Reactor Vessel

Reactor Design

The core, reactor vessel, and internals of the AP600 are essentially those of a conventional Westinghouse PWR design. Several important features, all based on existing technology, have been used to improve the performance characteristics of the AP600.

The AP600 reactor vessel has incorporated improvements over its predecessors, including ring forgings to eliminate vertical weld seams, location of circumferential welds outside high neutron flux beltline region, and control of chemical composition of vessel material to reduce irradiation damage

Over-sized Reactor Vessel

Although the AP600 reactor has two primary coolant loops, the reactor vessel is similar to the standard 3-loop model. Each primary loop has two cold leg nozzles and one hot leg nozzle, so the standard 3-loop vessel accommodates the AP600 nicely with slight re-orientation of the nozzles. Moreover, the larger reactor vessel on the AP600 accommodates a larger reactor core than that for a traditional two-loop plant. With the larger reactor core and the same power rating, the core power density is reduced which adds safety margin to the plant -- one of the hallmarks of the AP600.

Radial Reflector

The use of a radial neutron reflector contributes to lowering fuel cycle cost and extending reactor life. This reflector, which surrounds the core, reduces neutron leakage, thereby improving core neutron utilization and reducing the damaging neutron fluence on the reactor vessel. The reduced fluence is important in view of the 60-year design objective of the AP600.

Improved Overall Reactor Design

The combination of the radial reflector, the low power density core, and optimized fuel assemblies results in a 20-percent fuel cycle cost savings compared to a standard PWR design of the same power rating. The core design allows 18-month refueling cycles to be achieved with an 85-percent capacity factor (approximately 466 effective full power days per cycle) and requires no burnable absorbers other than for the first cycle of operation.

Reactor Vessel