Sellafield with extension options to 17 years. On 13 January 2015, the NDA announced that NMP would lose the management contract for Sellafield Ltd. as the "complexity and technical uncertainties presented significantly greater challenges than other NDA sites", and the site was therefore "less well suited" to the NDA's existing standard management model. The new structure, which came into effect on 1 April 2016, saw Sellafield Ltd. become a subsidiary of the NDA. Activities at the Sellafield site primarily support decommissioning of historic plants, and reprocessing fuel from UK and international nuclear reactors. Decommissioning projects include the Windscale Piles, Calder Hall,
Oldbury Nuclear Power Station an urban area twice the size of Bristol. Reactor 1 went critical on 18 September 1967 and first generated electricity on 9 November 1967, Reactor 2 started generating electricity in April 1968. The construction was undertaken by a consortium known as The Nuclear Power Group ('TNPG'). The reactors were supplied by TNPG and the turbines by AEI and C. A. Parsons & Co. The main civil engineering contractor was Sir Robert McAlpine. Construction on site began in 1961. Oldbury was the first nuclear power station in the UK to use prestressed concrete pressure vessels, earlier Magnox reactors having used steel