Resonance enhancement in the accelerator transmutation of 1.3-day (sup 232)Pa and 2.1-day (sup 238)Np

摘要

The suggestion that the transmutation of actinide waste into fission products might best be done with thermalized spallation neutrons and odd-odd target materials such as (sup 238)Np has been studied. During the 1993 LAMPF/PSR cycle, we measured the fission cross section of 1.3-day (sup 232)Pa and 2.1-day (sup 238)Np from 0.01 eV to 40 keV at the LANSCE facility, and have carried out a preliminary resonance analysis of the observed structure and of the thermal region, with a 1/v representation above a few eV. In the present study, we calculate the reaction rates of these two species and (sup 247)Cm in a ''resonance reactor,'' an accelerator-driven assembly whose slowing-down properties are well known. Our model is a 1.8 m(sup 3)-block of lead with a helium-cooled tungsten target in the center, i.e, the Rensselaer Intense Neutron Source (RINS). We include the effects of adding moderator outside an idealized lead slowing-down assembly, giving resonance enhancement factors for (sup 232)Pa and (sup 238)Np, and present parameters for the accelerator required to drive such an assembly to accomplish actinide burnup of these species.