The Department of Energy uses a formal process of security clearances to help prevent unauthorized access to sites and facilities that niaintain or store classified information and/or special nuclear material. As part of this process, security badges are issued to indicate whethcr the individual possesses a security clearance and, as a consequence, whctlier access to agency facilities is permitted. In addition, the Department maintains a Central Personnel Clearance Index to track security clearance information. In virtually all circumstances, policy requires that security clearances be terminated when an individual ends their association with the Department. A limited exception to that policy exists for contractor employees that arc to be reemployed within three months. Closely controlling security clearances and restricting access to facilities to authorized individuals arc essential to protecting the Department's valuable security and property assets.