ML22069A732

Enclosure 1- Request for Supplemental Information and Observations for the Model No. HI-STAR Pbt Package - Public

ML22069A732
Person / Time
Site:	07109386
Issue date:	03/15/2022
From:	Pierre Saverot Storage and Transportation Licensing Branch
To:	Schwendenman K US Dept of Energy, National Nuclear Security Admin
P SAVEROT NRC/NMSS/DFM/STLB 3014157505
Shared Package
ML22069A730	List: ML22069A731 ML22069A732
References
EPID L-2021-NEW-0009
Download: ML22069A732 (18)

Text

Request for Supplemental Information and Observations for the Model No. HI-STAR PBT Package Docket No. 71-9386 This request for supplemental information (RSI) identifies information needed by the staff in connection with its acceptance review of the National Nuclear Security Administration (NNSA)

Model No. HI-STAR PBT (Purpose Built Tritium) package. The application is for a new package design to be used by NNSA to perform its Tritium Modernization Program mission.

CHAPTER 1 GENERAL INFORMATION 1-1 Provide licensing drawings for the tritium-producing burnable absorber rod (TPBAR) consolidation canisters.

The licensing drawings for the TPBAR consolidation canisters were not provided. This information is necessary to provide a complete description of the packaging including, the specific materials of construction, weights, dimensions, and fabrication methods.

This information is needed to determine compliance with 10 CFR 71.33(a)(5)(i).

Observations 1-2 Specify the insulation material on Licensing Drawing Nos. 11841, Revision 3 and 11856, Revision 4. Also address Note 1 of Table 3.2.3 of the safety analysis report (SAR) regarding the thermal conductivity of the insulation.

Licensing Drawing Nos. 11841, Revision 3 and 11856, Revision 4 include insulation that primarily has a thermal function and the associated flag note 5 for each drawing, refers to material properties that are defined in Table 3.2.3 of the SAR. Table 3.2.3 of the SAR includes the thermal conductivity of the insulation as a function of temperature.

Note 1 of Table 3.2.3 of the SAR describes that material with thermal conductivity values different from that cited herein can also be used as long as the thermal resistance (defined as a ratio of thickness to thermal conductivity) of the insulation board is equal to or higher than that adopted in the safety evaluations.

During normal conditions of transport (NCT) a higher thermal resistance for insulation could result in higher predicted temperatures for components internal to the package that are surrounded by the insulation, but possibly lower temperatures for components that are external to the insulation. Conversely, during the hypothetical accident conditions (HAC) regulatory fire, a higher thermal resistance for insulation could result in lower predicted temperatures for components internal to the package that are surrounded by the insulation, but possibly higher temperatures for components that are external to the insulation.

Enclosure 1

2 Therefore, it has not been demonstrated that bounding component or content temperatures have been provided based on Note 1 of Table 3.2.3 of the SAR. One function of the insulation is to prevent the lead gamma shield from melting.

The staff notes that the thermal conductivity for insulation used in the thermal model should be consistent with those values in Table 3.2.3 of the SAR; if they are not, the thermal models and the associated content and component maximum temperature and pressure results should be revised accordingly.

This information is needed to determine compliance with 10 CFR 71.33(a)(5), 71.51(c),

71.71(c)(1) and 71.73(c)(4).

1-3 Clarify if a personnel barrier is needed or used for the HI-STAR PBT package.

Some sections of the SAR include a personnel barrier (e.g., the definition of the HI-STAR PBT Package, and Sections 1.2.1.2 and 2.1.1.3 of the SAR). However, Section 3.1.5 of the SAR states that the accessible surface temperature limit criterion is satisfied, and therefore, no additional protective barriers are needed. In addition, there are no licensing drawings that include a personnel barrier.

Therefore, it is not consistently addressed in the application if a personnel barrier is needed or used for the HI-STAR PBT package. The staff notes that there is no temperature survey in Chapter 7 of the SAR to verify that the limits in 10 CFR 71.43(g) are met.

This information is needed to determine compliance with 10 CFR 71.43(g).

1-4 Provide tolerances for all Important to Safety (ITS) components on the licensing drawings so that the parameters used to calculate stresses, strains, and load distribution during drop tests can be assessed, and the as-built package can be verified as being manufactured in accordance with the analyzed design.

All tolerances that support analyses for all ITS components in the application shall be placed on the licensing drawings so that the staff can assess whether the results of the analyses including structural, shielding, and thermal analyses are valid. Tolerances for non-ITS components shall also be included, if they have a potential to impact any ITS component performance.

This information is required to determine compliance with 10 CFR 71.33(a)(5),

71.71(c)(7), 71.73(c)(1), and 71.73(c)(3).

CHAPTER 2 STRUCTURAL AND MATERIALS EVALUATION 2-1 Provide expanded test data for the prototype impact limiter and expanded test data for the prototype foam material.

The applicant proposed using three distinct prototype tests of either other packages or components to benchmark the LS DYNA methodology for the Model No. HI-STAR PBT package, with the intent that these separate tests would provide a sufficient basis, in aggregate, to justify the use of the LS DYNA modeling of the HI-STAR PBT to accurately

3 replicate the deceleration time history as well as gross structural damage of the impact limiter.

