ML24078A372
| ML24078A372 | |
| Person / Time | |
|---|---|
| Site: | 07201052 |
| Issue date: | 04/05/2024 |
| From: | Garcia-Santos N Storage and Transportation Licensing Branch |
| To: | Bussmann D Gesellschaft fur Nuklear-Service mbH |
| Shared Package | |
| ML24078A370 | List: |
| References | |
| CAC 001028, EPID L-2021-NEW-0006 | |
| Download: ML24078A372 (18) | |
Text
OFFICIAL USE ONLY - PROPRIETARY INFORMATION
Request for Additional Information Docket No. 72-1052 Certificate of Compliance No. 1052 Amendment No. 0 Revision No. 0 Model No. CASTOR geo69 Storage System
This request identifies additional information needed by the U.S. Nuclear Regulatory Commission (NRC) staff in connection with its review of the application. The NRC staff used NUREG-2215, Standard Review Plan for Spent Fuel Dry Storage Systems and Facilities - Final Report," in its review of the application.
Each question discusses information needed by the NRC staff to complete its review of the application and to determine whether the applicant has demonstrated compliance with the regulatory requirements of 10 CFR Part 72.
STRUCTURAL EVALUATION
RAI-St-1Provide a comparison between the American Society of Mechanical Engineers (ASME) design codes used in the CASTOR geo69 design, fabrication, installation, and maintenance of components important to safety to ensure that the structural integrity of the storage system is maintained.
The package design uses the guidance in NUREG/CR-6407 (INEL-95/0551),
Classification of Transportation Packaging and Dry Spent Fuel Storage System Components According to Importance to Safety, (ML15127A114) to establish the importance to safety significance of the package components. NUREG-3854 assigns ASME design codes to the components consistent with their safety significance to the package. The methodology allows for a graded approach to package component design acceptable to the review staff.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(b).
RAI-St-2For the safety analysis report (SAR) tables 3.10-55, 3.10-56, and 3.10-57, provide cross-references to chapter 4, tables 4.3-1, 4.6-2, and 4.7-4 of the SAR.
As part of your response, demonstrate that the temperatures used in the stress analysis of the components are consistent with those from the thermal analysis.
A comparison of the temperatures listed in table 4.3-1 (normal conditions of storage (NCS) and off normal conditions), table 4.6-2 (fire condition), and figure 4.7-4 (vacuum drying condition) of the SAR indicated that the temperature considered in table 3.10-55 of the SAR (appendix 3-2) was lower than those established in the summary tables of thermal analysis in chapter 4 of the SAR. It is not clear if the information in the application is the mechanical material properties and the temperatures are used in the structural analysis in chapter 3 of the SAR used the thermal conditions identified in chapter 4 of the SAR.
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This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(b).
RAI-St-3Provide allowable accident condition temperatures for all structural components identified in table 4.3-1 in the SAR, including shielding components in the appropriate tables in chapter 3 of the SER.
The staff reviewed the tables in chapter 4, which summarize the results of the thermal analysis, indicated that for many of the components in table 4.3-1 of the SAR. The accident condition allowable temperatures are not identified in SAR table 3.10-55. This prevents capturing the influence of the calculated temperatures on the mechanical properties of the materials and thermal stresses evaluated in the structural analysis in chapter 3 of the SAR for this load condition.
This information is relevant to demonstrate that the structural integrity of the confinement boundary would be maintained.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(b).
RAI-St-4Provide reference to chapter 7s pressure analysis tables from which the design pressure values were introduced in the design under the different loading conditions (normal, off normal, and accident).
Currently, the pressure evaluation results are not incorporated into the design stress analysis to establish structural integrity under all required load conditions.
The absence of these pressure analysis tables prevents capturing the impacts of the calculated temperatures on the mechanical material properties and thermal stresses evaluated in the structural analysis in chapter 3 of the SAR for this load condition.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(b).
RAI-St-5Provide information on how gaps shown in drawing No. 1014-DD-36931, sheet 1 of 1, are treated in the Finite Element Model (FEM) and their influence on the drop analysis results.
Design drawing No. 1014-DD-36931, sheet 1 of 1, shows a [withheld per 10 CFR 2.390] gap between the canister lid and top of the fuel basket, and a
[withheld per 10 CFR 2.390] gap between the canister body and basket shielding elements (1040-DPL-36855). This information is required to assess the interaction between the canister and the fuel basket, and the ability of the fuel basket stacked grid elements to maintain their configuration during drop scenarios.
The information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236 (b).
RAI-St-6Clarify which dimension, [withheld per 10 CFR 2.390] gap, is used in the FEM which is analyzed to determine the stress and strains in the fuel basket elements.
