each weigh ; 6,156 vertical fuel channels contain 49,248 natural uranium magnox-clad fuel elements, hence the name magnox reactor. A further 200 channels allow boron control rods to enter the reactor and control the nuclear reaction. The primary coolant in the reactors is carbon dioxide gas. The site is managed by Magnox Ltd, formerly Magnox North, formerly British Nuclear Group, formerly Magnox Electric, formerly Nuclear Electric, formerly National Power, formerly the Central Electricity Generating Board (CEGB); which is a subsidiary of the site owner, the Nuclear Decommissioning Authority (NDA). The NDA's purpose is to oversee the decommissioning and clean-up of the UK's civil nuclear legacy. During its operational life substantial works were needed to strengthen the reactors against deteriorating welds discovered in the safety review in April 2000. Amid public controversy, Greenpeace issued an independent safety appraisal, commissioned a report from Large Associates, critical of the plant and its restart plans, but the permit to restart operation was given in August 2001. In addition to welding weaknesses, radiolytic depletion of the graphite moderator blocks was still of concern and PAWB continue to campaign for early shut-down of the plant as well as against any nuclear replacement. Closure and decommissioning On 20 July 2006, the NDA announced that the station would be shut down in 2010 to enable the closure and decommissioning of the Magnox spent fuel reprocessing plant at Sellafield. Springfields Fuels Limited ended production of Magnox fuel elements in 2008 due to these plans. In 2010, the NDA announced an extension to 2012, beyond Wylfa's 40th anniversary as a generating power station in January 2011, due to schedule slippage at Sellafield which would allow Wylfa additional time before final defuelling. At this time, a strategy was also devised to maximise the generation from the remaining fuel stock given that new fuel could no longer be manufactured. This required a change in the distribution of fuel within the reactors, as well as the closure of Reactor 2 in 2012 to allow this fuel to be transferred into Reactor 1. Reactor 2 ceased generating on 25 April 2012 at 19:02 BST, allowing Reactor 1 to continue to operate. A license extension to operate Reactor 1 until 31 December 2015 was granted in September 2014. Reactor 1 was shut down on 30 December 2015. Defueling started in 2016, and was completed in 2019. Defueling and removal of most buildings is expected to