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 says could “rewrite the chemistry textbooks.”
Research published in Nature on May 22 marks the first time scientists have revealed key characteristics of the element, although the research could have implications far beyond promethium (No. 61 on the periodic table).
One of the most critical findings from the study is the bond length between promethium and surrounding atoms, a previously unknown measurement that unlocks some of the element’s properties.
Only about one kilogram of promethium exists on Earth at any given time. Promethium is used mostly for scientific research, but also in nuclear batteries used for pacemakers and space exploration.
The new research could help scientists expand those applications and potentially discover new ones for an element that is still relatively unexplored.
ORNL is the only producer of promethium-147 in the United States. Its unique capabilities come from the High Flux Isotope Reactor, one of the most powerful research nuclear reactors in the world. The reactor bombards materials with a concentrated beam of neutrons to create unique materials.
Among these materials are plutonium-238 produced for NASA space mission generators. There is also californium-252, used to run nuclear reactors.
The high-flux isotope reactor, in operation for nearly 60 years, is one of the few facilities in the world that can create artificial elements heavier than uranium.
The promethium was kept secret at ORNL until the end of the Manhattan Project
Promethium was first produced as a byproduct of the fission of uranium in the laboratory’s graphite reactor in 1945 by Charles Coryell, Jacob A. Marinsky, and Lawrence E. Glendenin.
The scientists named the new element after Prometheus, a 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 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 has already been discovered and studied.
The lanthanides are the 15 elements from number 57 lanthanum to number 71 lutetium. They are rare earth elements essential to modern technology such as smartphones, laptops, car batteries, lasers and some cancer treatments.
ORNL research boosts efficiency with hard-to-study promethium
For years, research on the lanthanides did not include promethium, in part because of how rare and unstable it is.
The isotope the ORNL researchers produced, promethium-147, has a half-life of only 2.6 years. This means that by the time scientists have actually produced the radioactive material, it has already begun to decay into a different element.
“It’s a pretty big undertaking to prepare to make a reasonable amount of promethium, especially in a chemically pure form,” Ilya Popovs, the scientist who led the research, told Knox News. “Producing and processing sufficient quantities of each isotope of promethium is quite challenging and requires special facilities and certainly expertise.”
It took the scientists, using multiple world-leading facilities, four months to isolate and purify the promethium sample.
Popov, along with Alex Ivanov and Santa Jansone-Popova, lead a team of 18 study authors. 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 study.
New discoveries of promethium spread in technology
Scientists have made new discoveries about lanthanide contraction, a phenomenon in which atoms of the elements become smaller as their atomic number increases, changing their properties.
The team found that the contraction slows significantly along the lanthanide series after promethium.
This new discovery could increase efficiency in the separation of the lanthanides, a critical process for using the elements in modern devices.
“Devising 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,” said Popov. “We hope to add additional information that will allow us to design better processes.”
ORNL has a legacy of discovering elements
ORNL is credited with the discovery of three elements: promethium in 1945, muscovium in 2003, and tenesine in 2010. Muscovium and tenesine, developed in partnership with a Russian laboratory, were verified as new elements by the International Union of Pure and Applied Chemistry in 2015.
In all, the lab played a critical role in the discovery of nine elements. The other six are rutherfordium, dubnium, cyborgium, flerovium, livermorium, and oganesone, the last chemical on the current periodic table.
For Ivanov, one of the scientists who led the research, 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 focusing on technology and energy. Phone 423-637-0878. Email daniel.dassow@knoxnews.com.
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