To benchmark LS DYNA models for the Model No. HI-STAR PBT package, the applicant relied in part on:

(1) physical testing of a similar package from published literature which was evaluated for a side drop and a Center of Gravity (CG) over corner drop, (2) a geometrically dissimilar package with foam impact absorbing material for an end drop, and (3) foam specimen (1-inch cubes) test performed by the foam manufacturer to document performance characteristics of their product.

This approach was necessary because the applicant did not perform prototype testing of the proposed PBT impact limiter design and thus relied on these existing tests as a surrogate for prototype testing of the HI-STAR PBT.

In past NRC approvals for similar designs, this evaluation approach was found to be acceptable because of the high degree of similarity of the geometry and materials of construction of the proposed impact limiter design (e.g., HI-STAR 180) and the previously tested and approved impact limiter (e.g., HI-STAR 100), and because the applicant had a complete set of physical testing data for the previously reviewed and approved impact limiter designs.

However, for this application:

(1) the applicant does not have a full set of design information or test data for the impact limiter designs used in the proposed benchmarking tests, (2) there is an insufficient range of drop orientations for a test with a high degree of similarity to the HI-STAR PBT, and (3) the tests do not adequately capture all relevant behavior of the impact limiter including the component foam material as used in the HI-STAR PBT package.

As a result, the staff is not able to conclude that the benchmarking approach is sufficiently robust and capable of producing analytical results for the proposed impact limiter that would be consistent with results produced in a physical test.

A robust testing protocol would address, at a minimum, the aforementioned deficiencies.

The analysis of testing results would also need to address (i) any scaling effects of the testing range, as well as foam component specimens, (ii) the effect of confining the foam material in a stainless steel skin, and (iii) strain rate effects for the entire range expected for the foam impact limiter.

This information is needed to determine compliance with 10 CFR 71.73.

2-2 Provide expanded test data to justify the assumption that only localized damage to the

4 impact limiter stainless steel skin seam welds will occur and that only minimal impact limiter foam material will be consumed by combustion.

The applicant claims that combustion of the foam impact limiter is not a credible event based on expected stainless steel skin material behavior, structural evaluations, and test results from the HI-STAR 100 package with an impact limiter with a different design, which showed that seam weld ruptures in the impact limiter skin would be localized and limited to a finite length.

However, the applicant has not provided an analysis of the dissimilarities between the two impact limiter designs sufficient to justify that the conclusions for the HI-STAR 100 can be generally applied to the Hi-STAR PBT package, nor has the applicant provided a thorough justification that seam weld splits would be localized and limited.

Further, there is no justification presented which demonstrates that even if the seam weld failures were localized, a subsequent combustion of the foam would also be localized.

This information is needed to determine compliance with 10 CFR 71.73.

2-3 Provide supplemental information on the proposed alternative to American Society of Mechanical Engineers (ASME) NB-5260 described in Table 2.1.10 as follows:

1. Describe the weld joint geometry, the redundant visual testing, and the stress limits from NG (e.g., Table NG-3352-1) that are proposed as an alternative to the nondestructive examination requirements in NB-5260.

2. Explain how the stress limits from NG, including fatigue factors such as those include in Table NG-3352-1, were considered in the fatigue considerations in SAR Section 2.6.1.3.2.

This information is needed to determine compliance with 10 CFR 71.31(c), 71.33(a)(5) and 71.35(a).

2-4 Provide supplemental information on materials properties for the materials listed in Table 2.2.3 including the allowable stress intensity values, Sm, for SA-36 and SA-516 Grade 60 as a function of temperature and the source of that information (e.g., ASME Table II Part D Table 2A).

This information is needed to determine compliance with 10 CFR 71.31(c) and 71.33(a)(5).

2-5 Provide supplemental information on the weld nondestructive examination (NDE) acceptance criteria for the non-code welds. Cite or describe the acceptance criteria for the non-code welds described in SAR Section 2.2.1.1.4.

This SAR section states, All non-destructive examinations specifications will comply with Section V of the ASME Code. ASME Section V describes requirements for NDE methods. The SAR does not describe or reference NDE acceptance criteria for non-code welds.

5 This information is needed to determine compliance with 10 CFR 71.31(c).

2-6 Provide additional information on the inspection of the packaging described in Section 8.2.3.1 Packaging Surfaces.

Include a description of the codes and standards, inspection methods, acceptance criteria for the inspection on the internal surfaces performed by a qualified corrosion metallurgist of all accessible containment surfaces, welds, heat-affected zones, and sealing surfaces for evidence of corrosive attack, cracking, or residue.

Provide the qualification requirements and identify the qualifying organization for the corrosion metallurgist conducting the inspection.

Describe how the evaluation for hydrogen embrittlement will be conducted including codes and standards, required measurements, inspection methods and acceptance criteria.

This information is needed to determine compliance with 10 CFR 71.31(c) and 71.87.

Editorial Comments

1. Section 1.1 contains the statement: High strength stainless steel alloy material in the containment system boundary to assure protection from fracture under sub-zero transport conditions.

This statement is inconsistent with the specified materials for the containment boundary.

The stainless steels specified are not high strength materials. The specified stainless steels retain ductility and toughness over a wide range of temperatures.

2. Section 1.2.1.1c. Impact Limiters contain the statements referring to the impact limiter skin as a steel material. The external surface of the impact limiter is stainless steel.

First paragraph in Section 1.2.1.1c: "Each impact limiter backbone is enveloped by crushable material, which in turn is enclosed by a painted steel skin."

