Japanese scientists discovered and synthesized a new isotope of the highly radioactive element uranium, Uranium-241. Photo/EnergyIntel
The new isotope, uranium-241, has 92 protons (the same as all uranium isotopes) and 149 neutrons. This number of neutrons makes Uranium-241 the first neutron-rich uranium isotope discovered since 1979.
Uranium belongs to a class of elements on the periodic table known as “actinides”, which have a proton number between 89 and 103. All actinides are radioactive, but uranium is one of the four most radioactive elements, along with radium, polonium, and thorium.
“We measured the masses of 19 different actinide isotopes at a high precision level of one part per million, including the discovery and identification of new uranium isotopes,” said Toshitaka Niwase, researcher at the High Energy Accelerator Research Organization (KEK) Wako Nuclear Science Center (WNSC) in Japan, to Live Science, Monday (17/4/2023).
The research team has not measured the half-life of uranium-241, but theoretical estimates put it at around 40 minutes. This is rather short by half-life standards. The half-life is the time it takes half of a substance to decay into another element.
For reference, the half-life of carbon-14 is 5,730 years, the half-life of the highly unstable isotope technetium-99m is six hours, and that of francium-223 is 22 minutes. The fastest decaying isotope, hydrogen-7, takes only 10^-23 seconds.
Niwase and colleagues created uranium-241 by shooting a sample of uranium-238 at a platinum-198 core in Japan’s RIKEN accelerator. The two isotopes then exchange neutrons and protons, a phenomenon called “multinucleon transfer”.
The team then measured the mass of the isotope made by observing the time it took for the resulting nucleus to travel a certain distance through a medium. The experiment also yielded 18 new isotopes, all of which contain between 143 and 150 neutrons.
Niwase acknowledges that uranium-241 may not have many useful practical or scientific applications, because the isotope is made in very small quantities. Niwase’s discovery was published in the journal Physical Review Letters on March 31, 2023. “This is the first new discovery of a uranium isotope on the neutron-rich side in more than 40 years,” he said.
(wib)
