He tells RFE/RL that the BN-350 type of reactor was long ago abandoned in the United States: "Breeder reactors were abandoned under President Jimmy Carter in the late 1970s because he recognized that reactors that produce as part of their operation more plutonium than they start with contribute directly to proliferation. They make more plutonium available throughout the world. It's much easier to make a nuclear weapon out of plutonium than it is out of uranium."