"The reason such information is needed is nowhere more obvious than at Chernobyl itself, where another nuclear accident could occur. Danger is increasing in what's left of Reactor 4 -- commonly called "the sarcophagus." The concrete tomb encasing the reactor hasn't held up. And some believe it's a threat to the world. Forty tons of radioactive dust have accumulated inside. And there's a pressed slab of uranium and concrete that some believe could lead to a chain reaction, causing a more powerful explosion than the original one. It's a terrifying possibility. The original explosion spewed radiation throughout Europe, and spread to parts of the rest of the world. Human error, compounded by a faulty technical design, led to the accident. Exposure to massive amounts of radiation immediately killed 32 plant workers and firefighters. Thou-sands more died later from effects of the accident. The Ukrainian government now says hundreds of thousands of people suffer from Chernobyl-related illnesses."