RBE OF D(50)-BE NEUTRONS FOR INDUCTION OF CHROMOSOME-ABERRATIONS IN ALLIUM-CEPA ONION ROOTS

Abstract

RBE[relative biological effectiveness]/absorbed dose relationship of d(50)-Be neutrons was determined for the induction of chromosome aberrations in A. cepa onion roots. Neutrons are produced at the cyclotron Cyclone by bombarding a thick Be target with 50 MeV deuterons. Two biological criteria were selected: mean number of aberrations (mainly breaks) per cell in anaphase and telophase and fraction of intact cells in anaphase and telophase. For the 2 criteria, RBE increases continuously from about 7-12 as the neutron absorbed dose decreases from 0.4-0.1 Gy [gray]. RBE values for the 1st criterion are slightly higher than for the 2nd one. The analysis of the distribution of the aberrations in the cells was investigated. In logarithmic coordinates, RBE/absorbed dose relationships for the 2 criteria are almost linear with a slope close to -1/2. RBE values observed for induction of chromosome aberrations in A. cepa are generally higher than for biological effects related to mammalian cell lethality.