A new structure built to confine the Chernobyl reactor at the centre of the world's worst nuclear disaster was previewed for the media on Tuesday. Reactor number four at the Chernobyl nuclear power plant in Ukraine exploded and burned on April 26, 1986. The complex construction effort to secure the molten reactor's core and 200 tonnes of highly radioactive material has taken nine years to complete under the auspices of the European Bank for Reconstruction and Development. The structure itself cost €1.5 billion (Dh3.6bn) and the entire shelter project cost €2.2bn. The European Bank for Reconstruction and Development managed a fund with contributions from 45 countries, the EU and €715 million in the bank's own resources. The shelter is the largest moveable land-based structure ever built, with a span of 257 metres and a total weight of more than 36,000 tonnes. "This was a very long project," said Balthasar Lindauer, director of the bank's Nuclear Safety Department. He noted that preliminary studies began in 1998 and the contract for the structure was placed in 2007. He said Ukraine was a big contributor, offering €100 million in cash along with expertise and personnel.