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Document No. 1014-SR-00002, Section 5.2, indicates that the gap between the canister and the fuel basket is [withheld per 10 CFR 2.390] while design drawing No. 1014-DD-36931, sheet 1 of 1, shows a [withheld per 10 CFR 2.390] gap between the canister body and basket shielding elements (1040-DPL-36855).
The information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(b).
RAI-St-7Explain how the load in the gasket is calculated for the assembly State.
In section 3.1.2.8 of the SAR, the applicant noted that prior to the application of any external loads to the FEM, the bolting stress for the assembly State is added as bolt preloads and gasket forces (represented by gasket elements in the FEM). The staff did not find in the application an explanation for computing the bolt preloads for the gasket loads in the SAR. The staff needs an understanding of the initial State of the gasket to ensure that the performance of the gasket as a seal is maintained through the application of the external loads.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(b) and (e).
RAI-St-8Provide simulation results that demonstrate that the material models, used in the fuel basket analysis, can duplicate the results of the material test data.
In a drop test the material performance is confirmed by the drop test, the results of the drop test confirm the behavior of the material over the range of the load demand. Since the applicant has relied solely on simulation, the staff needs confirmation that the selected material models can duplicate the entire range of performance demanded of the material used to fabricate the safety components of the CASTOR geo60 storage system. This is especially true for the accumulation of strain in the computation for instability.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(b) and (c).
RAI-St-9Provide a comparison of the acceptance criteria and methodology of analysis used from KTA to those found in ASME codes in the design of components important to safety (in this case the fuel basket).
The applicant submitted the application for the CASTOR geo69 storage to be added to the list of approved storage system available for use in the U.S. under a general license. Since the storage system was submitted for use in the U.S., the staff needs a comparison between the U.S. and German and European standards used in the application.
The lack of this information will result on, significantly increasing the required regulatory review time and effort. The staff are familiar with the codes and standards as well as regulatory guidance used in the U.S., and it would be difficult to draw a comparison between the U.S. standards (or guidance) and the ones used in the application.
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This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236 (b).
RAI-St-10Provide a comparison of the results of bolt pre-loads analyzed using the guidance in NUREG/CR-6007 (UCRL-ID-110637), Stress Analysis of Closure Bolts for Shipping Casks, (ML20127N810) with those obtained using VDI 2230 and KTA 3201.2 in the SAR.
Since the applicant is seeking approval of the CASTOR geo 69 for use in the U.S., the applicant should provide information comparison and describe how they comply with U.S. regulations. Also, the staff is unfamiliar with the guidance provided in VDI 2230 and KTA 3201.2 for bolt preload computations.
NUREG/CR-6007 (UCRL-ID-110637) is used by the staff in the review of closure bolts. The information provided by the requested comparison will allow the staff to evaluate the acceptability of the computed values in meeting the requirements of the U.S. regulatory practices.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(b) and (l).
RAI-St-11 Provide an explanation of the methodology and the acceptance criteria used in the stripping analysis of the lifting bolts as per KTA 3201.2. As part of your response, provide a comparison between KTA 3201.2 and applicable U.S. codes and standards.
The applicant submitted the application for the CASTOR geo69 storage to be added to the list of approved storage system available for use in the U.S. under a general license. Since the storage system was submitted for use in the U.S., the staff needs a comparison with the U.S. codes to evaluate the application.
The stripping of the bolts threads is a viable failure mechanism under this loading condition. However, the staff is not familiar with the design methodology of KTA 3201.2. Either a parallel can be drawn to a U.S. code of practice or discussion is needed for the staff to evaluate the analysis performed and its acceptability using an U.S. code of practice.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(b) and (l).
RAI-St-12Explain the equivalence of using the VDI 2230-2 to compute the force in the trunnion connection bolts to that of a U.S. design code.
The applicant submitted the application for the CASTOR geo69 storage to be added to the list of approved storage system available for use in the U.S. under a general license. Since the storage system was submitted for use in the U.S., the staff needs a comparison with the U.S. codes to evaluate the application. For example, in this case, the reviewer would likely be guided to the use of ASME Section VIII, Division 1, Rules for Construction of Pressure Vessels, or ASME Section III, Subsection NF (Nuclear Facilities), Supports, for an acceptance criterion and the methodology in ANSI N14.6 for bolt stress analysis. This
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information is needed to demonstrate that the structural integrity of the trunnion connection bolts is consistent with the functional objectives in NUREG- 0612, Control of Heavy Loads at Nuclear Power Plants: Resolution of Generic Technical Activity A-36 (ML070250180).
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(b) and (h).
RAI-St-13Identify conditions where LS-DYNA was used in the analysis of CASTOR geo69 storage cask.
