Text

Enclosure 3: Final Response on Request for Additional Information, Non-Proprietary Version
	ML24313A075
Person / Time
Site:	07201052
Issue date:	10/31/2024
From:	; GNS Gesellschaft fur Nuklear-Service mbH
To:	; Office of Nuclear Material Safety and Safeguards
Shared Package
ML24313A078	List: ML24313A070; ML24313A073; ML24313A075; ML24313A076;
References
	T1213-CO-00024
	Download: ML24313A075 (1)
	v • d • e

Enclosure 3 to letter T1213-CO-00024

'82' G N s Non-Proprietary Version

~

Proprietary Information withheld per 1 OCFR 2.390 Final Response on Request for additional information dated April 5, 2024 Model No. CASTOR geo69 Docket-No.: 72-1052, EPID No. L-2021-NEW-0006 Non-Proprietary Version STRUCTURAL EVALUATION (St)

RAI-Provide a comparison between the American Society of Mechanical Engineers (ASME) design St-codes used in the CASTOR geo69 component design to those suggested in NUREG-3854.

1:

RAI-St-2:

The package design uses the guidance in NUREG-6407 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 required to demonstrate compliance with 10 CFR 72. 128(a)(3) for containment and 10 CFR 72. 128 (a)(3) for shielding, and 10 CFR 72.124(b) for criticality.

Answer:

The way in which SSCs (and also services) are classified as ITS (Class A, B or C) or not-ITS (D or " ") items is regulated at GNS as a so-called graded approach via the QM system (and orients to NUREG/CR 6407). This classification is typically made in the manufacturing parts list. However, the item classification is also relevant for the design of the transport and storage cask. Thus, within Rev. 2 of the SAR, GNS revised the design parts lists in the Appendixes 1-4 to 1-8 of Chapter 1 to not only classify, whether an item is ITS or not, but also to grade ITS items from A (failure of the item could directly result in a safety case), B (failure or malfunction of the item could indirectly result in a safety case) to C (failure or malfunction of the item is unlikely to create a safety case) or D if not-ITS, but quality relevant. Cf. penultimate column of the respective design parts list which is headlined by Cl. standing for "classification level".

As part of the relevance for the SAR, a corresponding declaration is made in Section 1.2.

For Safety Analysis Report (SAR) Table 3.10-55, Table 3.10-56, and Table 3.10-57, provide cross-references to Chapter4 SAR Table 4.3-1, Table 4.6-2, and Table 4.7-4 to establish that the temperatures used in the stress analysis of the components are consistent with those from the thermal analysis.

A comparison of the listed temperatures in SAR Table 4.3-1 (Normal Conditions of Storage (NCS) and qff normal conditions), Table 4.6-2 (fire condition), and Figure 4. 7-4 (vacuum drying condition) indicated that the temperature considered in SAR Table 3.10-55 (Appendix 3-2) was lower than those established in the summary tables of thermal analysis in SAR Chapter 4. This does not provide assurance that the mechanical material properties and the temperatures used in the structural analysis in SAR Chapter 3 used the thermal conditions identified in Chapter 4.

1 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 This information is required to demonstrate the structural integrity of the cask and canister in support of the containment safety function required by 10 CFR 72.128 (a) (3).

Answer:

Table 4.3-1 lists the temperature limits of components, i.e. the maximum admissible temperatures, for the materials of which the components are made. These are not the maximum temperatures actually present in the components.

In Rev. 2 of the SAR, the maximum temperatures in the components are given in Table 4.4-6 for normal conditions of storage and in Table 4.5-1 for off-normal conditions of storage. These temperatures are equal to or less than the design temperatures for which the structural analyses are performed in Chapter 3.

The temperatures for normal and off-normal conditions during on-site transfer are covered by the temperatures for normal and off-normal conditions of storage (see Subsection 4.7.6.2 and Table 4.7.7 in Rev. 2 of the SAR).

The accident conditions of storage tipover, seismic event, flood and tornado may occur shortly after normal or off-normal conditions. Therefore, the admissible stress criteria at the design temperatures for normal and off-normal conditions apply for the structural analyses of these accident conditions of storage.

For the fire accident condition of storage, the verification is carried out for the temperature present in this case.

All load cases in the structural analyses are re-evaluated due to new calculated temperatures (see Chapter 4 in the SAR Rev. 2) to demonstrate the robustness of the geo69 design.

It is therefore necessary to check whether the temperatures used in the structural verifications (see Table 3.3 1 in the SAR) are still covering.

Check for storage cask configuration (canister and basket situated in storage cask):

The check shows that all temperatures are still covered, except for the cask body, the closure plate and the structure sheets of the basket with very small deviations. The deviation for the cask body is 1.3 % (the value in Table 3.3 1 in the SAR 1014-SR-00002 is 150 °C and the recalculated value is 152 °C), for the closure plate 1.5 % (the value in Table 3.3 1 in the SAR 1014-SR-00002 is 130 °C and the recalculated value is 132 °C) and for the structure sheets of the basket 0.8 % (the value in Table 3.3 1 in the SAR is 245 °C and the recalculated value is 247 °C). Due to the high safety margins in the verifications of the abovenamed components the very small deviations of the temperatures are negligible.

Additional it is checked whether the max. occurring temperatures of the applied temperature fields under the fire accident are still covering for the analyzed components. The check shows that all temperatures for the analyzed components are still covered.

Check for transfer cask configuration (canister and basket situated in transfer cask):

2 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Only normal conditions of transport (NCS) are evaluated in the transfer cask configuration. The check shows that all temperatures are still covered, except for the components discussed in the following:

For the transfer cask components the deviations of the admissible stress criteria due to the recalculated temperatures are very small (see table below). The verifications of the transfer cask components are still valid because of the high safety margins (see table below).

No explicit verifications for the canister and the basket for transfer cask configuration are performed because the verifications for these components are covered by the storage cask configuration. Therefore, the check for the canister and the basket is performed covering for the storage cask configuration:

o For the canister components the deviations of the admissible stress criteria due to the recalculated temperatures are very small (see table below). The verifications of the canister components are still valid because of the high safety margins (see table below).

o For the basket only vertical loads can appear in transfer cask configuration. The verifications of the basket for vertical loads are performed with a deceleration of even though only a deceleration of -

is required, resulting in a load-side safety factor of

Additionally, high safety margins are reported as result of the verifications. The recalculated temperatures for the basket deviate max.

about +11 % (highest deviation for the outer sheets; the value in Table 3.3 1 is 210 °C and the recalculated value is 233 °C). Therefore, the deviations of temperatures are negligible small in relation to the very conservative load assumptions and high safety margins in the verifications of the basket.

In conclusion no new calculations have to be performed and all verifications are still valid taking into account the increased temperatures.

Table: Check for transfer cask components

- Only components with increased temperatures are displayed

- Under NCS Level A stress criteria are applied which are derived from Sm. Thus, no further admissible stress criteria have to be calculated 3

to letter T1213-CO-00024 RAI-St-3:

RAI-St-4:

Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Table: Check for canister components The answer is integrated in the SAR Rev. 2 in the new Section 3.10 "Delta assessments".

Provide allowable accident condition temperatures for all structural components identified in SAR Table 4.3-1, including shielding components in the appropriate Tables in Chapter 3.

A review of the Tables in Chapter 4 which summarize the results of the thermal analysis indicated that for many of the components in SAR Table 4.3-1 the accident condition allowable temperatures are not identified in SAR Table 3. 10-55. This prevents the capture of the influence of the calculated temperatures on the mechanical material properties and thermal stresses evaluated in the structural analysis in SAR Chapter 3 for this load condition.

This information is required to demonstrate the structural integrity of the cask and canister in support of the containment safety function required by 10 CFR 72. 128 (a) (3).

Answer:

The answer to RAI-St-3 can be found in the answer to RAI-St-2.

Provide reference to the Chapter 7 pressure analysis Tables from which the design pressures values are introduced in the design under the different loading conditions (normal, off normal and accident).

This will ensure that the pressure evaluation results are incorporated into the design stress analysis to establish structural integrity under all required load conditions. This prevents the ca ture of the influence of the calculated tem eratures on the mechanical material ro erties 4

to letter T1213-CO-00024 RAI-St-5:

Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 and thermal stresses evaluated in the structural analysis in SAR Chapter 3 for this load condition.

This information is required to demonstrate the structural integrity of the cask and canister in support of the containment safety function required by 10 CFR 72. 128 (a) (3).

Answer:

In chapter 7 the maximum internal absolute pressure on the canister and the maximum internal absolute pressure on the cask are given. The maximum internal absolute pressure on the cask is also the maximum external absolute pressure on the canister.

The maximum external absolute pressure on the cask and the respective minimum absolute pressure are not given but can be assumed to be generally valid or covering. The maximum external absolute pressure on the cask is the environmental pressure which is 1.4 bar or 0.14 MPa (see 10 CFR 71. 71 ). The minimum internal absolute pressure on the canister and cask are assumed covering to be 0. Therefore, the minimum external absolute pressure on the canister is also 0.

