17.7.1 Water Reactors

Light water reactors are the most widely used type of reactor in service at the present time and much work is taking place in optimising the performance and safety of advanced evolutionary designs. A similar approach is being adopted in the development of evolutionary heavy water reactors The emphasis has been to improve the operating economics and also to simplify design to reduce construction costs.

Recent focus has been on large power generation (1300-1500 MWe) but smaller and medium-sized plants are in consideration. There is an increased tendency to introduce more passive systems but some passive safety systems are less appropriate for large power generation.

More innovative types of water reactors are being considered within the first phase of the Generation IV programme (Gen IV-A) (Sinco, 2003). The supercritical water-cooled reactor (SCWR) is a high-temperature super-critical pressure reactor that could be developed from present water reactor technology (Overview of Generation IV Roadmap). It would be primarily for electricity generation. However, there are two core design options, offering an open fuel cycle with a thermal spectrum or a closed fuel cycle with a fast spectrum to enable actinide management. The projected time for commercial deployment of the thermal spectrum option is around 2020-2030. Table 17.3 shows approximate timescales for the different advanced nuclear reactor technologies.