The applicant, in the SAR chapter on descriptions, notes that no handling accidents are considered as all handling operations are conducted used single-failure-proof cranes. The only dynamic condition considered in the storage cask analysis is the non-mechanistic tipover which is performed using the Electric Power Research Institute (EPRI) guidance documents. The staff needs to know which computer code was used for the analysis to determine the adequacy of the finite element properties used in the analysis.
This information is needed to demonstrate compliance with 10 CFR 72.236(b).
RAI-St-14Explain the conversion of the FA and component weight into inertial loads and its application as [withheld per 10 CFR 2.390] elements in the fuel basket FEM.
The applicant did not model the fuel basket in its entirety. The FA weights and effect of the deceleration forces are computed and applied to the FEM to capture the effect of the FA in the structural response of the fuel basket grid. A clear understanding of the representation of the inertial forces in the FEM is critical for understanding of the subsequent response analysis of the fuel basket.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(b).
MATERIALS EVALUATION
RAI-M-1Provide additional information (e.g., materials qualification data, manufacturer data sheets, etc.) about the cast iron package coatings that demonstrate coating durability and support the emissivity values credited in the thermal analysis.
The specifications and minimum requirements for the inner and outer coatings are provided in section 8.2.6.1, Surfaces of Storage Cask and Transfer Cask, of the SAR. The latter does not provide any details about materials qualification data, manufacturer data sheets or other bases that demonstrate the performance of the coating under the elevated heat and radiation exposures of the internal package environment.
The applicant states that the coating is important to safety as thermal analysis relies on emissivity values. However, it is not indicated in the bill of materials or the drawing package. The staff notes that the emissivity specification and how
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the emissivity value will be verified is important, as well as what standard the applicant is using to verify and validate these values.
In addition, Section 4.7.4 of the SAR indicated that the canister interior is filled with water vapor at low pressures (water vapor properties were provided in SAR table 4.7-3 with only density listed at 0.01 bar) during vacuum drying thermal analyses. However, there were no calculations and discussion that indicated the effective thermal conductivity of the steady-state vacuum analysis was based on the 0.01 bar water vapor properties. For example, table 4.2-4 and table 4.4.-3 of the SAR presented effective thermal properties of the fuel assembly zones assuming pure helium filling gas, which has a higher thermal conductivity than water vapor.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(b), (f), and (g).
RAI-M-2Provide additional information on the classification of undamaged versus damaged spent nuclear fuel. Alternatively, confirm and explain how the guidance in NUREG-2215, Section 8.5.15.1, Spent Fuel Classification, (ML20121A190) is used to differentiate between damaged and undamaged spent nuclear fuel.
Provide a revision to the SAR incorporating the information requested.
In section 8.4.1 of the SAR, the applicant states that the storage package relies on fuel cladding to meet fuel specific and dry storage system (DSS) related regulations. However, it does not explicitly state that the applicant is taking credit for fuel cladding in their analysis and the fuel specific as well as system related functions.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236 (b), (h), and (m).
RAI-M-3Provide additional information to demonstrate that the package drying criteria are adequate to prevent an unacceptable loss of cladding toughness due to hydride reorientation.
In section 9.1.2 Loading of Contents of the SAR, the applicant provides the process steps for the process used to remove moisture from the cask system, but is not clear why this will provide adequate drying without any adverse effects (oxidation) to the material (fuel cladding).
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(g), and (m).
RAI-M-4Justify that the [withheld per 10 CFR 2.390] fuel basket plates will have adequate fracture performance in a drop accident to maintain the assumed fuel configuration in the criticality analyses. Revise the SAR as appropriate.
The SAR does not include toughness testing requirements to verify that brittle fracture will not affect the structural integrity of the basket in a drop accident. This information is necessary to verify the adequacy of the assumptions related to the performance of the materials used to fabricate the fuel baskets, which are
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considered in the criticality analysis submitted by the applicant. This applicants analysis relies on the maintenance of configuration of the neutron absorber plates and fuel assemblies.
Although nonferrous materials are generally excluded from fracture acceptance testing in consensus standards, the proprietary [withheld per 10 CFR 2.390]
metal matrix composite is a non-code material that contains boron carbide ceramic particles that may diminish fracture performance relative to the conventional aluminum material that are considered in the ASME Boiler and Pressure Vessel Code (BPVC).
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236 (b), (c), and (g).
RAI-M-5Provide the following information:
a) an analysis to demonstrate that the package drying criteria of [withheld per 10 CFR 2.390] is adequate to remove residual moisture such that it limits hydrogen generation.
b) an explanation of the operational procedures that would prevent accumulation of hydrogen during loading operations.
c) A revised SAR incorporating the response to this question.
Section 9.1.2 of the SAR provides process steps related to removal of moisture but is unclear if this will provide adequate dryness. Additionally, in table 9.1-2, Operations for loading of contents, of the SAR it is unclear how and if hydrogen levels are monitored to ensure that flammable gas mixture is monitored and mitigated.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(h).
