Assessment of the probability of WWER 440 heat transfer tube break

An overview is presented of the state of the art in the steam generator tube integrity assessment. Damage of the tubes is evaluated in terms of the nature of the defects and their occurrence in the operating conditions. The resistance of the tube against break was measured by the burst test method, the thinning of the WWER steam generator tubes was determined by the eddy current method. This parameters was used in correlation with the observed critical pressure to tube break in order to derive the limits for blinding. The probability of WWER steam generator tube break corresponding to the limits for blinding was determined for the Mochovce NPP for the 3-year and 4-year periods of in-service inspections. (author)