Anadarko Petroleum Corp's agreement to pay $5.15 billion to clean up nuclear fuel and other pollution received approval from a federal judge on Monday, the final hurdle for the settlement touted by the U.S. Department of Justice as the largest-ever environmental cleanup recovery. The agreement, reached in April, resolved a lawsuit against Anadarko and its Kerr-McGee unit from creditors of Tronox Inc, the paint materials maker that was once a unit of Kerr-McGee.