Transmutation of Neptunium, Americium, Technetium, and Iodine in Fast Spectrum Cores Driven by Accelerated Protons

A neutronic analysis is presented of three incinerator subcritical lattices, driven by accelerated protons and designed to transmute the minor actinides, the ⁹⁹Tc and the ¹²⁹I, of light water reactor (LWR) waste. A calculational methodology must first be established to enable a neutronic burnup analysis of fission cores driven by high-energy protons. The methodology is based on the following codes: HERMES, the Forschungszentrum Jülich adaptation of HETC, for high-energy interactions; MCNP3, for neutron interactions below 20 MeV of neutron energy; and KORIGEN, the Forschungszentrum Karlsruhe adaptation of ORIGEN, for burnup analysis. A result of applying the methodology is that the minor actinides, the ⁹⁹Tc, and the ^I29I, of LWR waste may be transmuted in subcritical cores, driven by the spallation neutrons emanating from the bombardment of the cores with 1600-MeV protons. Three core types are required. Core type I is fueled by the minor actinides and is a modification of the Brookhaven National Laboratory PHOENIX. With a proton current of 20 mA, the core incinerates the minor actinide waste of 14 LWRs. Core type II contains the 99Tc, ^l29I, and plutonium waste of 19 LWRs. With a proton beam of 130 mA, the core incinerates the technetium and 60% of the iodine. With a fraction of the plutonium coming out of this core, the remaining 40% of ¹²⁹I is incinerated in core type III. All three cores run to 100 000 MWd/tonne or slightly higher; on the average, no core is a net consumer of grid electricity; all are cooled by sodium but remain subcritical with the loss of coolant.