12.2.1.1 SCWR (Gen IV). The Generation IV supercritical water cooled system is a thermal reactor aimed at electricity production as the primary option (Figure 12.1).

Pump

Figure 12.1. Supercritical water reactor. Source: NEA Annual Report (2002).

The option is, however, retained of converting the core design to a fast spectrum to enable actinide recycle.

The reference plant has 1700 MWe power at an operating pressure of 25 MPa above the thermodynamic critical pressure of water. The outlet temperature has a reference level of 510°C but this could range up to 550°C. The system has a high efficiency of 44% (The US Generation IV Implementation Strategy, 2003). This results in good economics, further enhanced via a simplified plant design. However, due to its corrosive high-temperature water environment, the SCWR requires significant materials development. Further developments are also required to address a number of operational safety issues.

12.2.1.2 SCLWR. The study (Squarer et al., 2001) takes the University of Tokyo’s Super Critical Light Water Reactor (SCLWR) as one of the most likely economically competitive of the proposed designs. It can also be designed as a fast reactor that could be fuelled with MOX fuel of around 12% enrichment.

The high-performance LWR size scales considered by Japan (Squarer et al., 2001) are based on the following parameters for core and fuel design, reactor pressure vessel, containment, turbine and balance of plant. The scale is that of a large 1000 MWe power output, at 25 MPa pressure and 500°C outlet temperature. It has 4.2 m active core height, 121 fuel assemblies with 8 mm OD fuel pins, and control rods inserted from the top, 3.380 m RPV ID and 27.5 MPa design pressure, a cylindrical containment with a turbine frequency of 50 cycles s_1. It can be seen that this design is consistent with the Generation IV reference design.

12.2.1.3 B-500 SKDI. The B-500 SKDI design from Russia (Silin et al., 1993) is based on a natural circulation, integrated supercritical pressurised water reactor system, at a smaller scale and power; reference power is 515 MWe.