Leidos Holdings Inc. (NYSE: LDOS) and Parsons Corp. (NYSE: PSN) earned spots on a $4 billion contract as part of a joint venture to support the cleanup of a former nuclear weapons site in southern Washington state. The Department of Energy announced the award Thursday of the Hanford Mission Essential Services Contract (HMESC), tapping the incumbent contractor Leidos, alongside Centerra Group LLC and Parsons as members of the Hanford Mission Integration Solutions (HMIS) LLC. The 586-acre Hanford…