The Relative Biological Effectiveness of Fast Neutrons, X-Rays, and γ-Rays for Acute Lethality in Mice

Abstract
Young adult female RF mice were exposed to single doses of Co60 gamma rays, 250 kvp X-rays (HVL 0.55 ml Cu), or cyclotron fast neutrons (mean effective energy 1-2 Mev). The LD50/30 days was observed to be 730 rep for gamma rays, 528 rep for X-rays, and 362 rep for fast neutrons. If the relative biological effectiveness of gamma rays is assumed to be 1, then that of X-rays is 1.4 and that of fast neutrons 2 for LD50/30 days.