All load cases in the structural analyses are re-evaluated in Rev. 2 of the SAR due to new calculated pressures (see answer to RAI-Th-6) to demonstrate the robustness of the CASTOR geo69 design.

The internal and external pressures were recalculated due to increased fission gas release rates for LBF (see Chapter 7 in the SAR 1014-SR-00002).

It is therefore necessary to check whether the pressures used in the structural verifications (see Table 3.11 6) are still covering. The check shows that all pressures are still covered, except the max. internal pressures under fire accident for the canister.

The pressure for the canister under fire accident increases from*** (see Table 3.11 6 in the SAR 1014-SR-00002) to the recalculated value of

. According to Section 3.6.2 in the SAR 1014-SR-00002 the canister is not assessed, since the thermal analysis in chapter 4 shows, that the temperature distribution of the canister and basket equals the design temperatures and does not change during the fire period, because the fire event does not last long enough. The recalculated respectively increased pressure value of is still covered by the max. pressure for the canister covering all other conditions of (see Table 3.11 6 in the SAR 1014-SR-00002).

In conclusion no new calculations have to be performed and all verifications are still valid taking into account the increased pressures due to new fission gas release rates.

The answer is integrated in the SAR Rev. 2 in the new Section 3.10 "Delta assessments".

Design Dwg: 1014-00-36931 Sht. 1/1 show a gap between the canister lid and top of fuel basket, and a gap between the canister body and basket shielding elements (1040-DPL-36855). Provide information on how these gaps are treated in the Finite Element Model (FEM) and their influence on the drop analysis results.

This information is required to capture 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.

5 to letter T1213-C0-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 The information is required to demonstrate the structural integrity of the fuel basket in support of the criticality safety function required by 10 CFR 72. 124 (b).

Answer:

In drawing 1014-DD-36931 1/1 the nominal gaps are given, i. e. the axial gap of between basket and canister lid as well as the radial gap between basket and canister body.

The axial nominal gap between basket and canister lid considers the height of the basket:

the height of the canister:

the height of the canister bottom:

the height of the cansiter lid:

and leads to the above mentioned gap of (1014-DD-30984 1/1),

(1014-00-36855 1/4),

(1014-00-36855 1/4)

The radial nominal gap between basket and canister body considers the outer diameter of the basket:

the inner diameter of the canister:

and leads to the above mentioned gap of (1014-00-30984 1/1),

( 1014-00-36855 1 /4)

Side and vertical loads are investigated for the fuel basket.

Side loads For side drops, the gaps are considered in the analysis. The interaction between the basket and the canister body is modeled to capture the closing of the radial gap upon impact. This ensures that the forces and deformations are accurately represented, demonstrating that the basket maintains its structural integrity.

Vertical loads For vertical loads (i.e.: end drops), safety margins of at least are shown for the stacked grid elements. The high safety ensures that even without explicitly modeling the axial gap, the basket's stacked grid elements maintain their configuration and structural integrity. The high safety margin compensates for any potential influence of the gap, ensuring the structural integrity and criticality safety function is preserved.

During an end drop, the deceleration experienced by the fuel basket is -

(please see also answer to RAI-St-13). This deceleration value is used to calculate the worst-case impact scenario, ensuring that the analysis is conservative and robust.

The membrane stress in the basket's stacked grid elements is calculated to be**** This stress level is significantly lower than the allowable stress of for the stacked grids in the basket. The value represents the yield strength, which is a conservative approach 6

to letter T1213-CO-00024 RAI-St-6:

Non-Proprietary Version Proprietary Information withheld per 10CFR 2.390 to ensure safety. Furthermore, the yield strength is validated during production to ensure material consistency and reliability.

The safety margin for the stacked grid elements is calculated as follows:

1111111--

This safety margin of indicates that the actual stress experienced by the grid elements is well within the allowable limits, providing a substantial buffer to ensure structural integrity.

Conclusion For side loads, the gaps are explicitly taken into account in the analysis. The interaction between the basket and the canister body is modeled to capture the closing of the radial gap upon impact. This ensures that the forces and deformations are accurately represented, demonstrating that the basket maintains its structural integrity. By considering these gaps, the analysis provides a comprehensive understanding of the basket's behavior under side load conditions, ensuring that the structural integrity and criticality safety function are preserved even in these scenarios. The conservative approach and high safety margins further reinforce the robustness of the design.

For vertical loads, the existing analysis is sufficient to demonstrate the structural integrity of the fuel basket during drop scenarios. The robust material properties and high safety margins ensure that the basket maintains its configuration and criticality safety function as required by 10 CFR 72.124(b ). The deceleration and stress analysis further support the conclusion that the fuel basket can withstand the impact forces without compromising its structural integrity. This comprehensive approach ensures compliance with regulatory requirements and the safety of the fuel basket during all potential drop scenarios Clarify which dimension c.11111 or gap) is used in the FEM which is analyzed to determine the stress and strains in the fuel basket elements. 1014-SR-00002 Section 5.2 indicates that the gap between the canister and the fuel basket is while Design Dwg:

1014-00-36931 Sht. 1/1 shows a gap between the canister body and basket shielding elements (1040-DPL-36855).

The information is required to demonstrate the structural integrity of the fuel basket in support of the criticality safety function required by 10 CFR 72. 124 (b).

Answer:

The nominal outer diameter of the basket is (drawing 1014 DD 30984 1/1) and the nominal inner diameter of the canister body is (drawing 1014 DD 36855 1/4). This leads to the nominal gap between basket and canister body of given in drawing 1014 DD 36931 1/1.

In the structural analyses also the nominal outer diameter of the basket is considered but unlike before, the maximum inner diameter of the canister body

drawing 1014 DD 36855 2/4) is used. This leads to a larger gap of between basket and canister body.

7 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Due to the considered larger gap of between basket and canister body in the FEM, the possible deformation of the basket is larger which leads to more conservative results in the structural analyses of the basket.

RAI-Explain how the load in the gasket is computed for the assembly State. In SAR section 3.1.2.8 St-7:

it is stated 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 an explanation like that presented 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 required to demonstrate the structural integrity of the cask and canister seals in support of the containment safety function required by 10 CFR 72. 128 (a) (3).

Answer:

The gasket characteristics are given in Chapter 4 of Appendix 3-1 to 1014-SR-00002 and are summarized in the following tables for the metal gaskets to the cask lid and to the canister lid.

The behavior of the gaskets under compression and relaxation is approximated using a hysteresis curve. A hysteresis curve represents the relationship between stress and strain during a cyclic loading and unloading process. This curve shows how the gasket material behaves under load and how it recovers after the load is removed. For both gaskets the behavior is shown in the following.

8 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 9

to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 The functionality respectively the sufficient compression of the gaskets is ensured by the calculations in Table 3.10-17 for the gasket to the cask lid and in Table 3.10-20 for the gasket to the canister lid in which the respective minimum preload of the bolts at room temperature according to Table 3.10-3 is conservatively considered.

10 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 The answer is integrated in Rev. 2 of the SAR in Chapter 4 of Appendix 3-1.

RAI-Provide simulation results that demonstrate that the material models used in the fuel basket St-8:

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. This is especially true for the accumulation of strain in the computation for instability.

This information is required to demonstrate the structural integrity of the fuel basket in support of the criticality safety function required by 10 CFR 72. 124 (b).

Answer:

For the parts of the basket, we take a highly conservative approach using an elastic ideally-plastic material model with a yield criterion that is equal to Rp0,2. This methodology ensures that the basket's structural integrity is thoroughly validated. Additionally, the characteristic value Rp0,2 is validated during production to ensure material consistency and reliability. With this approach the load-bearing capacity analyses are performed for the basket (extract from Chapter 3.3.2 of SAR):

The elastic-perfectly plastic material model describes the fundamental mechanical properties of a material. It assumes that the material behaves elastically up to its yield point. Beyond this point, the material deforms plastically at a constant stress level. In the elastic region the stress is proportional to strain (Hooke's Law). The yield point is the stress at which plastic deformation begins. In the plastic region stress remains constant regardless of further strain.

Stress-strain curves provide a detailed representation of a material's response to stress, showing how it deforms both elastically and plastically. These curves typically include elastic deformation (i. e. initial linear portion of the curve), yielding (i. e. transition from elastic to plastic behavior), strain hardening (i. e. increase in stress with increasing strain beyond the yield point). The elastic-perfectly plastic model simplifies this by ignoring strain hardening and assuming a constant stress level in the plastic region.

Since the elastic-perfectly plastic ignores strain hardening and assumes a constant stress level in the plastic region (see above), plastic strains are overestimated. This leads to conservative results in the computation of instability.

11 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 In conclusion, the used approach with an elastic-perfectly plastic model is sufficiently accurate for the fuel basket analysis.

RAI-Provide a comparison of the acceptance criteria and methodology of analysis used from KT A St-9:

to those found in ASME codes in the design of components important to safety (in this case the fuel basket).

