Ambient Dose Equivalent, Deep Dose Equivalent Index, and ICRU Sphere Depth-Dose Calculations for Neutrons from 30 to 180 MeV

Abstract

Detailed depth-dose calculations were performed in the ICRU sphere for monoenergetic parallel neutron beams with energies ranging from 30 MeV to 180 MeV. Fluence-to-dose conversion coefficients were obtained for both absorbed dose and dose equivalent quantities. Calculations of dose equivalents were performed using both ICRP 21 and ICRP 60 Q-L relationships. Ambient dose equivalents, at a depth of 10mm inside the ICRU sphere, and deep dose equivalent indices are reported. The LAHET computer code was utilised to perform the energy deposition calculations due to secondary charged particles for neutron interactions above 20 MeV. Lower energy neutrons and neutron-induced photons were transported using the HMCNP code and the ENDF/B-V continuous energy cross section data library. The kerma approximation was employed to compute the absorbed doses due to the interactions of neutrons below 20 MeV. The results are compared with the limited available depth-dose data for high energy neutron beams incident on slab phantoms.