ML20108E925

NRC-2020-000169 - Resp 1 - Final, Agency Records Subject to the Request Are Enclosed. Part 5 of 9

ML20108E925
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Issue date:	04/15/2020
From:	NRC/OCIO
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ML20108E919	List: ML20108E920 ML20108E921 ML20108E922 ML20108E923 ML20108E924 ML20108E925 ML20108E926 ML20108E927 ML20108E928 ML20108E929
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FOIA, NRC-2020-000169
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MOLTEC PROPRIETARY INFORMATlmJ Figure 3.4.36 Intentionally Deleted HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-200 Rev. 5

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MObTeC PROPRIETARY INFORMATION J\\N JON 4 2010 15: 13: ll Figure 3.4.37: Finite Element Model for Fuel Rod Integrity Analysis (Load Case 11)

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-201 Rev. 5

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,r.rn ( 2C10 15:lS:56 Figure 3.4.38: Applied Loads for Fuel Rod Integrity Analysis (Load Case 11)

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-202 Rev. 5

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~03. 333 452. 222 601.111 750 FigUJe 3.4.39: Applied Temperatures for Fuel Rod Integrity Analysis (Load Case l l )

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-203 Rev. 5

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HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-204 Rev. 5

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l'.:X *.o:c1 3$ *.cillE*Ql m *.o;.ua HOLTEC PROflRIETARY INFORMATION J\\N JUll l 2Cl0 1!:12:Hi Figure 3.4.41: Strain Distribution in Fuel Rod Due to MPC Reflood (Load Case 11)

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-205 Rev. 5

I IOLTEC PROPRIETAR'/ INFORMATION HI -STORM FW Figure 3.4.42A: Hl-STORM FW Stability Assw-ed Installation in Elevation View (For Reference Only)

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-206 Rev. 5

Hl-9TORIII fW INNER SHELL Hl*STORIII fW 9A8EPV.TE AOL I EC PROPRIE I ARV INFORMATION-ONNECTOR BLOCK Figure 3.4.42B: Stability Assured Installation Detail, Reference Design HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Hi-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-207 Rev. 5

I IOLTEO PROPRIETARV INFORMATION I

OUTER SHELL Figure 3.4.42C: Connector Block Dimensions, Reference Design HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-208 4X VT Rev. 5

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- - - ;:. x-axis Figure 3.4.43: Cask Geometry for Static Analysis of the Restrained HI-STORM FW Configuration HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-209 Rev. 5

HOLTEC f"ROl"RIETARY lt~FORMATION 3.5 FUEL RODS The regulations governing spent fuel storage cask approval and fabrication ( l O CFR 72.236) require that a storage cask system "will reasonably maintain confinement of radioactive material under no1mal, off-normal, and credible accident conditions" (§72.236(1)). Although the cladding of intact fuel rods does provide a barrier against the release of radioactive fission products, the confinement evaluation for the HI-STORM FW system (Chapter 7) takes no credit for fuel cladding integrity in satisfying the regulatory confinement requirement.

As described in Section 7.1, the Confinement Boundary in the HI-STORM FW system consists of the MPC Enclosure Vessel. The Enclosure Vessel is designed and, to the extent practicable, manufactured in accordance with the most stringent ASME B&PV Code (Section III, Subsection NB). As required by NB, all materials are 100% UT inspected and all butt welds are subjected to 100% volumetric inspection. The field closure features redundant barriers (the MPC lid and port cover plates are the primary barriers, the closure ring is the secondary barrier). Section 7.1 further describes that the MPC design, welding, testing and inspection requirements meet the guidance of ISG-18 [7.1.2] such that leakage from the Confinement B0unda1y is non-credible. Section 7.2 addresses confinement for normal and off-normal conditions, and concludes that since the MPC confinement vessel remains intact, and the design bases temperatures and pressure are not exceeded, leakage from the MPC Confinement Boundary is not credible. Confinement for accident conditions is addressed in Section 7.3, which concludes that there is no mechanistic failure mode that could result in a breach of the Confinement B0unda1y, and escape of radioactive materials to the environment.

Since fuel rod cladding is not considered in the design criteria for the confinement of radioactive material under normal, off-nonnal, or accident conditions of storage, no specific analysis or test results are required to demonstrate cladding integrity.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-210 Rev. 5

I IOLTEC PROPRIETARY INFORMATION 3.6 SUPPLEMENTALDATA 3.6.1 Calculation Packages In addition to the calculations presented in Chapter 3, supporting calculation packages have been prepared to document other information pertinent to the analyses. Supporting calculation packages back up the summary results reported in the FSAR. The Calculation Packages are referenced in the body of the FSAR and are maintained as proprietary documents in Holtec's Configuration Control system.

3.6.2 Computer Programs Two computer programs, all with a well established history of usage in the nuclear industry, have been utilized to perform structural and mechanical analyses documented in this FSAR. These codes are ANSYS and LS-DYNA. A third computer program, Visual Nastran, is also described below even though it is not explicitly used in this FSAR. It may, however, be used to perform the seismic stability evaluation of HI-STORM FW casks for a specific ISFSI site where NUREG/CR-6865 is not applicable (see Subsection 3.4.4.1.2).

1.

ANSYS Mechanical ANSYS is the original (and commonly used) name for ANSYS Mechanical general-purpose finite element analysis software. ANSYS Mechanical is the version of ANSYS commonly used for structural applications. It is a self-contained analysis tool incorporating pre-processing (geometry creation, meshing), solver, and post processing modules in a unified graphical user interface.

ANSYS Mechanical is a general purpose finite element modeling package for numerically solving a wide variety of mechanical problems. These problems include: static/dynamic structural analysis (both linear and non-linear), heat transfer and fluid problems, as well as acoustic and electro-magnetic problems.

ANSYS Mechanical has been independently QA validated by Holtec International and used for structural analysis of casks, fuel racks, pressure vessels, and a wide variety of SSCs, for over twenty years.

11.

LS-DYNA LS-DYNA is a general purpose finite element code for analyzing the large deformation static and dynamic response of structures including structures coupled to fluids.

The main solution methodology is based on explicit time integration and is therefore well suited for the examination of the response to shock loading. A contact-impact algorithm allows difficult contact problems to be easily treated. Spatial discretization is achieved by the use of four node tetrahedron and eight node solid elements, two node beam elements, three and four node shell elements, eight node solid shell HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-21 1 Rev. 5

HObTEC PROPRIETARY INEORMATIQN elements, truss elements, membrane elements, discrete elements, and rigid bodies. A variety of element formulations are available for each element type. Adaptive re-meshing is available for shell elements. LS-DYNA currently contains approximately one hundred constitutive models and ten equations-of-state to cover a wide range of material behavior.

In this safety analysis report, LS-DYNA is used to analyze all loading conditions that involve short-time dynamic effects.

LS-DYNA is maintained in a QA-validated status in Holtec's Configuration Control system.

111.

Visual Nastran Visual Nastran [3.6.1] is used for rigid body motion simulation of the cask components, where a simplified analysis is appropriate. VisualNastran is a kinematics simulation code that includes large orientation change capability, simulation of impacts, and representation of contact and friction behavior. Visual Nastran Desktop (VN) perfo1m s time history dynamic analysis of freestanding structures using the acceleration time-histories in the three orthogonal directions as tl1e input. It provides a complete articulation of the dynamic response of the rigid body, including sliding, precession, and tipping (and combinations thereof). Visual Nastran is maintained in a QA-validated status by Holtec International.

All three computer codes have been benchmarked and QA-validated to establish their veracity.

The compliance matrix below provides the necessary information to document their validation status, and the measures employed pursuant to ISG-21 and Holtec's QA program, to ensure error-free solutions.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-212 Rev. 5

HObTEC PROPRIETARY INFORMATION ISG-21 and QA Compliance Matrix for Computer Codes Item ANSYS LS-DYNA

1.

Benchmark and QA-validation are documented in HT-2012627 HJ-961519 Holtec Report No.(s) (Proprietary Reports)

2.

Computer Program Type (Public or Private Domain)

Public Public D omain Domain

3.

Does Holtec maintain a system evaluating error Yes Yes notices if any are issued by the Code provider to evaluate their effect on the safety analyses carried out using the Code, including Part 21 notification?

(Yes/No)

4.

Is the use of the Code restricted to personnel Yes Yes qualified under the Company's personnel qualification program? (Yes/No)

5.

Has benchmarking been perfonned against sample Yes Yes problems with known independently obtained numerical solutions (Yes/No)

6.

Have element types used in the safety analyses herein Yes Yes also employed in the benchmarking effort? (Yes/No)

7.

Are the element types used in this FSAR also used in Yes Yes other Holtec dockets that support other CoCs?

(Yes/No)

8.

Is each update of the Code vetted for backwards Yes Yes consistency with prior updates? (Yes/No)

9.

ls the use of the Code limited to the range of Yes Yes parameters specified in the User Manual provided by the Code Developer? (Yes/No)

10.

Are the element aspect ratios, where applicable, used Yes Yes in the simulation model within the limit recommended by the Code Developer or Holtec's successful experience in other safety analyses?

(Yes/No)

11.

Are element sizes used in the simulation models Yes Yes consistent with past successful analyses in safety significant aoolications? (Yes/No)

12.

Was every computer run in this chapter free of an Yes Yes error warning (i.e., in hidden warnings in the Code that indicate a possible error in the solution?

(Yes/No)

13.

If the answer to the above is No, then is the annotated N IA NIA warning discussed in the discussion of the result in this report?

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-213 Visual Nastran Hl-2022896 Public D omain Yes Yes Yes NIA NIA Yes Yes NIA NIA NIA NIA Rev. 5

lelObTi;C PROPRIETARY INFORMATION 3.7 COMPLIANCE WITH THE STRUCTURAL REQUIREMENTS IN PART72 Supporting information to provide reasonable assurance with respect to the adequacy of the HI-STORM FW system to store spent nuclear fuel in accordance with the stipulations of 1 OCFR 72 is presented throughout this FSAR. The following statements are applicable to an affirmative structural safety evaluation:

The design and structural analysis of the HI-STORM FW system is in compliance with the provisions of Chapter 3 ofNUREG-1536 as applicable.

The HI-STORM FW structures, systems, and components (SSC) that are important to safety (ITS) are identified in the licensing drawings in Section l.5. The licensing drawings present the HI-STORM FW SSCs in adequate detail and the explanatory narratives in Sections 3.1 and 3.4 provide sufficient textual details to allow an independent evaluation of their structural effectiveness.

The requirements of 1 OCFR72.24 with regard to information pertinent to structural evaluation is provided in Chapters 2, 3, and 12.

Technical Specifications pertaining to the structures of the HI-STORM FW system have been provided in Chapter 13 herein pursuant to the requirements of 10CFR72.26.

A series of analyses to demonstrate compliance with the requirements of 10CFR72.122(b) and (c), and 10CFR72.24(c)(3) have been performed which show that SSCs in the HI-STORM FW system designated as ITS possess an adequate margin of safety with respect to all load combinations applicable to normal, off-normal, accident, and natural phenomenon events. In particular, the following information is provided:

1.

Load combinations for the fuel basket, enclosure vessel, and the HI-STORM FW/HI-TRAC VW overpacks for normal, off-normal, accident, and natural phenomenon events are provided in Subsection 3.1.2.2.

11.

Stress limits applicable to the Code materials are found in Section 3.3.

111.

The stress and displacement response of the fuel basket, the enclosure vessel, and the HI-STORM FW/HI-TRAC VW overpacks for all applicable loads have been computed by analysis and repo11ed in Subsections 3.4.3 and 3.4.4.

Descriptions of stress analysis models are presented in Subsection 3.1.3.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-214 Rev. 5

I IOLTEC PROPRIETARY INFORMATION The structural design and fabrication details of the fuel baskets whose safety function in the HI-STORM FW system is to maintain nuclear criticality safety, are provided in the drawings in Section 1.5. The structural factors of safety, summarized in Section 3.4 for all credible load combinations under normal, off-nonnal, accident, and natural phenomenon events demonstrate that the acceptance criteria are satisfied in all cases.

In particular, the maximum lateral deflection in the fuel basket panels under accident events has been determined to be within the limit used in the criticality analysis (see Subsection 3.4.4.1.4). Thus, the requirement of 10CFR72.124(a), with respect to structural margins of safety for SSCs impo1iant to nuclear criticality safety are fully satisfied.

Structural margins of safety during handling, packaging, and transfer operations, under the provisions of 1 OCFR Part 72.236(b ), imply that the lifting and handling devices be engineered to comply with the stipulations of ANSI N 14.6 and NUREG-0612, as applicable. The requirements of the governing standards for handling operations are summarized in Subsection 3.4.3 herein. Factors of safety for all ITS components under lifting and handling operations are summarized in tables in Section 3.4, which show that adequate structural margins exist in all cases.

Consistent with the provisions of 1 OCFR 72.236(i), the Confinement Boundary for the HI-STORM FW system has been engineered to maintain confinement ofradioactive materials under normal, off-normal, and postulated accident conditions. This assertion of confinement integrity is made on the strength of the following information provided in this FSAR.

i.

The MPC Enclosure Vessel which constitutes the Confinement Boundary is designed and fabricated in accordance with Section ill, Subsection NB (Class 1 nuclear components) of the ASME Code to the maximum extent practicable.

11.

The primary lid of the MPC Enclosure Vessel is welded using a strength groove weld and is subjected to multiple liquid penetrant examinations and pressure testing to establish a maximum confidence in weld joint integrity.

111.

The closure system of the MPC Enclosure Vessel consists of two independent isolation barriers.

1v.

The Confinement Boundary is constructed from stainless steel alloys with a proven histo1y of material integrity under the environmental conditions of an ISFSI.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-215 Rev. 5

I IOLTEC PROPRIETARY INFORMATION

v.

The load combinations for normal, off-normal, accident, and natural phenomena events have been compiled and applied on the MPC Enclosure Vessel (Confinement Boundary). The results, sununarized in Section 3.4, show that the factor of safety (with respect to the appropriate limits) is greater than one in all cases. Design Basis natural phenomena events such as tornado-borne missiles (large, intermediate, or small) have also been analyzed to evaluate their potential for reaching and breaching the Confinement Boundary. Analyses presented in Section 3.4 and supplemented by Appendices 3.A and 3.B show that the integrity of the Confinement Boundary is preserved under all design basis projectile impact scenarios.

The information on structural design included in this FSAR complies with the requirements of 10CFR72.120 and 10CFR72.122.

The structural design features in the HI-STORM FW system are in compliance with the specific requirements of 10CFR72.236(e), (f), (g), (h), (i), (j), (k), and (m).

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-216 Rev. 5

3.8

[3.1.1]

[3.1.2]

[3.1.3]

[3.1.4]

[3.1.5]

[3.1.6]

[3.1.7]

[3.1.8]

[3.1.9]

[3.1.10]

[3.3.1]

[3.3.2]

[3.3.3]

HObTEC PROPRIETARY INEORMATIQN REFERENCES NUREG-0612, "Control of Heavy Loads at Nuclear Power Plants," United States Nuclear Regu latory Commission.

ANSI N l4.6-1993, "American National Standard for Special Lifting Devices for Shipping Containers Weighing 10000 Pounds (4500 kg) or More for Nuclear Materials," American National Standards Institute, Inc.

D. Burgreen, "Design Methods for Power Plant Structures", Arcturus Publishers, 1975.

HI-STORM 100 FSAR, Holtec Report No. Hl-2002444, Revision 7 [USNRC Docket 72-1014].

NUREG/CR-1 815, "Recommendations for Protecting Against Failure by Brittle Fracture in Ferritic Steel Shipping Containers Up to Four Inches Thick" Aerospace Structural Metals Handbook, Manson.

SHAKE2000, A Computer Program for the 1-D Analysis of Geotechnical Earthquake Engineering Problems, G.A. Ordonez, Dec. 2000.

LS-DYNA, Version 971, Li vennore Software Technology, 2006.

"Construction ofTrue-Stress-True-Strain Curves for LS-DYNA Simulations," Holtec Proprietary Position Paper DS-307, Revision 2.

• HI-STAR 180 SAR, Holtec Report No. HI-2073681, Revision 3 [USNRC Docket 71-9325].

ASME Boiler & Pressure Vessel Code,Section II, Part D, 2007.

HI-STAR 60 SAR, Holtec Report No. HI-2073 710, Revision 2 [USNRC Docket 71-9336].

Properties of Aluminum Alloys, Tensile, Creep, and Fatigue Data at High and Low Temperatures, ASM International, November 2006.

• Supporting document submitted with the HT-STORM FW License Application (Docket 72-1032).

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-217 Rev. 5

[3.3.4]

[3.3.5]

[3.3.6]

[3.3.7]

[3.3.8]

[3.4.1]

[3.4.2]

[3.4.3]

[3.4.4]

[3.4.5]

[3.4.6]

[3.4.7]

[3.4.8]

[3.4.9]

[3.4.1 O]

HOLTEC PROPRIETARY INFORMATION Holtec Proprietary Report HI-2043162, "Spent Fuel Storage Expansion at Diablo Canyon Power Plant for Pacific Gas and Electric Co.", Revision l (USNRC Docket Nos. 50-275 and 50-323).

American Concrete Institute, ACI-318-05.

American Concrete Institute, "Code Requirements for Nuclear Safety Related Structures" (ACI-349-85) and Commentary (ACI-349R-85).

J.H. Evans, "Structural Analysis of Shipping Casks, Volume 8, Experimental Study of Stress-Strain Properties of Lead Under Specified Impact Conditions", ORNL/TM-1312, Vol. 8, ORNL, Oak Ridge, TN, August, 1970.

ASTM Specification B221M-07, "Standard Specification for Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes (Metric)".

ANSYS 11.0, ANSYS, Inc., 2007.

ASME Boiler & Pressure Vessel Code, Section Ill, Subsection NF, 2007.

ASME Boiler & Pressure Vessel Code,Section III, Appendices, 2007.

ASME Boiler & Pressure Vessel Code,Section III, Subsection NB, 2007.

Witte, M., et al., "Evaluation of Low-Velocity Impacts Tests of Solid Steel Billet onto Concrete Pads, and Application to Generic ISFSJ Storage Cask for Tipover and Side Drop", Lawrence Livermore National Laboratory, UCRL-ID-126295, Livermore, California, March 1997.

Doug Ammerman and Gordon Bjorkman, "Strain-Based Acceptance Criteria for Section III of the ASME Boiler and Pressure Vessel Code", Proceedings of the 151h International Symposium on the Packaging and Transportation of Radioactive Materials, PATRAM 2007, October 21-26, 2007, Miami, Florida, USA.

NUREG/CR-6865, "Parametric Evaluation of Seismic Behavior of Freestanding Spent Fuel Dry Storage Systems," 2005.

NUREG-0800, "Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants," Section No. 3.7.1, 1989.

Bechtel Topical Report BC-TOP-9A, "Design of Structures for Missile Impact",

Revision 2 (September 1974).

l OCFR7 l, Waste Confidence Decision Review, USNRC, September 11, 1990.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Rev. 5 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-218

[3.4.11]

[3.4.12]

[3.4.13]

[3.4.14]

[3.4.15]

[3.4.16)

[3.4.1 7]

[3.4.18]

[3.4.19]

[3.4.20)

[3.4.21)

[3.4.22)

[3.4.23)

[3.4.24)

[3.4.25)

HO! rec PROPRIET,t\\RY INFORMATION Holtec Proprietary Report HI-2094353, "Analysis of the Non-Mechanistic Tipover Event of the Loaded HI-STORM FW Storage Cask", Latest Revision.

Oberg, E. et. al., Machinery's Handbook, Industrial Press Inc., 2ih Edition.

Holtec Proprietary Report HI-2094418, "Structural Calculation Package for HI-STORM FW System", Latest Revision.

EPRI NP-440, Full Scale Tornado Missile Impact Tests, 1977.

Holtec Proprietary Report HI-2094392, "Tornado Missile Analysis for HI-STORM FW System", Latest Revision.

Young, W., Roark's Formulas for Stress & Strain, McGraw Hill Book Company, 6 1h Edition.

Interim Staff Guidance - 15, "Materials Evaluation", Revision 0.

Timoshenko, S., Strength of Materials (Part II), Third Edition, 1958.

"Mechanical Testing and Evaluation", ASM Handbook, Volume 8, 2000.

Adkins, H.E., Koeppel, B.J., Tang, D.T., "Spent Nuclear Fuel St:mctural Response When Subject to an End Drop Impact Accident," Proceedings ASME/JSME Pressure Vessels and Piping Conference, PVP-Vol. 483, American Society of Mechanical Engineers, New York, New York, 2004.

Chun, R., Witte, M., Schwa1tz, M., "Dynamic Impact Effects on Spent Fuel Assemblies", Lawrence Livermore National Laboratory, Report UCID-2 1246, 1987.

Rust, J.H., Nuclear Power Plant Engineering, Haralson Publishing Company, 1979.

NUREG/CR-1864, "A Pilot Probabilistic Risk Assessment of a Dry Cask Storage System at a Nuclear Power Plant", USNRC, Washington D.C., 2007.

EPRI TR-103949, "Temperature Limit Determination for the Inert Dry Storage of Spent Nuclear Fuel", May 1994.

ANSYS 14.0, ANSYS, Inc., 2011.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Rev. 5 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-219

1 IOLTEG PROPRIET.ARY IJIIFORMAIION

[3.4.26]

[3.6.1]

ANSYS 17.1, SAS IP, Inc., 2016.

Visual Nastran 2004, MSC Software, 2004.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 3-220 Rev. 5

(b)(4)

I IOLTEC PROPRll:TARV ll".IFORMA I ION APPENDIX J.A - RESPONSE OF HI-STORM FW AND HI-TRAC VW TO TORNADO WTND LOAD AND LARGE MISSILE [MPACT HOLTBC INTERNATIONAL COPYRIG_HTED MATERJAL REPORT Hl-2 114830 3.A-1 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 Rev. 4

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REPORT fll-2114830 AOL I EC PROPRIE I AR t 1NFORMATIOl'-t HOLTEC INTERNATIONAL COPYRIGHTED MATERJAL 3.A-12 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 Rcv.4

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REPORT Hl-2 114830 HOLTEC PROPRIE'FAR¥-tNFORMATION HOLTEC INTERNATIONAL COPYRIGHTED MA TERJAL 3.A-14 HI-STORM FW SYSTEM FSAR Revision 5. June 20, 2017 Rev. 4

!10L'fEC PROPRIETARY l~IFORMA+IQN-(p)(4)

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,,~~,~~* 1\\01 l<IC:1111<1 "" o,mn,.'ION CHAPTER4* THERMAL EVALUATION 4.0 OVERVIEW The HI-STORM FW system is designed for long-tenn storage of spent nuclear fuel (SNF) in a vertical orientation. The design envisages an array of HI-STORM FW systems laid out in a rectilinear pattern stored on a concrete ISFSI pad in an open environment. In this chapter, compliance of HI-STORM FW system's thermal performance to I OCFR 72 requirements for outdoor storage at an ISFSI using 3-D thennal simulation models is established. The analyses consider passive rejection of decay heat from the stored SNF assemblies to the environment under normal, off-normal, and accident conditions of storage. Finally, the thermal margins of safety for long-term storage of both moderate burnup (up to 45,000 MWD/MTU) and high burnup spent nuclear fuel (greater than 45,000 MWD/MTU) in the HI-STORM FW system are quantified. Safe thermal performance during on-site loading, unloading and transfer operations, collectively referred to as "short-term operations" utilizing the HI-TRAC VW transfer cask is also evaluated.

The HI-STORM FW thermal evaluation follows the guidelines of NUREG-1536 [4.4.1] and JSG-1 1 [4.1.4]. These guidelines provide specific limits on the permissible maximum cladding temperature in the stored commercial spent fuel (CSF) t and other Confinement Boundary components, and on the maximum pennissible pressure in the confinement space under certain operating scenarios. Specifically, the requirements are:

1. The fuel cladding temperature must meet the temperature limit under normal, off-normal and accident conditions appropriate to its burnup level and condition of storage or handling set forth in Table 4.3.1.

2. The maximum internal pressure of the MPC should remain within its design pressures for normal, off-normal, and accident conditions set forth in Table 2.2.1.

3. The temperatures of the cask materials shall remain below their allowable limits set forth in Table 2.2.3 under all scenarios.

As demonstrated in this chapter, the HI-STORM FW system is designed to comply with all of the criteria listed above. Sections 4.1 through 4.3 describe thermal analyses and input data that are common to all conditions of storage, handling and on-site transfer operations. All thermal analyses to evaluate normal conditions of storage in a HI-STORM FW storage module are described in Section 4.4. All thennal analyses to evaluate normal handling and on-site transfer in a HI-TRAC VW transfer cask are described in Section 4.5. All thermal analyses to evaluate off-normal and accident conditions are described in Section 4.6. This SAR chapter is in full t

This chapter has been prepared in the format and section organization set forth in Regulatory Guide 3.6 I.