CASTO~ geo69 is to be licensed for use in the US. The regulatory review staff are familiar with the codes and standards used in the US regulatory environment and the supporting guidance documents. As a result, the staff finds it difficult to draw a ready comparison between the U.S. and German and European standards used in the application, significantly increasing the required regulatory review time and effort.

This information is required to demonstrate the structural integrity of the fuel basket in support of the criticality safety function required by 10 CFR 72. 124 (b).

Answer:

The comparability of KTA 3201.2 concerning the verification concept of the fuel basket is shown in the following by statement with regard to ASME BPVC.II1.3-2017 and ASME BPVC.III.A-2017.

The verification concept for fuel baskets is customized for the special purpose. KT A 3201.2 is used as a kind of toolbox for the classification of load cases and the evaluation of stresses and strains.

Many elements in KTA 3201.2 can also be found in ASME BPVC.II1.3-2017 WD and ASME BPVC.III.A-2017, e. g. the allowable stresses for level A events and the criterions and permissions of a load-bearing capacity analysis for level D events. The comparability of both standards is shown in detail below.

The stress limits according to KTA 3201.2 and ASME BPVC.II1.3-2017 or ASME BPVC.III.A-2017 are given in the following tables for level A events and level D events in case of an elastic analysis.

12 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 KTA 320 1.2, Section 7.7.3.4 (Table 7.7-4 and Table 7.7-5)

Design level A Design level D Pm Sm 0.7

Rmr P1 1.5

Sm Rmr Pm+ Pb or 1.5

Sm RmT P1+ Pb Pe 3

Sm Pm+ Pb+ P0 + Q or 3

Sm P1+Pb+P0 +Q Pm : General primary membrane stress due to mechanical loads P1 : Local primary membrane stress due to mechanical loads Pb : Bending stress due to mechanical loads P * : Membrane stress due to constrained thermal expansion Q : Bending stress due to constrained thermal expansion Sm : Stress reference value Rmr : Tensile strength at design temperature ASME BPVC.111.3-2017, ASME BPVC.ll1.A-2017, WD-3222 F-1331 Level A Service limits Level D Service limits pm Sm Min. { 2.4

Sm; 0.7 *Su }

PL 1.5 *Sm 1.5

Min. { 2.4

Sm; 0.7

Su }

(PmorPd+ Pb 1.5

Sm 1.5

Min. { 2.4

Sm; 0. 7

Su}

(Pm or PL ) + Pb+ Q 3

Sm Pm : Primary general membrane stress PL : Primary local membrane stress Pb : Primary bending stress Q : Secondary membrane plus bending stress Sm : Stress reference value Su= Rmr : Tensile strength at design temperature The criterions for level A are the same in KTA 3201.2 and ASME BVC.II1.3-2017. The criterions for level D differ between KTA 3201.2 and ASME BVC.III.A-2017. Since a load bearing capacity analysis with plastic calculations is performed in report 1014-TR-00078 (Appendix 3-6 to 1014-SR-00002; see below) the difference does not matter.

If the elastic analysis for level D loadings is not successful - like in report 1014-TR-00078 (Appendix 3-6 to 1014-SR-00002) -, both standards allow the alternative of a load-bearing 13 to letter T1213-CO-00024 RAI-St-10:

Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 capacity analysis with the help of plastic calculations - material behavior ideally plastic with a fictitious yield stress - to prove sufficient safety margins against the collapse load.

The criterion and yield stress which have to be considered in the load-bearing capacity analyses are the same in KTA 3201.2 and ASME BVC.ll1.A-2017, i.e.:

KTA 3201.2 The specified load sha II not exceed 90% of the lower bound collapse load using a yield stress of Min. { 2.3

Sm ; 0.7

Rmr }

ASME BPVC.ll1.A-2017 Static or equivalent static loads shall not exceed 90% of the limit analysis collapse load using a yield stress of Min. { 2.3

Sm; 0. 7

Su )

Therefore, both standards give identical criterions and permissions. The verification concept used by GNS is applicable for the mechanical design of fuel baskets.

The answer is integrated in the SAR Rev. 2 in the new Section 3.1.3 "Comparison of German and US standards".

Provide a comparison of the results of bolt pre-loads analyzed using the guidance in NUREGICR-6007 with those obtained using VOi 2230 and KTA 3201.2 in the SAR.

The staff is unfamiliar with the guidance provided in VOi 2230 and KTA 3201. 2 for bolt preload computations. NUREG-6007, "Stress Analysis of Closure Bolts for Shipping Casks," 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 US regulatory practices.

This information is required to demonstrate the structural integrity of the cask and canister in support of the containment safety function required by 10 CFR 72.128 (a) (3).

Answer:

The comparability of KTA 3201.2 concerning the determined required length of engagement is shown by the answer to RAI-St-11.

The comparability of German code VOi 2230-1 with US code NUREG-6007 concerning the computation of preloads is shown in the following either by statement or by calculation. The preloads determined by means of both codes are comparable or German code VDI 2230-1 leads to covering preloads.

Hexagon screw (item 62 and 63) to cask lid (item 55):

The bolts for the cask lid are fit for ultrasonic-based and preload assisted tightening. That is, the preload applied to the screw changes its length and can thus be determined live by measuring the runtime of the ultrasound through the screw during the tightening process. (See SAR 1014-SR-00002, Section 1.2.1.1.2.)

14 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Cap screw {item 37) to blind flange {item 89):

1) Minimum nut factor (left-hand side) and maximum nut factor (right-hand side) according to J. H. Bickford, Introduction to the Design and Behaviour of Bolted Joints, Fourth Edition, Non-Gasketed Joints, Table 7.1 (Molybdenum disulphide; MoS2)

2) Preload according to VDI 2230-1 is taken from Table 3.11-8 of Appendix 3-2 to 1014-SR-00002 Cap screw {item 37) to protection cap {item 113):

1) Minimum nut factor (left-hand side) and maximum nut factor (right-hand side) according to J. H. Bickford, Introduction to the Design and Behaviour of Bolted Joints, Fourth Edition, Non-Gasketed Joints, Table 7.1 (Molybdenum disulphide; MoS2)

2) Pre load according to VDI 2230-1 is taken from Table 3.11-9 of Appendix 3-2 to 1014-SR-00002 15 to letter T1213-CO-00024 Non-Propr-etary Version Proprietary Information withheld per 1 0CFR 2.390

1) Minimum nut factor (left-hand side) and maximum nut factor (right-hand side} according to J. H. Bickford, Introduction to the Design and Behaviour of Bolted Joints, Fourth Edition, Non-Gasketed Joints, Table 7.1 (Molybdenum disulphide; MoS2)

2) Pre load according to VOi 2230-1 is taken from Table 3.11-10 of Appendix 3-2 to 1014-SR-00002 Cap screw (item 13) to trunnion (item 12):

The cap screws of the lid side trunnions are fit for ultrasonic-based and preload assisted tightening. That is, the preload applied to the screw changes its length and can thus be determined live by measuring the runtime of the ultrasound through the screw during the tightening process. (See report 1014-SR-00002, Subsection 1.2.1.1.)

Hexagon head screw (item 60) to transfer cask lid (item 10):

1) Minimum nut factor (left-hand side) and maximum nut factor (right-hand side} according to J. H. Bickford, Introduction to the Design and Behaviour of Bolted Joints, Fourth Edition, Non-Gasketed Joints, Table 7.1 (Molybdenum disulphide; MoS2)

2) Preload according to VO i 2230-1 is taken from Table A 1 of Append ix 3-5 to 1014-SR-00002 (1015-TR-00005) 16 to letter T1213-CO-00024 RAI-St-11:

Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Hexagon head screw (item 33) to transfer lock (item 31):

1) Minimum nut factor (left-hand side) and maximum nut factor (right-hand side) according to J. H. Bickford, Introduction to the Design and Behaviour of Bolted Joints, Fourth Edition, Non-Gasketed Joints, Table 7.1 (Molybdenum disulphide; MoS2)

2) Pre load according to VDI 2230-1 is taken from Table A 3 of Appendix 3-5 to 1014-SR-00002 (1015-TR-00005)

Cap screw (item 13) to transfer cask trunnion (item 12):

The cap screws of the transfer cask trunnions are fit for ultrasonic-based and preload assisted tightening. That is, the preload applied to the screw changes its length and can thus be determined live by measuring the runtime of the ultrasound through the screw during the tightening process.

The answer is integrated in Rev. 2 of the SAR in the new chapter 3.1.3 "Comparison of German and US standards".

Provide an explanation of the methodology and the acceptance criteria used in the stripping analysis of the lifting bolts as per KTA 3201. 2.

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 required to demonstrate the structural integrity of the cask and canister in support of the containment safety function required by 10 CFR 72. 128 (a) (3).

Answer:

The comparability of KTA 3201.2 concerning the determined required length of engagement is shown in the following by calculation according to,,Machinery's Handbook" (29th Edition by E.

