The first footage for over 50 years has been captured on camera from inside the experimental Dounreay Fast Reactor (DFR) in Scotland.

DFR operated between from 1959 to 1977, using a sodium-potassium liquid metal to transfer heat from the core and breeder area via 24 heat exchanger loops. Since its closure, all but one of the fuel assemblies and 977 breeder elements have been removed from the reactor, along with the primary and secondary coolant. Decommissioning plans envisage demolition of the reactor building by 2025.

In 2012, following the removal and destruction of 57 tonnes of primary NaK, nitrogen-cooled digital cameras were inserted into the reactor for the first time in 50 years, to record images of the internal structures and the breeder fuel matrix.

The inspections (which ran from December 2012) were undertaken through penetrations in the top of the vessel, giving visual evidence of the condition of swollen and stuck breeder elements.

The cameras, which are predominantly used in the oil industry, had to be manufactured and modified to take into account the nuclear environment and the 100C temperature in the reactor vessel, according to the Babcock Dounreay Partnership, which operates the Dounreay site on behalf of the Nuclear Decommissioning Authority (NDA). Precise control of the atmosphere was required during the inspections due to the residual NaK and radioactive contamination present.

"The images and information captured are now enabling the Dounreay team to prepare accurate plans for the safest and most efficient approach for the removal of the remaining fuel and disassembly of the vessel’s internal structures," said John Smith, DFR senior project manager.

"They are also assisting in the detailed planning now underway for the cleansing and/or destruction of the residual NaK remaining in the pipes and vessels of the DFR," he said, adding that further inspections would be undertaken prior to the NaK treatment.

The camera has now been removed and is available for re-use at a later date.