Three workers at HM Naval Base Devonport have received an accidental intake of radioactive material following an incident during a submarine maintenance operation.
The incident – described as “minor” by the Office for Nuclear Regulation (ONR) – took place in the New Equipment Maintenance Storage facility at the Devonport naval dockyard when a large radioactive component from the submarine was being manoeuvred within an enclosure in the building.
An accidental tear in heavy sheet plastic enclosing the component allowed the release of a small amount of radioactive particulate matter, some of which was inhaled by the three workers.
All three were given chest monitoring for radiation and the effective radiation doses which they were assessed as receiving ranged between less than 10 and 50 microSieverts. The doses were significantly below the maximum daily dose permitted at the Devonport dockyard of 500 microSieverts and the statutory annual dose limit of 20 milliSieverts.
Both Devonport Royal Dockyard Ltd (DRDL), which operates the site, and ONR have carried out internal investigations into the incident and have identified a number of improvement actions concerning risk assessment and the handling of components such as the one involved in the incident.
ONR is “generally satisfied” that DRDL’s investigation and recommendations are appropriate and has decided not to take formal enforcement action against DRDL, but has written to the company to ensure that recommendations are actioned promptly.
The accident, which is believed to have taken place during the summer of 2013, has only recently come to light following publication of an Office for Nuclear Regulation quarterly site report for the Devonport dockyard, which mentions the incident.