ML22006A351

Enclosure 4: Nwp'S (Applicant'S) Comments on the Summary of the Teleconference Dated December 1, 2021 Related to Shielding RAIs (Acceptance Tests), Model Nos. TRUPACT-II and Halfpact Packages

ML22006A351
Person / Time
Site:	07109218, 07109279
Issue date:	12/27/2021
From:	Stephen Burns Nuclear Waste Partnership
To:	Garcia-Santos N, William Allen, John Wise Office of Nuclear Material Safety and Safeguards
Garcia-Santos N
Shared Package
ML22006A350	List: ML22006A351 ML22006A352 ML22006A353 ML22006A354 ML22006A355 ML22006A356 ML22091A162 ML22091A163
References
0CAC 01029, EPID L-2021-LLA-0033, EPID L-2021-LLA-0034
Download: ML22006A351 (3)

Text

Attendees:

Nuclear Waste Partners LLC (NWP LLC or NWP):

Todd Sellmer, Manager, Packaging and Information Systems Scott Burns, Packaging Engineer, Project Manager Steve Porter, Primary Shielding Reviewer U.S. DOE (DOE):

DaBrisha Smith, Package Certification Specialist U.S. Nuclear Regulatory Commission (NRC):

Norma García Santos, Project Manager William Allen, Shielding Reviewer Omar Khan, Materials Reviewer John Wise, Senior Materials Reviewer Aaron Thomilson, Inspector (Quality Assurance, Operations, and Acceptance Tests)

SUBJECT:

12/1/21-Conference Call with Nuclear Waste Partners LLC and the U.S.

Department of Energy-Discuss Follow up Questions Related to Shielding RAIs RAI-Sh-5 and -8, Model Nos. TRUPACT-II and HalfPACT (Docket Nos. 71-9218 and 71-9279; EPID L-2021-LLA-0033 and L-2021-LLA-0034, respectively)

On December 1st, 2021, NRC, NWP, and DOE/CBFO participated on a phone call to discuss the follow up questions to the responses to requests for additional information (RAI) related to the shielding evaluation for revisions of the certificates of compliance of Model Nos. TRUPACT-II and HalfPACT packages. The staff sent the following clarification questions:

1. Is the lead thickness in the packages drawings used as the standard to determine the reject rate for the minimum lead thicknesses?

Shielded Container Minimum Cavity Width Minimum Lead Thickness SC-30G1 0.94 in. 0.88 in.

SC-30G2 1.40 in. 1.31 in.

SC-30G3 2.75 in. 2.57 in.

SC-55G2 1.98 in. 1.86 in.

2. Is the standard used to determine the reject rate not stepped configured (i.e., the configuration seen in the figure below adjacent to the arrow and the D), but a simple lead plate sandwiched between two stainless steel plates (i.e., the configuration seen in the figure 7-23 farthest from the arrow and the D)? (this question is related to Figure 7-23, Regulatory Hypothetical Accident Condition Type B Testing for the HalfPACT Shielded Container Payloads.

3. The applicant noted the following:

the radioisotope (source) is placed at a distance equal to the source to survey instrument distance representative of the SCA to be gamma scanned.

a) Is the source placed in the center of the shielded container cavity or next to the cavity wall?

Enclosure 2 4

a)b) If it is placed next to the cavity wall, does the source move in tandem with the detector shown in Figure 6-47, Regulatory Hypothetical Accident Condition Type B Testing for the HalfPACT Shielded Container Payload?

The document enclosed to this summary includes the responses from the applicant to these questions. This document summarizes the discussions between the staff and the applicant.

In terms of question No. 3, the staff asked how the source is located during the scan. The applicant explained that, during the scan of the lead shield, there is a test port and a detector at the center of the of the lid. The source and the detector move together up and down the internal wall of the shielded canister. During production of the package, the lid is modified and built to the same thickness as the one used during testing.a test lid with a hole in the center is used.

The hole in the center of the lid allows for the source to be inserted into the cavity of the shielded container while the detector is located outside of the cavity. The source and detector move together up and down the wall of the shielded container. During production of the shielded containers, the test lid for gamma scans will be built to the same thickness and general configuration as the production lids, but will have a center penetration to allow for the source to be inserted into the cavity for gamma scan testing.

