Experimental Study of MTR Core Cooling after Pump Coast-Down In MTR pool Type Research Reactors

This study presents experimental investigations on core cooling of MTR pool type research reactor at later stages of pump coast down. The study aims to clarify the effect of the reactor pool temperature on the core cooling during these stages. Test rig is designed and built to simulate the MTR core cooling loop at later stages of pump coast down and after the opening of the natural convection valve. The core is simulated as two channels, one represents the core hottest channel and the other represents the average or less power channel. Each channel consists of two aluminum plates heated by electrical heater uniformly distributed on the plate's outer surfaces. Due to the expected shallow core flow at later stages of Pump coast down, the analysis is based on measuring the temperature distribution through the coolant and plate's inner surface. The measurements are taken at different reactor pool and return pipe temperature s. Also some measurements are taken at different channel powers.The experimental results show that at this stage of shallow flow the flow direction in the core channels depends on the reactor pool and return pipe temperature. Sometimes an upward flow is established in the two channels and in others the flow is upward in hot channel and downward in colder channel. Also, for power ratios (Pav/Phot) less than one, the inner circulation between the channels is more sus ceptible in spite of the high temperature difference between the reactor pool and return pipe temperature. In addition, the comparison with the theoretical results shows that there is a good agreement between RELAP5 results and the obtained experimental results.