National Nuclear Security Administration

Interns make a big difference with some very small creations at PNNL

September 4, 2018

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WSU student Jacqueline Reeve assembles an apparatus that bends the metal filament to hold samples for thermal ionization mass spectrometer analysis at PNNL.
WSU student Jacqueline Reeve assembles an apparatus that bends the metal filament to hold samples for thermal ionization mass spectrometer analysis.
The thermal ionization mass spectrometer (TIMS) at PNNL.
The thermal ionization mass spectrometer (TIMS).

Arnold Eng believes that small changes can make a big difference – especially in the world of nuclear safeguards. A researcher in NNSA’s Safeguards Internship Program at Pacific Northwest National Laboratory (PNNL), Eng turned to two teams of Washington State University (WSU) engineering and materials science students to design and fabricate the specialized equipment changes.

Eng works with a thermal ionization mass spectrometer (TIMS), one of the instruments that PNNL uses in the analysis of environmental samples for the International Atomic Energy Agency (IAEA) Network of Analytical Laboratories. These samples are collected by IAEA inspectors at nuclear facilities and sent to member laboratories like PNNL. The analytical results provide a powerful tool to help determine whether a country is complying with nonproliferation agreements.

One team of WSU students designed an apparatus to shape a metal ribbon into filaments to hold samples for TIMS analysis. A second team designed an enhanced device that pre-processes the batches of filaments. Each filament looks like a small staple with the top part supporting tiny – sub-picogram-sized – quantities of uranium, plutonium, and other nuclides.

Once filaments are welded to a post holder, the post holders are clipped into place in a device called a degas bench, which prepares the samples for analysis. Samples are then moved into the TIMS, heated by an electric current, and as the ions come off the filament, they are separated by the spectrometer for analysis.

Modifying the equipment may sound straightforward, but the thickness of the filament is 0.001 inch – about the diameter of a human hair. The specifications challenged the students to make the filaments V- or U-shaped to improve sample analysis, to modify the degas bench to better withstand high temperatures, and to present the filament posts in a consistent position for optimal pre-processing.

“We believe these projects will further improve TIMS capabilities,” Eng said.

PNNL engineer Patrick Valdez works to advise the students and ensure their projects address the equipment requests posed by PNNL researchers.

“Working to improve the efficiency of analysis with TIMS has focused the students’ efforts on the physical changes the samples and materials holding the samples undergo. Precision is very important. Developing a successful prototype is an iterative process—much like scientific research itself,” Valdez said.