THERMAL EVALUATION
RAI-Th-1Explain how the effective thermal conductivity applied to the three-dimensional (3D) model baskets homogenized fuel correctly considers the appropriate amount of thermal radiation heat transfer. In addition, provide the effective thermal properties (e.g., thermal conductivity) of the fuel basket assembly during vacuum drying operations and demonstrate the appropriateness of those values.
In section 4.4.2.4.2 of the SAR, the applicant noted that radiation heat transfer among fuel rods and inner surfaces of the fuel channel, and among the fuel channel and the inner surface of the basket sheets is considered in the detailed 2D model and the simplified 2D model. However, figure 4.4-3 of the SAR showed that the half-symmetric 3D model of the canister and cask includes the following:
- i. the fuel channel,
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ii. the helium between the fuel rods and fuel channels, and
iii. the helium between the fuel channels and outer basket sheets (i.e., as part of the homogenized fuels effective thermal conductivity and explicitly modeled in the 3D ANSYS model).
This appears to indicate that radiation heat transfer within the basket is accounted for twice, which would not be an accurate or bounding assumption.
The need for accurate and bounding effective thermal properties is critical considering that some basket components are near their allowable temperature during short-term operations.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(f).
RAI-Th-2Clarify that radial gaps exist among the basket sheets along the ANSYS models basket height.
In section 4.4.2.2 of the SAR, the applicant indicated that gaps were modelled between the individual basket sheets in radial and axial directions because there is no contact among the basket sheets. Although axial gaps along the height of the ANSYS models basket were observed by staff during a visual review of the thermal model, radial gaps were only observed in the upper portion of the model.
Modeling of radial gaps is important because the radial direction is dominant for transferring the fuels decay heat outward through the basket, canister, and cask and could impact the temperatures of important-to-safety (ITS) components and their margin with allowable temperatures. For example, table 4.7-5 of the SAR appears to indicate that increased thermal resistance through the transfer cask may result in some ITS components (e.g., basket sheets) being above allowable temperatures.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(f).
RAI-Th-3Demonstrate the appropriateness of the thermal model assuming no gaps between transfer cask components. Provide a revised SAR incorporating the information requested in this question.
Although section 1.2.2.1.1of the SAR indicated the transfer cask is fabricated from a number of radial sections (e.g., outer shell, water jackets, lead), section 1.2.2.1.6 of the SAR indicated an absence of air gaps in the transfer cask body.
Likewise, a visual review by staff of the ANSYS model indicated there were no contact resistances between the radial components. However, the applicant did not demonstrate assurance that fabrication (e.g., liners, lead shield fabrication and installation) would be possible without the presence of gaps between components (e.g., inner liner and lead shielding) and the corresponding thermal contact resistance that would result in increased component temperatures. For example, table 4.7-5 of the SAR appears to indicate that increased thermal resistance through the transfer cask (i.e., presence of gaps within transfer cask) may result in some ITS components (e.g., basket sheets) being above allowable temperatures.
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This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(f).
RAI-Th-4Demonstrate that spent fuel baskets and other ITS components (e.g., canister, transfer cask) for operations within the reactor building would not be affected by temperatures greater than [withheld per 10 CFR 2.390] degrees Celsius (ºC) and without the use of air conditioning within the reactor building.
The applicant noted the following:
- i. Section 12.1.2 of the SAR mentioned that off-normal temperatures during Cask Loading Unit (CLU) handling operations in the reactor building are not credible. Moreover, section 2.2.5.1of the SAR indicated there are no off-normal environmental temperatures within the reactor building because it is assumed that the building is air conditioned. However, active cooling of the CASTOR geo69 systems heat sink (i.e., internal reactor building temperature) using air conditioning is inconsistent with regulations requiring only passive cooling.
ii. In section 12.1.2 of the SAR, the applicant assumed that off-normal temperatures during CLU handling operations in the reactor building are covered by normal temperature evaluations for the DSS. The thermal analysis of the off-normal storage condition at a [withheld per 10 CFR 2.390] ºC ambient temperature discussed in section 4.5.4 of the SAR indicated that ITS components were below allowable temperatures.
Nevertheless, the applicant has not demonstrated that the content and ITS component temperatures within the canister and transfer cask (which does not include fins) and within the bounding stacked transfer cask-transfer lock-CASTOR geo69 cask arrangement (SAR figure 1.2-9), are bounded by the finned CASTOR geo69 storage system steady-state thermal analysis. Likewise, the [withheld per 10 CFR 2.390] to begin the dewatering process would be reduced [withheld per 10 CFR 2.390] (per item i., above). In addition, table 4.7-5 of the SAR appears to indicate that a higher ambient temperature may result in some ITS components (e.g.,
basket sheets) being above allowable temperatures.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72. 236(b) and (f).
