PNNL

Andrew Ritzmann joined Pacific Northwest National Laboratory (PNNL) in 2017 after earning a bachelor’s degree in chemical engineering from Cornell University (2005) and a PhD in chemical engineering from Princeton University (2016). Ritzmann previously worked as a quality assurance engineer in the software industry and as a high school physics teacher. His research has involved the use of a diverse set of computational techniques to analyze atomic-scale phenomena, laboratory experiments, and industrial processes. In prior research, he applied density functional theory to oxygen transport in solid oxide fuel cell materials to understand how chemical composition influences cathode performance. At PNNL, Ritzmann works on a diverse set of projects, including modeling the adsorption of iodine onto carbon surfaces, the transport of xenon through liquids and sorbent materials, liquid-liquid extraction processes, spent fuel dissolution, and the thermodynamics of high ionic strength solutions. His research is related to nuclear nonproliferation, nuclear forensics, and radioisotope production.

• Chemical engineering
• Chemical separations
• Chemical thermodynamics
• Computational modeling
• Thermodynamic modeling
• High-performance computing (HPC)
• Computational fluid dynamics (CFD)
• Density functional theory

• PhD in chemical engineering, Princeton University
• MA in chemical engineering, Princeton University
• BS in chemical engineering, Cornell University

• American Chemical Society

2025

• Dinpajooh M., G.L. Hightower, R.E. Overstreet, L.A. Metz, N.J. Henson, N. Govind, and A.M. Ritzmann, et al. 2025. "On the Stability Constants of Metal-Nitrate Complexes in Aqueous Solutions." Physical Chemistry Chemical Physics 37, no. 18:9350-9368. PNNL-SA-205148. doi:10.1039/D4CP04295F
• Torres R.D., B.J. Riley, L.R. Hare, M.A. Hall, S.K. Johansen, A.M. Ritzmann, and M.Y. Toyooka. 2025. Technical Assessment of Off-Gas System Technologies for Potential Use in Molten Salt Reactors. PNNL-37170. Richland, WA: Pacific Northwest National Laboratory. Technical Assessment of Off-Gas System Technologies for Potential Use in Molten Salt Reactors

2024

• Doll C.G., J.C. Hayes, A.M. Ritzmann, and K.L. Silvers. 2024. Abatement Case Study. PNNL-35949. Richland, WA: Pacific Northwest National Laboratory. Abatement Case Study

2023

• Graham T.R., B.N. Gartman, A. Bautista, L. Irwin, E.J. Shelby, D.L. Saunders, and T.J. Johnson, et al. 2023. "Spectroscopic features of dissolved iodine in pristine and gamma-irradiated nitric acid solutions." Journal of Molecular Liquids 387. PNNL-SA-178034. doi:10.1016/j.molliq.2023.122631
• Hubbard L.R., A.M. Ritzmann, J.H. Wahl, J.E. Shilling, C.Z. Soderquist, D.G. Abrecht, and N.P. Smith. 2023. "Optical Modeling of a Radioisotope Atmospheric Chamber." MRS Communications 13. PNNL-SA-164897. doi:10.1557/s43579-023-00337-2
• LaCount M.D., D.E. Meier, A.M. Ritzmann, S.E. Muller, R.A. Clark, E.C. Buck, and D. Abrecht. 2023. "Ab Initio Modeling and Thermodynamics of Hydrated Plutonium Oxalates." Journal of Nuclear Materials 583. PNNL-SA-178539. doi:10.1016/j.jnucmat.2023.154504

2021

• Bowen J.M., L.M. Arrigo, M.D. RisenHuber, N.E. Uhnak, B.M. Lawler, C.J. Allen, and A.M. Ritzmann, et al. 2021. Speciation Correlations between Uranium and Iodine. PNNL-32033. Richland, WA: Pacific Northwest National Laboratory. Speciation Correlations between Uranium and Iodine

2020

• Bilbrey J.A., C.M. Ortiz Marrero, M. Sassi, A.M. Ritzmann, N.J. Henson, and M. Schram. 2020. "Tracking the chemical evolution of iodine species using recurrent neural networks." ACS Omega 5, no. 9:4588-4594. PNNL-SA-148824. doi:10.1021/acsomega.9b04104
• Sassi M., A.M. Ritzmann, and N.J. Henson. 2020. "Consequences of 131I transmutation in gas phase radioiodine molecules and adsorbed on graphite surface." Journal of Physical Chemistry C 124, no. 39:21461-21466. PNNL-SA-153560. doi:10.1021/acs.jpcc.0c05928
• Stephenson D.E., P.H. Humble, A.M. Ritzmann, P.K. Thallapally, J.C. Hayes, and K.A. Wagner. 2020. Iodine Effects on Medical Isotope Producer Delay & Guard Bed Temperature and Performance in Support of NA-23 Program. PNNL-30456. Richland, WA: Pacific Northwest National Laboratory. Iodine Effects on Medical Isotope Producer Delay & Guard Bed Temperature and Performance in Support of NA-23 Program

2018

• Garrett K.E., A.M. Ritzmann, F.N. Smith, S.H. Kessler, R. Devanathan, N.J. Henson, and D.G. Abrecht. 2018. "First principles investigation of the structural and bonding properties of hydrated actinide (IV) oxalates, An(C2O4)2·6H2O (An = U, Pu)." Computational Materials Science 153. PNNL-SA-133111. doi:10.1016/j.commatsci.2018.06.033