A contamination with the ubiquitous radioactive fission product 137Cs cannot be assigned per se to its source. We used environmental samples with varying contamination levels from various parts of the world to establish their characteristic 135Cs/137Cs isotope ratios and thereby allow their distinction. The samples included biological materials from Chernobyl and Fukushima, historic ashed human lung tissue from the 1960s from Austria, and trinitite from the Trinity Test Site, USA. After chemical separation and gas reaction shifts inside a triple quadrupole ICP mass spectrometer, characteristic 135Cs/137Cs isotope signatures (all as per March 11, 2011) were obtained for Fukushima- (∼0.35) and Chernobyl-derived (∼0.50) contaminations, in agreement with the literature for these contamination sources. Both signatures clearly distinguish from the characteristic high ratio (1.9 ± 0.2) for nuclear-weapon-produced radiocesium found in human lung tissue. Trinitite samples exhibited an unexpected, anomalous pattern by displaying a low (<0.4) and nonuniform 135Cs/137Cs ratio. This exemplifies a 137Cs-rich fractionation of the plume in a nuclear explosion, where 137Cs is a predominant species in the fireball. The onset of 135Cs was delayed because of the longer half-life of its parent nuclide 135Xe, causing a spatial separation of gaseous 135Xe from condensed 137Cs, which is the reason for the atypical 135Cs/137Cs fractionation in the fallout at the test site.

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Radiometric or mass spectrometric analysis of the long-lived fission product 107Pd is notoriously difficult. We developed and optimized a chemical separation protocol for minute amounts of radiopalladium with a subsequent measurement by inductively coupled plasma triple quadrupole mass spectrometry with propane as the collision gas. This allows for detection limits of <2 ng of 107Pd/kg, which makes the method suitable for environmental samples with low levels of 107Pd. For testing of this method, a sample of sediment from the Chernobyl cooling pond was analyzed. Indeed, it could be shown that the cooling pond sediment exhibits a uniquely increased 107Pd/105Pd ratio (0.08 ± 0.02), thus strongly indicating detectable levels of 107Pd using this method.

On August 8, 2019, an explosion of a military missile occurred at the Nenoksa (also transcribed as Nyonoksa) Missile Test Center (Russian Federation). Russian authorities confirmed a release of radioactive material in the course of this incident, which fueled rumors that it could have involved a nuclear‐propelled missile of the Burevestnik/Skyfall type. In this study, our radioanalytical efforts are summarized searching for the “smoking gun” of the incident. These included the gamma‐measurements of air filters from two vessels that were in some proximity to the event as well as one Greek high‐volume air filter. In addition, we tested the hypothesis that radioactive 42Ar may have been used to operate a radiothermal generator. If the incident had released 42Ar, it may have become detectable by measuring characteristic gamma radiation emitted from a tank containing liquefied atmospheric argon. No traces whatsoever were found that could provide clues about the release. It is possible that the presumably small amounts of radionuclides released from either a small nuclear reactor or a powerful radionuclide source dispersed quickly over Russian territory to non‐detectable levels before reaching any of our assayed samples.