Effects of Thermal Neutrons on Living Cells III. Estimation of Absorbed Dose in Amoeba Irradiated by Thermal Neutrons

An absorbed dose in amoeba irradiated by thermal neutrons was estimated. Nuclear events following to thermal neutron capture were divided into 6 parts. More than 99% of absorbed dose was estimated to be due to capture γ-rays. Absorbed dose due to recoil nucleus following to the emission of capture γ-rays and that due to β- or γ-rays emitted at the nuclear disintegration of newly formed radioactive nuclides were about 1/1000 of that of capture γ-rays. Anyhow, the absorbed dose obtained by these calculation is too small to explain the lethal effects of thermal neutrons on amoeba. Therefore another processes than energy absorption, namely, transmutation effects due to thermal neutron capture and nuclear disintegration must be taken into account. Especially, the bond rupture on thermal neutron-irradiated DNA, caused by the nuclear reaction 31P(n, γ)32P, would play a very important role in cell killing of amoebae.