However, the material content of this chapter also fulfills the requirements ofNUREG-1536. Pagination and numbering of sections, figures, and tables arc consistent with the convention set down in Chapter I, Section 1.0, herein. All terms-of-art used in this chapter are consistent with the terminology of the Glossary. Finally, all evaluations and results presented in this Chapter are supported by calculation packages cited herein (References (4.1.9] and [4.1. 1 O]).

Defined as nuclear fuel that is used to produce energy in a commercial nuclear reactor (See Glossary).

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HJ-2114830 Rev. 5 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-1

I IOLTEC PROPRIETARY INFORMATION compliance with ISG-11 and with NUREG-1536 guidelines, subject to the exceptions and clarifications discussed in Chapter 1, Table 1.0.3.

As explained in Section 1.2, the storage of SNF in the fuel baskets in the HI-STORM FW system is configured for a three-region storage system. Figures 1.2.1 and 1.2.2 provide the information on the location of the regions and Tables 1.2.3 and 1.2.4 provide the permissible specific heat load (heat load per fuel assembly) in each region for the PWR and BWR MPCs, respectively.

The Specific Heat Load (SHL) values are defined for two patterns that in one case maximizes ALARA (Table 1.2.3, Pattern A and Table 1.2.4) and in the other case maximizes heat dissipation (Table 1.2.3, Pattern B). The ALARA maximized fuel loading is guided by the following considerations:

Region 1: Located in the core region of the basket is permitted to store fuel with medium specific heat load.

Region 2: This is the inte1mediate region flanked by the core region (Region I) from the inside and the peripheral region (Region Ill) on the outside. This region has the maximum SHL in the basket.

Region 3: Located in the peripheral region of the basket, this region has the smallest SHL. Because a low SHL means a low radiation dose emitted by the fuel, the low heat emitting fuel around the periphery of the basket serves to block the radiation from the Region II fuel, thus reducing the total quantity of radiation emanating from the MPC in the lateral direction.

Thus, the 3-region arrangement defined above serves to minimize radiation dose from the MPC and peak cladding temperatures mitigated by avoiding placement of hot fuel in the basket core.

To address the needs of cask users having high heat load fuel inventories, fuel loading Pattern B is defined to maximize heat dissipation by locating hotter fuel in the cold peripheral Region 3 and in this manner minimize cladding temperatures. This has the salutary effect of minimizing core temperature gradients in the radial direction and thermal stresses in the fuel and fuel basket.

The salutary consequences of all regionalized loading arrangements become evident from the computed peak cladding temperatures in this chapter, which show margin to the ISG-11 limit discussed earlier.

The safety analyses summarized in this chapter demonstrate acceptable margins to the allowable limits under all design basis loading conditions and operational modes. Minor changes to the design parameters that inevitably occur during the product's life cycle which are treated within the purview of I OCFR 72.48 and are ascertained to have an insignificant effect on the computed safety factors may not prompt a formal reanalysis and revision of the results and associated data in the tables of this chapter unless the cumulative effect of all such unquantified changes on the reduction of any of the computed safety margins cannot be deemed to be insignificant. For purposes of this determination, an insignificant loss of safety margin with reference to an acceptance criterion is defined as the estimated reduction that is no more than one order of magnitude below the available margin reported in the FSAR. To ensure rigorous configuration conh*ol, the information in the Licensing drawings in Section 1.5 should be h*eated as the HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Rev. 5 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-2

1 IOLTEC PROPRIETARY INFORMATlmJ authoritative source for numerical analysis at all times. Reliance on the input data and associated results in this chapter for additional mathematical computations may not be appropriate as they serve the sole purpose of establishing safety compliance in accordance with the acceptance criteria set down in Chapter 2 and in this chapter.

HOL TEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-3 Rev. 5

I IOLTEC PROPRIETARY INFORMATION 4.1 DISCUSSION The aboveground HI-STORM FW system consists of a sealed MPC situated inside a vertically-oriented, ventilated storage overpack. Air inlet and outlet ducts that allow for air cooling of the stored MPC are located at the bottom and top, respectively, of the cylindrical overpack (see Figure 4.1. l ). The SNF assemblies reside inside the MPC, which is sealed with a welded lid to form the Confinement Boundary. The MPC contains a Metamic-HT egg-crate fuel basket structure with square-shaped compartments of appropriate dimensions to allow insertion of the fuel assemblies prior to welding of the MPC lid and closure ring. The MPC is backfilled with helium to the design-basis pressures (Table 4.4.8). This provides a stable, inert environment for long-term storage of the SNF. Heat is rejected from the SNF in the HI-STORM FW system to the environment by passive heat transport mechanisms only.

The helium backfill gas plays an important role in the MPC's thermal performance. The helium fills all the spaces between solid components and provides an improved conduction medium (compared to air) for dissipating decay heat in the MPC. Within the MPC the pressurized helium environment sustains a closed loop thermosiphon action, removing SNF heat by an upward flow of helium through the storage cells. This MPC internal convection heat dissipation mechanism is illustrated in Figure 4.1.2. On the outside of the MPC a ducted overpack construction with a vertical annulus facilitates an upward flow of air by buoyancy forces. The annulus ventilation flow cools the hot MPC surfaces and safely transports heat to the outside environment. The annulus ventilation cooling mechanism is illustrated in Figure 4.1.1. To ensure that the helium gas is retained and is not diluted by lower conductivity air, the MPC Confinement Boundary is designed as an all-seal-welded pressure vessel with redundant closures. It is demonstrated in Section 12. l that the failure of one field-welded pressure boundary seal will not result in a breach of the pressure boundary. The helium gas is therefore assumed to be retained m an undiluted state, and is credited in the thermal analyses.

An impo11ant thermal design criterion imposed on the HI-STORM FW system is to limit the maximum fuel cladding temperature as well as the fuel basket temperature to within design basis limits for long-term storage of design basis SNF assemblies. An equally impo11ant requirement is to minimize temperature gradients in the MPC so as to minimize thermal stresses. In order to meet these design objectives, the MPC baskets are designed to possess certain distinctive characteristics, as summarized below.

The MPC design minimizes resistance to heat transfer within the basket and basket periphery regions. This is ensured by an uninterrupted panel-to-panel connectivity realized in the egg-crate basket structure. The MPC design incorporates top and bottom plenums with interconnected downcomer paths formed by the annulus gap in the aluminum shims. The top plenum is formed by the gap between the bottom of the MPC lid and the top of the honeycomb fuel basket. The bottom plenum is formed by flow holes near the base of all cell walls. The MPC basket is designed to minimize structural discontinuities (i.e., gaps) which introduce added thermal resistances to heat flow. Consequently, temperature gradients are minimized in the design, which results in lower thermal stresses within the basket. Low thermal stresses are also ensured by an MPC design that permits unrestrained axial and radial growth of the basket. The possibility of HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-4 Rev. 5

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sh*esses due to restraint on basket periphery thermal growth is eliminated by providing adequate basket-to-canister shell gaps to allow for basket them1al growth during all operational modes.

(b)(4)

The MPCs regionalized fuel storage scenarios are defined in Figures l.2. 1 and 1.2.2 in Chapter I and design maximum decay heat loads for storage of zircaloy clad fuel are listed in Tables 1.2.3 and l.2.4. The axial beat distribution in each fuel assembly is conservatively asswned to be non-unifo1mly distributed with peaking in the active fuel mid-height region (see axial burnup profiles in Figures 2.1.3 and 2.1.4). Table 4.1.1 summarizes the principal operating parameters of the HI-STORM FW system.

The fuel cladding temperature limits that the HI-STORM FW system is required to meet are discussed in Section 4.3 and given in Table 2.2.3. Additionally, when the MPCs are deployed for storing High Burnup Fuel (HBF) further restrictions during ce1tain fuel loading operations (vacuum drying) are set forth herein to preclude fuel temperatures from exceeding the normal temperature limits. To ensure explicit compliance, a specific term "short-term operations" is defined in Chapter 2 to cover all fuel loading activities. ISG-11 fuel cladding temperature limits are applied for short-term operations.

The HI-STORM FW system (i.e., HI-STORM FW overpack, HI-TRAC VW transfer cask and MPC) is evaluated under normal storage (HI-STORM FW overpack), during off-normal and accident events and during short-term operations in a HI-TRAC VW. Results of HI-STORM FW thermal analysis during normal (long-term) storage are obtained and reported in Section 4.4.

Results of HI-TRAC VW short-term operations (fuel loading, on-site transfer and vacuum drying) are reported in Section 4.5. Results of off-nonnal and accident events are reported in Section 4.6.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-5 Rev. 5

1 IOLTEC PROPRIETARY INFORMATION Table 4.1.1 HI-STORM FW OPERATING CONDITION PARAMETERS Condition Value MPC Decay Heat, max.

Tables 1.2.3 and 1.2.4 MPC Operating Pressure Note 1 Normal Ambient Temperature Table 2.2.2 Helium Backfill Pressure Table 4.4.8 Note 1: The MPC operating pressure used in the thermal analysis is based on the minimum helium backfill pressure specified in Table 4.4.8 and MPC cavity average temperature.

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I IOLTEO PROPRIETARY INFORMATION Figure 4.1.1: Ventilation Flow in the HI-STORM FW System HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-7 Rev. 5

AOL I EC PROPRIE I ARV INFORMA I ION Figure 4.1.2: Illustration ofMPC Internal Helium Circulation HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-8 Rev. 5

lelOb=FEG PROPRIETARY INFORMATIOl<l 4.2

SUMMARY

OF THERMAL PROPERTIES OF MATERIALS The thermo-physical properties listed in the tables in this section are identical to those used in the HI-STORM 100 FSAR [4.1.8], except for Metamic-HT and aluminum shims. Materials present in the MPCs include Alloy x*, Metamic-HT, aluminum alloy 2219, and helium. Materials present in the HI-STORM FW storage overpack include carbon steels and concrete. Materials present in the HI-TRAC VW transfer cask include carbon steel, lead, air, and demineralized water. In Table 4.2.1, a summary of references used to obtain cask material properties for performing all thermal analyses is presented.

Individual thermal conductivities of the alloys that comprise the Alloy X materials and the bounding Alloy X thermal conductivity are reported in Appendix l.A of this report. Tables 4.2.2 and 4.2.3 provide numerical thermal conductivity data of materials at several representative temperatures.

Surface emissivity data for key materials of construction are provided in Table 4.2.4. The emissivity properties of painted external surfaces are generally excellent. Kern [ 4.2.5] reports an emissivity range of 0.8 to 0.98 for a wide variety of paints. In the In-STORM FW thermal analysis, an emissivity of 0.851' is applied to painted surfaces. The solar absorbtivity, a s of paints are generally low. The NASA technical publication [4.2.20] reports as in the range of 0.03 to 0.54. For a robustly bounding analysis a s equal to 0.85 is applied to all exposed overpack surfaces.

In Table 4.2.5, the heat capacity and density of the MPC, overpack and CSF materials are presented. These properties are used in performing transient (i.e., hypothetical fire accident condition) analyses. The temperature-dependent values of the viscosities of helium and air are provided in Table 4.2.6.

The heat transfer coefficient for exposed surfaces is calculated by accounting for both natural convection and thermal radiation heat transfer. The natural convection coefficient depends upon the product of Grashof (Gr) and Prandtl (Pr) numbers. Following the approach developed by Jakob and Hawkins [ 4.2.9], the product GrxPr is expressed as L3 Li TZ, where L is height of the overpack, Li T is overpack surface temperature differential and Z is a parameter based on air properties, which are known functions of temperature, evaluated at the average film temperature.

The temperature dependent values of Z are provided in Table 4.2. 7.

• Alloy X is defined in Appendix 1.A to designate a group of stainless steel alloys permitted for use in tile HI-STORM FW system. In this chapter the terms Alloy X and stainless steel arc used interchangeably.

t This is conservative with respect to prior cask industry practice, which has historically utilized higher emissivities (4.2.16].

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-9 Rev. 5

I IOLTEC PROPRIETARY INFORMATION Table 4.2. l

SUMMARY

OF HI-STORM FW SYSTEM MATERIALS THERMAL PROPERTY REFERENCES Material Emissivity Conductivity Density Heat Capacity Helium NIA Handbook [ 4.2.2]

Ideal Gas Law Handbook [ 4.2.2]

Air NIA Handbook [4.2.2]

Ideal Gas Law Handbook [ 4.2.2]

Zircaloy

[4.2.3], [4.2.17],

NUREG Rust [4.2.4]

Rust [4.2.4]

[4.2.18], [4.2.7]

[4.2.17]

U0 2 Note I NUREG Rust [4.2.4]

Rust [ 4.2.4]

[4.2.17]

Stainless Steel Kern [4.2.5]

ASME [4.2.8]

Marks' [4.2.l]

Marks' [4.2.l]

(machined forgings tote 2 Stainless Steel ORNL ASME [4.2.8]

Marks' [4.2.1]

Marks' [4.2.l]

PlatesNotc 3

[4.2.11], [4.2.12]

Carbon Steel Kern [4.2.5]

ASME [4.2.8]

Marks' [4.2.l]

Marks' [4.2.1]

Concrete Note I Marks' [4.2. l]

Appendix l.D of Handbook [ 4.2.2]

HI-STORM 100 FSAR [4.1.8]

Lead Note 1 Handbook [ 4.2.2]

Handbook [4.2.2]

Handbook [ 4.2.2]

Water Note I ASME [4.2.10]

ASME [4.2.10]

ASME [ 4.2.1 O]

Metamic-HT Test Data Test Data Test Data Test Data Table 1.2.8 Table 1.2.8 Table 1.2.8 Table 1.2.8 Aluminum Alloy Test Data ASM [4.2.19]

ASM [4.2.19]

ASM [4.2.19]

2219 Table 1.2.8 Note I : Emissivity not reported as radiation heat dissipation from these surfaces is conservatively neglected.

Note 2: Used in the MPC lid.

Note 3: Used in the MPC shell and baseplate.

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lelObTi;C PROPRIETARY INFORMATION Table 4.2.2

SUMMARY

OF HI-STORM FW SYSTEM MATERIALS THERMAL CONDUCTIVITY DATA Material At 200°F At450°F At 700°F At 1000°F (Btu/ft-hr-°F)

(Btu/ft-h r-°F)

(Btu/ft-hr-°F)

(Btu/ft-hr-°F)

Helium 0.0976 0.1289 0.1575 0.1890 Air*

0.0173 0.0225 0.0272 0.0336 Alloy X 8.4 9.8 11.0 12.4 Carbon Steel 24.4 23.9 22.4 20.0 Concrete**

1.05 1.05 1.05 1.05 Lead 19.4 17.9 16.9 NIA Water 0.392 0.368 NIA NIA Metamic-HT Table 1.2.8 Aluminum Alloy 2219 **

69.3 69.3 69.3 69.3 Aluminum Alloy 86.7 86.7 86.7 86.7 (Solid Shim Plate)***

At lower temperatures, Air conductivity is between 0.0139 Btu/ft-hr-°F at 32°F and 0.0176 Btu/ft-hr-°F at 212°F.

Conservatively assumed to be constant for the entire range of temperatures.

The optional solid shim aluminum plates discussed in Table 1.2.9 must have the tabulated minimum thermal conductivity.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-11 Rev. 5

HOLTEC F'RO~RIETARY lt~FORMATION Table 4.2.3 *

SUMMARY

OF FUEL ELEMENT COMPONENTS THERMAL CONDUCTIVITY DATA Zircaloy Cladding Fuel (U02)

Temperature (°F)

Conductivity Temperature (°F)

Conductivity (Btu/ft-hr-°F)

(Btu/ft-hr-°F) 392 8.28 100 572 8.76 448 752 9.60 570 932 10.44 793

• See Table 4.2.1 for cited references.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-12 3.48 3.48 3.24 2.28 Rev. 5

I IOLTEC PROPRIETARY INFORMATION Table 4.2.4

SUMMARY

OF MATERIALS SURF ACE EMISSIVITY DA TA*

Material Emissivity Zircaloy 0.80 Painted surfaces 0.85 Stainless steel (machined 0.36 forgings)

Stainless Steel Plates 0.587**

Carbon Steel 0.66 Melamie-Hr*"~

Table 1.2.8

.Extruded Shims Table J.2.9 (Aluminum Alloy 2219i Solid Shims Table l.2.9 (Aluminum Alloyi See Table 4.2.1 for cited references.

• • Lower bound value from the cited references in Table 4.2.1.

• • • l(b)(4) rb)(4)

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Rev. 5

lelObTi;C PROPRIETARY INFORMATION Table 4.2.5 DENSITY AND HEAT CAPACITY PROPERTIES

SUMMARY

Material Density (lbm/ft3)

Heat Capacity (Btu/lbm-°F)

Helium (Ideal Gas Law) 1.24 Air (Ideal Gas Law) 0.24 Zircaloy 409 0.0728 Fuel (U02) 684 0.056 Carbon steel 489 0.1 Stainless steel 501 0.12 Concrete 140**

0.156 Lead 710 0.031 Water 62.4 0.999 Metamic-HT Table 1.2.8 Table 1.2.8 Aluminum Alloy 2219 177.3 0.207

• See Table 4.2. 1 for cited references.

• • Conservatively understated value.

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HOLTEC PROPRIETA~ ( INFORMATION Table 4.2.6 GASES VISCOSITY* VARIATION WITH TEMPERATURE Temperature Helium Viscosity Temperature Air Viscosity (OF)

(Micropoise)

(OF)

(Micropoise) 167.4 220.5 32.0 172.0 200.3 228.2 70.5 182.4 297.4 250.6 260.3 229.4 346.9 261.8 338.4 246.3 463.0 288.7 567.1 293.0 537.8 299.8 701.6 316.7 737.6 338.8 1078.2 377.6 921.2 373.0 1126.4 409.3

• Obtained from Rohsenow and Hartnett [ 4.2.2].

Table 4.2.7 VARIATION OF NATURAL CONVECTION PROPERTIES PARAMETER "Z" FOR AIR WITH TEMPERATURE Temperature (

0 F) z (ff3oFt)*

40

2. lx 106 140 9.0x I 05 240 4.6xl05 340 2.6x 105 440 1.5x I 05

• Obtained from Jakob and Hawkins [4.2.9)

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HObT!?C PROPRIETARY INFORMATION-4.3 SPECIFICATIONS FOR COMPONENTS HI-STORM FW system materials and components designated as "Important to Safety" (i.e.,

required to be maintained within their safe operating temperature ranges to ensure thei_r intended function) are summarized in Tables 2.2.3. The them1al bases supporting the temperature limits are provided in Table 4.3.1. Long-term integrity of SNF is ensured by the Hl-STORM FW system thennal evaluation which demonstrates that fuel c\\addin2. temoeratures are maintained below design basis limits. lCb)(4)

I (b)(4)

Compliance to 1 OCFR72 requires, in part, identification and evaluation of short-tenn, off-nonnal and severe hypothetical accident conditions. The inherent mechanical characteristics of cask materials and components ensure that no significant functional degradation is possible due to exposure to short-term temperature excursions outside the normal long-term temperature limits.

For evaluation of HI-STORM FW system thermal performance, material temperature limits under normal, short-term operations, and off-normal and accident conditions are provided in Table 2.2.3. Fuel temperature limits mandated by ISG-11 [4.1.4] are adopted for evaluation of cladding integrity under normal, short tenn operations, off-normal and accident conditions.

These limits are applicable to all fuel types, burnup levels and cladding materials approved by the NRC for power generation.

• B4C is a refractory material that is unaffected by high temperature ( on the order of I 000°F) and aluminum is solid at temperatures in excess of 1000°F.

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I IOLTEC PROPRIETARY INFORMATION Table 4.3.1 TEMPERATURE LIMITS OF CRITICAL COMPONENTS, °F Fuel Cladding (Note 1)

Condition MBF HBF Normal storage Table 2.2.3 Table 2.2.3 Short-term operations Table 2.2.3 Table 2.2.3 Off-normal and Accident Table 2.2.3 Table 2.2.3 conditions Metamic-HT (Note 2)

Normal storage Table 2.2.3 Short term operations, Off-Normal and Table 2.2.3 Accident conditions Aluminum Shims (Note 3)

Normal storage Table 2.2.3 Short term operations, Off-normal and Table 2.2.3 Accident conditions HI-TRAC VW Jacket Short term operations and off-normal Table 2.2.3 (Note 4) conditions Accident condition NA (Note 5)

Notes:

1. Temperature limits per ISG-11, Rev. 3 [ 4.1.4].

2. The B4C component in Metamic-HT is a refractory material that is unaffected by high temperatme ( on the order of 1000°F) and the aluminum component is solid at temperatures in excess of 1000°F.

3. To preclude melting the temperature limits are set well below the melting temperature of Aluminum Alloys..

4. Temperatme limit is defined by the saturation temperature of water at water jacket design pressure specified in Table 2.2.1.

5. The jacket water is assumed to be lost under accident conditions.

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I IOLTEC PROPRIETARY INFORMATION 4.4 THERMAL EVALUATION FOR NORMAL CONDITIONS OF STORAGE The HI-STORM FW Storage System (i.e., HI-STORM FW overpack and MPC) and HI-TRAC VW transfer cask thermal evaluation is performed in accordance with the guidelines ofNUREG-1536 [ 4.4. l] and ISG-11 [ 4.1.4]. To ensure a high level of confidence in the thermal evaluation, 3-dimensional models of the MPC, HI-STORM FW overpack and HI-TRAC VW transfer cask are constructed to evaluate fuel integrity under normal (long-term storage), off-normal and accident conditions and in the HI-TRAC VW transfer cask under short-term operation and hypothetical accidents. The principal features of the thermal models are described in this section for HI-STORM FW and Section 4.5 for HI-TRAC VW. Thennal analyses results for the long-te1m storage scenarios are obtained and reported in this section. The evaluation addresses the design basis thermal loadings defined in Chapter 1, Tables l.2.3 (MPC-37, Patterns A and B) and 1.2.4 (MPC-89).

Based on these evaluations the limiting thermal loading condition is defined in Subsection 4.4.4 and adopted for evaluation of on-site h*ansfer in the HT-TRAC (Section 4.5) and off-normal and accident events defined in Section 4.6.

4.4.1 Overview of the Thermal Mode)

As illustrated in the drawings in Section l.5, the basket is a mattix of interconnected square compa11ments designed to bold the fuel assemblies in a vertical position under long te1m storage conditions. The basket is a honeycomb structure of Metamic-HT plates that are slotted and arrayed in an orthogonal configuration to form an integral basket structure. !(b)('1)

I l(bX4J Thermal analysis of the HI-STORM FW System is performed for all heat load scenarios defined in Chapter 1 for regionalized storage (Figures 1.2. 1 and 1.2.2). Each fuel assembly is assumed to be generating heat at the maximum permissible rate (Tables 1.2.3 and 1.2.4). Whjle the asswnption of limiting heat generation in each storage cell imputes a certain symmeb*y to the cask thermal problem, it grossly overstates the total heat duty of the system in most cases because it is unlikely that any basket would be loaded with fuel emitting heat at their limiting values in each storage cell. Thus, the thermal model for the HI-STORM FW system is inherently conservative for real life applications. Other noteworthy features of the thennal analyses are:

1.

While the rate of heat conduction through metals is a relatively weak function of temperature, radiation heat exchange increases rapidly as the fomth power of absolute temperature.

11.

Heat generation in the MPC is axially non-uniform due to non-uniform axial burnup profiles in the fuel assemblies.

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I IOLTEC PROPRIETARY INFORMA I ION 111.

Inasmuch as the transfer of heat occurs from inside the basket region to the outside, the temperature field in the MPC is spatially distributed with the lowest values reached at the periphery of the basket.

As noted in Chapter 1 and in Section 3.2, the height of the PWR MPC cavity can vary within a rather large range to accommodate spent nuclear fuel of different lengths. The heat load limits in Table 1.2.3 (PWR MPC) and Table 1.2.4 (BWR MPC) for regionalized storage are, however, fixed regardless of the fuel (and hence MPC cavity) length. Because it is not a'priori obvious whether the shortest or the longest fuel case will govern, thermal analyses are perfo1med for the minimum*, reference and maximum height MPCs. Table 2.1.l allows two different fuel assembly lengths under "minimum" category for PWR fuel. Unless specified in this chapter, the term "minimum" or "short" is used for all short fuel assembly arrays except 15xl 51 sho1t fuel defined in Chapter 2.

As described in Chapter l, two different versions of HI-STORM lid and overpack are available -

standard and Version XL. The lid design details are shown in the licensing drawing package (Section 1.5). Version XL lid can be placed only with the Version XL HI-STORM FW overpack

- this ensures the axial gap between the MPC and HI-STORM lid is cognizant with Table 3.2. 1.

Thermal evaluations of both design options are performed in this chapter and discussed below.

Unless stated, the thermal evaluations in this chapter are based on standard HI-STORM FW lid and overpack design.