Third bullet under the first paragraph in Section 1.2.1.1c: External surface of the impact limiter surrounding the crushable material is made of painted steel, a ductile material.

3. Section 2.7.1.4 Fracture Analysis contains the statement, The HI-STAR PBT cask structural members are made of ductile materials, i.e., austenitic stainless steels for cask body parts and Inconel for closure lid bolts. Therefore, fracture is not a concern... The text should be revised to be specific to brittle fracture at low temperatures.

4. Section 2.7.4 Thermal contains the statement, The outer surface of the cask, directly exposed to the fire does not slump (i.e., suffer primary or secondary creep). This condition is readily ruled out for steel components since the metal temperature remains below 50% of the metal melting point (approximately 3000 °F or 1648.89 °C).

The statement includes an inaccurate estimation of the melting temperature (stainless steel melting temperatures are in the range of 2550 °F and 2790 °F or 1400 °C and

6 1530 °C (1673 K to 1803 K)).

The statement also includes a poor estimation of the minimum creep temperature because the general rule of thumb for creep is 0.4TMelting where TMelting is in absolute temperature. For 304/316 stainless steel, the minimum temperature for creep would be 0.4(1673 K) = 669 K or 396 °C (745 °F). It is clear that said creep is not an issue as the component temperatures are too low and the HAC condition are short duration events that are insufficient for creep to occur.

CHAPTER 3 THERMAL EVALUATION 3-1 Provide justifications and additional explanations in Section 3.4.2 of the HI-STAR PBT safety analysis report (SAR) on how the four papers in Attachments A - D of the Holtec Report No. HI-2200641, Revision 0, provide an accurate representation of the material properties (e.g., thermal conductivity, density, specific heat) for the polyurethane foam, foam char, and air, as well as the quantity of foam char for the HI-STAR PBT impact limiter material during the regulatory fire and post-fire hypothetical accident conditions (HAC). Alternatively, provide HAC fire testing results of the HI-STAR PBT impact limiter with the foam that demonstrates the material assumptions in the HAC thermal model are accurate. In addition, the type of foam should be specified on the licensing drawings.

Section 8.3 of Holtec Report No. HI-2200641, Revision 0, references Holtec Report No.

HI-2200912, Revision 2, indicating that no breach of the impact limiter enclosure stainless steel skin under any analyzed scenario during the 9-meter drop event and any potential seam weld rupture would be localized and limited to a finite length; however, based on the RSI-2 above, this has not been demonstrated.

Section 8.3 of Holtec Report No. HI-2200641, Revision 0, states that the puncture results in a square-shaped penetration of 6 (each side) through the outer skin and through the foam centered on the axial location of the seals, which has also not been demonstrated.

The results of the 9-meter drop (per 10 CFR 71.73(c)(1)) and puncture test (per 10 CFR 71.73(c)(3)) have an impact on the regulatory fire test (per 10 CFR 71.73(c)(4)),

and it has not been demonstrated that the papers in Attachments A - D of the Holtec Report No. HI-2200641, Revision 0, provide an accurate representation of the material properties for the polyurethane foam or the quantity of foam char for the HI-STAR PBT impact limiter.

The paper in Attachment A of Holtec Report No. HI-2200641, Revision 0, discusses the mechanism of intumescence for pour in-place polyurethane foam; however, this paper does not specifically connect any results to the foam material used in the impact limiter.

The paper in Attachment B of Holtec Report No. HI-2200641, Revision 0, discusses the thermal response of polyurethane foam-filled small-scale systems, when exposed to fire-like heat fluxes; however, this paper does not specifically connect any results to the foam material used in the impact limiter, or to the 10 CFR 71 regulatory fire hypothetical accident conditions, or address how the scaling is appropriate for the impact limiter.

The paper in Attachment C discusses the thermal transfer, intumescence, burn distance, and plastics memory of compressed General Plastics Manufacturing Companys

7 LAST-A-FOAM FR-3700 series foam at different densities for small-scale blocks; however, this paper did not specifically connect any results to the foam material used in the impact limiter because different foam densities were used, or how the scaling is appropriate for the impact limiter.

The paper in Attachment D discusses 19 liter or 5 gallon pail fire tests and provides results for extinguish time and recession distance; however, this paper did not specifically connect any results to the foam material used in the impact limiter, or how the scaling is appropriate for the impact limiter.

The staff also notes that the licensing drawings (e.g., Licensing Drawing No. 11856, Revision 4) do not specify the type of foam in the impact limiter, which would connect that foam to thermal material properties such as, thermal conductivity, density (there is currently a range of densities specified in Table 8.1.3 of the application), and specific heat used in the thermal analysis.

This information is needed to ensure the impact limiter material is accurately modeled.

This information is needed to determine compliance with 10 CFR 71.33(a)(5)(v),

71.35(a), and 71.73(c)(4).

Observations 3-2 Provide justification in Section 3.1.2 of the SAR for the 60-day average decay heat, 1.461 watts (W) per TPBAR that is in Table 3.1.1 of the SAR.

