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

Conceptual Thermal Study on Korean Transport Cask for Spent Fuel Considering Burnup Credit

Yong-Hoon Lee

International Technical Seminar on SNF Storage and Transportation November 5, 2010. Daejeon Korea

International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

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 Core Technology of Transportation and Storage of Spent Fuel (KRMC, KONES, etc.) Assessment Technology for Conceptual Transport and Storage Systems Feasibility Study for Transport System considering Burnup Credit Development of Radioactive Waste Management Technology (MKE, KRMC)

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

Cask Crane Capacity = 113.4 ton Lifting Device = 3 ton Marginal Weight = 2.4 ton Maximum Lifting Weight of Transport Cask = 108 ton Conceptual Design of 21 FA Standard Cask Conceptual Design of 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 Capacity [FA] Thickness of Disc [mm] Fuel Type Lifting Weight [ton] Evaluation 24 20 WH 106.4 CE 111.1 WH or CE 113.5 25 WH 107.0 CE 111.8 WH or CE 114.3 30 WH 107.7 CE 112.5 WH or CE 115.0 21 20 WH or CE 103.1 OK 25 103.7 OK 30 104.3 OK

International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Capacity Selection for the BUC Cask

Cask Capacity [FA] Thickness of Basket [mm] Fuel Type Lifting Weight [ton] Evaluation 24 8 WH&CE 108.5 6 107.6 OK 5 107.2 OK 26 8 109.4 6 108.4 5 108.0 OK 28 8 110.6 6 109.7 5 109.3

Conceptual Design of 24 FA BUC Cask Conceptual Design of 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 Flux Trap Basket

International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Conceptual Model for 24FA BUC Cask

3D Model of 24 FA BUC Cask Impact limiter Canister lid Neutron shielding layer (resin) Cask body Baskets with Neutron absorber Discs Outer shell Overpack lid 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

Normal Transport Conditions Hot condition Steady 38°C (311.15K) Yes Maximum Cold condition Steady

• 40°C (233.15K)

No Maximum

• Min. Temp.

Steady

• 40°C (233.15K)

No No Hypothetical Accident Conditions Initial condition Steady 38°C (311.15K) Yes Maximum Fire phase 30 min. 800°C (1073.15K) No Maximum Cool down phase → Steady 38°C (311.15K) 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

Tint = 42.35°C Solving Heat Balance: Thood = 71°C < 85°C

Personnel Barrier

International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Numerical Models: Homogenization

• Homogenized Spent Fuel Model
• Homogenized Model Gives:

– Reduction of the Cost and Time for Computation – To Make Possible to Compute Transient Solution

Fuel Pellet Helium Gap Cladding Helium Backfill Homogenized Fuel, Cladding, and Helium

International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Numerical Models: Homogenization

Symmetry Symmetry Constant Temperature Wall Constant Temperature Wall

• 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%

Tmax = 658K (385°C)

International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Results: 45GWD/MTU, 4.5wt%

Parts Requirements Results Outer of Package Surface Temperature Under 85°C 71°C Satisfied Containment, Shielding, Sub criticality Functions Cask Body (CS) Under 371°C 136°C O-Ring Seal

• 40~250°C

121°C Neutron Shield (Resin) Under 148°C 127°C Neutron Absorber Under 454°C 383°C Fuel Cladding Temperature Under 400°C 385°C

International Technical Seminar on SNF Storage and Transportation, Nov 5, 2010.

Loading Curves: Thermal Acceptance

Higher Burnup, More Heat

25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Burnup(GWD/MTU) U-235 Initial Enrich(wt%)

2 21FA S Sta tandard Cask 2 24FA B BUC Cask

Acceptable Not Acceptable

92.7% 100%

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