Cleavage behaviors in nuclear vessel steels

Cleavage behaviors of nuclear vessel steels in the transition temperature range are reviewed. View points are presented which assist understanding of cleavage crack speed, cleavage initiation, cleavage arrest, and the sensitivity of fracture toughness to constrain and temperature. The importance of high local stress elevations by high strain rate is emphasized. In order to assist understanding and efficient use of fracture toughness measurements for nuclear vessel steels, a number of fractographic studies have been made. This paper discusses cleavage behaviors in the transition temperature range from near NDT to loss-of-cleavage temperature. In addition, viewpoints are presented which are supported both by what is seen, with SEM and optical fractography, and by results from theoretical analysis