In response to a question from the March 31, 2021 pre-application meeting, meeting summary Agencywide Documents Access and Management System (ADAMS)

Accession No. ML21098A214, Pacific Northwest National Laboratory (PNNL) provided three supporting documents:

1. TRIT-E-WP-024, Summary of PNNL Document TTP-4-660 Radioactive Source Terms and Decay Heat for the TSP Purpose-Built Transport Cask,

2. TTP-4-657, 2016 Carbon Species Test Results, and

3. TTP-4-661, Gas Available from Ruptured TPBAR and Cask Pressure During HAC.

However, Section 3.1.2 of the SAR did not summarize how those documents justified the departure from the TPBAR decay heat values: 3.35 watts/TPBAR at 30 days after removal from the reactor and quickly drops to 2.31 watts/TPBAR at a 90-day interval, for purposes of conservatism, the 30-day interval should be used for all thermal analysis, which is consistent with 3 watts per irradiated absorber rod 30 days after reactor shutdown, each of which is provided in Section 3.4.1.3 of Appendix E of NUREG-2216.

For example, a justification could include: a description of operations, assumptions, calculations, etc. This is also important as noted in Section 3.4.1.3 of Appendix E of NUREG-2216, since the temperature will be the primary driving force for the expected tritium losses from the TPBARs into containment, and the average gas temperature affects the gas pressure.

8 This information is needed to determine compliance with 10 CFR 71.71(b) and 71.73(b).

3-3 Provide justification for the statement in Section 2.7.4.1 of the SAR that describes that the containment boundary remains below 425 °F during and after the HAC fire event.

Also justify providing bulk average temperatures for the containment top flange and the top lid in Table 3.1.4 of the SAR, as opposed to maximum temperatures.

Section 2.7.4.1 of the SAR describes that the containment boundary remains below 425 °F during and after the HAC fire event. However, Table 3.1.4 of the SAR includes containment boundary components (i.e., containment shell, containment top flange (bulk average), containment baseplate, and containment boundary top lid (bulk average) and vent and drain port inner seals) that have maximum or bulk average temperatures that exceed 425 °F during the HAC post-fire, and during the HAC fire for the vent and drain port cover inner seals.

Justification has also not been provided for the bulk average temperatures of the containment top flange and the top lid in Table 3.1.4 of the SAR, a bulk average temperature is not realistic for the components and the boundary conditions. Section 2.7.4.1 of the SAR further describes that the portion of the containment boundary (e.g.,

the small area of the top flange surface not covered by impact limiter) directly exposed to the fire may have outer surface temperatures in excess of 700 °F, but the bulk metal temperature of the material volume remains under 700 °F.

This information is needed to determine compliance with 10 CFR 71.73(c)(4).

3-4 Clarify the specific heat of air in Table 3.2.5 of the SAR. Also clarify whether the correct value is used in the thermal models (e.g., for the assumption of air for the impact limiter foam material during the post-fire cooldown) and provide revised thermal models and the associated content and component maximum temperature and pressure results accordingly.

Table 3.2.5 of the SAR describes the specific heat of air as: 1006 J/kg-K (0.0421 Btu/lbm-°F); however, the specific heat of air is 0.2403 Btu/lbm-°F.

This information is needed to determine compliance with 10 CFR 71.71(c)(1) and 71.73(c)(4).

3-5 Include the maximum allowable temperature limits for the basket in Table 3.2.7 of the SAR.

The maximum temperature limits for the basket were not provided in Table 3.2.7 of the SAR; however, they are necessary to show that the maximum component temperatures remain below their maximum allowable limits.

This information is needed to determine compliance with 10 CFR 71.71(c)(1) and 71.73(c)(4).

3-6 Clarify the meaning of accommodate on the lid and vent and drain port cover metallic seal drawings.

9 The lid, and vent and drain port cover metallic seal drawings described that the seals maintain a leaktight acceptance criterion at 250 °C (482 °F) for 1 year and accommodate accident conditions at 343 °C (650 °F) for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. These limits are used in Table 3.2.7 of the SAR. It is not clear if the term accommodate also means that there is reasonable assurance that the seals will be leaktight under accident conditions at 343 °C (650 °F) for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.

This information is needed to determine compliance with 10 CFR 71.51(a)(2).

3-7 Provide justification for the cladding and basket temperatures during the HAC 30-minute regulatory fire.

It is not clear why the cladding and basket temperatures during the HAC 30-minute regulatory fire, shown in Table 3.1.4 of the SAR, are not much higher (i.e., 9 °F and 5 °F higher, respectively) than the NCT temperatures shown in Table 3.1.2 of the SAR.

Whereas a component in proximity to the cladding and basket, the containment shell, has increased by 67 °F during the HAC 30-minute regulatory fire.

This information is needed to determine compliance with 10 CFR 71.73(c)(4).

3-8 Clarify the justification provided for using insolation averaged over 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> during NCT when the package is in 38 °C (100 °F) still air with insolation, and during the HAC post-fire analysis.

Section 3.3.1.2 of the SAR describes that because of the package decay heat that results in margin to component temperature limits, the HI-STAR PBT package model includes insolation at exposed surfaces averaged over a 24-hour time period.

However, according to the table in 10 CFR 71.71(c)(1), insolation is for a 12-hour period.

Section 5.0 of the Holtec Report No. HI-2200641, Revision 0 describes that due to the large mass of metal and the size of the package, the dynamic time lag exceeds the 12-hour heating period and accordingly, the HI-STAR PBT thermal model utilizes the insolation averaged over 24-hours.

It has not been clearly justified that insolation averaged over 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> provides maximum temperatures and pressures of the HI-STAR PBT package components, surface temperature, and contents during NCT when the package is in 38 °C (100 °F) still air with insolation, and during the HAC post-fire analysis.

