Evaluation of Np reaction amount by chemical analysis of Neptunium sample irradiated at experimental fast reactor "JOYO"

Osaka, Masahiko  ; Koyama, Shinichi  ; Mitsugashira, Toshiaki; Morozumi, Katsufumi; Namekawa, Takashi

The chemical analysis technique was established to determine the nuclide generated in Neptunium (Np) sample with a high accuracy, to contribute to evaluation of transmutation characteristics of Np in the fast reactor. (1)Establishment of chemical analysis technique The chemical analysis technique containing determination technique of fission amount of Np, which was consist of Vanadium (V) of capsule material removal and Neodymium (Nd) recovery at high efficiency, was established with optimization of experimental conditions. Four Np saples irradiated in "JOYO" were analyzed using this technique. Results were as follows. (a)Np were determined with high accuracy (relative error was 2.2% at maximum). (b)Errors of fission amount monitoring nuclides Nd were half less than that of Cs. (c)Small amount of Pu was able to determined. (2)Evaluation of Np reaction amount The reaction amount of capture, fission and (n,2n) reactions were evaluated using analyzed values. Transmutation characteristics of Np were evaluated using reaction amount. Evaluated results were as follows. (a)The ratio of capture or fission amount to unirradiated Np amount were 6.125.5 at%, 0.73.6 at%, respectively. (b)The Np (n,2n) Np reaction amount was 7.010 times of Np amount at maximum. (c)The dependences of Np reaction amount to neutron energy spectrum were revealed from the fact such as linearity of fission to capture reaction amount ratio against fast neutron ratio in same fuel assembly.