ML24075A118

4. Preliminary Safety Evaluation Report for CoC 1031 Amendment 13

ML24075A118
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Site:	07201031
Issue date:	06/18/2024
From:	Storage and Transportation Licensing Branch
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FINAL SAFETY EVALUATION REPORT DOCKET NO. 72-1031 NAC INTERNATIONAL, INC.

MAGNASTOR STORAGE SYSTEM CERTIFICATE OF COMPLIANCE NO. 1031 AMENDMENT NO. 13 Summary This safety evaluation report (SER) documents the U.S. Nuclear Regulatory Commission (NRC) staffs review and evaluation of the request to amend Certificate of Compliance (CoC) No. 1031 to NAC International, Incs (NAC, or the applicant) MAGNASTOR storage system. By letter dated July 13, 2022 (Agencywide Documents Access and Management System (ADAMS)

Accession No. ML22194A908), as supplemented on October 13, 2022, November 30, 2022, June 27, 2023, August 17, 2023, and September 15, 2023 (ADAMS Accession Nos.

ML22287A038, ML22321A269, ML23178A225, ML23229A481, and ML23258A233, respectively), NAC submitted an application in accordance with Title 10 of the Code of Federal Regulations Part 72 to amend CoC No. 1031 for the Model No. MAGNASTOR storage system to add the remaining fuel bearing material (FBM) from the Three Mile Island Unit 2 (TMI-2) reactor that experienced the March 28, 1979, reactor accident. The applicant proposes to:

add a new type of radioactive contents, FBM from the damaged Three Mile Island Unit 2 (TMI-2) reactor, to be stored inside the MAGNASTOR transportable storage canister (TSC);

add a new design configuration of the TSC (the FBM TSC) to accommodate the FBM and the new TSC internal components which includes:

reducing closure lid assembly thickness of the FBM TSC and remove the hydrostatic pressure test, adding a new waste basket liner (WBL) (based on the Greater Than Class C Waste WBL) made from stainless steel in lieu of the fuel basket, for the storage of FBM inside the FBM TSC, adding a new debris material container to be used as an operational device to handle and house finer debris; and adding a new segmented tube assembly to define cells for loading, and include concrete with a compressive strength of 6,000 psi vs. 8,000 psi for TMI-2 when using CC6.

The amended CoC, when codified through rulemaking, will be denoted as Amendment No. 13 to CoC No. 1031. This SER documents the staffs review and evaluation of the proposed amendment. The NRC staff reviewed the amendment request using guidance in NUREG-2215, Standard Review Plan for Spent Fuel Dry Storage Systems and Facilities - Final Report, dated April 2020.

For the reasons stated below and based on the statements and representations in NACs application, as supplemented, and the conditions specified in the CoC and the technical specifications, the staff concludes that the requested changes meet the requirements of Title 10 of the Code of Federal Regulations (10 CFR) Part 72, Licensing Requirements for the Independent Storage of Spent Nuclear Fuel, High-Level Radioactive Waste, and Reactor-Related Greater Than Class C Waste.

2 Chapter 1 GENERAL INFORMATION EVALUATION The objective of the review of this chapter is to evaluate design changes made to the MAGNASTOR storage system to ensure that NAC provided a description that is adequate to familiarize reviewers and other interested parties with the pertinent features of the system, including the requested changes.

1.1 General Description and Operational Features The MAGNASTOR system is a spent fuel, dry storage system consisting of a storage overpack containing a welded, stainless-steel TSC, which contains the spent fuel, and a transfer cask. In the storage configuration, the TSC is placed in the central cavity of the storage overpack. The storage overpack provides structural protection, radiation shielding, and internal airflow paths that remove the decay heat from the TSC surface by natural air circulation. The storage overpack also provides protection during storage for the TSC and the spent fuel it contains against adverse environmental conditions. The MAGNASTOR system is designed to accommodate storage of up to 37 pressurized-water reactor (PWR) fuel assemblies or 89 Boiling Water Reactor (BWR) fuel assemblies.

The transfer cask is used to move the TSC between the workstations during TSC loading and preparation activities, and to transfer the TSC to or from the overpack. There are two approved designs for the transfer cask, the standard MAGNASTOR transfer cask (MTC) and the passive MAGNASTOR transfer cask (PMTC). The MTC provides shielding during TSC movements between workstations, the overpack, or the transport cask. It is a multiwall (carbon steel/lead/NS-4-FR/steel) design with retractable (hydraulically operated) bottom shield doors that are used during loading and unloading operations. A variant of the MTC is introduced called the MTC2. The only difference from the MTC is that the MTC2 has stainless-steel walls.

1.1.1 Transportable Storage Canister In this amendment, NAC proposes to add a new design configuration of the TSC (the FBM TSC) to accommodate the FBM and the new TSC internal components. The FBM TSC is closed by an 5-inch thick solid stainless-steel closure lid, which is welded to the shell. The shell and bottom plate are the same as the other four TSCs. The shell is constructed of 0.5-inch thick stainless-steel and with a 72 inch diameter. The bottom plate is constructed of 2.75-inch-thick stainless-steel plate welded onto the shell.

1.1.2 Waste Basket Liner A WBL is proposed to replace the fuel basket structure for storage of FBM. The application states that the FBM may be loaded loose into the WBL, or it may be placed within other internal stainless steel structures that are, in turn, loaded into the WBL. These optional WBL internal components are the segmented tube assembly (STA) and the debris material container (DMC).

The application states that these components, which are also referred to as dunnage, are used to facilitate handling and placement of the FBM inside the WBL, but they are not credited in the safety analyses for demonstrating adequate functional performance of ITS structures, systems, and components.

3 1.2 Drawings In support of this application, NAC submitted the following 9 drawings for NRC review:

Drawing No. 71160-L201, Revision 0P* - Debris Material Container (DMC) Assembly, MAGNASTOR Drawing No. 71160-L205, Revision 0P* - Segmented Tube Assembly, MAGNASTOR Drawing No. 71160-L211, Revision 0P* - FBM Waste Basket Liner, MAGNASTOR Drawing No. 71160-L278, Revision 0P* - Closure Lid Assembly, FBM TSC, MAGNASTOR Drawing No. 71160-L281, Revision 0P* - Shell Weldment FBM TSC, MAGNASTOR Drawing No. 71160-L285, Revision 0P* - FBM TSC Assembly, MAGNASTOR Drawing No. 71160-L286, Revision 0P* - FBM TSC Segmented Assembly, MAGNASTOR Drawing No. 71160-662, Revision 1P* - Reinforcing Bar and Concrete Placement, Concrete Cask, MAGNASTOR Drawing No. 71160-690, Revision 1P* - Loaded Concrete Cask Assembly, MAGNASTOR 1.3 Contents NAC proposes to add FBM from the damaged Three Mile Island Unit 2 reactor as new contents to be stored inside the TSC. NAC also added a new WBL (based on the GTCC WBL) made from stainless steel in lieu of the fuel basket, for the storage of FBM inside the TSC.

1.4 Evaluation Findings

Based on the NRC staff's review of information provided by the applicant for amendment no. 13 to the MAGNASTOR system, the staff determined the following:

F1.1 A general description and discussion of Amendment No. 13 to MAGNASTOR system is presented in chapter 1 of the associated final safety analysis report (FSAR), with special attention to design and operating characteristics, unusual or novel design features, and principal safety considerations, and the description is sufficient to familiarize a reviewer or stakeholder with the design.

F1.2 Drawings for structures, systems, and components (SSCs) important to safety presented in section 1.8 of the FSAR were reviewed. Details of specific SSCs are evaluated in sections 3 through 17 of this SER.

F1.3 The specifications for the FBM to be stored in the MAGNASTOR cask are sufficient to familiarize a reviewer or stakeholder with the contents to be stored. Additional details concerning these specifications are presented in SAR Section 2.2.3.

Chapter 2 SITE CHARACTERISTICS EVALUATION FOR DRY STORAGE FACILITIES Analysis of this topic was not included in this evaluation since it is only applicable to a specific license application.

Chapter 3 PRINCIPAL DESIGN CRITERIA EVALUATION The changes associated with principal design criteria for the addition of the new FBM contents, FBM TSC, and new WBL are discussed and evaluated in chapters 7 and 8 of this SER.

4 Chapter 4 STRUCTURAL EVALUATION The staff reviewed the changes proposed by the applicant to the structural components of the approved structural configuration of the MAGNASTOR system, as described in the section below. The staff reviews the applicants analysis of each modification and associated information. The staff based their findings on the continued compliance of the amended design with the requirements prescribed in 10 CFR Part 72.

4.1 MAGNASTOR System TMI-2 Fuel Bearing Material Description MAGNASTOR system is designed and certified for the transport and storage of PWR and BWR spent fuels. This amendment would modify the system for the transport and storage of TMI--2 FBM. The MAGNASTOR TMI-2 FBM system is a MAGNASTOR system with two modified structural components. First, the concrete cask CC6 is modified by reducing the concrete compressive strength from 8000 psi to 6000 psi. Second, the TSC is reconfigured with a thinner 5-inch lid. In addition, the system includes a variable debris storage configuration using a WBL, STA, and a DMC that replaces the conventional fuel basket assembly of the MAGNASTOR system. The WBL, STA and DMC are dunnage and not credited in the safety analysis of the package.

4.1.1 Codes and Standards and Regulatory Guidance The applicant proposed no changes to the codes, standards, and material specifications, or in the use of regulatory guidance used in the previously approved MAGNASTOR system. The staff did not perform any additional reviews of these for this amendment. The applicant did, however, take an exception to the requirements of NB6111, that requires all pressure-retaining components, appurtenances, and completed systems be pressure tested. The preferred method is a hydrostatic test using water as the test medium. The pressure retaining system of the FBM TSC consists of the following components: FBM TSC shell, FBM TSC bottom plate, and FBM TSC Closure Lid. Portions of the FBM TSC undergo helium leak testing (FBM TSC shell and FBM TSC bottom plate) and the FBM TSC Closure Lid welded to the FBM TSC Shell undergoes visual and liquid penetrant exams. The staff determined this was an acceptable code alternative and has included this evaluation in Chapter 8 of this SER.

