ML25042A547

Enclosure 1 - Request for Additional Information for the Model No. Volunteer Package (Public)

ML25042A547
Person / Time
Site:	07109403
Issue date:	02/12/2025
From:	Storage and Transportation Licensing Branch
To:
Shared Package
ML25042A545	List: ML25042A546 ML25042A547
References
EPID L-2023-NEW-0007
Download: ML25042A547 (1)

Text

Enclosure 1 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Request for Additional Information for the Model No. VOLUNTEER Package Docket No. 71-9403 This request for additional information (RAI) identifies information needed by the staff in connection with its review of the NAC International (NAC) Model No. VOLUNTEER package.

CHAPTER 1 GENERAL INFORMATION 1-1 PROPRIETARY 1-2 PROPRIETARY CHAPTER 2 STRUCTURAL AND MATERIALS EVALUATION 2-1 PROPRIETARY 2-2 Provide a structural evaluation of the vitrified High-Level Waste (HLW) canisters for the Normal Conditions of Transport (NCT) and Hypothetical Accident Conditions (HAC) loads.

The safety analysis report (SAR) section 1.2.2.2 describes the canisters for vitrified HLW contents. The canisters have a nominal 24-inch OD and a minimum 3/8-inch nominal shell thickness, and a maximum nominal overall length of 180 inches (15 feet) and 120 inches (10 feet), respectively. The HLW canister is also described in other sections of the SAR and included in the thermal model for thermal analyses. However, relevant details of the HLW canisters and their structural evaluations for the NCT and HAC loads are not addressed in the SAR.

This information is needed to determine compliance with Title 10 of the Code of Federal Regulations (10 CFR) Section 71.71 and 10 CFR 71.73.

2-3 Provide a justification for using a 15.6g equivalent static acceleration load for the Volunteer package structural evaluation to meet the HAC puncture test requirement in accordance with 10 CFR 71.73(c)(3).

In the SAR section 2.7.3, the applicant calculates a 15.6 grams applied acceleration load based on the flow stress of the mild steel puncture bar for use in the structural evaluation of the package to meet the HAC puncture test requirement. In accordance with 10 CFR 71.73(c)(3), the package is required to be evaluated for a 1-meter (40 inches) free drop in a position for which a maximum damage is expected, onto the upper end of a solid, vertical, cylindrical, mild steel bar, mounted on an essentially unyielding horizontal surface.

The SAR description does not provide any explanation and justification for the use of the 15.6g applied acceleration load based on the flow stress of the mild steel puncture bar.

The applicant needs to demonstrate that the applied acceleration load in the package stress analysis is equivalent to or conservative when compared to the equivalent static acceleration load generated by the 1-meter drop on the puncture bar.

This information is needed to satisfy the requirements of 10 CFR 71.73(c)(3).

2-4 Provide additional information to justify the ultrasonic testing (UT) as a replacement for radiographic testing (RT) to examine transportation packaging welds.

In Section 1.2.5, the applicant states that UT examination of the circumferential weld between the cask outer shell and flange will be performed in lieu of RT examination per American Society of Mechanical Engineers (ASME) Code Case N-659-2 requirements.

ASME Code Case N-659-2 is not approved for use per Regulatory Guide (RG) 1.193, Revision 5. The justification in RG 1.193 is that interchangeability of the techniques, UT to replace RT, has not yet been fully demonstrated and UT acceptance criteria for fabrication/construction weld inspection have not yet been adequately defined and the applicability of UT in the presence of high levels of acoustic noise, such as that found in austenitic materials, is not fully understood.

Impact and implications of the expanded examination volume (full thickness) required for UT for fabrication/construction must also be addressed.

Performance demonstration requirements including acceptance criteria for UT equipment, procedures, and personnel used for construction fabrication activities must be addressed.

Performance demonstration for nondestructive examination is included in ASME Code section V, Article 14, Examination System Qualification.

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

CHAPTER 3 THERMAL EVALUATION 3-1 Clarify if there is any applicable thermal limit when performing vacuum drying of the package and its contents. Also, justify the following vacuum drying criteria that are provided in SAR sections 8.1.2.1 (step 14), and 8.1.2.2 (step 5):

To evacuate the cask cavity to a pressure below 10 torr (13 mbar) and continue vacuum pumping for at least 15 minutes more.

