ML24281A079

Enclosure - ES-3100 Amendment Request for Additional Information

ML24281A079
Person / Time
Site:	07109315
Issue date:	10/11/2024
From:	Storage and Transportation Licensing Branch
To:
Shared Package
ML24281A077	List: ML24281A078 ML24281A079
References
EPID L-2022-LLA-0116
Download: ML24281A079 (1)

Text

Enclosure UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Request for Additional Information Docket No. 71-9315 Certificate of Compliance No. 9315 Model No. ES-3100 Package By letter dated February 5, 2024 (Agencywide Documents Access and Management System Package Accession No. ML24060A090), as supplemented on April 17, 2024 (ML24164A259),

the U.S. Department of Energy (DOE) submitted an application for revision of certificate of compliance No. 9315 to the model No. ES-3100. Among other changes, DOE proposes the addition of tri-structural isotropic (TRISO) fuel as authorized contents, and the addition of Packcrete thermal insulating and impact limiting material to the design of the package.

This request for additional information (RAI) identifies information needed by the U.S. Nuclear Regulatory Commission (NRC) staff in connection with its review of the application. The requested information is listed by chapter number and title in the applicants safety analysis report (SAR).

The NRC staff used NUREG-2216, Standard Review Plan for Transportation Packages for Spent Fuel and Radioactive Material Final Report, in its review of the application.

Each question describes information needed by the staff for it to complete its review of the application and to determine whether the applicant has demonstrated compliance with regulatory requirements.

Chapter 2 Structural Evaluation 1-1 Provide a structural evaluation of the package behavior under the normal condition of transport (NCT) and hypothetical accident condition (HAC) drop tests that considers the corresponding maximum NCT temperature specified in Table 7.3 of Design Analysis and Calculation Package No. DAC M801940-0002, Thermal Analysis of the ES-3100 Package for NCT and HAC, (ML24164A261) (with insolation and decay heat) for the impact limiting material (Packcrete / Kaolite) lower bound dynamic impact crush strength (stiffness) properties.

The package responses under the NCT and HAC load drops have been evaluated considering the upper bound (at -40°F) and the lower bound (at 100°F) stiffness properties (Volumetric strain vs. Stress curves) of the impact limiting material (i.e. Kaolite) in the SAR. The SAR Table 2.3, Summary of load combinations for normal and hypothetical accident conditions of transport, requires considering the ambient temperature at 100°F with maximum insolation and maximum decay heat to be considered as part of the initial conditions for the NCT and HAC free drop evaluation.

The applicant performed a new thermal analysis (DAC M801940-0002) to determine the temperature distribution within the package with Packcrete (and Kaolite for comparison) as the insulation material, under the steady-state conditions, NCT, and HAC. As a results of this thermal analysis, the maximum NCT quasi steady state temperatures and

their locations on the package are provided in Table 7.3 of the analysis and are incorporated in the SAR Table 3.16. Based on the information in Table 7.3, the approximate maximum NCT (through thickness average) temperatures within the insulating/impact limiting material are derived as: 190°F (on the sides), 165°F (at the bottom), and 220°F (at the top).

These temperatures are much higher than the 100°F currently considered for the lower bound stiffness properties and need to be further evaluated for impact on the lower bound stiffness properties of the impact limiting material and package behavior under the NCT and HAC drop analyses.

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

Chapter 3.

Thermal Evaluation 3-1 Clarify that pressure calculations and radiolysis calculations are based on the bounding assumption regarding whether the secondary inner containers (e.g., Teflon bottles, metal cans) are opened or closed.

Section 3.6 of the application indicated that some containment vessel arrangements (CVAs) consist of inner containers (e.g., Teflon bottle, metal can) that are either open or closed. Recognizing that calculation results would change because of differences in void volume depending on the opening or closure of the inner containers, the applicant should discuss and clarify that the pressure analyses presented in appendix 3.5.1 and appendix 3.5.2 of the application and the radiolysis analyses presented in appendix 3.5.4 for the CVAs are based on the bounding nature of the inner containers (i.e., either open or closed).

For example, it appears that the time to reach the hydrogen flammable limit (and consequences of a higher secondary container pressure) inside a closed secondary container would be shorter than the times reported in the radiolysis calculations. In addition, the basis for calculating NCT pressure (appendix 3.5.1 Table 1) and HAC pressure (appendix 3.5.2 Table 2) is to maintain a closed and pressurized secondary container (reported as a 42.779 in3 CV void volume), but there is no demonstration that the secondary container structural integrity would be maintained.

