Simulation Design of Thermal Neutron Collimators for Neutron Capture Studies at The Dalat Research Reactor

摘要

Background and Objective: The neutron beams at the Dalat nuclear research reactor have been utilized for experimental researches based on the neutron capture reaction (n,γ) and prompt gamma neutron activation analysis. In recent years, a national project has been carried out for extending and improving the physical characteristics of the beam facilities. The objective of this study is to improve the thermal and epithermal neutron fluxes at the horizontal beamlines of the Dalat reactor. Materials and Methods: The new design of collimators and neutron filter selections has been made with optimal parameters for alternative applications. For validation of the simulation model s, the values of neutron flux and gamma dose rate were measured and compared with the simulated values. Results: The simulation of the new collimator system shows that for a crystal filter composition of 60 cm Si and 6 cm Bi, the thermal neutron flux at the beam port is 4.0×10sup7/sup n/cmsup2/sup/s. The selection of crystal filters of 20 cm Si and 3 cm Bi is proposed with higher thermal neutron fluxes of 1.74×10sup8/sup n/cmsup2/sup/s, that the thermal neutron component will be improved with a factor of 7.67. Conclusion: A newly designed model of the conical collimator with a filter combination of 20 cm silicon and 3 cm bismuth, in crystal formations, is proposed for the experimental study of the in-phantom boron neutron capture measurements.