4.1.2 Evaluation of Change in Concrete Compressive Strength Since the concrete cask provides the storage and protection function for the TSC the staff reviewed the effect of the change in concrete compressive strength in cask analyses under 10 CFR Part 72 load conditions (normal, off-normal, and accident) and operational loads.

The staff determined that the proposed change in the concrete compressive strength from 8000 psi to 6000 psi would only affect design parameters where the allowable strength of concrete has been modified as a result of the concrete compressive strength. All other aspects of design are considered to remain as approved earlier. The changes to the design parameters are discussed below.

The applicant in FSAR section 3.11.5 reevaluated all loading conditions where a change in the compressive strength of concrete would affect the allowable concrete capacity evaluation. Since the density of the concrete remains unchanged the weight of the cask is unaffected. The total weight of CC6 loaded is 340,000 pounds as shown in Table 3.2.1-1b. For design, a load of 360 kips is considered.

5 For the lift loading condition in FSAR section 3.11.5.1, using 6000 psi concrete the bearing stress demand is 3.2 ksi, which has a factor of safety (FS) of 4.0 over the allowable bearing stress. In shear loading, the FS is significantly larger, where the allowable is 3.9 ksi and a demand of 0.04 ksi.

FSAR section 3.11.5.2.3 presents the loading conditions associated with normal conditions of operation affected by the change in concrete compressive stress. Using the combined stress in load combinations 1, 2, and 3 with a concrete compressive strength of 6000 psi, the maximum combined compressive strength demand is 1.42 ksi and the allowable compressive strength is 3.78 ksi, resulting in a FS of 2.65. The maximum concrete tensile stress demand is 0.09 ksi, resulting in a FS of 2.61 for concrete ultimate strength.

The storage accident events that are affected by the proposed change in the concrete compressive strength are addressed in FSAR section 3.11.5.4. The applicant conducted a bounding analysis for events including extreme temperature, tornado wind and tornado driven missile impact, flood, earthquake, and tip-over.

For thermal, flood, seismic, tornado wind and cask instability (tipover) from high energy tornado missile impact, the cask analysis remain unaffected by the change in the concrete compressive strength. Since the mass and the location of the center of gravity of the cask has not changed there will be no effect on the non-mechanistic tipover analysis.

However, the staff notes that the local damage from a missile strike is affected by the change in concrete compressive strength. Using a concrete compressive strength of 6000 psi the penetration depth is computed as 5.33 inches and a corresponding scabbing thickness of approximately 16 inches. This provides an overall safety factor of 1.58 against local damage.

For punching shear capacity under missile impact using a concrete compressive strength of 6000 psi, the concrete area required to resist the energy of the missile strike is 0.81 ft2, which is significantly less than the 20 ft2 area available against punching shear. The staff finds that the concrete shell itself has the capability to resist the missile impact force.

In addition, the staff reviewed the load combinations (4, 5, 6, 7 and 8) which include accident loads and finds, that for combined stress in accident events the minimum FS against compressive stress in concrete as 2.55 and the FS against concrete tensile strength is 2.5.

The staffs review of the drop analysis for the cask shows a crush depth of the concrete using 6000 psi concrete as 0.08 inch. Thus, the steel shell will not experience any loss of functionality.

For all other loadings the staff finds the analysis in the FSAR, prior to amendment 13, as applicable.

Based on the above findings, the staff concludes that the concrete cask CC6, as modified by amendment 13 to the MAGNASTOR system, meets the requirements of 10 CFR Part 72 for storage of the TMI-2 FBM.

4.1.3 Evaluation of Change in Closure Lid Thickness The weight of the lid used in the approved design is that of the composite lid weighing 10,500 lbs. The weight of the 5-inch-thick lid for the FBM TSC is 5,600 lbs. Given the maximum weight and a lower thermal profile, the staff finds that the lifting analysis for the MAGNASTOR system bounds the lifting conditions for the FBM TSC.

6 In addition, the staff reviewed the effect of the 5-inch-thick lid in the tipover and drop conditions.

The review established that the stresses in the lid, lid welds and the closure ring welds are bounded by the stresses determined using the composite lid. No additional analysis is required for this amendment to the lid thickness.

4.2 Treatment of the Waste Basket Liner The WBL is not credited for any safety function in the amended analysis and is considered as dunnage. The weight of the WBL is included in the maximum weight of the TSC analyzed.

However, staff notes that the WBL would add to the lateral stiffness of the TSC in drop and missile impact conditions. The use of the WBL provides for a more uniform and continuous contact surface in the dynamic analysis of the package than that provided by the discontinuous contact areas of the fuel basket lattice.

4.3 Treatment of other Dunnage Additional dunnage is used in the placement of the FBM within the WBL. The weight of the dunnage is accounted for within the maximum allowed payload weight. Dunnage includes the STA and DMC designed to be used with the WBL (also dunnage) within the FBM TSC. No credit is applied in the safety analysis to the dunnage, in either storage or transport configurations.

Dunnage is metallic in nature and compatible with the payload and FBM TSC material. The evaluation of dunnage for chemical and galvanic reactions is addressed in chapter 8 of this SER.

4.4 Evaluation Findings

F4.1 The applicant has met the requirements of 10 CFR 72.124(b). The SSCs that are important to safety of the MAGNASTOR system FBM TSC are designed to provide favorable geometry or permanently fixed neutron-absorbing materials.

F4.2 The applicant has met the requirements of 10 CFR 72.236(b). The SSCs that are important to safety of the FBM TSC are designed to accommodate the combined loads of normal, off-normal, accidents, and natural phenomena events with an adequate margin of safety. Stresses at various locations of the cask under various design loads are determined by analyses. Total stresses for the combined loads of normal, off-normal, accidents, and natural phenomena events are acceptable and are found to be within the limits of applicable codes, standards, and specifications.

F4.3 The applicant has met the requirements of 10 CFR 72.236(c) for maintaining structural design and fabrication of the MAGNASTOR system with the FBM TSC by including structural margins of safety for those SSCs important to nuclear criticality safety. The applicant has demonstrated adequate structural safety for the handling, packaging, transfer, and storage under normal, off-normal, and accident conditions.

F4.4 The applicant has met the specific requirements of 10 CFR 72.236(m). In the FSAR, NAC considered the design of the spent fuel storage cask for compatibility with the removal of the stored spent fuel from a reactor site, transportation, and ultimate disposition by the Department of Energy.

Based on the statements and representations in the application, as supplemented, the staff concludes that the structural properties of the MAGNASTOR system as modified in amendment 13 meets the requirements of 10 CFR Part 72 for use with debris removal and

7 storage of TMI-2 FBM and that the applicable design and acceptance criteria have been satisfied. The evaluation of the structural properties provides reasonable assurance that the MAGNASTOR system as modified by this amendment will allow safe storage of FBM for the certified term of 20 years. This finding is reached on the basis of a review that considered applicable regulations, appropriate regulatory guides, applicable codes and standards, and accepted engineering practices.

Chapter 5 THERMAL EVALUATION The applicant proposes to amend the certificate of the MAGNASTOR Cask System to authorize the storage of the FBM in the MAGNASTOR system located at the TMI--2 reactor site. The staff performed a thermal review to evaluate the effects of a new content of FBM, a new waste basket liner (WBL), and a new design configuration of the TSC (the FBM TSC) on the cask thermal design. The WBL, which is made of stainless steel, is used to replace the fuel basket structure for storage of FBM. The major components of the TSC (containing FBM), included in thermal analysis, are the shell, base plate, closure lid assembly, closure ring and redundant vent and drain port covers, which provide the confinement boundary during storage.

5.1 Thermal Design and Features As stated in FSAR section 1.3, the FBM WBL is a cylindrical shell plate design used to contain either loose debris or dunnage, which includes the STA and DMC, to house debris. The applicant stated, in FSAR section 3.12, that the design basis heat load for FBM TSC is 0.139 kW (139 watt), which is significantly less than the design basis heat load of 35.5 kW for the TSC containing fuel assemblies. Therefore, the maximum temperatures and thermal gradients for the FBM TSC will be significantly less than those for TSCs containing spent nuclear fuel assemblies.

The applicant states, in FSAR section 1.3.1.3, that the concrete cask provides an annular air passage to allow the natural circulation of air around the FBM TSC to remove the decay heat from the contents; however, the applicant has also stated, in FSAR section 1.3.1.3, that, due to the low heat load (0.139 kW) of the FBM TSC, air convection around the FBM TSC to concrete cask (CC) annulus is not required to demonstrate allowable FBM TSC and CC temperatures, and, therefore, temperature monitoring and air inlet/outlet visual inspections are not required for casks loaded with FBM TSCs. The FBM TSC is placed in the CC6 concrete cask, as stated in FSAR section 4.12.

The staff reviewed the thermal design and features of the FBM WBL as described in FSAR section 1.3 and determined that the description of the thermal design and features is appropriate for the thermal evaluation.

5.2 Thermal Model The applicant presented thermal models in FSAR section 4.12.1 with heat removal features for CC and FBM TSC under normal, off normal and accident conditions of storage:

A uniform heat load of 0.5 kW, instead of the design heat load of 0.139 kW for FBM TSC, is used for steady-state thermal analysis.

The FBM TSC will be helium backfilled to 1 atm but is conservatively assumed to be backfilled with nitrogen to 1 atm in thermal model.

No convection and radiation are considered inside FBM TSC.

Air with no flow is modeled in annulus between FBM TSC and concrete cask liner.

8 Top and bottom of CC is modeled as adiabatic.

Solar heat, natural convection, and radiation heat transfer are at outside side surface of the CC.

