Britain closed its oldest nuclear reactor after nearly 45 years of service on Wednesday, marking the end of a British technology that dominated the country's nuclear industry for decades.

Closure of the Wylfa 1 reactor in Anglesey, Wales, leaves Britain with 15 nuclear reactors, all of them operated by France's EDF.

"Wylfa Nuclear Power Station (has) closed down, marking the conclusion of Magnox reactor generation in the UK," operator Magnox Ltd said in a statement. The site will now undergo defueling as part of its permanent closure.

Work began on the twin Wylfa 1 and Wylfa 2 reactors in 1963 and operations began in 1971. Wylfa 2 was permanently shut down in April 2012.

The 490-megawatt units were the last and largest of the 26 Magnox reactors built across Britain beginning in the 1950s. The company also exported reactors to Italy and Japan in the 1960s.

Horizon Nuclear Power, a subsidiary of Japan's Hitachi Ltd., plans to build two new reactors at an adjacent site with operations expected to begin in the early 2020s.