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Clearances
DOE and other federal employees and contractor employees hold about 220,000 clearances. DOE employees hold about 4 percent of the total; contractor employees, about 93 percent; and other government agencies and congressional staff, the remaining 3 percent. DOE issues five levels of clearances:<5>
Q Sensitive allow access to Special Nuclear Material (SNM) category 1. An employee with a Q sensitive clearance could have access to nuclear weapons design, manufacture, or use data; disclosure could cause exceptionally grave damage to the nation.
Q Nonsensitive allow access to Special Nuclear Material (SNM) category 2. The higher the SNM category, the more readily the material could be converted to a nuclear explosive device. Categories 1 and 2 require special protection, such as armed guards.
L clearances allow access to Secret National Security Information and to Special Nuclear Material (SNM) categories 3 and 4, but not to Secret Restricted Data or SNM categories 1 and 2. Persons with L clearance may have access only to Confidential RD but may have access to both Confidential and Secret FRD and NSI. For an L clearance, the background investigation of a person is much less extensive hence much cheaper and quicker than for a Q. The two clearances do, however, require the same standards of personal conduct. Anything turned up by an investigation that would cause a Q to be denied would also cause denial of an L.
Top Secret An employee with a secret clearance could have access to weapons-related National Security Information; disclosure of this information could cause exceptionally grave damage to the nation.
Secret An employee with a secret clearance could have access to weapons-related National Security Information; disclosure of this information could result in serious damage to the nation.
https://fas.org/sgp/classdoe.htm