ML102590476

Independent Spent Fuel Storage Installation, Updated Safety Analysis Report (Usar), Revision 19 - Chapter 12, Table of Contents - Pages 12-1 Thur 12.12-3

ML102590476
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Site:	Calvert Cliffs
Issue date:	09/09/2010
From:	Calvert Cliffs, EDF Group
To:	Office of Nuclear Material Safety and Safeguards
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Download: ML102590476 (73)

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CHAPTER 12 NUHOMS-32P DRY SHIELDED CANISTER LIST OF EFFECTIVE PAGES PAGE REVISION PAGE REVISION CALVERT CLIFFS ISFSI USAR LEP 12

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12.12-2 15 12.12-3 19 Figure 12.3-1 15 CHAPTER 12 NUHOMS-32P DRY SHIELDED CANISTER TABLE OF CONTENTS PAGE CALVERT CLIFFS ISFSI USAR 12-i Rev. 19 12.0 NUHOMS-32P DRY SHIELDED CANISTER 12.1-1

12.1 INTRODUCTION

AND GENERAL DESCRIPTION OF INSTALLATION 12.1-1 12.2 SITE CHARACTERISTICS 12.2-1 12.3 PRINCIPAL DESIGN CRITERIA 12.3-1 12.3.1 PURPOSE OF THE CALVERT CLIFFS INDEPENDENT SPENT FUEL STORAGE INSTALLATION 12.3-1 12.3.2 STRUCTURAL AND MECHANICAL SAFETY CRITERIA 12.3-1 12.3.2.1 Tornado Wind and Tornado-Generated Missile Loadings 12.3-1 12.3.2.2 Water Level (Flood) Design 12.3-1 12.3.2.3 Seismic Design 12.3-1 12.3.2.4 Snow and Ice Loadings 12.3-1 12.3.2.5 Combined Load Criteria 12.3-1 12.3.2.6 Weld Requirements 12.3-2 12.3.3 SAFETY PROTECTION SYSTEMS 12.3-5 12.3.3.1 General 12.3-5 12.3.3.2 Protection by Multiple Confinement Barriers and Systems 12.3-6 12.3.3.3 Protection by Equipment and Instrumentation Selection 12.3-6 12.3.3.4 Nuclear Criticality Safety 12.3-6 12.3.3.5 Radiation Protection 12.3-12 12.3.3.6 Fire and Explosions Protection 12.3-12 12.3.3.7 Materials Handling and Storage 12.3-13 12.3.3.8 Industrial and Chemical Safety 12.3-13 12.3.4 CLASSIFICATION OF STRUCTURES, COMPONENTS, AND SYSTEMS 12.3-13 12.3.5 DECOMMISSIONING CONSIDERATIONS 12.3-13 12.3.6

SUMMARY

OF DESIGN CRITERIA 12.3-13 12.4 INSTALLATION DESIGN 12.4-1 12.5 OPERATION SYSTEMS 12.5-1 12.6 SITE GENERATED WASTE CONFINEMENT AND MANAGEMENT 12.6-1 CHAPTER 12 NUHOMS-32P DRY SHIELDED CANISTER TABLE OF CONTENTS PAGE CALVERT CLIFFS ISFSI USAR 12-ii Rev. 19 12.7 RADIATION PROTECTION 12.7-1 12.7.1 ENSURING THAT THE OCCUPATIONAL RADIATION EXPOSURES ARE AS LOW AS REASONABLY ACHIEVABLE 12.7-1 12.7.1.1 Policy Considerations 12.7-1 12.7.1.2 Design Considerations - NUHOMS-32P DSC 12.7-1 12.7.1.3 Operational Considerations 12.7-2 12.7.2 RADIATION SOURCES - NUHOMS-32P 12.7-2 12.7.2.1 Characterization of Sources 12.7-2 12.7.2.2 Airborne Radioactive Material Sources 12.7-3 12.7.3 RADIATION PROTECTION DESIGN FEATURES - NUHOMS-32P 12.7-3 12.7.3.1 Installation Design Features 12.7-3 12.7.3.2 Shielding 12.7-3 12.7.3.3 Ventilation 12.7-3 12.7.3.4 Area Radiation and Airborne Radioactivity Monitoring Instrumentation 12.7-3 12.7.4 ESTIMATED ON-SITE COLLECTIVE DOSE ASSESSMENT 12.7-3 12.7.4.1 Operational Exposure 12.7-3 12.7.4.2 Storage Term Exposure 12.7-3 12.7.5 HEALTH PHYSICS PROGRAM 12.7-3 12.7.6 ESTIMATED OFF-SITE COLLECTIVE DOSE ASSESSMENT 12.7-3 12.7.6.1 Effluent and Environmental Monitoring Program 12.7-3 12.7.6.2 Analysis of Multiple Contribution 12.7-4 12.7.6.3 Estimated Dose Equivalents 12.7-4 12.7.6.4 Liquid Release 12.7-4 12.8 ACCIDENT ANALYSIS - NUHOMS-32P 12.8-1 12.8.1 NORMAL AND OFF-NORMAL OPERATIONS 12.8-1 12.8.1.1 Normal Operation Structural Analysis 12.8-1 12.8.1.2 Off-Normal Load Structural Analysis 12.8-4 12.8.1.3 Thermal Hydraulic Analysis 12.8-6 CHAPTER 12 NUHOMS-32P DRY SHIELDED CANISTER TABLE OF CONTENTS PAGE CALVERT CLIFFS ISFSI USAR 12-iii Rev. 19 12.8.2 ACCIDENTS 12.8-9 12.8.2.1 Loss of Air Outlet Shielding 12.8-10 12.8.2.2 Tornado Winds/Tornado Missile 12.8-10 12.8.2.3 Earthquake 12.8-10 12.8.2.4 Flood 12.8-13 12.8.2.5 Cask Drop 12.8-13 12.8.2.6 Lightning 12.8-18 12.8.2.7 Blockage of Air Inlets and Outlets 12.8-18 12.8.2.8 Dry Shielded Canister Leakage 12.8-19 12.8.2.9 Accidental Pressurization of Dry Shielded Canister 12.8-19 12.8.2.10 Forest Fire 12.8-20 12.8.2.11 Liquified Natural Gas Plant or Pipeline Spill or Explosion 12.8-21 12.8.2.12 Load Combinations 12.8-21 12.8.2.13 Other Event Considerations 12.8-21 12.8.3 SITE CHARACTERISTICS AFFECTING SAFETY ANALYSIS 12.8-22 12.9 CONDUCT OF OPERATIONS 12.9-1 12.10 OPERATING CONTROLS AND LIMITS 12.10-1 12.11 QUALITY ASSURANCE 12.11-1 12.12 REFERENCES 12.12-1 CHAPTER 12 NUHOMS-32P DRY SHIELDED CANISTER LIST OF TABLES TABLE PAGE CALVERT CLIFFS ISFSI USAR 12-iv Rev. 19 12.3-1 NUHOMS-32P DRY SHIELDED CANISTER DIMENSIONS 12.3-14 12.3-2 DESIGN PARAMETERS FOR CRITICALITY ANALYSIS OF THE NUHOMS-32P DSC 12.3-15 12.3-3 NUHOMS-32P

SUMMARY

OF DESIGN CRITERIA FOR NORMAL OPERATING CONDITIONS 12.3-17 12.3-4 NUHOMS-32P

SUMMARY

OF DESIGN PARAMETERS FOR OFF-NORMAL OPERATING CONDITIONS 12.3-20 12.3-5 NUHOMS-32P

SUMMARY

OF DESIGN CRITERIA FOR ACCIDENT CONDITIONS 12.3-21 12.3-6 NUHOMS-32P DSC DESIGN LOAD COMBINATIONS 12.3-24 12.7-1 NUHOMS-32P SHIELDING ANALYSIS RESULTS NOMINAL DOSE RATES (mrem/hr) 12.7-5 12.8-1 NUHOMS-32P DRY SHIELDED CANISTER ENVELOPING LOAD COMBINATION RESULTS FOR NORMAL AND OFF-NORMAL LOADS (ASME Service Levels A and B) 12.8-23 12.8-2 NUHOMS-32P DRY SHIELDED CANISTER ENVELOPING LOAD COMBINATION RESULTS FOR ACCIDENT LOADS (ASME Service Level C) 12.8-24 12.8-3 NUHOMS-32P DRY SHIELDED CANISTER ENVELOPING LOAD COMBINATION RESULTS FOR ACCIDENT LOADS (ASME Service Level D) 12.8-25 12.8-4 NUHOMS-32P DRY SHIELDED CANISTER SUPPORT ASSEMBLY ENVELOPING LOAD COMBINATION RESULTS 12.8-26 CHAPTER 12 NUHOMS-32P DRY SHIELDED CANISTER LIST OF FIGURES FIGURE CALVERT CLIFFS ISFSI USAR 12-v Rev. 15 12.3-1 NUHOMS-32P DSC KENO V.a CRITICALITY MODEL

CHAPTER 12 NUHOMS-32P DRY SHIELDED CANISTER LIST OF ACRONYMS CALVERT CLIFFS ISFSI USAR 12-vi Rev. 15 ACI American Concrete Institute AISC American Institute of Steel Construction ANSI American National Standards Institute ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials B&PV Boiler and Pressure Vessel CCNPP Calvert Cliffs Nuclear Power Plant CE Combustion Engineering, Inc.

CFR Code of Federal Regulations CSAS25 Criticality Safety Analysis Sequence No. 25 DSC Dry Shielded Canister HSM Horizontal Storage Module ISFSI Independent Spent Fuel Storage Installation NUHOMS Nutech Horizontal Modular Storage TR Topical Report USAR Updated Safety Analysis Report USL Upper Subcriticality Limit VAP Value Added Pellet CALVERT CLIFFS ISFSI USAR 12.1-1 Rev. 15 12.0 NUHOMS-32P DRY SHIELDED CANISTER An evaluation of the Nutech Horizontal Modular Storage (NUHOMS)-32P Dry Shielded Canister (DSC) used in the NUHOMS dry storage system is presented in this Chapter. Chapter 1 is revised to include information for both the NUHOMS-24P and NUHOMS-32P DSCs. Chapters 2 through 11 primarily apply to the NUHOMS-24P DSC, whereas Sections 12.2 through 12.11 provide the same information as it applies to the NUHOMS-32P DSC.

General references are identified throughout the body of this chapter, and are listed in Section 12.12. General references are intended to provide background information or additional detail that the reader may refer to in order to learn more about a particular topic presented in this document, but are not considered part of the Updated Safety Analysis Report (USAR). A referenced document shall be considered to be a part of the USAR only if it is clearly annotated as being "incorporated by reference" in Chapter 12 of this report. Documents that are incorporated by reference are subject to the same administrative controls and regulatory requirements as the USAR.

12.1 INTRODUCTION

AND GENERAL DESCRIPTION OF INSTALLATION The introduction and general description of the NUHOMS-32P is integrated into Chapter 1.

CALVERT CLIFFS ISFSI USAR 12.2-1 Rev. 15 12.2 SITE CHARACTERISTICS The Calvert Cliffs Independent Spent Fuel Storage Installation (ISFSI) site characteristics are discussed in Chapter 2. The evaluation presented in Chapter 2 is not affected by the addition of the NUHOMS-32P DSC as part of the NUHOMS System.

CALVERT CLIFFS ISFSI USAR 12.3-1 Rev. 15 12.3 PRINCIPAL DESIGN CRITERIA 12.3.1 PURPOSE OF THE CALVERT CLIFFS INDEPENDENT SPENT FUEL STORAGE INSTALLATION Information contained in Section 3.1 is applicable to the NUHOMS-32P DSC design as well. 12.3.2 STRUCTURAL AND MECHANICAL SAFETY CRITERIA Compared to the existing NUHOMS-24P DSC, the main difference in the principal design parameters for the NUHOMS-32P DSC consists of an increase in canister weight, radiological source, and decay heat due to the addition of eight more fuel assemblies plus modifications to the DSC basket assembly. The NUHOMS-32P DSC is handled and stored in the same manner as the NUHOMS-24P DSC. The environmental conditions and natural phenomena for a NUHOMS-32P DSC are the same as those described in Section 3.2.

12.3.2.1 Tornado Wind and Tornado-Generated Missile Loadings The principal tornado wind and tornado-generated missile loading criteria are not dependent on the type of DSC employed and, therefore, are the same for the NUHOMS-32P and NUHOMS-24P DSCs. The tornado wind and tornado-generated missile loading criteria are described in Section 3.2.1. They are based on Reference 3.1, which applies to the NUHOMS-24P DSC, but are applicable to the NUHOMS-32P DSC as well.

Evaluation of the NUHOMS-32P DSC for tornado wind and tornado generated missiles is presented in Section 12.8.2.2.

12.3.2.2 Water Level (Flood) Design As stated in Section 3.2.2, the Calvert Cliffs ISFSI is not subject to flooding. Therefore, the type of DSC used in the horizontal storage modules (HSMs) is independent of the flood water level.

12.3.2.3 Seismic Design The principal seismic loading criteria are not dependent on the type of DSC employed and, therefore, are the same for the NUHOMS-32P and NUHOMS-24P DSCs. The seismic loading criteria are described in Section 3.2.3.

Evaluation for the use of the NUHOMS-32P DSCs for seismic loading is presented in Section 12.8.2.3.

12.3.2.4 Snow and Ice Loadings The snow and ice loads are the same for the NUHOMS-32P and NUHOMS-24P DSCs and are described in Section 3.2.4.

12.3.2.5 Combined Load Criteria 12.3.2.5.1 HSM The Calvert Cliffs site-specific load combinations matrix and design criteria for the HSM storing the NUHOMS-32P and CALVERT CLIFFS ISFSI USAR 12.3-2 Rev. 15 NUHOMS-24P DSCs are the same and are presented in Section 3.2.5.1 and Table 3.2-2.

Structural evaluation of the HSM for the NUHOMS-32P DSC is presented in Section 12.8.

12.3.2.5.2 NUHOMS-32P DSC The Calvert Cliffs site-specific load combinations for the NUHOMS-32P DSC are presented in Table 12.3-6.

Structural evaluation of the NUHOMS-32P DSC basket assembly is presented in Section 12.8.

12.3.2.5.3 NUHOMS Transfer Cask The same transfer cask is used for the NUHOMS-32P and NUHOMS-24P DSCs. The Calvert Cliffs site-specific load combinations and allowable stress criteria for the transfer cask are the same as those presented in Section 3.2.5.3.

Structural evaluation of the transfer cask for the NUHOMS-32P DSC is presented in Section 12.8.

12.3.2.5.4 NUHOMS System Transfer Equipment The load combinations and acceptance criteria for the transfer equipment are not affected by the use of the NUHOMS-32P DSC and are the same as those in Section 3.2.5.4.

12.3.2.6 Weld Requirements The NUHOMS-32P DSC shell assembly welded joint details are the same as for the NUHOMS-24P DSC shell assembly (References 12.35 through 12.46). The NUHOMS-32P DSC basket structure welded joint details are shown in References 12.35 through 12.46. Full penetration welds in the DSC basket assembly are examined by progressive penetrant test examination in accordance with the requirements of paragraph NG-5231 of the American Society of Mechanical Engineers (ASME) Code Section III, Subsection NG (References 12.26 and 12.41).

Weld analysis results for the NUHOMS-32P DSC and the transfer cask are presented below.

