separation process for uranium and plutonium from
spent nuclear fuel. Variations of the process have and continue to find applications in many facilities such as
La Hague in the manufacture of MOX reactor fuel,
where reactor-grade plutonium is reused as fuel and likewise in the extraction of
weapons grade plutonium, in the legacy
B205 facility in Britain and the Mayak facility in Russia. While the release of the noble gas isotope
krypton-85 is routine during
nuclear reprocessing, the noble metal
ruthenium, which is generated in a
fission product yield rate of from 0.39% to 3.103% of every fission of a nucleus of uranium or plutonium respectively, is by contrast
generally in metallic form, with a high boiling point of in spent fuel. Owing to the
ionizing radiation environment of
spent fuel and the entry of oxygen, however,
radiolysis reactions can make the more volatile compound
ruthenium(VIII) oxide, which has a boiling point of approximately and is a strong oxidizer, reacting with virtually any fuel/
hydrocarbon. The use of a solution of
tributyl phosphate in the hydrocarbons
kerosene or
dodecane, is frequent – as part of the
nuclear reprocessing method known as
PUREX. Ru-106 has been accidentally released to the atmosphere through this pathway in the past, such as the
UK's B204 reprocessing incident in 1973, where 34 employees were exposed. With corrosion of the
fuel rod-cladding in the
MAGNOX-reactor, spent fuel pools (an issue in the British case, due to the selection of magnesium for the coating on the fuel rods), reprocessing needed to occur within a
few months at the B205 facility; most other facilities (like the French
La Hague) place the spent-fuel in
spent fuel pools for
about a decade, until the Ru-106, which has a half-life of ~ 1 year, has safely decayed into
Rh-106 and finally the stable
Pd-106. All attempts at PUREX to less aged spent-fuel need to take into account the presence of the oxidative and volatile ruthenium(VIII) oxide. assembly bundle being inspected before entering a reactor. Initially, there was no indication given for the source of these radioactive particles, apart from an October 2017 statement coming from German authorities estimating the source in the east, at more than from Germany. A later report from the German Federal Radiation Protection Service ruled in the South of the Urals and other potential locations. The
Federal Service for Hydrometeorology and Environmental Monitoring of Russia (Roshydromet) said that Ru-106 activity in St. Petersburg was at 115.4 μBq/m3 from October 2 to 6. The French
Institute of Radioprotection and Nuclear Security (IRSN) ruled out the emissions as coming from a nuclear reactor, estimating that it should have come either from a treatment site or from a center producing radioactive medicine. They estimated the source to be south of the Ural mountains, between the Urals and the Volga river, in Russia or
Kazakhstan. Roshydromet then issued a report describing a rise in beta activity of aerosols and surfaces at all monitoring posts in South Ural from September 25 to October 1, 2017. In two aerosol samples, an increase in Ru-106 activity was detected. On September 26 and 27, Ru-106 decay products were detected in the Republic of
Tatarstan. On September 27 and 28, high pollution levels of aerosols and surfaces was detected in Volgograd and Rostov-on-Don. In two aerosol samples from Chelyabinsk Oblast, 986- and 440-fold activity increases were measured, as compared to the preceding month. The
Mayak reprocessing and isotope production plant is widely suspected as the source. Authorities there and at
Rosatom, the Russian state company running the nuclear industry, have denied a link. On 21 November 2017, Russia reversed itself by confirming that a radiation spike was recorded at two monitoring facilities within of the plant. Russia states the published data is not sufficient to establish the air pollution source and government denies it has had any measurements or admissions of any incident. Domestic investigation within Russia is hampered by the problem that Mayak is in the walled-off
closed city of
Ozyorsk, which non-resident Russians are barred from visiting without special permission, and by government harassment of nuclear critics. In Russia prominent nuclear critics experience government raids, are accused on state TV of "exploiting the nuclear issue to foment revolution", and risk criminal prosecution on charges of incitement of hatred against nuclear energy employees. The French
Institute of Radioprotection and Nuclear Security (IRSN) provided a report to the committee in January 2018. The report concluded that the most likely source of the pollution is a spent fuel treatment facility located in a region between Volga and Ural. A possible reason for the release of radioactivity at Mayak PA might be an unsuccessful attempt to produce
cerium-144 for the European scientific project
Borexino. Mayak PA had agreed to deliver cerium-144 in fall 2016, but canceled the contract in December 2017. While the non-Russian members of the committee accepted the conclusions of IRSN's report, the Russian members maintain that an inspection by
Rostechnadzor of the Mayak PA facility in November 2017 showed no anomalies and a rare meteorological event may have transported the ruthenium-106 from somewhere else to the apparent region of origin. ==Timeline of European detection and public notice ==