The environmental effects of the explosion at the Chernobyl nuclear power plant in Ukraine began to dissipate long ago. But the political effects are still causing diplomats and development bankers to lose hair in large clumps. The sarcophagus built to surrond the burn-out reactor has begun to crumble, and western governments are helping to finance its repair. But another reactor of Chernobyl is still being used sporadically to generate electricity. Fearing a second disaster, those governments want the whole plant shut for good.