(Hanford, WA)  --  Operators at the Hanford nuclear reservation in Washington are working to fix a huge hole in the roof of a tunnel that contains rail cars full of radioactive equipment.  Thousands of Hanford workers filed out of the facility yesterday after the hole was discovered next to a closed area known as the PUREX plant, but there were no reports of radiation being released.  Hanford site officials tell the "Spokesman-Review" it's not clear how the hole, estimated at 400 square feet, will be covered.  Spokesman Destry Henderson says officials are exploring the possibility of placing a barrier between the contaminated equipment inside and the outside air without causing the hole to grow larger.