A federal judge yesterday temporarily blocked the Energy Department from trucking plutonium fuel across Michigan to Canadian nuclear reactors, ruling that the DOE needs to conduct a more comprehensive environmental impact statement before transporting the fuel on public roads from Los Alamos, N.M., 1,700 miles away. The feds are aiming to process the nuclear fuel from scrapped Cold War U.S. and Russian warheads, but opponents of the plan say the shipments north would be vulnerable to fire and terrorism; they have sued the DOE and oral arguments in the case are scheduled for Dec. 14.