The prototypes used a 1-inch top plate during gamma scan testing. The applicant notes that the this did not cause issues with the SC-30G2 canister. For the bigger canisters (SC-30G3 and SC-55G2), the applicant added a step tolead plates matching the inner cavity diameter to mimic the production lid. Also, during testing, yellow blankets and bags of lead shot are placed on top of the link lead serving as additional shielding during gamma scan testing. The applicant also measured the anulusannulus after the drop tests (see Table 7-2 of the report).

In terms of question No. 2, the staff asked how far the gamma scans source is from the center of the shielded container is. The applicant noted the following:

1. The source is located at the same distance as during production of the container.

2. The calibration standard used to calibrate the gamma scan mimics the cross -section of the shielded container, but using minimum material conditions (i.e., thicknesses).

3. During the scan test, there was no lead on top of the shielded container. Norma, we are not sure what is intended by #3. Is this referring to the point discussed that there was no lead associated with the test lid used for the SC-30G2 containers? Or is this referring to the gap observed in the end of the lead annulus? If the intention for this item is the later, a separate clarification is included for reference (attached).

Figure 7-2334, provided in revision 1 of the reportHPT-REP-0001, shows a 0.318-inch gap with no lead on the cross section of the shielded container tested. In this case, the shielded containers passed the gamma scan test, but there was an abnormal reading and the applicant decided to disassemble it to investigate the cause of the abnormal reading. The applicant pointed out that they cut multiple cross sections of the shielded canister that had an abnormal reading. This gap was formed after drop testing (note the contour matching the steel) due to the presence of a pre-existing gap that formed due to a cold shut on the other end of the annulus during lead pour. The results of the gamma scan performed after drop testing raised concern at

the ends of the annulus. The sections chosen for the post-test destructive disassembly were based on the gamma scan result comparisons between the pre-drop testing and post-drop testing gamma scans (Figure 7.30). Multiple cross sections of the shielded containers were cut where the gamma scan result comparisons warranted investigation.

Figure 7-23, provided in revision 1 of HPT-REP-0001, actually shows a cold shut with no lead on the cross- section of the shielded container tested. It is located such that the geometry of the base precludes a direct shine path resulting from the gap.

The gap shown in Figure 7-34 shows the location of the gap buried on the lidis located such that the geometry of the lid precludes a direct shine path resulting from the gap. Supplemental analyses showed a minimal increase in dose rate. The applicant noted that they added a section in the shielding chapter to address axial gaps. The staff pointed out that the applicant should ensure that there are no gaps on the packages lead shield during construction, since the gamma scan may not detect those gaps.

The applicant explained that they performed an analysis of the lead shield assuming a 1/2-inch gap and the package should not exceed 200 mrem prior to shipment (see Section 7.1.4). The staff noted that he performed a hand calculation assuming a 1/2-inch gap resulting on a dose increase. The applicant pointed out that the increase in dose rate is captured in the 10% margin on the radioactivity limit. The staff pointed out that the 10% margin was initially used to address source redistribution and source intensity. Therefore, the applicant needs to justify the applicability of crediting the use of the 10% margin for calculating the dose related to a gap in the lead shield.

The applicant mentioned that they are working on refining the process of using the gamma scan. The applicant commented that refining the process should ensure that the lead shield meets the minimum measurements in the packages drawings during fabrication.

The table provided in question 1, includes the minimum cavity width and the minimum thickness of the lead shield and steel shells. The applicant pointed out the following:

1. The gamma scan is set at a minimum cavity width. Norma, we are not sure what is intended by #1. After the reject rate is determined using the calibration standard described items in 2, 3, and 4 below, the source is inserted into the cavity through the center hole in the test lid while the detector remains outside of the cavity. The source and detector move up and down over the length of the cavity while the distance (and elevation) between them are fixed.

2. The calibration standard is made of steel-lead-steel.

3. The calibration standard mimics the minimum width of the shielded container lead annulus and thickness of the steel shells.

4. The minimum thickness of the lead shield is used as to determine the reject rate during the gamma scan process.

The staff will contact the applicant if there are any additional questions about the RAI responses.