External Radiation Conversion Coefficients using Radiation Weighting Factor and Quality Factor for Neutron and Proton from 20MeV to 10GeV

抄録

Conversion coefficients from neutron and proton fluences to effective dose are calculated in the range of incident neutron energy from 20MeV to 10GeV. Two different versions of effective dose are treated, respectively calculated using: (a) the radiation weighting factor w_R, and (b) the Q-L relationship given in ICRP 60. Monte Carlo calculations are performed applying the HETC-3STEP and the MORSE-CG/KFA in the HERMES code system. The calculations are based on a modified MIRD5 anthropomorphic phantom, which is irradiated in anterior-posterior and posterior-anterior directions of beam. For effective dose calculation using the Q-L relationship, a database was compiled and added to the HETC-3STEP, to derive the average quality factor. The effective dose derived using wR proved to overestimate that obtained with the Q-L relationship by about 80% at 10GeV incident neutron energy in the case of conversion from neutron fluence. For proton fluence, the corresponding overestimation reaches a maximum factor of 4.