BARRIER FOR ULTRA-HOT PLASMA IN A FUSION REACTORMark Jordan Robert Turin Nuclear Fusion Nuclear Fission Fossil Fuels Solar & Wind Sustainable?Uses sea water as fuel Uses highly radioactive uranium Uses unrenewable resources Harnesses solar and wind as energy Safe?Nonradioactive, shuts itself down in event of failure Has potential to be a nuclear bomb in event of failure Greenhouse gasses Safe Reliant on location? Available anywhere Can only be used in certain areas under certain conditions Fusion in the Reactor Nuclear fusion is the process by which atom nuclei fuse together to form heavier nuclei. The fusion reaction in the ITER uses two specific isotopes of hydrogen. Deuterium is a hydrogen atom that has one neutron, while tritium is a hydrogen atom with two neutrons. When these atoms combine, they create a helium atom, a free, energetic neutron, and a large amount of energy. In a reactor, the free neutron would then combine with lithium in order to create another helium atom and a tritium atom, the latter of which would be needed for the reaction to repeat. The mass of the helium atom and the neutron is slightly less than that of the two hydrogen atoms. This is because some of that mass converts into energy as described by Albert Einstein’s famous formula E=mc2. Because the transformation of mass into energy has such a high conversion constant, the speed of light squared, even a small amount of mass creates an enormous amount of energy. The reactor is shown in the figure below. Fuel Source The reactants required for a nuclear fusion reaction to be continuous in the ITER are deuterium, tritium, lithium, and beryllium. Although there is a finite amount of all of these on Earth, their abundance or ability to be created make them almost infinite sources. Deuterium is abundant in oceans and can be found in concentrations of 0.014–0.015% of natural hydrogen compounds. Tritium, on the other hand, does not exist naturally on Earth. However, it can be created through the reaction of lithium and an energetic neutron. After tritium’s initial production, the blanket produces the necessary amount of tritium. So, very little amounts of tritium are needed and only when sparking the reaction. With lithium being abundant in seawater, there is essentially a limitless supply. In the ocean alone, there is 230 billion tons of lithium. Beryllium is a much less common element than lithium. However because such a small amount is needed, its relative abundance is negligible. This means nuclear fusion will have a steady fuel supply from the oceans for millions of years to come MeV, with 4.8 MeV of energy. This process also helps shield from radiation by catching the energetic neutrons before they exit the reactor. Beryllium Wall The beryllium tiles provide an extra source of neutrons through a neutron-beryllium reaction. The neutron-beryllium reaction appears as: 9 Be + n  2n He This shows that many of the neutrons that pass through the beryllium tiles double in number before they reach the lithium tiles. In doing so, enough neutrons are generated to replace those lost in the tokamak. Lithium Wall Because tritium and deuterium are constantly used up by the tokamak, there must be a steady supply of both isotopes to continue the reaction. However, the outside source of fuel supplies solely deuterium. Therefore, there must be an internal source of tritium that produces at an equivalent rate as the injection of deuterium. Scientists have designed the fueling system to inject deuterium at the same rate at which the deuterium-tritium reaction occurs. The blanket’s ability to produce tritium occurs when the neutrons from the deuterium- tritium reaction collide with the lithium portion of the blanket. As shown in the figure to the right, a neutron reacts with a lithium atom to give one helium and one tritium atom. This exothermic reaction contributes substantially to the energy of the deuterium-tritium reaction,