Proliferation Resistance of Americium Originating from Spent Irradiated Reactor Fuel of Pressurized Water Reactors, Fast Reactors, and Accelerator-Driven Systems with Different Fuel Cycle Options

摘要

The three most important americium isotopes, ~(241)Am, ~(242m)Am, and ~(243)Am originate in the nuclear fuel of pressurized water reactors (PWRs), fast reactors (FRs), or accelerator-driven systems (ADSs) in a ratio of ~(241)Am/~(243)Am between ～0.45/0.55 to ～0.85/0.15. The content of ~(242m)Am in the spent fuel of PWRs, FRs, and ADSs is relatively small and varies between 0.08 and 4.5%. Only by dedicated breeding in ~(241)Am fuel and blanket assemblies could this ~(242m)Am content be increased to ～7%. Only the isotope ~(241)Am has a relatively high alpha-particle heat production whereas the isotopes ~(242m)Am and ~(243)Am have a relatively small alpha-particle heat production. All three americium isotopes are spontaneous fission neutron emitters. In this paper the different isotopic compositions of the three americium isotopes, ~(241)Am, ~(242m)Am, and ~(243)Am are assembled for a number of fuel cycle strategies for PWRs, FRs and ADSs. Then, the critical masses, spontaneous fission neutron sources, and alpha-particle heat power of these different americium compositions are calculated. In a preignition analysis for gun systems and implosion systems, it is shown that only the implosion system would be applicable to the considered americium isotopic compositions. A subsequent thermal analysis with assumptions for the geometry and choice of materials of so-called hypothetical nuclear explosive devices (HNEDs) shows that the high alpha-particle heat power in the fissile reactor americium part would lead to such high temperatures that the surrounding chemical high explosives would melt and self-explode, and the americium metal would melt. Such HNEDs on the basis of reactor americium as fissile material would be technically unfeasible.