International team discovers element 117
Oak Ridge National Laboratory is part of a team that has added a new chemical element to the Periodic Table. The news came after a paper on the discovery of element 117 had been accepted for publication in Physical Review Letters.
The team includes two Russian partners, the Joint Institute of Nuclear Research in Dubna and the Research Institute for Advanced Reactors in Dimitrovgrad. Other team members included Lawrence Livermore National Laboratory, Vanderbilt University and the University of Nevada, Las Vegas.
ORNL's role included production of the berkelium-249 isotope necessary for the target, which was subjected to an extended, months-long run at the heavy ion accelerator facility at Dubna.
"Without the berkelium target, there could have been no experiment," says ORNL Director of Strategic Capabilities Jim Roberto, who is a principal author on the Physical Review Letters paper and who helped initiate the experiment.
The berkelium was produced at ORNL's High Flux Isotope Reactor and processed at the adjoining Radiochemical Engineering & Development Laboratory as part of the most recent campaign to produce californium- 252, a radioisotope widely used in industry and medicine.
"Russia had proposed this experiment in 2004, but since we had no californium production at the time, we could not supply the berkelium. With the initiation of californium production in 2008, we were able to implement a collaboration," Roberto says.
Roberto worked closely with Yuri Oganessian of Russia's JINR. Five months at the Dubna JINR U400 accelerator's calcium-48 beam—one of the world's most powerful—was dedicated to the project. Lawrence Livermore contributed data analysis, and the entire team was involved in the assessment of the results.
The massive effort produced a total of six atoms of element 117 and the critical reams of data that substantiate their existence.
The two-year experimental campaign began with a 250-day irradiation in HFIR, producing 22 milligrams of berkelium-249, which has a 320-day half-life. The irradiation was followed by 90 days of processing at REDC to separate and purify the berkelium. The berkelium-249 target was prepared at Dimitrovgrad and then bombarded for 150 days at the Dubna facility.
This is the second element that ORNL has had a role in discovering. Element 117 joins element 61, promethium, which was discovered at the Graphite Reactor during the Manhattan project and reported in 1946. ORNL, through the production of radioisotopes for research, has contributed to the discovery of a total of seven new elements.
Members of the ORNL team include the Physics Division's Krzysztof Rykaczewski; Porter Bailey of the Nonreactor Nuclear Facilities Division; and Dennis Benker, Julie Ezold, Curtis Porter and Frank Riley of the Nuclear Science and Technology Division.
Roberto says the success of the element- 117 campaign underscores the value of international collaborations in science. "The 117 experiment paired one of the world's leading research reactors—capable of producing the berkelium target material—with the exceptional heavy ion accelerator and detection capabilities at Dubna. This use of ORNL isotopes and Russian accelerators is a tremendous example of the value of working together," he says.
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