RBE, OER and Dose-rate Effects with 14 MeV Neutrons Relative to 300 kVp X-rays in Barley Roots

Abstract

The effects of 14 MeV neutrons, 300 kVp x-rays, ⁶⁰Co gamma-rays and 10 MeV electrons on the growth of barley roots were investigated. The RBE values for 14 MeV neutrons versus 300 kVp x-rays are: (1) anoxic conditions: 6·01 ± 0·36, (2) oxic conditions: 3·39 ± 0·23 at dose-rates of x-rays higher than 48 rads min⁻¹, and 6·0 ± 0·04 at dose-rates of x-rays from 17 to 5·5 rads min⁻¹. No dose-rate effects were observed for 14 MeV neutrons for the range from 8·5 rads min⁻¹ to 1·5 rads min⁻¹. The RBE of ⁶⁰Co gamma-radiation versus 300 kVp x-rays was 0·79 ± 0·05 and 0·77 ± 0·24 in oxic and anoxic conditions, respectively. The oxygen enhancement ratio (OER) for x-rays is 3·4 ± 0·4, and for 14 MeV neutrons 1·92 ± 0·76, i.e. a gain factor of 1·8 ± 0·2.