A ruthenium mystery

RUSSIA ANNOUNCED ON 24 November that it would establish a commission to investigate detection of the isotope ruthenium-106 (Ru-106) across Europe in late September-early October.

Western reports cited Russia as the source despite Russian denials.

The Nuclear Safety Institute of the Russian Academy of Sciences (IBRAE) agreed to coordinate the work, while Rosatom promised “all necessary assistance” and undertook to publish the results.

The commission will include representatives of Russian and European scientific organisations and regulatory bodies, along with other nuclear specialists. It will conduct a new analysis of the monitoring data, and create and verify computer models to reconstruct propagation of the isotope alongside the movement of air masses. If necessary, it will conduct additional research and testing.

Earlier, Rosatom said all nuclear facilities in Russia were operating normally and that no radiation incidents had been recorded at those facilities, all of which undergo continuous monitoring.

Detection in Europe

Detection of the isotope was first made public by France and Germany.

A report by France’s Institut de Radioprotection et de Sûreté Nucléaire (IRSN) on 9 October said Ru-106 “had been detected in late September by several European networks involved in the monitoring of atmospheric radioactive contamination, at levels of a few milliBecquerels per cubic metre of air” (mBq/m³).

On 3 October, as soon as it became aware Ru-106 had been detected in the atmosphere in Italy, IRSN began regular analysis of the filters from its monitoring stations. Between 27 September and 13 October several stations recorded Ru-106 “in trace amounts”. The highest value (46 micro-Bq/m³) was recorded in Nice between 2 and 9 October. No Ru-106 was detected in France after 13 October. After 3 October other European stations confirmed the presence of Ru-106 “in the atmosphere of the majority of European countries”, IRSN said. The maximum level observed at the beginning of October was 100mBq/m³, steadily decreasing after 6 October. IRSN noted that the levels in Europe “are of no consequence for human health and for the environment”.

IRSN ruled out a release from a nuclear reactor, “which would result in the presence of other radionuclides”. It said the Ru-106 “is therefore to be found either in nuclear fuel cycle facilities or radioactive source production, or in the consequences of the re-entry into the atmosphere of a satellite equipped with a thermoelectric generator with ruthenium”.

The satellite hypothesis was investigated by the International Atomic Energy Agency (IAEA), which concluded that no satellite containing Ru-106 had fallen back to earth during the period.

IRSN carried out simulations to find the release zone, the quantity of ruthenium released, and the period and the duration of the release based on weather data from Météo France and 368 monitoring results from 28 European countries. The results suggested that the release was 100- 300TBq of Ru-106 and the most likely source was between the Volga and the Urals (Russia). IRSN said the release would have occurred during the last week of September.

The results were supported by comparison with simulations, that used contrasting methods and models. IRSN said its evaluation was in very good agreement with these peer organisations.

Similar information was reported from Germany’s Bundesamt für Strahlenschutz (BfS - Federal Office for Radiation Protection) using data from Deutscher Wetterdienst (DWD, Germany’s Meteorological Office) monitoring stations. Readings in Germany ranged from a few microBecquerel to 5mBq/m³. BfS also discounted an accident at a power plant, noting that Ru-106 is a radiation source in cancer therapy and can arise when nuclear fuel is reprocessed.

BfS agreed that backward calculations “suggest a high probability of a radioactive release in the Southern Urals, although other areas in the South of Russia cannot be ruled out”. It agreed that the release occurred during the last week of September.

Data collection by IAEA

IAEA collected information through its Unified System for Information Exchange in Incidents and Emergencies (USIE), which was published internally on 13 October, and later leaked to the public. IAEA said that, in early October, members states notified it that Ru-106 was being detected in high volume air samples. “The measured concentrations did not contain any other notable radionuclides and were at levels far below those requiring public protective actions”, the Agency said.

In response to a formal request from the Incident and Emergency Centre (IEC), 36 countries reported their monitoring results to IAEA. Data showed that measurements of Ru-106 in the air ranged from 10-5 to 10-2 Bequerels, with the highest measurement (145 mBq/m³) reported in Bucharest, Romania on 30 September. All these countries (and nine more that did not have monitoring capability) denied any events on their territories that would cause the spike in Ru-106,” the Agency said.

IAEA confirmed that Ru-106 is a fission product in used nuclear fuel and generated using accelerators and cyclotrons. It said the radiological significance of such Ru-106 concentrations in the air was “very low” and posed no risk to health, confirming similar assessments by IRSN and BfS.

