The application of gas-cooled reactor technologies to the transmutation of nuclear waste

Abstract

Nuclear waste from commercial power plants contains large quantities of plutonium, other fissionable actinides, and long-lived fission products that pose long-term safe storage problems. Along with materials from weapons decommissioning programs, they are also a proliferation concern. Based on current levels of global nuclear power generation, it is estimated that by 2015 there will be more than 250,000 tons of spent fuel worldwide. This waste will contain over 2,000 tons of plutonium. (There is also more than 100 tons of plutonium becoming available from disarmament programs.) The disposal of this nuclear waste from commercial and defense programs has become a significant environmental and political issue. Long-term uncertainties are hampering the acceptability of a geologic repository for spent fuel in the U.S. The greatest concerns are with the potential for radiation release and exposure from the waste, and the possible diversion of fissionable material. The development of high-power accelerators has brought up the possibility of a technological solution to the problem. This is the so-called accelerator transmutation of waste (ATW), in which an intense beam of protons is used to produce a large, high-energy neutron flux in a spallation target. The target is surrounded by a multiplying medium of the plutonium and actinide waste, which is destroyed by neutron fission and capture. This paper describes the application of gas-cooled technology to the ATW, which can result in the elimination of weapons-useful material in the waste in one pass, without intermediate reprocessing, along with at least an order of magnitude reduction in the amount of reactor-generated transuranic (TRU) waste. Repository heat loads and the radio-toxicity of the waste are dramatically reduced. The process provides a waste form that is highly resistant to corrosion. It is also passively safe and does not produce mixed waste. The use of gas-cooled nuclear technology also provides maximum flexibility in the transmutation approach, and can allow the use of a direct-cycle gas-turbine generator power conversion system to produce electricity with 47% efficiency. Economic analyses suggest that gas-cooled transmutation systems are economically viable and would attract private investment for deployment.