The domed lid is a variant of the Version XL lid. Because the flow passage for the ventilation air in the system is unaltered, the domed lid is thermally equivalent to the XL lid. Thus, the results presented in this chapter for the Version XL lid should be considered applicable for the domed lid design.

4.4.1.1 Description of the 3-D Thermal Model

1.

Overview The HI-STORM FW System is equipped with two MPC designs, MPC-37 and MPC-89 engineered to store 37 and 89 PWR and BWR fuel assemblies respectively. The interior of the MPC is a 3-D array of square shaped cells inside an irregularly shaped basket outline confined inside the cylindrical space of the MPC cavity. To ensure an adequate representation of these features, a 3-D geometric model of the MPC is constructed using the FLUENT CFD code pre-processor [ 4.1.2]. Because the fuel basket is made of a single isotropic material (Metamic-HT),

the 3-D thermal model requires no idealizations of the fuel basket structure. However, since it is impractical to model every fuel rod in every stored fuel assembly explicitly, the cross-section bounded by the inside of the storage cell (inside of the fuel channel in the case of BWR MPCs),

which surrounds the assemblage of fuel rods and the interstitial helium gas (also called the

• Both allowable PWR fuel assembly lengths under "minimum" category as shown in Table 2.1.1 are evaluated in this chapter.

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I IOLTEC PROPRIETARY INFORMATION "rodded region"), is replaced with an "equivalent" square homogeneous section characterized by an effective thermal conductivity. Homogenization of the cell cross-section is discussed under item (ii) below. For thermal-hydraulic simulation, each fuel assembly in its storage cell is represented by an equivalent porous medium. For BWR fuel, the presence of the fuel channel divides the storage cell space into two distinct axial flow regions, namely, the in-channel (rodded) region and the square prismatic annulus region (in the case of PWR fuel this modeling complication does not exist). The methodology to represent the spent fuel storage space as a homogeneous region with equivalent conductivities is identical to that used in the HI-STORM 100 Docket No. 72-1014 (4.1.8].

11.

Details of the 3-D Model The HI-STORM FW fuel basket is modeled in the same manner as the model described in the HT-STAR 180 SAR (NRC Docket No. 71-9325) (4.1.l l]. Modeling details are provided in the following:

Fuel Basket 3D Model The MPC-37 and MPC-89 fuel baskets are essentially an array of square cells within an irregularly shaped basket outline. The fuel basket is confined inside a cylindrical cavity of the MPC shell. Between the fuel basket-to-shell spaces, thick Aluminum basket shims are installed to facilitate heat dissipation. To ensure an adequate representation of the fuel basket a geometrically accurate 3D model of the array of square cells and Metamic-HT plates is constructed using the FLUENT pre-processor. Other than the representation of fuel assemblies inside the storage cell spaces as porous region with effective thermal-hydraulic properties as described in the next paragraph, the 3D model includes an explicit articulation of other canister parts. The basket shims are explicitly modeled in the peripheral spaces. The fuel basket is surrounded by the MPC shell and outfitted with a solid welded lid above and a baseplate below.

All of these physical details are explicitly articulated in a quarter-symmetric 3D thermal model of the HI-STORM FW.

Fuel Region Effective Planar Conductivity In the HI-STORM FW thermal modeling, the cross section bounded by the inside of a PWR storage cell and the channeled area of a BWR storage cell is replaced with an "equivalent" square section characterized by an effective thermal conductivity in the planar and axial directions. Figure 4.4.1 pictorially illustrates this concept. The two conductivities are unequal because while in the planar direction heat dissipation is interrupted by inter-rod gaps; in the axial direction heat is dissipated through a continuous medium (fuel cladding). The equivalent planar conductivity of the storage cell space is obtained using a 2D conduction-radiation model of the bounding PWR and BWR fuel storage scenarios defined in the table below. The fuel geometry, consisting of an array of fuel rods with helium gaps between them residing in a storage cell, is constructed using the ANSYS code [ 4.1. 1] and lowerbound conductivities under the assumed condition of stagnant helium (no-helium-flow-condition) are obtained. In the axial direction, an area-weighted average of the cladding and helium conductivities is computed. Axial heat conduction in the fuel pellets is conservatively ignored.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-20 Rev. 5

HOLTEC PROPRIETARY INFORMATlQN The effective fuel conductivity is computed under four bounding fuel storage configurations for PWR fueled MPC-37 and one bounding scenario for BWR fueled MPC-89. The fuel storage configurations are defined below:

Storage Scenario MPC Fuel PWR: 15xl 5I Short Fuel Minimum Height MPC-37 for l5xl5I 15xl51 in Table2.l.2 fuel assembly array PWR: Sh01t Fuel Minimum Height MPC-37 for all fuel I4x14 Ft. Calhoun assembly arrays except 15x l 5I PWR: Standard Fuel Reference Height MPC-37 W-17xl 7 PWR: XL Fuel Maximum Height MPC-37 APIOOO BWR MPC-89 GE-lOxlO The fuel region effective conductivity is defined as the calculated equivalent conductivity of the fuel storage cell due to the combined effect of conduction and radiation heat transfer in the manner of the approach used in the HI-STORM 100 system (Docket No. 72-1014). Because radiation is propottional to the fourth power of absolute temperature, the effective conductivity is a strong function of temperature. The ANSYS finite element model is used to characterize fuel resistance at several representative storage cell temperatures and the effective thermal conductivity as a function of temperature obtained for all storage configurations defined above and tabulated in Table 4.4.1.

Heat Rejection from External Surfaces The exposed surfaces of the HI-STORM FW dissipate heat by radiation and external natural convection heat transfer. Radiation is modeled using classical equations for radiation heat transfer (Rohsenow & Hartnett [4.2.2]). Jakob and Hawkins [4.2.9] recommend the following correlations for natural convection heat transfer to air from heated vertical and horizontal surfaces:

Turbulent range:

h = 0.19 (~ T t\\Vertical, GrPr > 10 9

)

h = 0.18 (~ T) 113 (Horizontal Cylinder, GrPr > 109)

(in conventional U.S. units)

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Laminar range:

~LTEG PRe~RIETARV INFORMATION h = 0.29 (LlLT )114 (Vertical, GrPr < 109) h = 0.27 (Ll T )114 (Horizontal Cylinder, GrPr < 1 o9)

D (in conventional U.S. Units) where.11T is the temperature differential between the cask's exterior surface and ambient air and GrPr is the product of Grashof and Prandtl numbers. During storage conditions, the cask cylinder and top surfaces are cooled by natural convection. The corresponding length scales L for these surfaces are the cask diameter and length, respectively. As described in Section 4.2, GrxPr can be expressed as L3LlTZ, where Z (from Table 4.2.7) is at least 2.6xl05 at a conservatively high surface temperature of 340°F. Thus the turbulent condition is always satisfied assuming a lowerbound L (8 ft) and a small LlT (- lO°F).

Determination of Solar Heat Input The intensity of solar radiation incident on exposed surfaces depends on a number of time varying parameters. The solar heat flux strongly depends upon the time of the day as well as on latitude and day of the year. Also, the presence of clouds and other atmospheric conditions ( dust, haze, etc.) can significantly attenuate solar intensity levels. In the interest of conservatism, the effects of dust, haze, angle of incidence, latitude, etc. that act to reduce insolation, are neglected.

The insolation energy absorbed by the HI-STORM FW is the product of incident insolation and surface absorbtivity. To model insolation heating a reasonably bounding absorbtivity equal to 0.85 is incorporated in the the1mal models. The HI-STORM FW thermal analysis is based on 12-hour daytime insolation specified in Article 71.7 l(c) (1) of the Transport Regulations [ 4.6.1).

During long-term storage, the HI-STORM FW Overpack is cyclically subjected to solar heating during the 12-hour daytime period followed by cooling during the 12-hour nighttime. Due to the large mass of metal and the size of the cask, the dynamic time lag exceeds the 12-hour heating period. Accordingly, the HI-STORM FW model includes insolation on exposed surfaces averaged over a 24-hour time period.

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I IOLTEC PROPRIETARY INFORMA I ION HI-STORM FW Annulus The HI-STORM FW is engineered with internal flow passages to facilitate heat dissipation by ventilation action. During fuel storage ambient air is drawn from intake ducts by buoyancy forces generated by the heated column of air in the HI-STORM FW annulus. The upward moving air extracts heat from the MPC external surfaces by convection heat transfer. As great bulk of the heat is removed by the annulus air, the adequacy of the grid deployed. to model annulus heat transfer must be confirmed prior to performing design basis calculations. To this end a grid sensitivity study is conducted in Subsection 4.4.1.6 to define the converged grid discretization of the annulus region. The converged grid is deployed to evaluate the thermal state of the HI-STORM FW system under normal, off-normal and accident conditions of storage.

iii. Principal Attributes of the 3D Model The 3-D model implemented to analyze the HI-STORM FW system is entirely based on the HI-STORM 100 thermal model except that the radiation effect is simulated by the more precise "DO" model (in lieu of the DTRM model used in HI-STORM 100) in FLUENT in the manner of HI-STAR 180 in docket 71-9325. This model has the following key attributes:

a) The fuel storage spaces are modeled as porous media having effective thermal-hydraulic properties.

b) In the case of BWR MPC-89, the fuel bundle and the small surrounding spaces inside the fuel "channel" are replaced by an equivalent porous media having the flow impedance properties computed using a conservatively articulated. 3-D CFD model [ 4.4.2]. The space between the BWR fuel channel and the storage cell is represented as an open flow annulus. The fuel channel is also explicitly modeled.

The channeled space within is also referred to as the "rodded region" that is modeled as a porous medium. The fuel assembly is assumed to be positioned coaxially with respect to its storage cell. The MPC-89 storage cell occupied with channeled BWR fuel is shown in Figure 4.4.4.

In the case of the PWR CSF, the porous medium extends to the entire cross-section of the storage cell. As described in [ 4.4.2], the CFD models for both the BWR and PWR storage geometries are constructed for the Design Basis fuel defined in Table 2.1.4. The model contains comprehensive details of the fuel which includes grid straps, BWR water rods and PWR guide and instrument tubes (assumed to be plugged for conservatism).

c) The effective conductivities of the MPC storage spaces are computed for bounding fuel storage configurations defined in Paragraph 4.4.1.1 (ii). The in-plane thermal conductivities are obtained using ANSYS [ 4. 1.1] finite element models of an array of fuel rods enclosed by a square box. Radiation heat transfer from solid surfaces ( cladding and box walls) is enabled in these models. Using HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-23 Rev. 5

I IOLTEC PROPRIETARY INFORMATION these models the effective conduction-radiation conductivities are obtained and reported in Table 4.4.1. For heat transfer in the axial direction an area weighted mean of cladding and helium conductivities are computed (see Table 4.4.1). Axial conduction heat transfer in the fuel pellets and radiation heat dissipation in the axial direction are conservatively ignored. Thus, the thermal conductivity of the rodded region, like the porous media simulation for helium flow, is represented by a 3-D continuum having effective planar and axial conductivities. In the interest of conservatism, them1al analysis of normal storage condition in HI-STORM FW and normal onsite transfer condition in HI-TRAC VW (Section 4.5) are performed with a I 0% reduced effective thermal conductivity of fuel region.

d) The internals of the MPC, including the basket cross-section, aluminum shims, bottom flow holes, top plenum, and circumferentially irregular downcomer formed by the annulus gap in the aluminum shims are modeled explicitly. For simplicity, the flow holes are modeled as rectangular openings with an understated flow area.

e) The inlet and outlet vents in the HI-STORM FW overpack are modeled explicitly to incorporate any effects of non-axisymmetry of inlet air passages on the system's thermal performance.

f) The air flow in the HI-STORM FW/MPC annulus is simulated by the k-ro turbulence model with the transitional option enabled. The adequacy of this turbulence model is confinned in the Holtec benchmarking report [4.1.6). The annulus grid size is selected to ensure a converged solution.(See Section 4.4.1.6).

g) A limited number of fuel assemblies (upto 12 in MPC-37 and upto 16 in MPC-89) classified as damaged fuel are pennitted to be stored in the MPC inside Damaged Fuel Containers (DFCs). A DFC can be stored in the outer peripheral locations of both MPC-37 and MPC-89 as shown in Figures 2.1.1 and 2.1.2, respectively.

DFC emplaced fuel assemblies have a higher resistance to helium flow because of the debris screens. However, DFC fuel storage does not affect temperature of hot fuel stored in the core of the basket because DFC storage is limited by Technical Specifications for placement in the peripheral storage locations away from hot fuel. For this reason the them1al modeling of the fuel basket under the assumption of all storage spaces populated with intact fuel is justified.

h) As shown in HI-STORM FW drawings in Section 1.5 the HI-STORM FW overpack is equipped with an optional heat shield to protect the inner shell and concrete from radiation heating by the emplaced MPC. The inner and outer shells and concrete are explicitly modeled. AIL the licensing basis therma l analyses explicitly include the heat shields. A sensitivity study is performed as described in paragraph 4.4.1.9 to evaluate the absence of heat shield on the overpack inner shell and overpack lid.

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HOL TEC PROPRIE I ARV INFORMATION i) To maximize lateral resistance to heat dissipation in the fuel basket, 0.8 mm full length inter-panel gaps are conservatively assumed to exist at all intersections.

This approach is identical to that used in the thermal analysis of the HI-ST AR 180 Package in Docket 71-9325. The shims installed in the MPC peripheral spaces (See MPC-37 and MPC-89 drawings in Section 1.5) are explicitly modeled. For conservatism bounding as-built gaps (3 mm basket-to-shims and 3 mm shims-to-shell) are assumed to exist and incorporated in the thermal models.

j) The thennal models incorporate all modes of heat transfer ( conduction, convection and radiation) in a conservative manner.

k) The Discrete Ordinates (DO) model, previously utilized in the HI-STAR 180 docket (Docket 71-9325), is deployed to compute radiation heat transfer.

l) Laminar flow conditions are applied in the MPC internal spaces to obtain a Jowerbound rate of heat dissipation.

The 3-D model described above is illustrated in the cross-section for the MPC-89 and MPC-37 in Figures 4.4.2 and 4.4.3, respectively. A closeup of the fuel cell spaces which explicitly include the channel-to-cell gap in the 3-D model applicable to BWR fueled basket (MPC-89) is shown in Figure 4.4.4. The principal 3-D modeling conservatisms are listed below:

1) The storage cell spaces are loaded with high flow resistance design basis fuel assemblies (See Table 2. 1.4).

2) Each storage cell is generating heat at its limiting value under the regionalized storage scenarios defined in Chapter 2, Section 2.1.

3) Axial dissipation of heat by conduction in the fuel pellets is neglected.

4) Dissipation of heat from the fuel rods by radiation in the axial direction is neglected.

5) The fuel assembly channel length for BWR fuel is overstated.

6) The most severe environmental factors for long-term normal storage - ambient temperature of 80°F and 10CFR71 insolation levels - were coincidentally imposed on the system.

7) Reasonably bounding solar absorbtivity of HI-STORM FW overpack external surfaces is applied to the thermal models.

8) To understate MPC internal convection heat transfer, the helium pressure is understated.

9) No credit is taken for contact between fuel assemblies and the MPC basket wall or between the MPC basket and the basket supports.

10) Heat dissipation by fuel basket peripheral supports is neglected.

11) Lowerbound fuel basket emissivity function cllefined in the Metamic-HT Sourcebook

[ 4.2.6] is adopted in the thermal analysis.

12) Lowerbound stainless steel emissivity obtained from cited references (See Table 4.2.1) are applied to MPC shell.

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I IOLTEC PROPRIETARY INFORMATION

13) The k-ro model used for simulating the HI-STORM FW annulus flow yields uniformly conservative results [ 4.1.6].

14) Fuel assembly length is conservatively modeled equal to the height of the fuel basket.

The effect of crud resistance on fuel cladding surfaces has been evaluated and found to be negligible [ 4.1.8]. The evaluation assumes a thick crud layer ( 130 µm) with a bounding low conductivity ( conductivity of helium). The crud resistance increases the clad temperatme by a very small amount (- 0.1 °F) [ 4.1.8]. Accordingly this effect is neglected in the thermal evaluations.

4.4.1.2 Fuel Assembly 3-Zone Flow Resistance Model*

The HI-STORM FW System is evaluated for storage of representative PWR and BWR fuel assemblies determ ined by a separate analysis, to provide maximum resistance to the axial flow of helium. These are (i) PWR fuel: W17xl7 and (ii) BWR fuel: GE lOxlO. During fuel storage helium enters the MPC fuel cells from the bottom plenum and flows upwards through the open spaces in the fuel storage cells and exits in the top plenum. Because of the low flow velocities the helium flow in the fuel storage cells and MPC spaces is in the laminar regime (Re < I 00).

The bottom and top plenums are essentially open spaces engineered in the fuel basket ends to facilitate helium circulation. In the case of BWR fuel storage, a channel enveloping the fuel bundle divides the flow in two parallel paths. One flow path is through the in-channel or rodded region of the storage cell and the other flow path is in the square annulus area outside the channel. In the global thermal modeling of the HI-STORM FW System the following approach is adopted:

(i)

In BWR fueled MPCs, an explicit channel-to-cell gap is modeled.

(ii)

The fuel assembly enclosed in a square envelope (fuel channel for BWR fuel or fuel storage cell for PWR fuel) is replaced! by porous media with equivalent flow resistance.

The above modeling approach is illustrated in Figure 4.4.4.

In the FLUENT program, porous media flow resistance is modeled as follows:

~P/L = DµV (Eq. 1) where ~P/L is the hydraulic pressure loss per unit length, D is the flow resistance coefficient, µ is the fluid viscosity and V is the superficial fluid velocity. In the HI-STORM FW thermal models the fuel storage cell length between the bottom and top plenums t is replaced by porous

• This Sub-section duplicates the methodology used in the HI-STORM FSAR, Rev. 7, supporting CoC Amendment

1. 5 in Docket 72-10 14 [ 4.1.8).

t These are the flow hole openings at the lower end of the fuel basket and a top axial gap to facilitate helium circulation. The flow holes are explicitly included in the 3D thermal models with an understated flow area.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-26 Rev. 5

I IOLTEC PROPRIETARY INFORMATION media. As discussed below the porous media length is partitioned in three zones with discrete flow resistances.

To characterize the flow resjstance of fuel assemblies inside square envelopes (fuel channel for BWR fuel or fuel storage cell for PWR fuel) 3D models of W-17x17 and GE-lOxlO fuel assemblies are constructed using the FLUENT CFD program. These models are embedded with several pessimistic assumptions to overstate flow resistance. These are:

(a) Water rods (BWR fuel) and guide tubes (PWR fuel) are assumed to be blocked (b) Fuel rods assumed to be full length (c) Channel length (BWR fuel) overstated

( d) Bounding grid thickness used (e) Bottom fittings resistance overstated (f) Bottom nozzle lateral flow holes (BWR fuel) assumed to be blocked The flow resistance coefficients computed from the 3D flow models [ 4.4.2] are adopted herein for an MPC-89. In the interest of conservatism, a flow resistance of Ix 106 m *2 adopted for thermal hydraulic analysis in Docket 72-1014 CoC amendment 9 is used for PWR fuel assemblies.

4.4.1.3 Bounding Flow Resistance Data Holtec report [4.4.2] has identified W17x17 OFA and GE 12/14 lOxlO fuel assemblies as the design basis fuel for computing the flow resistance coefficients required to compute the in-cell flow of helium in PWR storage cells and of in-channel flow of channeled BWR assemblies placed in a BWR storage cell (See Figure 4.4.4). These resistance coefficients form the basis for the thermal-hydraulic analyses in Docket 72-1014 in the CoC amendments 5. These resistance coefficients are appropriate and conservative for HI-STORM FW analysis because of the following reasons:

1.

The coefficients define the upperbound pressure drop per unit length of fueled space (Eq.

1 in Section 4.4.1.2).

11. The storage cell opening in the MPC-37 (PWR fuel) is equal to or greater than the cell openings of the PWR MPCs (such as MPC-32) licensed in the HI-STORM 100 System in Docket 72-1014 [4.1.8]. 1n the case of BWR fuel storage the channeled fuel located inside the storage cell is modeled explicitly as shown in Figure 4.4.4. The bounding flow resistance coefficients obtained from the cited reference above is applied to the channeled space porous media.

iii. The length of porous media incorporated in the HI-STORM FW FLUENT models meets or exceeds the fuel assembly length of the longest fuel listed in this SAR.

Thus the flow resistance defined in the manner above is significantly conservative for modeling the Ft. Calhoun 14xl4 fuel placed in the limiting minimum height MPC-37 (See Table 4.4.2).

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-27 Rev. 5

I IOLTEC PROPRIETARY INFORMATION The flow resistance for 15x151 short fuel is discussed in Section 4.4.1.7. In the following, explicit calculations for the case of MPC-37 are perfonned to quantify the conservatism introduced by using the "bounding" resistance data in the FLUENT analysis.

4.4.1.4 Evaluation of Flow Resistance in Enlarged Cell MPCs The flow resistance factors used in the porous media model are bounding for all fuel types and MPC baskets. This was accomplished for the PWR foe.Jed MPC-37 by placing the most resistive Westinghouse 17xl 7 fuel assembly in the smaller cell opening MPC-32 approved under the HI-STORM I 00 Docket 72-1014, CoC Amendment No. 5 and computing the flow resistance factors. In the case of BWR fueled MPC-89 the most resistive GE-1 Ox l O fuel assembly in the channeled configuration is explicitly modeled in the MPC-89 fuel storage spaces as shown in Figure 4.4.4. The channeled space occupied by the GE-lOxlO fuel assembly is modeled as a porous region with effective flow resistance properties computed by deploying an independent 3D FLUENT model of the array offuel rods and grid spacers.

In the PWR fuel resistance modeling case physical reasoning suggests that the flow resistance of a fuel assembly placed in the larger MPC-37 storage cell will be less than that computed using the (smaller) counterpart cells cavities in the MPC-32. However to provide numerical substantiation FLUENT calculations are performed for the case of W-l 7x 17 fuel placed inside the MPC-32 cell opening of 8.79" and the enlarged MPC-37 cell opening of 8.94". The FLUENT results for the cell pressure drops under the baseline (MPC-32) and enlarged cell opening (MPC-

37) scenarios are shown plotted in Figure 4-4-7. The plot shows that, as expected, the larger cell cross section case (MPC-37) yields a smaller pressure loss. Therefore, the MPC-37 flow resistance is bounded by the MPC-32 flow resistance used in the FLUENT simulations in the SAR. This evaluation is significant because the MPC-3 7 basket is determined as the limiting MPC and therefore the licensing basis HI-STORM FW temperatures by use of higher-than-actual resistance are overstated.

However, as mentioned in Sub-section 4.4.1.2, a flow resistance of lxl06 m*2 through PWR fuel assemblies is used in the thermal analysis.

4.4.1.5 Screening Calculations to Ascertain Limiting Storage Scenario To define the thermally most limiting HI-STORM FW storage scenario the following cases are evaluated under the limiting heat load patterns defined in Tables 1.2.3

• and 1.2.4:

(i) MPC-89 (ii) Minimum height MPC-37 (iii) Reference height MPC-37 (iv) Maximum height MPC-37

• Pattern A defined in Table 1.2.3 is the limiting fuel storage pattern (See Subsection 4.4.4.1 ).

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-28 Rev. 5

I IOLTEC PROPRIETARY INFORMATION To evaluate the above scenarios, 3D FLUENT screening models of the HI-STORM FW cask are constructed, Peak Cladding Temperatures (PCT) computed and tabulated in Table 4.4.2. The results of the calculations yield the following:

(a) Fuel storage in MPC-37 produces a higher peak cladding temperature than that in MPC-89 (b) Fuel storage in the minimum height MPC-37 is limiting (produces the highest peak cladding temperature).

To bound the HI-STORM FW storage temperatures the limiting scenario ascertained above is adopted for evaluation of all normal, off-nonnal and accident conditions.

4.4.1.6 Grid Sensitivity Studies To achieve grid independent CFD results, a grid sensitivity study is perfonned on the HI-STORM FW thermal model. The grid refinement is performed in the entire domain i.e. for both fluid and solid regions in both axial and radial directions. Non-uniform meshes with grid cells clustered near the wall regions are generated to resolve the boundary flow near the walls.

A number of grids are generated to study the effect of mesh refinement on the fuel and component temperatures. All sensitivity analyses were carried out for the case of MPC-37 with minimum fuel length under the bounding heat load pattern A. Following table gives a brief summary of the different sets of grids evaluated and PCT results.

Mesh No Total Mesh PCT (

0C)

Permissible Limit Clad Temperature Size (OC)

Margin (°C) 1 (Licensing 1,536,882 373 400 27 Basis Mesh) 2 3,354,908 372 400 28 3

7,315,556 372 400 28 Note: Because the flow field in the annulus between MPC shell and overpack inner shell is in the transitional turbulent regime, the value of l at the wall-adjacent cell is maintained on the order of 1 to ensure the adequate level of mesh refinement is reached to resolve the viscosity affected region near the wall.

