One mechanism that is being considered seriously for hydrogen production is thermo-chemical water splitting by the Iodine-Sulfur (IS) process. The IS process was originally proposed by the General Atomic Company in early 1970’s and is very promising because it involves only a few reaction steps. In this process Hydrogen — Iodide (HI) is produced by a cyclic chemical reaction chain utilizing Iodine, sulfur — dioxide and water; HI is then decomposed to produce hydrogen, releasing Iodine to the chemical reaction chain. Sulfuric acid, H2SO4, is generated in the process, which is vaporised and decomposed at a temperature of about 800 to 900 C to sulfur- dioxide, water and oxygen. The oxygen is released and sulfur-dioxide and water is returned to the reaction cycle. Laboratory scale experiments at Japan Atomic Energy Research Institute have demonstrated the feasibility of the IS process with continuous generation of hydrogen from water with recycling of the process material. An energy efficiency of 47% has been achieved in this process16.

B. Electrolysis

Water electrolysis at ambient pressure and temperature of 70 — 90 C is a common method for production of high purity hydrogen. However, it has been found that the demand for electricity decreases with increase of temperature. That is the electric energy required is much reduced for the electrolysis of steam at higher temperatures (800 C and above). High temperature electrolysis is a reverse reaction of the Solid-oxide Fuel Cell, where water is decomposed in the solid polymer electrolyte to hydrogen and oxygen. This method is at an early stage of development14.

Conclusion

There are several possibilities for direct utilization of heat from nuclear reactors. Nuclear desalination, district heating and industrial process heat are examples where this has been done, and these non-electric applications of nuclear power can be expanded in the future. It is also important to note that a wide range of temperatures, for low to high temperature applications, can be tailored for specific uses by different reactor types. Table IX shows the status of projects in several countries for non-electric applications of nuclear energy. The proposed applications are primarily for dual-purpose use but dedicated heating reactors are also being developed in China and Russia. Innovative applications are being explored with gas — cooled reactors because of their high temperatures. High temperature applications of nuclear energy, particularly for production of new fuel such as hydrogen, are in the laboratory stage now but have a great potential for the future3.

Cost-effectiveness is in general a crucial issue for non-electric applications of nuclear power. As nuclear power captures a larger share of the electricity market, the non-electric applications will also flourish. Until now, the non-electric applications are only a very small part of power production. For some applications, however, close proximity of the power plant to a population centre is needed (to reduce energy and/or product transmission losses) and this requires further public acceptance. Some large applications also require the development of infrastructure — heat-distribution networks for district heating and water distribution systems (water pipes and pumps) for fresh water. Many countries are exploring these possibilities of nuclear power. As mentioned in the text, there is a large market for non-electric applications of nuclear energy and it is hoped that someday this potential will be realized.

TABLE IX. PROSPECTIVE NUCLEAR PROJECTS FOR
NON-ELECTRIC APPLICATIONS

E: Electricity (Power), P: Steam supply for process heat, DH: Steam/Hot water supply for heating.