The Relative Effectiveness of Neutrons from a Nuclear Detonation and from a Cyclotron in Inducing Dominant Lethals in the Mouse

Abstract

Dominant lethality in the offspring of male mice exposed in lead hemispheres to neutron radiation from a nuclear detonation was determined for ten different doses by mating the males to unexposed females, dissecting the females at a late stage in pregnancy and recording the number of living and dead embryos, resorption sites and corpora lutea. Data from early matings (2 to 6 days after irradiation) and late matings (19 to 31 days after irradiation) were tabulated separately. Comparison of the results with those from a similar experiment with fast neutrons from a cyclotron shows: 1. For comparable levels of total effect, the two sets of results do not differ significantly in the distribution of deaths according to age of embryos. 2. The increase in dominant lethality observed when the offspring of late matings are compared with those of early matings is similar in the two experiments. 3. The biological effectiveness of detonation neutrons relative to cyclotron neutrons lies between 0.80 and 1.18, the minimum and maximum estimates obtained when allowance is made for uncertainty in the physical measurements of the gamma radiation contamination in the detonation experiment. (Taking the biological effectiveness of cyclotron neutrons relative to X-rays as 8.0, the corresponding minimum and maximum estimates of the biological effectiveness of detonation neutrons relative to X-rays are 6.4 and 9.4, respectively.) It may be concluded that, although there is a marked difference in intensity, and presumably some difference in energy spectrum, between the detonation and cyclotron neutrons, the present data show no significant difference in the effectiveness of these neutrons in inducing dominant lethality in mice.