Chernobyl nuclear disaster site given new 'shield'

A new shelter is being built to protect the site of the world's worst nuclear accident, at Chernobyl in Ukraine.

The construction costs over £1bn ($1.46bn/1.38bn euros) and is intended to stop radioactive material leaking, and to allow the old reactor to be dismantled safely.

A catastrophic explosion in April 1986 caused 31 deaths, and the radioactive material released spread across Europe.

The BBC's Science Editor David Shukman went to see the shield being built.