OER of Fission Neutrons for Induction of Heteroallelic Reversion in Diploid Yeast

A sensitive strain of diploid yeast, Saccharomyces cerevisiae BZ 34, was used to study the OER of fission neutrons with the induction of arginine prototrophs as the end point. A Standard Neutron Irradiation Facility (SNIF) which significantly cuts down thermal neutron and ..gamma.. contamination was used for fast neutron irradiation in a swimming pool reactor. For irradiation under hypoxic conditions, a high cell titer, viz 10/sup 8//ml, in a glass-stoppered vial was used which would use up the dissolved oxygen and hence achieve hypoxia. Gamma rays from a /sup 60/Co ..gamma.. cell were used to determine OER for purposes of comparison. The values of OER for fast neutron and ..gamma.. radiation were found to be 1.17 +- 0.19 and 2.42 +- 0.12, respectively. Computations were made with the LET distributions relevant for pile neutrons on the basis of charged particle data and it was found that the computed value of OER 1.68 is larger than the observed value 1.17 +- 0.19. This observation may have application in radiotherapy of malignant tumors.