Flow transients performance in an MTR-type research reactor

During a flow coastdown event leading to slowing down coolant flow, the rate of heat removal from the fuel element must be sufficiently high to prevent meltdown. It is essential to estimate the flow rate change and the decay heat removal capability. In many studies complete pump operating characteristics are used in analytical solutions of the problem. Under the coastdown phenomenon, retarding torque replaces motor torque. In order to determine this torque, all the induction motor losses during the event are identified and where possible these loss parameters are measured. Stator and rotor core losses, stator and rotor stray load losses and magnetizing saturation and rotor conductor skin effects are taken into account. The basics equations for coolant flow and for the rotating parts of the centrifugal pump are subsequently derived for an MTR-type research reactor such Tehran Research Reactor (TRR). Then the equation of flow motion is solved with another one which predicts the pump speed during the coastdown transient. The results of the present work are validated by comparison with experimental and analytical studies of the similar work. The model shows good agreement with the present literature.