CHERNOBYL, Ukraine (AP) -- A small bulldozer-like machine is prowling among pieces of brick and metal in front of a huge concrete structure covering the destroyed reactor at the Chernobyl nuclear power plant.
The machine, a mobile inspection robot, was developed in the United States especially to explore the debris inside Chernobyl's reactor No. 4, which exploded and caught fire in 1986 in the world's worst nuclear disaster.On Thursday, designers of the robot -- called Pioneer -- presented it at Chernobyl, marking the start of tests to prepare the machine for entering the highly contaminated environment under the troubled reactor's shelter.
The concrete-and-steel sarcophagus was hastily built over the ruined reactor soon after the 1986 accident to prevent further radioactive pollution by the remains of fuel that had been left over after the explosion.
Chernobyl officials have warned that the structure's supports could collapse unless urgent repairs were made, and said there was a possibility of a chain reaction and a danger of fire in the sarcophagus, which contains several thousand tons of flammable materials.
However, through the years that have passed since the explosion, experts have faced serious difficulties determining what exactly was going on in the so-called shelter.