Managers of a government uranium plant in Paducah, Ky., knew for decades that workers were being exposed to radiation hazards but concealed the information because of fears of a public outcry, according to documents to be released by a congressional panel this week. Memos and other documents showing what plant management knew and concealed have been turned over to a House Commerce Committee panel, which is holding hearings tomorrow into allegations of unsafe conditions at the facility. Accounts of plutonium contamination and illegal waste dumping at the plant have triggered an Energy Department investigation and a class action lawsuit by plant workers. On Friday, Energy Secretary Bill Richardson toured the facility, apologized to workers, and pledged millions of dollars to compensate sick workers and clean up the plant.