Power Engineering Neutron Yield from the Plasma of the Tokamak with Neutral Beam Injection

In modern tokamaks plasma parameters have reached a level that corresponds to the power gain Q ~ 1 in a fusion reactor. Thermonuclear devices with Q ~ 1 can be used as neutron sources for hybrid fusion–fission reactors with subcritical blanket. In such reactors thermonuclear neutrons cause fission fertile nuclides, resulting in production of fissile isotopes and energy. The work considers the plasma–beam mode of fusion neutrons generation for the tokamak conditions. It is implemented with a powerful heating by neutral beam of fast atoms. In these modes, the ratio Q of thermonuclear power to the power injection heating is the order of unity. It is enough for fusion neutron source for hybrid fusion–fission reactor. The reaction rate for fast particles substantially exceeds the rate of reaction in a Maxwellian plasma. So, in such regime, the requirement for the size of the magnetic trap is reduced. The reaction rate was calculated using the approximation of “shifted” Maxwellian velocity distribution function of fast particles. To justify the evaluations a special analysis was conducted to define influence of density and temperature profiles on the value of Q under the conditions close to the International Thermonuclear Experimental Reactor (ITER) operation mode. Using spatial zero-dimensional approach does not lead to an overestimation of the power gain factor Q. The relaxation time of the beam in a neutron source is much greater than the plasma energy confinement time. A possibility to realize the fast fusion neutron source with Q = 1 is shown for today’s scale tokamaks. Estimated parameters of such a source are close to the parameters of existing experimental devices for magnetic plasma confinement