DSC Shell and Basket Assembly Welds (Reference 12.22)

• Shell Welds The DSC Shell can be manufactured from pieces of cylindrical plates. These shell pieces are welded together by full penetration welds, both longitudinally and circumferentially. The weld is also 100% radiographed.

CALVERT CLIFFS ISFSI USAR 12.3-3 Rev. 15

• Support Ring Welds The Support Ring consists of a 1.75" high tapered ring and a 0.25" high plate that are welded to the DSC shell. When the Support Ring is loaded, the 1/4" fillet weld between the ring and plate is in compression, and the upper ring will bear against the lower plate. The welds that require analysis are the two 1/4" groove welds at the top and bottom of the Support Ring weldment. The Support Ring supports the weight of the top lead shield plug assembly, conservatively assumed to weigh 8,000 lbs. The Support Ring self-weight is an additional 300 Ibs. The critical loading condition occurs during the 75g bottom end vertical drop. The Service Level D allowable weld stress at the DSC design temperature of 380

°F is 22.55 ksi. The calculated weld shear and tensile stress is within allowable limits.

• Lead Shield Plug Assembly Welds Each of the four top shield plug assembly round bars are welded to the inner cover plate by a 5/16" fillet weld. The 1.5" diameter bars are loaded only during preliminary handling of the top shield plug assembly. In all other cases, the weld is in compression. The weight of the top shield plug assembly is conservatively 8,000 lbs. The allowable stress at room temperature is 10.0 ksi. Conservatively assuming that two of the four plugs carry the load, the calculated stress on the weld is within the allowable limits.

• Top Shield Plug Pressure Boundary Weld The inner cover plate on the top shield plug is welded to the DSC shell by a 3/16" groove weld. The highest load on the weld occurs during the 100 psig accident pressure load case. The pressure is applied to the top inner cover plate and loads the weld in pure shear. The Service Level D allowable weld stress at 380

°F is 22.55 ksi. The calculated stress is within allowable limits.

• Top Cover Plate Weld The top cover plate is welded to the DSC by a groove weld, which has a 1/2" minimum throat. The maximum load occurs during the bottom end drop, where the weld is loaded by the weight of the outer cover plate at 75g. The Service Level D allowable weld stress at 380

°F is 22.55 ksi. The calculated shear stress on the weld is within allowable limits.

• Bottom Cover Plate Weld The bottom end structural weld is a full penetration weld and is 100% radiographed.

• Bottom Lead Casing Plate Welds The bottom lead casing plate is welded to the lead casing shell plate by a 1/4" groove weld. During a lifting of the DSC into the transfer cask, the shearing load on this weld is equal to the dead weight of the bottom shield plug and the bottom lead liner plate (conservatively 7,500 Ibs). The CALVERT CLIFFS ISFSI USAR 12.3-4 Rev. 15 allowable stress at room temperature is 10.0 ksi. The calculated weld shear stress is within allowable limits.

The lead casing shell is welded to the bottom cover plate by a 1/4" groove weld on the outside, and a 1/8" fillet weld on the inside. These welds carry the same loads as the 1/4" groove weld between the lead liner plate and the lead casing shell and are acceptable.

The 5/16" bottom weld applied to the plug post and bottom cover plate interface is a non-structural weld.

• Grapple Ring Assembly Welds The grapple ring is welded to the grapple ring shell by a full penetration groove weld.

The grapple ring assembly plate is welded to the grapple ring shell on the inside by a 3/8" groove weld with a 1/8" fillet weld, and on the outside by a 1/4" fillet weld. These welds carry some of the lead shield during a vertical lift. The 1/4" groove weld is adequate under this loading condition.

The grapple ring shell is welded to the inner cover plate by a full penetration weld with a 1/8" fillet cover weld.

A 1/8" cover fillet weld over a 3/8" groove weld is applied to the outside of the grapple ring shell and the bottom cover plate interface. Conservatively ignoring the cover fillet weld, the 3/8" groove weld is loaded by a maximum of 95,000 lbs when the DSC is pushed by the ram assembly. The Service Level A allowable stress at 380

°F is 9.48 ksi. The calculated total shear stress on the weld is within the allowable limit.

• Vent and Siphon Port Welds The plates welded to the vent and siphon ports form part of the pressure boundary. The plates are 3.40" in diameter, and are welded to the drain and fill ports by 3/16" groove welds. Under worst case conditions, the plates carry a pressure of 100 psig. The Service Level D allowable weld stress at 350

°F is 22.55 ksi. The calculated weld stress is within the minimum allowable stress.

• Guide Sleeve Fusion Weld The weld strength of each fusion weld nugget connecting the fuel compartment guide sleeves of the DSC basket structure is required to be determined by shear tests using te st specimens made from production material and shall have a minimum capacity of 16.0 kips at 70

°F (Reference 12.41). The allowable design strength of the fusion weld is established by applying a safety factor of 2 and correction for the 600

°F design temperature (Reference 12.28).

Correcting for reduction in the weld allowable stress from 75 ksi at room temperature to 63.4 ksi at 600

°F, the minimum provided weld capacity at CALVERT CLIFFS ISFSI USAR 12.3-5 Rev. 15 600°F is 15.5 kips. The calculated load in the fusion weld connection of the fuel compartment guide sleeves is within the minimum allowable stress.

Transfer Cask Welds (Reference 12.25)

• Weld At Inner Bottom Cover Plate/Ram Access Penetration Ring This weld is analyzed for the critical lift handling condition and the vertical bottom drop accident condition.

- Critical Lift Handling Condition The inner bottom cover plate supports the weight of the DSC, conservatively taken to be 95 kips (Reference 12.34), during the critical lift condition. The load is increased by 15% to account for motion loads. The fuel and DSC are considered to load the cask base plate as a uniform pressure load. The remaining weight of the DSC, which includes the basket, shell, and top plate are conservatively represented as a pressure load that decreases toward the center of the plate. The calculated fillet weld size required is 0.35" (Reference 12.25). The existing 3/8" minimum weld size is adequate.

- Vertical Drop Condition (Level D) The weld stress for this condition is based on the results of the calculation for the NUHOMS-24P DSC (Reference 12.50) for the transfer cask vertical bottom drop accident and scaling up the stress by a factor of 1.1 to reflect the weight increase of the NUHOMS-32P DSC. The weld stress (using stainless steel allowables) is within the minimum allowable stress of 22.4 ksi.

• Weld at Cask Inner Shell Plate/ Top Flange Ring The weld stress is based on the results of calculation for the NUHOMS-24P DSC (Reference 12.50) for transfer cask vertical bottom drop accident and scaling up by a factor of 1.1 the stress to reflect the weight increase of the NUHOMS-32P DSC. The calculated weld stress is less than the allowable stress of 22.4 ksi.

The analyses described above demonstrate that the important-to-safety components of the Calvert Cliffs ISFSI with NUHOMS-32P DSC are adequate to withstand all postulated loads and loading combinations.

12.3.3 SAFETY PROTECTION SYSTEMS 12.3.3.1 General Section 3.3 discusses the Calvert Cliffs ISFSI design for the safe and secure long-term containment and storage of spent fuel. The NUHOMS-32P DSC is designed for storage of spent nuclear fuel as described in Section 3.3.1 and in the following subsections.

CALVERT CLIFFS ISFSI USAR 12.3-6 Rev. 15 12.3.3.2 Protection by Multiple Confinement Barriers and Systems The NUHOMS-32P DSC provides confinement of the spent fuel similar to the NUHOMS-24P DSC. Sealing of the NUHOMS-32P DSC is leak tested in accordance with American National Standards Institute (ANSI) N14.5 after loading and sealing the canister, as described in Section 3.3.2.

Containment of radioactive material associated with spent fuel assemblies is provided by fuel cladding, the DSC stainless steel shell and double seal welded primary and secondary closures. As described in Section 3.3.2, there are no credible events that will breach a DSC to provide a possible leakage path to the environment.

12.3.3.3 Protection by Equipment and Instrumentation Selection The protection by equipment and instrum entation is not impacted by the use of the NUHOMS-32P DSC, and remains the same as presented in Section 3.3.3.

12.3.3.4 Nuclear Criticality Safety The NUHOMS-32P DSC internals are designed to provide nuclear criticality safety during all phases of NUHOMS system operations and storage, including wet loading operations and postulated accident conditions. The Calvert Cliffs site-specific NUHOMS-32P DSC design satisfies the requirements of 10 Code of Federal Regulations (CFR) 72.124 for normal, off-normal, and accident conditions.

12.3.3.4.1 Control Methods for Prevention of Criticality Criticality control is provided during the transfer cask fuel loading, DSC drying and sealing (wet conditions), and the transfer and storage phases (dry conditions). Control methods for the prevention of criticality under wet conditions consist of the physical properties of the fuel, fixed neutron absorbers in the NUHOMS-32P basket, 2,450 ppm soluble boron in the spent fuel pool water, and Calvert Cliffs' administrative controls for fuel identification, verification, and handling.

Rigorous measures are taken to exclude the possibility of introducing moderator into the DSC cavity during the dry operations of transfer and storage. Prior to these operations, the DSC is vacuum dried, backfilled with helium, double seal welded, and helium leak tested to assure weld integrity. Therefore, under normal operating conditions there is no possibility of a criticality incident. Since the transfer cask and HSM are designed to provide adequate drop and/or missile protection for the DSC, there is no credible accident scenario which would result in the possibility of the entrance of a moderator into the DSC; nor is there a credible accident scenario which would prohibit the canister from being opened and re-flooded.

CALVERT CLIFFS ISFSI USAR 12.3-7 Rev. 15 12.3.3.4.2 Design Parameters for Criticality Model The design basis criticality analysis uses design parameters for Combusting Engineering, Inc. (CE) design 14x14 non-Value Added Pellet (non-VAP) fuel assemblies containing UO 2 enriched up to 4.5 wt% U 235 with geometry and fuel characteristics as shown in Table 3.3-3. The nominal dimensions of the NUHOMS-32P DSC are provided in Table 12.3-1. The geometry is illustrated in Figure 12.3-1. A summary of the design parameters for the criticality analysis is presented in Table 12.3-2.

Additional analyses are performed for fuel misloads and accidents. The design parameters for misloads and accidents are also presented in Table 12.3-2.

12.3.3.4.3 Criticality Analysis Methods Effective neutron multiplication factors, k eff, are calculated using the Criticality Safety Analysis Sequence No. 25 (CSAS25), of the SCALE-4.4 package of codes, and the 44 Group ENDF-V cross-section library. The CSAS25 control module allows simplified data input to the functional modules BONAMI-S, NITAWL-S, and KENO V.a. These modules process the required cross-sections and calculate the k eff of the system. BONAMI-S performs resonance self-shielding calculations for nuclides that have Bondarenko data associated with their cross sections. NITAWL-S applies a Nordheim resonance self-shielding correction to nuclides having resonance parameters. Finally, KENO V.a calculates the keff of a three-dimensional system. A sufficiently large number of neutron histories are run so that the standard deviation is below 0.0010 for all calculations.

The final keff that is calculated represents the maximum value of the effective multiplication factor with a 95% probability at a 95% confidence level (95/95). The "worst case" k eff values from the CSAS25 output are adjusted for uncertainty, such that: k eff = k keno + 2keno A series of 121 benchmark criticality calculations are documented in Reference 12.6. These calculations assume unirradiated fuel in the criticality analysis and use the SCALE-4.4 computer code package. The upper subcriticality limit (USL), as described in Section 4 of NUREG/CR-6361 (Reference 12.5), is determined using the results of these 121 benchmark calculations. The benchmark problems used to perform this verification are representative of benchmark arrays of commercial light water reactor fuels with the following characteristics:

• water moderation CALVERT CLIFFS ISFSI USAR 12.3-8 Rev. 18

• boron neutron absorbers

• unirradiated light water reactor type fuel (no fission products or "burnup credit")

• near room temperature (vs. reactor operating temperature)

• close reflection

• uranium oxide fuel The 121 uranium oxide experiments are chosen to model a wide range of uranium enrichments, fuel pin pitches, assembly separation, water/fuel ratio, concentration of soluble

boron and control elements in order to test the codes ability to

accurately calculate k eff. The minimum value of the USL from Reference 12.6 over the parameter range (in this case, the assembly separation distance) is 0.9422. This USL value (0.9422) is based on a methodology bias and an

administrative 5% margin on criticality. That is, keff < USL, ensures that k eff is less than 0.95 (with 95% probability and 95% confidence) when bias and uncertainty are taken into account.

For the criticality analyses, the criticality limits are shown in the following equation:

k eff = (k keno + 2keno) 0.9422 12.3.3.4.4 Normal Conditions (Reference 12.7) The calculated normal condition, "worst-case," reactivity (maximum k eff) of a fully loaded Calvert Cliffs NUHOMS-32P DSC is 0.9412. This is below the USL (0.9422), thus confirming that the "worst case" k eff is 0.95. It conservatively includes allowances for uncertainties due to fuel positioning, basket rail modeling, compartment tube dimensions, poison plate thickness, and optimum moderator density. The "worst case" configuration includes the following:

• no credit for burnable absorbers in the fuel rods (e.g., erbia, etc.),

• fuel is unirradiated,

• the maximum uniform enrichment, 4.5 wt% U 235 , for all 32 assemblies,

• an "inward" loading of all the 32 CE 14x14 fuel assemblies (i.e., all fuel assemblies are shifted toward the center of the DSC),

• credit for 90%

of the absorber material (B

10) in the fixed neutron absorbers in the NUHOMS-32P basket assembly,

• a minimum compartment tube dimension of 8.47",

• an internal moderator (soluble boron at 2,450 ppm) density of 70%,

CALVERT CLIFFS ISFSI USAR 12.3-9 Rev. 19

• an external (to the DSC and internal to the transfer cask) moderator (pure water) density of 10%.

To evaluate assemblies containing vacancies and inert stainless steel rods, Reference 12.58 utilizes the same methodology as Reference 12.7 to analyze criticality under normal conditions. No changes were made to the computer code software and version or to the characteristics of the KENO V.a models other than the changing of the fuel array input to include vacancies and inert stainless steel pins. The material specification used for the stainless steel rods is consistent with the methodology in Reference 12.7. The calculated 95/95 (95% probability and 95% confidence) k eff for all cases analyzed are below the USL of 0.9422.

12.3.3.4.5 Off-Normal Conditions (Reference 12.8) Four postulated off-normal conditions are analyzed:

• The misloading of up to eight VAP fuel assemblies into the DSC with an initial enrichment of 5.0 wt% U 235 ,

• Cask Drop Accidents,

• B 10 Absorber Plates at Minimum Thickness, and

• Optimum Moderator Density.

These analyses confirm that the off-normal conditions will not result in a DSC storage array with a reactivity higher than the USL of 0.9422.

Misloading of VAP Assemblies (5 wt% U 235) Value added pellet fuel is not currently licensed for storage in NUHOMS-32P canisters. However because it resides in the spent fuel pool, a misload of VAP fuel into a canister was analyzed. The criticality analysis for the fuel misloads demonstrates that a maximum of two VAP fuel assemblies at

an enrichment of 5.0 wt% U 235 can be misloaded and transferred under optimum moderator density conditions. The k eff for this case is 0.9377. The analysis also demonstrates that a maximum of eight VAP fuel assemblies at an enrichment of 5.0 wt% U 235 can be misloaded under fully flooded conditions (full moderator density). The k eff for this case is 0.9385.

