The decision follows an assessment, including checks on all aspects of the environmental safety case put forward by WRL, consultation with the local community and approval by the European Commission.
The Environment Agency said that it was satisfied that very low levels of radioactive waste would not cause a risk to people or the environment if disposed of at the Cumbrian landfill site.
The waste — the lowest category that requires permitting for disposal — is likely to come from a number of nuclear sites, such as Sellafield. It will include building rubble and soil, and other demolition waste from decommissioning activities, plus other items such as used clothing or gloves.
The Lillyhall landfill site already holds the relevant planning permission and an environmental permit to dispose of other non-radioactive wastes.
Ian Parker, nuclear regulation manager at the Environment Agency, said that the agency would ensure that WRL carries out regular checks and monitoring to confirm that the strict terms of its permit are being adhered to.