Sensitivity of Reflector on Neutronic Parameter for Conversion Core Design of the TRIGA Research Reactor

Abstract
The fuel of TRIGA core is specific and raise a big problem for a continuous operation of reactor. It was no longer produced by TRIGA International anymore. Meanwhile, the demand of radioisotope production in Indonesia and also in the world is still increasing. Therefore, the research reactor which has irradiation facilities and neutron flux for radioisotope production still needed. The TRIGA MARK II core conversion to plate-type fuel can be an appropriate solution. The fuel that used for conceptual design TRIGA MARK II core is MTR type, low enriched uranium, 19.75% enriched in 235U. It is important to study the effect of reflector on neutronic parameter to determine the optimal neutron flux in the core. Optimization of neutron fluxes in irradiation positions is one of great concern in a research reactor utilization. The approach in this research is based upon an optimization of the core configuration combined with improvement of reflector characteristics. This simulation study conducted by using the standard reactor physics simulation codes WIMSD-5B and Batan-FUEL. The present study is to analyze the effect of different reflector on neutronic parameter using diffusion code. TRIGA core design comprise 16 fuel elements and 4 control rods put in 5 x 5 position of grids plate and by loading reflector elements at outside the core. The aim of this research is to get the optimal design such as the highest neutron fluxes at the central flux trap position and also at irradiation positions in the core. it also becomes fuel cycle length of this core a concern. The requirement for the neutron flux at trap irradiation position is not less than 6x1013 n/cm2s at 2 MW of power. The core configuration which proposed meets the acceptance criteria such as stuck rod condition, thermal neutron flux at the trap position and shutdown margin. But it still has the lower burn up criteria for its safe operation at 2 MW of power.