RAI-Th-5Discuss the ability of the fins to resist deformation during short-term operations, including the transferring of the storage cask that is described in section 1.2.2.4 of the SAR, and their ability to retain effectiveness over time due to the buildup of dirt and debris, recognizing that fin performance is dependent on fin condition.
The CASTOR geo69 storage systems performance is based on a finned storage system design. However, there was no discussion of the robustness of the fins to resist deformation and damage during short-term operations (e.g.,
changing from vertical and horizontal orientations). In addition, there was no sensitivity analysis of thermal performance due to damaged fins and impacts of dirt or debris buildup between fins (e.g., thermal resistance, change in emissivity
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and absorptivity) and no discussion whether there is a need for periodic operations (i.e., maintenance) to remove dirt and debris.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(b), (g), and (f).
RAI-Th-6Explain and update the various parameters used in the pressure calculations and provide pressure results associated with low burnup fuel, which has a higher fission gas release fraction than the analyzed 0.15.
The fission gas release fraction for normal, off-normal, short-term, and accident conditions (e.g., SAR tables 7.2-4, 7.3-4, 7.4-4, and 7.4-5, respectively) was based on a 0.15 value for high-burnup fuel. However, the application did not indicate that pressures based on high-burnup fuel would bound a low burnup fuel, which is assumed to have a 0.3 fission gas release fraction.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(b) and (f).
RAI-Th-7Provide, in the SAR, the minimum and maximum allowable temperatures of the vinyl-methyl-silicon rubber (VMQ) and fluorocarbon rubber (FKM) elastomeric seals during normal conditions.
Sections 1.2.1.2.2 and 8.2.5.2 of the SAR indicated that VMQ and FKM seals are used for leakage rate testing purposes. The VMQ and FKM seals maximum and minimum allowable temperatures are needed to confirm that the seals would function during test operations.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(f) and (l).
RAI-Th-8Provide, in the SAR, additional discussion and justification for the water flow rate mentioned in table 9.1-1 of the SAR.
It appears from table 9.1-1 (Operations for preparation of loading) of the SAR (step 4.2.6) that flushing water in the annulus between the canister and transfer cask is necessary for cooling purposes, but a calculation supporting the flow rate was not provided.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(f).
RAI-Th-9 Provide the following results for the CASTOR geo69 storage system ANSYS thermal models:
a) thermal energy balances (e.g., numerical residuals),
b) spatial grid generation sensitivity results for steady-state runs, and
c) time step sensitivity results of transient runs.
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Although chapter 4 of the SAR provided normal, off-normal, short-term, and accident condition results of the three-dimensional half-symmetric CASTOR geo69 storage system thermal analyses, there was no discussion that confirmed grid and timestep parameters were appropriate. In addition, the application did not include a discussion demonstrating that the thermal analyses were appropriately converged. These numerical parameters are used to determine the relevance of the numerical results described in the SAR.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(f).
RAI-Th-10Provide the justification for the maximum allowable temperatures for the containment gaskets during accident conditions, which exceed the manufacturers operating limit. As part of the response, explain any basis for short term use and update the SAR accordingly.
Section 4.0 and table 4.3-1, Temperature limits of components, of the SAR provided the maximum allowable temperatures for the metallic gaskets during accident conditions. These limits exceed the manufacturers operating temperature limit, as described in appendix 8-4, Material Qualification, Metal Gaskets, of the SAR. In addition, section 4.6.2.2 of the SAR indicated gasket temperatures greater than the reported [withheld per 10 CFR 2.390] ºC allowable temperature.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(f).
RAI-Th-11Clarify and discuss how the increased area of the fins was considered when imposing insolation boundary conditions during normal conditions and for the increased radiation heat transfer during an engulfing fire accident.
SAR section 4.4.2.3 indicated that the packages radial fins were not explicitly modeled; rather, a surface enhancement factor was applied to the heat transfer coefficient at the models corresponding unfinned surface. However, there was no discussion regarding the increased thermal input to the fins additional area from insolation during normal conditions and the increased radiation heat transfer during an engulfing fire.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(f).
CONFINEMENT EVALUATION
RAI-Co-1Provide a discussion of how radionuclide releases from the CASTOR geo69 DSS will impact the doses calculated at the owner-controlled area boundary, and how any release might affect the ability of the CASTOR geo69 DSS to meet the dose limits prescribed in 10 CFR 72.104 and 106. Add this information to chapter 7 of the SAR.
In sections 1.2.1.7, Components of the Containment System. and 2.0.2.4, Containment, of the SAR, the CASTOR geo69 DSS confinement boundaries
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(i.e., the cask and canister) are referred to as a double containment system.
