Technical feasibility and costs of the retention of radionuclides during accidents in nuclear power plants demonstrated by the example of a pressurized water reactor

The maximum allowable radiation doses during accidents in nuclear power plants, i.e., 5 rem whole-body dose and 15 rem thyroid dose, have been laid down in the German Radiation Protection Act. In order to ensure that these limits are not exceeded for all exposure paths including the ingestion path or, if possible, to remain far below them, the Federal Ministry of the Interior has initiated a study on the effectiveness and cost of additional safety features for reducing the release of activity and the dose exposure during accidents in nuclear power plants. Detailed investigations were carried out for the following three radiologically representative types of accidents: break of a reactor coolant line, break of an instrument line in one of the outer ring rooms, and break of a main stream line outside the containment. The technical basis of the study was a BBR-type nuclear power plant with pressurized water reactor and once-through steam generator. I-131 was chosen for determining the activity release as this is the critical nuclide for the ingestion path. Altogether 33 feasible technical measures were investigated and their potential improvement was assessed