Christian Science Monitor: More than two decades after the Chernobyl meltdown, the world again is staring uneasily at the Janus faces of nuclear power. One offers an energy source that won’t cause global warming. The other presents challenges in cost, safety, disposal, and nuclear proliferation. Rising energy prices, and especially the need to find alternatives to fossil fuels that pour out greenhouse gases, have put a fresh focus on nuclear power. “We are facing a nuclear renaissance,” the head of a …