WASHINGTON, June 6 — Closing the Indian Point nuclear reactors would make electricity more expensive, leave New York more vulnerable to natural gas shortages and add to pollution that causes global warming, according to a report released on Tuesday by a committee of the National Academy of Sciences. The committee said that there were no insurmountable technical obstacles to closing the plant. But it asserted that electric demand was growing so fast in the region, and building power plants was so difficult, that simply meeting power needs during peak periods would be a challenge even if the reactors stayed in...