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

Masson, O. and Steinhauser, G. and Zok, D. and Saunier, O. et al.

Proceedings of the National Academy of Sciences

2019

10.1073/pnas.1907571116

National Academy of Sciences

A massive atmospheric release of radioactive 106Ru occurred in Eurasia in 2017, which must have been caused by a sizeable, yet undeclared nuclear accident. This work presents the most compelling monitoring dataset of this release, comprising 1,100 atmospheric and 200 deposition data points from the Eurasian region. The data suggest a release from a nuclear reprocessing facility located in the Southern Urals, possibly from the Mayak nuclear complex. A release from a crashed satellite as well as a release on Romanian territory (despite high activity concentrations) can be excluded. The model age of the radioruthenium supports the hypothesis that fuel was reprocessed <=2 years after discharge, possibly for the production of a high-specific activity 144Ce source for a neutrino experiment in Italy.In October 2017, most European countries reported unique atmospheric detections of aerosol-bound radioruthenium (106Ru). The range of concentrations varied from some tenths of {\textmu}Bq{\textperiodcentered}m-3 to more than 150 mBq{\textperiodcentered}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 {\textdegree}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.

0027-8424

https://www.pnas.org/content/early/2019/07/25/1907571116

https://www.pnas.org/content/early/2019/07/25/1907571116.full.pdf