BERLIN—Germany on Friday shut down half of the six nuclear plants it still has in operation. The decision to phase out nuclear power and shift from fossil fuels to renewable energy was first taken by the government of Gerhard Schroeder in 2002. His successor, Angela Merkel, reversed her decision to extend the lifetime of Germany’s nuclear plants in the wake of the 2011 Fukushima disaster in Japan and set 2022 as the final deadline for shutting them down. The three reactors now being shuttered were first powered up in the mid-1980s. Together they provided electricity to millions of German households for almost four decades. One of the plants—Brokdorf, located 40 kilometers (25 miles) northwest of Hamburg on the Elbe River—became a particular focus of anti-nuclear protests that were fueled by the 1986 Chernobyl catastrophe in the Soviet Union. The other two plants are Grohnde, 40 kilometers south of Hannover, and …