Release of ruthenium-106 in the southern Ural Mountains

Air dust collector at the BfS monitoring station Schauinsland

The Russian meteorological service, Roshydromet, has now published the first report on its own detection of radioactive ruthenium-106 a few weeks ago. The findings cited in the report support the calculations by the German Federal Office for Radiation Protection (BfS). The BfS assumes that a rather large quantity of ruthenium-106 (Ru-106) was released around the end of September 2017. The place of release can now also be localised more precisely: Due to the prevailing wind direction at that time, areas to the west and to the south of the Ural Mountains can be excluded as potential release areas. In the first days of October, the BfS and the Federal Ministry for the Environment had already published measurement results showing low concentrations of ruthenium-106 in Germany, and had stated their findings about the potential release area.

According to a recent report from the Russian meteorological service, ruthenium-106 was observed at a total of four monitoring stations in the southern Ural Mountains, the northern Caucasus Mountains and along the Don River between 26 September and 1st October 2017. Other measuring stations additionally detected ruthenium-106 on the ground in this area and within this period of time. The values measured in the air were between 15 and 76 millibecquerel of Ru-106 per cubic metre. Similar values were measured in South East Europe (Rumania) a few days later. The values measured in Russia are very low amounts of radioactivity that do not pose a health hazard.

The reported measurement values are about a factor of 1000 higher than the normal background measurements, but only about 1 % of the maximum permitted concentrations of Ru-106 in air in Russia (4.4 Bq/m3 yearly average for work places).

The low amount of radioactivity does not pose a health hazard

Since 29 September 2017, several European trace monitoring stations have detected slightly increased levels of radioactivity in the air. Marginals amounts of ruthenium-106 were detected at a total of 7 measuring stations in Germany and at numerous measuring stations in other European countries (including Austria and Italy). The concentration of the radioactive substance observed in Germany was very low, between several microbecquerel and a few millibecquerel per cubic metre. This marginal amount of radioactivity does not pose a health hazard to the population.

The BfS performed backward calculations for the dispersion of radioactive particles in the atmosphere and was thus able to indentify areas where the release might have occurred. This analysis has led to the finding that the release most probably has occurred in the southern Ural Mountains. Following technical consultations with the BfS, the French radiation protection institute IRSN (Institut de Radioprotection et de Sûreté Nucléaire) reached similar conclusions. An accident in a nuclear power plant can be excluded as the source of ruthenium-106, since in this case many other radionuclides would have been detected.

Background information on ruthenium-106

Ruthenium-106 is a beta emitter. The daughter nuclide of ruthenium-106 is Rh-106 (rhodium-106), which is very short-lived and a gamma emitter so that the decay of ruthenium-106 always leads to the concurrent occurrence of beta and gamma radiation. Ruthenium-106 has a half-live of slightly more than a year (372 days). Ruthenium-106 is a fission product that is generated from uranium fission in a nuclear power plant.

Ruthenium-106 is used as a radioactive source in cancer therapy, in particular for the treatment of eye tumours. It cannot be fully excluded that ruthenium-106 is also used in "radioisotope thermoelectric generators" (RTG) that produce electricity for satellites. Ruthenium can also occur during the reprocessing of nuclear fuel elements.