By Renfrey Clarke
MOSCOW — Russian officials have confirmed that plutonium salts were among the radioactive materials blasted into the atmosphere when a nuclear fuel reprocessing installation in western Siberia exploded on April 6. Although heavy snow brought the radioactive debris to earth relatively quickly, an area of at least 35 square kilometres of forest has been rendered uninhabitable — in effect forever.
The explosion occurred 28 km north-west of the large industrial city of Tomsk in an outlying plant of the Siberian Chemical Combine. The combine is centred in the town known as Tomsk-7.
Founded in the late 1940s as one of three major centres of the Soviet nuclear weapons manufacturing program, Tomsk-7 remains closed to foreigners, and during the Soviet era was so secret that despite having a population of more than 100,000, it was not marked on maps.
According to the Russian Greenpeace organisation, the plant at which the explosion occurred uses nitric acid to dissolve spent fuel rods from nuclear reactors, in order to extract uranium 238 and plutonium 239 for recycling. A preliminary report issued on April 9 by the State Nuclear Supervisory Committee blamed the accident on negligence by plant personnel. Experts of the committee have speculated that organic materials may have come in contact with nitric acid in a tank used for the extraction process, causing gases to be given off.
The plant director told the paper Izvestia that pressure built up rapidly in the tank, and that after six minutes an explosion blew off the concrete slab covering its top. Electrical systems short-circuited, starting a fire which burned for more than an hour. The roof and a wall of the building were destroyed. Plant workers were not evacuated, though one firefighter received a dose of radiation approaching his permitted annual exposure.
Fortunately for the 520,000 people in Tomsk, the wind at the time was from the south-west, and the plume of radioactive debris drifted over sparsely populated forest.
Once the fire was out, the official prevarication began. Initial statements claimed that radioactive contamination was confined to the plant grounds, and that the total area affected was no more than 1000 square metres. Later, it was admitted that radiation levels had been raised over many square kilometres. Conflicting statements also appeared on whether plutonium had been among the materials which escaped.
Monitoring over the days following the explosion showed that radiation levels were higher than normal in a strip extending for more than 22 km from the plant. The highest level recorded was 400 microroentgens per hour, compared with normal background radiation in the area of . The only permanent settlements affected were two small villages in which readings were around 35 microroentgens per hour.
Radiation levels such as those found in the villages would not normally be considered alarming; depending on geological factors, natural background radiation may be considerably higher than this. The presence of plutonium, however, changes the situation drastically. Even tiny particles of plutonium dust, if they lodge in the lungs, create a high risk of cancer. Unlike many of the radioactive products of nuclear reactions, plutonium does not decay into harmlessness within a few weeks or months; its half-life is 24,000 years.
"Plutonium was released into the atmosphere, but we have no information as to how much of it escaped", Ecology Ministry spokesperson Alexander Shuvalov said on April 9. "Plutonium must seep into the soil from the snow", observed Lidiya Popova, a nuclear scientist and activist in the Social-Ecological Union, Russia's largest environmental organisation. "The area will remain unsafe for at least 240,000 years."
Officials in Tomsk Province must now act quickly if they are to stop melting snow from carrying radioactive contaminants into the River Tom. Plans are being drawn up for a system of dams and canals to take water to evaporation ponds.
The accident once again focuses attention on the danger posed to large parts of the northern hemisphere by Russia's increasingly dilapidated and ill-staffed nuclear industry. Following a release of radiation from a Chernobyl-type nuclear power reactor near St Petersburg in March 1992, leaders of the Group of Seven industrialised nations agreed to spend US$700 million to upgrade the most dangerous nuclear power plants in the former USSR. However, disagreements between the donors on how the funds should be disbursed have prevented more than a small proportion of the money from being handed over.
The London Times reported recently that more than 200 "incidents" were recorded during 1992 in Russian plants and institutions handling radioactive materials.
In the major centres of the nuclear industry, the potential for accidents involving nuclear waste is unnerving. According to the newspaper Trud, about 130,000 tons of solid and 33 million cubic metres of liquid radioactive wastes have accumulated at Tomsk-7 in underground stores. In 1990, 38 workers in the city were hospitalised after being exposed to radiation.
So far, the most serious accident involving plutonium in Russia has been an explosion that took place in 1957 at the Chelyabinsk-65 nuclear weapons complex in the Urals. A total of 217 towns and villages were contaminated, and nearly 11,000 people were later resettled.
Environmentalists are concerned that next time a plutonium spill occurs, the area made uninhabitable may not be in a remote forest region, but in the Russian capital itself. According to Lidiya Popova, n laboratories working with dangerous nuclear fuels like plutonium are located in Moscow.