  Thermonuclear reactors hold a great promise for the future of Humankind.
Within Tokamak and Stellarator reactors, plasma is confined by twisted magnetic
fields. Reactors which produce fusion energy have existed since Princeton Large
Torus Tokamak in 1978, nevertheless in all reactors built up to now, energy
loss from plasma vastly exceeded fusion energy production. In order for a
thermonuclear power plant to run, generated fusion energy must significantly
exceed energy loss by the plasma. There are four processes by which plasma
looses energy -- neutron radiation, Bremsstrahlung radiation, synchrotron
radiation, and heat conduction to the walls. For a deuterium -- tritium
reactor, 80\% of energy produced by fusion is lost to neutron radiation, about
4\% to 6\% of fusion energy is lost to Bremsstrahlung and synchrotron
radiation. For a deuterium -- $^3$He reactor, 5\% of energy produced by fusion
is lost to neutron radiation, about 50\% to 75\% of fusion energy is lost to
Bremsstrahlung and synchrotron radiation. Increasing reactor operating
temperature decreases loss to Bremsstrahlung radiation and increases loss to
synchrotron radiation. Power loss to conduction is either independent or weakly
dependent on fusion power production. Up to now, no single theoretical or
experimental model can accurately predict conduction power loss. For small
Tokamaks and Stellarators, conduction power loss vastly exceeds power generated
by fusion. For large and powerful thermonuclear reactors which are yet to be
built, conduction power loss should be much lower then power produced by
fusion.
