ML23058A127
| ML23058A127 | |
| Person / Time | |
|---|---|
| Site: | Holtec |
| Issue date: | 03/06/2023 |
| From: | Storage and Transportation Licensing Branch |
| To: | Holtec |
| Shared Package | |
| ML23058A126 | List: |
| References | |
| CAC 001028, EPID L-2022-LLA-0002, CoC No. 1014 | |
| Download: ML23058A127 (7) | |
Text
Enclosure Request for Additional Information By letter dated December 15, 2021, as supplemented September 2, 2022, Holtec International (Holtec) submitted an application to the U.S. Nuclear Regulatory Commission (NRC) for Certificate of Compliance (CoC) No. 1014, Amendment No. 18 to the HI-STORM 100 system, pursuant to the requirements of Part 72 of Title 10 of the Code of Federal Regulations (10 CFR Part 72).
This request for additional information (RAI) identifies additional information needed by the NRC staff in connection with its review of this approval request. Each RAI below describes information needed by the staff to complete its review of the subject request.
RAI 4-1: Clarify in section 1.0.3.1 of the updated final safety analysis report (UFSAR):
a.
In step 2 the meaning of Site / Holtec.
b.
In steps 2a and 2c that the second and third bullets, respectively, end the process for that fuel loading pattern. Also, in step 2d that the first sub-bullet ends the process for that fuel loading pattern. (see also observation Th-3, Agencywide Documents Access and Management System (ADAMS) Accession No. ML22122A200) c.
In step 2a in the second bullet and in step 2d in the first sub-bullet that an application must be approved by the NRC.
d.
The purpose of comparing the peak cladding temperature (PCT) in step 2b to the PCT in step 2c.
e.
Whether there will be an additional step that includes all the 72.48 changes within the Invariant model, in addition to the new fuel loading pattern. (see also request for supplemental information (RSI) 4-2 and observations Th-2, and Th-4 (ML22122A200))
f.
As referenced in step 3, provide an example of the sites qualification report, and also describe what is meant by, as appropriate; in addition, the staff notes that configuration-controlled qualification reports will be referenced in the inspectable 72.212 report. Confirm that the Holtec Report No. HI-2200343-A Topical Report (TR)
(ML21302A147) evaluated loading pattern is completely documented in the sites configuration-controlled qualification report.
Regarding item a. above, it is not clear whether, Site / Holtec, means: 1) the site licensee and Holtec, 2) the site licensee or Holtec, or 3) the site licensee and/or Holtec. Additional clarification may be needed in figure 1.0.1, which states that the site (not site / Holtec) develops the candidate heat load pattern. It is not clear whether the site and Holtec will work together because Holtec has the invariant thermal model referenced in the Holtec Report No. HI-2200343-A TR safety evaluation (ML21216A181), the staff assumes Holtec would not provide the invariant thermal model to the site.
Regarding item b. above, it is not clear that the second and third bullets in steps 2a and 2c, respectively, and the first sub-bullet in step 2d ends the process for that fuel loading pattern.
The NRC staff notes that it is described in figure 1.0.1 step 2a that if the description in step 2a is not met, the process stops. (see also observation Th-3)
Regarding item c. above, it is not clear that the application must be approved by the NRC, not only submitted to the NRC.
Regarding item d. above, the purpose of comparing the PCT in steps 2b and 2c is not clear; it is also not clear why the PCT is the only component temperature being compared, why the PCT
2 has to be higher in step 2c than in step 2b, and why the pressure isnt also compared. See also item e., which could make the PCT, or any other comparison unnecessary.
Regarding item e. above, it is not clear whether there will be a step after step 2c, where all the 10 CFR 72.48 changes, including those made for any prior fuel loading patterns using the thermal TR, as well as the 10 CFR 72.48 changes associated with the new proposed fuel loading pattern being evaluated using the thermal TR, will be included within the invariant model and then evaluated using the thermal TR with the new proposed fuel loading pattern.
This may have an impact on all subsequent steps (e.g., steps 2d and 3) in section 1.0.3.1 of the UFSAR. All of the 10 CFR 72.48 changes have to be incorporated in the invariant model along with the new proposed fuel loading pattern to provide accurate temperature and pressure results that are then evaluated using the thermal TR. (see also RSI 4-2 and observations Th-2, and Th-4)
Regarding item f. above, an example of the qualification report has not been provided; however, this is important to safety considering that a configuration-controlled qualification report will have the heat load pattern that has been determined to meet the acceptance criteria in the TR, which will then be used for loading operations, and is referenced in the 10 CFR 72.212 report. The sites loading pattern should be completely described in the sites configuration-controlled qualification report that is referenced and inspectable through the 10 CFR 72.212 report.
