Former US government officials and independent experts urged the US government to reconsider the Molten Chloride Reactor Experiment (MCRE), which will use 600 kg of weapon-grade HEU (93% uranium-235). The experts argue that the experiment "would undermine the longstanding U.S. policy of HEU minimization, and thereby increase risks of nuclear proliferation and nuclear terrorism." In a letter addressed to the Secretary of Energy and the Administrator of the NNSA, the experts urge the Department of Energy "to suspend further work on the MCRE until your department's Nuclear Energy office develops an alternative LEU design."