It confirmed that the absence of other fission products in the samples ruled out release from a nuclear power plant, and it was not commonly used in medicine or RTGs.

Blame Russia

IAEA said it was unable to draw conclusions about location of the release “without factual reporting from a State of the origin of the release”.

The Western press suggested that responsibility could lie with the Mayak site in Ozersk (Urals), which undertakes nuclear fuel reprocessing and isotope production for Rosatom. But Rosatom denied any incident in Russia.

IAEA listed only two reports from Russia – one from Yekaterinburg taken on 1 October, showing no Ru-106, and one from St Petersburg on 4 October showing minimal levels.

However, on 21 November, Russia’s Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet) noted that it had earlier reported excessive Ru-106 levels in the samples collected on 25 September from the observation posts of Argayash and Novogorny in the Chelyabinsk Region, within the 100km zone around Mayak. These samples had 76.1mBq/m³ at Argayash and 52.3mBq/m³ at Novgorny (which is closer to Mayak). They exceeded the background of the previous month 986 and 440 times, respectively, so Roshydromet described them as “extremely high contamination”, although they were still well below notifiable levels.

Roshydromet said that on 26-27 September Ru-106 decay products were detected in Tatarstan. On 27-28 September, Volgograd and Rostov-on-Don recorded high contamination of aerosol and fallout samples. From 29 September to 3 October, Ru-106 was recorded in most European countries.

Roshydromet said the cloud was detected across southern Russia and then travelled to Europe, arriving in Italy before spreading north, as a result of unusual weather conditions – normally the air flow is from west to east but at this time air masses carried pollutants from the Southern Urals and southern Siberia to the Mediterranean and then to the north of Europe.

Roshydromet head Maxim Yakovenko said on 21 November that the increase in Ru-106 registered in Russia and other countries was thousands of times below permissible values. The concentration in Ukraine and Poland were comparable to those in Russia and in Romania it was 1.5-2 times higher than in Russia. “The published data does not allow us to establish the location of the pollution source”, he said.

Concerned by allegations of a “cover-up”, Yakovenko said Roshydromet had not withheld information. “We have taken account of the incorrect, and sometimes deliberately unfair, interpretation of our data on Ru-106 by some public organisations and the media. Roshydromet will change the way it submits reports in order to avoid ambiguity about the monitoring data. The tables will give data on the concentrations of detected pollutants in comparison with established maximum permissible concentrations (MPC),” he noted.

Yakovenko said monitoring data from 25 September to 6 October had been published on 13 October on the official websites of Roshydromet and its subordinate institutions, which are in the public domain. The data was also sent to the relevant executive authorities, he added. “Representatives of the media, interested organisations and citizens could have accessed this information more than a month ago,” he insisted.

The administration of the Chelyabinsk region administration held a briefing for the media on 20 October, where vice-governor Oleg Klimov, announced the presence of Ru-106 in samples taken by the Ural Department of the Hydrometeorological Service, Rosselkhoznadzor.

In a 21 November statement the Mayak Production Association denied any involvement in the Ru-106 release. Ru-106 could be released in two ways, Mayak said. One is if a fuel rod casing is compromised – but then dozens of other fragmentation radionuclides would have been detected.

Secondly, there could be a release during the production, use or recycling of Ru-106 sources. But, a typical ruthenium-106 source has an activity of 1-10Ci. Destroying such a source would see Ru-106 recorded at a distance of up to 500km. Increased background and strong radioactive contamination of the atmosphere would be recorded at the site of depressurisation of the source, the Mayak statement said.

“In 2017, there was no production of the ruthenium-106 sources at Mayak Production Association and emissions to the atmosphere were in the usual range. Radiation background is normal. We have done no separation of ruthenium-106 from spent nuclear fuel, and have not produced new Ru-106 sources in our company for many years now.” One eminent scientist based in Ozersk told NEI that he was certain there had been no radiation event at Mayak. “I would have known about it,” he said.

Rosatom said information on the level of radiation around Russia’s nuclear facilities is available in real time from the sensors of the Automatic Radiation Monitoring System and are available on the Russian Atom website: www.russianatom.ru

Russian scientists and engineers contacted by NEI admitted to being puzzled by the ruthenium mystery, which has become a major political issue. They pointed out that, even if there had been a local release in the Urals area,
the effects are unlikely to have been detected at such distances. Rosatom noted that increased concentrations of ruthenium-106 were observed in Europe at locations more than 3000 kilometres apart, and at almost the same time and concentration.