This information is needed to determine compliance with 10 CFR 71.43(g), 71.71(c)(1) and 71.73(c)(4).

3-9 Provide justification that the natural convection and thermal radiation heat transfer assumptions for the package surface to the environment are valid considering that there is a weather protection cover described in Section 1.2.1.1.d of the SAR. Alternatively, provide thermal analysis results during NCT and HAC that include the weather protection cover.

Section 1.2.1.1.d of the SAR describes that a weather protection cover, such as a tarp, may be secured to the HI-STAR PBT package to prevent dirt and water from accumulating on the external surfaces of the cask. Section 1.2.1.1.d of the SAR further

10 describes that a thermal evaluation shall be performed on a site-specific basis to ensure that the temperatures of all components of the HI-STAR PBT package remain below temperature and pressure limits specified in Chapter 3 of the SAR.

Therefore, it has not been demonstrated that bounding component, surface, or content temperatures have been provided. A site-specific analysis after a Certificate of Compliance (CoC) is issued is not a valid option for 10 CFR Part 71. The weather protection cover, if used, is part of the packaging and should be clearly described and shown on the licensing drawings.

This information is needed to determine compliance with 10 CFR 71.43(g), 71.71(c)(1) and 71.73(c)(4).

3-10 Address in Section 3.3.4 of the SAR if there are any modifications to the computational fluid dynamics (CFD) method using the 3-D Fluent methodology in Section 3.3.1 of the SAR. Also include in Section 3.3.4 of the SAR that the bulk water temperature should remain below the boiling temperature, i.e., 100°C (212°F).

Section 3.3.4 of the SAR briefly mentions the alternate CFD method. However, Section 3.3.4 of the SAR does not describe if there are any modifications to the CFD thermal model described in Section 3.3.1 of the SAR (e.g., orientation, not including impact limiters, water motion, etc.) in order to use this method. The purpose of the time-to-boil calculation is to prevent the water from boiling during fuel loading operations; therefore, the acceptance criterion should be included in the SAR.

This information is needed to determine compliance with 10 CFR 71.71(c)(1).

3-11 Provide justification for the need for additional measures during extended duration of operations given the times calculated in Table 3.3.3 of the SAR and overall low decay heat.

Section 3.3.4.1 of the SAR describes that in the unlikely event that the maximum allowable time provided in Table 3.3.3 is found to be insufficient to complete wet transfer operations, forced water circulation may be provided to remove the decay heat from the package cavity. The time-to-boil limits in Table 3.3.3 of the SAR range from 51 hours5.902778e-4 days <br />0.0142 hours <br />8.43254e-5 weeks <br />1.94055e-5 months <br /> to 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br />.

This information is needed to determine compliance with 10 CFR 71.87.

3-12 Provide justification for the number of TPBARs included in the 1/8th symmetry model shown in Figure 3.3.1 of the SAR.

Figure 3.3.1 of the SAR is of a 1/8th symmetry model that includes 148 TPBARs and represents one half of a TPBAR canister because there are four canisters within the HI-STAR PBT. Each canister can hold up to 300 TPBARs; therefore, a 1/8th symmetry model should include 150 TPBARs. Therefore, it has not been demonstrated based on the thermal model that bounding component or content temperatures have been provided during NCT, HAC, and vacuum drying.

This information is needed to determine compliance with 10 CFR 71.33(b)(3),

71.33(b)(7), 71.51(c), 71.71(c)(1) and 71.73(c)(4).

11 3-13 Provide justification for the package surface solar absorptivity provided in Table 3.4.1 of the SAR for the HAC post-fire conditions.

Table 3.4.1 of the SAR references Table 3.2.4 of the SAR for the package surface solar absorptivity during post-fire conditions. However, it has not been shown that the surface solar absorptivity value is appropriate for sooted conditions that are expected during the HAC post-fire conditions.

This information is needed to determine compliance with 10 CFR 71.73(c)(4).

3-14 Provide documentation of the method used for the differential thermal expansion calculations in Holtec Report No. HI-2200641, Revision 0.

Holtec Report No. HI-2200641, Revision 0, describes the analysis file used to perform the differential thermal expansion calculations and Table 3.4.2 of the HI-STAR PBT application summarizes the results. Section 3.4.4 of the SAR describes that the differential thermal expansion is calculated in Holtec Report No. HI-2200641, Revision 0.

However, the method (i.e., using thermal expansion coefficients at the worst case results) used for the differential thermal expansion calculations was not provided in Holtec Report No. HI-2200641, Revision 0.

This information is needed to determine compliance with 10 CFR 71.71(c)(1).

3-15 Provide documentation in Section 3.3.3.1 of the SAR, of the method used to calculate the tritium in-leakage/permeation that is summarized in Table 3.3.5 of the SAR.

Section 3.3.3.1 of the SAR describes that the tritium in-leakage/permeation is calculated for NCT, Table 3.3.5 of the HI-STAR PBT application summarizes the results, and Section 3.3.3.1 of the SAR concludes that tritium makes up less than 5% of the package cavity volume.

However, the calculational method used for the tritium in-leakage/permeation calculations was not provided in Section 3.3.3.1 of the SAR. This is necessary to demonstrate that combustible gas generation makes up less than 5% of the package cavity volume.

This information is needed to determine compliance with 10 CFR 71.43(d).

Editorial:

Change operatihistonal on page 3.1-5 to operational Tables 3.2.10, 3.2.11, and 3.2.12 referenced in Section 3.1.3 of the SAR do not exist; the table should be Table 3.2.7.

