The U.S. Government Accountability Office has rejected a protest, from a team led by Parsons Corp., of a $3.3-billion, six-year nuclear-waste cleanup contract for the U.S. Energy Dept.’s Savannah River Site in Aiken, S.C., awarded in December to a team led by the Washington division of URS Corp. GAO declined to explain the rationale for its decision until its opinion is redacted. Parsons would not give a reason for the protest.