Dr. Maxim Penkin passed away on November 30, 2021. At the time of his passing, Maxim was a Senior Safeguards Analyst with the Department of Safeguards at the International Atomic Energy Agency in Vienna, Austria. Maxim was an internationally-recognized expert in actinide chemistry and analytical techniques applied to nuclear safeguards. Since joining the Agency in 2003, Maxim made a very natural progression from analytical chemistry to information analysis. His ability to see beyond analytical results and understand the processes behind the numbers was just one of his remarkable talents. He introduced novel evaluation methodologies and modelling systems that significantly advanced the “verification toolbox” of the Department of Safeguards. For example, Maxim pioneered the systematic use of metallic impurities in uranium samples as a means of strengthening the Agency’s ability to verify States’ declarations from complex nuclear facilities. He was also persistent, and steered for many years a multilateral effort to produce an ultra-high-purity Pu-244 reference material, which will supply the nuclear safeguards and forensics communities for decades to come.

Maxim was not shy in his opinions, and many will remember his spirited participation at technical meetings and workshops. He was happy to challenge a conclusion, or to suggest a different interpretation, if he thought it would stimulate a debate. Yet he did so with respect and collegiality, and was polite and professional in all of his interactions. He enriched the safeguards community through his personal interactions, and was always the first to give credit to others for a good idea, or for a job well done. Maxim was trusted and held in extreme high regard by all who knew him, and his strength of character was clear to all. The international safeguards community will remember Maxim as a distinguished professional with a deep commitment to his work, but also as a courteous, gentle, and encouraging human being. He will be deeply missed by his colleagues and friends at the Agency, and beyond.

Upon kind approval by Prof. Dr. Zsolt Revay, Editor-in-Chief of Journal of Radioanalytical and Nuclear Chemistry, this Special Issue is published in his memory.