By Anastasia Teterevleva and Anna Ringstrom
MOSCOW/STOCKHOLM (Reuters) - Russia said on Monday it had detected no sign of a radiation emergency, after an international body reported last week that sensors in Stockholm had picked up unusually high levels of radioactive isotopes produced by nuclear fission.
The Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), which monitors the world for evidence of nuclear weapons tests, said last week one of its stations scanning the air for radioactive particles had found unusual, although harmless, levels of caesium-134, caesium-137 and ruthenium-103.
The isotopes were "certainly nuclear fission products, most likely from a civil source", it said. It tweeted a map showing where the material was likely to have originated, which included parts of several Baltic and Scandinavian countries as well as a swathe of western Russia.
Asked on Monday about reports that Russia could have been the source of a leak, Kremlin spokesman Dmitry Peskov said: "We have an absolutely advanced radiation levels safety monitoring system and there are no any emergency alarms."
"We do not know the source of this information."
The International Atomic Energy Agency asked member states over the weekend whether they had detected the isotopes, and "if any event may have been associated with this".
On Monday the IAEA said in a statement https://www.iaea.org/newscenter/pressreleases/iaea-receives-member-state-data-on-radioisotopes-detected-in-the-air-sees-no-human-health-risk that roughly 30 countries - including Finland, Sweden, Norway, the Baltic states, Britain, France and Germany - had informed it "that there were no events on their territories that may have caused the observed air concentrations". Russia was not one of them.
Finnish nuclear safety authority STUK said on Monday it had also found tiny amounts of nuclear particles in samples collected on its southern coast. But the concentrations were small enough that they could have been "derived from the normal operation or maintenance of nuclear reactors", it said.
Radiation protection expert Jan Johansson at the Swedish Radiation Safety Authority said the variations were extremely low and had no impact on radiation protection.
"What stands out here is the combination of these substances. That's not something we usually see," he told Reuters.
The TASS news agency, citing Rosenergoatom, a unit of the state nuclear company Rosatom, said over the weekend that Russia's two northwest nuclear power plants, in Leningrad and Kola, were working normally and radiation levels were unchanged.
(Reporting by Anastasia Teterevleva in MOSCOW, Francois Murphy in VIENNA, Anna Ringstrom in STOCKHOLM and Tarmo Virki in TALLINN; Writing by Katya Golubkova; Editing by Peter Graff and Giles Elgood)