Isolate the vacuum pump and monitor the cask cavity vacuum pressure for a minimum of 10 minutes.

If the pressure rise is greater than 5 torr (6.7 mbar), vacuum drying operations are repeated.

SAR chapter 3 does not include any drying analysis or temperature limits that can be used to justify the drying criteria provided in SAR chapter 8. The U.S. Nuclear Regulatory Commission (NRC) staff have accepted vacuum drying methods comparable to those recommended in PNL-6365, Evaluation of Cover Gas Impurities and Their Effects on the Dry Storage of LWR Spent Fuel, issued November 1987 (Knoll and Gilbert, 1987).

This information is necessary to determine compliance with 10 CFR 71.43(d) and (f).

3-2 Justify the heat transfer coefficient value used to perform the analysis of the 30-minute regulatory fire test.

SAR Section 3.4.2 states that a convection film coefficient that is 50 percent higher than the recommended value provided in S.D. Wix, Proceedings Volume 2, the 11th International Conference on the Packaging and Transportation of Radioactive Materials (PATRAM95), pp 672 is conservatively used during the fire period in the analysis.

During the fire regulatory test, the NRC staff have accepted values provided in Gregory, J.J., R. Mata, and N.R. Keltner, Thermal Measurements in a Series of Large Pool Fires, SAND85-0196, TTC-0659, UC-71, Sandia National Laboratories, Albuquerque, NM, August 1987.

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

CHAPTER 4 CONTAINMENT EVALUATION 4-1 Clarify the following in the SAR related to containment or American National Standards Institute (ANSI) N14.5 American National Standard for Radioactive Materials - Leakage Tests on Packages for Shipment.

• In the first paragraph of section 4 of the SAR, in the last sentence, 10 CFR 71.51(a)(2) would be a more specific citation of the regulation, rather than 10 CFR 71.51(a), considering 10 CFR 71.51(a)(1) is used in the first sentence of the first paragraph of section 4 of the SAR.

• Section 4.1 of the SAR describes that a sketch of the containment boundaries is included in figure 4.1-1. This should be described as the containment boundary, since there is one containment boundary. Similarly, section 4.1 describes The only welds within the containment boundaries, which should also be described as the containment boundary.

PROPRIETARY PROPRIETARY PROPRIETARY PROPRIETARY On page 9.2-2 of the SAR, reference 9-4 is cited as ANSI N14.5-1997; however, references 4-3 and 9-4 have it listed as ANSI N14.5-2014. The staff notes that ANSI N14.5-2022 is also available.

This information is necessary to determine compliance with 10 CFR 71.51(a)(1) and (2).

4-2 PROPRIETARY 4-3 Provide a description and evaluations in section 4.3 Containment under hypothetical accident conditions, of the SAR of the tritium permeation rate of seals for a tritium-producing burnable absorber rod (TPBAR) shipment.

The release of tritium into the cask cavity from all 1200 rods, 1198 rods that are event-failed and 2 rods defined to be prefailed, has the potential of releasing a significant quantity of tritium (> 1A2) into the cask cavity. To provide assurance that the accident release limit of 1A2/week is not exceeded under accident conditions the port and lid seal permeation rates evaluations should be provided in section 4.3 of the SAR.

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

4-4 PROPRIETARY CHAPTER 5 SHIELDING 5.1 Provide a description in SAR chapter 5, Shielding, to address tritium contamination issues to ensure the reusability of the Volunteer package for non-TPBAR content.

Chapter 5 of the SAR did not address precautions (e.g., cavity gas monitoring for tritium, internal and external tritium contamination surveys) that will be taken to minimize the risk of excessive contamination of NAC Volunteer packages during the loading and unloading of TPBAR contents to ensure the reusability of the NAC Volunteer package for transport of non-TPBAR contents. Alternatively, summarize how this is addressed in the operating procedures.

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

5-2 Provide a description of Tritium contamination surveys counting methods to ensure correct measurement of tritium present.

There is no information in the SAR related to the Tritium contamination surveys counting methods.

This information is required to determine compliance with 10 CFR 71.87(i) 5-3 Provide the following information and specify the key assumptions used in the shielding and source terms analysis.