The application indicates that the confinement boundaries remain leak tight for the duration of storage of spent fuel contents. The staff interprets this to mean that there is no credible leakage from either the cask or the canister. However, chapter 7 of the SAR does not specifically discuss how leakage from the CASTOR geo69 DSS confinement boundary might impact the doses calculated for the owner-controlled area boundary, nor does it discuss how the design of the confinement boundary contributes to meeting the requirements found in 10 CFR 72.104 or 72.106.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(d).
RAI-Co-2Clarify the maximum absolute pressure values for off-normal and accident conditions and provide the correct references for the filling gas temperatures cited in SAR sections 7.2.2, 7.3.2, and 7.4.3.
The pressures and fill gas temperatures cited for the off-normal and accident-fire conditions appear to be the same ([withheld per 10 CFR 2.390]) degrees Kelvin (K)), in SAR sections 7.3.2 and 7.4.3, respectively. It is not clear if this is correct.
Further, the citations for the filling gas temperatures stated in SAR sections 7.2.2, 7.3.2, and 7.4.3 include the following thermal review section citations:
sections 4.4, 4.5, and 4.6, respectively. It is not clear where the temperature values cited in the sections of chapter 7 above, appear in the sections of chapter 4 cited from the SAR. Finally, Appendix 3-1 table 3.10-4 of the SAR indicated that internal cask pressures of [withheld per 10 CFR 2.390] (fire) and [withheld per 10 CFR 2.390] (impact) were considered in structural evaluations, whereas section 7.4 of the SAR calculated larger cask pressures of [withheld per 10 CFR 2.390] (fire) and [withheld per 10 CFR 2.390] (impact) during accident conditions.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(l).
RAI-Co-3Revise the appropriate sections of the CASTOR geo69 DSS SAR to properly define the terms leak-tight and leak tight and the use of the phrases leak-tightness and leak tightness as defined in ANSI N14.5-2014 since this ANSI standard is included in the list of references for chapter 7 Containment, to chapter 10 Acceptance Criteria and Maintenance Program of the SAR.
Chapter 7 of the SAR references ANSI N14.5 - 2014, American National Standard for Radioactive Materials - Leakage Tests on Packages for Shipment, as the standard for leakage testing for the CASTOR geo69 DSS inner and outer confinement boundaries (i.e., the cask and the canister). The ANSI N14.5 -
2014 standard defines the term leaktight as follows:
The degree of package containment that, in a practical sense, precludes any significant release of radioactive materials. This degree of containment is achieved by demonstration of a leakage rate less than or equal to 1 x 10-7 refcm 3/s, of air at an upstream pressure of 1 atmosphere (atm) absolute (abs), and a downstream pressure of
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0.01 atm abs or less.
The ANSI N14.5 - 2014 standard provides the only definition of the term leaktight, as it relates to radioactive material package leakage testing, that is recognized by the NRC. Therefore, any use of the term (or similar terms such as leak-tight, leak tight, or leak tightness) must be in reference to the definition provided in the ANSI N14.5 - 2014 standard.
Sections 1.2.1.7 and 2.0.2.4 of the CASTOR geo69 DSS SAR describe that both the geo69 confinement boundaries (i.e., the cask and canister, which are referred to as a double containment system in the SAR) remain leak tight for the duration of storage of spent fuel contents. The staff understands this to mean that there is no credible leakage from either the cask or the canister; however, the terms leak-tight and leak tight should only refer, by definition, to the specific DSS components that have been demonstrated to be leaktight by leak testing performed in accordance with ANSI N14.5 and meeting the leaktight criteria found in ANSI N14.5 - 2014.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(e) and (l).
RAI-Co-4Provide additional justification for the request for the approval of a significant departure from the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) code Section III, Division 3, WC-6120, Testing of Containments, and subsequent leak testing according to WC-6224, Examination for Leakage After Application of Pressure, as indicated in table 2.0-5 of the SAR; similarly, this reliance on initial pressure test and leakage rate tests is mentioned in sections 10.1.3.1.1 and 10.1.4 of the SAR.
Table 2.0-5, List of BPVC Alternatives for DSS (on page 2.0-8 of the SAR),
provides a justification for an alternative to ASME B&PV code Section III, Division 3, WC-6120, for pressure testing of the storage cask and canister of the CASTOR geo69 DSS. The justification provided includes the following statement:
[withheld per 10 CFR 2.390]
This exception, if granted by the NRC as requested, would provide relief from the ASME code requirement for any pressure testing and subsequent leak testing of each of the CASTOR geo69 DSS storage containments in the course of serial production of both the cask and canister, based solely on the structural analysis of the CASTOR geo69 DSS presented in chapter 3 of the SAR. The alternative proposed by the applicant represents a significant departure from the ASME code requirements, one that NRC staff has not previously granted to any applicant for a storage design; therefore, the alternative requested would need additional justification in order for the staff to further evaluate the request. In addition, refer to section 7.3 and table 1 of ANSI N14.5 - 2014 that describes fabrication leakage rate testing.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(l).