As can be seen from the above table, the PCT is essentially the same for all the meshes. The solutions from the different grids used are in the asymptotic range. Therefore, it can be concluded that the Mesh l is reasonably converged. To provide further assurance of convergence, the sensitivity results are evaluated in accordance with the ASME V &V 20-2009

[4.4.3]. Towards this end, the Grid Convergence Index (GCI), which is a measure of the solution uncettainty, is computed to be 0.181 % for these meshes. The apparent order of the method calculated as 2.1, is similar to the order of the method.

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I IOLTEG PROPRl~T.ARY INFORMATION Based on the above results, Run No 1 grid layout is adopted for the thermal analysis of the HI-STORM FW.

4.4.1.7 Evaluation of lSxlSI Short Fuel Assembly i) Overview The various fuel assembly types allowed for storage are discussed in Chapter 2. Table 2.1.1 specifically provides a classification of fuel assembly based on its length - minimum, reference and maximum. Due to the unique design of l 5x 15I short fuel, the thermal evaluation for l 5x 15I short fuel is separately discussed in this subsection. All the thermal evaluations for MPC-37 discussed previously in this section are applicable to all fuel assembly arrays/classes except the l 5x 151 fuel defined in Table 2.1.2. The nominal length of 15xl 51 short fuel with fuel shim is 150 inches (See Table 2. 1.1 ). Therefore, the co1Tesponding height of the MPC, HI-STORM and HI-TRAC are detennined based on 150" fuel length.

ii) Evaluation of Flow Resistance through Fuel Assemblies (b)(4)

HOLTEC INTERNATIONAL COPYRIGHTED MATERlAL REPORT HI-2 114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-30 Rev. 5

1 IOLTEO PROPRIET-AR-¥-fNFeRMATteN-(b)(4) iii) Three-Dimensional Thermal Model The converged mesh solution discussed in Sub-Section 4.4.1.6 is modified to model the l 5x15 I short fuel assembly length. The mesb in the planar direction is unchanged while the mesh density in the axial ctirection is maintained. The following additional changes are made to the thennal model discussed in Sub-section 4.4.1.1 tlm1 4.4. l.6 to evaluate the Hl-STORM FW System with 1 Sx I SI fuel assembly class:

(1) The height of basket is conservatively modeled lower ( equal to 149 inches).

(2) The flow resistance through the fuel assemblies is based on the calculations in this sub-section.

(3) The effective fuel thermal properties specific to l5xl5I fuel assembly are used (see Table 4.4.1)

The results of this evaluation are discussed in Sub-section 4.4.4.

4.4.1.8 Thermal Evaluation of Various Basket Shim Design Options To allow flexibility in fabrication, the licensing drawings provide various options to install extruded basket shims between the basket and MPC wall. A summary is provided in Table 1.2.9. From a thermal standpoint, emissivity of shims and the average total gap between the basket and extruded shim and extruded shim and MPC shell are critical to heat transfer from the fuel basket to MPC. As noted in Table 1.2.9, solid shim aluminum plates may be placed between the basket and extruded shim to ensure the criteria on the gap in the basket periphery is met.

The predicted temperatures and pressure under normal operating conditions are bounding when MPC is in the HI-TRAC. Therefore, extensive thermal analysis to address all the allowable design options presented in Table 1.2.9 are performed when the MPC is in the HI-TRAC and discussed in Section 4.5. All the licensing basis thermal evaluations for HI-STORM are performed based on Option l in Table 1.2.9 since it results in the most limiting PCT and MPC pressure (see supporting evaluations in Section 4.5).

4.4.1.9 Evaluation of Overpack Heat Shields HI-STORM FW overpack is equipped with a heat shield on the overpack inner shell and underneath the overpack lid concrete. They are optional features engineered to protect the overpack body concrete and overpack lid concrete from excessive temperature rise due to radiant HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-3 1 Rev. 5

AOL I EC PROP~IETARY lrffORMATION heat from the MPC. Absence of the heat shields will have an adverse impact on the overpack temperatures. To quantify the impact, a thennal evaluation is performed for a HI-STORM overpack without the heat shields. The thermal model is exactly the same as the converged mesh discussed above in paragraph 4.4.1.6 except that heat shields are removed from the thennal model. The results of this thermal evaluation are discussed in paragraph 4.4.4.4.

4.4.1.10 Evaluation of Version XL HI-STORM FW Lid As discussed previously in this chapter and Chapter 1, Version XL of overpack lid can only be used with Version XL cask body design. The cask body Version XL is a slightly longer cask compared to the standard overpack design. This ensures the axial space between the top of the MPC and bottom of the overpack lid is consistent with the standard lid design. The HI-STORM FW Version XL lid is similar in design to the standard overpack lid but with enhanced shielding.

Additionally, the heat shields on the overpack body and lid are completely removed. An explicit thermal model is developed to include the Version XL lid design and evaluated in Sub-section 4.4.4.1.

4.4.2 Effect of Neighboring Casks HI-STORM FW casks are typically stored on an ISFSI pad in regularly spaced arrays (See Section 1.4, Figures 1.4.1 and 1.4.2). Relative to an isolated HI-STORM FW the heat dissipation from a HI-STORM FW cask placed in an array is somewhat disadvantaged. However, as the analysis in this Sub-section shows, the effect of the neighboring casks on the peak cladding temperature in the "surrounded" cask is insignificant.

(i) Effect oflnsolation The HI-STORM FW casks are subject to insolation heating during daytime hours. Presence of surrounding casks has the salutary effect of pattially blocking insolation flux. This effect, results in lower temperatures and in the interest of conservatism is ignored in the analysis.

(ii) Effect of Radiation Blocking The presence of suffounding casks has the effect of partially blocking radiation heat dissipation from the Overpack cylindrical surfaces. Its effect is evaluated in Sub-section 4.4.2.1.

(iii) Effect of Flow Area Reduction The presence of surrounding casks have the effect of reducing the access flow area arow1d the casks from an essentially unbounded space around it to certain lateral flow passages defined by the spacing between casks (See Figures 1.4. l and 1.4.2). A reduction in flow area for ventilated casks is not acceptable if the access area falls below the critical flow area in the ventilation flow passages. The HJ-STORM FW critical flow area is reached in the narrow annular passage. The lateral flow passages access flow area defined by the product of minimum gap between casks and cask height is computed below. The calculation uses the lowerbound 180 inch cask pitch defined in Table 1.4.1.

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I IOLTEC PROPRIETARY INFORMA I ION Annulus Area (Amin):

MPC OD: 75.5 in Overpack ID: 81 in Amin: 676.0 in2 Lateral Access Area (A0):

Cask Pitch: 180 in Overpack OD: 139 in Overpack Body Height: 187.25 in Min. cask spacing: 180 - 139 = 41 in A0 : 7677.2 in2 The above numerical exercise shows that A 0 >> Amin and therefore there is an adequate access area surrounding the interior casks for the ventilation air to feed the inlet ducts..

4.4.2.1 Analytical Evaluation of the Effect of Surrounding Casks In a rectilinear array of HI-STORM FW casks the unit situated in the center of the grid is evidently hydraulically most disadvantaged, because of potential interference to air intake from surrounding casks. Furthermore, the presence of surrounding casks has the effect of partially blocking radiation heat dissipation from the centrally located cask. This situation is illustrated in Figure 4.4.5. To simulate these effects in a conservative manner, a hypothetical square cavity defined by the tributary area A0 of cask shown in Figure 4.4.5 is erected around the centrally located HI-STORM FW. The hypothetical square cavity has the following attributes:

l. The hypothetical square cavity (with the subject HI-STORM FW situated co-axially in it) is constructed for thel5 ft minimum cask pitch defined in Section 1.4.1.

2. The cavity walls are impervious to air. In this manner as shown in Figure 4.4.6 lateral access to ambient air is choked.

3. The cavity walls are defined as reflecting surfaces from the inside and insulated from the outside. In this manner lateral dissipation of heat by radiation is blocked.

4. The hypothetical square cavity is open at the top as shown in Figure 4.4.6 to allow ambient air access for ventilation cooling in a conservative manner.

The principal results of the hypothetical square cavity thermal model are tabulated below and compared with the baseline thermal results tabulated in Section 4.4.4.

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I IOLTEC PROPRIETARY INFORMATION Model Peak Clad Margin-to-Limit (°F)

Temperature (°F)

Single Cask Model 703 49 Hypothetical Square 702*

50 Cavity Thermal Model Peak cladding temperature reported for the limiting heat load MPC-37 Pattern A (See Subsection 4.4.4.1)

The results show that the presence of surrounding casks has essentially no effect on the fuel cladding temperatures (the difference in the results is within the range of numerical round-off).

These results are in line with prior thermal evaluations of the effect of surrounding casks in the NRC approved HI-STORM 100 System in Docket 72-1014.

4.4.3 Test Model The HI-STORM FW thermal analysis is performed on the FLUENT [ 4.1.2] Qomputational fluid Dynamics (CFD) program. To ensure a high degree of confidence in the HJ-STORM FW thermal evaluations, the FLUENT code has been benchmarked using data from tests conducted with casks loaded with irradiated SNF ([4.l.3],[4.1.7]). The benchmark work is archived in QA validated Holtec reports ([ 4.1.5],[ 4.1.6]).These evaluations show that the FLUENT solutions are conservative in all cases. In view of these considerations, additional experimental verification of the thermal design is not necessary. FLUENT has also been used in all Holtec International Part 71 and Part 72 dockets since 1996.

4.4.4 Maximum and Minimum Temperatures 4.4.4.1 Maximum Temperatures (i) Evaluation of Standard HI-STORM FW Lid The 3-D model from the previous subsection is used to determine temperature distributions under long-term normal storage conditions for both MPC-89 and MPC-37. Tables 4.4.2, 4.4.3 and 4.4.5 provide key thermal and pressure results from the FLUENT simulations, respectively.

Tables 4.4.12 and 4.4.13 respectively provide the temperature and pressure results from the FLUENT simulation of the l5xl5I short fuel assembly height based on the methodology discussed in Sub-Section 4.4.1.7. The peak fuel cladding result in these tables is actually overstated by the fact that the 3-D FLUENT cask model incorporates the effective conductivity of the fuel assembly sub-model. Therefore the FLUENT models report the peak temperature in the fuel storage cells. Thus, as the fuel assembly models include the fuel pellets, the FLUENT

• The lower computed temperature is an artifact of the use of overstated inlet and outlet loss coefficients in the single cask model. The result supports the conclusion that surrounding casks have essentially no effect on the Peak Cladding Temperatures.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-34 Rev. 5

HOL TEC PROPRIETARY INFORMATION calculated peak temperatures are actually peak pellet centerline temperatures which bound the peak cladding temperatures with a modest margin.

The following observations can be derived by inspecting the temperature field obtained from the thermal models:

The fuel cladding temperatures are below the regulatory limit (ISG-1 l [4.l.4]) under all regionalized storage scenarios defined in Chapter 1 (Figures 1.2.1 and 1.2.2) and thermal loading scenarios defined in Tables 1.2.3 and 1.2.4.

The limiting fuel temperatures are reached under the Pattern A thermal loading condition defined in Table 1.2..3 in the MPC-37. Accordingly this scenario is adopted for thermal evaluation under on-site transfer (Section 4.5) and under off-normal and accident conditions (Section 4.6).

The maximum temperature of the basket sh*uctural material is within its design limit.

The maximum temperatures of the MPC pressure boundary materials are below their design limits.

The maximum temperatures of concrete are within the guidance of the governing ACI Code (see Table 2.2.3).

The calculated fuel temperature for the 15xl 51 short fuel assembly (Table 4.4.12) is bounded by the thermal evaluations for the minimum MPC-37 for sho1t fuel (Table 4.4.3). The temperatures of other cask components are similar. It is reasonable to conclude that the temperatures and pressure for the minimum height MPC-37 (short fuel) bounds all scenarios.

The above observations lead us to conclude that the temperature field in the HI-STORM FW System with a loaded MPC containing heat emitting SNF complies with all regulatory temperature limits (Table 2.2.3). In other words, the thermal environment in the HI-STORM FW System is in compliance with Chapter 2 Design Criteria.

Also, all the licensing basis thermal evaluations documented in this chapter are perfo1med for the most limiting thermal scenarios i.e. minimum MPC-37 with heat load pattern A.

(ii) Evaluation of Version XL HI-STORM FW Lid An explicit 3-D thermal model of Version XL lid with Version XL cask body is evaluated in this sub-section. All the inputs and methodology used in the evaluation are consistent with that used for the standard lid thermal evaluations. Moreover, the MPC and overpack thermal model is exactly the same as that used in the standard lid evaluations. This 3-D model for the Version XL HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-35 Rev. 5

HO! rec PROPRIET,t\\RY INFORMATION lid design is used to determine temperature distributions under long-term normal storage conditions for MPC-37 under the most limiting heat load pattern (Pattern A). Table 4.4.15 provides key thermal and pressure results from the FLUENT simulations. The peak cladding temperature and other component temperatures, except the overpack steel shells and concrete temperatures, are similar to that predicted from the thermal evaluations of the standard lid design. Therefore, the results demonstrate that the thermal performance of HI-STORM FW System with the Version XL lid is similar to the HI-STORM FW system with the standard lid design. All the licensing basis thermal evaluations in this chapter are perfom1ed with the standard lid design. Although, the overpack component temperatures are slightly higher for the Version XL lid than the standard lid, the increase in overpack component temperatures is within the margins available to temperature limits. Therefore, all the safety conclusions made for off-no1mal and accident conditions still remain valid.

4.4.4.2 Minimum Temperatures In Table 2.2.2 of this report, the minimum ambient temperature condition for the HI-STORM FW storage overpack and MPC is specified to be -40°F. If, conservatively, a zero decay heat load with no solar input is applied to the stored fuel assemblies, then every component of the system at steady state would be at a temperature of -40°F. Low service temperature (-40°F) evaluation of the HI-STORM FW is provided in Chapter 3. All HI-STORM FW storage overpack and MPC materials of construction will satisfactorily perform their intended function in the storage mode under this minimum temperature condition.

4.4.4.3 Effect of Elevation The reduced ambient pressure at site elevations significantly above the sea level will act to reduce the ventilation air mass flow, resulting in a net elevation of the peak cladding temperature. However, the ambient temperature (i.e., temperature of the feed air entering the overpack) also drops with the increase in elevation. Because the peak cladding temperature also depends on the feed air temperature (the effect is one-for-one within a small range, i.e., 1 °F drop in the feed air temperature results in - 1 °F drop in the peak cladding temperature), the adverse ambient pressure effect of increased elevation is pattially offset by the ambient air temperature decrease. The table below illustrates the variation of air pressure and corresponding ambient temperature as a function of elevation.

Elevation (ft)

Pressure (psi a)

Ambient Temperature Reduction versus Sea Level Sea Level (0) 14.70 0°F 2000 13.66 7.1 °F 4000 12.69 14.3°F HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 Rev. 5 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-36

lelObTi;C PROPRIETARY INFORMATION A survey of the elevation of nuclear plants in the U.S. shows that nuclear plants are situated near about sea level or elevated slightly (- 1000 ft). The effect of the elevation on peak fuel cladding temperatures is evaluated by perfom1ing calculations for a HI-STORM FW system situated at an elevation of 1500 feet. At this elevation the ambient temperature would decrease by approximately 5°F (See Table above). The peak cladding temperatures are calculated under the reduced ambient temperature and pressure at 1500 feet elevation for the limiting regionalized storage scenario evaluated in Table 4.4.2. The results are presented in Table 4.4.9.

These results show that the PCT, including the effects of site elevation, continues to be well below the regulatory cladding temperature limit of 752°F. In light of the above evaluation, it is not necessary to place ISFS] elevation constraints for HI-STORM FW deployment at elevations up to 1500 feet. If, however, an ISFSI is sited at an elevation greater than 1500 feet, the effect of altitude on the PCT shal I be quantified as part of the IO CFR 72.212 evaluation for the site using the site ambient conditions.

4.4.4.4 Evaluation of Overpack Heat Shields As discussed in Sub-section 4.4.1.9 above, a thermal evaluation is performed to evaluate the effect of removal of heat shields from a HI-STORM overpack. The predicted temperatures from this sensitivity study of notmal condition of storage are summarized in Table 4.4.14. The peak cladding temperature, basket and MPC component temperatures decrease due to removal of heat shields. As expected, the results demonstrate an increase in overpack component temperatures.

However, the overpack component temperatures are below their respective nonnal temperature limits with significant margins. Therefore, removal of heat shields does not have a detrimental effect on the system' thermal performance.

The temperatures of overpack components increase due to removal of heat shields under nonnal conditions of storage. This temperature increase is then added to the predicted temperatures of all the off-nonnal and accident conditions discussed in Section 4.6. The resulting temperatures are still well below their respective temperature limits which demonstrate that safety conclusions made for all the off-normal and accident condition evaluations in Section 4.6 remain valid even after the removal of heat shields from the HI-STORM overpack.

4.4.5 Maximum Internal Pressure 4.4.5.1 MPC Helium Backfill Pressure The quantity of helium emplaced in the MPC cavity shall be sufficient to produce an operating pressure of 7.1 and 7.0 atmospheres (absolute) respectively for loading patterns A and B during no1mal storage conditions defined in Table 4.1.1. Thermal analyses performed on the different MPC designs indicate that this operating pressure requires a certain minimum helium backfill pressure (Pb) specified at a reference temperature (70°F). The minimum backfill pressure for each MPC type is provided in Table 4.4.7. A theoretical upper limit on the helium backfill HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-37 Rev. 5

---

HOLTEC PROPRle+,ARY INFORMATION pressure also exists and is defined by the design pressure of the MPC vessel (Table 2.2.1 ). The upper limit of Pb is also reported in Table 4.4. 7. To bound the minimum and maximum backfill pressures listed in Table 4.4. 7 with a margin, a helium backfill specification is set forth in Table 4.4.8.

To provide additional helium backfill range for less than design basis heat load canisters a Sub-Design-Basis (SDB) heat load scenario is defined below:

(i)

MPC-37 under 80% Pattern A Heat Load (Table 1.2.3)

(ii)

MPC-37 under 90% Pattern A Heat Load (Table 1.2.3)

(iii)

MPC-89 under 80% Design Heat Load (Table 1.2.4)

(iv)

MPC-37 under vacuum drying threshold heat load in Table 4.5.1 *.

(v)

MPC-89 under vacuum drying threshold heat load in Table 4.5.1 *.

The storage cell and MPC heat load limits under the SDB scenario (i), (ii) & (iii) are specified in Table 4.4.11. Calculations for bounding scenarios (i), (ii) & (iii) show that the maximum cladding temperature under the SDB scenario meet the ISG-11 temperature limits. The helium backfill pressure limits supporting this scenario are defined in Table 4.4.10. These backfill limits maybe optionally adopted by a cask user if the decay heats of the loaded fuel assemblies meet the SDB decay heat limits stipulated above.

Two methods are available for ensuring that the appropriate quantity of helium has been placed in an MPC:

1.

By pressure measurement

11.

By measurement of helium backfill volume (in standard cubic feet)

The direct pressure measurement approach is more convenient if the FHD method of MPC drying is used. In this case, a certain quantity of helium is already in the MPC. Because the helium is mixed inside the MPC during the FHD operation, the temperature and pressure of the helium gas at the MPC's exit provides a reliable means to compute the inventory of helium. A shortfall or excess of helium is adjusted by a calculated raising or lowering of the MPC pressure such that the reference MPC backfill pressure is within the range specified in Table 4.4.8 or Table 4.4.10 (as applicable).

When vacuum drying is used as the method for MPC drying, then it is more convenient to fill the MPC by introducing a known quantity of helium (in standard cubic feet) by measuring the quantity of helium introduced using a calibrated mass flow meter or other measuring apparatus.

The required quantity of helium is computed by the product of net free volume and helium specific volume at the reference temperature (70°F) and a target pressure that lies in the mid-range of the Table 4.4.8 pressures.

• Threshold scenarios (iv) and (v) are bounded by scenarios (i) and (iii) respectively because the core Region I assembly heat loads and total cask heat loads are bounded by the Sub-Design Basis heat loads in Table 4.4.11.

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I IOLTEC PROPRIETARY INFORMATION The net free volume of the MPC is obtained by subtracting B from A, where A = MPC cavity volume in the absence of contents (fuel and non-fuel hardware) computed from nominal design dimensions B = Total volume of the contents (fuel including DFCs, if used) based on nominal design dimensions Using commercially available mass flow totalizers or other appropriate measuring devices, an MPC cavity is filled with the computed quantity of helium.

4.4.5.2 MPC Pressure Calculations The MPC is initially filled with dry helium after fuel loading and drying prior to installing the MPC closure ring. During normal storage, the gas temperature within the MPC rises to its maximum operating basis temperature. The gas pressure inside the MPC will also increase with rising temperature. The pressure rise is determined using the ideal gas law. The MPC gas pressure is also subject to substantial pressure rise under hypothetical rupture of fuel rods and large gas inventory non-fuel hardware (PWR BPRAs). To minimize MPC gas pressures the number of BPRA containing fuel assemblies must be limited to 30.

Table 4.4.4 presents a summary of the MPC free volumes determined for the fixed height MPC-89 and lowerbound height MPC-37 fuel storage scenarios. The MPC maximum gas pressure is computed for a postulated release of fission product gases from fuel rods into this free space. For these scenarios, the amounts of each of the release gas constituents in the MPC cavity are summed and the resulting total pressures determined from the ideal gas law. A concomitant effect of rod ruptures is the increased pressure and molecular weight of the cavity gases with enhanced rate of heat dissipation by internal helium convection and lower cavity temperatures.

As these effects are substantial under large rod ruptures the 100% rod mpture accident is evaluated with due credit for increased heat dissipation under increased pressure and molecular weight of the cavity gases. Based on fission gases release fractions (NUREG 1536 criteria

[4.4.1]), rods' net free volume and initial fill gas pressure, maximum gas pressures with 1%

(normal), 10% (off-nonnal) and 100% (accident condition) rod tupture are given in Table 4.4.5.

The results of the calculations support the following conclusions:

(i)

The maximum computed gas pressures reported in Table 4.4.5 under all design basis thermal loadings defined in Section 4.4 are all below the MPC internal design pressures for normal, off-normal and accident conditions specified in Table 2.2.1.

(ii)

The MPC gas pressure obtained under loading Pattern A is essentially same as in Pattern B. Accordingly Pattern A loading condition for pressure boundary evaluation of MPC in the HI-TRAC and under off-normal and accident conditions is retained.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-39 Rev. 5

lelObTi;C PROPRIETARY INFORMATION Evaluation of Non-Fuel Hardware The inclusion of PWR non-fuel hardware (BPRA control elements and thimble plugs) to the PWR basket influences the MPC internal pressure through two distinct effects. The presence of non-fuel hardware increases the effective. basket conductivity, thus enhancing heat dissipation and lowering fuel temperatures as well as the temperature of the gas filling the space between fuel rods. The gas volume displaced by the mass of non-fuel hardware lowers the cavity free volume. These two effects, namely, temperature lowering and free volume reduction, have opposing influence on the MPC cavity pressure. The first effect lowers gas pressure while the second effect raises it. In the HI-STORM FW thermal analysis, the computed temperature field (with non-fuel hardware excluded) has been dete1mined to provide a conservatively bounding temperature field for the PWR baskets. The MPC cavity free space is computed based on conservatively computed volume displacement by fuel with non-fuel hardware included. This approach ensures conservative bounding pressures.

During in-core irradiation of BPRAs, neutron capture by the B-10 isotope in the neutron absorbing material produces helium. Two different fo1ms of the neutron absorbing material are used in BPRAs: Borosilicate glass and B4C in a refractory solid matrix (At20 3). Borosilicate glass (primarily a constituent of Westinghouse BPRAs) is used in the shape of hollow pyrex glass tubes sealed within steel rods and supported on the inside by a thin-walled steel liner. To accommodate helium diffusion from the glass rod into the rod internal space, a relatively high void volume (-40%) is engineered in this type of rod design. The rod internal pressure is thus designed to remain below reactor operation conditions (2,300 psia and approximately 600°F coolant temperature). The B4C-Ali03 neutron absorber material is principally used in B&W and CE fuel BPRA designs. The relatively low temperatures of the poison material in BPRA rods (relative to fuel pellets) favor the entrapment of helium atoms in the solid matrix.

