Phenomenological investigation of loss of coolant accident in a research reactor facility

A systematic approach is proposed for describing the thermal hydraulic phenomena taking place during a loss-of-coolant accident in a research reactor facility. The phenomenological investigation is performed employing the RELAP5/MOD3.3 best estimate code in a parametric analysis of loss of coolant transients in the Greek Research Reactor-1 (GRR-1) facility. The results obtained demonstrate the significance of the pipe break location and severity in the transient evolution and reveal the effect of important safety components such as the flappers. As a means for presenting the wealth of information obtained during event development, a “TH phenomena regime map” (also known as “TH map”) is introduced. It is a graphical tool summarizing the accident progression in a user-friendly manner that could be useful in training and decision making.