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SHIELDING EVALUATION
RAI-Sh-1Justify using 8,766 hours0.00887 days <br />0.213 hours <br />0.00127 weeks <br />2.91463e-4 months <br /> (hrs.) as the bounding exposure duration for an individual at the controlled area boundary for the dose rates analysis in the CASTOR geo69.
In section 5.1 of the SAR, the applicant assumed annual doses at the storage site for an array consisting of [withheld per 10 CFR 2.390] storage casks as a function of distance, and 100 % occupancy for 8,766 hrs. However, there is no information that justify the use of 8,766 hrs. For normal conditions, a bounding exposure duration assumes that an individual is present at the controlled area boundary for 1 full year (8,760 hours0.0088 days <br />0.211 hours <br />0.00126 weeks <br />2.8918e-4 months <br />). The applicant needs to justify using an alternative exposure duration for the staff making a safety and regulatory finding.
This information is needed to determine compliance with 10 CFR 72.236(b) and (d).
OPERATIONS
RAI-Op-1Provide detail descriptions of the major specialized tools including the following:
a) The vacuum drying system,
b) leak detection system,
c) equipment for dewatering,
d) helium backfilling, and
e) bolting equipment needed to support loading, preparation for storage, and unloading operations.
The descriptions of this equipment should be in sufficient detail to provide a clear understanding of their function(s) and their performance characteristics.
Section 2.3.3.1.1 of the SAR states in part the following:
miscellaneous equipment essential for the operation, handling, and dispatch of the dry storage system (DSS) are discussed in Chapter 9. The miscellaneous equipment of the DSS includes but is not limited to load attachment devices (e.g. traverses, lifting lugs, lifting pintles), equipment for dewatering, drying, helium backfilling, bolting equipment (torque and preload controlled), temporary additional shielding and protections for sealing surfaces.
However, chapter 9 of the SAR does not include detailed descriptions of this equipment, their performance characteristics, their safety functions, and their operating procedures. The use of such equipment, whether it is classified as being important to safety or, though not important to safety, per the design bases, the equipments failure could negatively impact fulfillment of a function
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that is important to safety.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.230(a).
RAI-Op-2Provide a description of the evacuation system and the evacuation procedure that describes the operating requirements, use of suitable devices, and measures for the prevention of potential icing of the evacuation system line during evacuation of the canister and cask cavity during loading and unloading operation. Incorporate this information in the SAR.
Section 8.4.3 of the SAR states in part that,
potential icing of the evacuation system line during evacuation is considered and excluded through adequate measures and use of suitable devices. This way possible ice blockage of the canister evacuation path are prevented.
However, the SAR does not provide a description of the evacuation system nor the evacuation procedure with limiting conditions, and measures to prevent icing during evacuation of the canister during loading and unloading operations.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(f).
RAI-Op-3Revise chapter 9 of the SAR to provide the visual inspection acceptance criteria and specifications for all operational visual inspection steps outlined in tables 9.1-1, 9.1-2, 9.2-1, 9.2-2, 9.3-1, and 9.3-2 of the SAR, respectively. Further, provide clarification and additional information for the operational procedure steps in tables as outlined below:
a) Table 9.1-1, Operations for Preparation of loading
- i. in step 1.7, provide cask cleanliness and foreign material exclusion requirements and acceptance criteria; ii. in steps 1.7.4, 1.7.5, and 1.7.6, as applicable, provide the leak path and testing requirements; iii. in step 1.7.9, provide leak tightness test requirements and acceptance criteria; iv. for note 3 of step 1.7.9, provide the analysis or technical justification for not performing leak tightness test or provide the visual inspection acceptance criteria and specifications to provide reasonable assurance that the structural integrity of the preservation of the wear protection and closure plate is adequately maintained that will prevent any leakage;
- v. in steps 1.8.1, 2.1.3, 2.2.2, 2.3.2, and 4.1.7, provide additional information related to the type of crane used and its loading requirements; vi. step 2.1.6, states, Installation in lid fit. Clarify if this statement means Installation in sealing surface protection in lid fit in the canister body.
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vii. provide clarification for step 4.1.9, that states, Installation of sealing surface protection in the canister. Clarify the meaning of this statement and revise the SAR as appropriate; and viii. in step 4.2.5, change ground to bottom of.
b) Table 9.1-2, Operations for loading of contents
- i. in step 1.1.3, clarify the meaning of four-eye principle and where in the SAR this principle is described; ii. in steps 1.2.4 and 1.2.8, under the requirement column, E2.4 and E2.8 should be 1.2.4 and 1.2.8; iii. in steps 3.3.16 and 17, clarify if these steps should be reversed; and iv. in step 5, the word should be On-site, and provide detailed operational steps.
c) Table 9.2-2, Required steps for the unloading of contents via cask loading unit (CLU), in step 1.1.5, clarify the meaning of the phrase installation in lid fit means.
