Half of the last remaining radioactive fuel elements jammed for decades inside the Dounreay Fast Reactor (DFR) in northern Scotland have now been removed, Dounreay Site Restoration Ltd (DSRL) announced on 11 October.
DFR achieved criticality in 1959 and in 1962 became the world's first fast reactor to supply electricity to the grid achieving a maximum electrical power of 14.5MWe. The DFR, which was cooled by a liquid sodium-potassium alloy, has a core surrounded by a blanket of natural uranium elements that, when exposed to radiation, would “breed” to create a new fuel, plutonium. After the reactor closed in 1977 most of the core fuel was removed. However, work to remove elements from the breeder zone stopped when some were found to be swollen and jammed. Almost 1000, comprising some two-thirds of the total, were left in place.
DSRL said decommissioning the DFR is one of the most technically challenging projects in the Nuclear Decommissioning Authority estate and removing the breeder elements has been a "top priority". After designing and testing remotely-operated equipment, a decommissioning team started recovering the elements in 2017, using purpose-built tools that reached down into the reactor to cut the breeder elements free and lift them into a flask for removal.
Locally manufactured tooling has played a big part in the removal of the radioactive fuel inventory inside the reactor vessel. Companies manufactured mechanical equipment to demanding timescales included JGC Engineering and Technical, Precision Machining Services, and Calder Engineering. Contec Design Services carried out electrical, control and instrumentation works.
Photo: Dounreay Fast Reactor (DFR)