Nearly 80 years after scientists at Oak Ridge National Laboratory discovered an extremely rare radioactive element called promethium, a team at the lab published a landmark study on the subject that ORNL said could “rewrite chemistry textbooks.”
Research published in Nature on May 22 marks the first time scientists have uncovered key characteristics of the element, though the study could have implications far beyond promethium (No. 61 on the periodic table).
One of the most critical discoveries from the research is the bond length between promethium and surrounding atoms, a previously unknown measurement that unlocks some of the element’s properties.
At any given time, only about one pound of promethium exists on Earth. 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 discover new ones for an element that’s still relatively unexplored.
ORNL is the only producer of promethium-147 in the U.S. Its unique capabilities come from the High Flux Isotope Reactor, one of the world’s most powerful research nuclear reactors. The reactor bombards materials with a concentrated beam of neutrons to create unique materials.
Among those materials are plutonium-238, produced for generators on NASA space missions. There’s also californium-252, used for starting up nuclear reactors.
The High Flux Isotope Reactor, operational for nearly 60 years, is one of the few facilities in the world that can create manmade elements heavier that uranium.
Promethium was kept an ORNL secret until after Manhattan Project
Promethium was first produced as a byproduct of uranium fission at the lab’s Graphite Reactor in 1945 by Charles Coryell, Jacob A. Marinsky and Lawrence E. Glendenin.
The scientists named the new element for Prometheus, a Titan and the god of fire in Greek mythology who disobeyed the gods of Olympus by bringing fire to humans. The scientists kept the discovery of promethium 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 lanthanides had already been discovered and studied.
Lanthanides are the 15 elements from No. 57 lanthanum to No. 71 lutetium. They are rare earth elements that are essential to modern technologies such as smartphones, laptops, car batteries, lasers and some cancer treatments.
ORNL research increases efficiency with hard-to-study promethium
For years, studies on lanthanides have not included 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. That means by the time scientists have actually produced the radioactive material, it has already started to decay into a different element.
“It is quite an undertaking to prepare to make a reasonable amount of promethium, especially in a chemically pure form,” Ilja Popovs, a staff scientist who co-led the study, told Knox News. “Producing and handling sufficient quantities of any isotope of promethium is fairly challenging and requires special facilities and definitely expertise.”
It took scientists using multiple world-leading facilities four months to isolate and purify the 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 protect them from radiation. The lab’s Summit supercomputer, one of the top 10 fastest computers in the world, also was used in the research.
New promethium discoveries spill into tech
The scientists made new discoveries about lanthanide contraction, a phenomenon in which the elements’ atoms get smaller as their atomic number increases, changing their properties.
The team uncovered that the shrinking slows down considerably along the lanthanide series after promethium.
This new discovery could increase efficiency in separating lanthanides, a critical process for using the elements in modern devices.
“Figuring out 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 that field,” Popovs said. “We hope that we’re gonna add an additional piece of information that will allow us to design better processes.”
ORNL has legacy of discovering 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 lab, were verified as new elements by the International Union for Pure and Applied Chemistry in 2015.
Overall, the lab has played a critical role in the discovery of 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, carrying on 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 lab.
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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