In January 2016, 20 kilograms of plutonium were taken from PSI to the USA. According to a newspaper report, the federal government had a secret plutonium storage facility in which the material had been kept since the 1960s to construct an atomic bomb as planned at the time. The Federal Council denied this, maintaining the plutonium-239 content of the material was below 92 percent, which meant it was not weapons-grade material. The idea was rather to use the material obtained from reprocessed fuel rods of the Diorit research reactor, which was operated from 1960 to 1977, to develop a new generation of fuel element types for nuclear power plants. This, however, never happened. By the time it was decided, in 2011, to phase out nuclear power, it had become clear that there was no further use for the material in Switzerland. The Federal Council decided at the Nuclear Security Summit in 2014 to close the Swiss plutonium storage facility. A bilateral agreement between the two countries meant the plutonium could then be transferred to the USA for further storage.