# Minor actinide

Minor actinides in the periodic table
Hydrogen
Helium
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
Sodium
Magnesium
Aluminium
Silicon
Phosphorus
Sulfur
Chlorine
Argon
Potassium
Calcium
Scandium
Titanium
Vanadium
Chromium
Manganese
Iron
Cobalt
Nickel
Copper
Zinc
Gallium
Germanium
Arsenic
Selenium
Bromine
Krypton
Rubidium
Strontium
Yttrium
Zirconium
Niobium
Molybdenum
Technetium
Ruthenium
Rhodium
Palladium
Silver
Cadmium
Indium
Tin
Antimony
Tellurium
Iodine
Xenon
Caesium
Barium
Lanthanum
Cerium
Praseodymium
Neodymium
Promethium
Samarium
Europium
Gadolinium
Terbium
Dysprosium
Holmium
Erbium
Thulium
Ytterbium
Lutetium
Hafnium
Tantalum
Tungsten
Rhenium
Osmium
Iridium
Platinum
Gold
Mercury (element)
Thallium
Lead
Bismuth
Polonium
Astatine
Radon
Francium
Radium
Actinium
Thorium
Protactinium
Uranium
Neptunium
Plutonium
Americium
Curium
Berkelium
Californium
Einsteinium
Fermium
Mendelevium
Nobelium
Lawrencium
Rutherfordium
Dubnium
Seaborgium
Bohrium
Hassium
Meitnerium
Darmstadtium
Roentgenium
Copernicium
Nihonium
Flerovium
Moscovium
Livermorium
Tennessine
Oganesson :
Major actinides in the periodic table
Hydrogen
Helium
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
Sodium
Magnesium
Aluminium
Silicon
Phosphorus
Sulfur
Chlorine
Argon
Potassium
Calcium
Scandium
Titanium
Vanadium
Chromium
Manganese
Iron
Cobalt
Nickel
Copper
Zinc
Gallium
Germanium
Arsenic
Selenium
Bromine
Krypton
Rubidium
Strontium
Yttrium
Zirconium
Niobium
Molybdenum
Technetium
Ruthenium
Rhodium
Palladium
Silver
Cadmium
Indium
Tin
Antimony
Tellurium
Iodine
Xenon
Caesium
Barium
Lanthanum
Cerium
Praseodymium
Neodymium
Promethium
Samarium
Europium
Gadolinium
Terbium
Dysprosium
Holmium
Erbium
Thulium
Ytterbium
Lutetium
Hafnium
Tantalum
Tungsten
Rhenium
Osmium
Iridium
Platinum
Gold
Mercury (element)
Thallium
Lead
Bismuth
Polonium
Astatine
Radon
Francium
Radium
Actinium
Thorium
Protactinium
Uranium
Neptunium
Plutonium
Americium
Curium
Berkelium
Californium
Einsteinium
Fermium
Mendelevium
Nobelium
Lawrencium
Rutherfordium
Dubnium
Seaborgium
Bohrium
Hassium
Meitnerium
Darmstadtium
Roentgenium
Copernicium
Nihonium
Flerovium
Moscovium
Livermorium
Tennessine
Oganesson :
A minor actinide is an actinide, other than uranium or plutonium, found in spent nuclear fuel. The minor actinides include neptunium (element 93), americium (element 95), curium (element 96), berkelium (element 97), californium (element 98), einsteinium (element 99), and fermium (element 100). The most important isotopes of these elements in spent nuclear fuel are neptunium-237, americium-241, americium-243, curium-242 through -248, and californium-249 through -252.
Plutonium and the minor actinides will be responsible for the bulk of the radiotoxicity and heat generation of spent nuclear fuel in the long term (300 to 20,000 years in the future).
The plutonium from a power reactor tends to have a greater amount of plutonium-241 than the plutonium generated by the lower burnup operations designed to create weapons-grade plutonium. Because the reactor-grade plutonium contains so much $^{241}$Pu, the presence of $^{241}$Am makes the plutonium less suitable for making a nuclear weapon. The ingrowth of americium in plutonium is one of the methods for identifying the origin of an unknown sample of plutonium and the time since it was last separated chemically from the americium.
Americium is commonly used in industry as both an alpha particle source and as a low photon-energy gamma radiation source. For example, it is commonly used in smoke detectors. Americium can be formed by neutron capture of $^{239}$Pu and $^{240}$Pu, forming $^{241}$Pu which then beta decays to $^{241}$Am. In general, as the energy of the neutrons increases, the ratio of the fission cross section to the neutron capture cross section changes in favour of fission. Hence, if MOX is used in a thermal reactor such as a boiling water reactor (BWR) or pressurized water reactor (PWR) then more americium can be expected to be found in the spent fuel than in that from a fast neutron reactor.
Some of the minor actinides have been found in fallout from bomb tests. See Actinides in the environment for details.
Transuranics in LWR spent fuel (burnup 55 GWd$_{th}$/T) and mean neutron consumption via fission :
| Isotope | Fraction | D$_{LWR}$ | D$_{fast}$ | D$_{superthermal}$ |
| $^{237}$ Np | 0.0539 | 1.12 | −0.59 | −0.46 |
| $^{238}$ Pu | 0.0364 | 0.17 | −1.36 | −0.13 |
| $^{239}$ Pu | 0.451 | −0.67 | −1.46 | −1.07 |
| $^{240}$ Pu | 0.206 | 0.44 | −0.96 | 0.14 |
| $^{241}$ Pu | 0.121 | −0.56 | −1.24 | −0.86 |
| $^{242}$ Pu | 0.0813 | 1.76 | −0.44 | 1.12 |
| $^{241}$ Am | 0.0242 | 1.12 | −0.62 | −0.54 |
| $^{242m}$ Am | 0.000088 | 0.15 | −1.36 | −1.53 |
| $^{243}$ Am | 0.0179 | 0.82 | −0.60 | 0.21 |
| $^{243}$ Cm | 0.00011 | −1.90 | −2.13 | −1.63 |
| $^{244}$ Cm | 0.00765 | −0.15 | −1.39 | −0.48 |
| $^{245}$ Cm | 0.000638 | −1.48 | −2.51 | −1.37 |
| Weighted sum | Weighted sum | −0.03 | −1.16 | −0.51 |