Irradiation analysis of U, Am samples irradiated in experimental fast reactor “Joyo” for protected plutonium production in fast breeder reactor blanket

Americium is a key element to design the FBR based nuclear fuel cycle, because of its long-term high radiological toxicity as well as a resource of even-mass-number plutonium by its transmutation in reactors, which contributes the enhancement of proliferation resistance. The present paper summarizes analysis of the individual Am and U samples irradiation in Joyo to re-evaluate the results of Pu isotopes in the measure of proliferation resistance, and to combine the results for the prediction of DU-Am irradiation especially in the production of Pu isotopes. By the prediction of DU-Am oxide fuel in fast reactor environment with detail fuel irradiation analysis, it was confirmed that neutron moderation and fuel size affects the produced Pu isotope and its vector due to the very high sensitivity of 238U resonance capture reaction, the larger diameter fuel is more preferable in the case of moderated neutron spectrum environment for denaturing Pu in fast reactor blanket. Finally proliferation resistance of all the Pu produced in U, Am sample irradiation and DU-Am fuel irradiation prediction were evaluated based on decay heat and spontaneous fission neutron rate, and it was confirmed 241Am produces un-attractive Pu to abuse from the beginning to the end of irradiation, and more than 2% of 241Am doping is required to enhance the proliferation resistance of Pu to MOX grade and Kessler’s proposal in moderated neutron spectrum environment in fast reactor.

► PIE analysis of individual Am and U sample irradiation in Joyo is summarized.
► Results of Pu isotopes inventory and isotopic vector were re-evaluated.
► Multi-layer fuel pin model were applied to observe the radial Pu isotope distribution in DU-Am fuel.
► Larger-diameter-fuel is more preferable in moderated-neutron for denaturing Pu in FR blanket.
► Isotopic barrier of Pu were evaluated by decay heat and spontaneous fission generation.