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New Radiochemistry Facility To Open At PNNL

Dedicated instrumentation will enhance study of nuclear fuels and waste, environmental contamination

by Jyllian Kemsley
January 28, 2013 | A version of this story appeared in Volume 91, Issue 4

Credit: Scott Butner/PNNL
EMSL scientist Nancy Washton inspects an NMR spectrometer during installation in the Radiochemistry Annex.
PNNL scientist Nancy Washton inspects one of the NMRs during installation in the Radiochemistry Annex.
Credit: Scott Butner/PNNL
EMSL scientist Nancy Washton inspects an NMR spectrometer during installation in the Radiochemistry Annex.

A one-of-a-kind user facility for studying radioactive materials with state-of-the-art analytical instrumentation is set to open at Pacific Northwest National Laboratory (PNNL) in April.

The facility, known as the Radiochemistry Annex, should enable scientists to gain a better understanding of the subsurface transport of radioactive environmental contaminants as well as nuclear fuels and waste storage materials, says Nancy J. Hess, lead scientist for geochemistry, biogeochemistry, and subsurface science at PNNL’s W. R. Wiley Environmental Molecular Sciences Laboratory (EMSL). Researchers currently study such topics at facilities scattered around the U.S., often with repurposed equipment, Hess says. EMSL is PNNL’s user facility for high-end molecular sciences instrumentation, and the annex falls under its umbrella. National lab user facilities make scientific tools available to external users, who are granted access on the basis of research proposals they submit.

The annex will house glove boxes for wet chemistry and sample preparation, so users can manipulate samples on-site, Hess says. For instance, users can change the pH of soil samples to emulate different soil-leaching conditions right there. EMSL scientists running the instruments will also try to get users results in real time. Hess wants to give annex users as much flexibility as possible to make the most of their time and minimize failed experiments, she says.

For sample analysis, the facility will include a full suite of analytic, spectroscopic, and imaging tools, such as electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), X-ray photoelectron, and inductively coupled plasma mass spectrometers. The annex will also have scanning probe, transmission electron, and scanning electron microscopes and a superconducting quantum interference device (SQUID) magnetometer.

The only instrument that really needed to be customized for radioactive materials was a high-field, wide-bore NMR device, Hess says. EMSL wanted the instrument to be able to interrogate solid-state samples, but that requires spinning at high speeds. If the sample container failed, then the magnet would be contaminated with radioactive material. EMSL scientists came up with a design for an encapsulated rotor in which the top part is sealed from the interior of the magnet. “If the rotor were to explode, everything from the sample would be encased in this part,” Hess says. The sealed rotor costs about $15,000 to replace, but that’s still far less than $2 million for a new magnet.

The annex building was completed two years ago for another purpose, but the intended occupants decided not to move in, Hess says. The Department of Energy’s Office of Biological & Environmental Research provided $4.5 million to retrofit the facility to handle radioactive materials. An additional $7.5 million for instrumentation came from American Recovery & Reinvestment Act funds. The annex was supposed to open in February, but difficulties retrofitting air ducts with new filters have pushed back the opening, now scheduled for April, Hess says. EMSL is accepting research proposals to use the facility.

Ian Farnan, a professor of earth sciences at the University of Cambridge, is on EMSL’s advisory board and was an advocate for the facility from the start, he says. He is part of a consortium in the U.K. that is looking at spent nuclear fuel storage and how the materials might fare over time. He is excited about the opportunity to be able to use surface science techniques that until now have not been available to study radioactive samples. He highlights the ability to look at how solid uranium dioxide might interact with fluids such as groundwater, or how radioactive elements might sorb to different minerals and how that in turn affects their eventual release to the biosphere.

Also, one of the challenges of studying actinides is that “the electronic structures are very difficult to predict,” Farnan says. Research is still needed to work out how to describe actinide electronic structures and how they will react in different situations, Farnan says, and instruments such as EPR and SQUID will aid that effort.

PNNL is adjacent to the Hanford Site in Washington state, a former nuclear weapons production complex and the “American leader in radionuclide contamination of the environment,” says Peter C. Burns, a professor of civil engineering and geological sciences at the University of Notre Dame and director of the Department of Energy-funded Energy Frontier Research Center for Materials Science of Actinides. Many scientists at PNNL are working on aspects of environmental transport of those radionuclides, Burns notes, so it makes sense to have the annex there. It will significantly extend the science that PNNL researchers are able to do.

For his part, he is looking forward to using annex instrumentation to study the fate of neptunium in the environment. Neptunium doesn’t occur naturally in significant quantity but was concentrated during weapons-related activities, Burns says. Rock-forming materials can incorporate substantial amounts of neptunium, he adds. The new instrumentation will allow his group to study the element’s oxidation states and local environments and develop a better understanding of the crystal chemistry of its incorporation in rocks.

Studies like that ultimately will feed into policy decisions, Hess says, and that in part is the goal of creating the facility. “Science coming from the Radiochemistry Annex will provide new insights on a molecular scale,” Hess says. “In the long run, that will help decisionmakers and provide greater confidence in decisions regarding radioactive fuel and waste storage.”



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