Keywords: nuclear desalination, seawater desalination, reverse osmosis process (RO), low pressure steam, turbine driven high-pressure pump, fresh water storage bags, light water reator (LWR), pressurised water reactor (PWR), reusable type small PWR, transportation of reactor vessel, independent fuel exchange base, marine reactor
Seawater desalination using reusable type small PWR
Demand for seawater desalination is increasing, especially in regions such as the Middle East and North Africa, where populations are growing at a high annual rate. If such demand is met by fossil fuel energy, the influence on the environment, such as global warming, cannot be disregarded. Since these regions are behind in their preparedness of social capital infrastructure, such as power transfer grids, small reactors are considered to be more suitable for introduction than the large reactors found commonly in developed countries. Therefore, a small reusable PWR with mid-range pressure and temperature services, which does not require on-site refuelling, was devised for seawater desalination. In a small reusable PWR, spent fuel is taken out together with the reactor vessel and refuelled on the exterior fuel exchange base prepared independently. Thus, the safeguards against nuclear proliferation increase at a plant site because the lid of the reactor vessel is never opened at the site, in principle. The reactor vessel will be transported from the plant site to a fuel exchange base under stipulated conditions within a transportation cask after a long (about six years) operation. Since fuel handling facilities at the site become unnecessary through centralisation at a fuel exchange base, initial plant construction costs are reduced. In addition, the reactor vessel is reused until its service life has expired. This examination was based on the marine reactor of the experimental nuclear ship, Mutsu, after it had been applied for land use: at a lowered, midrange pressure and temperature service, in theory. It is possible to produce fresh water through reverse osmosis (RO) membrane pressure–rising seawater by a steam turbine driven pump. Using the method of driving a desalination unit high-pressure pump directly by low-pressure steam generated from the heating reactor, fresh water can be produced efficiently. Furthermore, operating at reduced pressure makes it possible not only to improve the transport performance of the reactor vessel but also to save plant construction costs, thus reducing bill materials of the primary system. There has been a worldwide trend for the RO method to be used for seawater desalination. So the reverse osmosis method was examined using low-pressure steam generated from a small heating reactor and compared with electrical power and evaporation methods (MED or MSF) utilising low-pressure steam towards a sea area with high salt concentration and countries that have been familiar with evaporation methods by fossil fuel energy.