Oberg et al, 2012 Industrial Press New York). All verifications can also be successfully carried out by using the US technical code.

17 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Hexagon screw (item 62 and 63) to cask lid (item 55):

(Required length of engagement according to KT A 3201.2 is taken from Table 3.11-13 of Appendix 3-2 to 1014-SR-00002)

Cap screw (item 37) to blind flange (item 89):

The following calculation is done for the tensile strengths of the different strength grades of the bolt (SA-193M Grade B6: 758 MPa; SA-193M Grade B7: 862 MPa).

18 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 10CFR 2.390 (Required length of engagement according to KTA 3201.2 is taken from Table 3.11-14 of Appendix 3-2 to 1014-SR-00002)

Cap screw {item 37) to protection cap {item 113):

The following calculation is done for the tensile strengths of the different strength grades of the bolt (SA-193M Grade B6: 758 MPa; SA-193M Grade B7: 862 MPa).

19 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 (Required length of engagement according to KTA 3201.2 is taken from Table 3.11-15 of Appendix 3-2 to 1014-SR-00002)

Hexagon screw (item 9) to closure plate (item 7):

(Required length of engagement according to KTA 3201.2 is taken from Table 3.11-16 of Appendix 3-2 to 1014-SR-00002)

Thread bolt (item 6) to canister lid (item 3):

The following calculation is done for the tensile strengths of the different strength grades of the bolt (SA-540M B22 Cl. 3: 1000 MPa; SA-540M B22 Cl. 1: 1140 MPa; SA-540M B22 Cl. 2: 1070 MPa).

20 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 (Required length of engagement according to KTA 3201.2 is taken from Table 3.1 1-17 of Appendix 3-2 to 1014-SR-00002)

Cap screw (item 13) to trunnion (item 12):

21 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 (Required length of engagement according to KTA 3201.2 is taken from Table 3.11-18 of Appendix 3-2 to 1014-SR-00002)

Load attachment points to cask lid (item 55):

The following calculation is done for the tensile strengths of the different strength grades of the nut (SA-182M F316, F304, 316 or 304]: 517 MPa; SA-965M F316 or F304: 483 MPa).

(Required length of engagement according to KT A 3201.2 is taken from Table 3.11-29 of Appendix 3-2 to 1014-SR-00002) 22 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Load attachment points to canister lid {item 3):

(Required length of engagement according to KTA3201.2 is taken from Table3.11-30 of Appendix 3-2 to 1014-SR-00002) 23 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Load attachment points (item 10) to protection cover (item 2-2):

(Required length of engagement according to KTA 3201.2 is taken from Table 3.11-31 of Appendix 3-2 to 1014-SR-00002) 24 to letter T1213.:..CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Hexagon head screw (item 60) to transfer cask lid (item 10):

(Required length of engagement according to KTA 3201.2 is taken from Table A 2 of Appendix 3-5 to 1014-SR-00002) 25 to letter T1213-CO-00024 RAI-St-12:

Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Cap screw (item 13) to transfer cask trunnion (item 12):

(Required length of engagement according to KTA 3201.2 is taken from Table A 5 of Appendix 3-5 to 1014-SR-00002)

The answer is integrated in Rev. 2 of the SAR in the new chapter 3.1.3 "Comparison of German and US standards".

Show the equivalence of using the VOi 2230-2 to compute the force in the trunnion connection bolts to that of a U.S. design code.

The staff reviews designs based on the design codes provided in NUREG/CR-3854, "Fabrication Criteria for Shipping Containers." For example, in this case, the reviewer would likely be guided to the use of ASME Section VIII, Division 1, or ASME Section Ill, Subsection NF, for an acceptance criterion and the methodology in ANSI N14.6 for bolt stress analysis.

This information is required to demonstrate that the structural integrity of the trunnion connection bolts meets the requirements of 10 CFR 72. 122 (h) (5) and is consistent with the functional objectives in NUREG- 0612.

Answer:

The comparability of VDI 2230-2 concerning the determined minimum safety for trunnion bolt force is shown in the following by calculation according to,,Machine Design" (August 17, 1967).

The determined safety is greater than 1, regardless the use of German code or US code.

26 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390

1) Richard T. Berger, Machine Design, August 17, 1967, "Eccentrically Loaded Joints"

2) Bolt and trunnion have the same temperature difference and the same thermal expansion=> f th = 0 kN

3) The minimum safety for bolt force calculated by means of VOi 2230-2 is taken from table 3.11-24 of Appendix 3-2 to 1014-SR-00002 27 to letter T1213-CO-00024 RAI-St-13:

Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390

1) Richard T. Berger, Machine Design, August 17, 1967, "Eccentrically Loaded Joints"

2) Bolt and trunnion have the same temperature difference and the same thermal expansion => Fth = 0 kN

3) The minimum safety for bolt force calculated by means of VDI 2230-2 is taken from Table 3.10-4 of 1014-SR-00002 The answer is integrated in Rev. 2 of the SAR in the new chapter 3.1.3 "Comparison of German and US standards".

Identify conditions where LS-DYNA was used in the analysis of CASTOR geo69 storage cask.

The applicant, in the SAR Chapter on descriptions, states that no handling accidents are considered as all handling operations are conducted used singlefailure-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. Knowing which computer code was used for the analysis is needed to determine the appropriateness of the finite element properties used in the analysis.

This information is required to demonstrate the structural integrity of the cask and canister in support of the containment safety function required by 10 CFR 72.128 (a) (3).

28 to letter T1213-CO-00024 RAI-St-14:

Non-Proprietary Version Proprietary Information withheld per 1 0CFR 2.390 Answer:

In Chapter 10 of Appendix 3-1 to 1014-SR-00002 the covering deceleration determined according to EPRI NP-4830 and EPRI TR-108760 is:

This results in a covering static deceleration of 35 g used for non-mechanistic tipover. With this deceleration the structural analyses of the storage cask and the canister are done for ACS.

For the analysis of the CASTOR geo69 storage cask, a static calculation approach with ANSYS is used instead of LS-DYNA. This approach is considered conservative and appropriate for several reasons:

In static analyses, the maximum deceleration -

is applied as a constant load. This assumes the worst-case scenario where the peak load is sustained throughout the event. In reality, during a dynamic event, the deceleration varies over time, typically peaking and then decreasing. By using the maximum value throughout, the analysis ensures that the structure is designed to withstand the highest possible forces, providing a safety margin.

Dynamic events involve time-dependent forces and responses. In a static analysis, these time-dependent effects are not considered, which simplifies the analysis but also makes it conservative. The actual dynamic response would likely involve periods of lower stress, which are not accounted for in a static analysis. This means the structure is evaluated under more severe conditions than it would actually experience.

Damping is a mechanism that dissipates energy in a dynamic system, reducing the forces experienced by the structure. By neglecting damping in the static analysis, the analysis assumes that all the energy from the impact is transferred to the structure without any loss.

This results in higher calculated stresses and strains, ensuring that the structure is evaluated under more stringent conditions than it would face in reality.

Therefore, using a static analysis ensures that the design is robust and can handle the worst-case scenario. By using a static analysis with the maximum deceleration and ignoring time-dependent effects and damping, the analysis ensures that the storage cask and canister are designed to withstand the most severe conditions. This conservative approach provides a significant safety margin, ensuring the structural integrity of the cask and canister under all potential scenarios, thereby supporting the containment safety function required by 10 CFR 72.128(a)(3).

The answer is integrated in Chapter 10 of Appendix 3-1 in Rev. 2 of the SAR.

Explain the conversion of the FA and component weight into inertial loads and its application as LOAD BODY elements in the fuel basket FEM.

The fuel basket is not modeled 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 qrid. A clear understandinq of the representation of the inertial 29 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 forces in the FEM is critical for understanding of the subsequent response analysis of the fuel basket.

This information is required to demonstrate the structural integrity of the fuel basket in support of the criticality safety function required by 10 CFR 72. 124 (b).

Answer:

For each of the 69 positions the mass of one FA is considered in relation to the length of the section in the FEM. This mass is divided by the loaded area in the FEM and multiplied by 1 g.

This is done to get a pressure load standardized to 1 g. In the following the standardized pressure load used in the FEM is calculated:

Mass of one FA:

Minimum length of FA:

Length of section in the FEM:

Loaded area in the FEM:

Acceleration due to gravity:

Standardized pressure load:

This standardized pressure load (defined by keyword *LOAD_SEGEMENT _SET) is scaled in each analysis depending on the decceleration present (defined by keyword

DEFINE_CURVE). The scaling is unit-independent, i.e. for a deceleration_, for example, the scaling factor is I because the acceleration due to gravity (g) has already been taken into account in the calculation of the standardized pressure load:

This conservative approach ensures that the load of the fuel assemblies is transferred to the fuel basket structure, eliminating any self-support by the fuel assemblies. In this context, the FAs are considered stiffnessless. By introducing the load into the fuel basket structure, the model assumes that the fuel assemblies do not provide any structural support. Consequently, all inertial forces are directly transferred to the fuel basket structure.