Reference 12.58 shows a clear and expected trend of lower k eff with increasing number of fuel rods removed. This trend applies to the case of accidental misloading of VAP assemblies as well. Therefore, there is no impact on the misload criticality analysis results as presented above.

Cask Drop Accidents The criticality analysis for the cask drop accidents demonstrates that the most reactive configuration is the triple

CALVERT CLIFFS ISFSI USAR 12.3-10 Rev. 19 contingency accident involving fuel damage, optimum pitch (due to grid deformation), and optimum moderator density.

For the helium-moderated system, the k eff is 0.5720 which is below the USL (0.9422). For the borated water moderated system, the maximum k eff is 0.9413, which is also below the USL (0.9422).

Reference 12.59 determines the structural adequacy of a fuel assembly containing vacancies following a cask drop event. The results show that the bending stresses are acceptable provided that no more than two vacancies are in any one column or row of the fuel assembly. It is not required that the vacancies be adjacent. The criticality analysis of Reference 12.58 has postulated that an assembly containing numerous vacancies can be postulated to be rearranged into a 13x13 array if grid spacer integrity is compromised. Reference 12.58 has analyzed a 13x13 array with maximum pitch separation and has determined that the k eff of such a scenario is 0.9012. The most reactive case, with vacancies, was found to be when one vacancy was present in each of the four center assemblies. The assemblies were modeled in the standard 14x14 array and at optimum fuel rod pitch; the resulting k eff is 0.9390. Both of these scenarios results in a k eff less than the bounding analysis which finds the keff to be 0.9413. All of these values are less than the USL of 0.9422.

B10 Poison Plate Thickness Variation The criticality analysis for sensitivity to B 10 absorber plate thickness demonstrates that there is enough conservatism in

the plate loading of 10.0 mg B 10/cm 2 to offset changes in reactivity due to a reduction in thickness. Credit is taken for

90% of the B 10 loading in the analysis. For the normal case, with an absorber plate thickness of 0.04", the maximum k eff is calculated to be 0.9412 (Reference 12.7). For the "worst case," with a B 10 loading of 8.964 mg/cm 2, a thickness of 0.035", and optimum moderator density, the k eff, is calculated to be 0.9357 (Reference 12.8).

Section 12.3.3.4.7 has a detailed discussion on poison plate acceptance testing.

Optimum Moderation Since all reported reactivities include an allowance for optimum moderator density, and all reported reactivities are less than the USL, a criticality event due to moderator density alone is not credible. For a misload of two VAP assemblies, optimum moderator density will not result in criticality, provided that at least 2,450 ppm of boron is present in the water inside the DSC. Therefore subcriticality is assured, even in the event that a flooded DSC remains out of the pool long enough for boiling to occur.

CALVERT CLIFFS ISFSI USAR 12.3-11 Rev. 19 12.3.3.4.6 Criticality Analysis Method Verification The analysis method which ensures a subcriticality margin of greater then 5% under all normal conditions uses the CSAS25, of the SCALE-4.4 package of codes, and the 44 Group ENDF-V cross-section library.

A series of 121 benchmark criticality calculations are documented in Reference 12.6. These calculations assume unirradiated fuel in the criticality analysis and use the SCALE-4.4 computer code package to demonstrate its applicability and to establish methods bias and variability.

12.3.3.4.7 B 10 Poison Plate Testing Description The poison plates consist of wrought aluminum containing boron, which is isotopically enriched to approximately 95 wt%

B 10. Because of the negligibly low solubility of boron in solid aluminum, the boron appears entirely as discrete second phase particles of AlB 2 in the aluminum matrix. The effect on the properties of the matrix aluminum alloy are those typically associated with a uniform fine (1-10 micron) dispersion of an inert equiaxed second phase.

The nominal plate thickness is 0.04".

The nominal boron concentration is 3.9 wt%. The design minimum B 10 areal density is 0.0100g B 10/cm 2.

Functional Requirements of Poison Plates The poison plates serve as a neutron absorber for criticality control and as a heat conduction path. The NUHOMS-32P DSC safety analysis does not rely upon their mechanical strength. The radiation and temperature environment in the cask is not severe enough to damage the aluminum matrix that retains the boron-containing particles. To assure performance of the plates' important-to-safety functions, the critical variables that need to be verified are thermal

conductivity and B 10 areal density.

Borated Aluminum Test Coupon and Lot Definitions Test coupons will be taken so that there is at least one coupon contiguous with each plate. These coupons will be used for neutron transmission and thermal conductivity testing.

A lot is defined as all the plates produced from a single cast ingot, or all the plates produced from a single heat.

CALVERT CLIFFS ISFSI USAR 12.3-12 Rev. 19 Thermal Conductivity Testing of Poison Plates The poison plate material is qualification-tested to verify that the thermal conductivity equals or exceeds the design requirements.

Testing may be by American Society for Testing and Materials (ASTM) E1225 (Reference 12.51), ASTM E1461 (Reference 12.52), or equivalent method.

B10 Areal Density Testing of Poison Plates The testing program for the NUHOMS-32P DSC poison plates meet the requirements of NUREG/CR-5661 (Reference 12.53).

The effective B 10 content is verified by neutron transmission testing of the coupons. The transmission through the coupons is compared with transmission through calibrated standards. The neutron transmission testing measurements are taken using a collimated neutron beam. The neutron transmission test procedure includes provisions to vary the selected measurement location along the coupon length.

The acceptance criterion for neutron transmission testing is that the B 10 areal density, minus 3 based on the number of neutrons counted for that measurement, must be greater than or equal to the minimum value 0.0100g B 10/cm 2.

Macroscopic uniformity of B 10 distribution is verified by neutron radioscopy/radiography of the coupons. The acceptance criterion is that there is uniform luminance across the coupon. This inspection shall cover the entire coupon. If a coupon fails this test, the associated plate is rejected.

In addition, a statistical analysis of the neutron transmission results for all plates in a lot is performed. This analysis shall demonstrate, using a one-sided tolerance limit factor for a normal distribution with at least 95% probability, the areal density is greater than or equal to the specified minimum

value of 0.0100g B 10/cm 2 with 95% confidence level.

12.3.3.5 Radiological Protection The discussion presented in Section 3.3.5 is not affected by the addition of the NUHOMS-32P DSC to the NUHOMS System. See Section 12.7 for additional discussion on radiation protection design considerations for the NUHOMS-32P DSC.

12.3.3.6 Fire and Explosions Protection The discussion presented in Section 3.3.6 is applicable to NUHOMS-32P DSC. The effects of a forest fire around the facility are discussed in Section 12.8.2.10.

CALVERT CLIFFS ISFSI USAR 12.3-13 Rev. 19 12.3.3.7 Materials Handling and Storage The evaluation presented in Section 3.3.7 is not affected by the addition of the NUHOMS-32P DSC to the NUHOMS system, with the exception of peak cladding temperatures which are higher than those of the NUHOMS-24P DSC. For long-term storage, HSM passive ventilation maintains the maximum normal operating fuel clad temperature at 620

°F or less (assuming 103

°F ambient temperature) as documented in Reference 12.1. During short-term conditions, such as DSC draining and drying, transfer of the DSC to/from the HSM and off-normal and accident temperature excursions (References 12.1, 12.2, 12.3, and 12.4), the fuel cladding temperature maximum value is 838

°F (Reference 12.9), which is significantly less than the maximum allowable value of 1,058

°F. 12.3.3.8 Industrial and Chemical Safety The discussion presented in Section 3.3.8 is not affected by the addition of the NUHOMS-32P DSC to the NUHOMS System.

12.3.4 CLASSIFICATION OF STRUCTURES, COMPONENTS, AND SYSTEMS The discussion presented in Section 3.4 is not affected by the addition of the NUHOMS-32P DSC to the NUHOMS System.

12.3.5 DECOMMISSIONING CONSIDERATIONS The discussion presented in Section 3.5 is not affected by the addition of the NUHOMS-32P DSC to the NUHOMS System.

12.3.6

SUMMARY

OF DESIGN CRITERIA Tables 12.3-3 to 12.3-5 provided a summary of the design criteria information for the normal, off-normal, and accident conditions for the NUHOMS-32P DSCs, respectively.

CALVERT CLIFFS ISFSI USAR 12.3-14 Rev. 19 TABLE 12.3-1 NUHOMS-32P DRY SHIELDED CANISTER DIMENSIONS GEOMETRY DESCRIPTION NOMINAL DIMENSIONS (inches) Guide Sleeve Inside Diameter 8.50 Guide Sleeve Thickness 0.1874 Center to Center Spacing 9.125 Stainless Steel Strip Thickness 0.25 Aluminum + Poison Plate Thickness 0.25 Basket Assembly Length 158.0 max. DSC Shell Outside Diameter 67.25 DSC Shell Inside Diameter 66.0 DSC Shell Length (with grapple ring) 176.5 DSC Shell Thickness 0.625 Top Shield Plug Thickness 6.25 Top Cover Plate Thickness 1.25 DSC Lead Shielding Thickness

• Top Shield Plug 4.0 min.

• Bottom Shield Plug 4.25 min.

Vent / Siphon Port Tube Inside Diameter 1.05 CALVERT CLIFFS ISFSI USAR 12.3-15 Rev. 19 TABLE 12.3-2 DESIGN PARAMETERS FOR CRITICALITY ANALYSIS OF THE NUHOMS-32P DSC PARAMETERS DESIGN VALUE FUEL ASSEMBLIES Number/Type 32/CE design 14x14 Rod Array 14x14 (d)Number of Fuel Rods 176 (c) Number of Control Rod Guide Tubes 5 Number of Instrument Tubes 1 (1 of the 5 guide tubes) Rod Pitch (inches) 0.580 Burnup Credit Not Applicable for NUHOMS-32P DSC FISSILE CONTENT wt% U 235 4.5 max. wt% U 235 (VAP Misload) 5.0 max. FUEL PELLETS Density 96.0%

Theoretical Density (VAP Misload) 96.5% Theoretical Diameter (inches) 0.3765 (a) Diameter (inches) (VAP Misload) 0.3810 FUEL ROD CLADDING Material Zircaloy-4 Thickness (inches) 0.028 (a) Thickness (inches) (VAP Misload) 0.026 Outside Diameter (inches) 0.440 Outside Diameter (inches) (VAP Misload) 0.440 CONTROL ROD GUIDE TUBES Material Zircaloy-4 Thickness (inches) 0.040 Outside Diameter (inches) 1.115 INSTRUMENT TUBE Material Zircaloy-4 Thickness (inches) 0.040 Outside Diameter (inches) 1.115 DSC COMPARTMENTS Material Stainless Steel Thickness (inches) 0.1874 Inside Diameter (inches) 8.5 DSC POISON PLATES Number 150

Material Borated Aluminum Alloy Density (g/cm

3) 2.693 Thickness (inches) 0.04 B 10 Areal density (mg/cm

2) 10 Location See Figure 12.3-1 CALVERT CLIFFS ISFSI USAR 12.3-16 Rev. 19 TABLE 12.3-2 DESIGN PARAMETERS FOR CRITICALITY ANALYSIS OF THE NUHOMS-32P DSC PARAMETERS DESIGN VALUE DSC FILL MATERIAL Material (wet) Borated Water (2,450 ppm min) Moderator Density (wet) 0.01% to 100% Material (dry) helium Moderator Density (dry) 1.785E-04 g/cm 3 /atm DSC SHELL Material Stainless Steel Thickness (inches) 0.625 Outside Diameter (inches) 67.25 CASK Material Stainless Steel/Lead Thickness (inches) 6.25 (b) Outside Diameter (inches) 80.5 (b)

(a) The fuel pellet outside diameter and clad thickness varied slightly for Fuel Batches A, B, and C in Units 1 and 2. These variances do not affect the results of the design basis analysis. (b) Exclusive of the cask neutron shield. (c) Fuel Rods/Assembly (32P)

Fuel assemblies to be stored in 32P DSCs may contain up to two vacancies in any column or row; the vacancies do not need to be adjacent. Vacancies that violate this configuration are to be filled with stainless steel replacement rods. Fuel assemblies to be stored in the 32P DSC may also contain a varying number of irradiated stainless steel replacement rods depending on the rods' exposure and time of cooling as shown in Table 9.4-3. An unlimited number of unirradiated stainless steel rods is permissible. (d) Accident analyses for fuel assemblies containing vacancies considers multiple array configurations. See Reference 12.58 for details.

CALVERT CLIFFS ISFSI USAR 12.3-17 Rev. 19 TABLE 12.3-3 NUHOMS-32P

SUMMARY

OF DESIGN CRITERIA FOR NORMAL OPERATING CONDITIONS COMPONENT DESIGN LOAD TYPE REFERENCE DESIGN PARAMETERS APPLICABLE CODE HSM Dead Load TR 8.1.1.5Dead weight including loaded DSCANSI 57.9-1984 ACI 349-85 and ACI 349R-85Load CombinationUSAR Table 3.2-2 Load combination methodologyANSI 57.9-1984 Sec 6.17.1.1Design Basis

Operating

Temperature DSC with spent fuel rejecting 21.12 kW decay heat. Ambient air temperature range

-3°F to 103°F ANSI 57.9-1984Normal Handling Loads TR 8.1.1.4Hydraulic ram load: 20,000 lbANSI 57.9-1984 Snow and Ice Loads USAR 3.2.4Design load: 200 psf (included in live load)ANSI 57.9-1984 Live Loads TR 8.1.1.5Design load: 200 psfANSI 57.9-1984 Shielding USAR 4.2.3.1Contact dose rate on HSM exterior surface 20 mrem/hr. HSM door 100 mrem/hr.

ANSI 57.9-1984 DSC Dead Loads Weight of loaded DSC: 91,000 lb nominal, 95,000 lb enveloping ANSI 57.9-1984Design Basis Internal Pressure Load DSC internal pressure 10.1 psigANSI 57.9-1984 Structural Design TR Table 3.2-6 Service Level A and B ASME B&PV Code

Sec III, Div 1, NB, Class 1 Design Basis Operating

Temperature Loads DSC decay heat 21.12 kW. Ambient air temperature -3

°F to 103°F ANSI 57.9-1984 Operational HandlingUSAR Table 3.2-1 Hydraulic ram load: 20,000 lbANSI 57.9-1984 Criticality USAR 12.3.3.4 K eff less than 0.95 ANSI 57.9-1984DSC Support Assembly Dead Loads Loaded DSC + self weight: 95,000 lbANSI 57.9-1984

AISC Code CALVERT CLIFFS ISFSI USAR 12.3-18 Rev. 19 TABLE 12.3-3 NUHOMS-32P

SUMMARY

OF DESIGN CRITERIA FOR NORMAL OPERATING CONDITIONS COMPONENT DESIGN LOAD TYPE REFERENCE DESIGN PARAMETERS APPLICABLE CODE Operational HandlingUSAR 12.8.1.1.4DSC reaction load with hydraulic ram load:

20,000 lb ANSI 57.9-1984 Transfer Cask Normal Operating

Condition TR Table 3.2-8 Service Level A and B ASME B&PV Code

Sec III, Div 1, Class 2, NC-3200 Structure: Shell, Rings, etc.