Several BPRA designs are used in PWR fuel. They differ in the number, diameter, and length of poison rods. The older Westinghouse fuel (W-14xl4 and W-15x 15) has used 6, 12, 16, and 20 rods per assembly BPRAs and the later (W-l 7x 17) fuel uses up to 24 rods per BPRA. The BPRA rods in the older fuel are much larger than the later fuel and, therefore, the B-10 isotope inventory in the 20-rod BPRAs bounds the newer W-l 7x 17 fuel. Based on bounding BPRA rods internal pressure, a large hypothetical quantity of helium (7.2 g-moles/BPRA) is assumed to be available for release into the MPC cavity from each BPRA containing fuel assembly. For a bounding evaluation the maximum pe1m issible number of BPRA containing fuel assemblies (see discussion at the beginning of this Section) are assumed to be loaded. The MPC cavity pressures (including helium from BPRAs) are summarized in Table 4.4.5 for the bounding MPC-37 (minimum MPC height and heat load Patterns A and B) and MPC-89 (design heat load) storage scenanos.

4.4.6 Engineered Clearances to Eliminate Thermal Interferences Thermal stress in a structural component is the resultant sum of two factors, namely: (i) restraint of free end expansion and (ii) non-uniform temperature distribution. To minimize thermal HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-40 Rev. 5

I IOLTEC PRO~RIETARY INFORMATIOl<l stresses in load bearing members, the HI-STORM FW system is engineered with adequate gaps to permit free thermal expansion of the fuel basket and MlPC in axial and radial directions. In this subsection, differential thermal expansion calculations are performed to demonstrate that engineered gaps in the HI-STORM FW System are adequate to accommodate thermal expansion of the fuel basket and MPC.

The HI-STORM FW System is engineered with gaps for the fuel basket and MPC to expand thermally without restraint of free end expansion. The following gaps are evaluated:

a. Fuel Basket-to-MPC Radial Gap

b. Fuel Basket-to-MPC Axial Gap

c. MPC-to-Overpack Radial Gap

d. MPC-to-Overpack Axial Gap The FLUENT thermal model provides the 3-D temperature field in the HI-STORM FW system from which the changes in the above gaps are directly computed. Table 4.4.6 provides the initial minimum gaps and their corresponding value during long-term storage conditions. Significant margins against restraint to free-end expansion are available in the design.

4.4.7 Evaluation of System Performance for Normal Conditions of Storage The HI-STORM FW System thermal analysis is based on a detailed 3-D heat transfer model that conservatively accounts for all modes of heat transfer in the MPC and overpack. The thermal model incorporates conservative assumptions that render the results for long-term storage to be conservative.

Temperature distribution results obtained from this thermal model show that the maximum fuel cladding temperature limits are met with adequate margins. Expected margins during nonnal storage will be much greater due to the conservative assumptions incorporated in the analysis. As justified next the long-term impact of elevated temperatures reached in the HI-STORM FW system is minimal. The maximum MPC basket temperatures are below the recommended limits for susceptibility to stress, corrosion and creep-induced degradation. A complete evaluation of all material failure modes and causative mechanisms has been performed in Chapter 8 which shows that all selected materials for use in the HI-STORM FW system will render their intended function for the service life of the system. Furthe1more, stresses induced due to the associated temperature gradients are modestly low (See Structural Evaluation Chapter 3).

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-41 Rev. 5

lelObTi;C PROPRIETARY INFORMATION Table 4.4.1 EFFECTIVE FUEL PROPER TIES UNDER BOUNDING FUEL STORAGE CONFIGURA TIONSNoie 1 Conductivity (Btu/hr-ft-°F)

PWR: Short Fuel PWR: Standard Fuel Temperature (°F)

Planar Axial Planar Axial 200 0.247 0.813 0.231 0.759 450 0.443 0.903 0.387 0.845 700 0.730 1.016 0.601 0.951 PWR: XL Fuel BWR Fuel Planar Axial Planar Axial 200 0.239 0.787 0.283 0.897 450 0.393 0.875 0.426 0.988 700 0.599 0.984 0.607 1.104 PWR: 15xl5I Short Fuel Temperature (°F)

Planar Axial 200 0.226 0.763 450 0.386 0.848 700 0.601 0.955 Thermal Inertia Prope1ties Density (lb/ft3)

Heat Capacity (Btu/lb-°Ftore 2 PWR: l5xl5I Short 194.5 0.056 Fuel PWR: Short Fuel 165.8 0.056 PWR: Standard Fuel 176.2 0.056 PWR: XL Fuel 187.5 0.056 BWRFuel 255.6 0.056 Note 1: Bounding fuel storage configurations defined in 4.4.1. l(ii).

Note 2: The lowerbound heat capacity of principal fuel assembly construction materials tabulated in Table 4.2.5 (U0 2 heat capacity) is conservatively adopted.

Note 3: The fuel properties tabulated herein are used in screening calculations to define the limiting scenario for fuel storage (See Table 4.4.2).

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-42 Rev. 5

I IOLTEC PROPRIETARY INFORMATION Table 4.4.2 RESULTS OF SCREENING CALCULATIONS UNDER NORMAL STORAGE CONDITIONS Storage Scenario Peak Cladding Temperature, °C (°F)

MPC-37 Minimum Height*

353 (667)

Reference Height 342 (648)

Maximum Height 316 (601)

MPC-89 333 (63 1)

Notes:

( l) The highest temperature highlighted above is reached under the case of minimum height MPC-37 designed to store the short height Ft. Calhoun 14xl4 fuel. This scenario is adopted in Chapter 4 for the licensing basis evaluation of fuel storage in the HI-STORM FW system.

(2) All the screening calculations were performed using a reference coarse mesh [ 4.1.9] and flow resistance based on the calculations in Holtec report [ 4.4.2].

• Bounding scenario adopted in this Chapter for all thermal evaluations.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-43 Rev. 5

I IOL'fEe PROPRIE I ARV INFORMATION Table 4.4.3 MAXIMUM TEMPERATURES IN HI-STORM FW UNDER LONG-TERM NORMAL STORAGE*

Component Temperature, °C (°F)

Pattern A/ Pattern B Fuel Cladding 373 (703) / 368 (694)

MPC Basket 358(676)/354(669)

Basket Periphery 290 (554) I 292 (558)

Aluminum Basket Shims 267 (513) / 267 (513)

MPC Shell 240 (464) I 242 (468)

MPC LidNote I 235 (455) I 232 (450)

Overpack Inner Shell 126 (259) / 127 (261)

Overpack Outer Shell 65 (1 49) / 65 (149)

Overpack Body ConcreteNote 1 89 (192) / 90 (194)

Overpack Lid ConcreteNote 1 111 (232) / 112 (234)

Area Averaged Air outlet t 103 (217)/ 103 (217)

Note J: Maximum section average temperature is reported.

t The temperatures reported in this table (all for short fuel scenarios ofMPC-37) are below the design temperatures specified in Table 2.2.3, Chapter 2. These temperatures bound MPC-89 temperatures.

Reported herein for the option of temperature measurement surveillance of outlet ducts air temperature as set forth in the Technical Specifications.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-44 Rev. 5

HOLTEC F'RO~RIETARY lt~FORMATION Table 4.4.4 MINIMUM MPC FREE VOLUMES Item Lowerbound Height MPC-89 MPC-37 (ft3)

(ft3)

Net Free 211.89 210.12 Volume*

• Net.free volumes are obtained by subtracting basket, fuel, aluminum shims, spacers, basket supports and DFCs metal volume from the MPC cavity volume.

Table 4.4.5

SUMMARY

OF MPC INTERNAL PRESSURES UNDER LONG-TERM STORAGE*

Condition MPC-37 MPC-89 (psig)

(psig)

Pattern A/Pattern B Initial backfill** (at 70°F) 45.5/46.0 47.5 Normal:

intact rods 96.6/97.9 98.4 l % rods rupture 97.7/99.0 99.0 Off-Normal (10% rods rupture) 107.5/108.9 104.0 Accident 191.5/194.4 155.0

( 100% rods rupture)

• Per NUREG-1536, pressure analyses with ruptured fuel rods (including BPRA rods for PWR fuel) is performed with release of 100% of the ruptured fuel rod fill gas and 30% of the significant radioactive gaseous fission products.

• • Conservatively assumed at the Tech. Spec. maximum value (see Table 4.4.8).

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-45 Rev. 5

I IOLTEC PROPRIETARY INFORMATION Table 4.4.6

SUMMARY

OF HI-STORMFW DIFFERENTIAL THERMAL EXPANSIONS Gap Description Cold Gap U (in)

Differential Is Free Expansion Expansion Oi (in)

Criterion Satisfied (i.e., U > 6i)

Fuel Basket-to-MPC

0. 125 0.112 Yes Radial Gap Fuel Basket-to-MPC 1.5 0.421 Yes Minimum Axial Gap MPC-to-Overpack 5.5 0.128 Yes Radial Gap MPC-to-Overpack 3.5 0.372 Yes Minimum Axial Gap Table 4.4.7 THEORETICAL LIMITS* OF MPC HELIUM BACKFILL PRESSURE**

MPC Minimum Backfill Pressure Maximum Backfill Pressure (psig)

(psig)

MPC-37 41.0 47.3 Pattern A MPC-37 40.8 47.1 Pattern B MPC-89 41.9 48.4

• The helium backfill pressures are set forth in the Technical Specifications with a margin (see Table 4.4.8).

• • The pressures tabulated herein are at 70°F reference gas temperature.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-46 Rev. 5

lelObTEG PROPRIETARY INFORMATIOl<l Table 4.4.8 MPC HELIUM BACKFILL PRESSURE SPECIFICATIONS MPC Item Specification Minimum Pressure 42.0 psig @ 70°F Reference Temperature MPC-37 Pattern A 45.5 psig @ 70°F Reference Temperature Maximum Pressure Minimum Pressure 41.0 psig @ 70°F Reference Temperature MPC-37 Pattern B 46.0 psig @ 70°F Reference Temperature Maximum Pressure Minimum Pressure 42.5 psig@ 70°F Reference Temperature MPC-89 47.5 psig@ 70°F Reference Temperature Maximum Pressure Table 4.4.9 MAXIMUM HI-STORM FW TEMPERA TURES AT ELEVATED SITES*

Component Temperature, °C (°F)

Fuel Cladding 374 (705)

MPC Basket 360 (680)

Aluminum Basket Shims 275 (527)

MPC Shell 246 (475)

MPC LidNotc I 242 (468)

Overpack Inner Shell 126 (259)

Overpack Body ConcreteNotc 1 86 (187)

Overpack Lid ConcreteNote 1 112 (234)

Note 1: Maximum section average temperature is reported.

The temperatures reported in this table (all for the bounding scenario defined in Table 4.4.2) are below the design temperatures specified in Table 2.2.3, Chapter 2.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-47 Rev. 5

I IOLTEC PROPRIETARY INFORMATION Table 4.4.10 MPC HELIUM BACKFILL PRESSURE LIMITS UNDER THE SUB-DESIGN-BASIS HEAT LOAD SCENARIONoic 1 MPC Item Specification MPC-37 Minimum Pressure 42.0 psig @ 70°F Reference Temperature 80% of Pattern A Maximum Pressure 50.0 psig @ 70°F Reference Temperature MPC-37 Minimum Pressure 42.0 psig @ 70°F Reference Temperature 90% of Pattern A Maximum Pressure 47.8 psig @ 70°F Reference Temperature MPC-89 Minimum Pressure 42.0 psig @ 70°F Reference Temperature 80% of Table 1.2.4 Maximum Pressure 50.0 psig @ 70°F Reference Temperature MPC-37 Minimum Pressure 42.0 psig@ 70°F Reference Temperature Table 4.5. l Threshold Heat Load Maximum Pressure 50.0 psig @ 70°F Reference Temperature MPC-89 Minimum Pressure 42.0 psig @ 70°F Reference Temperature Table 4.5. l Threshold Maximum Pressure 50.0 psig @ 70°F Reference Temperature Heat Load Note 1: The Sub-Design-Basis heat load scenario is defined in Section 4.4.5.1.

Note 2: Sub-design-basis heat load MPCs are sufficiently backfilled to yield an absolute operating pressure of 6 atJ.n in 80% heat load cases and 6.9 atm in 90% heat load cases.

Note 3: The 80% heat load backfill specifications are suitably adopted for threshold heat load scenarios because the thermal scenarios bound the latter (See Subsection 4.4.5.1 ).

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-48 Rev. 5

I IOLTEC PROPRIETARY INFORMATION Table 4.4.11 SUB-DESIGN BASIS HEAT LOAD LIMITS MPC-37 (80% of Pattern A in Table 1.2.3)

Region 1 Cells 0.840 kW/assy Region 2 Cells 1.360 kW/assy 0.712 kW/assy Region 3 Cells 35.27 kW Total MPC-37 (90% of Pattern A in Table l.2.3)

Region 1 Cells 0.945 kW /assy Region 2 Cells 1.530 kW/assy 0.801 kW/assy Region 3 Cells 39.68 kW Total MPC-89 (80% of Table 1.2.4)

Region I Cells 0.352 kW/assy 0.496 kW /assy Region 2 Cells 0.352 kW/assy Region 3 Cells 37.l kW Total Note: The MPC-3 7 and MPC-89 storage cell regions are defined in Figures 1.2.1 and 1.2.2 respectively.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-49 Rev. 5

HOLTEC F'RO~RIETARY lt~FORMATION Table 4.4.12 MAXIMUM TEMPERA TURES IN HI-STORM FW UNDER LONG-TERM NORMAL STORAGE FOR ] 5x151 SHORT FUEL ASSEMBLY LENGTH*

Component Temperature, °C (°F)

Pattern A Fuel Cladding 368 (694)

MPC Basket 352 (666)

Basket Periphery 295 (563)

Aluminum Basket Shims 283 (541)

MPC Shell 250 (482)

MPC LidNote 1 247 (477)

Overpack Inner Shell 130 (266)

Overpack Outer Shell 66 ( 151)

Overpack Body ConcreteNote 1 91 (196)

Overpack Lid ConcreteNore 1 113 (235)

Area Averaged Air outlet 104 (219)

Note l: Maximum section average temperature is reported.

• The temperatures reported in this table are below the design temperatures specified in Table 2.2.3, Chapter 2.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-50 Rev. 5

I IOLTEC PROPRIETARY INFORMA I ION Table 4.4.13

SUMMARY

OF MPC INTERNAL PRESSURES UNDER LONG-TERM STORAGE FOR 15xl51 SHORT FUEL ASSEMBLY*

Condition Gauge Pressure (psig)

Maximum Initial backfill at 21.1 °C (70°F)**

45.5 Normal condition (no rods rupture) 96.2 Normal condition (1 % rods ruptured)***

97. l Off-normal (10% rods ruptured)***

105.6 Accident (100% rods ruptured)***

190.8

• Per NUREG-1536, pressure analyses with ruptured fuel rods (including BPRA rods for PWR fuel) is performed with release of l 00% of the ruptured fuel rod fill gas and 30% of the significant radioactive gaseous fission products.

• • Conservatively assumed at the Tech. Spec. maximum value (see Table 4.4.8).

• Fuel assembly class 15x 151 short fuel defined in Table 2.1.2 do not have BPRAs. Therefore the MPC cavity pressure due to rod ruptures does not include any contribution from BPRAs for this type of fuel assembly.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-51 Rev. 5

t I IOLTEC PROPRIETARY INFORMATION Table 4.4.14 MAXIMUM TEMPERATURES IN HI-STORM FW UNDER LONG-TERM NORMAL STORAGE FOR AN OVERPACK WITHOUT HEAT SHIELDS" Component Temperature, °C (°F)

Fuel Cladding 368 (694)

MPC Basket 354 (669)

Basket Periphery 286 (547)

Aluminum Basket Shims 262 (504)

MPC Shell 234 (453)

MPC LidNote I 225 (437)

Overpack Inner Shell 156 (313)

Overpack Outer Shell 65 (149)

Overpack Body ConcreteNote 1 104 (219)

Overpack Lid ConcreteNote 1 l 06 (223)

Area Averaged Air outlet t 97 (207)

Note I: Maximum section average temperature is reported.

Table 4.4.15 MAXIMUM TEMPERA TURES AND MPC CAVITY PRESSURE FOR HI-STORM FW VERSION XL UNDER LONG-TERM NORMAL STORAGE*

Component Temperature, °C (

0F)

Fuel Cladding 372 (702)

MPC Basket 357 (675)

Basket Periphery 289 (552)

Aluminum Basket Shims 266(511)

MPC Shell 239 (462)

The temperatures reported in this table (licensing basis scenario - short fuel in an MPC-37) arc below the design temperatures specified in Table 2.2.3, Chapter 2.

Reported herein for the option of temperature measurement surveillance of outlet ducts air temperature as set forth in the Technical Specifications.

• The temperature reported in this table are below the design temperatures specified in Table 2.2.3, Chapter 2.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-52 Rev. 5

I IOLTEC PROPRIETARY INFORMATION MPC LidNote I 236 (457)

Overpack Inner Shell 162 (324)

Overpack Outer Shell 76 (169)

Overpack Body ConcreteNotc 1 109 (228)

Overpack Lid ConcreteNorc 1 128 (262)

Area Averaged Air outlet 99 (210)

MPC Cavity Pressure, kPa (psig)

No Rod Rupture 665.9 (96.6)

Note I: Maximum section average temperature is reported.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-53 Rev. 5

I IOLTEC PROPRIETARY INFORMATION HEAT GENERATING ~

FUEL RODS ARRAY BASKET CELL WALL HOMOGENEOUS CROSS-SECTION WITH UNIFORM HEAT GENERATION HELIUM FILLING EMPTY SPACES (a) TYPICAL FUEL CELL

{b) SOLID REGION OF EFFECTIVE CONDUCTIVITY Figure 4.4.1: Homogenization of the Storage Cell Cross-Section HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-54 Rev. 5

MPC Shell Fuel Zone HOLTEC flROflRIETARY lt~FORMATION Overpack Outer Shell Concrete Overpack Inner Shell Figure 4.4.2: Planar View of HI-STORM FW MPC-89 Quarter Symmetric 3-D Model HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-55 Rev. 5

HO! IEC PROPRIETARY INFORMATION Air In-Flow __ _f::::t::::~=~-

Overpack Outer Shell Channel MPC Shell Fuel Zone Overpack Inner Shell Figure 4.4.3: Planar View of HI-STORM FW MPC-37 Quarter Symmetric 3-D Model HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-56 Rev. 5

Rodded Region Modeled as Equivalent Porous Media HO! TEC PROPRleT,t\\RY INFORMATION Channel-to-Cell Helium Gap Basket Wall Fuel Channel Figure 4.4.4: Closeup View of the MPC-89 Channeled Fuel Spaces HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-57 Rev. 5

Legend:

Ps: Cask pitch A0 : Tributary area I IOLTEC PROPRIETARY INFORMATION Figure 4.4.5: Illustration of a Centrally Located Cask in a Cask Array HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-58 Rev. 5

I IOLTEC PROPRIETARY INFORMATION LEGEND: ~

IMPERVIOUS BOUNDARYI

' '~ "

......J '

I I

, /

v I l I I I I I I

,;).: :: : : ::~*

~:::*.:.' :: : *.:*:

AIR ACCESS PATH CANISTER/

OVERPACK ANNULUS I

,,,/

I I

/

/

L,..,

' r

~

I I

Figure 4.4.6: Illustration of the Hypothetical Square Cavity Thermal Model HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-59 Rev. 5

6.0 5.0 l i 4.0 ~

C ;

~

Q.

3.0 2.0 1.0 0.0 0.00 I IOLTEC PROPRIETARY INFORMATION 4

0.02 0.04 0.06 Superficial Velocity (mis) 0.08

-- MPC-32 MPC-37 Poly, (MPC3c')

Figure 4.4.7: Storage Cell Pressure Drop as a Function ofTn-Cell Helium Ve]ocity HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-60 Rev. 5

lelOb+EG PROPRIETARY INFORMATIOl<l 4.5 THERMAL EVALUATION OF SHORT-TERM OPERATIONS 4.5.1 Thermally Limiting Evolutions During Short-Term Operations Prior to placement in a HI-STORM FW overpack, an MPC must be loaded with fuel, outfitted with closures, dewatered, dried, backfilled with helium and transported to the HI-STORM FW module. In the unlikely event that the fuel needs to be returned to the spent fuel pool, these steps must be performed in reverse. Finally, if required, transfer of a loaded MPC between HI-STORM FW overpacks or between a HI-STAR transpo1t overpack and a HI-STORM FW storage overpack must be carried out in a safe manner. All of the above operations, henceforth referred to as "short-term operations", are short duration events that woul.d likely occur no more than once or twice for an individual MPC.

Chapter 9 provides a description of the typical loading steps involved in moving nuclear fuel from the spent fuel pool to dry storage in the HI-STORM FW system. The transition from a wet to a dry environment, to comply with ISG-11, Rev. 3, must occur without exceeding the short-term operation temperature limits (see Table 4.3.1 ).

The loading steps that present the limiting thermal condition during short tenn operations for the fuel are those when either one or both of the following conditions exist:

1.

The MPC's fuel storage space is evacuated of fluids resulting in a significant decrease in internal heat transmission rates. This condition obtains if the vacuum drying method for removing moisture from the canister is employed.

11.

The removal of heat from the external swfaces of the MPC is impeded because of the air gap between the canister and HI-TRAC VW. This condition exists, for example, when the loaded MPC is being moved inside HI-TRAC VW for staging and transfer of the MPC to the HI-STORM FW overpack.

In this section, the thermally limiting scenarios during short-term operations are identified and analyzed.

Onsite transport of the MPC has been analyzed with the HI-TRAC VW in the vertical orientation to ensure that the them1osiphon action within the MPC is preserved at all times. Onsite transport of the MPC in a non-vertical orientation HI-TRAC VW may occur provided that a site-specific analysis is perfonned to obtain the permissible duration of the non-vertical orientation.

Compliance with the therma] limits ofISG-11 [4.1.4] must be demonstrated as a part of the site-specific safety evaluation under 10CFR72.212.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-61 Rev. 5

I IOLTEC PROPRIETARY INFORMATION 4.5.2 HI-TRAC VW Thermal Model 4.5.2.1 On-Site Transfer The HI-TRAC VW transfer cask is used to load and unload the HI-STORM FW concrete storage overpack, including onsite transport of the MPCs from the loading facility to an ISFSI pad.

Within a loaded HI-TRAC VW, heat generated in the MPC is transported from the contained fuel assemblies to the MPC shell through the fuel basket and the basket-to-shell gaps via conduction and thermal radiation. From the outer surface of the MPC to the ambient atmosphere, heat is transported within across multiple concentric layers, representing the air gap, the HI-TRAC VW inner shell, the lead shielding, the HI-TRAC VW outer shell, the water jacket space and the jacket shell. From the surface of the HI-TRAC VW's enclosure shell heat is rejected to the atmosphere by natural convection and radiation.

A small diametral gap exists between the outer surface of the MPC and the inner surface of the HI-TRAC VW overpack which may be filled with water during an operational state to serve as a heat sink and radiation absorber. The water jacket, which provides neutron shielding for the HI-TRAC VW overpack, surrounds the outer cylindrical steel wall of the HI-TRAC VW body. Heat is transported through the water jacket by a combination of conduction through steel ribs and convection heat transfer in the water spaces. The bottom face of the HI-TRAC VW is in contact with a supporting surface which is a thermal heat sink. This face is conservatively modeled as an insulated surface. The HI-'fRAC VW is an open top construction which is modeled as an opening to allow air exchange with the ambient.

The HI-TRAC VW Transfer Cask them1al analysis is based on a detailed heat transfer model that conservatively accounts for all modes of heat transfer in the MPC and HI-TRAC VW. The thermal model incorporates several conservative features listed below:

1.

Severe levels of environmental factors - bounding ambient temperature, 32.2°C (90°F),

and constant solar flux - were coincidentally imposed on the thermal design. A bounding solar absorbtivity of 0.85 is applied to all exposed surfaces.

11.

The HI-TRAC VW Transfer Cask-to-MPC annular gap is analyzed based on the nominal design dimensions. No credit is considered for the gap reduction that would occur as a result of differential thermal expansion with design basis fuel at hot conditions. The MPC is considered to be concentrically aligned with the cask cavity and the annulus is filled with air. This scenario maximizes thermal resistance.

III.

The HI-TRAC VW baseplate is in thermally communicative contact with supporting surfaces. For conservatism an insulated boundary condition is applied to the baseplate.

1v.

The HI-TRAC VW fluid columns (namely air in the annulus and water in the water jacket) are allowed to move. In other words natural convection heat transfer by annulus air and water is credited in the analysis.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-62 Rev. 5

HOLfEC PROPRIETARY l~IFORMATION

v.

To maxurnze lateral resistance to heat dissipation in the fuel basket conservatively postulated 0.8 mm full length panel gaps are assumed at all intersections. This approach is similar to the approach in the approved HI-STAR 180 Package in Docket 71-9325. The shims installed in the MPC peripheral spaces (See MPC-37 and MPC-89 drawings in Section 1.5) are explicitly modeled. For conservatism reasonably bounding gaps (2.5 mm basket-to-shims and 2.5 mm shims-to-shell) are incorporated in the thennal models.

v1.

The Raleigh number of air flow in the annulus between the MPC and HI-TRAC VW indicates that the flow regime in this region is laminar. Therefore, the air flow in this region is modeled as laminar in the thermal model.

