Nearly 80 years after scientists at Oak Ridge National Laboratory discovered an extremely rare radioactive element called promethium, a team at the lab has published a landmark study on the topic that ORNL said could “rewrite the chemistry textbooks.”
The research, published in Nature on May 22, is the first time scientists have revealed key properties of the element, although the study could have implications far beyond promethium (No. 61 on the periodic table).
One of the research’s most critical discoveries is the bond length between promethium and surrounding atoms, a previously unknown measurement that reveals some of the element’s properties.
Only about one pound of promethium exists on Earth at any given time. Promethium is used mostly for research, but also in nuclear batteries used for pacemakers and space exploration.
The new research could help scientists expand these applications and potentially make new discoveries 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 Isotope Flux Reactor, one of the most powerful nuclear research reactors in the world. The reactor bombards materials with a concentrated beam of neutrons, creating unique materials.
These materials include plutonium-238, produced for generators on NASA space missions. There is also californium-252, used to start nuclear reactors.
The High Flux Isotope Reactor, which has been in operation for nearly 60 years, is one of the few facilities in the world capable of creating man-made elements heavier than uranium.
Promethium was kept secret by ORNL until the Manhattan Project
Promethium was first produced as a byproduct of uranium fission in a laboratory graphite reactor in 1945 by Charles Coryell, Jacob A. Marinsky, and Lawrence E. Glendenin.
Scientists have named a new element for Prometheus, the Titan and god of fire in Greek mythology who disobeyed the gods of Olympus by bringing fire to humans. Scientists kept the discovery of promethium a secret until years after World War II ended and the Oak Ridge Science 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 has already been discovered and studied.
Lanthanoids are 15 elements ranging from lanthanum #57 to lutetium #71. They are rare earth elements that are essential to modern technology such as smart phones, laptops, car batteries, lasers and some cancer treatments.
ORNL research boosts efficiency with hard-to-study promethium
For years, studies of the lanthanides did not include promethium, in part because of how rare and unstable it is.
The isotope produced by ORNL researchers, promethium-147, has a half-life of just 2.6 years. This means that by the time scientists have actually produced the radioactive material, it has already begun to decay into another element.
“It’s quite an undertaking to prepare to produce a reasonable amount of promethium, especially in a chemically pure form,” Ilja Popovs, a scientist who led the study, told Knox News. “Producing and handling sufficient quantities of any promethium isotope is quite difficult and requires special equipment and certainly expertise.”
Using several world-leading facilities, it took the scientists four months to isolate and purify a sample of promethium.
Popovs, along with Alex Ivanov and Santa Jansone-Popova, led a team of 18 authors on the study. The group used ORNL’s High Flux Isotope Reactor and hot cells to shield them from radiation. The lab’s Summit supercomputer, one of the 10 fastest computers in the world, was also used in the research.
New discoveries of promethium spread 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 diminution slows significantly along the lanthanide series after promethium.
This new discovery could increase the efficiency of lanthanide separation, a critical process for using the elements in modern devices.
“Coming up with new and better ways that allow more efficient separation of lanthanides is extremely important, and quite a few scientists and research groups are working in this area,” Popovs said. “We hope to add more 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. Developed in collaboration with a Russian laboratory, moscovium and tennessine were verified as new elements by the International Union of Pure and Applied Chemistry in in 2015.
In all, the lab played a key role in the discovery of nine elements. The other six are rutherfordium, dubnium, seaborgium, flerovium, livermorium, and oganesson, the last chemical in the current periodic table.
For Ivanov, one of the scientists who led the study, continuing the lab’s long legacy as a leader in scientific innovation is among 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 focused on technology and energy. Phone 423-637-0878. Email daniel.dassow@knoxnews.com.
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