Sizewell B

Steam generator tube integrity and the possibility of multiple tube failures arising from circumferentially-orientated intergranular attack in the residual crevice at the top of the tube-plate are discussed. Unreliability of non-destructive examination (NDE) techniques has been exhibited in the detection of intergranular attack; its presence has been undetected until tubes have been cut out for other reasons. It is concluded that the safety case for steam generator tube integrity is satisfactory for licensing provided that a reliable NDE technique is demonstrated. (U.K.)