The Atomic Weapons Establishment (AWE) at Aldermaston could face enforcement action after failing meet a deadline to deal with 1,000 drums of nuclear waste.
The Office for Nuclear Regulation (ONR) said a 2007 licence requiring AWE to reduce and encapsulate “intermediate level waste” by February had expired.
AWE said it informed ONR in 2011 it was unable to meet the deadline after work on the project was abandoned. ONR said the issue did not “give rise to significant risk to the public”.
AWE said the project to reduce the volume of the waste and encapsulate it at the Berkshire site was halted after the company concluded it was not the best long-term solution.
A spokesman for the regulator said: “ONR inspectors… are content that the current conditions under which the intermediate level waste is stored are acceptable in the short term and do not give rise to significant risk to the public or the workforce.
“Since August 2011 ONR has pressed AWE to… demonstrate adequate progress in placing the hazardous material into a passively safe form”.
“AWE has, in response, improved its arrangements for storing untreated intermediate level waste, and has made progress in developing its long term waste treatment and storage strategy.” ONR, an agency of the Health and Safety Executive, said it was investigating AWE's licence breach but did not give details of potential enforcement action.
AWE said it had remained in dialogue with the ONR and worked closely with the Nuclear Decommissioning Authority to find an appropriate long term solution. AWE Aldermaston is one of five UK locations shortlisted by the MoD to store nuclear waste from submarines.
In 2013, the facility was criticised for leaking radioactive gas into a stream, although the Environment Agency said the low levels of radiation did not represent an environmental hazard. It was also fined £200,000 for a safety breach during a fire at the site in 2010.