Nicolas (Nic) Uhnak joined Pacific Northwest National Laboratory (PNNL) in 2016 and is currently a radiochemist within the Radiochemistry group of the National Security Directorate.

Uhnak earned his PhD in inorganic chemistry from Washington State University, where his work was focused on developing actinide selective complexants for use in late-stage used nuclear fuel reprocessing. He joined PNNL shortly after graduating as a National Technical Nuclear Forensics Center Postdoctoral Fellow working on radiochemical separations for nuclear forensics.

Though his research interests are broad, most of his interests continue to be in nuclear forensics, where he currently leads the PNNL nuclear physics portion of a multi-national laboratory venture aimed at improving nuclear data for fission and activation products leveraging several unique neutron sources, as well as developing materials or processes for radiochemical separations to remove or isolate high impact radioisotopes from mixed activation and fission product matrices.

Research Interest

  • Actinide and Analytical Chemistry
  • Alpha and Gamma Spectrometry
  • Inorganic Chemistry
  • Nuclear and Radiochemistry
  • Nuclear Magnetic Resonance Spectroscopy
  • Organic Synthesis
  • Rare Earths
  • Separations Chemistry


  • PhD in inorganic chemistry, Washington State University
  • BS in chemistry, Boise State University

Affiliations and Professional Service

  • American Association for the Advancement of Science, Nov. 2015 - Present
  • American Nuclear Society, Oct. 2015 - Present
  • American Chemical Society, Aug. 2011 - Present

Awards and Recognitions

  • Outstanding Performance Awards, 2023
  • Recognized for Excellent Situational Awareness by PNNL’s Security Operations Center, 2023
  • Integrity Award for the Nuclear, Chemical, and Biological Technology Division, 2022



  • Arnquist, I.J., Bunker, R., Dohnalek, R., Ma, R., Uhnak, N.E. Exploration of methods to remove implanted 210Pb and 210Po contamination from silicon surfaces. Nucl. Instr. Meth. A 1048, 2023, 168008.
  • Graham, T.R., Gartman, B.N., Bautista, A., Irwin, L.E.I., Shelby, E.J., Saunders, D.L., Johnson, T.J., Murphy, M.K., Uhnak, N., Ritzmann, A.M., Bowen, J.M. Spectroscopic features of dissolved iodine in pristine and gamma-irradiated nitric acid solutions. J. Mole. Liq. 387, 2023, 122631.
  • Warzecha, E.J., Herman, S.M., Arnold, E.S., RisenHuber, M.D., Uhnak, N.E., Lawler, B.M., and Seiner, B.N. Determination of Distribution Coefficients of 41 Elements in Nitric and Hydrochloric Acids for Actinide Resin. J. Radioanal. Nucl. Chem. 332, 2023, 2785-2791.


  • Arnold, E.S., Uhnak, N.E., Schroder, J.M., Metz, L.A., Beck, C.L. The Impact of Silver on Uranium Quantification by Kinetic Phosphorescence Analysis. J. Radioanal. Nucl. Chem. 331, 2022, 5167-5172.
  • Hubbard, L., Reed, C., Uhnak, N., Sumner, R., Cell, T., Kinney, E., Smith, N., Allen, C., Foxe, M., Carman, A. Luminescent Silica Microagglomerates, synthesis, and Environmental Testing. MRS Comm. 12(1), 2022, 119-123. Cover Article
  • Pierson, B.D., Archambault, B.C., Greenwood, L.R., Haney, M.M., Cantaloub, M.G., Hagen, A.R., Herman, S.M., Uhnak, N.E., Bowen, J.M., Estrada, J.H. Alpha/beta-gated gamma–gamma spectroscopy of mixed fission products for trace analysis. J. Radioanal. Nucl. Chem. 331, 2022, 5453–5467.


  • Uhnak, N.E., K.L Nash. Functionalized Dipicolinic Acid Derivative as TALSPEAK-MME Stripping Agents. Solv. Extr. Ion Exch. 39(1), 2020, 18-37.
  • Uhnak, N.E., K.L Nash. Pyridine Based Polyaminocarboxylate Ligands For Actinide Lanthanide Separations. Solv. Extr. Ion Exch. 38(4), 2020, 401-416.


  • Morrison, S.S., Morrison, E.C., Uhnak, N.E., Wittman, R.S., Seiner, B.N. Isolation of Au and Pt Radionuclides from Deuteron-Irradiated Platinum Using TBP Resin. J. Radioanal. Nucl. Chem. 319, 2019, 679-686.
  • Uhnak, N.E., S.S. Morrison, M.J. O’Hara, N.J. Murray, M. Bartsch, H.S. Edwards, J.W. Grate. Manipulation of Mass Transport Rates using Bead-in-a-tube Method. J. Chroma. A. 1586(8), 2019, 139-144.


  • Uhnak, N.E. Prediction of Trivalent Actinide Amino(poly)carboxylate Complex Stability Constants Using Linear Free Energy Relationships with the Lanthanide Series. Sep. Sci. Tech. 53, 2018, 725-733.
  • Uhnak, N.E., S.S. Morrison, S.M. Morley, A.C. Edwards, E.C. Finn, B.N. Seiner. Cu Metal Based Radiotellurium Separation from Simulated HEU Process Streams. J. Radioanal. Nucl. Chem. 317, 2018, 519-526.