Study of the possibility of switching from natural to forced convection cooling during research reactor operation

This paper studies the possibility of switching from natural to forced convection cooling during research reactor operation using a coupled thermal-hydraulic and kinetics model. The switching to forced convection during operation of an open pool MTR (Material Testing Reactor) has been modeled and the results of switching transients are discussed. It is shown that a significant and fast decrease of the core temperature is induced during operation resulting in positive reactivity feedback and accidental power increase. Such a situation is not accepted from safety point of view. The limiting conditions to compensate the reactivity feedback and limit the significant and fast decrease of the core temperature are also discussed and possible solutions are proposed based on the results.