The grid deployed in the HI-TRAC VW thermal model is confomed to be grid independent through mesh sensitivity studies. The studies refined the radial mesh in HI-TRAC VW annulus and water jacket regions. The thermal solutions obtained show that the temperatures are essentially tmchanged.

To evaluate on-site transfer operations in a conservative manner a HI-TRAC VW thermal model is constructed under the limiting scenario of fuel storage in the minimum height MPC-37 (See Section 4.4.1.5) and limiting Pattern A heat load specified in Chapter 1, Section 1.2 (See Section 4.4.4). The model adopts the MPC thermal modeling methodology described in Section 4.4 and the properties of design basis I 4x 14 Ft. Calhoun fuel defined in Table 4.4.1 under the limiting fuel storage scenario cited above. Results of on-site transfer analyses are provided in Subsection 4.5.4.3.

4.5.2.2 Grid Sensitivity Studies Cognizant to the grid sensitivity studies performed for the HI-STORM FW System discussed in Section 4.4, a similar study is performed for the HI-TRAC VW System. This study is also performed in accordance with the ASME V&V method [4.4.3]. The grid sensitivity study is performed for the limiting thermal scenario i.e. MPC-37 with minimum fuel length and loaded with pattern A. All the three meshes used for this study satisfy the recommended criterion of 1.3 as the grid refinement factor [ 4.4.3]. The predicted PCT from these three meshes is essentially the same and are reported in the table below:

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HO! IEC PROPRIETARY INFORMATION Total Mesh Permissible Clad Mesh No Size PCT (°C)

Limit (°C)

Temperature Margin (°C) 1 (Licensing 1,267,474 389 400 11 Basis Mesh) 2 2,678,012 390 400 10 3

5,797,030 389 400 11 The solutions from these grids are in the asymptotic range. The finest mesh (Mesh 3) has about 4.6 times the total mesh size of the licensing basis mesh (Mesh 1). Even with such a large mesh refinement, the PCT is essentially same for all the three meshes. Since the difference of PCT for all these meshes is close to zero, it indicates that an oscillatory convergence or that the "exact" solution has been attained [4.5. 1]. To provide further assurance of convergence, grid convergence index (GCI), which is a measure of the solution uncertainty, is computed as 0.566%. The apparent order of the method is calculated as 1.2.

Based on the above results, it can be concluded that the Mesh 1 is reasonably converged and is adopted as the licensing basis converged mesh.

4.5.2.3 Vacuum Drying The initial loading of SNF in the MPC requires that the water within the MPC be drained and replaced with helium. For MPCs containing moderate bumup fuel assemblies only, this operation may be carried out using the conventional vacuum drying approach upto design basis heat load.

In this method, removal of moisture from the MPC cavity is accomplished by evacuating the MPC after completion of MPC draining operation. Vacuum drying of MPCs containing high burnup fuel assemblies is permitted up to threshold heat loads defined in Table 4.5.1. High burnup fuel drying in MPCs generating greater than threshold heat load is performed by a forced flow helium drying process as discussed in Section 4.5.4.

Prior to the start of the MPC draining operation, both the HI-TRAC VW annulus and the MPC are full of water. The presence of water in the MPC ensures that the fuel cladding temperatures are lower than design basis limits by large margins. As the heat generating active fuel length is uncovered during the draining operation, the fuel and basket mass will undergo a gradual heat up from the initially cold conditions when the heated surfaces were submerged under water. To minimize fuel temperatures during vacuum drying operations the HI-TRAC VW annulus must be water filled. The necessary operational steps required to ensure this requirement are set fo1t h in Chapter 9.

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HO! rec PROPRleT,t\\RY INFORMATION A 3-D FLUENT thermal model of the MPC is constructed in the same manner as described in Section 4.4*. The principal input to this model is the effective conductivity of fuel under vacuum drying operations. To bound the vacuum drying operations the effective conductivity of fuel is computed assuming the MPC is filled with water vapor at a very low pressure (1 torr). The methodology for computing the effective conductivity is given in Section 4.4.1 and effective prope1ties of design basis fuel under vacuum conditions tabulated in Table 4.5.8. To ensure a conservative evaluation the thermal model is incorporated with the following assumptions:

1.

Bounding steady-state condition is reached with the MPC decay heat load set equal to the limiting heat load (Pattern A in Table 1.2.3 and 1.2.4) for MPCs fueled with Moderate Burnup Fuel and threshold heat load defined in Table 4.5.1 for MPCs fueled with one or more High Burnup fuel assemblies.

ii.

The external surface of the MPC shell is postulated to be at the boiling temperature of water 100°C (212°F).

111.

The bottom surface of the MPC is insulated.

1v.

MPC internal convection heat transfer is suppressed.

Results of vacuum condition analyses are provided in Subsection 4.5.4.1.

4.5.3 Maximum Time Limit During Wet Transfer Operations In accordance with NUREG-1536, water inside the MPC cavity during wet transfer operations is not permitted to boil. This requirement is met by imposing time limits for fuel to remain submerged in water after a loaded HI-TRAC VW cask is removed from the pool.

Fuel loading operations are typically conducted with the HI-TRAC VW and its contents (water filled MPC) submerged in pool water. Under these conditions, the HI-TRAC VW is essentially at the pool water temperature. When the HI-TRAC VW transfer cask and the loaded MPC under water-flooded conditions is removed from the pool, the water, fuel, MPC and HI-TRAC VW metal absorb the decay heat emitted by the fuel assemblies. This results in a slow temperature rise of the HI-TRAC VW with time, starting from an initial (pool water) temperature. The rate of temperature rise is limited by the thermal inertia of the HI-TRAC VW system. Environmental factors may be used to influence the rate of temperature change of the HI-TRAC VW system (e.g. wetting of the external surface of the HI-TRAC VW).

Two approaches of estimating the maximum permissible time for fuel to be submerged in water (i.e. time-to-boil) are presented in the following sections. Either approach may be selected without restriction. The first approach is developed as a bounding way of determining the time-to-boil and is best suited for low heat load canisters. The second approach is developed as a more

• The MPC thermal model adopted for vacuum drying analysis in this sub-section includes the gap between the intersecting basket panels as 0.4 mm. A sensitivity study of the most limiting thermal scenario (least margins to fuel temperature limit) of vacuum drying condition is performed with this gap as 0.8 mm and discussed in Sub-section 4.5.4.4.

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lelObTi;C PROPRIETARY INFORMATION realistically conservative approach and is best suited for higher heat load canisters, which require more extensive ALARA considerations.

Regardless of the approach used to estimate time-to-boil, defense-in-depth measures (such as measurement of the pool water or cask surface temperature) shall be employed to preclude boiling of the canister water at any point in time during short term operations.

4.5.3.1 Approach One, Bounding Time Limit To enable a bounding heat-up rate determination, the following conservative assumptions are utilized:

1.

Heat loss by natural convection and radiation from the exposed HI-TRAC VW surfaces to ambient air is neglected (i.e., an adiabatic heat-up calculation is performed).

11.

Design maximum heat input from the loaded fuel assemblies is assumed!.

111.

The shortest allowable HI-TRAC VW is credited in the analysis to impa1t the lowest thermal inertia on the system, which will result in the highest rate of temperature rise.

1v.

The water mass is in the MPC cavity is understated.

Table 4.5.3 summarizes the weights and thermal inertias of several components in the loaded HI-TRAC VW transfer cask that corresponds to the sho1test allowable fuel assembly*. The rate of temperature rise of the HI-TRAC VW transfer cask and contents during an adiabatic heat-up is governed by the following equation:

dT _ Q where:

Q =

conservatively bounding heat load (Btu/hr)

Ch =

thermal inertia of a loaded HI-TRAC VW (Btu/°F)

T =

temperature of the HI-TRAC VW transfer cask (°F) t =

time (hr) t

• In accordance with FSAR Paragraph 4.4. I. I, the shortest allowable fuel assembly considers all fuel assembly arrays except l Sx 151.

t Time clock begins when the lid is placed on the MPC or immediately following the measurement of the temperature of water in the MPC cavity.

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HOLTEC F'RO~RIETARY INFORMATION From this adiabatic rate of temperature rise estimate, the maximum allowable time duration (tmax) for fuel to be submerged in water is determined as follows:

T boil - Tini1ial tmax = (dT/dt) where:

Tboil =

boiling temperature of water (equal to 212°F at the water surface in the MPC cavity)

Tinitial = initial temperature of water in the MPC (°F)

The time-to-boil clock starts when the lid is placed on the MPC and the HI-TRAC is in the spent fuel pool and ends when the MPC is drained (See section 9.2.4). Following placement of the lid on the MPC, the initial temperature of water in the MPC shall be taken as the pool water temperature. Table 4.5.4 provides a summary of tmax at several representative initial temperatures. The example time-to-boil calculations shown in Table 4.5.4 are conservatively performed for the HI-TRAC VW that cotTesponds to shortest allowed fuel assembly since lowerbound thennal inertia results in lower time limits. A site-specific time-to-boil calculation can be performed using the above equations based on the actual canister heat load and thermal inertia of the specific HI-TRAC VW System. Environmental factors may be used to influence the rate of temperature rise of the HI-TRAC VW System ( e.g. wetting of the external surface of the HI-TRAC VW).

Measurement of the temperature of water in the MPC may be taken at any point following the removal of the MPC from the pool. The measured MPC water temperature may be used as the initial temperature (Tinitial) to re-evaluate the maximmn allowable time dlU"ation for fuel to be submerged in water (tmax)- The re-calculated maximum allowable time may be used as an updated time-to-boil clock.

4.5.3.2 Approach Two, Conservatively Realistic Time Limit At low heat loads, the adiabatic heat up formula is adequate to support an ALARA loading operation. However, the rate of MPC heat-up is heavily influenced by the environment around the cask, which the adiabatic condition assumption completely ignores. At higher heat loads the adiabatic heat up fo1mula yields increasingly more restrictive time-to-boil values, resulting in an adverse impact on the accumulated dose due to the operator actions required for implementing alternate cooling. ALARA considerations warrant a more realistically conservative estimate of the time-to-boil for loading scenarios where the adiabatic formula would lead to an overly conservative estimate. Accordingly, to minimize dose, the loading procedure should be appropriately info1med by a more realistic heat balance calculation for the specific conditions applicable to plant and the specific short term operation. The thermal-hydraulic model of the cask and the canister, presented in Section 4.5, may be used to obtain a refined estimate of the time-to-boil for each canister being loaded. This more realistic heat balance equation is developed and discussed by Holtec Position Paper DS-412 [ 4.5.2].

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I IOLTEC PROPRIETARY INFORMATIOl<l The time-to-boil clock starts when the lid is placed on the MPC and the HI-TRAC is in the spent fuel pool and ends when the MPC is drained. Following placement of the lid on the MPC, the initial temperature of water in the MPC shall be taken as the pool water temperature.

As in Approach One, measurement of the temperature of water in the MPC may be taken at any point following the remova] of the MPC from the pool for this approach as well. Using the maximum allowable time duration (tmax) formula outlined in Paragraph 4.5.3.1, the measured MPC water temperature may be used as the initial temperature (Tinitia1) to conservatively reevaluate the maximum allowable time duration for fuel to be submerged in water (tmax), The recalculated maximum allowable time may be used as an updated time-to-boil clock.

4.5.3.3 Forced Water Circulation As set forth in the HI-STORM FW operating procedures, in the unlikely event that the calculated maximum allowable time is found to be insufficient to complete all wet transfer operations, a forced water circulation shall be initiated and maintained to remove the decay beat from the MPC cavity. In this case, re latively cooler water will enter via MPC lid ports and heated water will exit from the vent port. At the conclusion of forced water circulation, the measured temperature of water in the MPC shall be used to re-calculate the maximum allowable time duration for fuel to be submerged in water (tmax) and update the time-to-boil clock.

The minimum water flow rate required to maintain the MPC cavity water temperature below boiling with an adequate subcooling margin is determinedl as follows:

where:

M =

Q w

Cpw (Tmax - T;,,)

Mw = minimum water flow rate (lb/hr)

Cpw = water heat capacity (Btu/lb-°F)

Tmax = suitably limiting temperature below boiling (°F)

Tin = water supply temperature to MPC 4.5.4 Analysis of Limiting Thermal States During Short-Term Operations 4.5.4.1 Vacuum Drying The vacuum drying option is evaluated for the two limiting scenarios defined in Section 4.5.2.2 to address Moderate Burnup Fuel under limiting heat load (Pattern A) and High Burnup Fuel under threshold heat load defined in Table 4.5.1. The principle objective of the analysis is to ensure compliance with ISG-1 1 temperature limits. For this purpose 3-D FLUENT thermal models of the MPC-37 and MPC-89 canisters are constructed as described in Section 4.5.2.2 and bounding steady state temperatures computed. The results are tabulated in Tables 4.5.6 and 4.5.7.

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I IOLTEC PROPRIETARY INFORMATIOl<l The results show that the cladding temperatures comply with the ISG-11 limits for moderate and high burnup fuel in Table 4.3.l by robust margins.

4.5.4.2 Forced Helium Dehydration To reduce moisture to trace levels in the MPC using a Forced Helium Dehydration (FHD) system, a conventional, closed loop dehumidification system consisting of a condenser, a demoisturizer, a compressor, and a pre-heater is utilized to extract moisture from the MPC cavity through repeated displacement of its contained helium, accompanied by vigorous flow turbulation. Demoisturization to the 3 torr vapor pressure criteria required by NUREG 1536 is assured by verifying that the helium temperature exiting the demoisturizer is maintained at or below the psychrometric threshold of 21 °F for a minimum of 30 minutes. Appendix 2.B of

[ 4.1.8] provides a detailed discussion of the design criteria and operation of the FHD system.

The FHD system provides concurrent fuel cooling during the moisture removal process through forced convective heat transfer. The attendant forced convection-aided heat transfer occurring during operation of the FHD system ensures that the fuel cladding temperature will remain below the applicable peak cladding temperature limit in Table 2.2.3. Because the FHD operation induces a state of forced convection heat transfer in the MPC, (in contrast to the quiescent mode of natural convection in long te1m storage), it is readily concluded that the peak fuel cladding temperature under the latter condition will be greater than that during the FHD operation phase.

In the event that the FHD system malfunctions, the forced convection state will degenerate to natural convection, which corresponds to the conditions of normal onsite transfer. As a result, if the FHD machine fails then the peak fuel cladding temperatures will approximate the value reached during normal onsite transfer, discussed below.

4.5.4.3 Normal On-site Transfer An MPC-37 situated inside a HI-TRAC VW is evaluated under the design heat load defined in Section 1.2. The MPC-37 is evaluated because it yields the highest fuel and cask temperatures (See Table 4.4.2). This scenario is analyzed using the same 30 FLUENT model of the MPC-37 articulated in Section 4.4 for normal storage with due recognition of it situated in the HI-TRAC VW transfer cask. The HI-TRAC VW model discussed in Section 4.5.2 is adopted to construct a global model of an MPC-37 situated inside the HI-TRAC VW and dissipating heat by natural convection and radiation to ambient air.

While the duration of onsite transport is generally short to preclude the MPC and HI-TRAC VW from reaching a steady-state, a conservative approach is adopted herein by assuming steady state maximum temperatures are reached. The principle objectives of the HI-TRAC VW analyses are to demonstrate:

i)

Cladding integrity ii)

Confinement integrity iii)

Neutron shield integrity HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-69 Rev. 5

lelOLTEC PROPRIETARY l~FORMA I ION The appropriate criteria are provided in Tables 2.2.1 (pressure limits) and 2.2.3 (temperature limits).

The results of thermal analyses tabulated in Table 4.5.2 show that the cladding temperatures are below the ISG-11 temperature limits of High and Moderate Burnup Fuel (Table 4.3.1). Actual margins during HI-TRAC VW operations will be much larger due to the many conservative assumptions incorporated in the analysis.

The water in the water jacket surrounding the HI-TRAC VW body provides necessary neutron shielding. During normal handling and onsite transfer operations this shielding water is contained within the water jacket at elevated internal pressure. The water jacket is equipped with two pressure relief devices set to an adequately high pressure to prevent boiling. Under HI-TRAC VW operations, the bulk temperature of water remains below the temperature limit specified in Table 2.2.3. Accordingly, water is in the liquid state and the neutron shielding function is maintained. The cladding, neutron shield and HI-TRAC VW component temperatures are provided in Table 4.5.2. The confinement boundary integrity is evaluated in the Section 4.5.6.

4.5.4.4 Effect oflncrease in Basket Panel Gap As described in Subsection 4.5.2.3, a sensitivity study is performed for the vacuum drying condition of high burnup fuel at threshold heat load with the basket panel notch gap equal to 0.8 mm. The results of the steady state analysis vacuum drying condition are summarized in Table 4.5.10. The PCT and cask component temperatures during vacuum drying are below their respective temperature limits. Therefore, the effect of increasing the panel gap is small and leaves sufficient safety margins during vacuum drying conditions.

4.5.4.5 Evaluation of 15x151 Short Fuel Assembly (a) On-Site Transfer The thermal evaluations described in this sub-section are performed for the 15x 151 short fuel height of the HI-TRAC VW, similar to the evaluations performed for HI-STORM FW System in Sub-Section 4.4.1.7. The thermal model is exactly the same as that described in sub-section 4.5.2 with the following exceptions:

1. The fuel basket height is conservatively modeled lower i.e. equal to 149".

2. The flow resistance through the fuel assemblies is based on the calculations in sub-section 4.4.1.7.

3. The effective fuel thennal properties specific to 15x l51 fuel assembly are used (see Table 4.4.1)

The converged mesh from Sub-section 4.5.2.2 is utilized to evaluate the normal on-site transfer of 15x151 short MPC-37 with bounding heat load pattern A in HI-TRAC VW. The results from HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-70 Rev. 5

I IOLTEC PROPRIETARY INFORMATION the steady state analysis are tabulated in Table 4.5.11. The fuel temperatures are bounded by the licensing basis results reported in Table 4.5.2 for the minimum MPC-37 (short). The temperatures of other cask components are similar to the licensing basis evaluation. Therefore, the minimum MPC-37 (short) is adopted for all the licensing evaluations.

(b) Vacuum Drying The surface area of the MPC for heat transfer reduces for a shorter MPC height. Therefore, the 15x 151 short fuel assembly under the "minimum" category defined in Table 2.1.1 warrants a thermal analysis to show compliance with regulatory limits. A steady state vacuum drying thermal evaluation is performed at threshold heat load for the l 5x 151 sho1t MPC based on the same methodology described in Sub-section 4.5.2.3. The results of this analysis are reported in Table 4.5.12. The results show that the cladding temperatures comply with the ISG-11 limits for moderate and high burnup fuel in Table 4.3.1 by robust margins.

4.5.4.6 Thermal Evaluation of Various Extruded Basket Shim Design Options To allow flexibility in fabrication, the licensing drawings provide various options to install extruded basket shims between the basket and inside of the MPC wall. A summary of various allowable options is provided in Table l.2.9. From a thermal standpoint, emissivity of shims and the average total gap between the basket and extruded shim and the extruded shim and MPC shell are critical to heat transfer from the fuel basket to MPC. As noted in Table 1.2.9, solid shim aluminum plates may be placed between the basket and extruded shim to ensure the criteria on the gap in the basket periphery is met.

A series of thermal analyses to address all the allowable design options presented in Table 1.2.9 are performed and discussed below:

(a)

On-Site Transfer All the design options presented in Table 1.2.9 are evaluated below:

i)

Option I: This option corresponds to the licensing basis analysis presented in Sub-section 4.5.4.3. The predicted temperature and MPC cavity pressure using this option are reported in Tables 4.5.2 and 4.5.5 respectively. All the licensing basis thermal evaluations for HI-TRAC documented in this chapter are performed based on Option I in Table 1.2.9 since it results in the most limiting PCT and MPC pressure.

ii)

Option 2: The basket extruded shims are fabricated to provide a loose fit in the basket peripheral space. If the average radial total cold gap in the basket periphery exceeds the gap in Option 1 (Table 1.2.9), solid aluminum shim plates are placed in the space between the basket and extruded shims. The average radial total cold gap after the placement of solid shim plates must be restricted to that provided for Option 2 in Table 1.2.9. The gap between the basket and extruded shims with a solid shim plate is modeled as resistance element with an effective thermal HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-71 Rev. 5

I IOLTEC PROPRIETARY INFORMATION conductivity. A two-dimensional evaluation is performed to determine this effective thermal conductivity and documented in the calculation package [ 4.1.9].

The calculated effective thermal conductivity in the basket periphery region from the two-dimensional model is used as an input to the licensing basis three-dimensional thermal model described above. All other input parameters remain unchanged. The predicted PCT for this option under normal onsite transfer in HJ-TRAC is tabulated in Table 4.5.13.

iii) Option 3: The effective thermal conductivity in the space between the basket and extruded shims is bounded by that corresponding to Option 4 [4.1.9]. This design option is bounded by Option 4.

iv) Option 4: As discussed earlier, emissivity of extruded shims have an impact on the radiation heat transfer within the MPC and therefore must be evaluated. This option corresponds to low emissive extruded shims. If the average radial total cold gap in the basket periphery exceeds the gap in Option 3 (Table 1.2.9), solid aluminum shim plates are placed in the space between the basket and extruded shims. The average radial total cold gap after the placement of solid shim plates must be restricted to that provided for Option 4 in Table 1.2.9. The gap between the basket and extruded shims with a solid shim plate is modeled as resistance element with an effective thermal conductivity. A two-dimensional evaluation is performed to determine this effective thermal conductivity and documented in the calculation package [4.1.9).

The calculated effective thermal conductivity in the basket periphery region from the two-dimensional model is used as an input to the licensing basis three-dimensional thermal model described above. All other input parameters remain unchanged. The predicted PCT for this option under normal onsite transfer in HI-TRAC is tabulated in Table 4.5.13.

v)

Option 5: The effective thermal conductivity in the space between the basket and extruded shims is bounded by that corresponding to Option 6 [ 4.1.9]. This design option is bounded by Option 6.

vi) Option 6: As discussed earlier, emissivity of extruded shims have an impact on the radiation heat transfer within the MPC and therefore must be evaluated. If the average radial total cold gap in the basket periphery exceeds the gap in Option 5 (Table 1.2.9), solid aluminum shim plates are placed in the space between the basket and extruded shims. The average radial total cold gap after the placement of solid shim plates must be restricted to that provided for Option 6 in Table 1.2.9.

The gap between the basket and extruded shims with a solid shim plate is modeled as resistance element with an effective thermal conductivity. A two-dimensional evaluation is performed to determine this effective thermal conductivity and HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-72 Rev. 5

I IOLTEC PROPRIETARY INFORMATION I documented in the calculation package [4.1.9].

The calculated effective thermal conductivity in the basket periphery region from the two-dimensional model is used as an input to the licensing basis three-dimensional thermal model described above. All other input parameters remain unchanged. The predicted PCT for this option under normal onsite transfer in HI-TRAC is tabulated in Table 4.5.13.

The PCTs from the above sensitivity studies tabulated in Table 4.5.13 demonstrate that Option l is thermally the most limiting design option. Therefore, it is adopted for all the normal, off-normal and accident condition thermal evaluations. Since MPC-37 is the limiting them1al basket, these design options can be extended to MPC-89 fuel basket.

(b) Vacuum Drying A series of the11nal analyses to address all the allowable design options presented in Table 1.2.9 are also perfonned for the most limiting vacuum drying scenario i.e. under threshold heat load. These thermal evaluations are similar to those performed for normal on-site transfer and discussed above.

The PCTs from the sensitivity studies tabulated in Table 4.5.14 demonstrate that Option 1 is thermally the most limiting design option under vacuum drying condition.

4.5.4.7 Sensitivity Study of Basket Extruded Shim Thickness All the licensing basis thermal evaluations in this chapter are performed with an inch thick extruded basket shims. A sensitivity study is performed to evaluate the effect of reducing the thickness of basket shims on the fuel, MPC and HI-TRAC component temperature field during normal onsite transfer. The converged mesh from Sub-section 4.5.2.2 is adopted for this study.

The thermal model is exactly the same as that discussed in Sub-section 4.5.2 except that the thickness of extruded shims is reduced to 0.5 inches. The results of the sensitivity study are documented in Table 4.5.15. The results demonstrate that the effect of reducing the thickness of extiuded shims is small and leaves sufficient margins to temperature limits.

4.5.4.8 Normal On-site Transfer inside a Building Normal on-site transfer using the HI-TRAC VW can be carried out inside a building. When HI-TRAC VW is located inside a building, the ambient air temperature inside the building could be higher than the outdoor environment temperature used in the thermal evaluations performed in Subsection 4.5.4.3. To evaluate this scenario, an ambient temperature that corresponds to the maximum indoor air temperature specified in Table 2.2.2 for short te1m operations is assumed.

