A complex study on the reliability assessment of the containment of a PWR. I

For evaluation of the reliability of the safety enclosure in the case of accidents the time-dependent loads by internal pressure and temperature on the spheric steel containment and the correspondent probabilities had to be calculated. Of the spectrum of possible accidents, e.g. large LOCA which leads to a maximum pressure of approximately 4.7 bar, working of all safety systems presumed, small LOCA or rupture of a primary steam pipe, only those have been selected which result in a considerable increase of internal pressure in the safety containment. Technical data and accident event sequences describing the system analysed were taken from the PWR Biblis B, which at this time is typical for the PWR-line construction in the FRG. The computer code ZOCO VI was used to calculate pressure buildup for the different event sequences. The probability of certain event sequences leading to an accident has been calculated by multiplication of probabilities P1 X P2 X P3 X P4. The values have been determined by fault tree analysis of the different systems. (Auth.)