The OPAL reactor has a primary cooling system that dissipates fission heat by the forced upward circulation of light water.
Primary cooling system
The OPAL reactor has a primary cooling system that dissipates fission heat by the forced upward circulation of light water through the cooling channels.
Its design guarantees the thermal stability of the water intake within a range of operating temperatures, regardless of external meteorological conditions.
The primary cooling system is made up of three identical circuits. Each circuit has a pump and a heat exchanger able to remove 50% of the reactor power. Usually, only two circuits are in operation, and the third one is redundant— that is, a backup.
Cooling system of the reactor and service pools
• Dissipates the facility irradiation heat under normal operating conditions.
• Dissipates the reactor core decay heat and keeps the irradiation facilities always cool when the reactor is switched off.
• Dissipates the spent fuel decay heat.
• Keeps the reactor’s pool water temperature within the limits recommended for all operating conditions.
In order to reduce the radiation dose rate on the surface of the pool, a warm layer of water flows on top through a special circulation and purification system.
Pipes connecting to the reactor tank are above the core level. Mechanisms are provided to avoid the pool emptying by siphon effect.
The primary circuit and the pool circuit have redundant butterfly valves to allow natural circulation.
Reflector’s cooling and purification system
Its function is to ensure circulation, cooling and purification of heavy water, which is used as reflector.
Secondary cooling system
The secondary cooling system removes the heat from the primary cooling circuit, the reactor and the service pool and from the reflector and other facilities so that the heat ultimately evaporates through the cooling towers.
The aim of the water purification and distribution system with mixed bed ion exchange resins is to ensure that the coolant complies with the purity specifications.
The quality of heavy water meets the operating safety standards though another mixed bed resin. Deuterium and oxygen concentrations are kept constant by recombination.