Since the cask is inside a building, no solar insolation is applied to the cask. A steady state analysis is performed for the limiting thermal scenario of MPC-37 inside the HI-TRAC VW HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-73 Rev. 5

I IOLTEC PROPRIETARY INFORMATION under heat load pattern A. The peak cladding, MPC and the HI-TRAC component temperatures are presented in Table 4.5.9 in addition to the MPC cask cavity pressure. The predicted component temperatures and MPC cavity pressure are below their respective temperatures and pressure for outdoor environment presented in Tables 4.5.2 and 4.5.5 respectively. Therefore, the no1mal on-site transfer of a HI-TRAC outside the building and with solar insolation as evaluated in Subsection 4.5.4.3 is the limiting thermal condition.

4.5.5 Cask Cooldown and Retlood Analysis During Fuel Unloading Operation NUREG-1536 requires an evaluation of cask cooldown and reflood procedures to support fuel unloading from a dry condition. Past industry experience generally supports cooldown of cask internals and fuel from hot storage conditions by direct water quenching. Direct MPC cooldown is effectuated by introducing water through the lid drain line. From the drain line, water enters the MPC cavity near the MPC baseplate. Steam produced during the direct quenching process will be vented from the MPC cavity through the lid vent port. To maximize venting capacity, both vent port RVOA connections must remain open for the duration of the fuel unloading operations. As direct water quenching of hot fuel results in steam generation, it is necessary to limit the rate of water addition to avoid MPC overpressurization. For example, steam flow calculations using bounding assumptions (100% steam production and MPC at design pressure) show that the MPC is adequately protected under a reflood rate of 3715 lb/hr. Limiting the water reflood rate to this amount or less would prevent exceeding the MPC design pressure.

4.5.6 Maximum Internal Pressure (Load Case NB in Table 2.2.7)

After fuel loading and vacuum drying, but prior to installing the MPC closure ring, the MPC is initially fi lled with helium. D uring handling and on-site transfer operations in the HI-TRAC VW transfer cask, the gas temperature will correspond to the thermal conditions within the MPC analyzed in Section 4.5.4.3. Based on this analysis the MPC internal pressure is computed under the assumption of maximum helium backfill specified in Table 4.4.8 and confirmed to comply with the short term operations pressure limit in Table 2.2.1. The results are tabulated in Table 4.5.5.

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HOLTEC PROPRIETARY INFORMATIOl<l TABLE4.5.l THRESHOLD HEAT LOADS UNDER VACUUM DRYING OF HIGH BURNUP FUEL (See Figures 1.2.1 and 1.2.2)

MPC-37 Number of Regions:

3 Number of Storage Cells:

37 Maximum Heat Load:

34.36 Region No.

Decay Heat Limit per Number of Cells Decay Heat Limit per Cell, kW per Region Region, kW 1

0.80 9

7.2 2

0.97 12 11.64 3

0.97 16 15.52 MPC-89 Number of Regions:

3 Number of Storage Cells:

89 Maximum Heat Load:

34.75 Region No.

Decay Heat Limit per Number of Cells Decay Heat Limit per Cell, kW per Recion Region, kW 1

0.35 9

3.15 2

0.35 40 14.00 3

0.44 40 17.60 Notes:

( 1) The maximum per storage cell heat load and total threshold heat load documented herein are used to perform thermal evaluations documented in subsection 4.5.4.1.

(2) The maximum per storage cell heat load and total threshold heat load allowed for an MPC-37 per the CoC are 0.8 kW and 29.6 kW respectively. Similarly, these values for an MPC-89 per the CoC are 0.337 kW and 30 kW respectively. No additional the1mal analysis is performed for these lower allowable CoC heat loads since they are bounded by the heat loads used in the vacuum drying thermal calculations (subsection 4.5.4.1).

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I IOLTEC PROPRIETARY INFORMATION Table 4.5.2 HI-TRAC VW TRANSFER CASK STEADY ST A TE MAXIMUM TEMPERA TURES Component Temperature, °C (°F)

Fuel Cladding 389 (732)

MPC Basket 374 (705)

Basket Periphery 299 (570)

Aluminum Basket Shims 272 (522)

MPC Shell 247 (477)

MPC LidNotc 1 240 (464)

HI-TRAC VW Inner Shell 138 (280)

HI-TRAC VW Radial Lead Gamma Shield 138 (280)

Water Jacket Bulk Water 129 (264)

Note 1: Maximum section average temperature is reported.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-76 Rev. 5

I IOLTEC PROPRIETARY INFORMATION Table 4.5.3 HI-TRAC VW TRANSFER CASK LOWERBOUND WEIGHTS AND THERMAL INERTIAS Note 1 Component Weight Heat Capacity Thermal Inertia (lbs)

(B tu/lb-°F)

(Btu/°F)

Lead 45627 0.031 1414 Carbon Steel 43270 0.1 4327 Stainless Steel 19561 0.12 2347 Aluminum 6734 0.207 1394 Metamic-HT 7349 0.22 1617 Fuel 46250 0.056 2590 MPC Cavity Water 6611 0.999 6604 Total 175402 20294 Note 1: Values presented in this table are based on the short HI-TRAC VW height determined in accordance with Table 3.2.1 using a PWR fuel height of l 57.

Table 4.5.4 MAXIMUM ALLOW ABLE TIME FOR WET TRANSFER OPERA TIONSNote I Initial temperature Time Duration OF (hr) 100 14.2 110 12.9 120 11.6 130 10.4 140 9.1 150 7.8 Note l: The time-to-boil limits provided herein are based on the HI-TRAC VW for a PWR fuel height of 157" and maximum design basis heat load. A site-specific calculation based on the methodology described in Section 4.5.3 can be performed to determine the time-to-boil limits.

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I IOLTEG PROPRle+,ARY lf)IFORMAJIQN Table 4.5.5 MPC CONFINEMENT BOUNDARY PRESSURE UNDER ON-SITE TRANSPORT Condition Pressure (psi~)

Initial backfill pressure (at 70°F) 45.5 (Tech. Spec. maximum in Table 4.4.8)

Maximum pressure 100.7 Table 4.5.6 MAXIMUM TEMPERATURES OF MPC-37 DURING VACUUM DRYING CONDITIONS Temperatures @DB Heat LoadNotc I Temperatures @ Threshold Heat Load Note 2 Component oc (OF) oc (OF)

Fuel Cladding 480 (896) 384 (723)

MPCBasket 464 (867) 367 (693)

Basket Periphery 357 (675) 288 (550)

Aluminum Basket Shims 278 (532) 232 (450)

MPC Shell 156 (313) 142 (288)

MPC LidNotc 3 107 (225) 100 (212)

Note 1: Addresses vacuum drying of Moderate Burnup Fuel w1der limiting heat load (Pattern A) defined in Section 1.2.

Note 2: Addresses vacuum drying of High Burnup Fuel under threshold heat load (Table 4.5.1).

Note 3: Maximum section temperature repo1ted.

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I IOLTEC PROPRIETARY INFORMATION Table 4.5.7 MAXIMUM TEMPERA TURES OF MPC-89 DURING VACUUM DRYING CONDITIONS Temperatures @DB Heat Temperatures @ Threshold Component LoadNote I Heat LoadNotel oc (OF) oc (OF)

Fuel Cladding 464 (867) 376 (709)

MPC Basket 449 (840) 359 (678)

Basket Periphery 348 (658) 286 (547)

Aluminum Basket Shims 275 (527) 232 (450)

MPC Shell 158(3 16) 144(291)

MPC LidN01c 3 127 (261) 110 (230)

Note 1: Addresses vacuum drying of Moderate Burnup Fuel under Design Basis heat load defined in Section 1.2.

Note 2: Addresses vacuum drying of High Burnup Fuel under threshold heat load (Table 4.5.1).

Note 3: Maximum section temperature reported.

Table 4.5.8 EFFECTIVE CONDUCTIVITY OF DESIGN BASIS FUELNote 1 UNDER VACUUM DRYING OPERATIONS (Btu/hr-ft-°F)

Temperature (°F)

Planar Axial 200 0.111 0.737 450 0.273 0.805 700 0.538 0.900 1000 0.977 1.040 Note 1: Ft. Calhoun 14x 14 fuel is defined as the design basis fuel under the limiting condition of fuel storage in the minimum height MPC-37 (See Table 4.4.2).

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lelObTi;C PROPRIETARY INFORMATION Table 4.5.9 STEADY STATE MAXIMUM TEMPERATURES AND MPC CAVITY PRESSURE FOR A HI-TRAC VW TRANSFER CASK INSIDE A BUILDING*

Component Temperature, °C (°F)

Fuel Cladding 387 (729)

MPC Basket 373 (703)

Basket Periphery 297 (567)

Aluminum Basket Shims 271 (520)

MPC Shell 246 (475)

MPC LidNotc 1 238 (460)

HI-TRAC VW Inner Shell 135 (275)

HI-TRAC VW Radial Lead Gamma Shield 134 (273)

Water Jacket Bulk Water 126 (259)

MPC Cavity Pressure, kPa (psig)

No Rod Rupture 691.4 (100.3)

Note 1: Maximum section average temperature is reported.

• This condition corresponds to a HI-TRAC inside a building at an ambient temperature specified in Table 2.2.2 and without solar insolation.

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I IOLTEC PROPRIETARY INFORMATION Table 4.5.10 EFFECT OF INCREASE IN BASKET PANEL GAP ON MAXIMUM TEMPERA TURES OF MPC-37 DURING VACUUM DRYING CONDITION AT THRESHOLD HEAT LOAD Component TemperaturesNote 1, °C (°F)

Fuel Cladding 389 (732)

MPC Basket 373 (703)

Basket Periphery 292 (558)

Aluminum Basket Shims 234 (453)

MPC Shell 142 (288)

Note l : The predicted temperatures for the increased panel gap are slightly higher than the licensing basis temperatures for threshold heat load repo1ted in Table 4.5.6.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-81 Rev. 5

I IOLTEC PROPRIETARY INFORMATION Table 4.5.11 HI-TRAC VW TRANSFER CASK STEADY STATE MAXIMUM TEMPERATURES AND MPC CAVITY PRESSURE FOR 15x151 SHORT FUEL ASSEMBLY Component Temperature, °C (°F)

Fuel Cladding 382 (720)

MPC Basket 366 (691)

Basket Periphery 301 (574)

Aluminum Basket Shims 290 (554)

MPC Shell 254 (489)

MPC LidNote 1 250 (482)

HI-TRAC VW Inner Shell 141 (286)

HI-TRAC VW Radial Lead Gamma Shield 140 (284)

Water Jacket Bulk Water 131 (268)

MPC Cavity Pressure (psig)

No Rod RuptureNote 2 100.3 Note 1: Maximum section average temperature is reported.

Note 2: The MPC cavity pressure is calculated based on the Tech. Spec. maximum value (see Table 4.4.8).

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HJ-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-82 Rev. 5

lelObTi;C PROPRIETARY INFORMATION Table 4.5.12 MAXIMUM TEMPERA TURES OF MPC-37 DURING VACUUM DRYING CONDITIONS AT THRESHOLD HEAT LOAD FOR l 5x15I SHORT FUEL ASSEMBLY Component Temperatures oc (OF)

Fuel Cladding 389 (732)

MPC Basket 369 (696)

Basket Periphery 280 (536)

Aluminum Basket Shims 235 (455)

MPC Shell 149 (300)

MPC LidNotc I 95 (203)

Note l : Maximum section temperature reported.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-83 Rev. 5

I IOLTEC PROPRIETARY l~JFORMATION TABLE4.5.13 PEAK CLADDING TEMPERATURES FOR EXTRUDED BASKET SHIM DESIGN OPTIONS UNDER NORMAL ONSITE TRANSFER USING HI-TRAC VW Design OptionNotc 1 PCT (°C)

Option 1 Note 2 389Notc 3 Option 2 386 Option 3 Note4 Option 4 381 Option 5 Note 5 Option 6 387 Notes:

(1) All the extruded basket shim design options are summarized in Table 1.2.9.

(2) Option 1 corresponds to the licensing basis evaluation documented in Table 4.5.2.

(3) Option I results in the highest peak cladding temperature and is therefore adopted as the licensing basis option for thermal evaluation of long-term storage in HI-STORM and under all off-normal and accident conditions.

(4) Option 3 is bounded by Option 4.

(5) Option 5 is bounded by Option 6.

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I IOLTEC PROPRIETARY INFORMATION TABLE4.5.14 PEAK CLADDING TEMPERATURES FOR EXTRUDED BASKET SHIM DESIGN OPTIONS UNDER VACCUM DRYING CONDITION AT THRESHOLD HEAT LOAD Design OptionNotc 1 PCT (

0C)

Option l Note 2 3g9Notc 3 Option 2 376 Option 3 Note4 Option 4 362 Option 5 Note 5 Option 6 376 Notes:

(1) All the extruded basket shim design options are summarized in Table 1.2.9.

(2) Option 1 corresponds to the licensing basis evaluation documented in Table 4.5. 10.

(3) Option l results in the highest peak cladding temperature and is therefore adopted as the licensing basis evaluation.

(4) Option 3 is bounded by Option 4.

(5) Option 5 is bounded by Option 6.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-85 Rev. 5

lelObTi;C PROPRIETARY INFORMATION Table 4.5.15 SENSITIVITY STUDY OF REDUCED BASKET SHIM THICKNESS ON HI-TRAC VW TRANSFER MAXIMUM TEMPERATURES DURING NORMAL ON-SITE TRANSFER Component Temperature, °C Note 2 Fuel Cladding 391 MPC Basket 376 Basket Periphery 304 Aluminum Basket Shims 277 MPC Shell 250 MPC LidNote I 240 HI-TRAC VW Inner Shell 138 HI-TRAC VW Radial Lead Gamma Shield 137 Water Jacket Bulk Water 129 Note 1: Maximum section average temperature is reported.

Note 2: The results are essentially the same as the licensing basis thermal evaluation presented in Table 4.5.2.

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lelObTi;C PROPRIETARY INFORMATION 4.6 OFF-NORMAL AND ACCIDENT EVENTS In this Section thermal evaluation of HI-STORM FW System under off-normal and accident conditions defined in Sections 4.6.1 and 4.6.2 is provided. To ensure a bounding evaluation the limiting Pattern A thermal loading scenario defined in Section 4.4.4 is adopted in the evaluation.

4.6.1 4.6.1.1 Off-Normal Events Off-Normal Pressure (Load Case NB in Table 2.2.7)

This event is defined as a combination of (a) maximum helium backfill pressure (Table 4.4.8),

(b) 10% fuel rods rupture, ( c) limiting fuel storage configuration and ( d) off-normal ambient temperature. The principal objective of the analysis is to demonstrate that the MPC off-normal design pressure (Table 2.2.1) is not exceeded. The MPC off-nom1al pressures are reported in Table 4.6. 7. The result is below the off-normal design pressure (Table 2.2.1 ).

4.6.1.2 Off-Normal Environmental Temperature This event is defined by a time averaged ambient temperature of 100°F for a 3-day period (Table 2.2.2). The results of this event (maximum temperatures and pressures) are provided in Table 4.6.1 and 4.6.7. The results are below the off-norn1al condition temperature and pressure limits (Tables 2.2.3 and 2.2.1).

4.6.1.3 Partial Blockage of Air Inlets/Outlets The HI-STORM FW system is designed with debris screens installed on the inlet and outlet openings. These screens ensure the air passages are protected from entry and blockage by foreign objects. As required by the design criteria presented in Chapter 2, it is postulated that the HI-STORM FW air inlet vents and/or outlet vents are 50% blocked. The resulting decrease in flow area increases the flow resistance of the inlet and outlet ducts, thereby decreasing the air mass flow ate into the system.

An explicit thermal evaluation to evaluate the effect of 50% blockage of air inlet vents is performed. The effect of the increased flow resistance on fuel and other component temperature is analyzed for the normal ambient temperature (Table 2.2.2) and a limiting fuel storage configuration. The computed temperatures are repo11ed in Table 4.6.1 and the corresponding MPC internal pressure in Table 4.6.7. The results are confirmed to be below the temperature limits (Table 2.2.3) and pressure limit (Table 2.2. 1) for off-normal conditions.

In an unlikely event of both inlet and outlet vents being 50% blocked, cold air still enters into the annulus space between the MPC and HI-STORM FW overpack and hot air exits from the partially unblocked outlet vents. The effect of partially blocked outlet vents is similar to the effect of partially blocked inlet vents. Since the effect of partially blocked inlet vents alone has a HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-87 Rev. 5

I IOLTEC PROPRIETARY INFORMATION smal 1 impact on the fuel (less than 15°C) and component temperatures compared to large temperature margins, the temperatures and MPC pressw-e due to combined effect of partially blocked inlet and outlet vents will still remain below the off-normal temperature and pressure limits.

4.6.1.4 FHD Malfunction This event is defined in Subsection 12.1.5 as stoppage of the FHD machine following loss of power or active component trip. The principal effect of this event is stoppage of helium circulation through the MPC and transitioning of heat dissipation in the MPC from forced convection to natural circulation cooling. To bound this event an array of adverse conditions are assumed to have developed coincidentally, as noted below:

a. Steady state maximum temperatures have been reached.

b. Design maximum heat load in the limiting MPC-37 is assumed.

c. Air (not water) is in the HI-TRAC FW annulus.

d. The helium pressure in the MPC is at the minimum possible value of 20 psig.

Under the FHD malfunction condition the principal requirement to ensure the off-normal cladding temperature limits mandated by ISG-11, Rev. 3 (see Table 2.2.3) must be demonstrated.

For this purpose an array of adverse conditions are defined above and the Peak Cladding Temperature (PCT) computed using the 30 FLUENT model of the transfer cask articulated in Section 4.5. The PCT computes as 433°C which is significantly below the 570°C off-normal temperature limit.

4.6.2 4.6.2.l Accident Events Fire Accident (Load Case AB in Table 2.2.13)

Although the probability of a fire accident affecting a HI-STORM FW system during storage operations is low due to the lack of combustible materials at an TSFST, a conservative fire event has been assumed and analyzed. The only credible concern is a fire from an on-site transport vehicle fuel tank. Under a postulated fuel tank fire, the outer layers of HI-TRAC VW or HI-STORM FW overpacks are heated for the duration of fire by the incident thermal radiation and forced convection heat fluxes. The amount of fuel in the on-site transporter is limited to a volume of 50 gallons. The data necessary to define the fire event is provided in Table 2.2.8.

{a) HT-STORM FW Fire The fuel tank fue is conservatively assumed to surround the HI-STORM FW overpack.

Accordingly, all exposed overpack surfaces are heated by radiation and convection heat transfer from the fire. Based on NUREG-1536 and 10 CFR 71 guidelines [4.6.1], the following fire parameters are assumed:

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-88 Rev. 5

I IOLTEC PROPRIETARY INFORMATION

1. The average emissivity coefficient must be at least 0.9. During the entire duration of the fire, the painted outer surfaces of the overpack are assumed to remain intact, with an emissivity of 0.85. It is conservative to assume that the flame emissivity is 1.0, the limiting maximum value corresponding to a perfect blackbody emitter. With a flame emissivity conservatively assumed to be 1.0 and a painted surface emissivity of 0.85, the effective emissivity coefficient is 0.85. Because the minimum required value of 0.9 is greater than the actual value of 0.85, use of an average emissivity coefficient of 0.9 is conservative.

2. The average flame temperature must be at least 1475°F (802°C). Open pool fires typically involve the entrainment of large amounts of air, resulting in lower average flame temperatures. Additionally, the same temperature is applied to all exposed cask smfaces, which is very conservative considering the size of the HI-STORM FW cask. It is therefore conservative to use the I 475°F (802°C) temperature.

3. The fuel source must extend horizontally at least l m (40 in), but may not extend more than 3 m ( l O ft), beyond the external surface of the cask. Use of the minimum ring width of l meter yields a deeper pool for a fixed quantity of combustible fuel, thereby conservatively maximizing the fire duration (specified in Table 2.2.8).

4. The convection coefficient must be that value which may be demonstrated to exist if the cask were exposed to the fire specified. Based upon results of large pool fire thermal measurements [ 4.6.2], a conservative forced convection heat transfer coefficient of 4.5 Btu/01rxft2x°F) is applied to exposed overpack surfaces during the short-duration fire.

Based on the 50 gallon fuel volume, the overpack outer diameter and the l m fuel ring width

[4.6.1], the fuel ring surrounding the overpack covers 154.1 ft2 and has a depth of 0.52 inch.

From this depth and the fuel consumption rate of 0.15 in/min, the calculated fire duration is provided in Table 2.2.8. The fuel consumption rate of 0.15 in/min is a lowerbound value from a Sandia National Laboratories report [4.6.2). Use of a lowerbound fuel consumption rate conservatively maximizes the duration of the fire.

To evaluate the impact of fire heating of the HI-STORM FW overpack, a thermal model of the overpack cylinder was constructed using FLUENT. A transient study is conducted for the duration of fire and post-fire of sufficient duration to reach maximum temperatures. The bounding steady state HI-STORM FW normal storage temperatures (short fuel scenario in MPC-37, see Table 4.4.3) are adopted as the initial condition for the fire accident (fire and post-fire) evaluation. The transient study was conducted for a sufficiently long period to allow temperatures in the overpack to reach their maximum values and begin to recede.

Due to the severity of the fire condition radiative heat flux, heat flux from incident solar radiation is negligible and is not included. Furthermore, the smoke plume from the fire would block most of the solar radiation.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-89 Rev. 5

I IOLTEC PRO~RIETARY INFORMATIOl<l The thennal transient response of the storage overpack is determined using FLUENT. Time-histories for points in the storage overpack are monitored for the duration of the fire and the subsequent post-fire equilibrium phase.

Heat input to the HI-STORM FW overpack while it is subjected to the fire is from a combination of incident radiation and convective heat flux to all external surfaces. This can be expressed by the following equation:

where:

qF =Surface Heat Input Flux (Btu/ft2-hr) hfc = Forced Convection Heat Transfer Coefficient (4.5 Btu/ft2-hr-°F) cr = Stefan-Boltzmann Constant TA= Fire Temperature (1475°F)

C= Conversion Constant (460 (°F to 0R))

Ts = Surface Temperature (°F) s = Average Emissivity (0.90 per 10 CFR 71.73)

The forced convection heat transfer coefficient is based on the results of large pool fire thennal measurements [ 4.6.2].

After the fire event, the ambient temperature is restored and the storage overpack cools down (post-fire temperature relaxation). Heat loss from the outer surfaces of the storage overpack is determined by the following equation:

where:

gs =Surface Heat Loss Flux (W/m2 (Btu/ft2-hr))

hs = Natural Convection Heat Transfer Coefficient (Btu/:ft:2-hr-°F)

Ts = Surface Temperature (°F))

TA = Ambient Temperature (°F) cr = Stefan-Boltzmann Constant s = Surface Emissivity C= Conversion Constant (460 (°F to 0R))

In the post-fire temperature relaxation phase, hs is obtained using literature correlations for natural convection heat transfer from heated surfaces [ 4.2.9]. Solar insolation was included during post-fire event. An emissivity of bare carbon steel (see Table 4.2.4) is used for all the cask outer surfaces during post-fire analysis.

The results of the fire and post-fire events are repo1ted in Table 4.6.2. These results demonstrate that the fire accident event has a minor effect on the fuel cladding temperature. In addition, the local concrete temperature is well below its short-tenn temperature limit (Table 2.2.3). The HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-90 Rev. 5

lelObTEG PROPRIETARY INFORMATIOl<l temperatures of the basket and components of MPC and HI-STORM FW overpack (see Table 4.6.2) are within the allowable temperature limits.

Table 4.6.2 shows a slight increase in fuel temperature following the fire event. Thus the impact on the MPC internal helium pressure is conespondingly small. Based on a conservative analysis of the HI-STORM FW system response to a hypothetical fire event, it is concluded that the fire event does not adversely affect the temperature of the MPC or contained fuel. Thus, the ability of the HI-STORM FW system to maintain the spent nuclear fuel within design temperature limits during and after fire is assured.

(b) HI-TRAC VW Fire In this subsection the fuel cladding and MPC pressure boundary integrity under an exposure to a short duration fire event is demonstrated. The HI-TRAC VW is initially (before fire) assumed to be loaded to design basis decay heat and has reached steady-state maximum temperatures. The analysis assumes a fire from a 50 gallon transporter fuel tank spill. The fuel spill, as discussed in Subsection 4.6.2.l(a) is assumed to surround the HI-TRAC VW in a 1 m wide ring. The fire parameters are same as that assumed for the HI-STORM FW fire discussed in this preceding subsection. In this analysis, the HI-TRAC VW and its contents are conservatively postulated to undergo a transient heat-up as a lumped mass from the decay heat and heat input from the fire.

