Rbe of 200 Mev Neutron Radiation for the Induction of Chromosomal Abberation in Human Lymphocytes

Abstract

2 Induction of dicentric chromosomes by 192 MeV neutronsR. NolteThe production of dicentric chromosomes in human lymphocytes by high-energy neutron radiation was studied at the neutron beam facility of iThemba Laboratory using a quasimonoenergetic 192 MeV neutron beam. The linear yield coefficient of the linear dose-response relationship for dicentric chromosomes was measured to be (0.096 ± 0.020) Gy -1. This confirms our earlier observations that the yield of dicentric chromosomes decreases with increasing neutron energy above 400 keV and is almost constant above 20 MeV. Using the linear-quadratic dose-response relationship for dicentric chromosomes established in blood of the same donor for 60 Co γ-rays as reference radiation, an average maximum low-dose RBE (RBE M ) of 9 ± 3 for 192MeV quasi-monoenergetic neutrons, with a dose-weighted average energy of 162.1 MeV, was obtained. The yield of chromosome aberrations due to neutrons from the low-energy breakup continuum of the quasi-monoenergetic neutron spectrum was determined by an additional measurement at a neutron emission angle of 16° where the high-energy peak is strongly suppressed. Using this technique, a yield coefficient α = (0.121 ± 0.026) Gy -1 and an RBE M of 12 ± 4 for virtually monoenergtic 192 MeV neutrons was determined. The increased uncertainties result from the application of the (0°-16°) difference method.