A preliminary design study for the HYPER system

Abstract In order to transmute the long-lived radioactive nuclides such as transuranics (TRU), Tc-99, and I-129 in LWR spent fuel, a preliminary conceptual design study has been performed for an accelerator driven subcritical reactor system, called HYPER (HYbrid Power Extraction Reactor). The core has a hybrid neutron energy spectrum which includes fast and thermal neutrons for the transmutation of TRU and fission products, respectively. TRU are loaded into the HYPER core in a TRU–Zr metal form because a metal type fuel has very good compatibility with the pyro-chemical process which retains the self-protection of transuranics at all times. On the other hand, Tc-99 and I-129 are loaded as pure technetium metal and sodium iodide, respectively. Pb–Bi is chosen as a primary coolant because Pb–Bi can provide a good spallation target and produce a very hard neutron energy spectrum. As results, the HYPER system does not need any independent spallation target system. 9Cr–2WVTa is used as a window material because this advanced ferritic/martensitic steel is known to have a good performance in the highly corrosive and radiative environment. The support ratios of the HYPER system are about 4–5 for TRU, Tc-99, and I-129. Therefore, a radiologically clean nuclear power, i.e. zero net production of TRU, Tc-99 and I-129 can be achieved by combining 4–5 LWRs with one HYPER system. In addition, the HYPER system, having good proliferation resistance and high nuclear waste transmutation capability, is believed to provide a breakthrough to the spent fuel problems the nuclear industry is facing with.