Safety against brittle fracture of the reactor pressure vessel in the nuclear power plant Obrigheim

Obrigheim, the first pressurized light water reactor built in Germany, operates with a nominal power of 357 MW. Since the beginning of electricity production in 1968 the nuclear power plant Obrigheim (KWO) has proved to be a reliable and safe operation with a high availability, in terms of time, of 81.4% over 29 years. The reactor pressure vessel could be qualified for future operation by means of inservice inspections, irradiation programs, fluence calculations, nondestructive testing, investigations of pressurized thermal shock (PTS) conditions and by implementation of technical improvements for operation and maintenance. The main steps of the final licensing procedure, for the qualification of the reactor pressure vessel relative to irradiation embrittlement and safety against brittle fracture under pressurized thermal shock conditions, are presented as a summary of investigations and experiences over more than 20 years.