Heat Rejection
Not all power leaves as electricity: neutron heat, radiated power, and converter losses must be carried away by the machine's thermal systems.
Direct conversion captures the charged-particle stream, but a real machine still makes heat. The 5.44% neutron fraction deposits its energy in the shielding as heat. The plasma radiates power to the first wall. The DEC electrodes, beam dumps, and cryogenic current leads all shed heat. The machine's thermal-management system collects and rejects all of it.
Heat rejection in the burner is smaller than in a thermal reactor of similar fusion power, because most of the power leaves as electricity through the DEC rather than as heat through a boiler. But the heat that remains is real, concentrated in specific places — shielding, wall, electrodes, cryoplant — and must be removed continuously in steady state.
Where the heat comes from
- Neutron energy from the 5.44% fraction, deposited in shielding
- Plasma radiation onto the first wall
- Intercepted-ion and secondary-electron heat at the DEC
- Beam-dump and RF-load heat from the heating systems
- Cryogenic heat leaks removed by the refrigeration plant
- RF-load and power-conditioning losses
Each of these loads has a different temperature and location, so the thermal system is really several loops — a high-temperature loop for the shield and wall, a low-temperature loop for the cryoplant, and intermediate loops for the electrodes and heating dumps — collected toward a common rejection point. Sizing follows the sum of the non-electrical power, which is far smaller here than in a steam plant of similar fusion power.
Signature relevance
Heat rejection is also where the machine's thermal signature is set. For the fixed-installation housing, how and where waste heat is dumped affects how visible the site is. The thermal design is coupled to the low-signature goal: the smaller and better-managed the rejected heat, the lower the installation's thermal footprint. That connection is developed on the thermal-signature page.
All figures are design-and-simulation values for a machine not yet built.