Nearly 80 years after scientists at Oak Ridge National Laboratory discovered an extremely rare radioactive element called promethium, a team from the lab has published a landmark study on the subject that ORNL said could “remake chemistry textbooks.”
The research, published in the journal Nature on May 22, marks the first time scientists have discovered key characteristics of the element, although the study could have implications far beyond promethium (No. 61 on the periodic table).
One of the most critical findings from the research is the bond length between promethium and surrounding atoms, a previously unknown measure that unlocks some of the element’s properties.
Only about half a pound of promethium exists on Earth at any given time. Promethium is mainly used for research, but also in nuclear batteries used for heart pacemakers and space exploration.
The new research could help scientists expand these applications and potentially discover new ones for an element that is still relatively unexplored.
ORNL is the only producer of promethium-147 in the US. Its unique capabilities come from the High Flow Isotope Reactor, one of the world’s most powerful research nuclear reactors. A reactor bombards materials with a concentrated beam of neutrons to create unique materials.
Among these materials is plutonium-238, produced for generators in NASA space missions. There is also californium-252, which is used to run nuclear reactors.
The high flux isotope reactor, which has been operating for almost 60 years, is one of the few facilities in the world that can create artificial elements heavier than uranium.
Promethium was kept a secret by ORNL until the completion of the Manhattan Project
Promethium was first produced in 1945 by Charles Coryell, Jacob A. Marinsky, and Lawrence E. Glendenin as a byproduct of uranium fission in a laboratory graphite reactor.
The scientists named the new element after Prometheus, the Titan and god of fire in Greek mythology who disobeyed the gods of Olympus by bringing fire to people. Scientists kept the discovery of promethium a secret until years after World War II ended and Oak Ridge’s scientific mission moved beyond the Manhattan Project.
Their discovery of promethium filled a gap in the periodic table. Every other element in the group known as the lanthanides had already been discovered and studied.
Lanthanides are 15 elements of no. 57 lanthanum to no. 71 lutetium. They are rare earth elements that are key to modern technologies such as smartphones, laptops, car batteries, lasers and some cancer treatments.
ORNL research boosts efficacy with hard-to-study promethium
For years, lanthanide studies did not include promethium, in part because it is rare and unstable.
The isotope produced by the ORNL researchers, promethium-147, has a half-life of only 2.6 years. This means that by the time the scientists actually produced the radioactive material, it had already begun to decay into another element.
“It’s a big undertaking to prepare to produce a reasonable amount of promethium, especially in a chemically pure form,” Ilja Popovs, an expert scientist who co-led the study, told Knox News. “Producing and handling sufficient quantities of any promethium isotope is quite challenging and requires special facilities and definitely expertise.”
It took scientists four months to isolate and purify a sample of promethium used by several of the world’s leading facilities.
Popovs, along with Alex Ivanov and Santa Jansone-Popov, led the team of 18 study authors. The group used ORNL’s high-flux isotope reactor and hot cells to shield them from radiation. The research also used the Summit laboratory supercomputer, one of the 10 fastest computers in the world.
New promethium discoveries spill over into technology
Scientists have made new discoveries about lanthanide contraction, a phenomenon in which atoms of the elements shrink as their atomic number increases, changing their properties.
The team found that shrinkage slows significantly along the lanthanide sequence after promethium.
This new discovery could increase efficiency in lanthanide separation, a key process for using the elements in modern devices.
“Finding new and better ways that enable more efficient separation of lanthanides is extremely important, and many scientists and research groups are working in this field,” said Popovs. “We hope to add additional information that will allow us to design better processes.”
ORNL has a legacy of discovering the elements
ORNL is credited with the discovery of three elements: promethium in 1945, moscovium in 2003, and tennessine in 2010. Moscovium and tennessine, developed in partnership with a Russian laboratory, were confirmed as new elements by the International Union of Pure and Applied Chemistry in 2015.
In all, the laboratory played a key role in the discovery of the nine elements. The other six are rutherfordium, dubnium, seaborgium, flerovium, livermorium and oganesson, the last chemical on the current periodic table.
For Ivanov, one of the scientists who led the study, continuing the laboratory’s long legacy as a leader in scientific innovation is one of the most rewarding parts of the research. ORNL, managed by UT-Battelle, is the Department of Energy’s largest science and technology laboratory.
Daniel Dassow is a growth and development reporter focusing on technology and energy. Phone 423-637-0878. Email [email protected].
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