Tests in the ATLE Loop on the PIUS design

The self-protective thermal hydraulic design of the primary system that prevents reactor power from exceeding the coolant capability of the submerging water independent of outside surveillance and supervision is a fundamental feature of the PIUS design. The experimental demonstration of the self-protective features of the primary system in a large scale test loop (the ATLE Loop) in the ABB Atom Engineering Laboratories are described in the paper. The volume scale of the ATLE Loop is approximately 1:300. The height of the test loop is the same as in the full scale design to ensure similarity in the driving buoyancy force during a transient. The test loop includes the following: one electrically heated, simulated fuel assembly, reactor pool, primary systems, upper and lower density locks and heat exchangers. System response to various severe transients and normal operations was studied. Comparisons were made with the predictions of the RIGEL code, which has been developed by ABB Atom specifically for study of the PIUS design and its predecessor designs. Selected results of these studies and comparison of these results with predictions obtained using RIGEL are presented in this paper