Where is the thermonuclear energy?


Nuclear fusion power should be much chipper an safer than that from uranium-plutonium fission. The fuel for the fission not only needs expensive mining but also enrichment by a fissile uranium isotope. Conversely, the fusion fuel, deuterium is readily extracted from the the ocean water. To get fusion, one have to heat the fuel up to about a hundred million degrees to provide the atoms’ kinetic energy high enough to overcome the Coulomb repulsion of nuclei and let them get close enough to fuse. To keep such a temperature for about a second, the plasma can not be confined by nothing but magnetic field. A straightforward idea to manage that is to enclose plasma into a torus surrounded by coils creating an appropriate magnetic field so that charged particles move in circles along magnetic lines far enough from the torus’ walls. In addition, we make a million amps electric current inside the plasma which results in the pinch-effect, that is squeezing the plasma into a cord to additionally separate the plasma from walls. Soon after the first thermonuclear bomb explosion (1952), the corresponding apparatuses were built in both USA and USSR and named Stellarator and Tokamac respectively. Until now they don’t perform well enough due to plasma’s unstable behavior. Instead confining the hot plasma for a long time, one can make it dense, which results in an intensive fusion as well. The practical approach here is to hit a tiny capsule of frozen deuterium-tritium mixture by laser beams squeezing it for nanoseconds. Though the heated this way plasma naturally expands, this happens not that fast and nuclei have time enough to fuse. Even a better way is to put the capsule in a uranium cavity and then evaporate the cavity with laser beams. The resulting intensive gamma radiation squeezes the capsule much more uniformly which prevent the plasma leak out there.

The principle of Tokamak thermonuclear energy

The fusion energy is released as the kinetic energy of neutrons and charged nuclei. Neutrons escape the confined plasma so the simplest way to capture the fusion energy is to surround the reactor by a blanket of lithium converting neutrons’ energy to heat and additionally producing tritium for the fuel.


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