FLUENCE TO EFFECTIVE DOSE CONVERSION COEFFICIENTS FOR NEUTRONS - A COMPARISON BETWEEN RESULTS OBTAINED BY MCNP AND FLUKA CODES

Conversion coefficients from fluence to effective dose are calculated by radiation transport codes using mathematical models of the adult hu man, the so called anthropomorphic phantoms. A comparison using differ ent codes is always important to discover limits and bugs in the compu tational methods of the codes. Two well-known radiation transport code s, MCNP and FLUKA, have been compared calculating the conversion coeff icients from neutron fluence to effective dose using an identical mode l of an hermaphrodite phantom. Monoenergetic neutrons of energy rangin g from 10 keV to 15 MeV plus Maxwellian distributed 0.025 eV neutrons were used with various irradiation geometries. The agreement is genera lly satisfactory in the energy range 10 keV-10 MeV, although differenc es as large as 20% can be observed for posterior-anterior irradiation. At thermal energy and at 15 MeV discrepancies up to 25% and 15% respe ctively, are found for all the irradiation geometries investigated. Th ese results are discussed and some considerations about the various co ntributions of the radiation involved to the effective dose are expose d.