The government's nuclear safety regulator has revealed that during the second half of 2013 three incidents took place at the site operated by Rolls-Royce Marine Power Operations Ltd (RRMPOL) in Derby where reactors for the UK's nuclear powered submarines are produced.
In the first incident swarf in a non-active machining area of the factory's clean shop caught fire leading to an evacuation of the building, according to a report published by the Office for Nuclear Regulation (ONR). The fire was rapidly extinguished and machinery involved in the fire was made safe. During the second incident the 'Neptune' test reactor, which is used to design and evaluate equipment for reactor systems, made an unplanned shoutdown when a safety system was tripped. According to ONR no operating rules or limits were breached during the incident.
In the third incident a small volume of radioactive liquor was accidentally released into an engineered secondary containment area. No-one was contaminated as a result of the incident and there was no release of radioactivity to the environment. RRMPOL have investigated each incident and ONR are monitoring follow-up actions taken by the company.
ONR recently concluded that the manufacturing site at Derby can continue to operate following a ten-year periodic review of safety which was conducted by Rolls-Royce in 2012. ONR's assessment of the review had been delayed to allow the regulator prioritise work on approving new build construction work at the site and has only now been published. The review did not identify any safety factors which would compromise safe operation of the site, but a programme of work is underway to implement a number of improvements to plant, equipment, facilities, and processes as a result of the review.
A new manufacturing facility is currently under construction at Derby as part of the Ministry of Defence's Core Production Capability regeneration project, which will eventually replace the current plant for manufacturing reactor components and fuel. The first phase of the project – construction of a new 'Manufacturing Facility First Build' building – is underway and ONR has allowed construction plans to be amended to allow construction to take place independently of construction of a second new building known as the Product Assembly Building.
The two buildings were to have shared common foundation piling, but design of the Product Assembly Building has not yet been finalised and, in order to avoid construction delays, ONR has agreed that the two buildings should have separate foundations. The regulator has concluded that this will not present any immediate nuclear safety risks, but that it might present a construction risk to the project which Rolls-Royce will have to bear.