A fast neutron from uranium fission that has been slowed down by elastic collision with a moderator such as graphite to energies equivalent to those of gas molecules at room temperature (approximately 0.025 electron volts). The biological effect of thermal neutrons is attributable to the summation of capture and decay radiations. In biological material, the reactions 1H (n, γ) 2H and 14N (n, p) 14C are the most important sources of tissue ionization. The relative importance of these reactions depends on the size of the organism. Protons from nitrogen capture are the major cause of the biological effects of thermal neutrons in an organism the size of Drosophila.
Subjects: Genetics and Genomics.