They want to complete a survey of the installation before an international effort begins to repair the massive concrete and steel tomb that now surrounds it.

The sarcophagus is in danger of following down

This sarcophagus, as it is known, was erected quickly in the aftermath of what was the world's worst nuclear accident. But, weakened by radiation and the elements, it is now in danger of collapse.

Were this to happen, radioactive dust and debris would be thrown into the atmosphere resulting in another environmental disaster.

Enter Pioneer, a sturdy robot featured on this week's edition of the BBC science programme Tomorrow's World. The machine will be sent to the most dangerous parts of the Chernobyl plant - places where human operators would get a lifetime's radiation in just three minutes.

3D map

It has a plough on the front to push aside fallen debris and tank tracks to climb over larger objects. An imposing drill allows Pioneer to test the structural weakness of concrete.

Pioneer will go into the most dangerous areas

Crucially, by using spaceage camera technology, the robot will also be able to construct a three dimensional map of the damaged power station's interior.

"The 3D mapper takes the three images and generates a 3D model of the shelter," says Mike Catalan from robotics company RedZone. "It's basically an extension of the 3D image system that was used on the Mars Sojourner robot."

These unique images, together with temperature and radiation data, will help build a comprehensive picture of what the reactor is now like inside the sarcophagus.

The international community can then make proper decisions about what needs to be done to make Chernobyl safe.

Biobot heroes

This should finally end the need for humans to go into the tomb to carry out emergency repairs. These people, known as biobots, expose themselves to dangerously high levels of radiation.

The robot will help construct 3D images

"There have been a lot of manned entries into the shelter," says Bruce Thompson from RedZone. "As times move on, they've moved beyond that phase. I've heard the Ukrainians say 'now is not the time for heroics'. It's time to use more remote technology."

But Pioneer's most sensitive systems will also need to be protected from the intense radiation. None of the important electronics are on board - they are kept safely inside a lead-lined room with Pioneer connected to the controls by an unbiblical cord.

The Chernobyl accident in April 1986 was the result of a test procedure that went disastrously wrong. More than 30 people died fighting the initial fire and 46,000 people had to be evacuated from the region within a radius of 10 km around Pripyat.