Scientists solve plutonium puzzle

LIVERMORE, Calif., June 6 (UPI) -- U.S. scientists have solved a question about the nature of plutonium that had remained a mystery since the Manhattan Project.

Plutonium behaves as no other element. The bonding of its electrons causes its crystal structure to be uneven, similar to a mineral, and the nucleus is unstable, causing the metal to spontaneously decay over time and damage the surrounding metal lattice.

Manhattan Project scientists resolved the problem by adding a small amount of gallium.

"There was never a clear explanation as to why gallium stabilized the ductile cubic structure over the low-symmetry mineral-like structure;" said Kevin Moore, a staff scientist at the Lawrence Livermore National Laboratory. "They just did it and it worked."

Researchers now, for the first time, have determined why gallium works. In pure plutonium, the bonds between atoms are very uneven, causing the metal's high propensity to adopt a low-symmetry structure. However, when a gallium atom is put into the plutonium lattice, it causes the bonds to become more uniform and thus leads to the high-symmetry cubic structure.

The research is outlined in the May 26 online edition of Physical Review Letters.