The Coupling of Nuclear Heat and Hydrogen Production Thermochemical Cycles

The technology to use nuclear heat to thermally split water into hydrogen and oxygen attracts more and more attentions at present. This paper discusses some challenges to couple nuclear heat with thermochemical hydrogen production cycles. The challenges include matching the maximum heat grade of thermal chemical cycles and nuclear reactors, and extracting heat from nuclear reactors. Sulfur-iodine and copper-chlorine cycles are taken as typical examples for analysis and discussion. The heat grade and quantity required by each step of the cycles are discussed. The maximum heat grade of sulfur-iodine cycle is higher than 800°C which cannot be easily coupled by GenIV nuclear reactor and other sources of heat must be provided. In comparison, the maximum heat grade of copper-chlorine cycle is 530°C which can be coupled by more nuclear reactors such as advance Gen-III and future Gen-IV nuclear reactor. It is concluded that thermochemical cycles with lower temperature requirement are easier to couple with present and future generations of reactors. Low temperature thermochemical cycles such as copper-chlorine cycles are recommended to match the heat grade of most nuclear reactors. Some methods are proposed to couple heat between a thermochemical cycle and nuclear power generating station. Several heat extraction methods such as using working fluid of nuclear reactor to provide heat to thermochemical cycles are proposed in this paper.