An assessment of the effect of the Sizewell power stations on fish populations

Abstract

Sizewell A and B Nuclear Power Stations are located on the Suffolk coast of East Anglia. The A station is a 650 MWe Magnox plant, completed in 1966 and operated by British Nuclear Fuels; the B station is a 1258 MWe pressurised water reactor (PWR), commissioned in 1995 and operated by British Energy Generation Ltd. Both power stations are direct cooled and rely on abstractions of cooling water (CW) from the North Sea: together they can abstract some 80 m3s-'. The water is passed around the plant condenser circuits and returned to the sea, along with reject heat and any chlorine residues from antifouling treatment. The abstraction of this water is accompanied , to some extent unavoidably, by entrained fish present either as ichthyoplankton (eggs, larvae and postlarvae of fish), or as fully-formed juvenile or adult fish which have to be removed by mechanical screening systems ('drum' screens) to avoid CW con-denser blockage. The entrained ichthyoplankton passes through the entire cooling system and is discharged back to sea along with the heated water. The later life stages of fish and other material that become impinged upon the drum screens are removed from the water. At Sizewell B provision is made to return the more robust species of fish back to the sea alive. In the late 1970% the Central Electricity Generating Board (CEGB), then owner of the whole Sizewell site, announced plans to build the PWR power station which was to become known as Sizewell B. Local fishermen lodged an objection to the scheme on the grounds that the mortality of juvenile fish on the drum screens might be increased to an unacceptable level. Between 1981 and 1982 a joint study of the fish catch was carried out by the CEGB and the Ministry of Agriculture, Fisheries and Food (MAFF). This study showed that the losses on the A station of commercially important species, including plaice (Pleuronectes platessa), sole (Solea solea), dab (Limanda limanda), cod (Gadus morhua), whiting (Merlangius merlangus) and herring (Clupea harengus), amounted to 66 tonnes per year (t y '), then valued at £28,000 per annum. This estimate included an allowance for the potential yield of fish which were below the statutory minimum landing