Ambient temperatures are 76 °F, 106 °F and 133 °F under normal, off normal, and accident conditions of storage.

The applicant described thermal models, in FSAR section 4.12.1, that included heat removal features for the MAGNASTOR transfer cask (MTC) and FBM TSC under on-site transfer operations (including vacuum drying and on-site transfer evolutions):

A uniform heat load of 0.5 kW, instead of the design heat load of 0.139 kW for FBM TSC, is used for steady-state thermal analysis.

The FBM TSC will be helium backfilled at 1 atm but is conservatively assumed to be backfilled with nitrogen at 1 atm in thermal model.

Neither convection nor radiation are modeled inside the FBM TSC.

The top and bottom of the MTC are modeled as adiabatic.

Natural convection and radiation heat transfer are included on the outer surface of MTC.

Air (for the on-site transfer) or water (for vacuum drying) are modeled with no circulation in the annulus between the FBM TSC and the MTC.

Ambient temperature is 100 °F (38°C) for both air and water cases.

The staff reviewed the descriptions, provided in FSAR section 4.12, of the development of the analysis models and the assumptions used in the analyses of the FBM TSC, CC and MTC and accepts the use of nitrogen backfill in the thermal model analysis because of its lower thermal conductivity (when compared to helium), as it will bound the use of helium as the backfill gas in the FBM TSC, as prescribed in FSAR section 4.12.

5.3 Thermal Evaluation Normal Conditions of Storage and Transfer Operation The applicant calculated the maximum average fill-gas temperatures for normal storage and the transfer operation, which is comprised of three phases (water phase, vacuum drying phase and transfer phase). The applicant presented the maximum FBM TSC and cask concrete temperatures in FSAR Table 4.12-1 for normal conditions and Table 4.12-2 for the transfer operation. The applicant stated, in FSAR section 4.12, that the maximum operating pressure under all operating conditions will be below 2 atm per the ideal gas law. This is because there is no increase in system pressure associated with the release of fission gas and there is no significant additional pressure expected from the gas generating media that is limited to a maximum 4% hydrogen within the FBM TSC cavity.

The staff reviewed FSAR Tables 4.12-1 and 4.12-2 and confirmed that (1) the water phase is bounded by vacuum drying in the thermal analysis, (2) maximum temperatures of the FBM TSC shell, cask concrete, and neutron shield are below the allowable limits in FSAR Tables 4.4-3 and 2.1-1 under normal storage and transfer operations (including the water phase, vacuum drying, and on-site transfer) and (3) TSC internal pressures under normal storage and transfer operations are below 2 atm (per the Ideal Gas Law) that is below the design limit of 103 psig (FSAR Table 2.1-1) for the MAGNASTOR system loaded with fuel assemblies. The staff confirmed that the allowable temperature and pressure limits, shown in FSAR tables 4.4-3 and 2.1-1 for normal, off-normal and accident conditions of storage, were reviewed and approved by the NRC in the previous amendment (e.g., MAGNASTOR Amendment No. 5), and accepts that,

9 based on thermal evaluations of the FBM contents, an indefinite operating time is allowed for all loading and closure operations, including on-site transfer, water phase, and vacuum drying.

The staff checked the material source book and ensured that all MAGNASTOR cask components are sustainable under an ambient cold temperature of -40 °F with no solar heat, in compliance with 10 CFR 71.71(c)(2).

Off-Normal Conditions of Storage The applicant presented the maximum FBM TSC shell and cask concrete temperatures in FSAR section 4.12.3 under off-normal conditions of severe ambient temperatures of 106 °F (hot weather) and 50% blocked air inlets. The applicant stated that the FBM TSC internal pressure, at maximum average fill-gas temperature under off-normal storage, is below the pressure limit of 103 psig that is accepted by the NRC for the MAGNASTOR system loaded with fuel assemblies.

The staff reviewed FSAR section 4.12.3 and confirmed that the maximum FBM TSC shell and cask concrete temperatures are below the allowable limits as shown in FSAR Tables 4.4-3 and 2.1-1 and the FBM TSC internal pressure is below the design limit, as shown in FSAR Table 2.1-1, under off-normal conditions of severe ambient temperatures of 106 °F. The staff confirmed that the event of the 50% blocked air inlet is bounded by the normal condition of storage in which a thermal analysis assuming no air flow in the annulus (100% blockage) was reviewed and accepted by NRC.

Accident Conditions of Storage The applicant evaluated three accident events of maximum anticipated ambient temperature (133 °F), fire accident, and 100% blocked air inlets using a bounding heat load of 0.5 kW (500 watt) for FBM TSC. The applicant presented the results in FSAR section 4.12.4. As shown in FSAR section 4.12.4, the calculated maximum FBM TSC shell and cask concrete temperatures are below the allowable limits for the event of maximum anticipated ambient temperature; and are bounded by the results of the design basis heat load of 35.5 kW for the fire accident. The applicant also noted that the results for normal storage analysis assuming no air flow in annulus are applicable for the event of 100% blocked air inlets.

The staff reviewed FSAR section 4.12.4 and confirmed that the maximum FBM TSC shell and cask concrete temperatures are below the allowable limits, as shown in FSAR Tables 4.4-3 and 2.1-1, and the FBM TSC internal pressures are below the design limit under maximum anticipated ambient temperature (133 °F), fire accident and 100% blocked air inlets.

The staff further confirmed that evaluations of FBM TSC under off-normal and accident level events are bounded by the spent fuel TSC evaluations because of the shared TSC design features, equivalent maximum system weights, low design basis heat load of 0.139 kW, and reduced internal canister pressures.

Thermal Stress Based on the temperature results, described above, for normal, off normal and accident conditions of storage, the staff has reasonable assurance that the resulting thermal gradients and thermal stresses of the TSC containing FBM will be bounded by those of the TSC containing spent fuel with a design heat load of 35.5 kW (FSAR section 3.11.6) which was reviewed and accepted by the NRC.

10 5.4 Hydrogen Generation The applicant stated, in FSAR section 1.4, that non-metallic FBM may be loaded into the FBM TSC provided maximum hydrogen generation during storage and transportation will not exceed the lower explosive limit (4% molar volume) and system pressure is evaluated as acceptable.

Any potential retention must be accounted for within total hydrogen generation.

The staff compared the decay heat, maximum FBM temperature, and FBM TSC internal pressure with those of the spent fuel TSCs (e.g., TSC1 ~ TSC4) which were approved by the NRC in MAGNASTOR Amendment No. 5 and has reasonable assurance that the FBM TSC will be bounded by the spent fuel TSC in hydrogen generation. The staff also referred to License Amendment Request - Three Mile Island, Unit 2, Decommissioning Technical Specifications, Response to Request for Additional Information (ML22276A024) and confirmed that for the FBM TSC backfilled with helium, there is no credible scenario under which a significant combustion, reaction, or activation of the FBM contents would occur under normal, off-normal and accident conditions of storage.

The applicant stated, in FSAR section 9.7, that the residual moisture in the FBM TSC is then removed by vacuum drying techniques and the FBM TSC dryness is verified through the steps below:

FBM TSC is evacuated to be less than or equal to 3 torr for greater than or equal to 30 minutes to ensure the FBM TSC cavity is dry of free water.

FBM TSC is backfilled with helium to a pressure of 1 atm to provide an inert atmosphere for the safe long-term storage of the FBM contents.

The staff reviewed the vacuum drying process described in FSAR Chapter 9 and accepts the criteria for limiting the hydrogen concentration less than 4.0% by volume of the total gas inventory in the FBM TSC and for limiting the FBM TSC pressure less than 3 Torr for vacuum drying operation.

5.5 Evaluation Findings

F5.1 The proposed changes of (a) adding the FBM as contents in the TSC and (b) using a WBL to replace the fuel basket structure for storage of FBM meet the thermal requirements of 10 CFR Part 72.

F5.2 The applicants thermal evaluations provide reasonable assurance that the FBM TSC and cask component temperatures and the FBM TSC internal pressures are below the allowable limits under loading operations and normal, off normal, and accidental conditions of storage.

F5.3 The gas generating media within the FBM TSC should be limited such that only a maximum 4.0 vol% hydrogen may be generated within the FBM TSC cavity to meet the 5 vol% hydrogen limit, in accordance with section 8.5.13.1, Flammable and Explosive Reactions, of NUREG-2215.

The staff determined that the thermal evaluation of the FBM TSC of the MAGNASTOR storage system complies with 10 CFR Part 72, and that the applicable design and acceptance criteria have been satisfied. The finding is reached based on a review that considered the regulation

11 itself, appropriate regulatory guides, applicable codes, model assumptions/methodology, and accepted engineering practices.

Chapter 6 SHIELDING EVALUATION The shielding review evaluates the ability of the proposed shielding features to provide adequate protection against direct radiation from the dry storage system contents. The shielding features must limit the dose to the operating staff and members of the public so that the dose remains within regulatory requirements during normal operating, off-normal, and design-basis accident conditions. The review seeks to ensure that the shielding design is sufficient and reasonably capable of meeting the operational dose requirements of 10 CFR 72.104 and 72.106 in accordance with 10 CFR 72.236(d). The staffs shielding review evaluated the proposed change requested in this revision in conjunction with the findings from previous staff analyses to determine whether, with the requested changes, the system continues to provide adequate protection from the radioactive contents of the fuel within the system. This review evaluated the methods and calculations employed by NAC to determine the expected gamma and neutron radiation at locations near the MAGNASTOR Transfer Cask (MTC) surface and at specific distances away from the concrete cask.

6.1 Shielding Design Description 6.1.1 Design Features MAGNASTOR is a dry storage system consisting of a metal cask and a welded stainless-steel canister with a welded closure to safely store the spent fuel. The system also includes a transfer cask as a shielded lifting device designed to hold the canister during loading operations, transfer operations, and unloading operations. The system contains a steel canister (TSC), waste basket liner, and concrete cask (CC6). The basket is replaced by waste basket liner to provide support for the FBM.

