A federal judge has blocked Vermont from forcing the closure of the Vermont Yankee nuclear power plant when its license expires in March. The Vermont Senate voted to deny the company a new operating license in 2010, but the federal Nuclear Regulatory Commission extended the plant’s license in the days following last year’s Fukushima nuclear crisis. On Thursday, U.S. District Judge J. Garvan Murtha overruled Vermont’s effort, saying only federal authorities can regulate nuclear safety. The Vermont Yankee plant is one of the oldest in the country and has had a series of radioactive tritium leaks. Vermont officials are expected to appeal the ruling.