Author: Svilena Velcheva

The 27th anniversary  since the nuclear accident in the so-called “secret” city in Siberia was this week. The explosion at the Tomsk-7 nuclear processing facility dispersed large amounts of radioactivity over an area of ​​120 km2, exposing tens of thousands of people to elevated levels of radiation. Polluting the air, water and soil for decades to come. The Tomsk-7 accident is considered the most serious Russian nuclear accident after Chernobyl.

The story

Tomsk-7 was a “secret” center in Siberia until 1992, when it returned to its historical name Seversk. It houses several nuclear facilities for the large-scale production of plutonium and uranium for nuclear fuel and weapons, including spent fuel reprocessing. The closed city was home to about 100,000 workers and their families. One of the worst accidents in the history of the Russian nuclear industry occurred at the Tomsk-7 processing plant on April 6, 1993. On that day, workers poured nitric acid into a tank to separate plutonium from spent nuclear fuel. It is not clear whether the accident was caused by human or technical error. The lack of compressed air is thought to have caused the mixture of nitric acid, uranium and plutonium to overheat, reaching a critical temperature in just a few minutes. The ensuing explosion tore down walls on two floors of the complex, and the fire released about 250m of radioactive gas, 8.7kg of uranium and 500g of plutonium into the environment. This amounts to about 30 tera-becquerel (tera = trillion) beta- and gamma-emitters and about 6 giga-becquerel (giga = billion) plutonium-239. An area of ​​1500 m2 around the plant is heavily contaminated, while the radioactive release covers an area of ​​120 km. The Tomsk-7 explosion was ranked level 4 on the International Scale of Nuclear and Radiological Events (INES), comparable to the 1999 nuclear accident in Tokaymura, Japan.

Impact on health and the environment

Radioactive snowfall in the days after the disaster creates hotspots with radiation levels up to 30 µGy / h – approximately 100 times above normal background radiation. Soils in areas affected by radioactive waste show significantly elevated levels of cesium-137 and strontium-90. Cesium-137 can cause solid tumors and genetic defects when inhaled or ingested through food or water, while strontium-90 is a proven cause of leukemia.

With the help of foreign specialists, the initial cleaning operations managed to collect and remove about 577 g of plutonium from the area around Tomsk-7. Interestingly, only about 450 g of plutonium was present in the pool before the explosion, suggesting unregistered previous leaks from the facility. Even months after the explosion, snow samples continued to show elevated levels of radioactive isotopes such as plutonium, uranium, zirconium, ruthenium, cerium, niobium and antimony. According to the Norwegian environmental NGO Bellona, ​​about 30 major accidents have occurred at the Tomsk-7 nuclear facility, releasing about 10 grams of plutonium into the atmosphere each year. The organization also documents large amounts of nuclear waste from 50 years of plutonium production accumulated in the area of ​​the nuclear facility. Dumped in underground landfills or pumped into outdoor pools, they pose a constant threat to public health. In 2008, a study found elevated levels of plutonium and cesium-137 in soils and water samples, suggesting ongoing leaks.


Some reactors at Tomsk-7 were shut down in June 2008, following a 2003 agreement between Russia and the United States to phase out weapons-grade plutonium production. The reprocessing of spent fuel and the dumping of nuclear waste on the premises of the so-called Siberian Chemical Plant continue. Despite the detected elevated levels of plutonium, strontium, cesium and other radioactive particles in the soil and water, no significant medical studies have been conducted on the local population. In 2001, the Tomsk District Court ruled in the case of affected residents of the village of Georgievka against the Siberian Chemical Plant. The court ordered the company to pay each plaintiff $ 860 in damages. During the hearings, 14 of the 26 applicants died as a result of health compromised by the nuclear production, according to the Bellona Foundation.

Translator: Valentina Vagge


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