Validation of the dynamic simulation of a natural circulation loop

A natural circulation loop, or test rig, was built at the Chalk River Nuclear Laboratories for the investigation of the thermalhydraulic aspects of natural circulation at atmospheric pressure and corresponding subcooled or saturation temperatures. The test rig is a scale model of a small nuclear reactor intended for heating applications. A real-time, dynamic simulation of this test rig, code-named RIGSIM, has been developed and implemented on a hybrid computer. Step-transient experiments were carried out in the test rig to obtain the data for validating RIGSIM. Two series of tests were performed. In the first, a step change input, positive or negative, was applied to the test-section power; while in the second, the coolant-inlet temperature on the secondary side of the heat exchanger was stepped up or down. Results from both series of experiments show excellent agreement between RIGSIM predictions and experimental data, thus validating the RIGSIM simulation