A defunct nuclear reactor from the Trojan Nuclear Plant in Oregon safely completed a 36-hour, 270-mile barge ride up the Columbia River yesterday, reaching its destination at the Port of Benton, Wash. A tugboat pushed the barge past Portland, Ore., at about 1 a.m. Saturday, making it the first commercial reactor of that size and level of contamination to travel so near to a major U.S. city. Three years of design and planning went into building a special barge for the 1,000-ton reactor and a 320-wheel, 20-axle trailer that transported the reactor from the banks of the river 20 miles to its burial site at the Hanford Nuclear Reservation.