CHAPTER 4 CONTAINMENT EVALUATION 4-1 Provide the references below for staff to verify the information used to calculate the gas available in ruptured tritium-producing burnable absorber rods (TPBARs) and the cask

12 pressure during hypothetical accident conditions (HAC). These references are listed in the Pacific Northwest National Laboratory (PNNL) Report No. TTP-4-661, Gas Available from Ruptured TPBAR and Cask Pressure During HAC.

Deibler, JE, 2017, TPBAR Void Volume Ratios and Void Volume Compendium, PNNL-TTP-1-3096 Rev. 0, Pacific Northwest National Laboratory, Richland, WA.

Geelhood, K.G., 2016, Analysis of Mark 9.2 Design TPBARs Including Permeation Calculations and Impact of Accidents for Bounding WBN Cycles using TROD Version 1.13 (U), PNNL-TTP-1-3082 Rev. 2, Pacific Northwest National Laboratory, Richland, WA.

Meriwether, G.H. 2007, Estimates of He-3 Redistribution Effects on Core Power Profiles for Watts Bar Mark-9.2 Design, PNNL-TTP-1-1107 Rev. 0, Pacific Northwest National Laboratory, Richland, WA.

Schmitt, B.E. 2012, TPBAR Tritium Releases (U), PNNL-TTQP-1-735, Rev. 10, Pacific Northwest National Laboratory, Richland, WA.

This information is needed to determine compliance with 10 CFR 71.73(c)(4).

Observations 4-2 Provide the classification of important to safety (ITS) components according to categories A, B, and C from NUREG-6407 on the licensing drawings (e.g., Licensing Drawing No. 11841, Rev. 3).

NUREG/CR-6407, Classification of Transportation Packaging and Dry Spent Fuel Storage System Components According to Importance to Safety, provides a description of packaging components that are important to safety and classifies them in accordance with categories A, B, and C.

For example, all of the containment boundary components should be ITS Category A.

This type of information was not provided on the licensing drawings for the category of the ITS components that are part of this new HI-STAR PBT package design so that the staff can assess whether the results of the thermal analysis are valid. Tolerances for non-ITS components shall also be included, if they have a potential to impact any ITS component performance.

This information is needed to determine compliance with 10 CFR 71.33(a)(5).

4-3 Clarify that the top lid bolts and vent/drain cover bolts are not part of the containment boundary and revise Licensing Drawing No, 11841 Rev. 3 and SAR Tables 2.1.9 and 2.2.6 accordingly.

The applicant stated, in SAR Section 4.0, that the HI-STAR PBT package containment system consists of the containment shell, containment base plate, containment top flange, top lid, top lid bolts, top lid vent and drain port and port covers, and their respective seals and welds, as specified in the drawing package in SAR Section 1.3.

Parts List of Drawing No. 11841 Rev. 3 categorizes the port cover bolt (item 15) and top lid bolt (item 16) primarily functions as containment boundary. SAR Tables 2.1.9 and

13 2.2.6 also identify the top/closure lid bolts and lid port cover bolts functions as containment boundary.

SAR Table 8.1.2 lists the HI-STAR PBT containment components tested for each of fabrication, pre-shipment, maintenance, and periodic leakage rate tests, in accordance with the ANSI Standard. However, both the top lid bolts and port cover bolts, which are specified with the main function of serving as containment boundary in Licensing Drawing No, 11841 Rev. 3 and SAR Tables 2.1.9 and 2.2.6, are not leak tested during a fabrication, periodic, or pre-shipment leakage rate test.

This information is needed to determine compliance with 10 CFR 71.51.

CHAPTER 5 SHIELDING EVALUATION 5-1 Provide information to demonstrate that the data provided in Table 7.D.1 (SHEET 2 of 3) is the bounding total radiation source with the distribution in the package for the given limit of the total number of TPBARs.

The applicant provided the radiation source term in Table 7.D.1 (SHEET 2 of 3) of the application. The applicant also provided the material composition of the TPBAR in Table 5.3.1 of the application. However, it is not clear what irradiation conditions of the TPBAR produced this source term. It is not clear either how this source term is related to the axial burnup profile as provided in Table 5.2.1 of the application.

The information needs to include the activation reaction chains (e.g., 58Ni(n, p)58Co, 59Co(n, )60Co, 50Cr (n, )51Cr, 58Fe (n, )59Fe) considered in the activation analyses, the neutron flux that the TPBARs were exposed to, and the total exposure time that produce the source term [Ref. 1, 2].

The information should also be consistent with the TPBAR material composition as provided in Table 5.3.1 of the application. Information on the impurity level of 59Co in the stainless steel will help justify the source term since Table 5.3.1 does not provide this information which is critical to calculation of the 60Co concentration.

This information is needed to determine compliance with 10 CFR 71.47 and 71.51.

References:

1. W. C. Morgan, Long-Term Neutron Activation Product of Nickel-58, General Electric Hanford Atomic Products Operation - Richland, Washington, December 11, 1963.

2. ML11229A714, Neutron Activation and Activation Analysis, United States Nuclear Regulatory Commission, https://www.nrc.gov/docs/ML1122/ML11229A714.pdf 5-2 Revise the shielding model to calculate the dose rate on the surface of the package body under normal conditions of transport.

