Study Of Jamming Phenomenon For High Temperature Gas Cooled Reactor

In the core area of the High Temperature Gas Cooled Reactor,the fuel balls may get blocked during transportation,and as a result an arch may be formed in the conical part at the bottom.Once the blockage occurs,the refueling stops,which may cause serious consequences.Discrete numerical simulations and extensive experimentations are used to study the influence of container’s geometry on probability of jamming J.The height of the pebble-bed h and the angle of the conical hopper a are among our varied parameters.By increasing the angle of the conical hopper a,the probability of jamming remains almost constant till α=40°,then decreases when α≥60°,which is due to the influence of angle on the granular flow pattern and the fact that α=60° is almost the critical angle of repose of the flow.The results have shown that height has a crucial effect on jamming probability when h is smaller than a critical value,flow becomes more susceptible to jamming if we increase h,when h exceeds this critical value,J approaches unity.To understand the underlying physical mechanism,we computed the average total stress near the aperture during the discharge and measured it for various h.The trace of stress tensor tr[σij]increases when h increases.One can conclude that the inner pressure of particles has an imperative effect on the probability of jamming.Furthermore,an exponential law between the pebble bed h and jamming probability J has been establised based on these observations and Janssen model.An obstacle in form of a circular disc has been inserted and tested at verious obstacle heights ho and some obstacle sizes ro.The pressure variations originated by obstacle are plotted against the jamming phenomenon to understand its effect in detail.Results and trends instigated from our simulation techniques are then finally endorsed by the our experimental techniques to exhibit a better picture of our work.