Structural Steel in the Nuclear Power Industry

From Building with Steel
February 1960

Structural steelwork is marching with the times. Nuclear power stations – virtually unthought of a decade ago – are consuming large quantities of struc­tural steelwork in both new and traditional applications. Windscale, Britain’s first large venture into the atomic energy field, used 17,000 tons; the atomic factory at Capenhurst used an initial quantity of 20,000 tons and then called for more in order to extend; at Dounreay, more than 5,000 tons were used. The ‘true’ power sta­tions now being built are using even more, and for purposes varying from conventional girder structures to mammoth cranes as tall as Nelson’s Column.

THE EARLY DAYS

Like so many things invented by man, the first nuclear reactors were built for warlike purposes. The U.S.A. employed the first ones to produce military plutonium, and Britain’s first atomic plant – at Wind­scale – was built for the same reason.

Calder Hall saw the beginning of the nuclear elec­tricity era: the electricity here being a secondary product of the plutonium plant. That was just over three years ago. Today a new power station at Chapelcross, the first to be built primarily as a power station, is in opera­tion. Others, in differing stages of construction, are going up at Bradwell, Berkeley, Hinkley Point, Hunterston, and Trawsfynydd. Britain is now well on the way towards achieving the generating capacity called for in the 1955 White Paper: twelve stations generating between 1,500,000 and 2,000,000 kW. by 1965.

WINDSCALE AND DOUNREAY

Seventeen thousand tons of structural steelwork: that was the first indication industry received of the quantities likely to be required by the programme and was the amount employed in the buildings and other structures at Windscale. Although Windscale produces plutonium and not electricity, it is important in that it was the first large-scale unit built in Britain’s military programme in this field. The buildings are con­spicuously different from those at a civil nuclear power station, the site being dominated by two giant chimneys each 414 ft. tall. On top of each of these is a 200-ton steel filter assembly – rather like storks’ nests.

Dounreay is capable of contributing 15,000 kW. to the National Grid. It was built primarily as a fast breeder reactor research station and, like Windscale, differs considerably from conventional power stations in appearance. Here, everything else on the site is dwarfed by the containment sphere. Five thousand tons of structural steelwork were used at Dounreay, much of it in connection with this sphere. The steelwork was used principally in the form of lattice-type straight and radial girders, floors, columns, and crane girders. The seven-floor active element store building – 86 ft. high by 55 ft. by 66 ft. – is of beam and stanchion construc­tion; it has seven floors, some of which are chequer plated.

To the west of the sphere is the heat exchange build­ing, also of beam and stanchion construction. This has five floors, four of which are chequer plated, with castellated beams at one of the floor levels.

CALDER HALL

The Turbine Hall – Calder Hall’s principal struc­ture – is set almost on a north-south line. It is a steel-­framed building of portal-type design, and is of 78 ft. span by 58 ft. high by 242 ft. long. To the east of this is a steel-framed annexe, with a somewhat larger one to the west. Both annexes run the full length of the Turbine Hall. Each gable end of the Turbine Hall is connected to the face side of the reactors by a series of structural steel pipe bridges.

Each reactor building is composed of an octagonal concrete Biological Shield – 60 ft. across the flat sides of the octagon by 81 ft. 8 in. high, with 7 ft. thick walls. The reactors are also bounded by concrete walls on their east and west sides. Between the octagonal and rectangular walls steel floorwork – known as the envelope wall steelwork – has been erected at four levels.

To the east of the concrete shield is the Long Blower House, again a steel-framed structure of portal-type design. This is a building of 58 ft. span by 110 ft. long by 42 ft. high, to the west of which is the Short Blower House of similar construction.

The steel-framed Control Room is sited to the north of the Shield. It extends 50 ft. from the outside face of the Biological Shield and has eight steel floors, three of them covered with chequer plate decking.

The Discharge Side of the Shield, on the south, is occupied by a similar building which extends 19 ft. from the Shield’s face.

Joining the Control and Discharge sides – running roughly north-south – is a steel structure which sup­ports a complete roof over Control Side, Biological Shield, and Discharge Side; this is equipped with crane and gantry. The pipe bridges connecting the Turbine Hall and Control Side are of box-type lattice girder design sup­ported by rectangular lattice steel towers. There are 360 linear ft. of box girders, generally 80 ft. span by 10 ft. deep, with widths of either 6 ft. or 13 ft. The supporting towers are 15 ft. by 13 ft. by 27 ft. high.

The Administrative Block is to the east of, and parallel to, the Turbine Hall. Steel beam and stanchion construction was used for the 30 ft. span by 242 ft. long by 20 ft. high building, along the west side and at the north of which is the workshop annexe.

An additional feature called for at Calder Hall was a permanent bridge over the River Calder. This is of box-type lattice girder construction, 7 ft. deep by 6 ft. 5 in. wide by 294 ft. long. It is supported by inter­mediate trestles with 24 ft. 6 in. steel towers at each end.

THE GOLIATH CRANE

Besides being used extensively in the permanent structures at power stations, structural steelwork is also called upon to fulfil equally vital but temporary roles. For instance, a great deal of heavy lifting work has to be done to install reactor and other vessels. Conven­tional cranes cannot cope with the loads and heights involved and special forms of lifting gear have been de­vised to carry out this work. Typical of these is the Goliath crane used at Bradwell-on-Sea, Essex. This is of the overhead girder type, and is supported at each end by a leg mounted on eight, four-wheel bogies. The crane straddles the reactor building during all stages of construction and is designed to lift 200 tons to a height of 140 ft.; an auxiliary hoist can lift 30 tons.

COMING SHORTLY

Calder Hall set the pattern of scientific and industrial co-operation which has since been developed and in­creased. Industry, recognizing the need for further collaboration within itself, has formed a number of consortia which are now working in different parts of the country – and abroad – to ensure that Britain main­tains the lead and prestige that Calder Hall first gave her.

Here we have summarised the activities in just a few of the many directions in which nuclear power is lead­ing. More has been done – and is being done – than we have the space to deal with. Before long, Wales will have her own nuclear power station by the picturesque waters of Trawsfynydd – using an initial 4,500 tons of structural steelwork; England and Scotland will have additional ones where they are most needed; Japan and Italy, too, are to benefit from British ability in this field.

The designs so far have not changed much since Calder Hall was built – but they will. Calder Hall has been called the ‘Model-T Ford’ of the nuclear power industry. The critic should have remembered that the Model-T Ford engine survived virtually unchanged for very many years. Whether Britain decides to stick to the Model-T or to develop new and improved de­signs, the designers are secure in the knowledge that whatever they require from the structural steelwork industry they will receive.

Calder Hall proved the suitability of steel for the tasks assigned to it; its inherent adaptability ensures that, like the nuclear power industry itself, steel will continue to measure up to any new demands that may be made.