Determination of safety factors for admissibility assessment of defects in WWER-440 pressure vessel materials

In assessing the admissibility of defects, so-called safety factors have to be included in the calculations. These factors in principle compensate for the inaccuracies of the starting values, as are the dimensions of the defects, some material properties such as the critical temperature of embrittlement, etc. A definition of the safety factors is given, based mainly on the stress intensity factor. Relations for safety factors are then derived for both ferritic materials of reactor pressure vessels and austenitic materials of primary coolant circuits. The relations are always given for three situations: normal operation, pressure tests and operation under abnormal conditions, and accident situations. (A.K.) 3 refs