Research on LWR safety

In this project it has been determined for the BBR PWR by emergency cooling analyses which minimum quantity of water will still be sufficient to protect the core from melting down, and at what point in time these minimum quantities of water have to be injected into the core at the latest. Starting with the degrees of availability of the emergency cooling systems required by the licensing procedure the number of effective primary side emergency cooling systems was systematically reduced and/or the times when they started injecting were delayed. A 2A - (double pipe cross section area) - rupture on the pump discharge side of the cold leg and the rupture of a connecting line of nominal width 100 were investigated. Realistic (best estimate) parameters were chosen for the starting and boundary conditions. The analyses of system behaviour have shown that alfter a 2A-rupture even a single low pressure injection system will be sufficient to prevent a core meltdown. To cope with the rupture of a pipe of nominal width 100 one high pressure injection system is sufficient. The allowable delay time of these systems which are necessary as the minimum are in a time range which would allow corrective measures to a limited extent only. It has been established altogether that system failures far beyond the licensing requirements have to be postulated before a loss-of-coolant accident could turn into a core meltdown accident. (orig./HP)