10 CFR 71.47(a) requires the dose rate at any point of the package surface not to exceed 2 mSv/h. The applicant calculated the dose rate at 2 meters from the surface of

14 the impact limiters as shown in Figure 5.1.2. It is not clear what the maximum dose rate is on the side surface of the package body.

This information is needed to determine compliance with 10 CFR 71.47(a).

5-3 Provide shielding analyses for the package under side-drop accident that creates lead slump on the side of the package.

The applicant provided the dose rate for the package under end-drop accident with consideration of lead slump. The application states, These are the lead slump in the lead shielding as a result of the 9-meter (30-foot) drop, and lead slump in the base plate a result of a slap-down accident.

However, there is no discussion on the dose rate of the package under a side-drop accident that would cause the lead slump to the side at a horizontal position. Since the TPBAR source term has an axial profile with the maximum source in the middle of the package, the maximum dose rate may occur at the side rather than at the end of the package under a side-drop accident condition.

This information is needed to determine compliance with 10 CFR 71.51.

5-4 Demonstrate that the skin of the impact limiter will be able to support the dead weight of the canister and contents under hypothetical accident conditions.

The applicant provided the dose rate for the package under an end-drop accident with consideration of lead slump. The application also states, Furthermore, the top and bottom external shank of the lifting trunnions are removed. Only the impact limiter strongback plate and skirt plate are credited in shielding. Based on licensing drawing 11856, the skin is made from 11-gauge stainless steel sheet, which is 0.125. However, it is not clear whether the skin of the impact limiter under HAC would be able to keep its geometric shape under HAC and thus support the weight of the canister loaded with TPBARs and if credit can be taken in the shielding calculations, even without considering the fact that the applicant considered that the shells have been teared under one-meter drop.

This information is needed to determine compliance with 10 CFR 71.51.

5-5 Justify the acceptability of the shielding calculation results and reperform the shielding calculations as necessary.

The applicant provided an output file for its shielding calculations. However, the staff notes that the calculation does not meet the acceptable convergence criteria, as specified in the MCNP users manual.

Also, the staff noted that there multiple warning messages that indicate the calculation did not converge adequately. As a result, the results of the shielding calculation may be unreliable [Ref. 1]. The staff is unable to make a licensing decision based on unreliable dose rates.

This information is needed to determine compliance with 10 CFR 71.47.

Reference 1:LA-UR-17-29981, MCNP User Manual, Code Version 6.2, Los Alamos National Laboratory, October 27, 2017. (page 3-183) Printed with each tally bin is the

15 relative error of the tally corresponding to one standard deviation. These errors cannot be believed reliable (hence neither can the tally itself) unless the error is fairly low.

Results with errors greater than 50% are useless, those with errors between 20% and 50% can be believed to within a factor of a few, those with errors between 10% and 20%

are questionable, and results with errors less than 10% are generally (but not always) reliable, except for detectors. Detector results are generally reliable if their associated relative errors are below 5%. The tally fluctuation charts at the end of the output file base their results on the information from one specified bin of every tally. (See the TF card.) This bin also is used for the weight-window generator and is subject to ten statistical checks for tally convergence, including calculation of the variance of the variance (VOV). The VOV can be printed for all bins in a tally by using the DBCN card.

A tally is considered to be converged with high confidence only when it passes all ten statistical checks.

5-6 Demonstrate that the results of the shielding calculations for the package under normal conditions of transport and hypothetical accident conditions are reliable.

The applicant calculated the dose rate for the package under hypothetical accident conditions. The applicant states that it made four calculations which include:

Table 7-1 MCNP HI-STAR PBT Calculations Photon Energy Input File Condition Range (MeV) 4tpbarsrg1 0.45-1.1 Normal 4tpbarsrg2 1.1-1.7 Normal 4tpbarsrg1ac2 0.45-1.1 Accident 4tpbarsrg2ac2 1.1-1.7 Accident However, the applicant provided only input files for 4tpbarsrg1 and 4tpbarsrg1ac2 models and an output file for 4tpbarsrg1ac2. Because the models broke the shielding calculations into four cases and each case covers a specific scenario and source term energy range, it is necessary to examine the output files that show that all calculations are converged in accordance with the convergence acceptance criteria as specified by the MCNP users manual.

This information is needed to determine compliance with 10 CFR 71.51.

CHAPTER 7 OPERATING PROCEDURES 7-1 Demonstrate that a package cavity vacuum pressure of less than 10 Torr for greater than 30 minutes, as the dryness criteria for vacuum drying, will not raise the package cavity hydrogen content above 5%.

The applicant stated, in SAR Section 7.0, that the cask will be dried to the criteria of SAR Table 7.1.2 (with cask cavity pressure 10 Torr for 30 minutes for vacuum drying) so that there shall be no remaining water to generate hydrogen through radiolysis and it is not expected that there shall be any source of hydrogen that will raise the cask cavity hydrogen content above 5%.

16 Its not clear to the staff how the value of 10 Torr, instead of 3 Torr, is determined to be the dryness criteria that will result in a hydrogen generation less than 5% in the package.

The applicant needs to demonstrate (e.g., through a calculation) that the use of 10 Torr as the dryness criteria will generate hydrogen at less than 5% in volume.

This information is needed to determine compliance with 10 CFR 71.43(d).

7-2 Clarify in SAR Section 7.1.2.1, Step 5, that the metallic seals should be replaced after each use.

