Minneapolis-based Xcel Energy Inc. on Monday brought one of its 550 MW units (Unit 1) at Prairie Island Nuclear Generating Plant in Minnesota back to full power following a repair outage that began Dec. 10, requiring additional purchased natural gas-fired generation during the outage. The situation posed no danger to the public or plant workers, and Unit 2 continued to operate at full power during the repairs, Xcel said. Xcel has not yet calculated the total costs of replacement power; however, the impact on customer bills is expected to be relatively small.Prairie Island and Xcel’s second nuclear plant, Monticello, are among the multi-state utility’s lower-cost sources of generation, according to Xcel.