European Project “Supercritical Water Reactor–Fuel Qualification Test”: Results of Fuel Pin Mock-up Tests

The main target of the EURATOM FP7 project “fuel qualification test for supercritical water-cooled reactor” was to make significant progress toward the design, analysis, and licensing of a fuel assembly cooled with supercritical water (SCW) in a research reactor. Within the project, fuel pin mock-ups of a future fuel qualification test facility were designed and manufactured by Centrum Výzkumu Řež (CVR). Following that, it was decided to conduct three different types of tests considering two possible accident scenarios. Simulation of loss of external pressure was the target of Test 1. The autoclave was depressurized as fast as possible from 20 to 1 MPa by opening the close valve located behind the cooling part of the high-pressure part of the loop. Pressure inside the pin was held at a constant value of 20 MPa by pumping high-pressure water via the pin and in parallel via a separate relief valve that was connected directly to the pin using the filling pressure tube. A similar approach was chosen when the opposite case, i.e., loss of internal pressure in the pin, was simulated in Test 2A. Eventually, Test 2A was repeated with modified setup to determine the lower limit of the internal pin pressure (i.e., collapse/buckling of the pin due to external overpressure) more accurately. The presented paper summarizes the results of all three performed tests.