Dead Loads USAR 12.8.1.1.9a) Vertical orientation, self weight + loaded DSC + water in cavity: 220,000 lb

enveloping ANSI 57.9-1984b) Horizontal orientation, self weight + loaded DSC on transfer skid: 220,000 lb enveloping ANSI 57.9-1984 Snow and Ice Loads USAR 3.2.4 External surface temperature of cask will preclude buildup of snow and ice loads when in use: 0 psf 10 CFR 72.122Design Basis

Operating

Temperature Loads Loaded DSC rejecting 21.12 kW decay heat. Ambient air temperature range -3

°F to 103°F ANSI 57.9-1984 Shielding USAR 12.7.1.2 Contact dose rate 200 mrem/hr.

ANSI 57.9-1984 Transfer Cask Upper Trunnions Operational HandlingUSAR 12.8.1.1.9a) Upper lifting trunnions while in Auxiliary Building: i) Stress must be less than yield stress for 6 times critical load of 126,500 lb/trunnion nominal ANSI N14.6-1978 USAR 12.8.1.1.9ii) Stress must be less than ultimate stress for 10 times critical load

CALVERT CLIFFS ISFSI USAR 12.3-19 Rev. 19 TABLE 12.3-3 NUHOMS-32P

SUMMARY

OF DESIGN CRITERIA FOR NORMAL OPERATING CONDITIONS COMPONENT DESIGN LOAD TYPE REFERENCE DESIGN PARAMETERS APPLICABLE CODE USAR Table 3.2-1 b) Upper lifting trunnions for on-site transfer: i) Dead Load +/- 1g vertically ii) Dead Load +/- 1g axially iii) Dead Load +/- 1g laterally iv) Dead Load (+/- 1/2g vertically +/- 1/2g axially + 1/2g laterally)

ASME B&PV Code Sec III, Div 1, Class 2, NC-3200 Lower Trunnions Operational HandlingUSAR 12.8.1.1.9Lower support trunnions weight of loaded cask during downloading and transit to

HSM ASME B&PV Code

Sec III, Div 1, Class 2, NC-3200 Shell Operational HandlingUSAR 12.8.1.1.9 Hydraulic ram load due to friction of extracting loaded DSC: 20,000 lb ANSI 57.9-1984 Bolts Normal Operation TR Table 3.2-9Service levels A, B, and C

Avg stress less than 2 S m Max stress less than 3 S m ASME B&PV Code Section III, Div 1, Class 2, NC-3200

(ASME B&PV Code-1983, with Addenda up to 1985 for HSM and Transfer Cask)

(ASME B&PV Code-1998, with Addenda up to 1999 for DSC)

CALVERT CLIFFS ISFSI USAR 12.3-20 Rev. 19 TABLE 12.3-4 NUHOMS-32P

SUMMARY

OF DESIGN PARAMETERS FOR OFF-NORMAL OPERATING CONDITIONS COMPONENT DESIGN LOAD TYPE REFERENCE DESIGN PARAMETERS APPLICABLE CODE HSM Off-Normal Temperature

-3°F and 103°F ambient temperature ANSI 57.9-1984Jammed Condition

Handling USAR 12.8.1.2.1Hydraulic ram load equal to 80,000 lbANSI 57.9-1984Load CombinationUSAR Table 3.2-2 Load combination methodologyANSI 57.9-1984 Sec 6.17.1.1 DSC Off-normal Temperature

-3°F and 103°F ambient temperature ANSI 57.9-1984 Off-normal Pressure DSC internal pressure 10.8 psigANSI 57.9-1984 Blowdown Pressure DSC internal pressure: 40.0 psig 10 CFR 72.122(b)Jammed Condition

Handling USAR 12.8.1.2.1Hydraulic ram load equal to 80,000 lbANSI 57.9-1984 Structural Design Off-Normal Conditions TR Table 3.2-6Service Level C ASME B&PV Code

Sec III, Div 1, NB, Class 1 DSC Support Jammed Handling Condition USAR 12.8.1.2.1 Hydraulic ram load: 80,000 lbANSI 57.9-1984Load Combination TR Table 8.2-11 Load combination methodologyANSI 57.9-1984 Transfer Cask Off-normal Temperature

-3°F and 103°F ambient temperature ANSI 57.9-1984Jammed Condition Handling USAR 12.8.1.2.1 Hydraulic ram load: 80,000 lbANSI 57.9-1984 Structural Design Off-Normal Conditions TR Table 3.2-8Service Level C ASME B&PV Code

Sec III, Div 1, Class 2, NC-3200 Bolts, Off-Normal Conditions TR Table 3.2-9 Service Level C Avg stress less than 2 S m Max stress less than 3 S m ASME B&PV Code

Sec III, Div 1 Class 2, NC-3200 CALVERT CLIFFS ISFSI USAR 12.3-21 Rev. 19 TABLE 12.3-5 NUHOMS-32P

SUMMARY

OF DESIGN CRITERIA FOR ACCIDENT CONDITIONS COMPONENT DESIGN LOAD TYPE REFERENCE DESIGN PARAMETERS APPLICABLE CODE HSM Design Basis Tornado USAR 3.2.1Max velocity 360 mph Max wind pressure 304 psf RG 1.76 ANSI 58.1 1982 Load CombinationUSAR Table 3.2-2Load Combination MethodologyANSI 57.9-1984 Sec 6.17.1.1 Design Basis Tornado Missiles TR 3.2.1.2Max velocity 126 mph Types: Automobile, 3,967 lb 8" diam shell, 276 lb 1" solid sphere NUREG-0800 Sec 3.5.1.4 Flood USAR 2.4.2 Dry Site Seismic USAR 12.3.2.3Horizontal ground acceleration 0.15g (both directions) Vertical ground acceleration 0.10g 7% critical damping NRC RGs 1.60 and 1.61 Accident Condition Temperature USAR 12.8.2.7HSM vents (inlet/outlet) blocked for 36 hrs or less. HSM inside surface temp: 391

°F ANSI 57.9-1984 Fire USAR 12.8.2.101 hour0.00117 days <br />0.0281 hours <br />1.669974e-4 weeks <br />3.84305e-5 months <br /> forest fire 65' from HSM Explosions USAR 8.2.11Probability of liquefied natural gas spill

affecting HSM

< 10-7 NUREG-0800 Section 2.2.3 DSC Accident Drop USAR 12.8.2.5Equivalent static deceleration: 75g vertical end drop 75g horizontal side drop 25g corner drop with slap down (corresponds to an 80" drop height)

Structural damping during drop: 10%

RG 1.61 Flood TR 3.2.2Maximum water height: 50' 10 CFR 72.122(b)

Seismic USAR 12.8.2.3.2Horizontal acceleration: 1.5g Vertical acceleration: 1.0g 3% critical damping NRC RGs 1.60 and

1.61 CALVERT CLIFFS ISFSI USAR 12.3-22 Rev. 19 TABLE 12.3-5 NUHOMS-32P

SUMMARY

OF DESIGN CRITERIA FOR ACCIDENT CONDITIONS COMPONENT DESIGN LOAD TYPE REFERENCE DESIGN PARAMETERS APPLICABLE CODE Accident Internal Pressure (HSM vents blocked) USAR 12.8.2.7DSC internal pressure: 100 psig based on 100% fuel clad rupture and fill gas release, and ambient air temp. = 103

°F. DSC shell temperature: 571

°F Blocked vent time = 36 hrs 10 CFR 72.122(b)

Accident ConditionsTR Table 3.2-6Service Level D ASME B&PV Code Sec III, Div 1, NB, Class 1 Reflood PressureUSAR 12.8.2DSC internal pressure: 40.0 psig 10 CFR 72.122(i)DSC Support Assembly Seismic USAR 12.8.2.3.2DSC reaction loads: Horizontal acceleration: 0.61g Vertical acceleration: 0.39g 7% critical damping NRC RGs 1.60 and

1.61 Load Combination USAR Table 12.8-4 Load combination methodologyANSI 57.9-1984 Sec 6.17.3.2.1 Transfer Cask Design Basis

Tornado TR 3.2.1Max wind velocity: 360 mph Max wind pressure: 397 psf NRC RG 1.76, ANSI 58.1-1982 Design Basis Tornado Missiles TR 3.2.1Automobile, 3967 lb 8" diameter shell, 276 lb NUREG-0800

Sec 3.5.1.4 Flood TR 3.2.2Cask use to be restricted by administrative

controls 10 CFR 72.122 Seismic USAR 3.2.3Horizontal ground acceleration: 0.25g (both directions)

Vertical acceleration: 0.17g 3% critical damping NRC RGs 1.60 and 1.61 CALVERT CLIFFS ISFSI USAR 12.3-23 Rev. 19 TABLE 12.3-5 NUHOMS-32P

SUMMARY

OF DESIGN CRITERIA FOR ACCIDENT CONDITIONS COMPONENT DESIGN LOAD TYPE REFERENCE DESIGN PARAMETERS APPLICABLE CODE Accident Drop USAR 12.8.2.5Equivalent static deceleration: 75g vertical end drop 75g horizontal side drop 25g corner drop with slapdown (corresponds to an 80" drop height) 10 CFR 72.122(b) Structural damping during drop 10%

RG 1.61 Bolts, Accident DropTR Table 3.2-9Service Level D ASME B&PV Code

Sec III, Div 1, Class 2, NC-3200 Structural Design, Accident TR Table 3.2-8Service Level D ASME B&PV Code Sec III, Div 1, Class 2, NC-3200 Internal Pressure--Not applicable because DSC provides pressure boundary 10 CFR 72.122(b)

For more information see Reference 3.14.

CALVERT CLIFFS ISFSI USAR 12.3-24 Rev. 19 TABLE 12.3-6 NUHOMS-32P DSC DESIGN LOAD COMBINATIONS Load Case (1) Normal Operating Conditions Off-Normal Conditions Emergency and Accident Conditions (2) Type I.D. 1 2 3 4 1 2 3 4 1 2 3 4 5 6 1 2 3 4 5 Dead Weight Empty DSC DW 1 X DSC w/water DW 2 X DSC w/fuel DW 3 X X X X X X X X X X X X X X X Thermal Inside HSM: normal T nh X X X X Inside Cask: normal T nc X X X X X Inside HSM: off-normal T ho X X Inside Cask: off-normal T co X X Inside HSM: Accident T ha X Inside Cask: Accident T ca X X Internal Pressure Normal Operating P n X X X X X X X Hydrostatic P h X Off-normal (blowdown) P b X X X X Accident (inner boundary) P a1 X X X Accident (outer boundary) P a2 X Handling Loads Normal DSC Transfer L n X X X Off-normal (jammed DSC) L o X X X X X Accident Loads Cask Drop DL X Seismic E X ASME B&PV Code Service Level A A A A B B B B C C C C C C D D D D D Load Combination No. A 1 A 2 A 3 A 4 B 1 B 2 B 3 B 4 C 1 C 2 C 3 C 4 C 5 C 6 D 1 D 2 D 3 D 4 D 5 (1) The Table has been modified to include hydrostatic and blowdown pressure and to delete the flooding accident load for which no analysis is required.

(2) For emergency and accident load combinations, the DSC shall not be allowed to deform to an extent that would prevent retrieval of spent fuel. For Service Level D, the DSC internal components need only comply with deformation limits that will allow the retrieval of spent fuel. In addition, both end plug assemblies shall maintain their ability to provide shielding for personnel during DSC handling operations.

CALVERT CLIFFS ISFSI USAR 12.4-1 Rev. 15 12.4 INSTALLATION DESIGN The discussion presented in Chapter 4 is not affected by the addition of the NUHOMS-32P DSC to the NUHOMS System. Chapter 4 describes the installation design associated with the Calvert Cliffs ISFSI and related systems. The narrative describes the installation design unique to the NUHOMS systems, such as the storage structures, auxiliary systems, decontamination systems, transfer cask repair and maintenance, and the fuel handling operation systems. The Calvert Cliffs ISFSI is a self-contained, passive storage facility, which requires no auxiliary systems.

CALVERT CLIFFS ISFSI USAR 12.5-1 Rev. 15 12.5 OPERATION SYSTEMS The discussion presented in Chapter 5 is not affected by the addition of the NUHOMS-32P DSC to the NUHOMS System. Chapter 5 describes the operation of the Calvert Cliffs ISFSI. The narrative describes operations unique to the NUHOMS systems, such as draining, drying, and closure of the DSC. Although some operational details are provided, the description is not intended to limit or restrict operation of the facility. Operational procedures may be revised according to the requirements of the plant, provided that the limiting conditions of operation are not exceeded.

CALVERT CLIFFS ISFSI USAR 12.6-1 Rev. 15 12.6 SITE GENERATED WASTE CONFINEMENT AND MANAGEMENT The discussion presented in Chapter 6 is not affected by the addition of the NUHOMS-32P DSC to the NUHOMS System. Chapter 6 describes the on-site waste sources, off-gas treatment and ventilation, liquid waste treatment and retention, solid wastes and radiological impact of normal operations of the Calvert Cliffs ISFSI.

CALVERT CLIFFS ISFSI USAR 12.7-1 Rev. 15 12.7 RADIATION PROTECTION The NUHOMS-32P DSC provides enhanced shielding which helps to compensate for the additional spent fuel elements. Dose rate s for the NUHOMS-32P DSC are presented in Table 12.7-1. The Calvert Cliffs site-specific NUHOMS-32P DSC design meets the requirements of 10 CFR 72.104 and 10 CFR 72.106 for normal, off-normal, and accident conditions.

The principal design features of the NUHOMS-32P DSC are listed in Table 1.3-1 and shown in Figure 12.3-1. Tables 1.2-1 and 12.3-1 lists the capacity, dimensions, and design parameters for the NUHOMS-32P DSC.

The differences between the NUHOMS-32P DSC and NUHOMS-24P DSC that affect shielding and radiation protection are:

• an increase from 24 to 32 spent fuel assemblies,

• an addition of full-length aluminum plates (borated and non-borated) between the guide sleeves,

• an addition of full-length stainless steel ra ils and aluminum rail inserts between the DSC stainless steel cylindrical shell and the outside guide sleeves,

• a redesign of the top shield plug (including vent and siphon ports), and

• increasing the assembly neutron source term from 2.23E+08 n/sec/assy to 3.300E+08 n/sec/assy (Reference 12.47).

The radiation protection and shielding aspects of the NUHOMS-32P DSC, and the effects of these differences, are addressed in detail below.

12.7.1 ENSURING THAT THE OCCUPATIONAL RADIATION EXPOSURES ARE AS LOW AS REASONABLY ACHIEVABLE 12.7.1.1 Policy Considerations The discussion in Section 7.1.1 is unchanged and equally applicable to the NUHOMS-32P DSC.

12.7.1.2 Design Considerations - NUHOMS-32P DSC NUHOMS-32P DSCs can store 32 spent fuel assemblies as opposed to NUHOMS-24P DSCs that store 24. Thus the radiation source is significantly increased in the NUHOMS-32P DSC. The design considerations which ensure that occupational exposures for the NUHOMS ISFSI are as low as reasonably achievable, are discussed in Section 7.1.2. The following paragraphs, which are numbered to correspond with Section 7.1.2, discuss differences in the NUHOMS-24P and NUHOMS-32P designs which affect the shielding design considerations.

1-7. Same as Section 7.1.2.

