EXPERIMENTAL AND SIMULATION STUDY OF NEUTRON DOSIMETRY AT VARIOUS NEUTRON ENERGIES

A Monte Carlo Neutron Photon (MCNP) transport code has been employed t o simulate CR-39 plastic track detector as neutron dosimeter at variou s neutron energies. In each simulation a monoenergetic neutron source of a particular energy was embedded in the center of a sphere made of CR-39. Surrounding the source there were concentric shells of 2 mu m C R-39 track detectors. The code, MCNP, was run on personal computer for 7.5x10(6) histories. The number of proton recoils in each shell of 2 mu m of CR-39 were determined. The simulation results show that apart from proton recoils (for E-n > 1.0 MeV), about 50% recoils are due to heavy charged particles i.e. Oxygen and Carbon in CR-39. This indicate s that etched tracks are not only due to recoil of protons but also du e to recoil of heavy charged particles. The upper limits of the track registration efficiencies have been determined as a function of neutro n energies. These simulation results have been experimentally verified using CR-39 track detectors at various known energies of neutrons. Th e proton and heavy charged particle recoil tracks in CR-39 were made v isible by etching in NaOH solution, at 70+/-1 degrees C for 1.75 hours .