The Beznau nuclear power plant in Switzerland, which was shut down multiple times over the last two months due to summer heatwaves, is fully operational again, Swiss energy company Axpo said on Friday.Axpo said the second reactor at the Beznau plant in northern Switzerland, Europe’s oldest nuclear power plant still in operation, went back online on Thursday.The heatwaves that hit Europe sent temperatures soaring in the Aare River, which the site uses for cooling.Reactor 1 has been back in operation since 21 August and Axpo said it had now reconnected the other to the grid, which is “now gradually returning to power operation and is expected to reach full capacity within approximately two days.”Reactor 2 was taken offline on 4 August for refuelling, during which 20 of the 121 fuel assemblies in the reactor core were replaced.The plant had been shut down in June and again in July due to the unusually high temperatures in the Aare, which drains nearly half of Switzerland and flows into the Rhine.Several European nuclear power plants had to reduce their output or temporarily shut due to summer heatwaves.Nuclear energy accounts for just over a third of Switzerland’s electricity production.The country has four ageing nuclear reactors, including the two at Beznau, which produce around a tenth of Switzerland’s electricity demand.Reactor 1 was first brought online in 1969 and Reactor 2 in 1971, making it one of the oldest nuclear plants in the world.