This information is needed to determine compliance with 10 CFR 72.236(f).
RAI 4-2: Explain and clarify the HI-STORM 100 technical specifications (TS) appendix A, SR 3.1.2 language, such that it is consistent with the language in sections 3.1.2, and 3.2.4.9 of the Holtec Report No. HI-2200343-A TR (ML21302A147).
The HI-STORM 100 TS appendix A, SR 3.1.2 states, For OVERPACKS with installed temperature monitoring equipment, verify that the difference between the average OVERPACK air outlet temperature and independent spent fuel storage installation (ISFSI) ambient temperature is < 155 °F for OVERPACKS containing pressurized water reactor (PWR) multipurpose canisters (MPCs), < 137 °F for OVERPACKS containing boiling water reactor (BWR) MPCs (except MPC-68M) and 164 °F for OVERPACKS containing MPC-68M. For sites that have loaded in accordance with the TR HI-2200343-A, verify that the difference between the average OVERPACK air outlet temperature and ISFSI ambient temperature is less than or equal to the value computed using the topical report methodology.
Section 3.1.2 of the TR, item iii. (for the MPC-68M) states, For overpacks installed with temperature monitoring equipment, verify that the difference between the average overpack air outlet temperature and ISFSI ambient temperature is < 168 °F. The staff assumes 168 °F was calculated based on the difference between the value of the average air outlet temperature (248 °F) and the ISFSI ambient temperature (80 °F) from the example 1, table 3.1 of the TR.
Similarly, section 3.2.4.9 of the TR, item iii. states, For overpacks installed with temperature monitoring equipment, verify that the difference between the average overpack air outlet temperature and ISFSI ambient temperature is < 191 °F. The staff also assumes 191 °F was calculated based on the difference between the value of the average air outlet temperature (271 °F) and the ISFSI ambient temperature (80 °F) from the example 2, table 3.3 of the TR.
It is not clear based on the language in section 3.1.2 of the TR, item iii. in combination with the language in the TS appendix A, SR 3.1.2, whether the calculated 168 °F replaces 164 °F for the MPC-68M in the TS appendix A, SR 3.1.2 for that heat loading pattern in example 1 of the TR because an MPC-68M was used in that example. This would then be recalculated for every fuel
3 loading pattern and the appropriate numerical value in TS appendix A, SR 3.1.2 would be replaced based on the type of canister (PWR, BWR, or MPC-68M). Alternatively, because this is an example, and there is no explicit part of the chapter 2 TR methodology that describes this calculation; therefore, the difference between the measured air outlet temperature and the ISFSI ambient temperature should be less than 164 °F, as described for the MPC-68M in the TS appendix A SR 3.1.2. The staff notes that example 2 in the TR is also for an MPC-68M. There were no examples in the TR for PWR MPCs or BWR MPCs, excluding the MPC-68M.
This information is needed to determine compliance with 10 CFR 72.236(f).
RAI 4-3: Provide whether and how the 100 percent duct blockage of the HI-STORM 100 inlet vents temperature monitoring limit, as described in section 1.0.3.1, step 5 of the UFSAR, is calculated based on the methodology in section 2.3.12 of the TR.
Section 1.0.3.1, step 5 of the UFSAR describes that the site ensures loading procedures have the accurate restrictions for duct blockage allowable clearance time or temperature monitoring limit and is further referred to the HI-2200343-A section 2.3.12. Part four of the response to RSI 4-4 (ML22122A200) addresses how the duct blockage clearance times are calculated in section 2.3.12 of the TR. However, section 2.3.12 of the TR does not address recalculation of the temperature monitoring limits.
Section 2.3.12 of the TR further states, A threshold heat load is defined for all MPCs in Section 4.6 of the HI-STORM 100 UFSAR [2] at or below which fuel and component temperatures remain below the UFSAR prescribed temperature limits under a 30-day accident. The TR does not intend to modify these threshold total decay heats already established in the UFSAR and CoC. Therefore, 30-day 100% vent blockage accident is not included in the TR. The staff notes that section 11.2.13.4 of the UFSAR states, For an accident event that completely blocks the inlet or outlet air ducts of a cask with heat loads greater than the threshold heat load (Table 4.6.8a) at the time of occurrence for greater than the analyzed duration, a site-specific evaluation or analysis may be performed to demonstrate adequate heat removal for the duration of the event. See also, the RAI 8-1 that describes how the temperature limits from the UFSAR that are part of the TR acceptance criteria are not clear.
