Neutron spectra re-binning and dose calculation using Monte Carlo methods

Abstract

One hundred thirty lethargy neutron spectra in 60 energy groups were converted to energy spectra and re-binned to 31 energy groups. Original spectra were taken form the compilation published by the IAEA and covers neutron spectra from isotopic neutron sources, nuclear reactors, medical and physical application accelerators, cosmic rays, etc. The 31 energy groups were taken from the BUNKIUT unfolding code, which is utilized to obtain the neutron spectrum from a multisphere neutron spectrometer. Re-binned spectra were utilized to calculate the ambient, personal and effective doses covering 13 types of doses. This calculation was carried out through the ICRP74 dose-to-fluence conversion coefficients. This procedure was performed using Monte Carlo methods using the MCNP 4C code. Two experiments were carried out to obtain, with a Bonner sphere spectrometer, the BUNKIUT code and the UTA4 response matrix, the neutron spectra of 252Cf and 252Cf/D2O. For both sources and at the same locations the equivalent ambient dose were measured using a rem meter. Measured H*(10) and neutron spectra were compared with those obtained in the Monte Carlo calculations.