Research And Design On Fuel Bundle Of Advanced Heavy Water Reactor

AECL and Department of Engineering Physics (DEP) in Tsinghua University aremaking a cooperation on research and design of The Advanced Thorium-based HeavyWater Nuclear Energy System (TACR). The research and design on physicscharacteristics of fuel bundle is the basis for the further work.Multi-group lattice code WIMS-AECL has strong modeling capability for clustergeometry and isotopic composition, so it has been used for the design and analysis ofthe advanced CANDU reactors (ACR). The applicability of WIMS-AECL and itsnuclear data library for our routine work needs to be further validated. Especially forthe TACR analysis, the work of verification and validation seems necessary.MCNP-4B is chosen to be compared with WIMS for criticality calculation andMCBurn for burnup calculation. One of verification examples of WIMS-AECL andpractical ACR assembly are adopted as calculation model. The results of comparisonmanifest that WIMS-AECL with ENDF/B-V library leads to better results than thatwith B-VI in which there are no resonance tables of thorium isotopes. So, B-V libraryis used in our routine research work.In core design, the type of coolant and moderator must correspond to thecharacteristics and design aim of reactor. Under the limitation of not changing ACRlattice geometry, the analysis shows that adopting light water or heavy water as bothcoolant and moderator will bring some physical and economical problems. Lightwater as coolant and heavy water as moderator is the most reasonable design.Especially for thorium fuel lattice, such design has negative coolant void reactivitythat decreases with burnup.AECL is engaged in the design of ACR-1000 which has higher power thanACR-700. The power boost requires better performance of fuel assembly. Increasingthe number of cluster fuel rods can lower the maximum linear power of fuel rod andthus improve thermal-hydraulics performance and safety margin of fuel bundle. The71-rods bundle is 1/7 symmetrical and has the same basic overall dimensions and fuelloading with CANFLEX fuel. The 71-rods bundle changes the number of rings from4 to 5. The 61-rods is 1/6 symmetrical and has the same design rules with 71-rodsbundle. The power and burnup distribution of 61-rods are a little worse than those ofCANFLEX and 71-rods bundle. For thorium fuel bundle, the coolant void reactivityof 61-rods which can be negative is between TACR (43-rods) and 71-rods and thusbetter than the latter.