Volume 90 Issue 21 | p. 9 | News of The Week
Issue Date: May 21, 2012

Plutonium Analysis Advances

Spectroscopy: Study of nuclear waste, fuels enabled by observation of NMR signal
Department: Science & Technology
News Channels: Materials SCENE
Keywords: NMR, plutonium, nuclear fuel, nuclear waste
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Koutroulakis (left) and Yasuoka discuss data in the condensed matter NMR lab at LANL.
Credit: Courtesy of Georgios Koutroulakis
Koutroulakis (left) and Yasuoka collect Pu-239 data in the condensed-matter NMR lab at LANL.
 
Koutroulakis (left) and Yasuoka discuss data in the condensed matter NMR lab at LANL.
Credit: Courtesy of Georgios Koutroulakis

Researchers have detected the long-sought nuclear magnetic resonance signal of plutonium-239, one of the common radioactive elements used in nuclear fuel and weapons.

The discovery will allow scientists to use NMR to directly probe plutonium coordination, electronic structure, and nuclear spin relaxation processes in nuclear fuels and waste, as well as in plutonium-containing superconductors, says Melissa A. Denecke. She is the head of actinide speciation at Karlsruhe Institute of Technology’s Institute for Nuclear Waste Disposal, in Germany, and was not involved in the work.

239Pu has been difficult to study directly because of its radioactivity and complex oxidation chemistry. Additionally, its most common oxidation state, Pu(IV), is nonmagnetic, which means that techniques such as magnetic susceptibility or electron spin resonance yield little information. And NMR experiments are challenging because coupling between unpaired electrons and the nuclear spin leads to rapid relaxation and thus loss of signal.

The 239Pu signal was located by a group of researchers from Los Alamos National Laboratory (LANL) and Japan’s Atomic Energy Agency (JAEA). Led by LANL postdoctoral researcher Georgios Koutroulakis and JAEA scientific counselor Hiroshi Yasuoka, the group studied samples of 239PuO2 that were cooled to 4 K to slow spin relaxation. In contrast to standard NMR experiments, in which the magnetic field is held constant while the radiowave frequency is varied, the researchers held the radio frequency constant and swept the magnetic field from 3 to 8 tesla. They found that the gyromagnetic ratio, which predicts where the signal will appear for a particular frequency and magnetic field combination, is 2.856 × 2π MHz/tesla for 239PuO2.

Additional study of a mixed-oxide sample revealed two distinct NMR signals, indicating that 239Pu NMR should be sensitive to different chemical environments around the Pu atom. Koutroulakis notes, however, that fast relaxation times may still be a problem for other Pu complexes, even at 4 K.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society
Comments
Jeff C. Bryan (Sat Jun 02 13:41:08 EDT 2012)
The use of the word "elements" is incorrect in the first sentence. Plutonium-239 is an isotope of an element, not an element. In the context of the first sentence "nuclides" would best - Pu-239 is one of the nuclides used in nuclear fuel and weapons.

Additionally, "239" is not properly superscripted twice in this article.
Jyllian (Mon Jun 04 12:31:25 EDT 2012)
@Jeff - Thank you for commenting. You make a very good point that "nuclides" would be a better word to use in the first sentence.

We've also corrected the missing superscripts.

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