Plutonium-244
Decay mode Decay energy (MeV) | | |
α (99.879%) | ||
---|---|---|
SF (0.121%) | ||
Isotopes of plutonium Complete table of nuclides |
Plutonium-244 (244Pu) is an isotope of plutonium that has a half-life of 80 million years. This is longer than any of the other isotopes of plutonium and longer than any other actinide isotope except for the three naturally abundant ones: uranium-235 (704 million years), uranium-238 (4.468 billion years), and thorium-232 (14.05 billion years). Given the mathematics of the decay of plutonium-244, an exceedingly small amount should still be present in the Earth's composition, making plutonium a likely although unproven candidate as the shortest lived primordial element.
Natural occurrence
Accurate measurements, beginning in the early 1970s, appeared to detect
However, the detection of primordial 244Pu in 1971 is not confirmed by recent, more sensitive measurements
Trace amounts of 244Pu (that arrived on Earth within the last 10 million years) were found in rock from the Pacific ocean by a Japanese oil exploration company.[6]
Live interstellar plutonium-244 has been detected in meteorite dust in marine sediments, although the levels detected are much lower than would be expected from current modelling of the in-fall from the interstellar medium.[7] It is important to recall, however, that in order to be a primordial nuclide – one constituting the amalgam orbiting the Sun that ultimately coalesced into the Earth – that plutonium-244 must have comprised some of the solar nebula, rather than having been replenished by extrasolar meteoritic dust. The presence of plutonium-244 in meteoritic composition without evidence the meteor originated from the formational disc of the Solar System supports the hypothesis that 244Pu was abundant enough to have been a part of that disc, if an extrasolar meteor contained it in some other gravitationally supported system, but such a meteor cannot prove the hypothesis. Only the unlikely discovery of live 244Pu within the Earth's composition could do that.
As an extinct radionuclide
Plutonium-244 is one of several extinct radionuclides that preceded the formation of the Solar System. Its half-life of 80 million years ensured its circulation across the solar system before its extinction,[9] and indeed, 244Pu has not yet been found in matter other than meteorites.[10] Radionuclides such as 244Pu undergo decay to produce fissiogenic (i.e., arising from fission) xenon isotopes that can then be used to time the events of the early Solar System. In fact, by analyzing data from Earth's mantle which indicates that about 30% of the existing fissiogenic xenon is attributable to 244Pu decay, the timing of Earth's formation can be inferred to have occurred nearly 50–70 million years following the formation of the Solar System.[11]
Preceding the analysis of
Both the examination of spectra data and study of
Production
Unlike
Applications
Plutonium-244 is used as an internal standard for isotope dilution mass spectrometry analysis of plutonium.[14]
References
- .
- .
- ^ S2CID 4283169.
- ^ .
- . Retrieved 29 January 2024.
- ^ Greenfieldboyce, Nell (May 13, 2021). "Freshly-made plutonium from outer space found on ocean floor". NPR.
- PMID 25601158.
- S2CID 35389103.
- ^ S2CID 11625563.
- ^ S2CID 25831210.
- PMID 9572726.
- S2CID 35389103.
- PMID 26898531.
- ^ OSTI 1024694. Retrieved 2022-10-02.
- PMID 23565016.