[en] The helium removal and exhaust in ITER tokamak are discussed. The possibility of the enhancement of the radiation of light impurities is investigated. A model for the calculation of radiation power from the ITER divertor is proposed. The results show that in the non corona model a fraction of the power entering into the ITER divertor region can be reradiated in the case of carbon divertor plates. The time relaxation mode of the ITER divertor region operation can be calculated for Be-seeded and C-seeded plasmas

[en] Results of calculating the vertical plasma instability development in a tokamak reactor with an oblong plasma filament cross section are presented. It is suggested to realize the passive instability stabilization by means of a screen consisting of the reactor first wall and the blanket lithium layer located between the first wall and the uranium layer. This permits to exclude additional aluminium turns of the passive stabilization which complicate the structure of the first wall and reduce the neutron flux into the blanket. A conclusion is drawn that the structure of the first wall and the blanket with the effective electric conductivity σ=(2 to 1)x10⁴ Ω^-1 decreases the vertical instability development increment to the value γ=30 to 60 s^-1. This permits to exclude additional elements of the passive feedback. However, the active feedback system shoeld ensure a fast-response of 30 to 15 ms

No abstract available

[en] The parameters of a tokamak reactor using D³He fuel are optimized by means of a one-dimensional steady-state model of the power balance for ITER scaling. The effect of the density profiles and plasma temperatures, aspect ratio, elongation of the cross section and magnitude of the magnetic field on the reactor parameters is studied. A set of plasma parameters is determined for an experimental reactor on the basis of generally accepted engineering constraints for large tokamaks. 6 refs., 10 figs

[en] The possible use of low Z materials for the ITER divertor plates is discussed. A non coronal radiation model has been developed which indicates that strong enhancement in the radiated power from the divertor may take place when finite confinement is considered. For carbon this leads to stable operating regimes at low electron temperature. It is shown that relaxation oscillations in the dynamical behaviour of impurity density and electron temperature are possible, and can lead to a large decrease in the gross erosion rate of the divertor plates both for carbon and beryllium. (orig.)

[en] Optimization of parameters of a tokamak reactor with D³He fuel is performed within the framework of one-dimensional steady-state model of power balance for ITER scalings. Effect of density profiles and plasma temperature, aspect ratio, cross section stretching and magnetic field value on reactor parameters is investigated. A set of plasma parameters for experimental reactor is defined within the framework of general engineering restrictions for large tokamaks

[en] Calculations on the ideal MHD stability of the plasma in a tokamak with a small aspect ratio and an elongated cross section are discussed. The necessary condition for the stability of the n = 1 external mode, n = 1;q/sub s/≥2 (q>1), for these configurations is replaced by more stringent condition q/sub s/≥q/sub s//sup */>2. If the latter condition is violated, even a force-free equilibrium will be unstable. At q/sub s/>q/sub s//sup */, the limiting value of β for all ideal modes is close to the limiting value for small-scale ballooning modes

[en] Analytical model to control fusion burning in tokamak using fueling is developed and studied. Model is based on two traditional differential equations of particle and energy balance, control of thermonuclear power is conducted using proportional feedback between plasma density and thermal energy characterized by β parameters. Range of control parameters providing for stationary fusion burning along low-temperature brand of ignition curve is determined. Comparison of predictions of analytical model with calculations of burning stabilization is conducted according to QUET sesquidimensional transport code. Good conformity between analytical estimations and calculation results is shown

[en] A brief review and systematization of the D-T fusion burn control techniques in the fusion tokamak-reactor plasma are given in the paper. Passive stabilization techniques and the methods of active control over the overheating instability are discussed. The active control methods related to a cold, time-profiled fueling of the reactor by injection of solid fuel pellets into the plasma column core are considered in detail. A possibility of the overheating instability self-stabilization due to a displacement of the magnetic surfaces out of the torus at rather high plasma pressures is analyzed. (author). 6 refs, 6 figs

[en] To obtain an optimal mode of tokamak reactor fuelling, a 1.5-D computational code was used which includes the 2-D Grad-Shafranov equilibrium equation and 1-D particle and thermal energy balance equations averaged over magnetic surfaces. It is shown that the combination of regulated fuelling with short term, low power auxiliary heating seems to be the optimal technique for burn control. Two aspects of helium pumping are considered: thermalization of fast α-particles - the product of fusion reactions - and their diffusion towards the divertor layer; and diffusion and pumping of α-particles within the divertor layer. On the basis of kinetic equation analysis from the viewpoint of anomalous diffusion effects on α-particle confinement it is shown that, under reasonable assumptions about the anomalous diffusion coefficient, α-particle losses amount to 10% (associated energy losses being 5%) for the OTR device. On the basis of numerical calculations using a 2-D divertor plasma code it is shown that the onset of self-sustained oscillations in the divertor could significantly alleviate helium exhaust from a tokamak reactor, reducing the pumping rate by two orders of magnitude. (author). 6 refs, 4 figs