PRODUCTION OF RADIOISOTOPES IN HIGH SPECIFIC ACTIVITY WITH FAST NEUTRONS IN NUCLEAR REACTOR

Fast neutron fluxes and their distributions in reactors were measured. On the basis of the measurements, the production of several radioisotopes was tried with fast neutron reactions (n,p) and (n, alpha ) and the effect of the irradiation on the amount of a radioisotope produced was investigated. The fast neutron flux was measured using several threshold reactions, such as Al/sup 27/(n alpha )Na/sup 24/, i/sup 31/ and Ni/sup 58/(n,p)Co/sup 58/. The maximum equivalent fission neutron flux of (1.1 to 1.6) x 10/sup 12/ n/cm/sup 2//sec at an output of 40 kw and that of (2.3 to 3.5) x 10/sup 10/ n/cm/sup 2/ /sec at an output of 10 kw were obtained. Distribution and distortion of neutron spectrum in the reactors from true fission neutron spectrum are discussed, considering the results of flux measurements in the light of reactions that have different effective energy. Many (n,p) and (n, alpha ) reactions were taken into account to prepare radioisotopes in high specific activity. Among them (n,p) reactions on S, Cl, Zn, Mg, and Ni and (n, alpha ) reactions on Cl and Al were investigated to prepare P/sup 32/, S/sup 35/, Cu/sup 64/, Na/sup 24/, Co/sup 58/, P/sup 32/, and Na/sup 24/,more » respectively. Yie lds of radioisotopes by these reactions and their specific activities were proved to be sufficient for practical use. The effect of irradiation positions on the reaction yield was also investigated. The effect was quite clear, especially in the case of a reaction having a larger E/ sub eff/ such as Cl/sup 35/(n, alpha )P/sup 32/. The (n,p) reaction has the feature of producing a radioisotope, Cu/sup 67/, which cannot be produced by the (n, gamma ) reaction. This is also discussed briefly. (P.C.H.)« less