Auxiliary Plant – Cooling
The JT-60U in-vessel water cooling system (steady state heat removal capability of about 15 MW) has being upgraded to handle the maximum plasma heating power in JT60-SA of ~41 MW for 100 s, with the provision of a large water tank as well as new pumps. The water storage tank has been installed on the underground floor of the JT-60 torus building.
The cooling of the vessel is carried out by a borated water coolant to provide maximum neutron shielding. Baking of the vessel is accomplished by draining this coolant and replacing it by a flow of heated nitrogen. In-vessel component baking is accomplished through radiation and conduction during vessel baking.
A secondary water cooling system serves all primary cooling circuits of heat sources throughout the plant, including the vessel, magnets, heating and diagnostic systems, and all peripheral major heat sources that are not cooled by the building HVAC systems.
The system consists of a succession of heat exchangers and a pumped circulation system. Wet cooling towers exchange heat with the atmosphere.
For JT-60SA operation the secondary water cooling system has been modified and replaced. The base frame of the cooling tower, and the cooling tower connection to the base frame, has been modified, and the water treatment equipment to maintain the water quality, and the 12 pumps, has been replaced.