1. 3D Coupled Fault Modelling for the Gas- cooled Fast Reactor Jason Dunstall KNOO PhD Student (EPSRC Funded) Applied Modelling and Computation Group (AMCG) Dept. Earth Sciences & Engineering Supervisors: Prof. C. Pain, Prof. A. Goddard KNOO Post-Doc. Support: Dr J Gomes

2. Presentation overview The Gas-cooled Fast Reactor –What is the GFR –Why is it of interest? –Background of HTRs –AMCG involvement with GFR Dragon Reactor Experiment –Background to the DRE –Benchmarking work using Dragon

3. What is the GFR? Gas-cooled Fast Reactor - one of six Generation IV innovative reactor systems Design specifications: –He cooled –Carbide or nitride fuel –Zr 3 Si 2 reflector, B 4 C shield –600 / 2400 MWth designs –Power density ~100 MWth / m 3 –~ 850°C outlet temperature (direct cycle)

4. Strengths of the GFR Incorporation of passive safety features –Helium chemically inert, nearly neutronically inert, single phase –Favourable reactivity coefficients Sustainability –High U utilisation, actinide management, integrated fuel cycle High temperature reactor –Improved thermal efficiency, potential for use of process heat But: high fuel rating, lack of moderation → cooling and control issues

5. Technology base for GFR Decommissioned reactors include: –Dragon (International / UK sited) –AVR, THTR (Germany) –Peach Bottom, Fort St. Vrain (USA) –Fast reactors inc. DFR / PFR (UK), Superphenix (France) Extensive UK experience from AGRs Current and future projects include: HTTR (Japan) HTR-10 (China) PBMR (South Africa) GT-MHR (Russia / General Atomics) ETDR (~2015)

6. AMCG work on GFR AMCG Codes: –EVENT (radiation transport) –FLUIDITY (CFD) –FETCH (coupled radiation-fluids interface code) Perform multiphysics analysis on GFR designs Potential for cross-cutting with VHTR - fuels & materials.

7. Background to Dragon Dragon Reactor Experiment –OECD / NEA International collaboration –Operational 1964-75, Winfrith, Dorset –World’s first HTR Testbed for HTR technology: –Fuel (TRISO particles) –Use of Helium coolant –Materials under HTR conditions Physics description: –1.5m 3 core volume –Inlet temperature ~350°C, outlet ~750°C –Normal peak core temperature ~1200°C

8. Dragon – some pictures

9. Modelling the DRE (1) Modelling the DRE: HTR benchmarking with FETCH – Reactivity measurements – Neutron fluxes & power distributions – Transients  EVENT Model: –71650 nodes –75927 surface –& volume elements Fuel (I) Fuel (II) Inner Reflector Control Rod Region Outer Reflector

10. Modelling the DRE (2) Example – Dragon first charge loading reactivity measurements and EVENT transport calculation results Dragon experimental (solid line) EVENT transport calculations

11. Future PhD work for GFR GFR (600 and / or 2400 MW) model in EVENT - benchmarking Detailed multiphysics analysis using FETCH 3D asymmetrical transients & accident scenarios including: –Control rod movement –Structural faults –Depressurisations –UTOP

12. Summary Use of well documented Dragon experiment for benchmarking of FETCH Need for comprehensive awareness of materials, thermal hydraulics and control issues for GFR Address use of fast spectrum cross section data Plan to perform detailed GFR coupled transient fault studies