30 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 MATERIALS EVALUATION (Ma)

RAI-Ma-1:

RAI-Ma-2:

Provide additional information on 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 inner and outer coatings are provided in SAR Section 8.2.6.1, which 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 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 the emissivity value will be verified is important, as well as what standard the applicant is using to verify and validate these values.

This information is needed to demonstrate compliance with 10 CFR 72.236 (b),

10 CFR 72.236 (f) and 10 CFR 72.236 (g).

Answer:

The requirements on the coatings in Rev. 2 of the SAR, Subsection 8.2.6 are supplemented with the explicit designation of two coating systems, one for the inner and another one for the outer cask surface. The proof of suitability of these coatings regarding the requirements are provided in a qualification report 1014-TR-00083 Rev. 0 Material Qualification Coatings as Appendix 8-6 to Chapter 8 in Rev. 2 of the SAR. It shall be treated as proprietary information to be withheld from public disclosure. Amongst others, it provides manufacturer data sheets, results from GNS testing and reference to literature.

Remark: The qualification report 1014-TR-00083 Rev. 0 was already also submitted with the response on the 2nd RAI in the CASTOR geo69 transport application.

Provide additional information on the classification of undamaged versus damaged spent nuclear fuel. Alternatively confirm that the guidance in NUREG-2215 Section 8. 5. 15. 1, "Spent Fuel Classification," is used to differentiate between damaged and undamaged spent nuclear fuel.

SAR Section 8.4. 1 states that the storage package relies on fuel cladding to meet fuel specific and 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 10 CFR 72.236 (h) and (m) 31 to letter T1213-CO-00024 RAI-Ma-3:

Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Answer:

The fuel cladding is credited and performs the following fuel-specific as well as system-related functions:

to maintain fuel pellets configuration, to be a primary barrier to radioactive materials release, to retain fission and fill gases, and to limit fuel release under NCT.

The hypothetical fuel reconfiguration is considered under NCS and under ACS for high burn-up fuel after 20 years of storage only (according to NUREG-2224).

The answer is integrated in Section 2.1 of Rev. 2 of the SAR.

Provide additional information to demonstrate that the package drying criteria are adequate to prevent an unacceptable loss of cladding toughness due to hydride reorientation.

SAR Section 7.1.2 provides process steps but is not clear why this will provide adequate drying without any adverse effects to the material (fuel cladding).

This information is needed to demonstrate compliance with 10 CFR 72.236(g) and 10 CFR 72.236(m).

Answer:

Short-term operations during the fuel drying operations of the CASTOR geo69 comprise amongst others fuel loading of the canister under water, dewatering, vacuum drying and helium backfilling of the canister interior.

During short-term operations, the maximum fuel cladding temperature is limited to 400 °C according to NUREG-2215 (section 8.5.15.2.4). Additionally, NUREG-2215 (section 8.5.15.2.5) includes a restriction concerning the thermal cycling of the cladding to prevent an unacceptable reduction in ductility due to hydride reorientation.

After dewatering, the cladding heats up continuously during one single phase of vacuum drying without feed-in of helium. Afterwards, the cladding cools down within one single phase of vacuum drying with feed-in of helium.

By nature of this vacuum drying process, no thermal cycling of the cladding occurs. Other operations are not associated with thermal cycling. This restriction is therefore not applicable to the CASTOR geo69 and for that reason, no corresponding restrictions for the fuel drying operations are required.

Additional explanations on the vacuum drying process are added to the description of the package operations in Subsection 9.1.2 in Rev. 2 of the SAR.

32 to letter T1213-CO-00024 RAI-Ma-4:

RAI-Ma-5:

Non-Proprietary Version Proprietary Information withheld per 10CFR 2.390 Justify that the fuel basket plates will have adequate fracture performance in a drop accident to maintain the assumed fuel configuration in the criticality analyses.

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.

The staff notes that the criticality 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 - 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 BPVC.

This information is needed to demonstrate compliance with 10 CFR 72. 236 (b) and (g).

Answer:

The qualification report for the material (1014-TR-00011 Rev. 6, Appendix 8-2 in Chapter 8 of the SAR) was revised and supplemented with a discussion regarding the fracture performance. Based on an electron microscope scanning of the fracture surface after a tensile test at -40 °C, it can be concluded that brittle fracture can be excluded for the intended application (i.e. the temperature range). Fracture toughness testing is thus not applicable.

Remark: Rev. 6 of the material qualification report 1014-TR-00011 also considers the discussion results of the clarification call on August 27th related to this topic (CASTORgeo69 transport application).

Provide analysis to demonstrate that the package drying criteria of is adequate to remove residual moisture such that it limits hydrogen generation and clarify operational procedures that would prevent accumulation of hydrogen during loading operations.

SAR Section 9. 1. 2 provides process steps but is unclear why this will provide adequate dryness and removal of moisture. Additionally in Table 9. 1-2 "Operations for loading of contents", 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 10 CFR the requirements in 10 CFR 72.236(h).

Answer:

In Rev. 2 of the SAR, Subsection 9.1.2 was adjusted as follows:

The vacuum drying process reduces the cavity pressure in stages to prevent the formation of ice. Step by step, the vacuum pressure is reduced to approximately -- The boiling temperature at that pressure is-* which is far enough away from the freezing temperature of water, thus icing of the system lines can be excluded. Subsequently, after a sufficient drying time to remove most of the Ii uid water from the cavit, the vacuum ressure is further 33 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 reduced to

a. Even if the dew point of water at this pressure is about -

icing of the system lines is negligible due to the very low residual moisture in the cavity. After a sufficient drying period, the interior is disconnected from the vacuum pump and the maximum permissible residual moisture has to be verified. The proof is considered to be provided if the ** pressure criterion can be kept stable for at least***- In accordance with NUREG-2215 [4]

(Section 8.5.15.2.3, examples of accepted methods for drying), the amount of residual water is constrained to only a few grams as shown by [5]. Thus, fuel cladding degradation due to oxidizing gases (e.g., 0 2, CO2 and CO) arising as a result of the conversion of the residual water over the operating/storage time is within an acceptable level. To the same extent, the amount of hydrogen produced is also tolerable. After successful completion of drying, the cavities are filled with the inert gas helium()

to promote heat transfer and prevent cladding degradation.

THERMAL EVALUATION (Th)

RAI-Th-1:

Explain how the effective thermal conductivity applied to the tri-dimensional (30) model basket's homogenized fuel correctly considers the appropriate amount of thermal radiation heat transfer.

SAR section 4.4.2.4.2 stated 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 accounted for in the detailed 20 model and the simplified 20 model. However, SAR figure 4.4-3 indicated that the halfsymmetric 30 model of the canister and cask includes the fuel channel, the helium between the fuel rods and fuel channels, and the helium between the fuel channels and outer basket sheets (i.e., as part of the homogenized fuel's effective thermal conductivity and explicitly modeled in the 30 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 10 CFR 72. 236 (f).

Answer:

The simplified model of a FA contains the homogenized fuel rod zone, fuel channel, helium gap and basket sheets.

As described in Subsection 4.4.2.5.2 of the SAR, in the simplified model, the fuel rods, the water rods and the gas atmosphere between the fuel rods are substituted by a homogenized zone. The homogenization is performed for the region within the fuel channel. The helium gap between the fuel channel and the basket sheets is not part of the homogenized fuel rod zone.

34 to letter T1213-CO-00024 RAI-Th-2:

RAI-Th-3:

Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Hence, the radiation in the helium gap is not accounted for twice and the radiation heat transfer is modelled correctly.

Clarify that radial gaps exist among the basket sheets along the ANSYS model's basket height.

SAR section 4.4.2.2 mentioned 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 model's basket were observed 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 fuel's decay heat outward through the basket, canister, and cask and could impact ITS component temperatures and their margin with allowable temperatures.

For example, SAR table 4. 7-5 appears to indicate that increased thermal resistance through the transfer cask (i.e., presence of gaps within transfer cask) may result in in some ITS components (e.g., basket sheets) being above allowable temperatures.

This information is needed to determine compliance with 10 CFR 72.236 (f).

Answer:

It is confirmed that the radial gaps are present in the basket sheets along the entire basket height. Figures 4.4-4 to 4.4-6 showing different enlarged detail views of the 3D FE model illustrating the gaps modelled between the FA, the fuel basket components, the canister and the cask are added in Subsection 4.4.2.3 in Rev. 2 of the SAR. Variation calculations for axial gap widths between basket sheets were performed and added into Subsection 4.4.6.3 in Rev. 2 of the SAR. A short discussion of radial gap widths and tolerances is added as well in Subsection 4.4.6.4 in Rev. 2 of the SAR.

Clarify and demonstrate the appropriateness of the thermal model assuming no gaps between transfer cask components.

