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,
Wylfa Nuclear Power Station nuclear station on a site adjacent to the old plant. An application to build two advanced boiling water reactors was submitted by Horizon Nuclear Power to the Office of Nuclear Regulation on 4 April 2017. Wylfa was the second nuclear power station to be built in Wales after Trawsfynydd in 1959. Following the closure of Trawsfynydd in 1991, Wylfa became Wales' only nuclear power station. Construction of Wylfa, which was undertaken by British Nuclear Design & Construction (BNDC), a consortium backed by English Electric, Babcock & Wilcox Ltd and Taylor Woodrow Construction, began in 1963. The reactors were supplied by