AP600 gets results, ahead of schedule

The first phase of a test programme on the safety systems of a one quarter size scale model of the proposed AP600 Westinghouse reactor is reported. The AP600 is a 600 MWe two loop, advanced reactor with passive safety systems. Thermal/hydraulic tests are being carried on the scale model in which the nuclear core of a full-scale reactor is replaced by electric heating rods. Attention is being focussed on the passive safety core cooling systems. The major elements are a steel reactor containment shell surrounded by a concrete shield building, between which there is natural air conditioning, and large volumes of gravity-fed water stored in tanks above the reactor. In performing the principal safety functions such as primary coolant inventory control, reactivity control and residual heat removal, the passive systems rely on the natural forces of condensation, evaporation and gravity. Because there is no reliance on mechanical equipment, as in ''active'' systems, no human intervention is required. Encouraging results have been obtained for the passive systems. (UK)