CARCINOGENIC EFFECTS OF EXPOSURE OF RATS TO LOW-DOSES OF FISSION NEUTRONS DELIVERED AT LOW-DOSE RATE

In this experiment we compared the efficiency of fission neutrons of c alifornium 252 at doses of 25 or 53 mGy in function of the dose rate. Two groups of male Sprague-Dawley rats were exposed at 100 or 420 days of age to fission neutrons with dose rates of 950 or 760 mu Gy/h for 26 or 33 h, and 2 other groups were irradiated over a year from 3 mont hs to 15 months of age with dose rates of 3.58 or 7.72 mu Gy/h. The 4 groups of animal were compared with a control group of 501 rats. The r eduction of effectiveness on cancer induction that we have previously shown at low dose rate with rats exposed to gamma rays or to alpha par ticles was not observed for low dose rate exposure with fission neutro ns.