Although SAR section 1. 2. 2. 1. 1 indicated the transfer cask is fabricated from a number of radial sections (e.g., outer shell, water jackets, lead), SAR section 1.2.2.1.6 indicated an absence of air gaps in the transfer cask body. Likewise, a visual review of the ANSYS model indicated there were no contact resistances between the radial components. However, there was no discussion that demonstrated 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, SAR table 4. 7-5 appears to indicate that increased thermal resistance throuqh the transfer cask (i.e., presence of 35 to letter T1213-CO-00024 RAI-Th-4:

Non-Proprietary Version Proprietary Information withheld per 10CFR 2.390 gaps within transfer cask) may result in in some ITS components (e.g., basket sheets) being above allowable temperatures.

This information is needed to determine compliance with 10 CFR 72.236 (f).

Answer:

Gaps are modelled in the transfer casks sandwich structure and considered in the recalculation of the short-term operation calculations in Section 4.7 of the SAR, Rev. 2. As described in Subsection 4.7.4.2, a 1 mm gap is modelled on either side of the lead shield of tt:ie transfer cask to model the thermal contact resistances. The modelled gap represents the presence of possible gaps which could arise between the transfer cask components and the lead shield during the fabrication of the transfer cask. This leads to the calculation of conservatively higher temperatures within the transfer cask.

Demonstrate that spent fuel baskets and other ITS components (i.e., canister, transfer cask) for operations within the reactor building would not be affected by temperatures greater than -

and without the use of air conditioning within the reactor building.

The applicant noted in section 12. 1. 2 of the SAR that off-normal temperatures during CLU handling operations in the reactor building are not credible and SAR section 2.2.5.1 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 system's heat sink (i.e., internal reactor building temperature) via air conditioning is inconsistent with regulations requiring only passive cooling.

SAR section 12. 1. 2 stated that it was assumed that off-normal temperatures during CLU handling operations in the reactor building are covered by normal temperature evaluations for the OSS. Although the thermal analysis of the off-normal storage condition at a -

ambient temperature discussed in SAR section 4.5.4 indicated that ITS components were below allowable temperatures, it was not demonstrated that the content and ITS component temperatures within the canister and transfer cask (which does not include fins) is bounded by the finned CASTOR geo69 storage system thermal analysis.

Likewise, the time limit to begin the dewatering process would be reduced if ambient temperature was raised from (per item a, above). In addition, SAR table 4. 7-5 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 10 CFR 236 (f).

36 to letter T1213-CO-00024 RAI-Th-5:

RAI-Th-6:

Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Answer:

New calculations for off-normal conditions (- for both, ambient and SNF pool water temperatures) during vacuum drying and helium backfilling were performed and incorporated in Section 4.7 of the SAR, Rev. 2. Gaps in the transfer cask (see RAI-Th-3) are considered thereby. A time limit of 105 h is established for the vacuum drying process (see Subsection 4.7.4.4) to ensure that all ITS components listed in Table 4.7-6 stay at allowable temperatures.

Discuss the ability of the fins to resist deformation during short-term operations, including the transferring of the storage cask that is described in SAR section 1.2.2.4, 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's 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 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 10 CFR 72.236 (f).

Answer:

During short-term operations incl.

on-site transfer as described in Subsection 1.2.2.4 and also during NCS, any significant damage to the fins of the cask body is not applicable, as any equipment used is optimized accordingly. The fins are not load-bearing components.

Furthermore, a decrease of the thermal performance due to dirt or debris between the fins is not to be assumed during NCS, since the cask is visually inspected periodically. In case of any deviation from the specification the surface, especially the space between the fins shall be cleaned. Therefore, an additional inspection step regarding cleanliness of the fins has been added in Tables 9.3-1 and 9.3-2 in the new Rev. 2 of the SAR. Fin cleanliness was also added in the maintenance Section 10.2.

Thus, a sensitivity analysis of thermal performance due to damaged fins and impacts of dirt or debris buildup between fins is not applicable.

Clarify and update the various parameters used in the pressure calculations so as to 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, 7.4-5) was based on a 15 %

value for high burnup fuel. However, there was no indication that pressures based on high burnup fuel would bound a low burnup fuel, which is assumed to have a 30 % fission gas release fraction.

This information is needed to determine compliance with 10 CFR 72. 236 (f).

37 to letter T1213-CO-00024 RAI-Th-7:

Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Answer:

New thermal (numerical) calculations for low burnup fuel considering an increased fraction of fission gas release (0.30) in case of fuel rod failure for normal conditions of storage, off-normal conditions, for accident fire conditions and short-term operations were performed. The results are summarized in Table 4.4.7 for NCS, Table 4.5-1 for off-normal conditions, Tables 4.6-2 and 4.6-3 for ACS fire and Tables 4.7-8 and 4.7-9 for on-site transfer in Rev. 2 of the SAR. The temperatures obtained were subsequently used for the calculation of pressure buildup.

In Rev. 2 of the SAR, Subsection 7.2.2, it is justified that high-burnup fuels result in greater fission gas amounts and canister pressures than low-burnup fuel for physical reasons which are compiled in Appendix C.5 of NUREG/CR-7203.

According to NUREG/CR-6487, a fission gas release fraction of up to 30 %

may be expected for low burn-up fuel. As no backfill of fission gases into fuel rods with higher burn-up with a fission gas release fraction of 15 % is credible, the highest amount of mobilized fission gas in the canister and/or the cask is still linked to the situation with maximum burn-up, when the maximum produced amount of fission gas per loading exists. Thus, the set of boundary conditions for pressure calculations from Tables 7.2-4, 7.3-4, 7.4-4 and 7.4-5, i.e. values for high burn-up fuel, remains bounding even though individual parameters might be exceeded for low burn-up fuel.

In addition, the pressure values that would result for low burn-up fuel with a fission gas release fraction of 30 % are also calculated and provided in Subsection 7.2.2 for NCS, Subsection 7.3-2 for off-normal conditions and Subsection 7.4-3 for ACS to quantify the impact of the argumentation above.

Provide in the SAR the minimum and maximum allowable temperatures of the and ********

elastomeric seals during normal conditions.

SAR section 1.2.1.2.2 and section 8.2.5.2 indicated that*****

seals are used for leakage rate testing purposes. The ****** 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 10 CFR 72.236 (f).

Answer:

In the new revision of the SAR, section 8.2.5.2 is modified as follows:

"All elastomeric seals used are not important to safety with regard to requirements of 10 CFR 72. They are primarily used to during package operations and to protect the cask and/or components from dirt and water penetration. They are made of

, which are suitable to the expected thermal and radiation conditions (c.f. Section 8.3). Both have excellent resistance to high temperatures (up to

) and outstanding low temperature behavior down to <

[11]. This service temperature range is maintained during the entire DSS lifetime (c.f. Chapter 4)."

38 to letter T1213-CO-00024 RAI-Th-8:

RAI-Th-9:

Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390

[11]

Parker O-Ring Handbook Catalog, Rev. 06.00 Provide additional discussion and justification for the water convection heat transfer parameter described in SAR section 4. 7 and the water flow rate mentioned in SAR table 9. 1-1.

a) Section 4. 7. 1 of the CASTO~ geo69 storage SAR indicated a water convection heat transfer coefficient for short-term operations within the pool. However, the description in Section 4. 7 appears to indicate relatively small temperature differences between components in the water pool. Buoyant heat transfer correlations between parallel walls with small temperature differences would indicate convection heat transfer coefficients less than the assumed value in the SAR. The sensitivity of temperatures (and resulting relevant time constraints) for much lower heat transfer coefficient values was not considered in the SAR's analysis.

b) It appears from SAR Table 9.1-1 (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 10 CFR 72. 236 (f).

Answer:

a) To confirm the applied heat transfer coefficient for free convection of for water in the chambers, a comparative calculation based on an appropriate Nusselt law is conducted and briefly described at the end of SAR Subsection 4.7.1. The sensitivity of transfer cask temperatures to the heat transfer coefficient of water is investigated as follows:

"Regarding the heat transfer coefficients h1 and h2, deviations of only have a minor influence on the calculated temperature difference over the water gaps of-*"

b) The flushing water in the annulus between the canister and the transfer cask fulfills no cooling purposes. It is thus not considered within the thermal evaluations.

The flushing with demineralized water ensures that the annulus remains free from radioactive contamination due to inflowing water from the SNF pool. This is described in Section 1.2.2.1.1.

No changes in the SAR are necessary.

Provide results of thermal energy balances (e.g., numerical residuals), spatial grid generation sensitivity results for steady-state runs, and time step sensitivity results of transient runs for the CASTOR geo69 storage system ANSYS thermal models.

Although SAR chapter 4 provided normal, off-normal, short-term, and accident condition results of the three-dimensional half-symmetric CASTO~ geo69 package thermal analyses, there was no discussion that confirmed grid and timestep parameters were appropriate. In addition, there was no discussion that the thermal analvses were aooropriatelv converaed. These numerical 39 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 parameters are used to determine the relevance of the numerical results described in the SAR.

