French energy giant EDF has shut down reactor number one at its controversial nuclear power plant in Fessenheim on the German border, the company said late Tuesday. The shutdown was due to "a malfunction discovered during a periodical test carried out on a piece of security equipment situated in a non-nuclear part of the facility," EDF said in a statement. Teams were working on fixing the equipment, and there would be no impact on safety or the environment, the statement added. EDF expected that the shutdown would not be for long. The statement also warned that clouds of steam might form above the power station, but that they would not be radioactive. French Energy Minister Segolene Royal announced within the last two weeks that the Fessenheim nuclear power plant would be permanently shut down at the end of 2018. Environmental campaigners and France's neighbours in Germany have long complained that the outdated facility presents the risk of a nuclear accident. German Greens have dubbed the plant as "scrap." One of its reactors was disconnected from the grid last year when a material defect was discovered in a steam generator.