In tables 9.11, 9.1-2, 9.2-1, 9.2-2, 9.3-1, and 9.3-2 of the SAR, include a summary of the operating procedures applicable to the Model No. CASTOR geo69 storage system. However, the applicant did not provide information such as the acceptance criteria for visual inspections and information about other operating processes mentioned in items a) through c) of RAI-Op-3. Specifying visual inspection acceptance criteria (qualitative or quantitative) are necessary and sufficient to provide reasonable assurance that, when a visual inspection is performed and the acceptance criteria are met, then a safety-related component is considered acceptable.
The staff also needs clarification on some of the terminology used in these tables. The staff needs this information to better assess the information provided in the application.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.234(a) and 72.236(e).
RAI-Op-4Provide the nominal torquing and nominal preloading acceptance criteria or provide the section(s) in the SAR where these requirements are specified.
Revise section 9.1.2 of the SAR as part of your response.
Section 9.1.2, Loading of Contents, the SAR states the following:
each screw is installed with either a nominal tightening torque or nominal preload.
In tables 9.1-2 and 9.3-1, the SAR mentions tightening of screws (for example tightening plug and pressure nut, hexagonal screws, cap screws) with nominal torque. However, the SAR does not specify the required nominal torque for each type of screws. Specifying the requirement for nominal tightening torque or nominal preload acceptance criteria for installation of screws necessary to
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ensure the structural integrity of the preservation of the wear protection is maintained that will prevent any leakage caused by damaged screw threads.
This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.236(e).
RAI-Op-5Correct reference to the regulations cited in section 10.1 of the SAR specific to performance of all tests applicable to DSS and CLU in accordance with written and approved procedures.
There is no 10 CFR 21.162 regulations. The staff believes the correct reference should be 10 CFR 72.162, Test Control.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.162.
RAI-Op-6Revise sections 9.1, steps 1.2.9, 2.2.8, and 3.3.13, and section 9.3, step 3.10, and chapter 10.1.5 of operation procedures, and table 13.1-1 of section 13.1, Operation Controls and Limits, and technical report 1014-TR-00077, Proposed Technical Specification Basis, Revision 0, to include a known qualitative specification (a known maximum percentage of impurities) of the inert helium gas to be used during the drying process to minimize the source of potentially oxidizing impurity gases and vapors and adequately remove contaminants from the canister and cask.
Section 8.4.3 of the SAR states, in part,
that the canister cavity is then backfilled with helium as inert gas for applicable pressure and leak testing. The applied cover gas fulfils a defined quality specification that ensures a known maximum percentage of impurities and is additionally verified by sampling".
However, the NRC staff noted that the SAR does not include a defined quality specification, with respect to known maximum percentage of impurities present in the helium gas to be used in the canister and cask cavity.
NUREG 2215, Drying Adequacy, specifies that drying procedure should specify a suitable cover gas (such as helium) with a quality specification that ensures a known maximum percentage of impurities to minimize the source of potentially oxidizing impurity gases and vapors and adequately remove contaminants from the cask.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(e).
RAI-Op-7Clarify that the pitch between casks on the ISFSI pad, specified in the technical specifications, is sufficient to perform maintenance and operational activities.
Technical specification 4.1.3 specifies that the center to center spacing between each DSS is to be [withheld per 10 CFR 2.390]. Considering that the cask diameter is approximately [withheld per 10 CFR 2.390] m (per SAR table 4.4-2),
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this would indicate that the space between casks could be as small as [withheld per 10 CFR 2.390] m (approximately [withheld per 10 CFR 2.390] ft). Section 1.4 of the SAR states the required center to center spacing between neighboring storage casks (pitch) is guided by operational considerations.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.122(f).
RAI-Op-8Provide a description of the operational procedure explaining the precautions and procedural steps to prevent or mitigate the potential dispersal of fuel crud particulate material during unloading operations. Incorporate this information in chapter 9 of the SAR.
Section 9.2 of the SAR, table 9.2-1 and table 9.2-2, does not include procedural steps and precautions to prevent or mitigate the potential dispersal of fuel crud particulate materials.
NUREG-2215, Fuel Crud, specifies that procedural descriptions in the SAR should include contingencies for protection from fuel crud particulate material.
Further it specifies that unloading procedures should include an alert to operations personnel to wait until any loose particles have settled and to slowly move the fuel assemblies to minimize crud dispersion in the spent nuclear fuel pool.
This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(e).
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