In the classification Actinide, elements with atomic numbers 89 to 103 are included and are the third group in the periodic table. The sequence is the row beneath the Lanthanide series, positioned beneath the main section of the periodic table. Both Actinide and Lanthanide series are labelled as Rare Earth Metals.  

Uranium, which is used as a nuclear fuel and is converted into plutonium by a nuclear reaction, is the most common and recognized actinide element. The actinides have a wide array of oxidation numbers and are all radioactive in nature.

A Brief History of Actinides

  • Uranium by Klaproth in 1789 and Thorium by Berzelius in 1829 were the very first actinides to be identified. 
  • However, most of the actinides are the human-made element of the twentieth century. 
  • Actinium & Protactinium, as decay products of 253-Uranium and 238-Uranium, are present in low amounts in the environment. 
  • The Thorium Ore form produces tiny quantities of plutonium, and it is a phosphate ore containing significant amounts of Lanthanides in it.
  • The primary uranium ore is U3O8, since it exists in black, pitch-like masses and is recognized as pitchblende.   
  • All elements that go beyond uranium are human-made. 
  • Actinides, since most of them are radioactive & unstable, demand specialized treatment. 
  • In the chemistry and distribution of particles in crystals, radiation in actinides plays a significant role.

Characteristics of Actinide Elements

  • Actinides, as a result of instability, most of them are radioactive. 
  • Most of them are synthetically created by particle accelerators that cause nuclear reactions and are short-lived. 
  • Because of the atomic number above 83, every element is unstable & reactive. 
  • In metallic nature, all have them are silvery/silvery-white lustre. 
  • With ligands, such as sulfate, chloride, carbonate & acetate, every element has the potential to form stable compounds. 
  • Most of those actinides survive in the environment as ocean water or minerals.
  • Actinides are capable of undergoing nuclear reactions.
  • Properties that render them unsafe to treat are the release of toxicity, radioactivity, nuclear criticality and pyrophoricity.

Usage of Actinides Compounds

  1. Actinides are used as a fuel in nuclear weapons as well as in nuclear reactors. 
  2. The main isotope of nuclear power is uranium-235, which thoroughly absorbs thermal neutrons that release a large amount of energy. 
  3. Approximately half of the produced Thorium is used as the gas mantle light-emitting component.
  4. Currently, Thorium is used for gas lanterns, cooking & decorative gas lamps.
  5. For smoke detectors, the 241-Americium isotope is being used as an ionizing source.

Nuclear Reactions

The development of a short-lived barium radioisotope that was separated from neutron-irradiated uranium must have been some initial evidence for nuclear fission. It was believed that it was a new radium isotope, as using a barium sulphate carrier precipitate to aid in the separation of radium was then standard radiochemical procedure.

Plutonium uranium reduction extraction (PUREX) is a chemical process that used purify fuels for nuclear weapons or reactors. PUREX is used for spent fuel, that mainly consists of actinide elements of very high atomic weight such as uranium, plutonium, americium, along with smaller quantities of material consisting of lighter atoms, in particular known as fission products.

The Chemical Process of PUREX

The fuel dissolves in (nitric acid) HNO3 at a concentration of approximately ca 7 M. In the solvent extraction setting, solids are extracted by filtration if they do not form emulsions, known as third phases. In a hydrocarbon, like kerosene, the organic solvent consists of 30 percent TBP (tributyl phosphate). Uranium ions are obtained as compounds of UO2(NO3)2·2TBP & plutonium as comparable compounds.

Other fission materials, including Americium & Curium, reside in the aqueous state. Some study has focussed on the existence of the organic soluble uranium compound. The presence of the trialkyl phosphate compounds of uranyl nitrate has been described. 

By processing the kerosene solution with reducing agents to transform the plutonium to the oxidation state of +3 and it is isolated from uranium. Ferrous sulphamate, hydrazine and N, N – diethyl -hydroxylamine are common reducing agents.