On the requirements for tokamak reactor fuel purity

In the framework of the problem related to optimization of fuel purification system and ensuring the stationary operation of a tokamak reactor the balance of particls in a reactor chamber is considered. The system of equations for determination of permissible relative concentrations of helium and protium in plasma and supplied fuel is obtained. The conclusion is made that a relatively thorough purification of fuel mixture from helium is required, whereas for the purification from protium the withdrowal of its insignificant portion is sufficient