This information is needed to determine compliance with 10 CFR 72.236(f).
RAI 4-4: Clarify in section 1.0.3.1 of the UFSAR how content changes that do and do not appear in the CoC or TS, but do explicitly affect the thermal model would warrant a thermal review.
Section 1.0.3.1 of the UFSAR does not address the issue of content changes that do appear in the TS, and/or the CoC, would result in an amendment request and a thermal review with justification, which would be provided by the applicant to demonstrate that the TR included in section 1.0.3.1 is valid for the content changes. Content changes that do not appear in the TS or CoC could also necessitate a thermal review. For example, changes in the fuel assembly effective thermal conductivity, density, or specific heat for an existing approved content could affect the thermal model beyond changing the heat load pattern, and it is not clear from section 1.0.3.1 of the UFSAR whether that content change would be thermally reviewed in an amendment request. Therefore, specifying in broad terms within the implementation described in section 1.0.3.1 of the UFSAR how content changes would lead to a thermal review, would
4 provide reasonable assurance that the implementation described in section 1.0.3.1 is not obviating the need for a thermal review.
This information is needed to determine compliance with 10 CFR 72.236(f).
RAI 4-5: Clarify the following in section 1.0.3.1 of the UFSAR:
- a. How errors and uncertainties are accounted for in the TR change control process.
- b. If current bounding temperature results in the UFSAR are exceeded based on the design changes or applicant-developed heat load patterns, that the UFSAR will be updated to reflect those results and the corresponding model description.
Regarding item a. above, possible errors and uncertainties in the thermal model should be considered in the incorporation of design changes; examples of errors and uncertainties in computational fluid dynamics (CFD) simulations are provided in NUREG-2152, Computational Fluid Dynamics Best Practice Guidelines for Dry Cask Applications. This can be especially important when temperatures are close to the maximum allowable limits.
Regarding item b. above, it is not clear in section 1.0.3.1 of the application if the bounding temperature results found in the current UFSAR are exceeded that the temperature results and corresponding model description will be updated in the UFSAR.
This information is needed to determine compliance with 10 CFR 72.236(f).
RAI 4-6: Clarify in the HI-STORM 100 TS, appendix A, table 3-2a, for the MPC-68M, item iii, whether the helium backfill pressure limit will be calculated for the MPC-68M with a proposed heat load greater than 42.8 kW and up to 50 kW.
It is not clear from the HI-STORM 100 TS, appendix A, table 3-2a, for the MPC-68M, item iii whether the helium backfill pressure limit is calculated for the proposed heat load limit that is greater than 42.8 kW.
This information is needed to determine compliance with 10 CFR 72.236(f).
RAI 4-7: Address whether the friction factor used in the TRs multiple thermal models is bounding for all applicable MPCs / fuel contents. Also clarify whether the concept of cyclic drying during vacuum drying was incorporated in all of the TRs multiple thermal models.
In HI-STORM 100 Amendment No. 2 the concept of a friction factor not being bounding (see ML041250495) was raised after many MPC and fuel contents were approved. Because the TR uses invariant thermal models, it is not clear whether the friction factor concept seen in Amendment No. 2, and the concept of cyclic drying were also applied to all of the thermal models.
This information is needed to determine compliance with 10 CFR 72.236(f).
RAI 4-8: Clarify how site elevation is addressed and its effects on fuel and component temperatures when using the TR.
5 Section 4.4.4.3, Effects of Elevation, of the UFSAR describes the effects of elevation on PCT (that the reduced pressure also reduces the ventilation air flow, but the site ambient temperature also decreases, resulting in a net increase in PCT). It is not clear in the application how elevation is addressed when using the TR.
This information is needed to determine compliance with 10 CFR 72.236(f).
Errors/Typos/Suggestions:
In section 1.0.3.1, step 2., change typical to topical.
In section 1.0.3.1, change system to HI-STORM 100 system (multiple occurrences).
In section 1.0.3.1, be specific regarding the TR that you are referring to for three occurrences (i.e., HI-2200343-A [1.0.7]) (e.g., in the sentence prior to the list of steps, in steps 2., 2a., and 2c.).
In figure 1.0.1, step 2., change invariant to invariant thermal model.
In section 1.0.3.1, step 4., and figure 1.0.1, step 4., change CoC restrictions to CoC requirements.
In figure 1.0.1, step 2c., if the intent is to be consistent with section 1.0.3.1, step 2c., add language to specify the, invariant thermal model.