8. Section 7.1.2 states that the cavity of the NUHOMS-24P DSC will be submerged in the spent fuel pool for about 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and, on removal from the pool, will contain borated water from the spent fuel pool for less than 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />. Because of the larger number of fuel assemblies (32 opposed to 24) to be stored in the NUHOMS-32P DSC, it is expected that the DSC will be submerged in the pool for a longer CALVERT CLIFFS ISFSI USAR 12.7-2 Rev. 19 period of time than the NUHOMS-24P DSC. This additional submersion time does not affect the performance of the austenitic stainless steel as discussed in Section 7.1.2. The NUHOMS-32P DSC also contains aluminum plates (borated and un-borated). There is a substantial body of industry experience with exposure of aluminum to borated and unborated water and its performance is not affected by the pool conditions.

9-15. Same as Section 7.1.2.

12.7.1.3 Operational Considerations The discussion in Section 7.1.3 is unchanged and equally applicable to the NUHOMS-32P DSC.

12.7.2 RADIATION SOURCES - NUHOMS-32P 12.7.2.1 Characterization of Sources The neutron and gamma source-terms used to analyze the NUHOMS-32P DSC are based on the same spent fuel assembly used to analyze the NUHOMS-24P DSC (i.e., 3.4 w/o initial enrichment, 42,000 MWD/MTU burnup, cooled for eight years).

The design basis neutron source per fuel assembly that is used to calculate dose rates from the NUHOMS-32P DSC is increased from 2.23E+08 n/sec/assy to 3.300E+08 n/sec/assy. This increase accounts for the fact that some Calvert Cliffs spent fuel assemblies with a thermal output 660 watts have a neutron source 2.23E+08 n/sec/assy. This NUHOMS-32P DSC design basis source, 3.300E+08 n/sec/assy, bounds all assemblies that have an initial U 235 enrichment 4.5%, burnup 47,000 MWD/MTU, and a thermal output 660 W. The neutron source-term is further increased by a factor 1.107 to account for axial peaking.

The design basis gamma source per fuel assembly for the NUHOMS-32P DSC is the same as the source used for the NUHOMS-24P DSC when the fuel assembly contains no vacancies or stainless steel replacement rods. The addition of stainless steel rods to the fuel assembly increases Co-60 activity due to impurities resulting in a harder spectrum and the need for extended cooling times. Details of the changed gamma source are presented in Reference 12.58. The additional loading criteria for assemblies with irradiated stainless steel replacement rods are presented in Table 9.4-3. The neutron and gamma source spectra calculated using ORIGEN2 computer code are provided in Table 3.1-4.

Figure 7.2-1 has a bounding radiological limit curve for assemblies at or below a thermal power of 660 W/assembly that may be loaded into the NUHOMS-32P and NUHOMS-24P DSC.

CALVERT CLIFFS ISFSI USAR 12.7-3 Rev. 19 12.7.2.2 Airborne Radioactive Material Sources The discussion in Section 7.2.2 is unchanged and equally applicable to the NUHOMS-24P DSC and NUHOMS-32P DSC.

12.7.3 RADIATION PROTECTION DESIGN FEATURES - NUHOMS-32P 12.7.3.1 Installation Design Features The discussion in Section 7.3.1 is applicable to the NUHOMS-32P DSC.

12.7.3.2 Shielding The shielding analyses that support the NUHOMS-32P DSC are identical in form and methodology to the design basis analyses that support the NUHOMS-24P DSC. The methodology and model are described in detail in References 12.29 through 12.33. A comparison to actual NUHOMS-24P DSC data demonstrates that the methodology and model are conservative (Reference 12.33).

The results of the shielding analyses are presented in Table 12.7-1. In most cases, the calculated dose rates outside the NUHOMS-32P DSC are

lower or just slightly higher than the NUHOMS-24P DSC even with eight additional spent fuel assemblies and increased neutron source-term. The shielding provided by the NUHOMS-32P basket assembly helps to compensate for the increased radiation from the additional fuel assemblies.

12.7.3.3 Ventilation The discussion in Section 7.3.3 is applicable to the NUHOMS-32P DSC.

12.7.3.4 Area Radiation and Airborne Radioactivity Monitoring Instrumentation The discussion in Section 7.3.4 is applicable to the NUHOMS-32P DSC.

12.7.4 ESTIMATED ON-SITE COLLECTIVE DOSE ASSESSMENT 12.7.4.1 Operational Exposure The discussion of Section 7.4.1 is applicable to NUHOMS-32P DSC.

12.7.4.2 Storage Term Exposure The discussion of Section 7.4.2 is applicable to NUHOMS-32P DSC.

12.7.5 HEALTH PHYSICS PROGRAM The discussion in Section 7.5 is unchanged and equally applicable to the NUHOMS-24P DSC and NUHOMS-32P DSC.

12.7.6 ESTIMATED OFF-SITE COLLECTIVE DOSE ASSESSMENT 12.7.6.1 Effluent and Environmental Monitoring Program The discussion in Section 7.6.1 is applicable to the NUHOMS-32P DSC.

CALVERT CLIFFS ISFSI USAR 12.7-4 Rev. 19 12.7.6.2 Analysis of Multiple Contribution The discussion in Section 7.6.2 is applicable to the NUHOMS-32P DSC.

12.7.6.3 Estimated Dose Equivalents The discussion in Section 7.6.3 is applicable to the NUHOMS-32P DSC.

12.7.6.4 Liquid Release The discussion in Section 7.6.4 is applicable to the NUHOMS-32P DSC.

CALVERT CLIFFS ISFSI USAR 12.7-5 Rev. 19 TABLE 12.7-1 NUHOMS-32P SHIELDING ANALYSIS RESULTS - NOMINAL DOSE RATES (mrem/hr) LOCATION NEUTRON(c) GAMMA (c) (PRI + SEC)

TOTAL (c) NUHOMS-32P DSC in HSM 1. HSM Wall or Roof 0.6 9.3 9.9 2. HSM Air Outlet 1.2 54.3 55.5

3. Center of Door 5.8 6.3 12.1

4. Doorway (Maximum, 1 ft. into opening) 1075 2943 4018 5. Air Inlet Vent 1 67 68 6. 1m from HSM Door 3 4.8 7.8 NUHOMS-32P DSC in Cask 1. Centerline DSC Shield Plug (Flooded DSC) (a) 1.5 90.9 92.4 2. DSC Cover Plate (Dry DSC) 2.1 Center 48 98 146 2.2A Edge (b) (Wet Gap) 98 61 159 2.2B Edge (b) (Dry Gap) 134 137 271 3. Transfer Cask 3.1 Side 98 48 146 3.2 Top 8.5 1.4 9.9 3.3 Bottom 104 74 178 (a) The DSC/cask annular gap is filled with water. All but the top 6" of the DSC inner cavity is filled with water. (b) Nominal at edge of cover plate. The total dose rate is approximately a factor of 3 lower at the top edge of the transfer cask, and several times higher inside the dry annulus. (c) From References 12.29, 12.30, and 12.31.

CALVERT CLIFFS ISFSI USAR 12.8-1 Rev. 15 12.8 ACCIDENT ANALYSIS - NUHOMS-32P Analyses of all design events for the NUHOMS-24P DSC have been reanalyzed for the NUHOMS-32P DSC. The results are reported in this section in the same format as in Chapter 8. The analytical assumptions, methodology, and computer codes used to generate the results in this section are identical to those used in Chapter 8 unless otherwise noted in the text.

12.8.1 NORMAL AND OFF-NORMAL OPERATIONS This section follows the format of Section 8.1 and includes the evaluation of the normal and off-normal events for the NUHOMS-32P DSC.

12.8.1.1 Normal Operation Structural Analysis The normal operating loads for the NUHOMS-32P important to safety components are shown in Table 8.1-1 of Reference 12.21. A comprehensive structural analysis of the NUHOMS-32P DSC was performed and documented in Reference 12.22.

12.8.1.1.1 Normal Operation Structural Analysis The loads applicable to the normal operation structural analysis such as the dead weight load, internal pressure load, thermal load, handling loads, and live loads are calculated on the same bases as described in detail in Section 8.1.1.1.

12.8.1.1.2 DSC Analysis Stresses were evaluated in the DSC due to: A. Dead Weight Loads B. Design Basis Normal Operating Internal Pressure Loads C. Normal Operating Thermal Loads D. Normal Operation Handling Loads The NUHOMS-32P DSC is analyzed using analytical methods comparable to those described for the NUHOMS-24P DSC in Section 8.1.1.2. The ANSYS analytical model used for the analysis of dead weight, pressure, thermal, and handling loads is similar to that used in the evaluation of the NUHOMS-24P DSC, modified as necessary to reflect the NUHOMS-32P shell assembly. The ANSYS analysis model is described in Reference 12.22. Stresses due to normal operating pressures are based on a bounding internal pressure of 30 psig, applied as a uniform load to the inner boundary of the analytical model. Also considered was the external hydrostatic pressure loading on the DSC shell, when the 3/8" annulus between the DSC shell and the transfer cask is filled with water. Circumferential shell temperature variations are analyzed using the ANSYS three-dimensional solid shell model. The NUHOMS-32P DSC stresses remain within ASME code allowable stresses (Reference 12.24).

CALVERT CLIFFS ISFSI USAR 12.8-2 Rev. 15 12.8.1.1.3 DSC Internal Basket Analysis The DSC basket analysis was performed for: A. Dead Weight Loads B. Thermal Loads The fuel assembly weight of 1,450 lbs (Reference 12.34) and 158" length (Reference 12.28) are used in the analysis. The basket temperature is taken as 650

°F uniform. The peripheral rail temperature is taken as 500

°F uniform.

The three-dimensional finite element analysis ANSYS model used in the evaluation is described in Reference 12.28. The analysis model consists of a 10.28" slice of the NUHOMS-32P DSC basket, rails, and canister using SHELL 43 elements, with appropriate boundary conditions applied at the cut faces of the model. The fuel assembly and aluminum plates are not included in the analysis model. The fuel assembly weight is applied as pressure on the basket plates. The weight of the aluminum plates is accounted for by increasing the density of stainless steel tubes. The aluminum plate stiffness is conservatively neglected in the analysis. The fusion welds connecting the fuels compartment guide sleeves and the bolts connecting the rails are modeled by three-dimensional PIPE20 elements. Gap elements (CONTACT 52) are used to simulate the interface between the basket rails and inner side of canister as well as between outer side of canister and inside of transfer cask.

The results of the analysis show that the stresses in the DSC are within the allowable stress limits (Reference 12.27).

12.8.1.1.4 DSC Support Assembly Analysis The Calvert Cliffs DSC support assembly components are the same as described in Section 8.1.1.4.

The DSC support assembly was reevaluated for the following loads by scaling the results of the NUHOMS-24P DSC evaluation to reflect the weight increase of the NUHOMS-32P DSC. The allowable stresses are taken at a bounding temperature of 600

°F for all conditions, including normal operation (Reference 12.23).

A. Dead Weight Loads B. Normal Operational Handling Loads C. Thermal Loads The calculated stresses were small, and the vertical deflections under the transfer cask loading were less than 0.1".

CALVERT CLIFFS ISFSI USAR 12.8-3 Rev. 15 12.8.1.1.5 HSM Analysis The same array size (2x6) used in Section 8.1.1.5 was used for the NUHOMS-32P DSC. The following loads are considered in the structural analysis for normal operation loads. A. HSM Dead and Live Loads The HSM dead and live loads were evaluated using the ANSYS methodology as discussed in Reference 12.23 for the NUHOMS-32P DSC.

B. Concrete Creep and Shrinkage Loads Loads due to creep and shrinkage of the concrete are determined by the same methodology described in Section 8.1.1.5.B.

C. HSM Thermal Loads The HSM thermal loads, temperature-dependent material properties, analysis approach, and analysis results are documented in Reference 12.23.

Conservatively, an enveloping design temperature of 400°F is used for all conditions, including normal operation (Reference 12.23).

D. Radiation Effect on HSM Concrete The effects of radiation on the HSM concrete were determined to be negligible for the NUHOMS-24P DSC in Section 8.1.1.5.D. The effect of radiation on the HSM concrete remains negligible for the NUHOMS-32P DSC. The neutron fluence from the NUHOMS-32P DSC remains below the threshold for neutron induced degradation of concrete and the gamma flux is less than the NUHOMS-24P DSC value. E. HSM Design Analysis Structural re-evaluation of the HSM concrete structure, DSC support structure, and miscellaneous components for the effects of the increased weight and thermal load of the NUHOMS-32P DSC are documented in Reference 12.23.

The effects of the weight increase are addressed either by scaling the existing stress results of the NUHOMS-24P DSC analyses or by reanalysis of the affected components.

CALVERT CLIFFS ISFSI USAR 12.8-4 Rev. 15 The thermal load evaluation of the HSM concrete structure is performed with the ANSYS computer program using a representative 2-D analytical model of the HSM.

The results of the evaluation confirm that the normal operation moment and shear in the HSM concrete structure are less than the ultimate moment and shear capacity shown in Table 8.1-8 of Chapter 8.

12.8.1.1.6 HSM Door Analysis The discussion in Section 8.1.1.6 is applicable to the NUHOMS-32P DSC.

12.8.1.1.7 Heat Shield Analysis The discussion in Section 8.1.1.7 is applicable to the NUHOMS-32P DSC.

12.8.1.1.8 HSM Seismic Restraint for DSC Details of the analysis of the Calvert Cliffs DSC seismic restraint is provided in Reference 12.23.

12.8.1.1.9 Transfer Cask Analysis The same transfer cask is used to transport the NUHOMS-24P and NUHOMS-32P DSCs and was re-evaluated for the same normal operation loads identified in Section 8.1.1.9, but considering the increased weight of the NUHOMS-32P DSC payload. A bounding design temperature of 400

°F is used for both normal and off-normal operating conditions.

Re-evaluation of the transfer cask for the increased weight of the NUHOMS-32P DSC payload, based on the stress results of the ANSYS analyses of the transfer cask, is presented in Reference 12.25.

The resulting maximum dead weight, thermal, and handling stresses in the transfer cask and its components are within the allowable stress limits.

12.8.1.2 Off-Normal Load Structural Analysis The off-normal loads for the NUHOMS-32P DSC are the same as those identified in Section 8.1.2.

12.8.1.2.1 Jammed DSC During Transfer This off-normal condition results from the DSC becoming jammed in the transfer cask or the HSM during the transfer operation.

CALVERT CLIFFS ISFSI USAR 12.8-5 Rev. 15 A. Postulated Cause of Jammed DSC The discussion in Section 8.1.2.1.A is applicable to the NUHOMS-32P DSC.

B. Detection of Jammed NUHOMS-32P DSC The discussion in Section 8.1.2.1.B is applicable to the NUHOMS-32P DSC.

C. Analysis of Effects and Consequences The analyses of the NUHOMS-32P DSC under the assumed jamming and binding conditions are documented in Reference 12.22.

The stresses on the NUHOMS-32P DSC body have been analyzed for a maximum ram force of 95,000 lbf. The calculated stresses were much less than the ASME code allowable stress criteria. Therefore, plastic deformation of the NUHOMS-32P DSC body will not occur and there is no potential for rupture.

D. Corrective Actions The courses of action open to the system operators to correct a jammed NUHOMS-32P DSC are described in Section 8.1.2.1.D.

12.8.1.2.2 Off-Normal Thermal Loads Analysis Structural analyses of the ISFSI components for off-normal thermal loads are discussed below using the same temperature extremes of -3

°F and 103°F as the NUHOMS-24P design.

