Airborne concentrations and chemical considerations of radioactive ruthenium from an undeclared major nuclear release in 2017.

In October 2017, most European countries reported unique atmospheric detections of aerosol-bound radioruthenium (106Ru). The range of concentrations varied from some tenths of µBq·m-3 to more than 150 mBq·m-3 The widespread detection at such considerable (yet innocuous) levels suggested a considerable release. To compare activity reports of airborne 106Ru with different sampling periods, concentrations were reconstructed based on the most probable plume presence duration at each location. Based on airborne concentration spreading and chemical considerations, it is possible to assume that the release occurred in the Southern Urals region (Russian Federation). The 106Ru age was estimated to be about 2 years. It exhibited highly soluble and less soluble fractions in aqueous media, high radiopurity (lack of concomitant radionuclides), and volatility between 700 and 1,000 °C, thus suggesting a release at an advanced stage in the reprocessing of nuclear fuel. The amount and isotopic characteristics of the radioruthenium release may indicate a context with the production of a large 144Ce source for a neutrino experiment.

The workshop on signatures of medical and industrial isotope production - WOSMIP; Strassoldo, Italy, 1-3 July 2009.

Radiopharmaceuticals make contributions of inestimable value to medical practice. With growing demand new technologies are being developed and applied worldwide. Most diagnostic procedures rely on (99m)Tc and the use of uranium targets in reactors is currently the favored method of production, with 95% of the necessary (99)Mo parent currently being produced by four major global suppliers. Coincidentally there are growing concerns for nuclear security and proliferation. New disarmament treaties such as the Comprehensive Nuclear-Test-Ban Treaty (CTBT) are coming into effect and treaty compliance-verification monitoring is gaining momentum. Radioxenon emissions (isotopes Xe-131, 133, 133m and 135) from radiopharmaceutical production facilities are of concern in this context because radioxenon is a highly sensitive tracer for detecting nuclear explosions. There exists, therefore, a potential for confusing source attribution, with emissions from radiopharmaceutical-production facilities regularly being detected in treaty compliance-verification networks. The CTBT radioxenon network currently under installation is highly sensitive with detection limits approaching 0.1 mBq/m³ and, depending on transport conditions and background, able to detect industrial release signatures from sites thousands of kilometers away. The method currently employed to distinguish between industrial and military radioxenon sources involves plots of isotope ratios (133m)Xe/(131m)Xe versus (135)Xe/(133)Xe, but source attribution can be ambiguous. Through the WOSMIP Workshop the environmental monitoring community is gaining a better understanding of the complexities of the processes at production facilities, and the production community is recognizing the impact their operations have on monitoring systems and their goal of nuclear non-proliferation. Further collaboration and discussion are needed, together with advances in Xe trapping technology and monitoring systems. Such initiatives will help in addressing the dichotomy which exists between expanding production and improving monitoring sensitivity, with the ultimate aim of enabling unambiguous distinction between different nuclide signatures.

Notes on radioxenon measurements for CTBT verification purposes.

The verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) includes, beside three different waveform techniques, global monitoring of radioactive aerosols and noble gases. The noble gases are difficult to contain for the illicit tester and are therefore of particular importance to identify signals from underground or underwater nuclear tests. Several isotopes of xenon are sufficiently produced in fission and a few have suitable half-lives and radiations to be detected. These are (131m)Xe, (133m)Xe, (133)Xe and (135)Xe and they have been selected for continuous monitoring. Four different systems have been developed to sample and measure them. Three of them use cryogenic or room-temperature gas chromatography processes and one a membrane technology. One measures by gamma spectroscopy, two by beta-gamma coincidence spectroscopy and one by beta-gated gamma spectroscopy. These systems are now undergoing trials at worldwide locations in the so-called International Noble Gas Experiment (INGE). In parallel, specific analytical software is being developed to examine the spectra produced by these different systems. This paper presents results from data acquired both from regions having a high radioxenon background and from remote low background stations.