In figure 1.0.1, step 2c., similar to step 2a., note that if the description in step 2c. is not met, the process stops. (see also RAI 4-1b. (ML22122A200))
In figure 1.0.1, step 2d., similar to step 2a., note that if the description in step 2d. is not met, the process stops. (see also RAI 4-1b. (ML22122A200))
Page B 3.1.1-9, change, quantity of helium to helium backfill pressure limit to be consistent with the meaning in table 3-2 of appendix A of the TS, section 1.0.3.1, step 5, and section 2.3.6 of the TR.
In page B 3.1.2-4 of the UFSAR, HI-2200343 is still there. (see RSI typos / errors (ML22122A200))
In table 3-2a of appendix A of the TS, note 2 continues to refer to table 3-1; however, table 3-1 refers to all MPCs with no reference to the TR HI-2200343-A, Revision 2 methodology; whereas table 3-1a of appendix A of the TS refers to ventilated MPCs and includes a reference to the TR HI-2200343-A, Revision 2 methodology. (see RSI typos / errors (ML22122A200))
NRC staff suggests that Holtec provide the entire HI-STORM 100 Amendment No. 18 TS, not only page changes, for the staff to be in the best position to evaluate the proposed changes based on the staffs RSIs (ML22122A200) and RAIs.
RAI 6-1: Provide information to evaluate the shielding implications of documented alternate decay heat load patterns and submit details for those updated patterns or provide a generic shielding methodology for evaluation of any developed alternate decay heat loading patterns.
The NRCs staff reviewed the information provided by the applicant and evaluated the changes requested in the application. The application consisted of incorporation of the thermal
6 methodology for developing and evaluating alternate decay heat load patterns for the HI-STORM 100 MPCs as described in TR HI-2200343-A.
The applicant confirmed in their response to RSIs (ML22245A103) that the decay heat limits and burn-up, enrichment and cooling time (BECT) limits are completely independent of each other, so no BECTs are derived from decay heat limits developed using the TR. Since there is no general provision for allowing for implementation of an alternate decay heat load pattern without prior NRC review and approval of a shielding methodology, and that the applicant didnt provide supporting information to (a) evaluate shielding implications of any alternate decay heat load pattern or (b) provide a generic shielding methodology in this submittal to allow for development of alternate decay heat load patterns without prior NRC review and approval, the NRC cannot make a regulatory determination.
The staff needs this information to determine the system shielding design compliance with 10 CFR 72.236(d).
RAI 8-1: Provide additional information to clarify the component temperature limits for the following MPCs:
MPCs - 24/24E/24EF
MPCs - 32/32F
MPCs - 68/68F/68FF/68M The application uses Holtec TR HI-2200343-A (ML21302A147) for the methodology and acceptance criteria for developing heat load patterns for each canister. Holtec TR HI-2200343-A table 2.1 is consistent with and references HI-STORM 100 UFSAR table 2.II.2.9 which is applicable to the following MPCs:
MPC-32M
Version 1 of the MPC-32
Version 1 of the MPC-68 Holtec TR HI-2200343-A does not reference HI-STORM 100 UFSAR table 2.2.3 which provides maximum component temperatures for the following MPCs:
MPC - 24/24E/24EF
MPC - 32/32F
MPC - 68/68F/68FF/68M The staff notes that the MPC component temperatures including the MPC shell, lid, baseplate, and closure ring are 200 °F to 400 °F lower in HI-STORM 100 UFSAR table 2.2.3 compared to the temperature limit for Alloy X (used for the MPC shell, lid, baseplate, and closure ring) listed in HI-STORM 100 UFSAR table 2.II.2.9. It is not clear to the staff whether the application is consistent with the principal acceptance criteria listed in Holtec TR HI-2200343-A, section 1.0, which states that the, PCT (Peak Cladding Temperature) and component temperatures shall remain below their respective limits under all conditions of storage. See also ML21099A262, comment no. 1 because it refers to the HI-STORM 100, table 2.1 of the Holtec TR HI-2200343-A, and table 2.2.3 of the UFSAR. The response to comment no. 1 states, Proposed temperature limits of all components except fuel cladding in Table 2.1 of the TR are consistent with those in Table 2.2.3 and 2.II.2.9 of HI-STORM 100 Amendment 15 LAR.
7 However, table 2.1 of the Holtec TR HI-2200343-A was not updated to refer to table 2.2.3 of the UFSAR.
This information is needed to determine compliance with 10 CFR 72.236(b).