CRIIRAD report N°18-21 Valence, February 16th 2018 Ru-106 / Mayak Commission de Recherche et d’Information Indépendantes sur la Radioactivité 29 cours Manuel de Falla / 26000 Valence / France . 33 (0)4 75 41 82 50 / [email protected] Contamination with ruthenium 106 Results of soil tests carried out by the CRIIRAD laboratory in the environment of the Mayak nuclear site Editor: Bruno CHAREYRON, nuclear physics engineer, director of the CRIIRAD laboratory. Contact : [email protected] 1 / Context: need to document the "Mayak" hypothesis Following the detection of ruthenium 106 in the air of about 30 countries from late September to mid- October 2017, the origin of the source is still debated. Among the many assumptions, that of an "incident" on the nuclear site "Mayak" was considered by CRIIRAD in October1 and remains one of the strongest. This nuclear site is located in Russia, in the sector pointed by the modelizations of several institutes (even if it is not located in the most probable zone resulting from modelizations published on November 9th by the French IRSN and November2 10th by Ukrainian scientists). Given the extent of atmospheric contamination, the release of ruthenium 106 was necessarily very high. In its communication3 of November 9th, 2017, the IRSN for its part gave an estimate of 100 to 300 TBq or 100 000 to 300 000 billions becquerels. It is unlikely that such a large release will come from a facility designed to produce ruthenium 106 for medical purposes. The Mayak site is engaged in the reprocessing of spent fuel and the vitrification of highly radioactive waste, which leads to the regular release4 of ruthenium 106 to the atmosphere (2.23 billion becquerels of Ru-Rh106 in 2015 according to the annual report of the Mayak site). In the case of accidental releases in September 2017, it seems that only isotopes of ruthenium are involved. Uncontrolled releases involving only ruthenium have already occurred at similar facilities, for example, in 2001, at two vitrification plants at the spent fuel reprocessing plant at La Hague in France. During certain stages of treatment of highly radioactive solutions resulting from the dissolution of irradiated fuels, ruthenium is indeed in gaseous form (RuO4) which can easily, in the event of incidents, be massively released into the atmosphere, without other radioactive substances being released at the same time (in any case in such large quantities). RuO4 is not stable in air and decomposes to ruthenium dioxide (RuO2), in the form of very fine solid particles. 1 http://balises.criirad.org/pdf/cp_criirad_17-10-11_ru106-air.pdf 2 https://www.linkedin.com/pulse/detection-ruthenium-106-2017-meteorological-analysis-sources-ivan/ 3 http://www.irsn.fr/FR/Actualites_presse/Actualites/Pages/20171109_Detection-Ruthenium-106-en-france-et-en- europe-resultat-des-investigations-de-l-IRSN.aspx#.WoQGCXzkV8w 4 In the context of "chronic" releases from the Mayak site, ruthenium 106 is not the dominant element in terms of rejected activity. According to 2015 official figures, releases of radioactive gases (argon 41, krypton 88, xenon 135) were 25,000 times higher. Ruthenium 106 / Mayak ? CHAREYRON - CRIIRAD 1 / 10 In 2017, the Mayak site obviously encountered technical difficulties pointed out by Nadezda Kutepova in October 2017. Since then, other clues have supported the "Mayak" hypothesis: The international commission5 of inquiry set up by Russia, validated, at its first meeting, on 31 January 2018 in Moscow, the order of magnitude6 of the accidental release of ruthenium 106 at a value of 100 TBq, ie 100 000 billion Becquerels. The technical difficulties encountered at the Mayak site were confirmed by the fact that the manufacturer told its customers, at the end of December, that it would not be able to fulfill a delivery contract for a highly radioactive cerium 144 source. This information was revealed by the Italian press and the French newspaper Le Figaro on 2 February. However, the manufacture of this source requires the reprocessing of spent fuel relatively "fresh". The international commission set up by Russia concluded that the ruthenium discharge, at the end of September 2017, corresponded to "fresh" spent fuel. It is based on the Ru 106 / Ru 103 isotopic composition measured7 in air in Austria, Czech Republic and Sweden. On the other hand, the Russian authorities claim that the inspections carried out on the Mayak site found no malfunction compared to normal technological processes. In addition, the results of ruthenium 106 air contamination analysis around Mayak, published by the Russian agency Rosguidromet, are comparable to those recorded in Romania and Ukraine. 