This information is needed to determine compliance with 10 CFR 71.35, and 71.43(d).

3-2 Demonstrate that the radiolysis calculations for hydrogen generation result in a transport period with adequate margin that ensures flammable gases will not exceed 5 percent by volume for both NCT and the fire test for HAC.

a.

Appendix 3.5.4 of the application provided radiolysis-related calculations for NCT, based on theory and experiments, for determining various parameters and corresponding allowable transport times. However, there were no discussions, sensitivity analyses, and test program results to demonstrate that the transport time provided in Table 1.3a of the application included a sufficient margin with the calculated values reported in appendix 3.5.4 and to address the uncertainties associated with the numerous calculation inputs and methods in order to ensure flammable gases will not exceed 5 percent vol. flammability limit.

Staff notes that, although the current application includes greater transuranic concentrations and higher decay heats that should result in a shorter transport period, the calculated time periods to reach 5 percent vol. for the hydrogen concentration in appendix 3.5.4 were longer than the time periods reported in a previously submitted SAR appendix 3.5.4 (Rev. 3).

b.

There was no discussion of the impact of the fire test for HAC on radiolysis and transport time, such as whether the fire test for HAC occurred after 1 year of transport (or the end of a certificate-limited transport time), recognizing that hydrogen generation rates for certain materials (e.g., plastics) are a function of temperature.

c.

Although section 1.2.2 of the application mentioned that transuranic radionuclides can have a concentration of 800 µg/gU for ground transport, the radiation energy inputs (i.e., used as input to subsequent radiolysis calculations) in the applications Table 3.5.4.2 of appendix 3.5.4 are based on a concentration of 40 µg/gU. There were no discussions or calculations that considered the effect of the higher transuranic quantity on hydrogen generation calculations and allowable transport period.

d.

It should be clarified that the assumption and calculation for determining the hydrogen gas generation rate by balancing with the hydrogen permeability (or diffusion) through Teflon (or metal can) is appropriate for ensuring hydrogen concentration is less than 5 percent vol. throughout the transport. For example, recognizing that hydrogen concentration build-up has a transient behavior and a corresponding time constant (which was not discussed in the application) prior to reaching steady-state, it is uncertain whether it is possible for either the bulk package interior or interior convenience containers (e.g., Teflon bottle, metal can) to reach 5 percent hydrogen concentration before the assumed balance between hydrogen generation and permeation (or diffusion) occurs. For example, a transient behavior is possible if content is loaded in a closed convenience container and then subsequently transported.

e.

Section 3.1.4.1 of the application mentioned there are 11 CVAs that represent allowable loadings (some of these CVAs are revised or new to this application).

Therefore, it should be clarified that new contents (e.g., polyethylene and carbon within TRISO fuel), other than those listed in SAR appendix 3.5.4 (i.e., CVA 1 with high-enriched uranium and CVA 2 with uranyl nitrates), do not generate flammable gases and do not affect pressure calculations.

f.

Appendix 3.5.4 of the application did not address the time period to reach 5 percent vol. in a closed convenience container, recognizing the guidance of limiting hydrogen concentrations within secondary confined vol. containers as well as the package interior.

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

3-3 Clarify that package temperatures would remain below allowable values during NCT and the fire test in HAC when multiple packages are placed within the enclosed conveyance mentioned in section 7.1.3.2 of the application.

Section 3.1.2 of the application noted that the package decay heat is 5 W (an increase from the previous 0.4 W value). Considering that section 6.1.3 of the application noted that multiple packages can be shipped together, the thermal analyses did not address the potential impact of increased package temperatures from multiple packages within an enclosed conveyance with reduced heat transfer to the ambient.

For example, although Table 3.3 of the application provided the NCT temperature of the O-ring seals based on the stand-alone thermal model assumption, the extent of the temperature margin with the O-ring allowable value is uncertain when multiple packages are positioned within a single enclosure with reduced heat transfer.

Similarly, other package-related effects may change (e.g., pressure and radiolysis effects within the containment boundary and within the closed secondary containers) due to increased package temperatures.

This information is needed to determine compliance with 10 CFR 71.35.

