ML25253A289
| ML25253A289 | |
| Person / Time | |
|---|---|
| Site: | Holtec |
| Issue date: | 09/09/2025 |
| From: | Holtec |
| To: | Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML25253A287 | List: |
| References | |
| 5014989 | |
| Download: ML25253A289 (1) | |
Text
Attachment 1 to Holtec Letter 5014989 Page 1 of 4 NRC Pre-Decisional Enforcement Conference Information Requests Apparent Violations A and B NRC Request - Provide details on operating experience on water found in unloaded casks (and loaded if any exists) including how the unloaded cask storage con"guration might differ from a loaded cask con"guration Holtec has requested this information from users and expects to be able to provide additional information to the NRC staff by September 16 NRC Request - Provide FSAR sections that direct general licenses on recovery actions to take after a "ood and any drawings that show the drain line. Include any recovery procedures provided to users. Also include communications to users about potential violations.
HI-STORM FW FSAR Section 12.2.7.4 contains the recovery actions to be taken after a "ood, and says:
At the completion of the "ood, exposed surfaces may need debris and adherent foreign matter removal. For the HI-STORM FW Version E, Version F, and Version E 1 a drain connection may be included to assist with removal of any additional water that remains after the "ood.
HI-STORM FW FSAR Section 12.2.13.4 contains the corrective actions to be taken after a 100% blockage of air vents (by any material)
For an accident event that completely blocks the inlet or outlet air openings for greater than the analyzed duration, a site-speci"c evaluation or analysis may be performed to whether adequate heat removal for the duration of the even would occur. Adequate heat removal is de"ned as the minimum rate of heat dissipation that ensures cladding temperatures limits are met and structural integrity of the MPC and overpack is not compromised. For those events where an evaluation or analysis is not performed or is not successful in showing that cladding temperatures remain below their short term temperature limits, the sites emergency plan shall include provisions to address removal of the material blocking the air inlet openings and to provide alternate means of cooling prior to exceeding the time when the fuel cladding temperature reaches its short-term temperature limit.
The FSAR clearly indicates that users must have provisions to remove debris, foreign material, water, or any other material as recovery from both the "ood and vent blockage events. These post-accident recovery actions apply to all versions of HI-STORM FW. No to Holtec Letter 5014989 Page 2 of 4 speci"c recovery procedures are provided to users, as the FSAR indicates it is referred to the sites emergency plan.
A drawing showing the drain line is included as a proprietary attachment to this letter.
Meeting minutes from meetings held with users related to the potential violations are also included as a proprietary attachment to this letter. Note that these are just summary meeting minutes, these meetings are not transcribed in their entirety.
Apparent Violation C NRC Request - Provide the FSAR section and any supporting analysis related to the tornado missile impact on the MPC lid in the HI-STORM overpack The direct missile impact on the MPC lid is discussed in Section 3.4.4.1.3 (b) of the HI-STORM FW FSAR. As stated in that section:
The MPC upper lid is analyzed for a direct missile impact because, when the MPC is placed inside the HI-TRAC VW, the MPC lid is theoretically accessible to a vertically downward directed small or intermediate missile.
The text indicates that the analysis was performed because the design of the HI-TRAC exposes the MPC lid to a potential missile. The actual evaluation is contained in the supporting calculation package (HI-2094392, Appendix D, included as a proprietary attachment to this letter). The analysis contained in that calculation package clearly indicates that the evaluation takes no consideration for the surrounding overpack. The evaluation is a direct impact to the steel plate of the MPC lid only. Therefore, the analysis is unchanged for an MPC in a HI-STORM FW overpack (with no lid) or in a HI-TRAC VW transfer cask, as documented in the existing 72.48 screening.
Apparent Violation D NRC Request - Are there any additional direct comparison to FSAR results for the speci"c cases in the applicable 72.48? NRC staff wants to understand how Holtec came to the essentially the same conclusion.
As stated during the conference, Holtec did not run the exact same FSAR lid analysis in both ANSYS Version 11 and ANSYS Version 2020. Prior to the introduction of the Version F in 72.48 # 1516, the common lid was analyzed using ANSYS Version 11. In accordance with the guidance in NEI 12-04, Holtec performed a validation and veri"cation of ANSYS Version 2020 and documented it in accordance with Holtecs QA program requirements. NEI 12-04, Section 6.8.1 states that, the revised software must be used to re-analyze one or more representative cases that were analyzed using the previous version of the software. The to Holtec Letter 5014989 Page 3 of 4 results of the old and new sets of representative cases are then compared to determine if the revised software produces results that are conservative, non-conservative, or essentially the same.
Holtec ran the same cases in Version 11 and Version 2020 and documented them in HI-2012627. Speci"cally, for the lid evaluation, case VM7 uses the same element type and nonlinear material model that are used to model the common lid during the tipover event.
As documented in HI-2012627, the results for case VM7 (and all other cases) for Version 11 and Version 2020 are different by less than 1%. Based on the comparison of results from the two versions, Holtec determined that the modi"ed MOE gives essentially the same results.
NEI 12-04, Section 6.8.1.2 states that:
The determination of whether a new analysis result would be considered essentially the same as the previous result can be made through benchmarking the revised MOE to the existing one, or may be apparent from the nature of the differences between the MOEs. When benchmarking a revised MOE to determine how it compares to the previous one, the analyses that are done must be for the same set of conditions to ensure that the results are comparable, and the revised MOE should only be used where the benchmarking has demonstrated it to be conservative or essentially the same.
Case VM7 (and all other cases) were done using the exact same set of conditions, the results were shown to be comparable, thus completing the benchmarking as expected by the guidance document. ANSYS Version 2020 is only used because the cases that show essentially the same results are appropriately representative of the scenarios for which it is used in this proposed activity.
Apparent Violation E NRC Request - Please provide the QI that was written to document the position paper concern.
Holtec QI-3620 is included as a proprietary attachment to this letter.
Potential Corrective Actions During the conference it was discussed that Holtec disagrees with the apparent violations as currently documented. Holtec has entered the apparent violations into our corrective action program for tracking, but has not performed a full review and determined "nal corrective actions. However, if at the conclusion of the full NRC enforcement process the to Holtec Letter 5014989 Page 4 of 4 violations remain as currently stated, Holtec has considered corrective actions that may be implemented.
For Apparent Violations A and B, if the NRC determines that these changes should have been submitted for an amendment, Holtec will submit amendments as required to bring systems back into compliance. Holtec would also work with general licensees to support the exemption requests that may be needed to continue loading campaigns. Holtec would also perform a full extent of condition review to ensure similar issues do not exist with other 72.48 evaluations, and include any updated training or procedures necessary.
For Apparent Violation C, if the NRC determines that a full evaluation was required, Holtec would update the 72.48 to document a full evaluation. Holtec would also do an extent of condition review to identify any other similar 72.48 screenings and update those documents as necessary.
For Apparent Violation D, if the NRC determines that the representative cases performed were not sufficient to provide reasonable assurance that the new ANSYS code version provides essentially the same results as the previous version, Holtec would run the exact FSAR analysis with ANSYS Version 2020 and document that the results are essentially the same as provided in the FSAR. The 72.48 documentation would be updated to reference the additional FSAR case. Holtec would review other 72.48s for the extent of condition and update any evaluations which contain the same conclusions. Holtec would also update the 72.48 training and procedural guidance to make it clear that the representative and benchmarking cases described in the NEI guidance must match exact FSAR scenarios to prevent recurrence of the issue.
For Apparent Violation E, the issue has been fully evaluated in the QI process, and corrective actions have been completed as identi"ed in the proprietary QI attached to this letter.