A. HSM Off-Normal Thermal Analysis The methodology used for the off-normal thermal loads structural analysis of the HSM concrete structure storing the loaded NUHOMS-32P DSC is the same as for the normal thermal loads structural analysis of the structure described in Section 12.8.1.1.5.C. The DSC support assembly is designed with slotted holes as described in Section 8.1.2.2.A and, therefore, the increase in temperature has no effect on the DSC support structure.

B. DSC Off-Normal Thermal Analysis Off-normal thermal loads structural analysis of the NUHOMS-32P DSC shell assembly and the DSC fuel basket assembly for the DSC inside the HSM are performed using the same methodology as for the CALVERT CLIFFS ISFSI USAR 12.8-6 Rev. 15 normal thermal loads structural analyses of these components.

As discussed in Section 12.8.1.1.9, the off-normal thermal loads for the transfer cask are identical to the normal thermal loads. Therefore, the off-normal thermal loads for the DSC inside the transfer cask are identical to the normal thermal loads for the DSC inside the transfer cask, and are not considered further. C. Transfer Cask Off-Normal Thermal Analysis As previously stated, the off-normal thermal loads for the transfer cask are identical to the normal thermal loads. Therefore, the off-normal thermal loads for the transfer cask are not considered further.

12.8.1.3 Thermal Hydraulic Analyses The following evaluations have been performed for the Calvert Cliffs ISFSI: A. Thermal Analysis of the HSM B. Thermal Analysis of the DSC in the HSM C. Thermal Analysis of the DSC in the Transfer Cask The analytical models of the HSM, the NUHOMS-32P DSC, and the transfer cask are described in References 12.11 (HSM), Reference 12.12 (DSC in the HSM), and 12.10 (DSC in the transfer cask).

The method described in References 12.13 and 12.18 is used for calculating the effective thermal conductivity of the spent fuel assemblies.

The primary portion of the thermal evaluation of the NUHOMS-32P design uses a methodology that differs from the thermal analysis methodology utilized for the NUHOMS-24P. The NUHOMS-32P thermal methodology has three major new features:

• Solution Method - ANSYS finite element

• Model Geometry - 3D

• Treatment of Effective Transverse Thermal Conductivity of Fuel - A detailed finite element model of the spent fuel according to method of the TRW Spent Nuclear Fuel Effective Conductivity Report (Reference 12.14)

The new methodology has been compared in detail with the methodology used for the thermal analysis of the Transnuclear NUHOMS-32PT design (Reference 12.54). The use of the NUHOMS-32PT methodology is appropriate for the Calvert Cliffs ISFSI with the NUHOMS-32P DSC per Reference 12.55.

The radial effective thermal conductivity for helium backfill conditions is determined by creating a two-dimensional finite element ANSYS model of the fuel assembly centered within a basket compartment. The outer CALVERT CLIFFS ISFSI USAR 12.8-7 Rev. 15 surfaces, representing the fuel compartment walls, are held at a constant temperature, and decay heat is applied to the fuel pellets within the model. A maximum fuel assembly temperature is then determined. From the heat load, maximum fuel temperature, and outer surface temperature, the effective fuel conductivity can be determined via an equation given in Reference 12.14.

The axial effective conductivity (Kaxl) is determined directly from the geometry and conductivities of the fuel components.

Mass-weighted averages are used in the determination of the effective density (eff) and specific heat values (C p,eff). The effective properties of the fuel are shown in Reference 12.13.

The thermal analyses are performed with the following ambient air temperatures: A. Normal Conditions The discussion in Section 8.1.3.A is applicable to the NUHOMS-32P DSC.

B. Off-Normal Condition The discussion in Section 8.1.3.B is applicable to the NUHOMS-32P DSC.

C. Accident Condition An extreme summer condition with an ambient temperature of 103°F was considered in Reference 12.2. In addition, the HSM vents are assumed to be completely blocked for a period of 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> or less. A solar heat flux of 127 Btu/hr-ft 2 is conservatively included to maximize the HSM concrete temperatures.

No thermal accident conditions are considered for the transfer cask.

12.8.1.3.1 Thermal Analysis of the HSM The HSM thermal analyses are performed for the ambient air temperatures defined in Section 12.8.1.3.

The decay heat load is transferred from the DSC to the HSM air space by convection and then is removed from the HSM by natural convection air flow. Heat is also radiated from the DSC surface to the heat shield and HSM walls where the natural convection air flow and conduction through the walls removes the heat. The solar heat flux is applied only to the HSM roof. Heat transfer from the outer surface of the HSM roof is by natural convection and radiation to the ambient air. Heat transfer from the HSM floor slab is by conduction to the soil below.

CALVERT CLIFFS ISFSI USAR 12.8-8 Rev. 15 Maximum temperatures on the DSC outer surfaces and the concrete inner and outer surfaces are calculated for the normal, off-normal winter, and off-normal summer ambient conditions, and the postulated accident conditions with blocked HSM vents.

12.8.1.3.2 Thermal Analysis of the DSC in the HSM The DSC and fuel assembly heat transfer analysis with the DSC inside the HSM was performed for the ambient air temperatures defined in Section 12.8.1.3. The analytical model is described in Reference 12.12. The cases of interest are those that maximize fuel cladding temperature (summer ambient conditions) as described in References 12.1 and 12.2. Reference 12.9 evaluates the impact of aluminum/ poison material plates in the DSC basket assembly on the maximum component temperatures. In the analysis, an effective conductivity is determined for the aluminum/poison plates and is substituted for that of the all aluminum interior basket plates in the model from Reference 12.12. The modified model is run for normal, off-normal, and blocked vent conditions. The analysis shows that the modified plates have a negligible impact on maximum component temperatures. The temperatures from these cases are used to derive the DSC internal pressures in Reference 12.17.

The maximum allowable cladding temperature for long-term storage is 335

°C as discussed in Section 8.1.3.2.

The acceptable peak clad temperature limit for accident conditions for ISFSI storage is the same as the generic NUHOMS-24P DSC design (Reference 8.26). This limit is based on the empirical work presented in Reference 8.27. The peak fuel clad temperature limit (short-term) of 570

°C (1,058°F) is specified in the off-normal DSC thermal calculation (Reference 12.1).

12.8.1.3.3 Thermal Analysis of the DSC in the Transfer Cask The thermal analyses for the cases with the DSC inside the transfer cask are performed for the ambient air temperatures defined in Section 12.8.1.3. The analyses are conducted using the model described in Reference 12.12.

Maximum fuel cladding and DSC shell temperatures are calculated for the normal ambient temperature of 70

°F, abnormal summer ambient temperature of 103

°F and the postulated accident conditions with blocked HSM vents.

In the models presented in Reference 12.10, the gap size between the inner shell of the transfer cask and the outer shell of the DSC is assumed uniform in all directions.

CALVERT CLIFFS ISFSI USAR 12.8-9 Rev. 15 Reference 12.19 performs a sensitivity analysis of gap symmetry between the DSC and transfer cask. In addition, Reference 12.20 investigates the sensitivity of maximum temperatures to axial gap size. For the asymmetries and gap sizes investigated, there is little impact on the maximum component temperatures.

Reference 12.3 evaluates the impact of aluminum/poison material plates in the basket on the maximum component temperatures. In the analysis, an effective conductivity is determined for the aluminum/poison plates and is substituted for that of the all aluminum interior basket plates in the models from References 12.15 and 12.16. The analysis shows that the modified plates have a negligible impact on maximum component temperatures.

Use of NS-3 for the transfer cask neutron shield is discussed in Section 8.1.3.3.

12.8.2 ACCIDENTS This section addresses design events of the third and fourth types as defined by ANSI/American Nuclear Society 57.9-1984 (Reference 8.2), and other credible accidents consistent with 10 CFR Part 72 which could impact the safe operation of the Calvert Cliffs ISFSI. The postulated events identified in Section 8.2 of Reference 8.1 and addressed therein for the Calvert Cliffs ISFSI are: A. Loss of Air Outlet Shielding B. Tornado Winds/Tornado Missile C. Earthquake D. Flood E. Transfer Cask Drop F. Lightning G. Blockage of Air Inlets and Outlets H. DSC Leakage I. Accidental Pressurization of DSC In addition, two additional Calvert Cliffs site-specific accidents have been identified and addressed. These are: A. Forest Fire B. Liquified Natural Gas Plant or Pipeline Spill or Explosion The accidents considered, and the associated components affected by each accident, are summarized in Chapter 8, Table 8.2-1.

In the following sections, each accident condition is evaluated for applicability to the Calvert Cliffs ISFSI. For each applicable condition the accident cause, structural, thermal, radiological consequences, and recovery measures required to mitigate the accident are discussed. Where appropriate, resulting accident condition stresses were combined with those of normal operating loads in accordance with the load combination definitions of Section 12.3.2.5. Load combination results for the HSM, NUHOMS-32P DSC, and transfer cask are discussed in Section 12.8.2.12.

CALVERT CLIFFS ISFSI USAR 12.8-10 Rev. 15 Reflood pressure is included as an ASME Service Level D activity but is not identified as an accident.

12.8.2.1 Loss of Air Outlet Shielding The discussion provided in Section 8.2.1 is applicable to NUHOMS-32P DSC. 12.8.2.2 Tornado Winds/Tornado Missile The discussion provided in Section 8.2.2 is applicable to NUHOMS-32P DSC. 12.8.2.3 Earthquake 12.8.2.3.1 Cause of Accident As specified in Section 3.2.3, a Design Basis Earthquake with peak ground acceleration values of 0.15g horizontal and 0.10g vertical is postulated to occur at the Calvert Cliffs ISFSI.

12.8.2.3.2 Accident Analysis Earthquake loads for the evaluation of the HSM concrete structure, DSC support assembly in the HSM, and the transfer cask are determined by scaling the results of the NUHOMS-24P DSC seismic analysis reflecting the weight increase (References 12.23 and 12.25).

The NUHOMS-32P DSC and the DSC basket assembly earthquake loads were determined by a computer analysis (Reference 12.22).

A. DSC Seismic Analysis 1. DSC Seismic Analysis Inside the HSM the combined earthquake load of 1.5g transverse, 1.5g axial, and 1.0g vertical is applied to the finite element model depicting the horizontal orientation of the DSC in storage. In addition to the seismic loads, 1.0g vertical acceleration is added to account for the self-weight effects.

A three-dimensional finite element model of the basket, rails, and the DSC canister was constructed by using the ANSYS computer program. Since the seismic loading is non-symmetric, a 360

° model is used. Details of the analysis model and boundary conditions used are described in Reference 12.28. The finite element model used in the seismic analysis is shown in Reference 12.22.

CALVERT CLIFFS ISFSI USAR 12.8-11 Rev. 15 A nonlinear stress analysis is conducted for computing the elastic stresses in basket and canister shell models using ANSYS computer program. The nonlinearity of analysis results from the gap elements used in the analysis model. Details of the analysis are documented in Reference 12.22 for the DSC canister and Reference 12.28 for the DSC basket assembly.

The resulting maximum stresses in the DSC canister and in the DSC basket assembly remain within the specified ASME code allowable stress criteria.

2. DSC Seismic Stability Analysis An evaluation for the potential of the NUHOMS-32P DSC to lift-off from the DSC support assembly rail during a seismic event is documented in Reference 12.22. The seismic loadings applied to the DSC that would cause instability are based on conservative rigid range seismic acceleration inputs to the HSM of 0.25g horizontal in both transverse and longitudinal directions, and 0.17g vertical. The stability analysis is based on showing that the overturning moment of the DSC on the HSM support structure is smaller than the restoring force moment due to gravity. The non-rigid body modes of the DSC do not contribute to overturning so that the use of the rigid body accelerations is appropriate.

The resultant horizontal acceleration used to calculate the overturning moment is based on the square root of sum of the square of 0.25g in both the transverse and longitudinal directions, equal to 0.35g. The vertical acceleration used to calculate the minimum restoring force is gravity less the vertical acceleration. The restoring moment is determined to be 1.37 times greater than the overturning moment (Reference 12.22). Therefore, the DSC canister is stable during a seismic accident.

B. HSM Seismic Analysis 1. HSM Seismic Stress Analysis Seismic evaluation of the HSM concrete structure is performed using the same methodology as described in Section 8.2.3.2.B.1 CALVERT CLIFFS ISFSI USAR 12.8-12 Rev. 15 for the NUHOMS-24P DSC, with scaled seismic forces applied to the STRUDL finite element analysis model to reflect the weight increase of the NUHOMS-32P DSC.

The resulting forces and moments in the HSM are found to be within the ultimate capacity (Reference 12.23).

2. HSM Seismic Stability Evaluation There is no change in the dimensions of the HSM. As such, the seismic stability of the HSM is not affected by storing the NUHOMS-32P DSC. C. DSC Support Assembly Seismic Analysis The NUHOMS-32P DSC support assembly geometry and, therefore, the DSC support structure computer analysis model is the same as for the NUHOMS-24P DSC. The earthquake loads due to the effects of the weight increase of the NUHOMS-32P DSC are evaluated by scaling the NUHOMS-24P DSC seismic analysis results.

The stress evaluation of the DSC support structure components is performed by hand calculations and the results are within acceptable limits (Reference 12.23).

D. Transfer Cask Seismic Analysis Seismic stresses for the transfer cask with a NUHOMS-32P DSC are determined by conservatively scaling the seismic analysis results of the transfer cask - NUHOMS-24P DSC assembly to account for the increased payload of the NUHOMS-32P (Reference 12.25). This conservative method assumes the weight of the entire transfer cask-DSC system increases by the DSC weight change of 36%, instead of the more accurate 10%. This is done because some components, such as the inner liner, are loaded primarily by the DSC and thus the stresses would be underestimated using the 10% assembly weight increase. The resulting stress intensities are significantly below the ASME Level C allowable stress limits at the transfer cask design temperature of 400°F. Seismic stability of the transfer cask is not a function of the DSC weight and, therefore, remains unaffected by the use of the NUHOMS-32P DSC.

CALVERT CLIFFS ISFSI USAR 12.8-13 Rev. 15 12.8.2.3.3 Accident Dose Consequences Major components of the Calvert Cliffs ISFSI have been designed and evaluated to withstand the forces generated by the Design Basis Earthquake. Hence, there are no dose consequences.

12.8.2.4 Flood As discussed in Section 3.2.2, flood loads are not applicable to the Calvert Cliffs ISFSI.

12.8.2.5 Cask Drop This section addresses the structural integrity of the transfer cask, the NUHOMS-32P DSC, and its internals under a postulated transfer cask accident condition.

12.8.2.5.1 Cause of Accident As discussed in Section 8.2.5.1 of Reference 12.21, an actual drop event is not considered credible. However, consistent with the criteria of Reference 12.21, it is postulated that the transfer cask with the DSC inside will be subjected to an end, side, or oblique drop with a maximum height of 80" onto a thick concrete slab. A drop of greater than 80" is not considered because (a) transfer inside the Auxiliary Building will be performed using a single-failure-proof crane and (b) the transfer trailer and haul road are designed such that the transfer cask cannot be raised greater than 80" from the ground. The transfer cask is transported along an asphalt or concrete paved road which is 16' wide and has 7 to 8' shoulders. The road is approximately 3,300 linear feet with slopes which range from 0% to 3% except for an approximate 50' length which carries a 5.7% slope. The roadbed is level except for a negligible 1% slope required to create a crown in the road for drainage and a transverse slope at any point along the transportation route of less than 10%. The shoulders are either level with the road or slope up from the road. In those locations where the paved road abuts up to existing blacktop, or concrete paving, the shoulder is discontinued. The shoulder may be paved, gravel, or soil and contain typical roadside fixtures, including curbs, fences, guard rails, and light poles which do not constitute potential puncture devices for the cask during a drop. The shoulders do not contain items such as light pole pedestals which protrude above the shoulder surface and could represent a potential cask puncture device during a cask drop. For the entire route that the transfer cask is transported there will exist a minimum 8' wide zone that is at or above the roadbed elevation.

