Abstract:
Interpreting the operating history of a nuclear reactor is a key question in safeguards, non-proliferation, and studies of environmental contamination. It can help answer questions related to the amount and quality of Pu or other radioactive materials that were produced during the irradiation. Traditional approaches to characterizing spent nuclear fuels rely either on radiometric counting and/or mass spectrometry, usually relying on chemical purification of the specific analyte to increase precision and accuracy. We present an approach using resonance ionization mass spectrometry (RIMS) to precisely analyze small, solid samples of spent nuclear materials to characterize isotope ratios of multiple elements simultaneously, without prior chemical separation. Dispensing with chemical separation avoids the addition of chemistry “blanks” (background), measuring multiple elements from the same volume allows the correlation of multiple irradiation characteristics, and working from small samples decreases the radioactive hazards in the laboratory.
We have applied Lawrence Livermore National Laboratory’s Laser Ionization of Neutrals (LION) instrument to several samples of spent nuclear material. This presentation will explain how we can analyze nearly any combination of 3 elements including U, Pu, Am, Sr, Rb, Mo, Zr, Nd, Ba, Cs simultaneously, during a single measurement, usually with enough material remaining to analyze the others in a subsequent analysis. We will show how connecting multiple isotope ratios across elements and comparing those analytical results to computational models provide an improved understanding of the operating history of a nuclear reactor.
Bio:
Brett Isselhardt is a Staff Scientist in the Trace Isotopic and Elemental Signatures Group at Lawrence Livermore National Laboratory. He earned his Ph.D. in Nuclear Engineering from the University of California at Berkeley and has a B.S. in Physics from Westmont College. His primary technical research focuses on applying Resonance Ionization Mass Spectrometry to characterizing nuclear material samples. With this goal, he established the LION (Laser Ionization of Neutrals) facility at LLNL in 2015, this facility now analyzes complex samples of nuclear material routinely. He has experience leading several small teams to perform cutting-edge R&D in materials signatures and new method development for application to nuclear forensics, nonproliferation, and national security. Over the last two years he has expanded his research efforts to modernize Atomic Vapor Laser Isotope Separation (AVLIS) methods for the domestic production of enriched isotopes.
