Russia has denied that its nuclear power stations in the north-west of the country were responsible for a mild leak of radiation detected in Scandinavia last week.
Rosenergoatom, the power-plant subsidiary of state-owned nuclear group Rosatom, said its installations near St Petersburg and Murmansk were operating normally.
“Aggregated emissions of all specified isotopes in the above-mentioned period did not exceed the reference numbers. No incidents related to release of radionuclide outside containment structures have been reported,” Rosenergoatom said, according to Tass news agency.
The International Atomic Energy Agency, the UN nuclear watchdog, said late on Saturday it had contacted member states seeking more information “and if any event may have been associated with this atmospheric release”.
The IAEA said it had received evidence from international monitoring systems of “elevated” levels of three radioactive isotopes in the Nordic region.
The IAEA’s technical directorate was notified by the Comprehensive Nuclear-Test-Ban Treaty Organization, which maintains independent monitoring systems around the world, that radioisotopes of caesium and ruthenium had been measured well above normal levels by a facility it runs in Sweden. The isotopes do not occur naturally.
Lassina Zerbo, executive secretary of the CTBTO, wrote on Twitter on Friday that its Swedish monitoring unit had detected three isotopes normally associated with nuclear fission that were “higher than usual levels (but not harmful for human health)”. The message included a map of the possible source of the radiation, stretching from north-western Russia across the Baltic to the North Sea.
Mr Zerbo later added in a second message: “These isotopes are most likely from a civil source. We are able to indicate the likely region of the source, but it’s outside the CTBTO’s mandate to identify the exact origin.”
Russia has a history of concealing radiation leaks. Most notoriously, Soviet authorities for weeks denied the true extent of the accident at Chernobyl in 1986, the world’s worst nuclear disaster.
More recently, it took Russian authorities several weeks in 2017 to acknowledge publicly a radioactive cloud containing ruthenium that was detected by France. The highest levels of ruthenium from the leak were found in Argayash, a village close to the Mayak nuclear fuel reprocessing plant in the southern Urals. Rosatom denied the facility was responsible.
The latest incident was first reported last week by agencies in Sweden, Finland and Norway. The Swedish Radiation Safety Authority said it detected “very low levels of the radioactive substances caesium-134, caesium-137, cobalt-60 and ruthenium-103” in early June. Its Finnish counterpart identified the same substances while the Norwegian agency picked up iodine-131.
The National Institute for Public Health and the Environment (RIVM) in the Netherlands on Friday said: “The combination of radionuclides may be explained by an anomaly in the fuel elements of a nuclear power plant.”
“RIVM has performed calculations to find out the source of the radionuclides. The calculations indicate that the nuclides come from the direction of western Russia. Determining a more specific source location is not possible with the limited data available.”
Western Russia has several nuclear facilities, including the vast Leningrad nuclear facility outside St Petersburg on the southern shore of the Gulf of Finland, which features four reactors of the same Soviet-era type as those at Chernobyl. Work is under way to upgrade the facility.
Russia also has operational civilian nuclear plants near Smolensk and Tver.
Finland and Sweden also operate active reactors in the potential zone of origin for the isotopes indicated by the CTBTO. The region is also home to Lithuania’s Ignalina facility, decommissioned in 2009 — as a condition for the country joining the EU — and reactors under construction in Belarus and Russia’s Kaliningrad enclave.