3-4 Provide details and discussion regarding the modeling of radiant heat transfer (e.g.,

equation, view factors) of exterior surfaces as well as internal surfaces between gaps within the package so that a review of the new thermal model can be performed for NCT and HAC.

a.

Although emissivity values of the stainless steel, silicone rubber spacers, and cat 277-4 neutron absorber were mentioned in Table 3.8 of the application and thermal calculation document No. DAC M801940-0002, there did not appear to be information about the stainless-steel absorptivity (for NCT and HAC) nor the emissivity and absorptivity values of the Kaolite and Packcrete.

b.

The brief statement in thermal calculation document section 6.6.1 in calculation document no. DAC M801940-0002 mentioned an ambient boundary condition that did not include flame properties and did not fully explain the radiant heat transfer model methodology during the fire test for HAC. Additional discussion is needed regarding the numerical modeling method and the radiant heat transfer equation (e.g., Stefan-Boltzmann) and how emissivity and absorptivity values between the package and ambient (e.g., 10 CFR 71.73 lists a 0.9 flame emissivity and 0.8 package surface absorptivity) were used in the equation.

c.

Although thermal calculation document (DAC M801940-0002) section 6.6.2 briefly discussed radiation heat transfer between gaps, the sensitivity and appropriateness of the gap dimensions (e.g., based on nominal dimensions) as well as the emissivity and absorptivity values of some internal surfaces noted above used in the calculation were not provided.

Some of the presumed above-mentioned modeled gaps would include a gap between the CV and the 277-4 neutron absorber, a gap between the 277-4 neutron absorber and the Packcrete/Kaolite, and a gap between the Packcrete/Kaolite and the drum body. In addition, it appears there also would be axial gaps between the bottom of the CV and the Packcrete/Kaolite and between the Packcrete/Kaolite and the drum.

This information is needed to determine compliance with 10 CFR 71.35.

3-5 Provide a discussion that justifies the NCT results for the ES-3100 with Packcrete refractory insulation showing an O-ring temperature of approximately 87°C, compared to nominally higher O-ring temperature for the ES-3100 with Kaolite 1600 insulation.

Table 3.8 of the application indicated that the thermal conductivity of the proposed Packcrete material is approximately one-half the thermal conductivity of the currently used Kaolite 1600 material. However, a previous application focused on the ES-3100 package with Kaolite insulation and appeared to indicate O-ring temperatures (temperatures based on 5 W decay heat values interpolated from the 0 W and 20 W decay heat temperatures) are higher for the ES-3100 package with Kaolite insulation material compared to O-ring temperatures for the ES-3100 package with Packcrete insulation material.

A clarification of the proposed thermal model is needed because it appears the models calculations indicate that a package constructed with a lower thermal conductivity material result in better heat transfer (i.e., lower package temperatures).

This information is needed to determine compliance with 10 CFR 71.35, and 71.41.

3-6 Clarify that the new thermal models have appropriate steady-state spatial resolution and temporal resolution (i.e., transient time-step sizes), and thermal model convergence values (i.e., residuals) that ensure appropriate thermal results.

The thermal discussion in the application and the calculation package did not include values associated with thermal model spatial and temporal resolutions and convergence; therefore, a complete review of thermal model performance could not be performed.

This information is needed to determine compliance with 10 CFR 71.35.

3-7 Provide document DAC-PKG-801940-A001 if it was updated for this amendment request so that a review of the model can be performed.

Section 1.2.2.7 of the application mentioned thermal calculation package document DAC-PKG-801940-A001 as a track-change. However, it was uncertain if the document was updated to support the amendment request or if the document was listed as a track-change to clarify it as an existing document of previously analyzed and reviewed thermal calculations.

This information is needed to determine compliance with 10 CFR 71.35.

Chapter 4 Containment Evaluation 4-1 Provide additional information that explains the basis and appropriateness of the test units described in the document ES-3100 Containment Vessel (CV) O-rings Life Extension Testing (RP-801580-0022 000 01) (ML24164A268).

The applicant requested a change to extend the packages periodic leakage rate testing frequency from 1 year to 2 years. The following is a list of additional O-ring life extension testing information that should be included so that a review can be performed:

a.