The thickness of the TSC lid is reduced to 5 inches in this amendment, due to the source term being one decade lower than the previously approved source term in the MAGNASTOR system.

6.2 Source Specification The content is FBM, that is composed of actinide and fission product produced during 90 days of operation before core accident of TMI-2. The FBM was not removed during the previous cleanup of the TMI-2 site activities. The FBM modeled as homogenous stainless steel of 25%

maximum payload weight of the WBL or 0.8513 g/cm3. The whole inventory is modeled in a single TSC. The WBL and segmented tube assembly configuration are considered in the evaluations. No credit is taken from basket or segmented tube assembly (STA) in the safety evaluation. FBM can be loaded directly into WBL or within other internal structures such as segmented tube assembly. The source region geometry is modeled as smeared stainless steel or in void of the cavity of WBL or seven opening of the STA. Table 5.13.1-1 (from NUREG-0683 Supplement 3, Tables 2.3 and 2.4) depicted total radionuclide inventory in Curies on 1/1/1990.

The applicant used the ORIGEN module of Scale 6.2.4 to convert inventory to gamma and neutron source for 33 years from 1/1/1990 to 1/1/2023. The daughter products are included in the source due to long decay time. The results of source term are grouped into 19 group photon and 28 group neutron sources. The neutron and gamma spectra are shown in the Table 5.13.1-2 and 3 respectively.

12 6.3 Shielding Model No changes were made to the shielding design of the CC6 for the MAGNASTOR dry storage system as the result of this amendment. The CC6 is used as an overpack in this amendment, as approved in the previous shielding design evaluations amendments. The TSC lid thickness changes from 9 inches to 5 inches due to much lower source term. In Amendment No.13, the applicant used the computer codes MCNP-6.2 that the staff found acceptable for the shielding analyses. The staffs determination is based upon the code being cited as a well-established code commonly used for spent fuel dry storage system shielding evaluations that the staff has found to be acceptable in section 6.5.4 of NUREG-2215, Shielding Analyses, and section 4.3 of NUREG/CR-6802, Dose Rate Estimation.

6.3.1 Shielding Model Specification The staff reviewed the MCNP model of the MAGNASTOR storage system as depicted by MCNP VisEd in FSAR figures 6.1 through figure 6.4 in Calculation Package No. 30097-5002, Revision 0, Three Mile Island Unit Two Shielding Evaluation, and found NAC modeled it in sufficient detail to accurately represent the TMI-2 FBMs within MAGNASTOR TSC.

Evaluation performed using MCNP6.2 with Amendment 13 content for CC6 and MTC which were approved in the previous amendment. There is no change in the material composition and dimensions of TSC, MTC and CC6. Geometry modifications are for WBL in TSC cavity and TSC lid thickness reduction. The FBM evaluated as homogenous volume containing 25% stainless-steel of maximum weight of the WBL (density of 0.8513 g/cm3). For STA model the source located inside the STAs. The total source term models uniformly for both WBL and STA configurations. Figures 5.13.2-1 and 5.15.2-2 shows the vised cross section for WBL and STA models. As no fissile material is included in the shielding model, only the neutron source, a subcritical multiplication factor is applied to the neutron source as part of the MCNP source magnitude multiplier. As there is no significant neutron source, the neutron dose is not a significant portion of either MTC or CC dose rates regardless of subcritical adjustment.

6.4 Shielding Evaluation The applicant calculated dose rates for the MTC and CC6 using the MCNP6.2 computer code.

FSAR table 5.13.1-1 shows the maximum fuel bearing material dose rates for CC6 radial surface profile. FSAR figure 5.13.3-2 shows the CC6 top dose profiles surface. FSAR figures 5.13.3-3 and 5.13.3-4 show MTC radial surface and top surface dose profiles.

In addition, since the CC6 dose rates for FBM are bounded by the concrete cask dose rates for spent fuel, the measurement locations and dose rates in Technical Specification 3.3.1, CONCRETE CASK Maximum Surface Dose Rate, are adequate to ensure offsite dose can be met.

6.5 Confirmatory Review and Analysis The staff reviewed the applicants shielding analysis and found it acceptable because the maximum offsite dose rates meet the limits in 10 CFR 72.236(d). The staff reviewed the radiation shielding evaluations, including the calculations of the sources, and the dose rates for the FBM in the MTC and CC6. The staff independently calculated source terms for the FBM that agrees with the applicant source term. The staff also performed confirmatory analyses of the dose rates for MTC and CC6. The staff find the applicant dose rates are similar or very close to

13 the staffs evaluation. The staff also finds the applicants determination of the bounding dose rates for FBM is bounded with spent fuel analyses in the previous amendments and acceptable and there is no need to evaluate offsite dose. Therefore, offsite doses from storage FBM are within regulatory limits. The staff concludes that the applicant has demonstrated that the MAGNASTOR dry cask storage system with the FBM in the CC6 meets the radiation protection requirements of 10 CFR 72.104 and 72.106 as referenced in 10 CFR 72.236(d).

6.6 Evaluation Findings

Based on the NRC staff's review of information provided for the MAGNASTOR application, the staff finds the following:

F6.1 Chapter 5 of the MAGNASTOR FSAR describes shielding structures, systems, and components important to safety in sufficient detail to allow evaluation of their effectiveness.

F6.2 Chapter 5 of the MAGNASTOR FSAR provides reasonable assurance that the radiation shielding features are sufficient to meet the radiation protection requirements of 10 CFR Part 20, 10 CFR 72.104, and 10 CFR 72.106.

F6.3 Operational restrictions to meet dose and as low as reasonably achievable (ALARA) requirements in 10 CFR Part 20, 10 CFR 72.104, and 10 CFR 72.106 are the responsibility of the TMI-2 staff. The MAGNASTOR shielding features are designed to assist in meeting these requirements.

Based upon its review, the staff has reasonable assurance that the design of the shielding system for the MAGNASTOR system, including the CC6 and the TSC, comply with 10 CFR Part 72 and that the applicable design and acceptance criteria have been satisfied. The evaluation of the shielding and radiation protection design features provides reasonable assurance that the MAGNASTOR system will provide safe storage of spent fuel in accordance with 10 CFR 72.236(d). This finding is based on a review that considered the appropriate regulatory guides, applicable codes and standards, the applicants analyses, the staffs confirmatory analyses, and acceptable engineering practices.

Chapter 7 CRITICALITY EVALUATION This amendment request is to remove the remaining damaged core material from TMI-2 reactor which was left in place as part of a previous licensing action to allow for a possession only license and post-defueling monitored storage (ML20059D154). The applicant has requested to store the remaining TMI-2 fuel bearing material in the MAGNASTOR system under 10 CFR Part 72 within the existing independent spent fuel storage installation (ISFSI) at the TMI site.

Staff reviewed the amendment request to determine whether the MAGNASTOR system will remain subcritical under all credible normal, off-normal, and accident events that may be encountered during the handling, loading, transfer, and storage of the damaged core material.

Staff reviewed the applicants criticality safety analysis to ensure that this evolution will meet the requirements of 10 CFR 72.124 and 72.236. Staff conclusions are based on the information provided by the applicant and the supporting calculations for storage of the damaged core material in the MAGNASTOR system.

14 7.1 Criticality Design Criteria and Features The MAGNASTOR storage system consists of a TSC, a concrete and metal storage overpack, and a lead-shielded transfer cask. The MAGNASTOR cask system is designed to meet the requirements of 10 CFR 72.124.

Since the previously approved MAGNASTOR (MAGNASTOR Amendment 12, ML23328A396) cask design is not changed by this amendment, staff evaluated only the use of the TMI-2 canisters for storage of the damaged core material. Staff reviewed the applicants modeling and assumptions and finds that they are consistent with the description of the design and contents specified in the FSAR. Staff also evaluated the criticality safety calculations and find that they are sufficiently detailed to support the staff evaluation. Based on this review, staff finds that the applicant continues to meet the requirements of 10 CFR Part 72.

7.2 Fuel Specifications The materials to be stored in the MAGNASTOR cask are specified in FSAR chapter 2. Stored materials consist of the debris remaining from the SNF involved in the accident at TMI-2 and is referred to as FBM. For the bounding fuel description used in the analysis, the boron multiplier identified in the decommissioning study is changed to reflect the maximum reactivity configuration justified in the study. This baseline decommissioning evaluation applies a burned fuel composition. The applicant used a simplified material composition to evaluate the fission products and actinides present in the fuel and compared the results to the fresh fuel case at an enrichment of 2.64 wt% 235U. The results of this study (as identified in Table 6-1 of the criticality calculation 30097-6001, Rev. 02) indicate that the bounding configuration is the fresh fuel assumption, which staff finds acceptable since it yields conservative results when compared to burned fuel since it removes the reactivity effects of the remaining actinides and fission products, yielding higher values for keff for the evaluated cases.

The applicant evaluated the minimum boron multiplier necessary to meet the Upper Safety Limit (USL) for fresh fuel (boron concentration is listed in TS 3.2.1), which was found to be 0.55 for 1200kg of FBM. The applicant then evaluated the maximum allowable uranium mass at a boron multiplier of 0.5, which was found to be 800kg of FBM.

As mentioned above, no credit is taken for the burnup of the fuel, and therefore the fuel is considered fresh fuel.

Staff finds that these stored material specifications are within the scope of the requirements of 10 CFR 72.124 (b) since the criticality safety of the facility is based on the canister geometry and fixed neutron absorbers.

7.3 Model Specifications The description of the model configuration used to evaluate the criticality safety of the facility is specified in FSAR chapter 2. The design of the TSC uses conservative assumptions to ensure that during all normal, off-normal, and accident conditions criticality safety is preserved.

