A method of decommissioning, in which radioactive contaminants are encased in a structurally long-lived material, such as concrete. The entombed structure is maintained and surveillance is continued until the entombed radioactive waste decays to a level permitting termination of the licence and unrestricted release of the property. During the entombment period, the licensee maintains the licence previously issued by the NRC. For further information, see the Fact Sheet on Decommissioning Nuclear Power Plants.