Study of a tandem fuel cycle between a Brazilian PWR (Angra-I) and an Argentinian CANDU (Embalse)

The introduction of advanced fuel cycles in commercial reactors provides a better utilization of natural resources, increases the efficiency and contributes to reduce the amount of wastes to be disposed. On face of the nuclear programs of Brazil and Argentina, the TANDEM cycle could be considered a convenient way to integrate both fuel cycles, achieving some of the mentioned advantages. This paper describes a first study of this synergistic fuel cycle, between the Brazilian PWR (Angra-I) and the Argentinean CANDU reactor (Embalse). Calculations of several parameters of the cycle were performed, as determination of the compositions of the PWRʹs spent fuel for different cooling times, optimum blending ratio considering that the fuel will be diluted with natural uranium, extraction bum-up for the CANDU with MOX fuel, mass flows in the bi-national system, multiplication factors for the new fuel, and estimations of the fuel cycle costs. The study shows that, if the main goal is to minimize the bi-national uranium consumption, the ideal blending for the fuel is 38% of natural uranium in heavy metal (U and Pu), which comes from coprocessed spent fuel of the PWR, considering one year of cooling time. Using this blending ratio, the extraction bum-up of the CANDU is increased up to 22,500 MWDlton U, giving an economy of 84 ton U/year, nearly 50% for the bi-national system. The fuel cycle cost did not show significant variations compared with the natural uranium fuel cycle. Finally, a calculation of the ingestion toxicity was made for the TANDEM cycle and compared with the isolated reactor cycles, showing a reduction of at least 20% during a one million years period