Based on the use of the conservative modeling assumptions listed above, all of which tend to yield a higher reactivity of the system, staff finds that the modeling assumptions used in the criticality safety analysis are conservative and adequate to evaluate the subcriticality of the MAGNASTOR system loaded with fuel debris that is proposed in this amendment.

15 7.4 Criticality Analysis The applicant used the MCNP6.2 criticality code ENDF/B-VII cross-section library in their analysis. MCNP uses a three-dimensional Monte-Carlo computation scheme to calculate the neutron multiplication factor of an input system. This is a standard criticality code and staff find the use of this code acceptable for the fresh UO2 system.

An upper safety limit was calculated by the applicant for fresh UO2 fuel using MCNP6 Version 1.0 as shown in the validation report 91150-1060-012, Rev. 0. The range of applicability was shown to be between enrichments of 2.350 and 4.738 wt% U-235, which staff finds adequately bounds the enrichments for the TMI-2 fuel, and developed an USL of 0.9427. Although this USL was calculated using an earlier version of MCNP, comparison with MCNP6.2 showed agreement withing one standard deviation, and staff finds them applicable to this evaluation.

Based on the baseline fuel composition performed for the decommissioning evaluation (30097-DI-007), the applicant developed fuel compositions as shown in Table 4-3 of calculation 30097-6001, Rev. 2. The model geometry was developed based on several parameters of the basket and TSC, the transfer cask, the concrete cask, and the transport cask as shown in Tables 4-4, 4-5, 4-6, and 4-7 of the calculation package, respectively.

The applicant divided their analysis into several iterations, each building on the previous one.

First, they created MCNP models for the transfer, storage, and transport overpacks containing the decommissioning report FBM maximum reactivity configuration sphere. Since the baseline decommissioning evaluation applied a burned fuel composition, the applicant looked at an alternative approach for the FBM to minimize the complexity of this application. The application of a burned composition within storage and transportation licensing would require depletion code biasing and additional criticality code biasing associated with non-uranium actinides and fission products. To minimize these additional biases and analysis complications, the applicant used a simplified material composition that produces acceptable reactivities. Included in their analysis are results for both a No Fission Products case that removes all Pb, Ra, Ac, Sr, Pa, Sm, Eu, and Gd isotopes from the material cards, as well as a No Actinides case, which removes U, Np, Pu, and Am isotopes except 234U, 235U, 236U, and 238U and does not remove any fission products. The fresh fuel case has 2.64 wt % 235U fresh fuel, which is the second highest fresh fuel batch enrichment of the TMI-2 core, composition and removes the remaining actinides and fission products. For all cases, the total weight fraction computed prior to execution by MCNP is approximately 0.99; and the upscaling of the remaining materials by MCNP (which includes both boron and iron) is not significant due to the low amount of upscaling done. The results of this study demonstrate that fresh fuel at 2.64 wt % U-235 is the bounding of these material descriptions and results in reactivities that can be compensated for by reducing fissile material mass and/or slightly increasing the boron content of the FBM. Application of the fresh fuel material composition allows the use of the fresh fuel USL (given the range of applicability discussion in section 6.3 of the calculation report). Staff finds that the fresh fuel approach is acceptable for evaluating the safety of the TMI-2 FBM due to the additional conservatisms introduced by this method of evaluation, including maximizing the amount of U-235 and reducing the amount of neutron absorption materials.

Next, the applicant evaluated the initial configuration and adjusted the parameters of the baseline case to ensure that the system was below the USL. Based on the initial assumption of a 1200kg mass limit, the boron multiplier needed would be 0.55 to meet the USL. To compensate for this, the applicant performed a parametric study on the mass required to meet the USL with a boron multiplier of 0.5 and found that a reduction in mass limit to 800kg would

16 achieve this at a keff of 0.93621. Staff finds that this reduction in the mass limit is appropriate and conservative for this analysis based on the overall reduction in fissile mass allowed.

Once the maximum system configuration was determined the applicant evaluated the impacts of various fissile material sphere locations within the overpack and an H/U ratio study similar to what was done in the decommissioning report to verify that the particle size and pitch of FBM are bounding for the system. The original decommissioning report relied on a FBM pellet diameter of 0.6 cm and a pitch of 1.6 cm. The applicant performed two parameter studies to verify that this also holds true for the fresh fuel model. The first study fixed the pellet diameter and varied the pitch (i.e., the H/U ratio) and the second applied a fixed H/U ratio and varied the pellet diameter. As shown in Figure 6-7 and Figure 6-8 of the calculation report, the resulting curves demonstrate that within the statistical uncertainty of the evaluations the 0.6/1.6 cm options remain the most reactive.

With this bounding configuration, the applicant evaluated the effects of steel within the unit cell.

This was performed since the majority of the FBM is mixed with, or has adhered to metal components, and small levels of steel can have a net increase in keff. The applicant found that as fuel mass increases, the effect of the steel on the multiplication factor is less. For the bounding cases, a maximum mass of 700kg and a boron multiplier of 0.5 was found to be most reactive at a level of 3% steel in the water/steel moderator mixture. Staff reviewed the applicants analysis and finds that while the effect of the steel does have an effect, it is a small one, and agrees with the approach of taking the most conservative (i.e., 3%) steel as appropriate and conservative for this analysis.

The applicant then evaluated the system to determine that the most conservative parameters were chosen for the evaluation. As noted above, the evaluations performed by the applicant took only partial credit for the expected boron and iron content within the FBM. Crediting these fractions at their nominal values provides an indication as to the conservatism of the calculations. In addition, the FBM mass is also reduced to a more realistic value. As identified by the applicant, the maximum FBM mass within the TMI-2 facility is estimated at 1097 kg both within and outside of the reactor vessel. The applicant plans to divide the FBM material into 14 separate TSCs. Staff noted that the applicant conservatively placed the materials into three TSCs for their evaluation (i.e., 366 kg U in each) and that with either the baseline 0.5 boron/0.9 iron multipliers or 1.0 multipliers used by the applicant significantly reduces reactivity further.

Evaluation results for these scenarios are listed in Table 6-6 of the calculation report. At 366 kg, a steel in the unit cell fraction of 5% is bounding. The results at 1.0 multipliers demonstrate the rapid decrease in system reactivity for steel fractions above 15%. Note that even with no reduction in boron and iron credit, the masses are significantly less than the unadjusted fuel composition (i.e., with 16.21% overall impurity fraction relative to the 10% impurity fraction analyzed by the applicant). Staff finds that by reducing the number of TSCs analyzed they are conservatively increasing the multiplication factor over what the real transportation evolution will be, and that this imparts a significant conservatism to their analysis.

Optimum moderation studies were then performed for both Part 71 and Part 72 requirements.

Based on the applicants conservative model described above, they found no change in system reactivity due to the FBM sphere being infinitely reflected, and therefore flooding the cannister has no effect, and is bounding for this analysis. Staff finds that the infinitely reflected sphere case is bounding and conservative for the same reasons.

Finally, the applicant compared the validation range of applicability with that of the most reactive configuration. The applicant used the most reactive configuration identified above and listed the

17 parameters in table 6-15 of the calculation package. Staff noted that the majority of the most reactive configuration variables are within the validated ranges. The differences between the validation cases and the configuration analyzed by the applicant are for bare (i.e., no cladding) pellets in a spherical array. However, since the pitch and pellet diameter are within the validated range, these differences (i.e., bare pellets in a spherical array) are acceptable with respect to neutron interactions. In addition, staff finds that the lack of cladding is acceptable as cladding is a transparent material with respect to neutron interactions. Based on the above, staff finds that it is acceptable to apply the USL from section 4.1 of the calculation report to the evaluations performed by the applicant.

7.5 Evaluation Findings

Staff reviewed the information provided in Amendment No. 13 of the MAGNASTOR cask system application and determined that it is in compliance with the requirements in 10 CFR 72.124, and 10 CFR 72.236(c). Staff also determined that the results of the applicants evaluation of the TMI-2 FBM, as described in this application, remain less than the USL for each of the evaluated cases. The applicant incorporated several conservative assumptions and evaluated the FBM over a range of bounding credible scenarios. As a result, staff has reasonable assurance that the MAGNASTOR spent fuel dry cask storage system containing TMI-2 FBM, as described in this amendment to the application, will remain safe while in storage.

Specifically, the applicants nuclear criticality safety evaluation demonstrates that the MAGNASTOR spent fuel dry cask storage system will continue to meet the relevant regulatory requirements and the staff finds the following:

F7.1 The applicant described structures, systems, and components important to criticality safety in sufficient detail in the FSAR to enable an evaluation of their effectiveness.

F7.2 The cask and its spent fuel transfer systems are designed to be subcritical under all credible conditions.

Chapter 8 MATERIALS EVALUATION 8.1 Summary of Proposed Changes for Materials The staff reviewed the information provided in the application for the proposed Amendment No.13 for the MAGNASTOR Storage System. The purpose of the staffs materials evaluation for MAGNASTOR Amendment 13 is to assess whether the applicant adequately described and evaluated the proposed changes related to component materials for the MAGNASTOR storage system to ensure that the requirements of 10 CFR Part 72 are satisfied. The specific changes proposed in the amendment that are relevant to the staffs materials evaluation include the following:

A new type of radioactive contents, FBM from the damaged TMI--2 reactor, is to be stored inside the MAGNASTOR TSC; the TSC is the confinement boundary for the MAGNASTOR system. An additional design configuration of the TSC (the FBM TSC) is added to accommodate the FBM and the new TSC internal components described below.

The application proposes to eliminate the requirement to perform a hydrostatic pressure test, in accordance with American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC),Section III, Subsection NB, Article NB-6000, of the FBM TSC closure lid weld.

18 A new WBL made from stainless steel is used, in lieu of the fuel basket, for the storage of FBM inside the TSC. The WBL is designed to enclose and structurally support the FBM contents inside the TSC and is credited in the radiation shielding analysis; however, it has no confinement or criticality control function.

