The tritium breeding blanket (also known as a fusion blanket, lithium blanket or simply blanket), is a key part of many proposed
fusion reactor
Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices de ...
designs. It serves several purposes; one is to act as a cooling mechanism, absorbing the energy from the
neutron
The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beha ...
s produced within the
plasma by the
nuclear fusion
Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons or protons). The difference in mass between the reactants and products is manife ...
reaction between
deuterium
Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1). The nucleus of a deuterium atom, called a deuteron, contains one proton and one ...
and
tritium
Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus o ...
(D-T), another is to "breed" further tritium fuel, that would otherwise be difficult to obtain in sufficient quantities, through the reaction of neutrons with
lithium
Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid e ...
in the blanket. The breeder blanket further serves as shielding, preventing the high-energy neutrons from escaping to the area outside the reactor and protecting the more radiation-susceptible portions, such as ohmic or
superconducting
Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike ...
magnets, from damage.
Of these three duties, it is only the breeding portion that cannot be replaced by other means. For instance, a large quantity of water makes an excellent cooling system and neutron shield, as in the case of a conventional
nuclear reactor
A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat from n ...
. However, tritium is difficult to obtain in sufficient quantity to run a reactor through other means, so if commercial fusion using the D-T cycle is to be achieved, successful breeding of the tritium in commercial quantities is a requirement.
Breeding blanket designs are mostly based on lithium containing ceramics, with a focus on
lithium titanate and
lithium orthosilicate. These materials, mostly in a pebble form, are used to produce and extract tritium and helium; must withstand high mechanical and thermal loads; and, should not become excessively radioactive upon completion of their useful service life.
To date, no large-scale breeding system has been attempted, and it is an open question whether such a system is possible to create.
ITER
ITER (initially the International Thermonuclear Experimental Reactor, ''iter'' meaning "the way" or "the path" in Latin) is an international nuclear fusion research and engineering megaproject aimed at creating energy by replicating, on Eart ...
runs a major effort in blanket design and will test a number of potential solutions. Concepts for the breeder blanket include helium-cooled lithium lead (HCLL), helium-cooled pebble bed (HCPB), and water-cooled lithium lead (WCLL) methods. Six different tritium breeding systems, known as Test Blanket Modules (TBM) wil be tested in ITER.
References
External links
*
* {{cite web , url=https://www.iter.org/newsline/-/2736 , first= Luciano , last=Giancarli , title=Tritium breeding systems enter preliminary design phase , date=5 June 2017, website=ITER
Nuclear fusion
Lithium