Protection against high energy line breaks in WWER power plants

This contribution describes the procedure used in the protection of safety relevant systems and equipment against high energy line breaks in WWER power plants, which are in operation or in the construction phase. The investigations are based on the American standards and regulations for the postulation of ruptures described in ANSI/ANS 58.2 and in the Standard Review Plan, Section 3.6.2. Pipe ruptures are postulated on the basis of piping stress analyses of the normal and upset loading conditions. If stress indices are not available for special piping parts detailed analyses are carried out. The modification of piping supports with the aim to reduce stresses and to reduce the number of rupture postulates is also considered as a protection measure. The procedure for the investigation of the effect of jet impingement loads and of pipe whip impacts is discussed and newly created protection measures, which take into account the limited space and the limited load capability of surrounding structures are presented. (orig.)