Modeling of neutronic beam for PARR-II using OpenMC

The objective of this study is to model a neutronic beam at Pakistan Research Reactor-II in order to obtain neutrons of epithermal energy for the therapy of deep seated tumors like glioblastoma multiforme etc. which have no other best alternative cure so far. The modeling of PARR-II was performed using Monte Carlo based open source simulation program called OpenMC. The core modeling was validated with reference values taken from final safety analysis report of Pakistan Research Reactor-II. The calculated value of excess reactivity is 4.14mk with an error of about 3.5% and beryllium shim worth is 19.95mk with an error of 6% and these values were found in good agreement to the reference values. For neutronic beam modeling of beam tube using different materials were done and validated by comparing with beam parametric values found in literature. The selection of reflector, moderator and filters of definite thicknesses for beam tube is based on the required energy and magnitude of the neutron flux required at the exit of tube. The variation of the total and epithermal flux was studied and found that both fluxes decrease with the increase in thickness of both reflector and moderator. In this way an optimum value of moderator thickness 11cm selected according to values of flux (108 neutrons/cm2.s) and energy of neutrons required for therapy as provided by international atomic energy commission (IAEA).