To have a net gain in reactor output thermal power, the total thermal output of the reactor must be more than the power required to maintain the fusion plasdma. From a physical point of view, the total thermal power from a nuclear fusion reactor includes neutrons with an energy of 14.1Mev. That pass through the plasma, braking radiation that escapes from the plasma environment and is absorbed by the primary wall and the continuous transfer of plasma energy to the primary wall by thermal conduction. To prevent the primary wall from melting, the heat is transferred by the coolant and turns into steam. The heat output from the reactor is in the from of radiation and heat conduction. For a fusion reactor with a capacity of 1000MW and an engineering profit factor =10 whose efficiency is ⋍0.5 , The maximum microwave power that can be absorbed in the plasma for external heating and creating torus current will be 50MW.

Power balance plasma neutron factor heat capacity primary wall spontaneous ignition.