC Region IV Inspector Letter and AVs from contracts to provide submits questions to February 27 - NAC July 6 - PVGS NRC Palo Verde 11 PVGS regarding the completes PVGS Site receives Choice MAGNASTOR System sitespecific TipOver Specific LSDYNA Tip Letter and notice of

- 1st CC5 Order Evaluation Over (300322010) 2 AVs from NRC 2016 2017 2018 2019 2020 December 30 NAC February 27 - NRC July 22 - NRC holds incorporates CC5 May 14 - NAC issues Exit Meeting with Memorandum Triennial Inspection into MAGNASTOR of NAC Complete NAC. First time NAC FSAR via 72.48 ED20190048 to is informed of 2 AVs document the Palo (No Exit Meeting NAC Inspection NAC16MAG018 pending ongoing and forthcoming Verde Site Specific ISFSI remains open Choice Letter Pad TipOver (Supports Region IV PVGS 72.212 Evaluation) inspection at PVGS 33

PALO VERDE NRC INSPECTION VS. NAC NRC INSPECTION (CONTD)

CC5 Incorporation into FSAR via 72.48 (2016)

NAC initiates the 72.48 process to determine if incorporation of CC5 into the FSAR requires prior NRC approval.

NAC performed a screening and subsequent evaluation, per the regulation.

NAC determined that CC5 was acceptable without obtaining prior NRC approval.

NAC did not use linear scaling.

CC5 Acceptance on the Palo Verde ISFSI Pad via 72.212 (2019 - 2020) 10 CFR 72.212 requires Palo Verde to review the FSAR generic ISFSI pad and identify / justify differences.

Palo Verde provided these ISFSI pad differences to NAC via a specification.

NAC provided a report (ED20190048) which ratioed prior LSDYNA tipover evaluation results to estimate gloads that would be expected with CC5 on the Palo Verde ISFSI pad.

Palo Verde then performed a 72.48 determination, referencing the NAC report to justify the pad was acceptable for CC5 tipover.

NRC Region IV raised questions on the MOE used in the evaluation.

NAC promptly developed a sitespecific LSDYNA model and calculation (300322010) to support the PVGS MAGNASTOR CC5 tip over and resolve the Region IV concerns.

APS revised their 72.212 report prior to cask loading to include 300322010.

Through subsequent dialog with Palo Verde and Region IV, NAC understands the NRCs position. NAC acknowledges this ratioing (or linear scaling) approach when applied to multiple parameter differences with nonlinear behavior (i.e. those between the generic FSAR pad and the PVGS pad) was an overreliance on ratioing. The sitespecific LSDYNA model and calculation was the appropriate choice of analysis. 34

NAC CORRECTIVE ACTIONS FOLLOWING PALO VERDE INSPECTION Following the APS Inspection, NAC issued CAR 2001 with respect to NACs decision not to initially perform a sitespecific LSDYNA run.

CAR 2001 Corrective Actions:

Evaluation of the ability of the components to perform intended safety function (reportability).

Extent of condition review:

Design Control Methods Other Customers sitespecific tipover analyses Root Cause Analysis.

Review NAC calculation process and procedure for weakness related to the specific issue.

Review NAC project management planning procedure for weakness related to design deliverables.

Employee training - including emphasis on compliance with licensing basis MOE.

Participated in the Palo Verde corrective action process.

NAC is in the process of updating our 72.48 training program to include Reg Guide 3.72 Rev. 1 and NEI 1204 now that it has been endorsed by the NRC.

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NAC ACTIONS FOLLOWING AVS NAC has issued a SelfIdentification Report (SIR) to document the AVs for potential escalation into NACs Corrective Action Program (CAP) including extent of condition review pending outcome of the PEC.

NAC has performed LSDYNA analyses explicitly for CC3, CC4, CC5 and CC6 via NAC calculation 711602024 Resulting accelerations are essentially the same as FSAR CC1/CC2 NAC verified LSDYNA was used for all subcontracted sitespecific MAGNASTOR implementations.

NAC has reviewed earlier cask system designs (i.e., NACMPC and NACUMS) and found FSAR tipover analyses to be consistent with the current MAGNASTOR licensing basis.

NAC has performed an inspection of our 72.48 activities with respect to linear scaling or ratioing dispositions.

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NAC ACTIONS FOLLOWING AVS (CONTD)

In preparation for this PEC, NAC has used LSDYNA to explicitly evaluate the CC5 cask for the nonmechanistic tipover impact onto the FSAR pad & soil.

The CC5 cask was modeled in LSDYNA using an approach consistent with the licensing basis analysis described previously.

The cask model reflects the minor physical differences in the CC5 cask design (taller, thicker lid, thicker liner, inlet bars, and outer cage rebar spacing).

The ISFSI pad and underlying soil are represented with the same material models considered in the licensing basis analysis.

Results show that the LSDYNA produced accelerations for CC5 are lower than the licensing basis analysis accelerations.

The relative difference in I for these CC5 and CC1 cask models is 1.064 which is consistent with the uniform density cylinder approximation presented earlier.

These results further support the conclusion NAC made in the CC5 72.48 determination, that no additional tipover analysis was required as the existing licensing basis analysis is applicable to the CC5 cask design.

CC1/CC2 (1) CC5(2)

Basket peak acceleration, g 26.6 25.8 TSC peak acceleration, g 29.6 28.9 CC5 LSDYNA Cask & Pad Model

1) NAC Calculation 711602005, Rev. 0, Newgen VCC TipOver Analysis, 2004

2) NAC Calculation 711602034, Rev. 0, LSDYNA TipOver Analysis for CC1 and CC5 Concrete Casks, 2020 37

PRESENTATION CONCLUSION The 72.48 evaluation performed for CC5 FSAR nonmechanistic tipover did not result in a departure from the existing MOE in the licensing basis.

The CC1/CC2 FSAR LSDYNA licensing basis was reasonably determined to be applicable to CC5.

CC5 meets the same criteria NRC used to approve CC6 in the Amendment 9 SER.

There is low regulatory significance and low safety significance associated with the AVs, since no FSAR limits or criteria are based on the LSDYNA results.

NACs supplemental LSDYNA calculation confirmed the adequacy of the design.

NAC believes neither a 72.48 nor a design control violation has occurred.

NAC takes nuclear safety and regulatory compliance seriously and hopes this presentation helps clarify any misunderstandings the NRC may have with regards to the underlying facts.

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NAC International Inc.

3930 East Jones Bridge Road, Suite 200 Peachtree Corners, GA 30092 USA www.nacintl.com