Provide information regarding the typical bounding operation of an ES-3100 package and its O-rings. For example, how many times in a year is a typical bounding ES-3100 package (i.e., a well-used package) used for transport and, correspondingly, how many hours does the O-ring experience the temperatures and radiation from content placed within the CV during transport and periods of storage (see item 2 below)?

b.

Provide a discussion as to how the conditions of the test units represent the environment of an O-ring based on that usage (i.e., the conditions associated with the response to the preceding question). It is noted that many of the test units were new O-rings and packages or those exposed for 1 year of usage. Therefore, they were not exposed for 2 years to the adverse synergistic effects of high temperature and radiation flux that exist when content is within the CV, and therefore, do not appear to be representative of actual units at the proposed extended period conditions.

c.

According to page 1 of the document ES-3100 Containment Vessel (CV) O-rings Life Extension Testing (RP-801580-0022 000 01), the Parker O-ring Handbook indicates an EPDM O-ring can experience 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> of use at NCT temperatures*

and be within its service life (note, it appears that the 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> does not consider the effects of radiation, which, although potentially small, may contribute to a shorter service life**). Although the ES-3100 CV is the containment boundary during transport operations, it appears that the ES-3100 CV may have a dual use that includes storage (i.e., an ES-3100 CV with its O-rings is used for RAM storage such that it is exposed to temperature and radiation from content for periods of transport and storage). Staff notes that a storage period of approximately 11/2 months amounts to 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />. The two notes below provide additional considerations.

• Note: Section 3.1.2 of the application noted that the package decay heat is 5 W, which is an increase from the 0.4 W value provided in previous ES-3100 SARs. Considering that section 6.1.3 and Table 1.3 of the application noted that multiple packages can be shipped together, the thermal analyses did not address the potential impact of increased package temperatures from 1/ the effects of multiple, neighboring packages and 2/ the effects of those multiple packages within an enclosed conveyance (per section 7.1.3.2 of the application) with reduced heat transfer to the ambient.

• • Note: Section 2.2.3 of the application indicated EPDM compounds do not undergo property changes at a cumulative dose up to 1E6 rad and section 5.4.4 of the application indicated that, based on a dose rate of 0.5 rad/hr, the cumulative dose would be less than 5000 rad for 1 year and less than 10,000 rad for 2 years. However, whereas the dose rate found in section 5.4.4 of the application was based on a single ES-3100 drum, section 6.1.3 and Table 1.3 indicated that multiple ES-3100 drums could be shipped on a single conveyance (e.g., 20, infinite). There was no discussion of the dose rate and cumulative dose to the EPDM O-rings that accounted for the dose from surrounding, multiple ES-3100 drums.

d.

Provide the reasons for the three O-ring leakage testing failures discussed in section 5 of the document ES-3100 Containment Vessel (CV) O-rings Life Extension

Testing (RP-801580-0022 000 01). In addition, there was no clear discussion as to how the three leakage testing failures entered into the decision that a 2-year periodic leakage rate testing frequency (and 2-year O-ring usage period) was acceptable.

This information is needed to determine compliance with 10 CFR 71.35, 71.41, and 71.51 4-2 Clarify the leakage rage test results (e.g., leaktight) of the ES-3100 Test Units (TU) described in section 4.2 of the application.

Section 4.2 of the application indicated that the ES-3100 design verification leakage rate testing included a leakage rate between TU-4 O-rings of 2.4773E-5 ref cm3/sec (air) and a subsequent entire TU-4 containment boundary leakage rate test result of 2E-7 cm3/sec (helium). The analysis or discussion that concludes an ANSI N14.5 leaktight designation (which is the basis for the packages operation) when part of the containment boundary has a 2.4773E-5 ref cm3/sec (air) leak rate, was not provided.

This information is needed to determine compliance with 10 CFR 71.35, and 71.41.

Chapter 6 Criticality Safety 6-1 Revise the application to clarify and justify the assumption that TRISO fuel can be bounded by Uranium Carbide (UC).

Table 6.1e,Summary of criticality evaluation for UNX crystals and unirradiated TRIGA or TRISO fuel elements provides the results of the calculation for packages containing unirradiated TRISO fuel. In each scenario, the TRISO fuel is modelled as UC.

However, it is not clear what the basis is for this assumption. Revise the application to clarify and justify the reasoning behind this assumption.

The information is needed to determine compliance with 10 CFR 71.55 and 71.59.