Conceptual Thermal Study on Korean Transport Cask for Spent Fuel - PowerPoint PPT Presentation

International Technical Seminar on SNF Storage and Transportation November 5, 2010. Daejeon Korea Conceptual Thermal Study on Korean Transport Cask for Spent Fuel Considering Burnup Credit Yong-Hoon Lee

Contents • Background – Capacity Selection for Standard and BUC Casks – Burnup Credit (BUC) – Comparison of Standard and BUC Casks – Conceptual Model for 24FA BUC Cask • Thermal Evaluation – Numerical Models: Personnel Barrier / Homogenization – Numerical Techniques – Results • Thermal Loading Curves • Conclusions International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Background Development of Radioactive Waste Management Technology (MKE, KRMC) Development of Core Technology of Transportation and Storage of Spent Fuel (KRMC, KONES , etc.) Assessment Technology for Feasibility Study for Transport Conceptual Transport and System considering Burnup Storage Systems Credit International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Burnup Credit (BUC) • Burnup Credit – Reduction in Reactivity due to Depletion of SNFs. – Consider a Change of Isotopic Compositions. – High Fuel Initial Enrichment + High Burnup Reactor Operation • Benefits of considering Burnup Credit – Increase the Number of Fuels in a Cask with Same Size Number of Cask Transportation and Cost – Reduce Amount of Neutron Absorption Material Radiological Risk International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Capacity Selection for Standard Cask Marginal Weight = 2.4 ton Maximum Lifting Weight of Transport Cask = 108 ton Lifting Device = 3 ton Cask Crane Capacity = 113.4 ton Conceptual Design of Conceptual Design of 21 FA Standard Cask 24 FA Standard Cask * Lifting Weight includes the Weight of Cask Body, Fuels, and Water ** [ton] = Metric Ton International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Capacity Selection for the Standard Cask Cask Thickness of Lifting Fuel Type Evaluation Capacity [FA] Disc [mm] Weight [ton] WH 106.4 20 CE 111.1 WH or CE 113.5 WH 107.0 24 25 CE 111.8 WH or CE 114.3 WH 107.7 112.5 30 CE WH or CE 115.0 20 103.1 OK 21 25 WH or CE 103.7 OK 30 104.3 OK International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Capacity Selection for the BUC Cask Cask Thickness of Lifting Fuel Type Evaluation Capacity [FA] Basket [mm] Weight [ton] 8 108.5 24 6 107.6 OK 5 107.2 OK 8 109.4 26 6 WH&CE 108.4 5 108.0 OK 8 110.6 28 6 109.7 5 109.3 Conceptual Conceptual Design of Design of 24 FA BUC Cask 26 FA BUC Cask International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Comparison of Standard and BUC Casks 21 FA Cask with Flux Traps 24 FA Cask without Flux Traps Neutron Absorber Basket Flux Trap International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Conceptual Model for 24FA BUC Cask Impact limiter Overpack lid Canister lid Neutron shielding layer (resin) Outer shell Cask body Baskets with Neutron absorber Discs 3D Model of 24 FA BUC Cask Section View International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Conceptual Model for 24FA BUC Cask Structural Disc (Stainless Steel) Heat Conduction Disc (Aluminum) International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Thermal Evaluation Conditions Time Ambient Temp. Insolance Decay Heat 38 ° C (311.15K) Normal Hot condition Steady Yes Maximum Transport -40 ° C (233.15K) Cold condition Steady No Maximum Conditions -40 ° C (233.15K) Min. Temp. Steady No No 38 ° C (311.15K) Hypothetical Initial condition Steady Yes Maximum Accident 800 ° C (1073.15K) Fire phase 30 min. No Maximum Conditions 38 ° C (311.15K) Cool down phase → Steady Yes Maximum MEST Notice 2009-37 / 10 CFR Part 71 / IAEA TS-R-1 / ISG-11 rev.03 • Requirements Maximum Fuel Cladding Temperature < 400 ° C – Maximum Temperature of Any Accessible Surface < 85 ° C – Ambient Temperature Assumption = 38 ° C – • Spent Fuel Selection – Maximum Burnup: 45 GWD/MTU – Maximum Initial Enrichment: 4.5 wt% – Minimum Cooling Time: 10 year International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Numerical Models: Personnel Barrier Personnel Barrier Solving Heat Balance: T int = 42.35 ° C T hood = 71 ° C < 85 ° C International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Numerical Models: Homogenization • Homogenized Spent Fuel Model Homogenized Helium Backfill Fuel, Cladding, Cladding and Helium Helium Gap Fuel Pellet • Homogenized Model Gives: – Reduction of the Cost and Time for Computation – To Make Possible to Compute Transient Solution International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Numerical Models: Homogenization Constant Temperature Wall Constant Temperature Wall Symmetry Symmetry • Effective Properties of Homogenized Model – Considering Full Spent Fuel Geometry – Considering Conduction and Radiation Heat Transfer International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Analysis Techniques • Numerical Analysis Software: ANSYS FLUENT v12.0 • Governing Equations and Models – Flow Equations (Continuity, Momentum) – Energy Equation with Ideal Gas Law – Homogenized Thermal Properties Model – Discrete Ordinate Radiation Heat Transfer Model – Personal Barrier Model – Correlations for Natural Convection and Radiation • Solving Techniques – FVM on Collocated and Unstructured 3D Hexagonal Grid System – SIMPLE Method for Pressure-Velocity Coupling – Second-order Upwind Differencing for Spatial Discretization International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Results: 45GWD/MTU, 4.5wt% T max = 658K (385 ° C) International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Results: 45GWD/MTU, 4.5wt% Parts Requirements Results Under 85 ° C 71 ° C Outer of Package Surface Temperature Under 371 ° C 136 ° C Cask Body (CS) Containment, -40~250 ° C 121 ° C O-Ring Seal Shielding, Satisfied Sub criticality Under 148 ° C 127 ° C Neutron Shield (Resin) Functions Under 454 ° C 383 ° C Neutron Absorber Under 400 ° C 385 ° C Fuel Cladding Temperature International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Loading Curves: Thermal Acceptance 45 Not Acceptable 44 43 100% 42 41 Higher Burnup, More Heat 40 92.7% 39 Burnup(GWD/MTU) 38 37 36 35 Acceptable 34 33 32 31 30 29 2 21FA S Sta tandard Cask 28 27 2 24FA B BUC Cask 26 25 1.5 2.0 2.5 3.0 3.5 4.0 4.5 U-235 Initial Enrich(wt%) International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Conclusions • Conceptually Designed BUC Casks for 24 and 26 FA – Identical design of cask overpack, Modified design of canister for applying BUC – Weight limit is the most severe condition for designing higher capacity casks • Studied Thermal Behavior of Conceptual 24 FA BUC Cask – Considered Conduction, Natural Convection, Radiation heat transfer – Aluminum conduction discs take a major role in transferring heat – For NTC with a burnup of 45GWD/MTU and 4.5wt% enrichment, 24 FA cask could meet the regulatory requirements • Now working on the HAC for the 24 FA cask and the thermal analysis of NTC+HAC for the 26 FA cask International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.