Work to build a permanent shelter to secure the exploded reactor at the Chernobyl nuclear power plant in Ukraine has reached a key milestone when workers raised the arched section that will cover the destroyed unit. The explosion at reactor number four at the Chernobyl power plant on April 26, 1986 sent radioactive fallout into the atmosphere that spread from the Soviet Union across Europe. It remains the world’s worst nuclear accident. The structure that was raised to its full height on Tuesday will be part of the so-called New Safe Confinement, a colossal arch-shaped structure which when completed will be slid on rails over the existing sarcophagus covering the reactor. During the initial lifting operation, around 5,000 tonnes of steel was raised to a preliminary height of up to 22 metres, according to the European Bank for Reconstruction and Development (EBRD). The EBRD is administering the fund to build the shelter with the help of donor contributions. “This is a very significant milestone, which is a tribute to the ongoing commitment of the international donor community, and an important step towards overcoming the legacy of the accident,” EBRD President Suma Chakrabarti said. When it is finished in 2015, the structure will weigh 20,000 tonnes and span 257 metres.