A new shelter is being built to protect Chernobyl in Ukraine. The construction costs over £1bn (.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.
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