Thirty U.S. nuclear power plants still need to upgrade their computers to be immune from the Y2K computer bug, and six of the plants are not scheduled to finish their repairs until just weeks before year end, the Nuclear Regulatory Commission said yesterday. The NRC said that none of the systems still in need of repair involve safety, but leaders of a special Senate committee on the millennium bug are concerned, saying there might not be enough time to correct unforeseen problems. Meanwhile, a diplomat at the French embassy in the Ukraine has advised all French citizens living in the area to leave before the beginning of the new year, warning of potential risk in the region where the Chernobyl nuclear disaster took place. But the French government has dismissed the diplomat’s warning.