Prototype Fast Reactor
Dounreay's Prototype Fast Reactor (PFR) was the second and last fast reactor to be built in the UK. The success of the experimental fast reactor at Dounreay led the British government in 1966 to order a prototype fast reactor power plant.
Construction commenced in 1968 and PFR went critical in 1974.
PFR had the dual role of providing power to the national grid and offering unique research and development facilities. PFR provided information for future design and operation of large commercial fast reactor stations. It was the final step towards bringing fast reactors into use as conventional power stations. But by the late 1980s, Britain decided there was no immediate need for such a development and shelved the programme.
The reactor was 250 MW electrical (660 MW thermal output, although the original design intent was 600 MW).
The plutonium metal fuel was cooled by sodium liquid metal designed to remove heat from the reactor core. This heat was transferred via the primary and secondary sodium circuits to the steam raising plant which fed a conventional steam turbine with an electrical output.
The reactor closed in 1994. It was de-fuelled and the 1,500 tonnes of bulk sodium that once flowed through the primary and secondary circuits removed. The world’s largest liquid metal destruction plant was built at PFR to destroy this sodium, and destruction of the bulk sodium was completed in August 2008.
PFR also incorporated fuel research and development. A shielded remote handling facility, known as the Irradiated Fuel Cave (IFC), was constructed. This facility contained approximately 70 tonnes of liquid sodium in a number of storage tanks. This sodium has been drained and destroyed and the next step is to cleanse the residue from this area. The structure will be decommissioned in parallel with the reactor vessel.
PFR's decommissioning programme is designed to lower the overall hazard by prioritised removal of hazards:
- complete destruction of 1,500 tonnes of bulk sodium coolant through the sodium disposal plant.
- removal of sodium residues using the water vapour nitrogen process and destruction of the sodium through the sodium disposal plant.
- design, construction and operation of a reactor vessel dismantling facility and associated waste handling facilities.
- design, construction and operation of a waste size-reduction facility and waste packaging plants to deal with major components from the reactor, as well as intermediate level waste arising from the irradiated fuel cave produced during their dismantling.
- decommission and demolish all remaining facilities and buildings.
- backfill of underground structures ranging in size from drains to the reactor vessel vault, which is 13 m in diameter and approximately 18 m deep.
- reinstatement of the ground to a brown field condition.
This work requires a range of supporting activities to prepare the reactor, floor area and infrastructure for the major engineering tasks, including:
- strip-out of electrical services from the west wall of the reactor hall.
- strip-out of the reactor top auxiliary services.
- removal of all asbestos clad cabling.
- removal of reactor top instrumentation.
Decommissioning PFR between 2008 and 2024 is expected to cost in the region of £338 million.
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