Article Photos: Nuclear board warns of Hanford tank explosion risk 1/1

FILE -- In this March 23, 2004 file photo, workers at the tank farms on the Hanford Nuclear Reservation near Richland, Wash., measure for radiation and the presence of toxic vapors. A nuclear safety board has warned a key U.S. senator that underground tanks holding radioactive waste at the nation's most contaminated nuclear site pose a possible risk of explosion. Concerns that hydrogen gas could build up inside the tanks and lead to an explosion at south-central Washington state's Hanford Nuclear Reservation have been known for some time.(AP Photo/Jackie Johnston, File)