Neutron absorbers are
isotopeIsotopes are different types of atoms of the same chemical element, each having a different number of neutrons. Correspondingly, isotopes differ in mass number but not in atomic number. The difference in the number of nucleons comes from a difference how many neutrons are in the atomic nucleus...
s of certain
elementsA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.Common examples of elements...
that absorb free neutrons creating heavier isotopes of the same element. The most prolific neutron absorbers are elements that become stable by absorbing a
neutronThe neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutron are usually found in atomic nuclei. The nuclei of most atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of protons in a...
such as
xenon-135135Xe is an unstable isotope of xenon with a half-lifeabout 9.2 hours. 135Xe is a fission product of Uranium which is the most powerful known neutron-absorbingnuclear poison and has a significant effect on...
(Xe-135, half life 9.1 hours), which absorbs a neutron to become Xe-136. Xe-135 is formed in
nuclear reactorA nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate.The most significant use of nuclear reactors is as an energy source for the generation of electrical power and for the power in some ships...
s through the splitting of
actinideThe actinoid or actinide series encompasses the 15 chemical elements that lie between actinium and lawrencium included on the periodic table, with atomic numbers 89 - 103...
metals indirectly as a
decay productIn nuclear physics, a decay product is a nuclide produced by radioactive decay. Radioactive decay often involves a sequence of steps...
of
iodineIodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
-135 (I-135), which also has a short half-life.
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Neutron absorbers are
isotopeIsotopes are different types of atoms of the same chemical element, each having a different number of neutrons. Correspondingly, isotopes differ in mass number but not in atomic number. The difference in the number of nucleons comes from a difference how many neutrons are in the atomic nucleus...
s of certain
elementsA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.Common examples of elements...
that absorb free neutrons creating heavier isotopes of the same element. The most prolific neutron absorbers are elements that become stable by absorbing a
neutronThe neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutron are usually found in atomic nuclei. The nuclei of most atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of protons in a...
such as
xenon-135135Xe is an unstable isotope of xenon with a half-lifeabout 9.2 hours. 135Xe is a fission product of Uranium which is the most powerful known neutron-absorbingnuclear poison and has a significant effect on...
(Xe-135, half life 9.1 hours), which absorbs a neutron to become Xe-136. Xe-135 is formed in
nuclear reactorA nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate.The most significant use of nuclear reactors is as an energy source for the generation of electrical power and for the power in some ships...
s through the splitting of
actinideThe actinoid or actinide series encompasses the 15 chemical elements that lie between actinium and lawrencium included on the periodic table, with atomic numbers 89 - 103...
metals indirectly as a
decay productIn nuclear physics, a decay product is a nuclide produced by radioactive decay. Radioactive decay often involves a sequence of steps...
of
iodineIodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
-135 (I-135), which also has a short half-life. Other isotopes that are major neutron absorbers include
heliumHelium is the chemical element with atomic number 2, and is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert monatomic gas that heads the noble gas group in the periodic table...
-3 (He-3), which becomes
tritiumTritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
and
boronBoron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a trivalent metalloid element which occurs abundantly in the evaporite ores borax and ulexite....
-10 (B-10) which becomes Li-7. Samarium-149 formed during the fission process is also a highly effective neutron absorber, with its very long half life it last effectively forever in the fuel until it absorbs a neutron and transmutes into Sm-150, which is stable. Other neutron absorbers used in nuclear power plants include
cadmiumCadmium is a chemical element with the symbol Cd and atomic number 48. The soft, bluish-white transition metal is chemically similar to the two other metals in group 12, zinc and mercury. Similar to zinc it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
and
gadoliniumGadolinium is a chemical element that has the symbol Gd and atomic number 64. It is a silvery-white, malleable and ductile rare-earth metal. Gadolinium has exceptionally high absorption of neutrons and therefore is used for shielding in neutron radiography and in nuclear reactors...
, both of which consist of mixed isotopes some of which are voracious neutron absorbers.