This information is needed to determine compliance with 10 CFR 72. 236(().

Answer:

In Section 4.4 in Rev. 2 of the SAR, the new Subsection 4.4.5 about convergence behavior for steady-state calculations was added. Furthermore, Subsection 4.4.6.5 about mesh refinement was added in Section 4.4.

In Section 4.6 in Rev. 2 of the SAR, the new Subsection 4.6.1.3 about convergence behavior for transient calculations was added. Furthermore, Subsection 4.6.1.5.1 about time stepping was added in Section 4.6.

RAI-Th-10:

Justify in the SAR the maximum allowable temperatures for the containment gaskets during hypothetical accident conditions.

SAR section 4.0 and table 4.3-1 "Temperature limits of components" provided the maximum allowable temperatures for the metallic gaskets during hypothetical accident conditions. These limits exceed the manufacturer's operating temperature limit, as described in SAR appendix 8-4, "Material Qualification, Metal Gaskets." In addition, SAR section 4. 6. 2. 2 indicated gasket temperatures greater than the reported -

allowable temperature. Provide the justification for allowing the gaskets to exceed the manufacturer's operating limit, including any basis for short term use.

This information is needed to demonstrate compliance with 10 CFR 72.236 (f)

Answer:

The comment is correct, the material qualification for metal gaskets omits justification for the increased temperature limits applied for ACS and short-term operations.

In SAR Rev. 2 the revised material qualification report 1014-TR-00017 Rev. 2 in Appendix 8-4 considers the maximum allowable short-term temperatures

(

) for the metal gaskets in addition to the admissible service temperature range<******) for continuous operation. For justification it is referred to the Catalog HELICOFLEX Spring-energized metal seals by the manufacturer Technetics.

RAI-Th-11:

Clarify 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 engulfing fire accident conditions.

SAR section 4.4.2.3 indicated that the package's radial fins were not explicitly modeled; rather, a surface enhancement factor was applied to the heat transfer coefficient at the model's corresponding unfinned surface. However, there was no discussion regarding the increased thermal input to the fin 's additional area from insolation during normal conditions and the increased radiation heat transfer during the fire accident condition.

This information is needed to determine compliance with 10 CFR 72.236 (f).

40 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Answer:

The solar insolation applied during NCS is averaged over 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . Instead of applying an averaged solar insolation of I, I has been applied conservatively on the cylindrical cask surface which stands vertically.

The surface amplification factor for solar insolation should not be considered because not all fin surfaces participate in the heat exchange. Only the top surface of the top fin participates completely. The top surfaces of all other fins only experience solar insolation partially. The bottom surfaces of all fins experience no solar insolation. Therefore, the current numerical calculation methodology described in the report is correct and does not require changes.

The impact of increased thermal input via radiation during the fire phase is shown with the help of a variation numerical calculation in Subsection 4.6.1.5.2.

Here, the emissivity of the fire is increased from -

to 1. Additional explanations about why the surface enlargement of the fins is not considered during the fire phase are added at the end of SAR Rev. 2 Subsection 4.4.2.4.

CONFINEMENT EVALUATION (Co)

RAI-Co-1:

Provide 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 (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).

Answer:

In Subsections 7.2.1, 7.3.1 and 7.4.2 of Rev. 2 of the SAR, an editorial update was performed to state clearly that there is no significant contribution of radionuclides released from the CASTOR geo69 DSS to doses at the owner-controlled area boundary, as there is no credible leakage of radionuclides from either the canister or the cask, because these are leak-tight.

41 to letter T1213-CO-00024 RAI-Co-2 RAI-Co-3 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Clarify 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

, 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 (fire) and (impact) were considered in structural evaluations, whereas section 7. 4 of the SAR calculated larger cask pressures of (fire) and (impact) during accident conditions.

This information is needed to determine compliance with the regulatory requirements in 10 CFR 72.236(1).

Answer:

The filling gas temperature 405 K for off-normal and ACS-fire conditions are correct. And as this temperature is the only parameter of the cask pressure calculation that could potentially vary (no change of gas amount or volume in the cask), the cask absolute pressure of 500 kPa results in both cases.

For off-normal conditions, T gas is based on the calculation value "Cask filling gas - volume average" of 122 °C in Section 4.5, Table 4.5-1. For ACS-fire conditions, T9as is based on the calculation value "Cask filling gas - volume average" of 125 °C in Section 4.6, Table 4.6-3 (covering value for case without protection cover). In both cases (as for all temperatures used to provide covering pressure values), a safety margin is added to the calculation value. In these cases, the safety margin is 10 K (122°C 395 K +10 K = 405 K) for off-normal conditions and 7 K for ACS-fire conditions. In the other cases, a safety margin of approx. 5 - 10 K is applied, see new Table 7.6-5 in Rev. 2 of the SAR.

Note that the structural analysis lists overpressures, i.e. gauge pressures to the minimum ambient pressure of 25 kPa, (Appendix 3-1, Table 3.10-4) while the containment analysis in Chapter 7 lists absolute pressures. The values are consistent. The minimum ambient pressure of 25 kPa is set because of the required value for transport conditions and is covering for the value in storage conditions.

Revise 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 "leaktightness" 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 leakaae testina for the CASTOR aeo69 DSS 42 to letter T1213-CO-00024 RAI-Co-4 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 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 ref

cm 3/s of air at an upstream pressure of 1 atmosphere (atm) absolute (abs), and a downstream pressure of 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'J 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 (I).

Answer:

Both confinement boundaries of the cask and the canister, as described in Subsection 7.1.1, are leaktight in accordance with the definition given in ANSI N14.5 - 2014. Therefore, there is no credible leakage from either the cask or the canister.

In Rev. 2 of the SAR, the use of terms such as "leak tight", "leak-tight" or "leaktight" are harmonized and the term is used in accordance with the definition of the updated version of the standard, i.e. ANSI N14.5 - 2022, which is now referenced.

Provide 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 Ill, 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 Ill, Division 3, WC-6120, for pressure testinq of the storaqe cask and canister of 43 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 the CASTOR geo69 OSS. The justification provided includes the following statement:

"ft is deemed adequate and sufficient to replace pressure testing (including the subsequent LT according to WC-6224) of each individual cask and canister during series production of the CASTOR geo69 OSS by a verification by calculation (provided in Chapter 3 of this SAR) in combination with one-time pressure tests performed on the initial samples of cask and canister as a process qualification. The demanding quality assurance measures required by GNS (and in accordance with the GNS QA program) during all stages of production, i.e., in particular inspections and tests during production (e.g., destructive and non-destructive examination), as well as appropriate acceptance criteria for the tests, ensure a consistently high quality of all SSC important to safety of the CASTOR geo69 design (especially containment SSC)."

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 OSS storage containments in the course of serial production of both the "cask" and "canister", based solely on the structural analysis of the CASTOR geo69 OSS 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(/).

Answer:

The application to waive the pressure test and full-scale LT on each single cask as part of serial production is withdrawn from Rev. 2 of the SAR. Both tests will be performed regularly.

Table 2.0-5 was revised with respect to deviating from ASME B&PV Code Section Ill, Division 3, WC-6120. The corresponding line in Table 2.0-5 was removed in Rev. 2 of the SAR.

In addition, the statement of omitting full scale LT on both independent containment boundaries were removed in Chapter 2, Chapter 10, and the corresponding subsections therein.

44 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 SHIELDING EVALUATION (Sh)

RAI-Sh-1:

Justify using 8, 766 hours0.00887 days 0.213 hours 0.00127 weeks 2.91463e-4 months as the bounding exposure duration for an individual at the controlled area boundary for the dose rates analysis the GAS TOR geo69.

In Section 5. 1 of the safety analysis report, the applicant assumed annual doses at the storage site for an array consisting of 120 storage casks as a function of distance, and 100 % occupancy for 8, 766 hours0.00887 days 0.213 hours 0.00127 weeks 2.91463e-4 months . However, there is no information that justify the use of 8, 766 hours0.00887 days 0.213 hours 0.00127 weeks 2.91463e-4 months . 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 0.211 hours 0.00126 weeks 2.8918e-4 months ). The applicant needs to justify the 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) for sufficient radiation shielding to meet 10 CFR 72.104.

Answer:

For the bounding exposure, duration for an individual at the controlled area boundary a value of 8766 hours0.101 days 2.435 hours 0.0145 weeks 0.00334 months is used (Section 5.1 ).

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 0.211 hours 0.00126 weeks 2.8918e-4 months ). An excessive exposure duration of the quarter of a day (6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months ) is added to the normal exposure duration value in order to take into account a leap year, which occurs every four years.

45 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 OPERATIONS (Op)

RSI-Op-1:

Provide 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 (OSS) are discussed in Chapter 9. The miscellaneous equipment of the OSS includes but is not limited to load attachment devices (e.g. traverses, lifting lugs, lifting pint/es), equipment for dewatering, drying, helium backfilling, bolting equipment (torque and pre/oad 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 equipment's failure could negatively impact fulfillment of a function that is important to safety.