2 / Objectives of the controls carried out by CRIIRAD Since October 2017, CRIIRAD has been trying to obtain samples of the surface layer of soils around nuclear sites in Russia that may be responsible for releases of ruthenium 106, especially around Mayak. Regarding the Mayak site, the CRIIRAD objectives were: Have independent measurements of ruthenium 106 fallout levels in the vicinity of the facility. Indeed, the ruthenium 106 fallout levels around Mayak, published by the Russian agency Rosguidromet8, did not show "strong fallout" (a few hundred Becquerels per square meter), and indicated a level of atmospheric contamination much lower than the one highlighted in Romania. CRIIRAD indicated in press releases9 dated 21 and 22 November 2017 that these results did not correspond to "extremely high" levels, but were of the same order of magnitude as those recorded in Romania, and could not be used to "Prove" that Mayak was the source of the discharge. Check current health risk levels for the local population around Mayak due to fallout. Half-life of ruthenium 106 is indeed relatively long (it takes a little more than a year for its radioactivity to be divided by two). Performing controls is important, including several months after the fallout, even though the measurements are more and more difficult to perform and interpret as you wait. Beyond the question of ruthenium 106, check the level of residual soil contamination around this site which has been the subject of serious accidents10 with massive releases to the atmosphere, particularly in 1957 and 1967. 5 http://en.ibrae.ac.ru/newstext/885/ 6However, the commission did not specify why it chose the low range of the IRSN estimate. 7See page 7 of http://www.irsn.fr/FR/Actualites_presse/Actualites/Documents/IRSN_Report-on-IRSN- investigations-of-Ru-106-in-Europe-in-october-2017.pdf 8 Rosguidromet Monthly Report for September 2017 http://www.criirad.org/accident-et- pollutions/X0%20byulleten_rorf_09_2017.pdf 9 http://www.criirad.org/accident-et-pollutions/2017-11-21_cp_mise%20au%20point_1.pdf and http://www.criirad.org/accident-et-pollutions/2017-11-22_cp_mise%20au%20point_2.pdf 10 http://www.criirad.org/installations-nucl/Mayak/CRIIRAD_Mayak_Kyshtym_Tcheliabinsk.pdf Ruthenium 106 / Mayak ? CHAREYRON - CRIIRAD 2 / 10 The realization of independent controls was all the more useful as the communication of the first Russian commission of inquiry raised many questions mentioned in the CRIIRAD statement11 of 20 December 2017. 3 / A preliminary campaign on the west of Mayak 3.1 / Measurements west of Mayak Not having sufficient means to carry out a real cartography of the soil contamination around Mayak, the efforts were carried out within the framework of this preliminary work, on the west of the nuclear site and this for several reasons: The ruthenium-106 measurements published by Rosguidromet (air contamination and / or fallout) provided data on stations located from north-east (Metlino) to the south (Novogornyy, Argayash), so it was a priority to carry out controls on other parts of the territory around Mayak. Contamination with ruthenium 106 (regardless of the exact source), moved westward as it reached Europe. In the hypothesis that Mayak is at the origin of the discharge, it was therefore logical to control in priority the sector located in the west. It should be noted, however, that the simulations performed by CRIIRAD show that, in the event that the accidental releases occurred in Mayak, depending on the dates and times, the contaminated plumes could have moved first in other directions, especially in a northeasterly direction, before turning southwest. Most of the population near the Mayak site lives in the west, in the Forbidden City of Oziorsk, and in Kyshtym, so it was a priority to check the fallout levels in these areas. Furthermore, with regard to the contamination in 1957 (so-called "Kyshtym" accident) and 1967 (highly radioactive dust dispersed by winds from the shores of Lake Karatchaï), the official documents indicate that the most important fallout is intervened in the northeast. Numerous studies attest to the severity of residual contamination in these areas (see, for example, measurements taken in 2008 by CRIIRAD in Golubinka12, about 30 km northeast of Mayak). On the other hand, there are few independent measurements in the west. 3.2 / A very preliminary work The objective of CRIIRAD was to work in successive stages. If these tests revealed a high level of ruthenium106 contamination, this would provide evidence of Mayak's liability. If not, additional sampling should be done in additional angular areas. This soil analysis campaign is therefore only a first step, especially since, in the hypothesis of time-limited discharges, the trajectory of contaminated plumes at the local level is likely to be limited to a very small angular sector. The most intense fallout on the ground, which depends in addition to any precipitation (rain or snow) may therefore affect a restricted band. The realization of some samples of soil is not enough to cover 360 ° around the site. It would be necessary to cover all the angular sectors and at different distances from the supposed source term. 3.3 / Difficulties encountered It is necessary to insist here on the difficulties met to realize these preliminary surveys: Impossibility of approaching within 14 kilometers of Mayak due to access restrictions imposed by the Russian authorities (no-go zone).