CALVERT CLIFFS ISFSI USAR 12.8-14 Rev. 15 The transfer trailer braking system is not operable independent of the prime mover. However, failure of the prime mover will cause the trailer braking system to fail-safe, that is "lock tight." 12.8.2.5.2 Accident Analysis The drop height (80"), drop orientations, the properties of the target concrete surface, and the methodology used for the evaluation of the transfer with the NUHOMS-32P DSC as payload are the same as described in Section 8.2.5.2.

The design basis cask drop decelerations are specified in Table 12.3-5.

NUHOMS-32P DSC Four accidental drop orientations are postulated for analysis. A. Top end vertical drop B. Bottom end vertical drop C. Horizontal side drop D. Corner Drop A. Top End Vertical Drop A 360° three-dimensional finite element model of the basket, rails, and the NUHOMS-32P DSC was constructed with the ANSYS computer program. Gap elements are used to simulate the interface between the basket rails and inner side of the canister. Details of the analysis model and boundary conditions used are described in Reference 12.22.

Two loadings are applied to the top end drop case: 1. 75g drop load only. 2. 75g drop load with accident pressure (100 psig).

The weight of the basket and fuel assemblies is idealized as an equivalent pressure load against the inner cover plate of the top shield plug. The effect of the combined basket and fuel weight at a maximum 75g acceleration is simulated by equivalent pressure. The effect of the self-weight of the NUHOMS-32P DSC shell assembly at 75g is also applied to the analysis model.

The resulting maximum stress intensities for the "75g drop only" load case and for the "75g drop with accident pressure" show that the case without internal pressure is the bounding analysis.

CALVERT CLIFFS ISFSI USAR 12.8-15 Rev. 15 The maximum stress intensity for the "75g drop only" load case is located in the bottom shield plug side casing. Since these maximum stress intensities are due to the moments at the junction of the respective plates and casings which resist the bending of the flat plates, these are classified as Q stresses in accordance with Note (2) of Table 3217-1 131 of the ASME Code (Reference 12.19) and are ignored for accident condition evaluation.

B. Bottom End Vertical Drop The DSC shell assembly is analyzed for the bottom end vertical drop using the same three-dimensional ANSYS model described above and the same two loadings. The annular area on the bottom end of the model is fixed in the axial direction. This is the area on the bottom lead liner, which contacts the transfer cask. As in the Top End Vertical Drop analysis, the case without internal pressure governs.

The maximum stress intensity for the "75g drop only" load case is located in the top shield plug side casing. Since this maximum stress intensity is due to the moments at the junction of the respective plates and casings which resist the bending of the top inner cover plate, it is classified as Q stress in accordance with Note (2) of Table 3217-1 131 of the ASME Code (Reference 12.19) and is ignored for accident condition evaluation.

C. Horizontal Side Drop A NUHOMS-24P DSC shell assembly consisting of a spacer disk and guide sleeves has been analyzed in Reference 12.49. Because the spacer disks apply a series of concentrated loads, and the NUHOMS-32P basket design will apply a distributed load, the NUHOMS-24P DSC analysis results in Reference 12.49 are conservatively scaled by a factor of 1.37 to reflect the weight increase of the NUHOMS-32P DSC. In order to account for accident pressure, the side drop stress intensities are added directly to the accident pressure stress intensities. The net stress intensities are, therefore, very conservative.

D. Corner Drop No evaluation is required for the comer drop since the stresses are bounded by the vertical drop stresses (Reference 12.49).

CALVERT CLIFFS ISFSI USAR 12.8-16 Rev. 15 Summary of Results The maximum membrane plus bending stress enveloping all the cask drop scenarios evaluated above are below the Level D allowable stresses for the NUHOMS-32P DSC during a cask drop accident (Reference 12.22).

The maximum shear load on the fusion weld connecting the guide sleeves is 6,378 lb (Reference 12.22). The required strength of the fusion weld by testing is 16 kips, (Reference 12.41) which allows a safety factor of 2.

NUHOMS-32P DSC Basket Assembly A. Horizontal Side Drop The basket and canister are analyzed for two modes of side drops. Firstly, the cask is assumed to drop away from the transfer support rails. Under this condition, 0

°, 45°, and 60° orientation of side drops are evaluated to bound the possible maximum stress cases. Secondly, the side drop occurs on transfer cask support rails at 180

° orientation. The load resulting from the fuel assembly weight, for 1g and 75g accelerations, is applied as equivalent pressure on the plates. At 0

° and 180° orientations, the pressure acts only on the horizontal plates while at other orientations, it is divided in components to act on both horizontal and vertical plates of the basket.

A nonlinear static stress analysis of the DSC basket structural assembly is conducted for computing the stresses for the 0

°, 45°, 60°, and 180° drop orientations. A three-dimensional ANSYS model was used for this evaluation. The maximum load of 75g was applied in each analysis. Details of the analysis are described in Reference 12.28.

B. Vertical End Drop During an end drop, the fuel assemblies and fuel compartments are forced against the bottom of the canister/cask. For any vertical or near vertical loading, the fuel assemblies react directly against the bottom or top end of the canister/cask and not through the basket structure as in lateral loading. It is only the dead weight of the basket that causes axial compressive stress during an end drop. Axial compressive stresses are conservatively computed by assuming that all load acts on the fuel compartment guide sleeves during an end drop.

CALVERT CLIFFS ISFSI USAR 12.8-17 Rev. 15 Summary of Results The enveloping maximum membrane plus bending stresses in the basket assembly structural components are below the ASME Code Level D allowable stresses for the NUHOMS-32P DSC basket assembly during a transfer cask drop accident.

Transfer Cask The evaluation of the transfer cask drop accident with a NUHOMS-32P DSC is based on the results of the drop evaluation for NUHOMS-24P DSC using the ANSYS computer model. The maximum stress intensities for individual components of the transfer cask are obtained by scaling to reflect the increased weight of the loaded NUHOMS-32P DSC, and are compared to Level D elastic allowables.

No evaluation is required for the corner drop since the stresses are bounded by the vertical drop stresses (Reference 12.50).

A. Top and Bottom End Vertical Drops In the end drops, nearly all of the DSC load is taken by the underlying end components of the transfer cask. Therefore, the stresses in these components are increased by a scaling factor of 1.51 to reflect the ratio of the weights of the NUHOMS-32P and NUHOMS-24P DSCs. The stresses in the remaining components of the transfer cask are the same with either DSC since the transfer cask weight remains unchanged.

B. Horizontal Side Drop The effect of the added weight of the transfer cask with NUHOMS-32P DSC payload is accounted for by increasing the stresses in the transfer cask structural shell and the inner liner by a factor of 1.1. This increase factor reflects the increased combined weight of the transfer cask and the NUHOMS-32P DSC. This is conservative in that the NUHOMS-32P DSC basket assembly spreads the weight evenly along the length of the transfer cask, while the NUHOMS-24P DSC basket design uses spacer plates which apply concentrated pressure loads at the spacer plate locations. The stresses in the end components of the transfer cask are not changed since they do not see the effect of the increased payload.

CALVERT CLIFFS ISFSI USAR 12.8-18 Rev. 18 Summary of Results The enveloping maximum membrane plus bending stresses are below allowable ASME Code Level D limits for the dropped transfer cask accident.

12.8.2.5.3 Accident Dose Consequences Dose calculations for the transfer cask drop accident with a NUHOMS-32P DSC use the same methodology and model as the calculations for the NUHOMS-24P DSC, and continue to assume that the neutron shielding is lost. The doses for the NUHOMS-32P DSC, with the increased neutron source term, are 1,518 mrem/hr on contact, and 127.6 mrem/hr at 15' (Reference 12.29). The contact dose rate, 1,518 mrem/hr, remains below the limit of 5 rem/hr for this accident (Section 4.7.3.3). The recovery dose to an on-site worker, at an average distance of 15', increases from 776 mrem to

1,021 mrem (127.6 mrem/hr x 8 hr =

1,021 mrem). The recovery dose remains below the limit of 5 rem at the site boundary since the total dose at 15' is much less than 5 rem.

12.8.2.6 Lightning The lightning evaluation presented in Section 8.2.6 is not affected by the addition of the NUHOMS-32P DSC to the NUHOMS System.

12.8.2.7 Blockage of Air Inlets and Outlets This accident is postulated to consist of the complete and total blockage of all HSM air inlets and outlets for a period of 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

12.8.2.7.1 Cause of Accident See Section 8.2.7.1.

12.8.2.7.2 Accident Analysis The stresses caused by the additional weight of debris blocking the air inlets and outlets are bounded by the structural consequences of other accidents described in this section (i.e., tornado and earthquake analyses). The thermal consequences of this accident result from heating of the DSC and HSM due to the loss of natural convection cooling.

The thermal analyses to determine the temperature rise for the Calvert Cliffs HSM and DSC components due to blocked vents are performed using the ANSYS finite element methodology (Reference 12.2). The design basis pressure is considered in the DSC accident pressure evaluation presented in Section 12.8.2.9.

The thermally induced stresses for the HSM for the blocked vent case are calculated using an ANSYS finite element model and the methodology discussed in Reference 12.23.

CALVERT CLIFFS ISFSI USAR 12.8-19 Rev. 15 The thermally induced stresses for the DSC during accident conditions are addressed in Reference 12.22.

12.8.2.7.3 Accident Dose Consequences The discussion in Section 8.2.7.3 is unchanged and is conservative for the NUHOMS-32P DSC because the possible recovery dose is lower. The dose rate at the air inlet vent for the NUHOMS-32P DSC is 68 mrem/hr (Reference 12.30), which is less than the 73 mrem/hr for the NUHOMS-24P DSC. The possible recovery dose incurred by an onsite worker for debris removal is 544 mrem (68 mrem/hr x 8 hr) for the NUHOMS-32P DSC, which is less than the 584 mrem for the NUHOMS-24P DSC (Section 8.2.7.3).

12.8.2.8 Dry Shielded Canister Leakage As described in Section 12.3.3.2, the DSC is designed to ensure no leakage and the analyses for normal and accident conditions have shown that there are no credible events which can breach the DSC pressure boundary or fail the double seal welds at each end of the DSC. However, a total and instantaneous leak of a single NUHOMS-32P DSC is postulated using the same methodology as in Section 8.2.8 except using a 24 month operating cycle (resulting in a release fraction of 5.13%).

The resulting calculated doses for the NUHOMS-32P DSC are: Off-site total body dose: 0.36 mrem, Off-site skin dose: 60.1 mrem.

These doses remain within the 10 CFR 72.106 limit of 5,000 mrem.

12.8.2.9 Accidental Pressurization of Dry Shielded Canister This accident addresses the consequences of accidental pressurization of the NUHOMS-32P DSC.

12.8.2.9.1 Cause of Accident See Section 8.2.9.1.

12.8.2.9.2 Accident Analysis The maximum NUHOMS-32P DSC pressurization is calculated assuming that 100% of the fuel rods in a DSC rupture and release the fission and fuel rod fill gasses to the DSC cavity. The fuel rod fission gas release fraction is assumed to be 30% and the fuel rod fill gas release fraction is assumed to be 100%. The maximum fuel rod fill gas pressure is assumed to be 465 psia and is used to calculate the quantity of fill gas released from fuel rods to the DSC cavity during fuel rod rupture conditions. The internal DSC pressure is calculated at the maximum ambient temperature of 103

°F and a solar heat flux of 127.0 Btu/hr-ft

2.

CALVERT CLIFFS ISFSI USAR 12.8-20 Rev. 15 The limiting accident for DSC pressurization is the HSM blocked vent case as discussed in Section 12.8.2.7. Under these conditions, the gas temperatures in the DSC will rise to 735°F with a DSC internal pressure of 99.4 psig (Reference 12.48). This is based on a 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> vent blockage timeframe, which is conservative compared to the HSM blocked vent accident time of 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> in Section 12.8.2.7.

The maximum DSC pressure boundary stress intensities due to accident pressurization are calculated using 100 psig which bounds the 99.4 psig maximum DSC internal pressure. The calculated component stress intensities at 100 psig were determined to be below the allowable stress limits.

For NUHOMS-32P DSC, the maximum partial pressure of fill gas is 35% of the total gas pressure in the DSC, which is still not a major contributor to the accident DSC internal pressures.

The analysis of accidental pressurization of the DSC includes the effect of fuel burnup on internal fuel rod pressure by using the volume of fission gas generated in the fuel rod at the maximum burnup of 50,000 MWD/MTU. The results of the analysis show that the maximum DSC accident pressures are within the allowable design bases limits.

12.8.2.9.3 Accident Dose Calculations Since the maximum NUHOMS-32P DSC accident pressure is within the design basis limits, there are no dose consequences.

12.8.2.10 Forest Fire This postulated event involves a forest fire occurring in the woods adjacent to the Calvert Cliffs ISFSI.

12.8.2.10.1 Cause of Accident See Section 8.2.10.1.

12.8.2.10.2 Accident Analysis The initial parameters used in Section 8.2.10.2 for the forest fire evaluation remain unchanged for the NUHOMS-32P DSC with the exception of the initial HSM concrete temperature. The NUHOMS-32P forest fire evaluation is based on an initial concrete temperature of 183

°F (Reference 12.56). The damage to the wall, based on the HSM wall temperature gradient resulting from the fire, will be limited to a thickness of 6" into the wall (Reference 12.56). The remainder of the wall thickness will remain within American Concrete Institute 349 temperature limits. Fuel cladding temperature limits will be maintained within the fuel cladding short-term temperature CALVERT CLIFFS ISFSI USAR 12.8-21 Rev. 15 limit. The effect of the surface cracking and spalling will be minimal with respect to the load capacity of the HSM walls.

The NUHOMS-32P DSC internal pr essure limit (100 psig) will not be exceeded. The increase in HSM surface dose is from 9.9 mrem/hr to approximately 45 mrem/hr (Reference 12.57). This increase is not considered a "significant increase in occupational exposure" for the necessary repair activities. Actions to mitigate the fire and repair the HSMs will ensure that offsite dose consequences will be limited and of short duration and will remain within the limits of 10 CFR 72.106.

12.8.2.10.3 Accident Dose Consequences There are no accident dose consequences associated with the postulated forest fire accident.

12.8.2.11 Liquified Natural Gas Plant or Pipeline Spill or Explosion Use of the NUHOMS-32P DSC design does not change the analysis described in Section 8.2.11.

12.8.2.12 Load Combinations The load categories associated with normal, off-normal, and accident conditions have been described and analyzed in previous chapters. Evaluation of the load combination for the NUHOMS-32P important to safety components is addressed in this section.

