WH PWRs
WH-type PWRs increased the number of steam generators and reactor coolant pumps following the increase in the electrical output (large-scale plant). For 1000 MWe class WH-type PWRs, as shown below, the primary cooling system consists of four loops (four steam generators and four primary coolant pumps). The steam generator of WH-type PWRs is shown in Figure 12. The steam generator is designed as a vertical U-tube recirculating system to generate saturated steam. In such a design, Mitsubishi PWR (Japan), Framatome PWR (France) and Siemens (KWU) PWR (Germany) belong to the WH-type PWR.
The AP600 (600 MWe) is a medium-size reactor adopting a passive-safety design that was developed by WH according to the Advanced Light Water Reactor (ALWR) Program of DOE/EPRI. The reactor is designed to adopt passive cooling (for an example of reactor containment, see Figure 14), and to aim at simplification (reduction of about 50% of valves, about 80% of piping, about 70% of power cables, etc. compared with conventional reactors), modularization, high public safety (no operator action is required for three days after an accidents), easy licensing, and short construction period (three years). As mentioned later, the combination of two steam generators and four primary coolant pumps of the plant is the same configuration as that of the reactor cooling system of B&W-type and CE-type PWRs. The design has been already approved by the U.S. NRC.
Framatome PWR
The N4 reactor (1,516 MWe) is a twin-type standardized APWR developed by Framatome improving the central control room etc. and increasing reliability and economical efficiency with new knowledge obtained from lessons learned from the TMI plant accident (USA, 1979) Chooz-B1 & B2 and Civaux-1 & 2 are already in commercial operation. The EPR (the Europe pressurized water reactor, 1,500 MWe) is a large-sized reactor currently being developed jointly by France (Framatome) and Germany (Siemens), and the preliminary design has been completed. The plant design is based on the N4 and Konvoy (Germany-type PWR) and aims at improvement of safety (for a severe accident etc.), simple operation, competitive economical efficiency (60-year lifetime, high-burnup 70 GWd/t), and MOX fuel (used up to 50% of the fuel).
PWRs of other suppliers
The configuration of the reactor cooling system of CE-type PWRs consists of two loops (two steam generators and four primary coolant pumps) as shown in Figure 15. Namely, the reactor coolant coming out of two steam generators is returned to the reactor vessel with four reactor coolant pumps. The steam generator is almost the same type as one of WH-type PWR, which is a vertical reverse U-tube recirculating system to generate saturated steam (Figure 16). Furthermore, System80+ (1,300 MWe) that is modified from Sytem80 is a next-generation large-sized reactor significantly improved in safety and economical efficiency.