The application states that the design and construction of the new WBL is in accordance with the applicable requirements of the ASME BPVC,Section III, Subsection NF; ASME BPVC Section IX; and ASME BPVC Section V.

The application states that the FBM may be loaded loose into the WBL, or it may be placed within other internal stainless steel structures that are, in turn, loaded into the WBL. These optional WBL internal components are the STA and the DMC. The application states that these components, which are also referred to as dunnage, are used to facilitate handling and placement of the FBM inside the WBL, but they are not credited in the safety analyses for demonstrating adequate functional performance of ITS structures, systems, and components.

The application, as revised in its RAI response (ML23178A224), specifies that helium gas is to be used as the fill gas inside the TSC. The application states that no adverse chemical or galvanic reactions are expected for the FBM contents and the TSC, WBL, STA and DMC components in the helium fill gas environment.

The NRC staff performed the materials evaluation for the MAGNASTOR Amendment No. 13 by following the technical guidance in NUREG-2215, Standard Review Plan for Spent Fuel Dry Storage Systems and Facilities (ML20121A190).

8.2 Drawings The drawings are provided in FSAR section 1.8. The Amendment No. 13 application includes new drawings that convey the modified TSC, and the new internal WBL, STA, and DMC components for the storage of the FBM. The dimensions of certain FBM TSC components are modified (relative to previous approved MAGNASTOR TSC configurations) to accommodate the new internal components and the FBM contents; however, the welded stainless steel materials used for construction of the TSC are unchanged. The NRC staff reviewed the drawings for the FBM TSC and the new WBL, STA, and DMC components and confirmed that they adequately specify the materials and alloy types, standard alloy product form specifications, welding requirements, nondestructive examination (NDE) performance requirements, and NDE acceptance criteria for these components. Therefore, the staff finds that the component drawings are acceptable, with respect to the materials, fabrication, and examination requirements for the FBM TSC, WBL, STA, and DMC.

8.3 Codes and Standards for Materials, Fabrication, and Examination The FBM TSC confinement boundary is structurally designed and fabricated to the same ASME BPVC,Section III, Subsection NB requirements, as the previous approved TSC configurations for storage of spent fuel. The changes affecting the FBM TSC include changes to TSC dimensions to accommodate the new TSC internal components that hold the FBM contents and elimination of the ASME BPVC,Section III, NB-6000 hydrostatic pressure testing requirement for the FBM TSC closure lid weld. The staffs evaluation of the FBM TSC closure lid weld integrity, considering the elimination of hydrostatic pressure testing requirement, is addressed below in Section 8.4 of this SER.

19 The staff identified that the use of Subsection NB requirements for materials, fabrication, and examination of the FBM TSC confinement boundary is consistent with the guidance in NUREG--2215 for storage canisters that are used for confinement of spent fuel. For the FBM TSC, the staff confirmed that ASME BPVC requirements specified in the application for materials, fabrication and examination of the FBM TSC, including the selection of stainless steel base materials, welding and related fabrication methods, and NDE techniques and acceptance criteria, are all the same as those that were previously approved by the NRC for the earlier TSC configurations that store spent fuel. The staff determined that the use of these codes and standards are acceptable for the FBM TSC since the safety function performance requirements for the FBM TSC are generally not as demanding as the safety performance requirements for the previous approved spent fuel TSCs. This is due to the fact that the FBM contents has lower radioactivity sources, lower decay heat load, and there are no unique design features (dedicated neutron absorbers, and internal support structures) that are relied upon to ensure that the FBM contents is maintained in an analyzed subcritical critical configuration. Therefore, since the codes and standards for the FBM TSC are consistent with the guidance in NUREG-2215 Section 8.5.2, Codes and Standards, the staff found that the codes and standards for the materials, fabrication, and examination of the FBM TSC are acceptable.

The application requires that the design and construction of the new TSC-internal WBL follow the applicable requirements of Subsection NF of the ASME BPVC,Section III. The staff determined that the use of Subsection NF is acceptable for the construction of the WBL since the WBL is not a confinement boundary for the radioactive contents, and the WBL structure is not relied upon or credited for maintaining an analyzed subcritical geometry to ensure criticality safety. The staff noted that, unlike with the fuel baskets that are used to hold spent nuclear fuel assemblies inside the previous approved configurations of the MAGNASTOR TSC for storage of spent fuel, the use of internal support structures to maintain a subcritical spatial arrangement and geometry of radioactive contents is not required for FBM contents, as demonstrated in the application criticality safety analyses, which are evaluated in chapter 7 of this SER.

The staff confirmed that application drawings and the description of welding requirements specify that the weld joints in the WBL must be fabricated using weld procedures and personnel that are qualified in accordance with ASME BPVC Section IX requirements. The staff also confirmed that the application drawings and description of examination requirements specify that performance of NDE must follow the applicable requirements of the ASME BPVC Section V, and the NDE acceptance criteria are in accordance with the applicable requirements of Subsection NF. Additionally, the staff evaluated the WBL stainless steel alloy type and associated ASME BPVC Section II base material product specifications and verified that they are acceptable for use in the fabrication of the WBL components, since these materials are allowed for use in the construction of structural supports in accordance with the ASME BPVC Section III, Subsection NF.

The application states that optional WBL-internal segmented tube assembly (STA) and debris material container (DMC), also referred to as dunnage, may be used to facilitate handling and placement of the FBM contents inside the WBL. However, the staff noted that these items are not relied upon or credited for performing any safety function, such as confinement, criticality control, shielding, or heat removal during FBM storage. The staff noted the application drawings specify suitable stainless steel materials, welding qualification requirements, and NDE requirements for these components. Therefore, the staff finds that the codes and standards for the STA and DMC components are acceptable.

20 8.4 FBM TSC Closure Lid Weld Integrity The application proposes to eliminate the requirement to perform a hydrostatic pressure test, per the ASME BPVC Section III, Subarticle NB-6200, of the FBM TSC. To meet the requirements of Subarticle NB-6200, the hydrostatic pressure test must be performed at no less than 1.25 times the lowest design pressure of the TSC. For the previously approved TSC configurations that are used to store spent nuclear fuel (SNF), a hydrostatic pressure test of the SNF TSC is performed to look for water leakage from the closure lid weld. During the hydrostatic pressure test of the SNF TSCs, only the closure lid weld is inspected to detect water leakage; the hydrostatic pressure test of the SNF TSCs is not used to address the pressure-retaining integrity of any other SNF TSC confinement boundary welds such as the TSC shell welds. As such, the utility of the hydrostatic pressure test is limited in scope to only one weld in the confinement boundary for storing SNF. However, the staff also noted that, as per the current approved design for storing SNF, the TSC closure lid weld is not subjected to a helium leakage test, whereas as the other SNF TSC confinement boundary welds are subjected to the helium leakage test, and this provision will remain applicable to the FBM TSC. Therefore, the FBM TSC closure lid weld would only be subjected to the current required progressive dye penetrant test (PT) surface examsone PT exam for each of the three weld layersas a means to ensure weld integrity after fabrication; there would not be any fluid test performed to address the pressure-retaining integrity or the leak tightness of the FBM TSC closure lid weld.

The applicants justification for eliminating the hydrostatic pressure test for the FBM TSC closure lid weld is based on the adequacy of existing ASME BPVC Section III and Section IX requirements for design and fabrication of the closure lid weld, as well as NDE of the weld using progressive PT. The staff reviewed this justification and considered additional factors, as discussed below.

The staff noted that, for weld joints in pressure vessels, the purpose of the hydrostatic or pneumatic pressure test and the helium leakage test is to reveal thru-wall flaws and leakage paths that may not have been detected during the NDE of the weld joint; however, these tests each have unique functions to achieve this safety objective. In order for the hydrostatic or pneumatic pressure test to be beneficial, the system pressure and hold time at pressure must be sufficient to provide some driving force for a preexisting fabrication defect that is not a thru-wall defect to propagate through the wall to reveal itself through fluid leakage.

The helium leakage test has a high level of sensitivity that is capable of detecting small preexisting leakage paths associated with thru-wall fabrication defects that may not have been detected by NDE. In the case of the SNF TSC, no helium leakage test is performed on the TSC closure lid weld because this weld meets the criteria in NUREG-2215 Section 8.5.3.3.2, Helium Leakage Testing, according to which, large lid-to-shell confinement boundary field welds of austenitic stainless steel canisters with redundant confinement closures may be excepted from leakage testing, as described therein. While a hydrostatic pressure or pneumatic pressure test is an ASME BPVC requirement that is implemented for the SNF TSC to look for water leakage from the TSC closure lid weld, the likelihood that progressive PT would not detect a thru-wall fabrication defect is low. For the specific case of the FBM TSC, there would be very little benefit to performing the hydrostatic pressure test since the FBM TSC operating pressure is nearly equal to outdoor ambient pressure; thus, the driving force for leakage from a postulated preexisting thru-wall fabrication defect in the FBM TSC closure lid weld is a low risk concern given the physical form of the FBM contents and other factors discussed further below.

21 The staff confirmed that the heat load of the FBM contents is several orders of magnitude lower than the heat load for SNF contents. As such, the maximum FBM TSC pressures under normal, off-normal, and accident conditions of storage are far lower than those for the SNF TSC.

Therefore, the staff determined that there would be a low driving force for leakage of the internal helium backfill gas through a small postulated thru-wall fabrication defect in the FBM TSC closure lid weld. The staff also noted that the likelihood of such a thru-wall fabrication defect existing in the FBM TSC closure lid weld is very low since the progressive PT of three separate weld layers would ensure that any indication of an unacceptable surface defect is detected for each of the three layers. The lack of unacceptable surface indications on all three weld layers adequately ensures that there is no through-wall defect. Further, the FBM TSC includes another welded TSC closure joint (in addition to the closure lid weld), constituted by the FBM TSC closure ring welded to the TSC shell and TSC closure lid. The final pass of the FBM TSC closure ring welds are examined using PT. The FBM TSC closure ring welds provide a fourth PT-examined material boundary to the release of helium backfill gas in the very unlikely event that a through-wall fabrication defect exists in the FBM TSC closure lid weld.

