NSUF - Nuclear Science User Facilities

Timothy Lach

Profile Information
Name
Dr. Timothy Lach
Institution
Oak Ridge National Laboratory
Position
R&D Staff Member
Affiliation
TMS, ANS
h-Index
17
ORCID
0000-0002-4745-4179
Biography

Tim is an R&D staff scientist in the Nuclear Energy Materials Microanalysis group. He joined Oak Ridge National Laboratory as an associate research scientist in the Materials Science and Technology Division in February 2020. Previously, he was a research scientist in the Reactor Materials and Mechanical Design group in the Nuclear Sciences Division at Pacific Northwest National Laboratory. His research interests focus on the characterization and testing of advanced nuclear materials for fission/fusion energy and spallation neutron applications. In particular, he uses analytical electron microscopy (SEM and TEM) and atom probe tomography (APT) in conjunction with properties testing to elucidate processing-microstructure-property-performance relationships in materials exposed to extreme environments. He is an extensive user of the Low Activation Materials Development and Analysis laboratory (LAMDA) and the Center for Nanophase Materials Sciences (CNMS).

Ph.D. 2016, Materials Science and Engineering, University of Illinois at Urbana-Champaign

B.S. 2010, Materials Science and Engineering, The Ohio State University.

Expertise
APT, Electron Microscopy, FIB, Nuclear Structural Materials, Precipitation, Radiation, STEM, TEM
Publications:
"Characterization of the microstructure of yttrium hydride under proton irradiation" Stephen Taller, Fabian Naab, Takaaki Koyanagi, Timothy Lach, Journal of Nuclear Materials Vol. 606 2025 Link
High moderation per unit volume solid moderator materials like yttrium hydride (YHx) are necessary for compact nuclear microreactors. However, the phase stability and hydrogen transport processes of YHx under high-temperature irradiation are largely unknown. Proton irradiation was conducted on YHx at 300 °C and 580 °C to 0.2 dpa using 1 MeV or 2 MeV protons in a high-vacuum environment. The hydrogen concentration was determined before and after irradiation using elastic recoil detection analysis, and microstructural evolution was examined via post-irradiation scanning transmission electron microscopy and Raman spectroscopy. Dislocation loops and cavities were observed in all conditions; their distribution was correlated with the bombarding proton energy and ion irradiation temperature. This work revealed that hydrogen retention is proportional to the formation of traps for hydrogen gas atoms and identified pathways for hydrogen release. The relative contributions of bulk or fast diffusion paths, such as grain boundaries, delamination boundaries, and stacking faults are discussed; the primary mechanisms of hydrogen loss are likely based on diffusion, ruling out artefacts of the experimental design. The study suggests proton irradiation may be a strong surrogate to study hydrogen transport in hydride moderator materials under irradiation.

About Us

The Nuclear Science User Facilities (NSUF) is the U.S. Department of Energy Office of Nuclear Energy's only designated nuclear energy user facility. Through peer-reviewed proposal processes, the NSUF provides researchers access to neutron, ion, and gamma irradiations, post-irradiation examination and beamline capabilities at Idaho National Laboratory and a diverse mix of university, national laboratory and industry partner institutions.

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