Nuclear fusion reactor

How a nuclear fusion reactor works

Modern nuclear reactors based on nuclear fission to generate power. In nuclear fission, the U-235 atom splits apart with the help of high-energy neutrons to releases a high amount of energy radioactive wastes. Inversely in a nuclear fusion reactor, two hydrogen atoms combined to form another atom result in a release of a large amount of energy. The same type of nuclear fusion powers our sun. The amount of energy produced by nuclear fusion is 4 times in comparison to energy produced by nuclear fission for the same amount of fuel. The fusion process requires temperatures of about 100 million Kelvin. Due to Sun’s massive gravitational force, and extreme pressure the gaseous Hydrogen converts to hot plasma.

How nuclear fusion reactor works
  • In Nuclear fusion, two Hydrogen atoms fuse together to form helium atoms and release neutrons and a high amount of energy.
  • Hydrogen is super-heated so that it gets converts from gas to plasma in which negatively charged electrons get separated from positively charged nuclei.
  • In such high-temperature nuclei overcome the strong repulsive (electrostatic) force and ions fuse together to release a massive amount of energy.
  • In normal condition, strong electrostatic force prevents nuclei to combine and form another element.
Types of Nuclear fusion reaction:

Proton-proton reaction: In this pair of protons fuse together to form two deuterium atoms. The deuterium atom then combines with a proton to form a Helium-3 atom. Two helium-3 atoms combine to form beryllium-6, which is unstable.
So it decays into two Helium-4 atoms results in the release of high energy and radiation.
Deuterium-deuterium reaction: In this two deuterium atoms fuse together to form a Helium-3 atom and neutron.
Deuterium-tritium: In this, an atom of deuterium combines with another atom of tritium to form a Helium-4 atom and releases energy in the form of the neutron.

  • With the current technology we have, only Deuterium (D) and tritium (T) reactions are possible. When a D-T pair combine it forms a new element of Helium-4 and releases energy in the form of a high-energy proton.
  • A pair of D-T fusion reaction releases about 17.6 MeV in comparison to 3.4 MeV for a U-235 reaction.
  • The high-energy proton will then absorbed with a Lithium blanket that surrounds the nuclear core
  • The lithium blanket absorbs the kinetic energy of protons which helps it to heat up.
  • The heat energy is used to convert water into steam which rotates the turbine and produces electricity.

Currently, scientists are working on D-T reactions but in the future, they will try to work on D (Deuterium)-D(Deuterium) reactions. The reason is that Deuterium can be easily extracted from seawater instead of extracting tritium from lithium. The other reason is that the D-D fusion reaction generates more power than D-T fusion.

Method to achieve high temperature for Hydrogen fusion

Magnetic Confinement

It uses a magnetic and electric field to heat and squeeze Hydrogen plasma
In a magnetic confinement fusion (MFC), hundreds of cubic meters of D-T plasma at a density of less than a milligram per cubic meter are confined by a magnetic field at a few atmospheres pressure and heated to fusion temperature.

Magnetic Confinement

Magnetic fields are used to confine the plasma because of the electrical charges on the separated ions and electrons. The aim is to stop them from coming near the wall as this will dissipate their heat and slow them down.