RBE values for fast neutrons in connection with estimates of the radiation burden in space.

Much data concerning radiation in space as a serious danger to astronauts can be obtained in laboratories on Earth. For different parameters we investigated the relative biological efficiency (RBE) of 14-MeV neutrons on mice, rats and guinea pigs (being wholly exposed). Also the mitosis inhibition for isolated cells was determined. The RBE values found were: for lethality in the LD50(30d)-region--about 2 (for mice, rats and guinea pigs); for reduction due to radiation of living weight of different animals--2 to 3; for reduction of small gut weight of rats and guinea pigs--2.5 and 2; for histological changes in blood and albumin serum (rats and guinea pigs)--about 2; for the highly sensible cells of the lense epithelium from eyes of rabbits--2.5; for the mitosis inhibition of HeLa cells--2.5. The apparatus for radiation tests is described and measuring methods are indicated. The radiation of the whole body of mice, rats and guinea pigs was determined by activating of MgCl2 solution filled into phantoms. By means of a computer, the depth-dose curve can be determined for larger biological objects.