The applicant submitted section 5.3.1 and 5.3.1.1 related to the configuration of the source and the shielding calculations. However, there is information either not provided by the applicant or not clear to the staff, such as:

The impurity level of Co59 in the steel cladding used for TPBAR production rods to justify the source term used in the application The irradiation conditions of the TPBARs that produced the source terms The neutron flux that the TPBARs were exposed to, and the total exposure time to produce the source term that was used in the source terms calculations.

It is also not clear to the staff how a bounding total radiation source was used with the distribution in the package for the given limit of the total number of TPBARs.

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

5-4 Provide the literature review or references used to define the existing contents in the vitrified waste.

The applicant mentioned in section 5.6.2.1 of the application that vitrified waste gamma and neutron source terms (on a per kg basis) are determined using the activity inventory in table 5.6.2-1 of the application using SCALE/ORIGEN. The listed inventories are based on literature review of existing contents. However, the staff didnt find any reference related to the activity inventory.

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

5-5 Provide information on how the self-shielding from the payload was calculated.

In section 7.6.1, the applicant stated that the Volunteer Package does not include any polymetric neutron shields. Neutron shielding is provided by the austenitic stainless steel and lead that make up the cask along with some self-shielding from the payload. The staff finds that the self-shielding from the payload is not well defined in the application.

The staff needs to verify that the homogenized mass densities are correct for normal conditions of transport and hypothetical accident conditions. Because an accurate, effective density of homogenized source terms is important in characterizing self-shielding.

This information is needed to determine compliance with 10 CFR 71.47 CHAPTER 8 OPERATING PROCEDURES 8.1 In section 8.1.3 step 3 of the SAR clarify the torque value for the lid, vent, and drain test port plugs, or acknowledge that these torque values are part of the detailed operating procedures.

While the lid, vent, and drain port plugs are not part of the containment boundary, they are important to safety components according to NUREG-6407; therefore, clarification of the torque value should be provided at least as part of the detailed operating procedures, even if that value is to hand tighten the test port plugs.

This information is necessary to determine compliance with 10 CFR 71.51(a)(1) and (2).

CHAPTER 9 ACCEPTANCE TESTS AND MAINTENANCE PROGRAMS 9.1 In sections 9.1.4 and 9.2.2.1 of the SAR provide the ANSI N14.5 test method(s) and numerical sensitivity used for the fabrication, maintenance, and periodic leakage rate tests. In section 9.2.2.1 of the SAR also describe that the maintenance and periodic leak testing is performed by personnel in accordance with section 8.5 of ANSI N14.5-2014.

The type of ANSI N14.5 test method and leak testing qualification of the personnel performing the leakage rate test are necessary to meet the ANSI N14.5 acceptance criteria, LR (leaktight), and have not been provided in the SAR.

This information is necessary to determine compliance with 10 CFR 71.51(a)(1) and (2).

9.2 In section 9.2.2.2 of the SAR, for the ANSI N14.5 pre-shipment leakage rate test, clarify the qualifications of both the personnel who will be:

a. approving the leakage rate testing procedures and

b. performing the leakage rate test.

The SAR section 9.2.2.2 pre-shipment leakage rate test description for the containment boundary metallic seals and replaced elastomeric O-rings points to the ANSI N14.5 maintenance leakage rate testing requirements (section 9.2.2.1 of the SAR) for the qualifications of the personnel who will be approving leakage rate testing procedures and performing leakage rate tests. However, it has not been provided in section 9.2.2.2 of the SAR what the qualifications are for both the personnel who will be approving the leakage rate testing procedures and performing the leakage rate test for the containment boundary elastomeric O-rings that are not replaced. The qualification of the personnel approving the leakage rate testing procedures and performing the leakage rate test is necessary to meet the ANSI N14.5 acceptance criteria, no detectable leakage when tested to a sensitivity of 110-3 ref-cm3/s.

This information is necessary to determine compliance with 10 CFR 71.51(a)(1) and (2).

9.3 Explain the reason for not providing an acceptance and maintenance thermal test in SAR chapter 9.

SAR chapter 9 does not include an acceptance and maintenance thermal test to verify that these tests confirm the heat-transfer characteristics, and thermal performance predicted in the Thermal Evaluation section of the SAR (chapter 3). An explanation for why these tests are not necessary was not included in the SAR.

This information is necessary to determine compliance with 10 CFR 71.71.