GAMMA RAYS O3 1 IO L jl ~ R/WEEK 100 ~~ i 1OO0 A 100 MEAN SURVIVAL TIME (PER CENT OF CONTROL) 100 ' 7 O71 qT I 1O FAST NEUTRONS - T iOO RAD/WEEK Figure XIV. Mean survival time expressed as percentage of the control survival, as a funetton of the weekly dose or exposure to fast neutrons or gamma rays. The ganna and neutron seales are in the ratio of 1:13. The symbols refer to different sets of data obtatned on mice, rats and guinea-pigs by vartous authors, as plotted by Mole [M13] and tneluded in the UNSCEAR 1958 report [U1]. sponse the neutron data were intermediate between the effects of these two in« tensities of gamma rays and nearer to those of the 110 R/week. The RBE was therefore estimated to be between 13 and 7, but nearer to the latter figure. 196, In a subsequent paper by the same group [N8] the RBE value was dis- cussed for CBA mice irradiated chronically with fast neutrons with the neutron facilities described in [N3]. rad/day or 0.3 rad/day. The dose-rates of the 0.7 MeV neutrons were 2.2 Gamma irradiations were run at 15.8 or 2.3 rad/day. Complete life-table data and cumulative survival curves were obtained in repli-