Dounreay, Prototype Fast Reactor

Whilst 1994 had a sad start, particularly for fast reactors with the closure of the Dounreay Prototype Fast Reactor (PFR) the period since has seen many successes for the UK nuclear industry. The Utilities efforts have been rewarded with significant improvements in the operation efficiency of existing reactors and the UK s first Pressurised Water Reactor at Sizewell B achieved criticality on 31 January 1995. Good progress has also been achieved with a number of fuel cycle facilities which will make a major contribution to nuclear fuel recycle, ie ... 

Recent events in the energy field have emphasised the need for more thoughtful uses of energy and action on securing its transformation and its distribution. The fast breeder reactor has its natural, reasonable rate of development. The Dounreay prototype fast reactor has successfully ended its useful purpose in... 

Fig. 11.3. Sectional view of Dounreay Prototype Fast Reactor (courtesy of United Kingdom Atomic Energy Authority).

The Dounreay site was established as the site of the UK Fast Breeder Nuclear programme in 1955 and became operational in 1958. It accommodated three reactors, the Materials Test Reactor, (DMTR, 1958-1969), the Dounreay Fast Reactor (DFR, 1959-1977) and the Prototype Fast Reactor (PFR, 1974-1994). With all reactor operations now finished and the reactors already de-fuelled the site is undergoing active decommissioning which is planned to be completed by 2032. The Dounreay site has been cited by UKAEA as being the second biggest nuclear decommissioning challenge in the UK with similar liabilities to those at Sellafield but with smaller waste volumes. 

From ref. 245 PFR = Prototype Fast Reactor at Dounreay, UK HLW= High Level Waste in which the bulk of the fission products (FP) are concentrated. 

Figure 47 An outline flowsheet for the reprocessing of Prototype Fast Reactor fuel at Dounreay Table 14 Equilibrium Constants " for Nitrate Complexes of Pa ...

PROBLEMS EXPERIENCED DURING OPERATION OF THE PROTOTYPE FAST REACTOR, DOUNREAY, 1974-1994... 

Two years ago an experiment was carried out by the UK Atomic Energy Authority on the Prototype Fast Reactor at Dounreay, to establish whether ultrasonic imaging could be carried out beneath the sodium. The success of this experiment has given confidence in the eventual use of ultrasonics for under sodium inspection. Under-soUium ultrasonics cannot as yet match inspection techniques that can be applied in a more amenable situation. However it seems likely that it can provide the equivalent of visual examinations. 

A total of ten nuclear power reactors have been taken out of service including the experimental and prototype fast reactors (DFR and PFR) at Dounreay and are in various early stages of decommissioning. 

ADAM, E.R., GREGORY, C.V., Brief History of the Operation of the Prototype Fast Reactor at Dounreay, The Nuclear Engineer, 35 (1994) 112-117. 

My first encounter with the operational challenges of ensuring pressure vessel safety came at Dounreay in northern Scotland, at the prototype fast reactor (PFR), in 1981. PFR was a highly unusual power station since the reactor was cooled by liqnid sodium. PFR had three identical sodium-heated boiler circuits, each containing a boiler, a steam drum, a superheater and a reheater (Fig. 7.8). 

In the UK, the Prototype Fast Reactor at Dounreay in northern Scotland was an early adopter of computer control systems in industrial safety-related applications. The PFR was designed in the early 1970s and used dual-redundant Ferranti Argus 500 computers for plant indications, alarm messages and some control functions. 

Work at Dounreay site had begun in 1955. By 1979, the site was huge and employed some 2500 people. The site was divided between the fuel cycle area where used fuel was reprocessed, and the Prototype Fast Reactor (or PHi) itself which could generate enough electricity for a city. There was also a smaller fast reactor, the original Doumeay Fast Reactor (with its iconic golf ball containment building) that had shutdown in 1977. 

The Prototype Fast Reactor, PFR, was built and operated at the United Kingdom Atomic Energy Authority s site at Dounreay in Scotland to validate and provide operational experience of a large pool-type fast reactor and as a test bed for the fuel, components, materials and instrumentation needed for an eventual commercial-sized station It represented... 

The problem becomes much more acute in a fast reactor, where there is no moderator to slow down the neutrons. This means the core is far smaller, and megawatts of heat may be generated in very small volumes. In these reactors, liquid metals are the only viable option — the Dounreay Fast Reactor used sodium-potassium alloy and the Prototype Fast Reactor used liquid sodium. 

The experimental fast breeder reactor was considered to be something of a potential hazard, and a remote site was needed in case of accident As mentioned above, the site chosen was Dounreay, on the northern coast of Caithness, in the Scottish Highlands. Two fast reactors would be built there one which would be known as the Dounreay fast reactor (DFR), and the other being the prototype fast reactor (PFR). In a sense the DFR was the prototype the second reactor was intended as a prototype for a commercial fast reactor which never materialised. 

The programme involves the major facilities at Dounreay in Caithness — the prototype fast reactor, known as the PFR, which started operation in 1974... 

We recognise that there is continuing benefit to be secured from operation of the prototype fast reactor. We have therefore decided to fund the reactor until the end of the financial year 1993-94. This will enable operating experience to accumulate for a further five years. We have also decided to fund the reprocessing plant at Dounreay until 1996-97, to process spent fuel from the reactor. Our decisions will ensure continuing and substantial employment at Dounreay into the late 1990s. 

Today, there is a considerable degree of local opposition to any new development, in particular to nuclear power, in what has been described as NIMBYism (Not In My Back Yard). This was not always the case. A letter written by the town clerk of Wick, the nearest town to Dounreay, in 1963, concenung the proposed prototype fast reactor is not a letter which could be written today. 

The apparatus for obtaining images of the core of the prototype nuclear fast reactor at Dounreay has demonstrated the value of ultrasonic techniques under hot liquid sodium. A considerable amount of valuable data was obtained, and in addition experience was gained for future developments. The potential of imaging devices for sodium-cooled fast reactors is now established. 

The liquid metal-cooled option would require a very great deal of development and would probably have been an over-ambitious choice for a British submarine reactor (the Dounreay fast reactor, which was liquid metal cooled, first went critical in November 1959). The United States Navy s second nuclear submarine, USS Seawolf, which was launched in July 1955 and commissioned in March 1957, used a liquid sodium cooled reactor. It was not regarded as a success, and was only operational for a short period before being replaced by a PWR, which would then become standard in the United States Navy. Harwell was also taking some interest in a PWR at this time, with plans to build a prototype to be named LEO. It thus made sense for the Admiralty to work in parallel with Harwell on a water-cooled reactor. 

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