The applicant stated that the inner metallic seal is used as the containment seal for the top lid and vent/drain ports (SAR Section 4.1.3.1); the seals of the HI-STAR PBT cask are to be replaced and retested for each cask loading and closure (SAR Sections 4.0 and 8.2.3.4); and the metallic seals and elastomeric O-rings are replaced on the lid, port cover plates, and seal test ports as needed (SAR Section 7.1.2, Step 5).

However, it cannot be as needed. Consistent with SAR Section 8.2.3.4, the applicant needs to replace the metallic seals after each use because of the deformation caused by pressure and stress.

This information is needed to determine compliance with 10 CFR 71.43(f) and 71.51.

7-3 Clarify if permeation of the outer elastomeric O-rings is possible during leakage rate testing, such that the elastomeric O-rings should be replaced with metallic seals, given the package contents are TPBARs.

It has not been addressed in SAR Chapter 4 whether tritium permeation of the outer elastomeric O-rings is possible during leakage rate testing that could result in a release of radioactive material. The applicant should also consider the repeated use of elastomeric O-rings.

This information is needed to determine compliance with 10 CFR 71.51.

7-4 Clarify (1) the criteria and conditions for replacement of the bolt-washer combination with flanged bolts, as noted in Licensing Drawing No. 11841 (sheet 1 of 4) and (2) the torque requirements for flanged bolts used to tighten containment components in place.

Licensing Drawing No. 11841 (sheet 1 of 4) Note #27 notes the bolt and washer combination may optionally be replaced with flanged bolts.

The applicant needs to clarify (1) the criteria and conditions acceptable for replacement of a bolt-washer combination with flanged bolts, as noted in Licensing Drawing No.

11841 (sheet 1 of 4) and (2) whether the torque requirements of Table 7.1.1 are applicable to the flanged bolts to ensure all containment components are tightened in place.

This information is needed to determine compliance with 10 CFR 71.43(f) and 71.51.

CHAPTER 8 MAINTENANCE PROCEDURES

17 8-1 Clarify whether a leaktight criterion is applied for helium only or for all gases, including tritium outgassing, for the pre-shipment, maintenance, and periodic leakage rate tests. If the criteria is only for leakage of helium, provide the procedure in SAR Chapter 8 for separating helium from other gases (e.g., tritium outgassing) during the pre-shipment, maintenance, and periodic leakage rate tests.

The applicant stated, in SAR Section 8.1.4, Leakage Tests, that a pre-shipment leakage rate test of containment seals is performed following loading of authorized contents into the package. SAR Tables 8.1.1 and 8.1.2 show that a leaktight criterion of 1x10-7 ref-cm3/s (air) is used for pre-shipment, maintenance, and periodic leakage rate tests.

Its not clear to the staff whether the leaktight criterion is applied for helium only or for all of the gases released from the package, including tritium outgassing from bulk materials, outgassing from TPBARs and package internal surfaces, which could be wetted with tritium.

This information is needed to determine compliance with 10 CFR 71.43(f) and 71.51(a).

8-2 Provide the precautions, needed for test operations and workers safety, in the procedures of the pre-shipment leakage rate test and maintenance/periodic leakage rate tests, respectively, in SAR Chapters 7 and 8.

Appendix E, Section 4.4.5 of NUREG-2216 (Standard Review Plan for Transportation Packages for Spent Fuel and Radioactive Material) notes: Once a package has been used for the shipment of irradiated TPBARs, the internal surfaces of the package will have been contaminated with tritium. Additional precautions will, therefore, have to be built into the procedure used for the maintenance and periodic leakage tests.

Section 9.4.2, Maintenance Program, of NUREG-2216 notes that the appropriate precautions should be taken to verify that the internal walls of the containment vessel are not outgassing. This type of information can be particularly important to note for leakage testing purposes to determine the amount of tritium (as tritium oxide (HTO)) that might have to be pumped through the vacuum system and as information to be used for pre-inspection purposes so that the workers can be appropriately notified of potential HTO outgassing problems.

The applicant has Caution Notes such as tritium releases are possible when opening an empty cask during other operations as well in SAR Section 7.1.1 and real time monitoring for tritium in air must be engaged in the work area in SAR Section 7.2.2.

The applicant should also add such Caution Notes in SAR Chapters 7 and 8 for leakage rate tests.

This information is needed to determine compliance with 10 CFR 71.43(f) and 71.51(a).

ML22069A730; ML22069A732

• via email OFFICE NMSS/DFM/STLB NMSS/DFM/CTCFB NMSS/DFM/MSB* NMSS/DFM/MSB*

NAME PSaverot PS JPiotter JP DDunn DD TBoyce TB DATE Mar 10, 2022 Mar 10, 2022 Mar 10, 2022 Mar 10, 2022 NMSS/DFM/CTCFB OFFICE NMSS/DFM/CTCFB NMSS/DFM/NARAB NMSS/DFM/FFLB NAME JIreland JI ZLi ZL MDiaz MD FChang FC DATE Mar 11, 2022 Mar 11, 2022 Mar 11, 2022 Mar 14, 2022 OFFICE NMSS/DFM NMSS/DFM/STLB NMSS/DFM/STLB NMSS/DFM/STLB DMarcano NAME SFigueroa SF CJacobs CJ PSaverot PS CBajwa for CB DATE Mar 14, 2022 Mar 14, 2022 Mar 15, 2022 Mar 15, 2022