THE EFFECTIVENESS ANALYSIS OF FUEL BALL (KERNEL) DIMENSION SIZE AND URANIUM ENRICHMENT TO REACTOR REACTIVITY

Reactor reactivity does not only depend on reactor diameter but also radius and enrichment of fuel ball (kernel) to operate reactor optimally. This research analyses effectiveness of kernel radius and enrichment to achieve critical reactor condition. The HTR in this research adopts HTR-10 China and HTR of pebble bed. The calculations are performed by using MCNPX code in each kernel radii of 320-350 µm and enrichments of 5-10% Uranium. Kernel is composed of Uranium Dioxide coated by four outer layers: Carbon, IpyC (Inner Pyrolytic Coating), SiC (Silicon Carbides) and OpyC (Outer Pyrolytic Coating). It is called TRISO and it is distributed in pebble-bed ball using Simple Cubic Lattice whereas pebble-bed and moderator balls are distributed in the core zone using a Body Centred Cubic (BCC) lattice by ratio of 57:43. The research results are obtained that the reactor will be effective to achieve critical condition in kernel radius of 325-330 µm at 9% Uranium enrichment and will be in supercritical condition if the reactor uses more than 330 µm of kernel radius and 9% enrichment of Uranium but the reactor will be subcritical if Uranium enrichment is 5-8%.