This information is needed to demonstrate compliance with the regulatory requirements in 10 CFR 72.230(a).

Answer:

In Rev. 2 of the SAR, Chapter 9 was adjusted as follows:

Schematic pictures showing the involved DSS components, and the required equipment were added in Section 9.4 for the following operational setups:

Dewatering of canister cavity Drying and helium backfilling of canister cavity Drying and helium backfilling of cask cavity LT of metal gaskets in canister lid system LT of metal qaskets in cask lid system 46 to letter T1213-CO-00024 RAI-Op-2 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 LT of elastomeric seals in wear protection LT of elastomeric seals in bottom closure plate The provided schematic setup pictures provide sufficient detail to understand the functions and characteristics of the involved equipment.

Detailed descriptions of the equipment and its technical specifications will be incorporated in the detailed written and approved procedures, which will be provided with the DSS when it is shipped to the customer.

Provide 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).

Answer:

In Rev. 2 of the SAR, Subsection 9.1.2 was adjusted as follows:

The vacuum drying process reduces the cavity pressure in stages to prevent the formation of ice. Step by step, the vacuum pressure is reduced to approximately -

-The boiling temperature at that pressure is -

which is far enough away from the freezing temperature of water, thus icing of the system lines can be excluded. Subsequently, after a sufficient drying time to remove most of the liquid water from the cavity, the vacuum pressure is further reduced to

. Even if the dew point of water at this pressure is about -

icing of the system lines is negligible due to the very low residual moisture in the cavity. After a sufficient drying period, the interior is disconnected from the vacuum pump and the maximum permissible residual moisture has to be verified. The proof is considered to be provided if the pressure criterion can be kept stable for at least

. In accordance with NUREG-2215

[4] (Section 8.5.15.2.3, examples of accepted methods for drying), the amount of residual water is constrained to only a few grams as shown by [5]. Thus, fuel cladding degradation due to oxidizing gases (e.g., 0 2, CO2 and CO) arising as a result of the conversion of the residual water over the operating/storage time is within an acceptable level. To the same extent, the amount of hydroQen 47 to letter T1213-CO-00024 RAI-Op-3 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 produced is also tolerable. After successful completion of drying, the cavities are filled with the inert gas helium (

)

to promote heat transfer and prevent cladding degradation.

Revise 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 leakpath 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."

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 qeo69 storaqe system. However, the applicant did not provide information such 48 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 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).

Answer:

Chapter 9 of the SAR (new Rev. 2) was modified as follows:

a) Table 9.1-1, "Operations for Preparation of loading"

i.

in step 1.7, qualitative cleanliness and foreign material exclusion requirements and acceptance criteria are provided (also provided in steps 2.1.1, 2.1.2, 2.1.5, 2.1.6, 2.2.3, 2.3.3, 2.4.2, 4.1.5, 4.1.8 and 4.1.9) ii.

in steps 1.7.6, and 1.7.9, the leak testing acceptance criteria is provided; for the leak path separate figures are provided in Chapter 9.4, Appendix 9-1 iii.

see ii.

iv.

Leak tightness testing of the wear protection (step 1.7.6) and of the closure plate and the sealing screws (step 1.7.9) is already performed as acceptance test during manufacturing (see Section 10.1) and during maintenance prior to transport of a previously used storage cask. Therefore, it is not required to perform these tests again when a storage cask is delivered, provided no damage of these components occurred during transport of the empty packaging.

A technical justification was added below Table 9.1-1. In addition, leak testing requirements for the wear protection and the closure plate and the sealing screws were added in Subsection 10.1.5.

v.

in Section 9.0, an additional paragraph about crane handling requirements was added vi.

step 2.1.6 means "Installation of sealing surface protection in lid fit of the cask body" and was modified accordingly vii.

step 4.1.9 means "Installation of sealing surface protection in lid fit of the canister body" and was modified accordingly viii.

in step 4.2.5, "ground" was changed to "bottom of."

b) Table 9.1-2, "Operations for loading of contents"

i.

the meaning of "four-eye principle" is not described in the qlossarv (Section 0.5) of the SAR 49 to letter T1213-CO-00024 RAI-Op-4 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 ii.

in steps 1.2.4 and 1.2.8, under the requirement column, E2.4 and E2.8 were replaced by 1.2.4 and 1.2.8; iii.

steps 3.3.16 and 3.3.17 were not reversed, the check for proper installation of the protection cap shall be performed prior to the leakage test of the corresponding metal gasket iv.

in step 5, the word was corrected to "On-site";

detailed operational steps cannot be provided for step 5, since the detailed operational procedure of an on-site transfer is necessarily site-specific and the set-up of the site is currently not known c) Table 9.2-1 "Required steps for the unloading of contents directly from the DPC", in step 1.1.5, the correct meaning is "Installation of sealing surface protection in lid fit of the cask body." The wording was changed accordingly.

In tables 9.11, 9.1-2, 9.2-1, 9.2-2, 9.3-1, and 9.3-2 of the SAR, qualitative acceptance criteria for visual inspections and acceptance criteria for LT are now provided in the requirement column. The terminology used in these tables was either modified, if required, or a corresponding entry in the glossary (Section 0.5) of the SAR was made.

In addition to the changes specified above, Section 9.1 is further adapted by changing the point at which the sealing screws with valve are mounted in the closure plate of the cask. In Rev. 1 of the SAR, it was assumed that the sealing screws with valve are already mounted when the empty packaging or storage cask is accepted. However, this assumption is inconsistent with the provided parts list 1014-DPL-30934 (Legend 201.) and the descriptions in the SAR for transport. In the new Rev. 2 of the SAR, the sealing screws (with O-Rings) are replaced by the sealing screws with valve after loading.

Provide 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 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).

50 to letter T1213-CO-00024 RAI-Op-5 RAI-Op-6 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Answer:

In Rev. 2 of the SAR, Tables 9.1-2 and 9.3-1 were adjusted as follows:

The nominal torquing or nominal preloading acceptance criteria (as applicable) are provided in the requirement column for each step where screws are mounted. The values for torque and preload provided are consistent with the values used for the structural evaluation of the bolted joints in Chapter 3 of the SAR. The applicable tolerance ranges are also provided.

Correct reference to the regulations cited in section 10. 1 of the SAR specific to performance of all tests applicable to OSS 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.

Answer:

In Rev. 2 of the SAR, Section 10.1 was adjusted as follows:

The reference was corrected to 10 CFR 72.162, "Test Control."

Revise 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 NRG 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.

NU REG 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).

51 to letter T1213-CO-00024 RAI-Op-7 RAI-Op-8 Non-Proprietary Version Proprietary Information withheld per 10CFR 2.390 Answer:

In Rev. 2 of the SAR, Chapter 9, Subsection 10.1.5 and the technical report 1014-TR-00077 are adjusted as follows:

A qualitative specification for the minimum required purity of the helium gas to be used in the canister and cask cavity is added. The required purity class of helium is

. The new Rev. 1 of technical report 1014-TR-00077 is attached to Chapter 13 of the SAR Rev. 2 (Appendix 13-1).

Clarify 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 -

or greater. Considering that the cask diameter is approximately (per SAR table 4.4-2), this would indicate that the space between casks could be as small as (approximately -.i.

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).

Answer:

In Rev. 2 of the SAR, Section 1.4 is adjusted as follows:

The required centre-to-centre spacing between neighbouring storage casks (pitch) is guided by thermal considerations in order to enable sufficient heat dissipation from the casks. In addition, the required centre-to-centre spacing ensures the accessibility of the trunnions of each cask for handling operations.

For maintenance operations to be performed during storage, casks shall be moved to a separate maintenance area to minimize the occupational exposure.

Provide 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 the 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).

52 to letter T1213-CO-00024 Non-Proprietary Version Proprietary Information withheld per 1 OCFR 2.390 Answer:

In Rev. 2 of the SAR, Section 9.2, the following paragraph including contingencies for protection from fuel crud particulate material is added:

The canister cavity may contain fuel crud or other residual material. During flooding of the loaded canister with pool water (step 2.2.3 in Table 9.2 1 and Table 9.2 2), residual material accumulated at the canister cavity bottom may be dispersed within the canister cavity and remains suspended in the water for a considerable amount of time. The unloading process thus has the potential to disperse crud into the SNF pool, thereby creating exposure and personnel contamination hazards. Operations personnel shall therefore incorporate a sufficient waiting time until any loose particles have settled within the flooded canister cavity before lowering the canister into the SNF pool.

Fuel assemblies shall be removed slowly from the canister to minimize crud dispersion in the SNF pool. Fuel crud may settle on flat surfaces of the canister and the DPC or the CLU during fuel un-loading. Surfaces suspected of carrying fuel crud should be kept under water until a preliminary dose rate scan clears the canister and the DPC or the CLU for removal. Any remaining fuel crud shall be removed within the framework of decontamination.

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ML24313A075

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