While there is some likelihood that a small subsurface flaw could be embedded in one of the weld layers, which the progressive PT surface exam cannot detect (since it only detects surface-breaking flaws), the staff has assessed that the potential safety consequences of such a flaw are very low. The potential concern with such a flaw, with respect to internal pressure loading, would be the possibility for it to propagate through the total thickness of the weld joint and become a leak path. The staff determined that rapid flaw propagation through the TSC closure lid weld, due to non-ductile fracture, is not a concern since the austenitic stainless steel construction of the TSC welds and base metal precludes brittle fracture over the full range of service temperatures. Since the weld material is ductile for all service temperatures, the crack driving force associated with internal pressure inside the FBM TSC for normal, off-normal, and accident conditions of storage is too low to cause an embedded fabrication flaw to propagate through the weld joint and cause leakage. Therefore, pressure testing of the FBM TSC closure lid weld is not needed to address the potential for propagation of a non-though-wall fabrication defect.

Further, the application identifies that no significant quantities of releasable fission gases are remaining within the FBM as a result of the reactor accident conditions, and thus there is no increase in system pressure associated with the release of fission gases inside the FBM TSC.

The application also states that no significant additional pressure inside the TSC is expected from gas generation from other foreign material or filter material in the FBM. Therefore, considering that (1) the radioactive content of the loaded FBM TSC is predominantly in a stable physical form, with little potential for significant radioactive gas generation, and (2) there is a very low driving force for helium backfill gas leakage through a postulated through-wall fabrication defect, the staff determined that the radioactive gas release consequence of a postulated through-wall fabrication defect in the FBM TSC closure lid weld is sufficiently low to support a risk argument for eliminating the hydrostatic pressure test as a means to determine if such a flaw exists.

Based on the foregoing considerations, including (1) the very low likelihood of a through-wall fabrication defect existing in both the FBM TSC closure lid weld and the redundant FBM TSC closure ring welds, and (2) the very low radioactive release consequence assuming that postulated through-wall fabrication defects are present in both the FBM TSC closure lid weld and closure ring welds, the staff determined that the increase in risk to public health and safety associated with the elimination of the hydrostatic pressure test of the FBM TSC is negligible.

22 Therefore, the staff finds that the applicants proposal to eliminate the requirement to perform a hydrostatic pressure test of the FBM TSC is acceptable.

8.5 Mechanical Properties of Materials According to the application, the only new TSC internal component that is credited in the MAGNASTOR structural evaluation is the WBL, which contains the FBM contents. The STA and the DMC are not safety related and are not credited in the structural analyses. The staff noted that the WBL is fabricated from the same type and specification of stainless steel as the TSC. The staff confirmed that the application includes all the information necessary to assure that the tensile and elastic properties for this stainless steel demonstrate that the WBL meets the applicable structural design criteria in the ASME BPVC Section III Subsection NF. These properties include the design stress intensity, yield stress, tensile strength, modulus of elasticity, Poissons ratio, coefficient of thermal expansion, and density. The staff confirmed that the values for these properties are consistent with those specified in the ASME BPVC,Section II, Part D, as required by Subsection NF of the ASME BPVC Section III. The staff also noted that a fracture toughness evaluation of the WBL stainless steel is not required since the type of wrought austenitic stainless steel used to fabricate the WBL does not undergo a significant ductile-to-brittle transition as a function of decreasing temperature down to the lowest service temperature; the ASME BPVC Section III Subsection NF specifies that material qualification testing (i.e., notched bar impact tests) to validate fracture toughness properties is not required for this type of wrought austenitic stainless steel material. Therefore, based on the foregoing evaluation, the staff determined that the mechanical properties of the stainless steel WBL are acceptable.

8.6 Thermal Properties For the stainless steel WBL, the staff reviewed the material thermal properties used in the thermal evaluation, including the thermal conductivity, specific heat capacity, and thermal diffusivity, and confirmed that these properties are consistent with those specified in the ASME BPVC Section II, Part D. Therefore, the staff determined that the thermal properties of the WBL materials are acceptable. With respect to the thermal performance of the WBL material and the FBM contents, the staff confirmed that the heat load of the FBM contents is less than the heat load of the spent nuclear fuel that is stored in previous approved MAGNASTOR design configurations. Therefore, based on the previously approved thermal evaluation of the MAGNASTOR system with spent fuel contents (MAGNASTOR Amendment 0, ML090350589), the staff determined that the application adequately ensures that the stainless steel WBL and FBM contents is not susceptible to adverse physical or metallurgical changes due to elevated temperatures.

8.7 Radiation Shielding and Criticality Safety The application does not include any changes that would affect the function of the shielding materials for the transfer cask, concrete cask (CC6) and TSC for loading, transfer, and storage operations. The reduction in the compressive strength of the concrete used in CC6 from 8000 psi to 6000 psi would not affect shielding performance because the concrete density remains the same. The staff confirmed that the shielding evaluation adequately considered the properties of the stainless steel used in the new WBL, and the shielding properties of the stainless steel WBL material are the same as those previously evaluated for TSC. Therefore, the staff determined that the WBL materials are acceptable with respect to radiation shielding.

23 The application states that criticality control for the FBM is achieved through a combination of neutron absorbing species that are already present within the FBM and a limitation on the mass of fissile material allowed within a TSC. The staff noted that the proposed design configuration of the MAGNASTOR system for storage of FBM does not use any dedicated neutron absorber materials for criticality control; and there are no TSC internal support structures that are relied upon for maintaining an analyzed subcritical geometry and spatial arrangement of fissile FBM contents to ensure criticality safety. The staffs evaluation of the applications criticality safety analyses is addressed in chapter 7 of this SER.

8.8 Corrosion Resistance and Content Reactions The staff noted that the application, as revised in the RAI response (ML23178A224), specifies the use of helium gas as the canister fill gas during storage. Considering the physical and chemical form of the FBM contents (addressed below) and the fact that the helium fill gas is chemically inert and will displace oxygen and moisture inside the canister, the staff determined that there is no concern with corrosion of the stainless steel FBM TSC, WBL, STA, or DMC components. Therefore, the staff finds that the corrosion resistance of FBM TSC, WBL, STA, and DMC components is acceptable.

The application includes a description of the physical and chemical form of the FBM contents and briefly addresses certain filter media that are associated with the FBM contents. The application states both the FBM and the associated filter media contents are loaded into the WBL for storage inside the sealed FBM TSC. In its response (ML23178A224) to the staffs RAI requesting information concerning the physical and chemical form of the filter media that are associated with the FBM, the applicant provided a description of the filter media contents to be stored inside the FBM TSC and described how the filter media are associated with the FBM.

The RAI response (ML23178A224) states that filter media are generally used to facilitate decontamination of the damaged TMI Unit 2 reactor; several types of filter media are disposable materials that contain radioactive FBM particles, including radioactive fission products and other radioisotopes from damaged reactor fuel assemblies and non-fuel reactor material activation products. The applicant clarified that the disposable filter media containing FBM that are to be stored inside the TSC are composed of unreactive metallic and inorganic compounds.

The staff reviewed the applicants RAI response (ML23178A224), including the associated updates to the application, and confirmed that, other than the potential for hydrogen gas generation through radiolysis of residual moisture and limited quantities of organic compounds present in the FBM contents, the FBM and associated filter media contents will not undergo chemical reactions in the helium gas environment that could adversely affect the safe storage condition of these radioactive contents. The staffs evaluation of the potential for hydrogen gas generation by radiolysis of residual moisture and organic materials present in the FBM, and the associated limits on the quantity of these species allowed in the FBM TSC, is documented in Section 5.4 of this SER on hydrogen generation. Therefore, considering the potential for corrosion and content reactions, the staff determined that the application provides an acceptable description of FBM and associated filter media contents.

8.9 Evaluation Findings

F8.1 The staff reviewed the application and concludes that the applicant has met the requirements in 10 CFR 72.236(b). The applicant described the materials used for the storage system SSCs that are important to safety in sufficient detail to support a safety finding.

24 F8.2 The staff reviewed the application and concludes that the applicant has met the requirements in 10 CFR 72.236(g). The properties of the materials used in the storage system design have been demonstrated to support the safe storage of the FBM contents.

F8.3 The staff reviewed the application and concludes that the applicant has met the requirements in 10 CFR 72.236(h). The materials of the FBM TSC and WBL are compatible with FBM contents in the storage system operating environment such that there are no adverse chemical or metallurgical reactions or service-induced degradation of SSCs that are important to safety.

F8.4 The staff reviewed the application and concludes that the applicant has met the requirements in 10 CFR 72.234(b). Quality assurance programs and control of special processes are demonstrated to be adequate to ensure that the materials, fabrication, examination, and maintenance for storage system SSCs support the intended functions of the SSCs that are important to safety.

8.10 Conclusion The NRC staff has reviewed the statements in the application and concludes the materials used in FBM configuration of MAGNASTOR storage system have been adequately described and evaluated in accordance with 10 CFR Part 72.

Chapter 9 CONFINEMENT EVALUATION The staff reviewed the proposed changes as addressed in the Summary of this SER and confirmed that the proposed changes have no negative impact to the confinement performance of the FBM TSC. The confinement design and features of the FBM TSC remain unchanged as those of TSC1 ~ TSC4 in the previous amendments.

The applicant noted, in FSAR table 2.1-2, that (1) the FBM TSC shell and FBM TSC bottom plate are subjected to a helium leak test to 2 x 10-7 cm3/sec (helium), and (2) the FBM TSC closure lid is welded to the FBM TSC shell in the field using 3-layer welds with visual and liquid penetrant exams performed on the root, mid plane and final weld surface to eliminate potential leakage paths.