Based on the specified 50 gallon fuel volume, HI-TRAC VW cylinder diameter (7.9 ft) and the I m fuel ring width, the fuel ring area is 115.2 ft2 and has a depth of 0.696 in. From this depth and the fuel consumption rate of 0.15 in/min, the fire duration 'tf is calculated to be 4.64 minutes (279 seconds). The fuel consumption rate of 0.15 in/min is a lowerbound value from Sandia Report

[ 4.6.1]. Use of a lowerbound fuel consumption rate conservatively maximizes the duration of the fire.

From the HI-TRAC VW fire analysis, a bounding rate of temperature rise 2.722°F per minute is determined. Therefore, the total temperature rise is computed as the product of the rate of temperature rise and 'tr is 12.6°F. Because the cladding temperature at the start of fire is substantially below the accident temperature limit, the fuel cladding temperature limit during HI-TRAC VW fire is not exceeded. To confirm that the MPC pressure remains below the design accident pressure (Table 2.2.1) the MPC pressure resulting from fire temperature rise is computed using the Ideal Gas Law. The result (see Table 4.6.7) is below the pressure limit (see Table 2.2. l ).

4.6.2.2 Jacket Water Loss In this subsection, the fuel cladding and MPC boundary integrity is evaluated under a postulated (non-mechanistic) loss of water from the HI-TRAC VW water jacket. For a bounding analysis, all water compartments are assumed to lose their water and be replaced with air. The HI-TRAC VW is assumed to have the maximum thermal payload ( design heat load) and assumed to have reached steady state (maximum) temperatures. Under these assumed set of adverse conditions, HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-91 Rev. 5

HO! IEC PROPRIETARY INFORMATION the maximum temperatures are computed and reported in Table 4.6.3. The results of jacket water loss evaluation confirm that the cladding, MPC and HI-TRAC VW component temperatures are below the limits prescribed in Chapter 2 (Table 2.2.3). The co-incident MPC pressure is also computed and compared with the MPC accident design pressure (Table 2.2.1). The result (Table 4.6.7) shows a positive margin of safety.

4.6.2.3 Extreme Environmental Temperatures To evaluate the effect of extreme weather conditions, an extreme ambient temperature (Table 2.2.2) is postulated to persist for a 3-day period. For a conservatively bounding evaluation the extreme temperature is assumed to last for a sufficient duration to allow the HI-STORM FW system to reach steady state conditions. Because of the large mass of the HI-STORM FW system, with its corresponding large thermal inertia and the limited duration for the extreme temperature, this assumption is conservative. Starting from a baseline condition evaluated in Section 4.4 (normal ambient temperature and limiting fuel storage configuration) the temperatures of the HI-STORM FW system are conservatively asswned to rise by the difference between the extreme and normal ambient temperatures ( 45°F). The HI-STORM FW extreme ambient temperatures computed in this manner are repo1ted in Table 4.6.4. The co-incident MPC pressure is also computed (Table 4.6.7) and compared with the accident design pressure (Table 2.2.1), which shows a positive safety margin. The result is confirmed to be below the accident limit.

4.6.2.4 100% Blockage of Air Inlets This event is defined as a complete blockage of all eight bottom inlets for a significant duration (32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br />). The immediate consequence of a complete blockage of the air inlets is that the normal circulation of air for cooling the MPC is stopped. An amount of heat will continue to be removed by localized air circulation patterns in the overpack annulus and outlet ducts, and the MPC will continue to radiate heat to the relatively cooler storage overpack. As the temperatures of the MPC and its contents rise, the rate of heat rejection will increase correspondingly. Under this condition, the temperatures of the overpack, the MPC and the stored fuel assemblies will rise as a function of time.

As a result of the considerable inertia of the storage overpack, a significant temperature rise is possible if the inlets are substantially blocked for extended durations. This accident condition is, however, a short duration event that is identified and corrected through scheduled periodic surveillance. Nevertheless, this event is conservatively analyzed assuming a substantial duration of blockage. The HI-STORM FW thermal model is the same 3-Dimensional model constructed for normal storage conditions (see Section 4.4) except for the bottom inlet ducts, which are assumed to be impervious to air. Using this model, a transient thermal solution of the HI-STORM FW system starting from normal storage conditions is obtained. The results of the blocked ducts transient analysis are presented in Table 4.6.5 and compared against the accident temperature limits (Table 2.2.3). The co-incident MPC pressure (Table 4.6.7) is also computed HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-92 Rev. 5

I IOLTEC PROPRIETARY INFORMATION and compared with the accident design pressure (Table 2.2.1). All computed results are well below their respective limits.

It must be noted that the heat rejection capacity of the HI-STORM FW System is better when all the outlet vents are blocked instead of all the inlet vents. This is because in the event of inlet vents being unblocked, cold air can enter the system through the inlet vents and remove heat from the MPC. Therefore, a 100% of inlet vent blockage is more bounding than 100% outlet vents being blocked. The amount of heat removed from the MPC external surfaces by natural circulation of air is reduced to less than 7% of that under normal conditions (i.e. when inlet and outlet vents completely unblocked). Therefore, in an unlikely event of complete blockage of both inlet and outlet vents, that small additional heat removal capability by air through outl.et vents is also lost. This will result in a small temperature rise compared to the large available temperature margins (greater than 80°C) established from the transient study of complete inlet vents blockage.

4.6.2.5 Burial Under Debris (Load Case AG in Table 2.2.13)

Burial of the HI-STORM FW system under debris is not a credible accident. During storage at the ISFSI there are no structures that loom over the casks whose collapse could completely bury the casks in debris. Minimum regulatory distances from the ISFSI to the nearest ISFSI security fence precludes the close proximity of substantial amount of vegetation. There is no credible mechanism for the HI-STORM FW system to become completely buried under debris. However, for conservatism, the scenario of complete burial under debris is considered.

For this purpose, an exceedingly conservative analysis that considers the debris to act as a perfect insulator is considered. Under this scenario, the contents of the HI-STORM FW system will undergo a transient heat up under adiabatic conditions. The minimum available time (Llt') for the fuel cladding to reach the accident limit depends on the following: (i) thermal inertia of the cask, (ii) the cask initial conditions, (iii) the spent nuclear fuel decay heat generation and (iv) the margin between the initial cladding temperature and the accident temperature limit. To obtain a lowerbound on !::..:t, the HI-STORM FW overpack thermal inettia (item i) is w1derstated, the cask initial temperature (item ii) is maximized, decay heat overstated (item iii) and the cladding temperature margin (item iv) is understated. A set of conservatively postulated input parameters for items (i) through (iv) are summarized in Table 4.6.6. Using these parameters t::..-r is computed as follows:

where:

mxcP xt::..T

!::..r=----

t::..-r = minimum available burial time (hr) m = Mass of HI-STORM FW System (lb)

Cp = Specific heat capacity (Btu/lb-°F) t::..T = Permissible temperature rise (°F)

Q = Decay heat load (Btu/hr)

Q HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-93 Rev. 5

lelObTi;C PROPRIETARY INFORMATION Substituting the parameters in Table 4.6.6, the minimum available burial time is computed as 57.6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> for the short fuel assembly (l5xl5I). A site-specific calculation based on the methodology described herein can be performed to determine the burial time limits. The co-incident MPC pressure (see Table 4.6.7) is also computed and compared with the accident design pressure (Table 2.2.1). These results indicate that HI-STORM FW has a substantial thermal sink capacity to withstand complete burial-under-debris events.

4.6.2.6 Evaluation of Smart Flood (Load Case AD in Table 2.2.13)

A number of design measures are taken in the HI-STORM FW system to limit the fuel cladding temperature rise under a most adverse flood event (i.e., one that is just high enough to block the inlet duct). An unlikely adverse flood accident is assumed to occur with flood water upto the inlet height and is termed as 'smart flood'. The inlet duct is narrow and tall so that blocking the inlet ducts completely would require that flood waters wet the bottom region of the MPC creating a heat sink.

The inlet duct is configured to block radiation efficiently even if the radiation emanating from the MPC is level (coplanar) with the duct penetration. The MPC stands on the base plate, which is welded to the inner and outer shell of the overpack. Thus, if the flood water rises high enough to block air flow through the bottom ducts, the lower region of the MPC will be submerged in the water. Although heat transport through air circulation is cut off in this scenario, the reduction is substantially offset by flood water cooling.

The MPCs are equipped with the thermosiphon capability, which brings the heat emitted by the fuel to the bottom region of the MPC as the circulating helium flows along the downcomer space around the basket. This places the heated helium in close thermal communication with the flood water, fmther enhancing convective cooling via the flood water.

The most adverse flood condition exists when the flood waters are high enough to block the inlet ducts but no higher. In this scenario, the MPC surface has minimum submergence in water and the ventilation air is completely blocked. In fact, as the flood water begins to accumulate on the ISFSI pad, the air passage size in the inlet vents is progressively reduced. Therefore, the rate of floodwater rise with time is necessary to analyze the thermal-hydraulic problem. For the reference design basis flood (DBF) analysis in this FSAR, the flood waters are assumed to rise instantaneously to the height to block the inlet vents and stay at that elevation for 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br />. The consequences of the DBF event is bounded by the 100% blocked ducts events evaluated in Section 4.6.2.4. If the duration of the flood blockage exceeds the DBF blockage duration then a site specific evaluation shall be perfo1med in accordance with the methodology presented in this Chapter and evaluated for compliance with Subsection 2.2.3 criteria.

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I IOLTEC PROPRIETARY INFORMATION Table 4.6.1 OFF-NORMAL CONDITION MAXIMUM HI-STORM FW TEMPERA TURES Component Off-Normal Ambient Partial Inlets Duct Temperature*

Blockage oc (OF) oc (OF)

Fuel Cladding 384 (723) 385 (725)

MPC Basket 369 (696) 371 (700)

Aluminum Basket Shims 301 (574) 285 (545)

MPC Shell 251 (484) 257 (495)

MPC Lid 246 (475) 252 (486)

Overpack Inner Shell 137 (279) 141 (286)

Overpack Outer Shell 76 (169) 62 (144)

Overpack Body Concrete 139 (282tote 1 141 (286)

Local Temperature Overpack Lid Concrete Local 144 (29Itote 1 141 (286)

Temperature Note 1: The maximum local temperatures of body concrete and lid concrete under normal long-term storage condition are 128°C (262°F) and l33°C (271 °F) respectively. The temperatures of concrete reported in this table are obtained by adding 11 °C (20°F) to these local concrete temperatures.

• Obtained by adding the difference between extreme ambient and normal temperature difference (11.1 °C (20°F)) to normal condition temperatures reported in Table 4.4.3.

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I IOLTEC PROPRIETARY INFORMATIOl<l Table 4.6.2 HI-STORM FW FIRE AND POST-FIRE ACCIDENT ANALYSIS RESULTS Initial End of Fire Post-Fire Component Condition otc 3 Condition Cooldown oc (OF) oc (OF) oc (OF)

Fuel Cladding 375 (707) 375 (707) 376 (709)

MPC Basket 361 (682) 361 (682) 362 (684)

Basket Periphery 297 (567) 297 (567) 298 (568)

Aluminum Basket 276 (529) 276 (529) 277 (53 1)

Shims MPC Shell 246 (475) 250 (482) 250 (482)

MPC LidNote 1 243 (469) 242 (468) 244 (47 1)

Overpack Inner Shell 128 (262) 133 (271) 133 (271)

Overpack Outer Shell 60 (140) 337 (639) Note2 337 (639) Note2 Overpack Body Concrete Local 128 (262) 456 (853) 456 (853)

Temperature Overpack Lid Concrete Local 133 (271) 412 (774) 412 (774)

Temperature Note 1: Maximum section average temperature is reported.

Note 2: Surface average temperature is reported.

Note 3: The initial condition used for the thermal analysis of hypothetical fire condition bounds the predicted temperatures for nonnal long-term storage condition (Table 4.4.3).

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I IOLTEC PROPRIETARY INFORMATION Table 4.6.3 HI-TRAC VW JACKET WATER LOSS MAXIMUM TEMPERA TURES Component Temperature oc (OF)

Fuel Cladding 432(810)

MPC Basket 416 (781)

Basket Periphery 342 (648)

Aluminum Basket Shims 314 (597)

MPC Shell 290 (554)

MPC Lid*

263 (505)

HI-TRAC VW Inner Shell 205 (401)

HI-TRAC VW Radial Lead Gamma 204 (399)

Shield Maximum section average temperature is reported.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-97 Rev. 5

HOLTEC PROPRIE I ARV INFORMA I ION Table 4.6.4 EXTREME ENVIRONMENTAL CONDITION MAXIMUM HI-STORM FW TEMPERA TURES Component Temperature*

Oc (OF)

Fuel Cladding 398 (748)

MPC Basket 383 (721)

Basket Periphery 315 (599)

Aluminum Basket Shims 292 (558)

MPC Shell 265 (509)

MPC LidNotc 1 260 (500)

Overpack Inner Shell 151 (304)

Overpack Outer Shell 90 (194)

Overpack Body Concrete Local Temperature Note 1 153 (307)

Overpack Lid Concrete Local Temperature Note 1 158 (316)

Average Air Outlet 128 (262)

Note 1: The maximum local temperatures of body concrete and lid concrete under normal long-te1m storage condition are 128°C (262°F) and l 33°C (271 °F) respectively. The temperatures of concrete reported in this table are obtained by adding 25°C (45°F) to these local concrete temperatures.

• Obtained by adding the difference between extreme ambient and normal temperature difference (25°C (45°F)) to normal condition temperatures reported in Table 4.4.3.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-98 Rev. 5

t,,tOLTEC PROPRIETA~V INFORMA I ION Table 4.6.5 RESULTS OF HI-STORM FW 32-HOURS BLOCKED INLET DUCTS THERMAL ANALYSIS Component Temperature oc (OF)

Fuel Cladding 470 (878)

MPC Basket 453 (847)

Basket Periphery 388 (730)

Aluminum Basket Shims 363 (685)

MPC Shell 340 (644)

MPC LidNotc 1 293 (559)

Overpack Inner Shell 238 (460)

Overpack Outer Shell 105 (22 l)

Overpack Body Concrete Local 236 (457)

Temperature Overpack Lid Concrete Local 175 (347)

Temperature Note I: Maximum section average temperature is reported.

HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-99 Rev. 5

I IOLTEC PROPRIETARY INFORMATION Table 4.6.6

SUMMARY

OF INPUTS FOR BURIAL UNDER DEBRIS ANALYSIS Thermal Inertia Inputs*:

M (Lowerbound HI-STORM FW Weight) 139172 kg Cp (Carbon steel heat capacity) t 419 J/kg-°C Clad initial temperatureNote 1 390°c Q (Decay heat) 45kW LiT (clad temperature margin):

160°C Note 1: Initial temperature conservatively postulated to bound the maximum cladding tern peratu re.

Thermal inertia of fuel is conservatively neglected.

't t

Used carbon steel's specific heat since it has the lowest heat capacity among the principal materials employed in MPC and overpack construction (carbon steel, stainless steel, Metamic-HT and concrete).

The clad temperature margin is conservatively understated in this table.

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HOLfEC PROPRIETARY l~IFORMATION Table 4.6.7 OFF-NORMAL AND ACCIDENT CONDITION MAXIMUM MPC PRESSURES Condition Pressure (psi2)

Off-Nonna! Conditions Off-Normal Pressure*

110.0 Partial Blockage oflnlet Ducts 99.9 Accident Conditions HI-TRAC VW fire accident 103.3 Extreme Ambient Temperature lOl.7 100% Blockage of Air Inlets 116.4 Burial Under Debris 130.8 HI-TRAC VW Jacket Water Loss 109.5

• The off-normal pressure event defined in Section 4.6. 1.1 bounds the off-normal ambient temperature event (Section 4.6.1.2)

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I IOLTEC PROPRIETARY INFORMATION 4.7 REGULATORY COMPLIANCE 4.7.1 Normal Conditions of Storage NUREG-1536 [ 4.4.1] and ISG-11 [ 4.1.4] define several thermal acceptance criteria that must be applied to evaluations of normal conditions of storage. These items are addressed in Sections 4.1 through 4.4. Each of the pertinent criteria and the conclusion of the evaluations are summarized here.

As required by ISG-11 [ 4.1.4], the fuel cladding temperature at the beginning of dry cask storage is maintained below the anticipated damage-threshold temperatures for normal conditions for the licensed life of the HI-STORM FW System. Maximum clad temperatures for long-term storage conditions are reported in Section 4.4.

As required by NUREG-1536 (4.0,IV,3), the maximum internal pressure of the cask remains within its design pressure for normal conditions, assuming rupture of 1 percent of the fuel rods.

Assumptions for pressure calculations include release of 100 percent of the fill gas and 30 percent of the significant radioactive gases in the fuel rods. Maximum internal pressures are reported in Section 4.4 and shown to remain below the normal design pressures specified in Table 2.2.1.

As required by NUREG-1536 (4.0,IV,4), all cask and fuel materials are maintained within their minimum and maximum temperature for normal and off-no1mal conditions in order to enable components to perform their intended safety functions. Maximum and minimum temperatures for long-term storage conditions are reported in Section 4.4 which are shown to be well below their respective Design temperature limits summarized in Table 2.2.3.

As required by NUREG-1536 (4.0,IV,5), the cask system ensures a very low probability of cladding breach during long-term storage. For long-te1m normal conditions, the maximum CSF cladding temperature is shown to be below the ISG-11 [ 4.1.4] limit of 400°C (752°F).

As required by NUREG-1536 (4.0,IV,7), the cask system is passively cooled. All heat rejection mechanisms described in this chapter, including conduction, natural convection, and the1mal radiation, are completely passive.

As required by NUREG-1536 (4.0,IV,8), the thermal performance of the cask is within the allowable design criteria specified in SAR Chapters 2 and 3 for normal conditions. All thermal results reported in Section 4.4 are within the design criteria under all normal conditions of storage.

4.7.2 Short-Term Operations Evaluation of short-term operations is presented in Section 4.5 wherein complete compliance with the provisions of ISG-1 1 [ 4.1.4] is demonstrated. In particular, the ISG-11 requirement to HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL REPORT HI-2114830 HI-STORM FW SYSTEM FSAR Revision 5, June 20, 2017 4-102 Rev. 5

HOLTEC PROPRIETARY INF-ORMATION ensure that maximum cladding temperatures under all fuel loading and short-term operations be below 400°C (752°F) for high burnup fuel and below 570°C (1058°F) for moderate burnup fuel (Table 4.3.1) is demonstrated.

Further, as required by NUREG-1536 (4.0,IV, 4), all cask and fuel materials are maintained within their minimum and maximum temperature for all short-term operations in order to enable components to perform their intended safety functions.

As required by NUREG-1536 (4.0,IV,8), the thermal performance of the cask is within the allowable design criteria specified in SAR Chapters 2 and 3 for all short-term operations.

4.7.3 Off-Normal and Accident Conditions As required by NUREG-1536 (4.0,IV,3), the maximum internal pressure of the cask is evaluated in Section 4.6 and shown to remain within its off-normal and accident design pressure, assuming rnpture of 10 percent and 100 percent of the fuel rods, respectively. Assumptions for pressure calculations include release of 100 percent of the fill gas and 30 percent of the significant radioactive gases in the fuel rods.

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I IOLTEG PROPRle:r.ARY lf)IFORMAJIQN

4.8 REFERENCES

[4.1.1] ANSYS Finite Element Modeling Package, Swanson Analysis Systems, Inc., Houston, PA, 1993.

[ 4.1.2] FLUENT Computational Fluid Dynamics Software, Fluent, Inc., Centerra Resource Park, 10 Cavendish Court, Lebanon, NH 03766.

[ 4.1.3] "The TN-24P PWR Spent-Fuel Storage Cask: Testing and Analyses," EPRI NP-5128, (April 1987).

[ 4.1.4] "Cladding Considerations for the Transportation and Storage of Spent Fuel," Interim StaffGuidance - 11, Revision 3, USNRC, Washington, DC.

[4.1.5] Topical Report on the HI-STAR/HI-STORM Thermal Model and its Benchmarking with Full-Size Cask Test Data," Holtec Report Hl-992252, Revision 1, Holtec International, Marlton, NJ, 08053.

[ 4.1.6] "Identifying the Appropriate Convection Correlation in FLUENT for Ventilation Air Flow in the HI-STORM System", Revision l, Holtec Report Hl-2043258, Holtec International, Marlton, NJ, 08053.

[4.1.7] "Performance Testing and Analyses of the VSC-17 Ventilated Concrete Cask", EPRl TR-100305, (May 1992).

[4.1.8] "Holtec International Final Safety Analysis Report for the HI-STORM 100 Cask System", Holtec Report No. 2002444, Revision 7, NRC Docket No. 72-1014.

[4.1.9] "The1mal Evaluation of HI-STORM FW", Holtec Report HI-2094400, Latest Revision.

[4.1.10] "Effective Thermal Properties of PWR Fuel in MPC-37", Holtec Repo1t HI-2094356, Revision 0.

[4.1.11] "Safety Analysis Report on the HI-STAR 180 Package", Holtec Report HI-2073681, Latest Revision.

[ 4.2.1] Baumeister, T., Avallone, E.A. and Baumeister III, T., "Marks' Standard Handbook for Mechanical Engineers," 8th Edition, McGraw Hill Book Company, (1978).

[4.2.2] Rohsenow, W.M. and Hartnett, J.P., "Handbook of Heat Transfer," McGraw Hill Book Company, New York, (1973).

[ 4.2.3] Creer et al., "The TN-24P Spent Fuel Storage Cask: Testing and Analyses," EPRI NP-5128, PNL-6054, UC-85, (April 1987).

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lelObTEG PROPRIETARY INFORMATIOl<l

[4.2.4] Rust, J.H., "Nuclear Power Plant Engineering," Haralson Publishing Company, (1979).

[4.2.5] Kern, D.Q., "Process Heat Transfer," McGraw Hill Kogakusha, (1950).

[ 4.2.6] "Metamic-HT Qualification Sourcebook", Holtec Report HI-2084122, Latest Revision.

[4.2.7] "Spent Nuclear Fuel Effective Thermal Conductivity Report," US DOE Report BBA000000-01717-5705-00010 REV 0, (July 11, 1996).

[4.2.8] ASME Boiler and Pressure Vessel Code,Section II, Part D, (1995).

[4.2.9] Jakob, M. and Hawkins, G.A., "Elements of Heat Transfer," John Wiley & Sons, New York, (1957).

[4.2.10] ASME Steam Tables, 3rd Edition (1977).

[4.2.11] "Nuclear Systems Materials Handbook, Vol. 1, Design Data", ORNL TID 26666.

[4.2.12] "Scoping Design Analyses for Optimized Shipping Casks Containing 1-, 2-, 3-, 5-, 7-, or 10-Year-Old PWR Spent Fuel", ORNL/CSD/TM-149 TTC-0316, (1983).

[4.2.13] Not used.

[4.2.14] Not used.

[ 4.2.15] Not used.

[4.2.16] USNRC Docket no 72-1027, TN-68 FSAR & Docket no 72-1021 TN-32 FSAR.

[ 4.2.17] Hagrman, Reymann and Mason, "MA TPRO-Version 11 (Revision 2) A Handbook of Materials Properties for Use in the Analysis of Light Water Reactor Fuel Rod Behavior,"

NUREG/CR-0497, Tree 1280, Rev. 2, EG&G Idaho, August 1981.

[ 4.2.18] "Effective Thermal Conductivity and Edge Conductance Model for a Spent-Fuel Assembly," R. D. Manteufel & N. E. Todreas, Nuclear Technology, 105, 421-440, (March 1994).

[ 4.2.19] Aluminum Alloy 2219 Material Data Sheet, ASM Aerospace Specification Metals, Inc.,

Pompano Beach, FL.

[4.2.20] "Spacecraft Thermal Control Coatings References", NASA Publication NASA/TP-2005-212792, December 2005.

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I IOLTEC PROPRIETARY INFORMATION

[4.4.1] NUREG-1536, "Standard Review Plan for Dry Cask Storage Systems," USNRC, (January 1997).

[ 4.4.2] "Pressure Loss Charactersistics for In-Cell Flow of Helium in PWR and BWR Storage Cells", Holtec Report HI-2043285, Revision 6, Holtec International, Marlton, NJ, 08053.

[4.4.3] "Standard for Verification and Validation in Computational Fluid Dynamics and Heat Transfer", ASME V&V 20-2009.

[4.5. 1] "Procedure for Estimating and Reporting of Uncertainty due to Discretization in CFD Applications", I.B. Celik, U. Ghia, P.J. Roache and C.J. Freitas (Journal of Fluids Engineering Editorial Policy on the Control of Numerical Accuracy).

[ 4.5.2] Holtec Position Paper DS-412, "A Method to Compute the Time-to-Boil for a Loaded Canister in HI-TRAC", (Holtec Proprietary).

[4.6.l] United States Code of Federal Regulations, Title 10, Part 71.

[ 4.6.2] Gregory, J.J. et. al., "Thermal Measurements in a Series of Large Pool Fires", SAND85-1096, Sandia National Laboratories, (August 1987).

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