Page 34 - Fundamentals of Magnetic Thermonuclear Reactor Design

Facilities With Magnetic Plasma Confinement Chapter | 2 17

Not all the technical ideas embedded in the projects have stood the test of
time. In hindsight, GTRT parameters, such as the additional heating power and
the plasma elongation, were grossly over-estimated, and τ scaling for the T-20
E
tokamak proved to be over-optimistic (today, an H-mode scaling produces a 4×
lower value). The same is true for the OTR machine: the energy confinement
time should be 1.9 s instead of the 3.7 s accepted by the machine designers.
The GTRT developers placed high emphasis on material R&D and the
physical and technical ideology for hybrid reactors. All these problems are still
pending solution.
The parameters of the purely fusion DEMO tokamak reactors designed in
Russia [11] and the European Union (see Refs [7,12]) are given in Table 2.3.
One can see that a transition from ITER to DEMO requires increases in the
plasma elongation, plasma density and toroidal beta value, as well as a consider-
2
ably greater neutron first wall load (up to ∼2.5 MW/m ).
As a result, the thermonuclear power can be increased to ∼2.5 GW. The
DEMO reactor’s standard operating mode is the stationary mode with a trend
towards a fully non-inductive current drive. Both projects utilise superconduct-
ing magnetic systems.

TABLE 2.3 Parameters of DEMO Reactor Tokamaks
Parameter DEMO-S PPCS-D
Plasma major radius (m) 7.8 6.1
Plasma minor radius (m) 1.5 2.03
Aspect ratio 5.2 3.0
Elongation of plasma cross-section 1.85 1.9
Toroidal magnetic field on plasma 7.7 5.6
axis (T)
Plasma current (MA) 11.2 14.1
Stability margin 3.0 3.8
Plasma toroidal beta (%) 2.8 4.0
Plasma energy confinement time (s) 2.1 (H y,2 = 0.6) 5.8 (H y,2 = 1.2)
Average plasma temperature (keV) 20 12
20
−3
Average D-T ion density (10 m ) 1.5 1.4
Thermonuclear power (MW) ∼2500 ∼2400
Electric power (gross) (MW) 860 1500
Plasma additional heating power 120 70
(MW)
−2
Neutron first wall load (MW·m ) 2.5 2.4
Burn time (s) Steady state Steady state