Neutron Science In the News – 2014

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Researchers use neutrons, simulations to examine soil carbon

PhysOrg 3/31

Carbon dioxide in the atmosphere may get the lion's share of attention in climate change discussions, but the biggest repository of carbon is actually underfoot: soils store an estimated 2.5 trillion tons of carbon in the form of organic matter.

"The combined amount of carbon in vegetation and the atmosphere is only half of the carbon stored in soils," said Melanie Mayes of ORNL's Environmental Sciences Division. "How quickly that carbon moves in and out of soils is one of the big uncertainties in modeling the carbon cycle."

With an eye on the big picture, Mayes and her colleagues are taking a closer look at soil carbon by studying nanoscale interactions between organic matter and minerals in soil. The team's novel combination of neutron analysis and supercomputer simulations is providing experimental and theoretical data that challenge long-held assumptions in soil science.


Multiphysics Simulations Transmuting Designs for Safer Nuclear Power 1/7

Like the rest of the US's nuclear research reactors, Oak Ridge National Lab's (ORNL) high flux isotope reactor (HFIR) is moving from high-enriched uranium (HEU) fuel to low-enriched uranium (LEU). As such, the safety of the system must be assessed to incorporate the changes in fuel properties and the subsequently modified fuel plate.

Due to the recent growth in multiphysics, fluid-structure dynamics calculations can be coupled using a fluid-structure interaction (FSI) solver. The FSI solver is the key to the analysis of the HFIR system. Due to a built-in fully coupled FSI solver, and implicit solution capabilities, ORNL chose COMSOL to obtain their stable and precise solution.

Comprehensive phonon "map" offers direction for engineering new thermoelectric devices

R&D Magazine 1/9

If you've ever been stuck in traffic on a hot, sunny afternoon, you might have noticed the rippling effect caused by the release of even hotter exhaust fumes. If so, you've watched opportunity drift away.

Automobiles, power plants, laptops and many other machines produce heat when they operate. Waste heat is an unavoidable energy loss, a tradeoff in order to produce the kind of energy for which the machine is intended. However, this heat could be partly recycled into electrical energy through thermoelectric technology, which converts a temperature difference into an electric voltage.

To understand how to design better thermoelectric materials, researchers are using neutron scattering at the Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR) at the U.S. Dept. of Energy (DOE)'s Oak Ridge National Laboratory (ORNL) to study how silver antimony telluride is able to effectively prevent heat from propagating through it on the microscopic level. Heat in materials is carried by quantized sound waves, known to scientists as phonons. By mapping the phonons and their interactions with the atomic architecture of silver antimony telluride, researchers in ORNL's Quantum Condensed Matter and Materials Science groups discovered that a complex structure of nanoscale domains improved the thermoelectric properties of this compound.

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