Chemistry 2011.org
Chemistry2011.org
All About Chemistry... 2011 and beyond

Related Stories

Nuclear reactor fuel behavior during a severe event

A new discovery about the atomic structure of uranium dioxide will help scientists select the best computational model to simulate severe nuclear reactor accidents.

Using the Advanced Photon Source (APS), a Department of Energy (DOE) Office of Science User Facility, researchers from DOE's Argonne National Laboratory and Brookhaven National Laboratory, along with Materials Development, Inc., Stony Brook University, and Carnegie Institution of Washington, found that the atomic structure of uranium dioxide (UO2) changes significantly when it melts.

UO2 is the primary fuel component in the majority of existing nuclear reactors, but little is known about the molten state because of its extremely high melting point. Until now, the extremely high temperature and chemical reactivity of the melt have hindered studies of molten UO2. This lack of fundamental information has made it difficult to evaluate issues associated with the interaction of molten UO2 with a reactor's zirconium cladding and steel containment vessel.

The research team found that when uranium dioxide melts, the number of oxygen atoms around uranium changes from eight-fold to a mixture of six- and seven-fold, which changes the way it interacts with other materials. Many existing models, however, do not account for this change in structure or the rapid oxygen dynamics that occur at high temperatures. "Determining the behavior of UO2 under extreme conditions is essential to enhancing our understanding of reactor safety during severe accidents," said Mark Williamson of Argonne's Chemical Sciences and Engineering Division.

"Very few places in the world have the capability to safely measure the structure of molten UO2 at 3,000 degrees Celsius without introducing contamination from the container that holds the melt," added Chris Benmore of Argonne's X-ray Science Division.

Researchers studied the UO2 in the hot crystalline and molten states. In this experiment, researchers relied on the APS's high-energy synchrotron X-ray beam to study a bead of UO2 that was aerodynamically levitated on a stream of argon and heated with a laser beam. X-ray experiments were performed at sector 11-ID-C at the APS. The work was funded by the DOE Office of Science (Office of Basic Energy Sciences), the DOE Small Business Innovation Research program and the Argonne Laboratory Directed Research and Development program. The paper, "Molten uranium dioxide structure and dynamics," is published in Science magazine.

"Our group plans to continue to use innovative synchrotron techniques to study molten materials like this," said John Parise, who holds a joint appointment with Brookhaven National Laboratory and Stony Brook University. "The next steps include putting molten materials under different atmospheres, and that requires modifications to the existing set-up used at APS."

Parise said this group of researchers, which includes colleagues from Materials Development, Inc., who built the apparatus used to study UO2, is discussing designs for next-generation levitation devices that could be installed at the X-Ray Powder Diffraction beamline at Brookhaven's National Synchrotron Light Source II, for example. "There's a lot more work to be done," Parise said. "It's important to understand how many other materials behave in a molten state. Theory is a good way to do that, but theorists need data on how atoms interact with each other in the molten state, under conditions that are as realistic as possible."

Story Source:

The above story is based on materials provided by Argonne National Laboratory. Note: Materials may be edited for content and length.

Share this story with your friends!

Social Networking

Please recommend us on Facebook, Twitter and more:

Other social media tools

Global Partners
Feedback

Tell us what you think of Chemistry 2011 -- we welcome both positive and negative comments. Have any problems using the site? Questions?

About us

Chemistry2011 is an informational resource for students, educators and the self-taught in the field of chemistry. We offer resources such as course materials, chemistry department listings, activities, events, projects and more along with current news releases.

Events & Activities

Are you interested in listing an event or sharing an activity or idea? Perhaps you are coordinating an event and are in need of additional resources? Within our site you will find a variety of activities and projects your peers have previously submitted or which have been freely shared through creative commons licenses. Here are some highlights: Featured Idea 1, Featured Idea 2.

About you

Ready to get involved? The first step is to sign up by following the link: Join Here. Also don’t forget to fill out your profile including any professional designations.

Global Partners