Optimization of core configuration for the innovative research reactor

Innovative Research Reactor (RRI) is designed to serve as much as various utilization such as radioisotope production, irradiation technology, neutron beam experiment and material test. For that purposes it is needed to design reactor core that is able to provide high neutron flux, economic and high safety. The reactor uses uranium molybdenum alloy UMo-Al with low enrichment, less than 20 %, 360 g uranium content per fuel element because of its good performance and easy in waste fuel treatment. To achieve a high neutron flux in irradiation facilities, a compact core surrounded by reflector was applied. For completing the initial conceptual design of RRI, it is necessary to find optimum core configuration that produces high neutron flux. The objectives of this study is to obtain a high thermal neutron flux in irradiation positions in the reflector region. The study contains neutron diffusion calculation in the reactor core. Calculations were done by computer codes WIMSD-5B for cross section generation and BATAN Fuel for core diffusion calculation. The results showed that an optimum core configuration is T08 which is formed by using JMTR type fuel element that provides a maximum neutron flux in the center of the core is 1.09E+15 n/cm²s, in reflector region in amount to 4.48E+14 n/cm²s in the inner reflector and 3.89E+14 n/cm²s in the outer reflector. (author)