MOSCOW — An explosion at a secret Siberian nuclear weapons complex contaminated an area more than three times greater than previously thought, the latest official estimate said Monday.
At the Chernobyl nuclear power plant in Ukraine, meanwhile, the No. 1 reactor was shut down Monday because of a malfunctioning turbine engine, the Itar-Tass news agency said. Head engineer Viktor Vasilchenko said there was no danger of radiation leaks.
The 1986 explosion and fire at the Chernobyl reactor was the worst nuclear accident to date. At least 32 people died and a large area of Ukraine, Belarus and Russia was contaminated.
Russian experts said the explosion last Tuesday at the Siberian chemical complex near the city of Tomsk-7 was the worst nuclear accident in the former Soviet Union since Chernobyl.
There were no deaths, but assessments of the contaminated area have grown daily, and official accounts have varied widely.
The environmental group Greenpeace has accused Russia's nuclear leadership of covering up the severity of the accident and has demanded an investigation.
The Atomic Energy Ministry said Monday that the explosion at the complex, about 1,700 miles east of Moscow, contaminated about 46 square miles, the Interfax and Itar-Tass news agencies reported.
It did not explain the discrepancy between that estimate and its own estimate Sunday, when it said the radioactive zone was 10 miles long and covered 14 square miles.
Sergei Shoigu, chairman of the State Emergency Committee, said one village, Georgiyevka, is in the contaminated area. It has about 30 families. They have not been evacuated.
Shoigu said the most dangerous area is a half-mile section of the Tomsk-Samus highway, Itar-Tass said. Snow has been removed from the area, and decontamination has begun, he said.
Environmental experts from the State Emergency Committee concluded Monday that the traces of plutonium in the affected area were insignificant and posed no health danger, according to Itar-Tass and Interfax.
The vat that exploded contained liquid radioactive waste consisting of uranium salts and plutonium, which is fatal if inhaled even in microscopic amounts.