58
Actinides
58.1 INTRODUCTION
Actinides (ACs) is the term used for the elements from actinium [Ac, 89] to lawrencium
[Lr, 103]. The International Union of Pure and Applied Chemistry recommended term
actinoids. Sometimes they are also included in the group of rare earth elements.
The group of ACs contains 14 various elements, but only 5 of them are present in
nature. These are actinum [Ac, 89], thorium [Th, 90], proactinum [Pa, 91], uranium
[U, 92], and plutonium [Pu, 94]. Only two elements exist in relatively large quantities as long-lived nuclides: two isotopes of U ( 235 U and 238 U) and one of Th ( 232 Th).
Thorium is several times more abundant than U. Other ACs, especially Pu, may also
occur in the environment, as a result of natural nuclear reaction of U, but in very negligible amounts. Soils in the vicinity of the Tomsk–Seversk facility (Siberia, Russia)
contain elevated amounts of 239+240 Pu (up to 5900 Bq/m 2 ) and 241 Am (up to 1220 Bq/m 2 )
(Gauthier-Lafaye et al. 2008).
All ACs are radioactive and release energy upon decay. Naturally occurring U
and Th, and synthetically produced Pu are the most abundant ACs on the Earth.
They are used in nuclear reactors and nuclear weapons. Both U and Th have relatively diverse uses. Thorium may replay U in nuclear reactors.
ACs share the following common properties:
r All are radioactive.
r All are highly electropositive.
r The metals tarnish readily in air.
r They are very dense metals and may form several allotropes.
r They react with boiling water or dilute acids to release hydrogen gas.
r All combine directly with most nonmetals.
ACs, as well as lanthanides, are relatively easily taken up by plants, and thus its
concentrations in plants may identify the place of growth. Their content in pumpkin
seed oil has been applied for assessing the geographic origin of plants (Bandoniene
et al. 2013).
58.2 THORIUM [Th, 90]
58.2.1 INTRODUCTION
Thorium is a silvery-white metal and its luster tarnishes in air due to the oxidation.
The degree of oxidation greatly influences its physical properties. Its occurrence in
the Earth’s crust is estimated within the range of 3.6–9.6 mg/kg and is several times
more abundant than all isotopes of U. Its isotope, 232 Th, decays very, very slowly.
381
Actinides
58.1 INTRODUCTION
Actinides (ACs) is the term used for the elements from actinium [Ac, 89] to lawrencium
[Lr, 103]. The International Union of Pure and Applied Chemistry recommended term
actinoids. Sometimes they are also included in the group of rare earth elements.
The group of ACs contains 14 various elements, but only 5 of them are present in
nature. These are actinum [Ac, 89], thorium [Th, 90], proactinum [Pa, 91], uranium
[U, 92], and plutonium [Pu, 94]. Only two elements exist in relatively large quantities as long-lived nuclides: two isotopes of U ( 235 U and 238 U) and one of Th ( 232 Th).
Thorium is several times more abundant than U. Other ACs, especially Pu, may also
occur in the environment, as a result of natural nuclear reaction of U, but in very negligible amounts. Soils in the vicinity of the Tomsk–Seversk facility (Siberia, Russia)
contain elevated amounts of 239+240 Pu (up to 5900 Bq/m 2 ) and 241 Am (up to 1220 Bq/m 2 )
(Gauthier-Lafaye et al. 2008).
All ACs are radioactive and release energy upon decay. Naturally occurring U
and Th, and synthetically produced Pu are the most abundant ACs on the Earth.
They are used in nuclear reactors and nuclear weapons. Both U and Th have relatively diverse uses. Thorium may replay U in nuclear reactors.
ACs share the following common properties:
r All are radioactive.
r All are highly electropositive.
r The metals tarnish readily in air.
r They are very dense metals and may form several allotropes.
r They react with boiling water or dilute acids to release hydrogen gas.
r All combine directly with most nonmetals.
ACs, as well as lanthanides, are relatively easily taken up by plants, and thus its
concentrations in plants may identify the place of growth. Their content in pumpkin
seed oil has been applied for assessing the geographic origin of plants (Bandoniene
et al. 2013).
58.2 THORIUM [Th, 90]
58.2.1 INTRODUCTION
Thorium is a silvery-white metal and its luster tarnishes in air due to the oxidation.
The degree of oxidation greatly influences its physical properties. Its occurrence in
the Earth’s crust is estimated within the range of 3.6–9.6 mg/kg and is several times
more abundant than all isotopes of U. Its isotope, 232 Th, decays very, very slowly.
381