Cooling

The present in-vessel water cooling system (steady state heat removal capability of about 15 MW) is to be 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 will be 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 drainage of this coolant and replacement 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.

No extra purchases are envisaged for the secondary cooling water system as it is expected to be able to handle the increased heat loads.