A tank that holds radioactive liquid at the Hanford Nuclear Reservation, the nation’s most contaminated nuclear site, is leaking, Gov. Jay Inslee said Friday. The news raises concerns about the site’s other storage tanks, which hold millions of gallons of a highly radioactive stew left from decades of plutonium production for nuclear weapons. The federal Department of Energy said that liquid levels were falling in one of 177 underground tanks, but that monitoring wells near the tank had not detected higher radiation levels. Mr. Inslee said the leak could be in between 150 and 300 gallons a year. A plant being built to treat the waste is billions of dollars over budget and years behind schedule.