RBE of 14 MeV Neutrons in Barley

Abstract
The effects of 14 meV neutrons were compared with those of 60Co γ-rays in barley seeds. After irradiation the seeds were germinated on wet filter paper and the lengths of the first leaf and coleoptiles were measured. The results for leaf growth can be fitted to an exponential function down to 20 per cent decrease for both types of irradiation. The mean RBE was found to be 11·0 ± 1·4. Coleoptile growth showed initially an exponential response to gamma and neutron irradiation. The exponential parts gave a mean RBE of 5·1 ± 0·36. Both RBE values (11·0 and 5·1) are calculated from the doses stated as rads in water at the position of the seeds. When the elemental composition of the barley plant is taken into account the RBE values become 14·5 for leaf growth and 6·6 for coleoptile growth.