Wylfa is situated west of Cemaes Bay on the island of Anglesey, off the northwestern coast of Wales.

Wylfa was also the second British nuclear power station, following Oldbury, to have a pre-stressed concrete pressure vessel instead of steel for easier construction and enhanced safety.

Although the original design output was 1,190 MW, unexpected accelerated ("breakaway") corrosion of mild steel components of the gas circuit in hot CO2 was detected even before the first reactor began operating.

During its operational life substantial works were needed to strengthen the reactors against deteriorating welds discovered in the safety review in April 2000.

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.

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.

Horizon planned to build two advanced boiling water reactors (ABWRs) at a site to the south of the existing Wylfa station.

[18][19] On 18 October 2010, the British government announced that Wylfa was one of the eight sites it considered suitable for future nuclear power stations.

[20] In January 2012, 300 anti-nuclear protesters took to the streets of Llangefni, against plans to build a new nuclear power station at Wylfa.

[28] Horizon Nuclear Power submitted a Development Consent Order application for the Wylfa Newydd project to the Planning Inspectorate on 1 June 2018.

Duncan Hawthorne, chief executive of Horizon Nuclear Power, said: "...we will take steps to reduce our presence but keep the option to resume development in future".

[32] The UK government had been expected to grant a development consent order in a move to restart the project,[33] but subsequently deferred the decision deadline until 30 September 2020.

It will close down its development activities, but will work with the UK government and other stakeholders to facilitate future options for the two sites.

[37] In January 2021, Shearwater Energy presented plans for a hybrid plant, to consist of a wind farm and small modular reactors (SMRs), to be installed adjacent to the existing Wylfa power station but separate from the proposed Wylfa Newydd site.

[39][40][clarification needed] In March 2024, during the Spring Budget, Chancellor Jeremy Hunt announced that the site would be purchased from Hitachi for £160m.