Monte Carlo Simulation for Designing Collimator of the Neutron Radiography Facility in Malaysia

Neutron collimator is the most important component in a neutron radiography facility set-up, which defines the neutron beam characteristic at the object plane. The neutron radiography facility in Malaysia was built at one of the radial beam ports of TRIGA MARK II PUSPATI research reactor (RTP). At present, the facility has low thermal neutron intensity at the sample position, which leads to long irradiation times; it gives many limitations for the industrial applications. The collimator used for this facility is based on step divergent collimator type. The aim of this research is to design the best geometry and to choose materials for thermal neutron collimator so as to obtain a uniform beam, high L/D ratio and a maximum thermal neutron flux at the object plane. In order to achieve this aim new collimator geometry has been designed to improve the existing radiography facility by using Monte-Carlo simulation codes of SIMRES and MCNPX. The new design results are compared with those of the existing facility. Our simulation result may be of help in the design of new collimator for neutron radiography facility.