Steel lid to seal Chernobyl reactor

Chernobyl nuclear power station
The Ukrainian authorities have approved a giant steel cover for the Chernobyl reactor, the site of the world's worst nuclear accident 21 years ago.

French and U.S. companies are to build the structure, which will replace the crumbling concrete casing that currently protects the Chenobyl 4 reactor. 

The contractors will also build a special facility to store spent nuclear fuel.

It will take five years to complete.  Authorities say they'll start dismantling the reactor once the work is done.