The whole picture: BNL researchers combine CT technologies to study nuclear materials

Often, multiple tests need to be performed to make an accurate diagnosis. This can be the case for illnesses, a strange rattle in a car, computer troubleshooting-and examining nuclear materials.

Rather than wait the days or even weeks it would take to run such tests one after the other, a team at Brookhaven National Library has developed a way to get multiple images concurrently, shortening the testing time to just hours.

Their achievement, recently published in the Journal of Synchrotron Radiation, combines four types of computed tomography (CT) scans that can reveal the internal structure, chemical makeup, and physical shape of a material at the same time.

In-depth understanding: Knowing how the properties of materials change when exposed to radiation, corrosion, high temperatures, and mechanical stress is key for nuclear engineering, whether the design is for fuel, reactor components, or storage.

"Exposure to radiation alters materials and changes their structure, introducing defects and redistributing elements throughout the material," explained Simerjeet Gill, deputy chair of BNL's Nuclear Science and Security Department. "By conducting these four techniques simultaneously, we can pinpoint exactly where those chemical changes occurred and connect them to how the material's strength and brittleness have changed. That structure-composition-property relationship is what we want to understand when studying nuclear materials."

According to Mehmet Topsakal, the paper's lead author and a materials scientist at BNL, "Nuclear reactors are designed to operate for several decades, but we cannot wait that long to understand how materials will hold up in extreme nuclear environments."

To test their experimental setup, the researchers made a sample comprising "a little bit of everything," as Topsakal described it, including various types and sizes of metal wires and different powder materials.

The set-up: High energy X-rays-also called hard X-rays-are needed to penetrate and create imaging for the dense materials that make up nuclear reactors and their fuels.

The researchers built their experimental imaging device at BNL's X-ray Powder Diffraction (XPD) beamline of the National Synchrotron Light Source II (NSLS-II). According to XPD's lead beamline scientist, Sanjit Ghose, "NSLS-II is one of a few facilities in the world for studying dense, high-atomic-number materials, like nuclear materials, using an all-in-one method."

Four types of imaging techniques were used to build a 3D picture of the researchers' sample:

• X-ray absorption CT, to reveal the physical structure, including variable density, voids, and cracks.
• X-ray fluorescence CT, to examine the sample's chemical elements.
• X-ray diffraction CT, to capture organized, crystalline materials.
• Pair distribution function CT, to capture disordered, amorphous materials.

Describing the new setup as an "order of magnitude improvement," Ghose said it will enhance efficiency "by increasing the number of researchers who can come use this tool and the amount of data we can generate."