The applicant stated, in FSAR section 10.1.3, that a shop helium leakage test of the FBM TSC closure lid shall be performed following fabrication: the leakage test shall be performed in accordance with ANSI N14.5, American National Standard for Leakage Tests on Packages for Shipment of Radioactive Materials, to confirm the total leakage rate is less than, or equal to, 2 x 10-7 cm3/s (helium).

The applicants structural and thermal evaluations of the new FBM contents, associated FBM TSC, new WBL, and the proposed helium leakage testing on the confinement boundary of the FBM TSC, demonstrate that the FBM TSC maintains its confinement capability. The staff determined that the FBM TSC proposed in this amendment application is acceptable based on the design, components, and helium leakage test conditions. Therefore, the staff concludes that the proposed MAGNASTOR FBM TSC meets the confinement requirements in 10 CFR 72.236 and will continue to fulfill the regulatory requirements and the confinement acceptance criteria as listed in section 9.4, Regulatory Requirements and Acceptance Criteria, of NUREG-2215, Standard Review Plan for Spent Fuel Dry Storage Systems and Facilities.

25

9.1 Evaluation Findings

F9.1 The confinement system of the FBM TSC has been evaluated per helium leak test and other appropriate tests acceptable to the NRC to demonstrate that the design will reasonably maintain confinement capability under normal, off-normal, and credible accident conditions, in accordance with 10 CFR 72.236(l).

F9.2 The storage container confinement system will be inspected to ascertain that there are no cracks, pinholes, uncontrolled voids, or other defects that could significantly reduce its confinement effectiveness, in accordance with 10 CFR 72.236(j).

F9.3 The design of the FBM TSC provides redundant sealing of the confinement system, in accordance with 10 CFR 72.236(e).

F9.4 On the basis of review of the FBM TSC, the staff concludes that the proposed changes have no negative impact on the confinement system of the FBM TSC and the FBM TSC will continue to meet the confinement requirements of 10 CFR 72.236.

The staff determined that the confinement evaluation of the FBM TSC of the MAGNASTOR storage system complies with 10 CFR Part 72, and that the applicable design and acceptance criteria have been satisfied. The finding is reached based on a review that considered the regulation itself, appropriate regulatory guides, applicable codes, and accepted engineering practices.

Chapter 10 RADIATION PROTECTION EVALUATION Since the average dose rates around the cask for normal, off-normal and accident conditions for FBM in the MAGNASTOR system are lower than when loaded with the 37 PWR spent fuel assemblies and associated nonfuel hardware or 89 BWR spent fuel assemblies with or without zirconium-based alloy channels as estimated in previous amendment, the PWR or BWR content fuel assemblies bound the FBM content. The exposure rate from radiation emitted from the FBM is lower than of the spent fuel since dose rates for FBM system as documented in the chapter 6 of this SER. The estimated exposure during operation and storage also based on PWR or BWR contents that have higher dose rates than FBM configurations and therefore bound the FBM exposure during operation and storage. Note the contamination from FBM system may be higher than associated spent fuel systems, therefore additional ALARA steps may be required during loading operation.

Chapter 11 OPERATION PROCEDURES AND SYSTEMS EVALUATION The staff reviewed the information provided by the applicant and found the applicant added section 9.7 to address operating procedures with the proposed FBM TSC, which required an operating procedures evaluation. The operating procedures in section 9.7 included procedures for loading the FBM TSC, transferring it to the vertical concrete cask (VCC) using a standard MTC, transporting and placing the loaded VCC, and for unloading the FBM TSC.

The staff reviewed the procedures for loading the FBM TSC included in sections 9.7.1 and 9.7.2 and determined that the procedures are acceptable because they address FBM TSC loading operations, including preparation of the transfer cask and FBM TSC, FBM loading into the FBM TSC, FBM TSC drying and backfilling, and FBM TSC sealing operations. The staff verified that the FBM TSC loading operations are consistent with and include the applicable operational steps as the approved operational procedures included in section 9.1.1 of the NAC

26 MAGNASTOR FSAR, Revision 12. The staff reviewed the operating procedures for FBM TSC transfer included in section 9.7.3 and determined that the procedures are acceptable because they address VCC preparation, transfer of the FBM TSC into the VCC using the transfer adapter, installation of the VCC upper segment, and VCC preparation for movement. The staff verified that the FBM TSC transfer operations are consistent with and include the applicable operational steps as the approved operational procedures included in section 9.1.2 of the NAC MAGNASTOR FSAR, Revision 12. The staff reviewed the operating procedures for transporting and placing the loaded VCC on the ISFSI pad in section 9.7.4 and determined that the procedures are acceptable because they address cask transportation using a vertical cask transporter, preparing the VCC for storage, and radiological surveys of the VCC within the ISFSI array. The staff verified that the VCC transportation and placement operations are consistent with and include the applicable operational steps as the approved operational procedures included in section 9.1.3 of the NAC MAGNASTOR FSAR, Revision 12.

The staff reviewed the procedures for unloading the FBM TSC included in section 9.7.5 and 9.7.6 of the application. The staff determined that the procedures for the FBM TSC retrieval from the VCC were acceptable because these procedures are consistent with and include the applicable operational steps as the approved operational procedures included in section 9.2 and 9.3 of the NAC MAGNASTOR FSAR, Revision 12.

11.1 Evaluation Findings The staff concludes that the operations descriptions, including procedures and guidance, for the operation of the dry storage system (DSS) are in compliance with 10 CFR Part 72, and that the applicable acceptance criteria have been satisfied. The evaluation of the operations descriptions provided in the FSAR offers reasonable assurance that the DSS will enable the safe storage of FBM. This finding is based on a review that considered the regulations, appropriate regulatory guides, applicable codes and standards, and accepted practices. Some of the key findings from the staffs review of Amendment 13 include:

F11.1 The FSAR includes acceptable descriptions and discussions of the DSS operations, operating characteristics and safety considerations, in compliance with 10 CFR 72.234(f).

F11.2 The FBM TSC is compatible with wet/dry loading and unloading. General procedure descriptions for these operations are summarized in chapter 9 of the applicants FSAR. Detailed procedures will need to be developed and evaluated on a site-specific basis.

F11.3 The DSS storage container design allows for ready retrieval of the fuel bearing material for further processing or disposal as required. The descriptions of the proposed DSS functions and operating systems with regard to retrieval of stored radioactive material from storage, in normal and off-normal conditions, are acceptable and comply with 10 CFR 72.236(m).

F11.4 The content of the general operating procedures described in the FSAR are adequate to protect health and minimize damage to life and property that is in compliance with 10 CFR 234(f).

F11.5 The radiation protection chapter of this SER evaluates the operations descriptions and systems, including implementation of operational limits and restrictions to meet the applicable regulatory requirements in 10 CFR Part 20 and

27 in 10 CFR Part 72 for a DSS, to facilitate compliance with these requirements by licensees using the DSS and to meet 10 CFR 72.236(d). A licensee using the DSS may also establish additional restrictions for use of the DSS at its site.

F11.6 The design and procedures for the DSS provide acceptable capability to test and monitor components important to safety, in compliance with 10 CFR 72.234(f).

Chapter 12 CONDUCT OF OPERATIONS EVALUATION There were no requested changes to conduct of operations. As such, no evaluation of this section is included.

Chapter 13 WASTE MANAGEMENT EVALUATION Analysis of this topic was not included in this evaluation since it is only applicable to a specific license application.

Chapter 14 DECOMMISSIONING EVALUATION Analysis of this topic was not included in this evaluation since it is only applicable to a specific license application.

Chapter 15 QUALITY ASSURANCE EVALUATION There were no requested changes to NACs quality assurance program, and none of the changes requested by NAC affect the quality assurance program.

Chapter 16 ACCIDENT ANALYSES EVALUATION NAC made minor changes in chapter 12 of the FSAR to ensure the new FBM, FBM TSC, and WBL are incorporated into the evaluation of accidents. Since NAC showed in its FSAR, and as NRC describes above in this SER, the evaluation results for these changes are either similar to or bounded by previous amendments. Therefore, the revisions requested by NAC do not affect the accident analysis evaluation for the system and do not alter the staffs previous evaluation of the accident analyses for the MAGNASTOR storage system.

Chapter 17 TECHNICAL SPECIFICATIONS AND OPERATING CONTROLS AND LIMITS EVALUATION In its application, NAC proposed incorporation of the changes listed in the Summary section above and associated changes in the technical specifications. The staff reviewed the technical specifications and the associated operating controls and limits to ensure they meet the requirements of 10 CFR Part 72. The staff evaluation of the adequacy of the technical specifications is provided in this SER.

Chapter 18 CONCLUSIONS The staff has performed a comprehensive review of the amendment application, during which it evaluated the following requested changes to the MAGNASTOR storage system:

add a new type of radioactive contents, FBM from the damaged TMI-2 reactor, to be stored inside the MAGNASTOR TSC;

28 add a new design configuration of the TSC (the FBM TSC) to accommodate the FBM and the new TSC internal components which includes:

reducing closure lid assembly thickness of the FBM TSC and remove the hydrostatic pressure test, adding a new WBL (based on the Greater Than Class C Waste WBL) made from stainless steel in lieu of the fuel basket, for the storage of FBM inside the FBM TSC, adding a new debris material container to be used as an operational device to handle and house finer debris; and adding a new segmented tube assembly to define cells for loading, and include concrete with a compressive strength of 6,000 psi vs. 8,000 psi for TMI-2 when using CC6.

Based on the statements and representations provided by the applicant in its amendment application, as supplemented, the staff concludes that the changes described above to the MAGNASTOR storage system will meet the requirements of 10 CFR Part 72. Amendment No. 13 for the MAGNASTOR storage system should be approved.

Issued with CoC No. 1031, Amendment No. 13.

on _______________.