Inerting system and pressure relief system with filtered venting in KWU BWRs

The owners of boiling water reactors of the 1969 type (BWR 69) in the Federal Republic of Germany have decided voluntarily to build an inerting system and a pressure relief system with filtered venting in order to strengthen the containment vessel in the event of severe accidents beyond the design basis. First, the relevant sequences and the design requirements for these systems are described. Secondly, the technical solutions for these measures are considered from the point of view of the scheduled realization and the expected cost. Finally, rough evaluations of the radiological efficiency of a pressure relief system with filtered venting are made. The bases for the calculations and evaluations were not experimentally verified and therefore conservative data had to be used and many assumptions had to be made. The chosen sequences were meant to cover other postulated events, envelop the problems and allow the new systems to be dimensioned. The installations are emergency measures; they are intended to be flexible instruments and serve to mitigate the consequences of beyond design basis accidents. (author). 6 refs, 7 figs, 2 tabs