Synthesizing ununseptium, element number 117, took more than a little legwork.
How hard is it to make a new element? Logistically, it’s harder than you might think — especially if the groups collaborating on the work are formerly secret nuclear weapons laboratories in the United States and Russia.
The Physical Review Letters paper announcing the find is headed by Yuri Oganessian, a nuclear physicist at the Joint Institute for Nuclear Research in Dubna, Russia — a lab that was born in secrecy immediately after World War II and only emerged into daylight in the 1950s. Also notable on the author list are many names from the Oak Ridge National Laboratory in Tennessee, the descendant of one of several groups in Oak Ridge that developed materials during the Manhattan Project for the U.S. atomic bomb.
And Dubna and ORNL needed to work together if element 117 was going to get made. Oganessian knew he wanted to smash calcium-48 together with berkelium-249. The Dubna researchers were famous for their method of making calcium-48, but they would need ORNL’s help to get the berkelium-249. The heavy, unstable element can be made in Oak Ridge’s High Flux Isotope Reactor.
Joseph Hamilton, a nuclear physicist at Vanderbilt University in Nashville, says that Oganessian asked for his help in getting a berkelium target from ORNL. “The problem was, the typical cost for such a target was about $3.5 million,” Hamilton says. The cheapest way to get some would be to wait for another group to order up some californium-252, since berkelium-249 is a byproduct of making the californium. And it would cost only a few hundred thousand dollars to separate out. “So every four months I would call the reactor and ask is there any campaign on to make californium,” Hamilton says. “And in the summer of 2008 they said yes.” An oil company, which uses californium in geophysical exploration, had ordered up a batch of the stuff.
ORNL scientists let it all cool for three months and spent another three months painstakingly separating the berkelium from the californium. Then came an equally hard part: figuring out how to ship it to Russia. “When you’re transferring 36 curies [a measure of radioactivity] of berkelium to Russia, you go through a lot of desks,” says Krzysztof Rykaczewski, an ORNL physicist who helped coordinate the transfer.
Once the paperwork was finally sorted, Oak Ridge researchers packed the berkelium in five separate barrels, each with a minuscule 4.4 milligrams of the stuff heavily shielded by lead. In fact, Rykaczewski says, the shipment was so well protected against radioactivity leakage that when it arrived at customs, fresh off the Delta flight, Russian officials didn’t believe it was berkelium because they couldn’t detect any radioactivity. Only when they lifted the lid, and the Geiger counters started to click frantically, did they believe it, he says.
And off the berkelium target went to Dubna, where late last year it helped make a brand-new element never before seen on Earth.
Oganessian, Y.T., et al. 2010. Synthesis of a new element with atomic number Z=117. Physical Review Letters. LQ12400.