The methodology used in combining normal, off-normal, and accident loads and their associated overload fa ctors for various NUHOMS-32P components is presented in Reference 12.22. The load combination analysis results showed that the calculated stresses are less than the code allowables for various load combinations shown in Tables 12.8-1, 12.8-2, 12.8-3, 12.8-4, 8.2-14, 8.2-15, and 8.2-16.

When compared to the NUHOMS-24P DSC, the confinement boundary stress allowables (Table 12.8-3) have been altered to an elastic/plastic analysis for all accident conditions except for the 100 psig applied to the inner pressure boundary combinations (D 3 , D 4 , & D 5) Horizontal storage module enveloping load combination results were obtained based on a conservative interpretation of the Calvert Cliffs Nuclear Power Plant (CCNPP) calculation. The forces and moments, including thermal loads, are taken from the ANSYS output presented in Reference 12.23.

The load combination analysis results show that the calculated stresses are less than the code allowable stresses for all the specified normal, off-normal, and accident condition load combinations.

12.8.2.13 Other Event Considerations Use of the NUHOMS-32P DSC design does not change the analysis described in Section 8.2.13.

CALVERT CLIFFS ISFSI USAR 12.8-22 Rev. 15 12.8.3 SITE CHARACTERISTICS AFFECTING SAFETY ANALYSIS All site characteristics affecting safety analyses presented in this document are noted where they apply.

CALVERT CLIFFS ISFSI USAR 12.8-23 Rev. 15 TABLE 12.8-1 NUHOMS-32P DRY SHIELDED CANISTER ENVELOPING LOAD COMBINATION RESULTS FOR NORMAL AND OFF-NORMAL LOADS (ASME Service Levels A and B) DSC COMPONENTS STRESS TYPE CONTROLLING (a) LOAD COMBINATION ALLOWABLE (b)(c) STRESS (ksi)

DSC Shell Primary Membrane B2 18.96 Membrane + Bending B2 28.44 Primary + Secondary B2 56.88 Bottom Cover Plate Primary Membrane A4 18.96 Membrane + Bending B2 28.44 Primary + Secondary B2 56.88 Top Pressure Plate Primary Membrane A3 18.96 Membrane + Bending A3 28.44 Primary + Secondary A3 56.88 Top Structural Plate Primary Membrane A4 18.96 Membrane + Bending A4 28.44 Primary + Secondary A4 56.88 (a) See Table 12.3-6 for load combination nomenclature. (b) See Table 3-4 of Reference 12.22 for allowable stress criteria. Material properties were obtained from Table 3.5 of Reference 12.22 at a design temperature. (c) Allowables are for stainless steel material at 380

°F.

CALVERT CLIFFS ISFSI USAR 12.8-24 Rev. 15 TABLE 12.8-2 NUHOMS-32P DRY SHIELDED CANISTER ENVELOPING LOAD COMBINATION RESULTS FOR ACCIDENT LOADS (ASME Service Level C) DSC COMPONENTS STRESS TYPE CONTROLLING (a) LOAD COMBINATION ALLOWABLE(b)(c) STRESS (ksi)

DSC Shell Primary Membrane C2 21.6 Membrane + Bending C1 32.4 Bottom Cover Plate Primary Membrane C2 21.6 Membrane + Bending C5 32.4 Top Pressure Plate Primary Membrane C2 21.6 Membrane + Bending C2 32.4 Top Structural Plate Primary Membrane C2 21.6 Membrane + Bending C1 32.4 (a) See Table 12.3-6 for load combination nomenclature. (b) See Table 3-4 of Reference 12.22 for allowable stress criteria. Material properties were obtained from Table 3-5 of Reference 12.22 at a design temperature. (c) Allowables are for stainless steel material at 460

°F.

CALVERT CLIFFS ISFSI USAR 12.8-25 Rev. 15 TABLE 12.8-3 NUHOMS-32P DRY SHIELDED CANISTER ENVELOPING LOAD COMBINATION RESULTS FOR ACCIDENT LOADS (ASME Service Level D)(c) DSC COMPONENTS STRESS TYPE CONTROLLING (a) LOAD COMBINATION ELASTIC ALLOWABLE (b) STRESS (ksi)

ELASTIC-PLASTIC ALLOWABLE (d) STRESS (ksi)

DSC Shell Primary Membrane D2 43.2 44.6 Membrane + Bending D2 63.6 57.3 Bottom Cover Plate Primary Membrane D2 43.2 44.6 Membrane + Bending D2 63.6 57.3 Top Pressure Plate Primary Membrane D2 43.2 44.6 Membrane + Bending D2 63.6 57.3 Top Structural Plate Primary Membrane D2 43.2 44.6 Membrane + Bending D2 63.6 57.3 Basket Assembly Primary Membrane D2 44.4 Membrane + Bending D2 57.0 Top End Structural Weld Primary -- 21.6 22.3 Membrane + Bending N/A Bottom End Structural Weld Primary -- 45.1 45.1 For more information see Reference 12.22.

(a) See Table 12.3-6 for load combination nomenclature. (b) See Table 3-4 of Reference 12.22 for allowable stress criteria. Material properties were obtained from Table 3-5 of Reference 12.22 at a design temperature. (c) Allowables are for stainless steel material at 460

°F. (d) Used on 100 psi pressure applied at outer boundary case (D 5).

CALVERT CLIFFS ISFSI USAR 12.8-26 Rev. 15 TABLE 12.8-4 NUHOMS-32P DRY SHIELDED CANISTER SUPPORT ASSEMBLY ENVELOPING LOAD COMBINATION RESULTS AISC Allowable Stress Axial Bending Shear Component Load Combination (ksi) (ksi) (ksi) W8x48 Cross Beam Normal Operation DW s + DW c + HL f 15.5 17.6 10.6 Off-Normal Operation DW s + HL j 26.3 29.9 18.0 Accident DW s + DW c + DBE 24.8 28.1 16.7 W8x40 Support Rail Normal Operation DW s + DW c + HL f 14.6 17.6 10.6 Off-Normal Operation DW s + HL j 24.8 29.9 18.0 Accident DW s + DW c + DBE 23.4 28.1 16.7 KEY: DW s = Dead Weight Support Assembly, HL j = Off-normal Handling Loads-Jammed, DW c = Dead Weight Canister, HL f = Normal Loads Friction, DBE = Seismic Loads NOTES: Allowable stresses taken at 600

°F to conservatively envelope all ambient temperature cases. Allowables for DW s + DW c + DBE increased by a factor of 1.6.

CALVERT CLIFFS ISFSI USAR 12.9-1 Rev. 15 12.9 CONDUCT OF OPERATIONS The Calvert Cliffs ISFSI is operated under the same corporate management organization responsible for operation of the CCNPP. The conduct of operations for the Calvert Cliffs ISFSI are described in Chapter 9.0. The discussion presented in Chapter 9.0 is not affected by the addition of the NUHOMS-32P DSC to the NUHOMS System.

CALVERT CLIFFS ISFSI USAR 12.10-1 Rev. 15 12.10 OPERATING CONTROLS AND LIMITS The discussion presented in Chapter 10 is not affected by the addition of the NUHOMS-32P DSC to the CCNPP NUHOMS System.

CALVERT CLIFFS ISFSI USAR 12.11-1 Rev. 15 12.11 QUALITY ASSURANCE The quality assurance program for the Calvert Cliffs ISFSI covers the construction phase, the operational phase, and the decommissioning phase of structures, systems, and components of the Calvert Cliffs ISFSI important to safety. The Calvert Cliffs ISFSI quality assurance program is discussed in Chapter 11. The discussion presented in Chapter 11 is not affected by the addition of the NUHOMS-32P DSC to the CCNPP NUHOMS System.

CALVERT CLIFFS ISFSI USAR 12.12-1 Rev. 15 12.12 REFERENCES 12.1 CCNPP Calculation No. CA06306, "DSC Thermal Analysis - Off Normal Conditions (Max. Summer Temperature)" 12.2 CCNPP Calculation No. CA06304, "HSM Thermal Analysis - Accident Conditions (Blocked Vents)" 12.3 CCNPP Calculation No. CA06313, "Thermal Analysis of Transfer Cask with Poison Material in Basket" 12.4 CCNPP Calculation No. CA06314, "Thermal Analysis of Vacuum Drying" 12.5 NUREG/6361, dated March 01, 1997, "Criticality Benchmark Guide for Light-Water-Reactor Fuel in Transportation and Storage Packages," March 01, 1997 12.6 CCNPP Calculation CA05895, "Criticality Benchmarks" 12.7 CCNPP Calculation CA06227, "Criticality Analysis of the NUHOMS-32P for Calvert Cliffs ISFSI" 12.8 CCNPP Calculation CA05896 "Criticality Analysis for Fuel Misloads and Accidents" 12.9 CCNPP Calculation CA06312, "Thermal Analysis of Storage Cases Poison Plates in Basket" 12.10 CCNPP Calculation No. CA06296, "Finite Element Models, Thermal Analysis" 12.11 CCNPP Calculation No. CA06301, "HSM Thermal Analysis - Normal Storage Conditions" 12.12 CCNPP Calculation No. CA06305, "DSC Thermal Analysis - Normal Storage Conditions" 12.13 CCNPP Calculation No. CA06295, "Effective Fuel Properties" 12.14 "Spent Nuclear Fuel Effective Conductivity Report," TRW Environmental Safety Systems, Inc., Document Identifier BBA000000-01717-5705-00010 Revision 00 12.15 CCNPP Calculation No. CA06297, "Transfer Thermal Analysis, 103 F" 12.16 CCNPP Calculation No. CA06298, "Transfer Thermal Analysis, -3 F Ambient" 12.17 CCNPP Calculation No. CA06300, "Maximum Operating Pressure, Storage and Transfer" 12.18 CCNPP Calculation No. CA06308, "Effective Fuel Properties for Vacuum Drying" 12.19 CCNPP Calculation No. CA06309, "Sensitivity of the Component Temperatures to the Position of the DSC in the Transfer Cask" 12.20 CCNPP Calculation No. CA06310, "Sensitivity of the Transfer Cask Thermal Analysis to the Axial Gaps Between DSC and Transfer Cask" 12.21 "The Topical Report for the NUTECH Horizontal Modular Storage System for Irradiated Nuclear Fuel NUHOMS-24P," Revision 1A 12.22 CCNPP Calculation No. CA06359, "NUHOMS 32P - DSC Structural Analysis" 12.23 CCNPP Calculation No. CA06364, "NUHOMS 32P - CCNP ISFS HSM Facility Evaluation" 12.24 ASME Boiler and Pressure Vessel Code,Section III, Division 1, Subsection NB and NC and Appendix F, 1998 Edition with 1999 Addenda CALVERT CLIFFS ISFSI USAR 12.12-2 Rev. 15 12.25 CCNPP Calculation No. CA06329, "NUHOMS-32P - Transfer Cask Structural Analysis" 12.26 ASME Boiler and Pressure Vessel Code,Section III, Division 1, Subsection NG and Appendix F, 1998 including 1999 Addenda 12.27 CCNPP Calculation No. CA06326, "NUHOMS 32P Basket Stress Analysis for Storage Loads (Normal and Accident)" 12.28 CCNPP Calculation No. CA06335, "Basket Stress Analysis Due to Accident Transfer Drop" 12.29 CCNPP Calculation No. CA06292, "NUHOMS-32P Radiation Dose Rates Loading and Transfer" 12.30 CCNPP Calculation No. CA06293, "NUHOMS-32P - HSM Dose Rates for Calvert Cliffs ISFSI" 12.31 CCNPP Calculation No. CA06327, "Shielding Evaluation with the New Top Shield Plug for NUHOMS-32P" 12.32 CCNPP Calculation No. CA05924, "Calvert Cliffs ISFSI/NUHOMS-24P Radiation Dose Rates for Cask Loading and Transfer" 12.33 CCNPP Calculation No. CA05925, "Calvert Cliffs ISFSI/NUHOMS-24P HSM Dose Rates" 12.34 CCNPP Calculation No. CA06319, "NUHOMS-32P - Weight Calculation of DSC/TC" 12.35 CCNPP Drawing 84218SH0001, "NUHOMS-32P DSC Shell & Bottom Plug Assembly" 12.36 CCNPP Drawing 84219SH0001, "NUHOMS-32P DSC Shell & Siphon Pipe Assembly Details" 12.37 CCNPP Drawing 84220SH0001, "NUHOMS-32P DSC Siphon Pipe/Adapter & Lifting Block Details" 12.38 CCNPP Drawing 84221SH0001, "NUHOMS-32P DSC Top Shield Plug Details" 12.39 CCNPP Drawing 84222SH0001, "NUHOMS-32P Top Cover Plate & Siphon/Vent Port Covers" 12.40 CCNPP Drawing 84223SH0001, "NUHOMS-32P DSC Basket Assembly" 12.41 CCNPP Drawing 84224SH0001, "NUHOMS 32P DSC Basket Details" 12.42 CCNPP Drawing 84225SH0001, "NUHOMS-32P DSC Basket Rails & Shims" 12.43 CCNPP Drawing 84226SH0001, "NUHOMS-32P DSC Basket Plate & Rail Inserts" 12.44 CCNPP Drawing 84227SH0001, "NUHOMS-32P DSC Parts List" 12.45 CCNPP Drawing 84234SH0001, "NUHOMS-32P DSC Final Assembly, Field Welding &

Testing" 12.46 CCNPP Drawing 84235SH0001, "NUHOMS-32P DSC ASME Code Exceptions" 12.47 CCNPP Engineering Evaluation ES200200585, "Evaluation of the Shielding Source Terms for the ISFSI 32P Phase I Design" 12.48 CCNPP Calculation No. CA06637, "Sensitivit y Analysis of Homogenized Fuel Region" 12.49 CCNPP Calculation No. CA04977, "NUTECH Horizontal Module System (NUHOMS) 24P ISFSI Shielded Canister Structural Analysis for Sixteen New Assemblies" 12.50 CCNPP Calculation No. CA04141, "ISFSI Transfer Cask Structural Analysis" CALVERT CLIFFS ISFSI USAR 12.12-3 Rev. 19 12.51 ASTM E1225, "Thermal Conductivity of Solids by Means of the Guarded-Comparative-Longitudinal Heat Flow Technique" 12.52 ASTM E1461, "Thermal Diffusivity of Solids by the Flash Method" 12.53 NUREG/CR-5661, "Recommendations for Preparing the Criticality Safety Evaluation of Transportation Packages," 1997 12.54 Nuclear Regulatory Commission Safety Evaluation Report, Docket No. 72-1004, Standardized NUHOMS Modular Storage System for Irradiated Nuclear Fuel, Certificate of Compliance No. 1004, Amendment 5 (NUHOMS-32PT System) 12.55 CCNPP 10 CFR 72.48 Safety Evaluation No. SE00163, Revision 1, "Use of NUHOMS-32P Dry Shielded Canister" 12.56 CCNPP Calculation No. CA06653, "Forest Fire Evaluation for the NUHOMS-32P for CCNPP" 12.57 CCNPP Calculation No. CA06629, "Forest Fire Radiological Evaluation for the NUHOMS-32P HSM for CCNPP" 12.58 CCNPP Calculation No. CA06367, "Comparison of the Radiological, Thermal, and Reactivity Characteristics of Assemblies with Missing or Inert Fuel Rods with the 32P ISFSI DSC Design Basis" 12.59 CCNPP Calculation No. CA06354, "Accidental Drop Loading Evaluation of 14x14 Fuel Assembly with Missing Fuel Rods"