System for the automatic switching off feeding between two parallel lines of an emergency cooling system for water-cooled nuclear reactors

The safety feeding of a PWR designs, amongst others, a feeding system. This is divided into two lines to increase the safety so that if one of the lines breaks it is automatically switched over to the other line, the switching over taking place via a piston-guided three-way valve. A high-pressure pump is placed in front of the three-way value whilst the two lines leading off open out in the low-pressure feedpipe. The driving piston is connected on both sides with a line each via a control pipe. The valve plate normally rests on the lower valve seat due to gravitational effect. The three-way valve thus works without any help. For further safety, two three-way valves can be connected one behind the other where if one should fail, one can switch over to other. (TK/LH)