The estimation of human tooth enamel in vivo radiation sensitivity to neutron irradiation

In the present study MCNP4B simulation code was used to simulate the external neutron irradiation of the human adult mathematical model with pre-defined dental region. It gave the conversion coefficients that relate neutron fluence to the dose absorbed in tooth enamel (molars and pre-molars only) for 20 energy groups of monoenergetic neutrons with energies from 10"9 to 20 MeV for AP, PA, LLAT, RLAT and ISO irradiation geometries. The data presented are intended to provide the basis for connection between EPR dose values and standart protection quantities defined in ICRP Publication 74. The results of the calculations for critical organs were found to be consistent with ICRP data, the discrepancies is generally less than 10 % for the fast neutrons. The absorbed dose in enamel was found to depend strongly on the incident neutron energy for neutrons over 10 keV. The dependence of the data on the irradiation geometry was also observed. Lower bound estimates of enamel radiation sensitivity to neutrons were made using obtained coefficients for the secondary photons. Tooth enamel was shown to register at least 10 % of the total dose in human body in case of irradiation with pre-fast neutrons in AP irradiation geometry.