Overheating of reactors in the polyolefin chemical process industry, sometimes leads to complete plant shutdown. This is due to catalyst overheating, which creates strings and lumps and undesirable agglomeration within the reactor with highly concentrated hot spots. Fresh research on this problem is carried out using numerical analysis to model the heat removal mechanisms in Polyolefin Gas Phase Reactors. Up to now, it was thought that the main factor preventing overheating and associated problems in reactor stability was the heat transfer from the catalyst to the gas phase. Numerical analysis has shown that the main solution to reactor overheating problems is the direct heat transfer from the fresh catalyst to the powder bed. Therefore, this new result is to have consequences in new methods design for the fresh catalyst feed into gas-phase reactors. It is now clear that in order to prevent strings and lumps, it is necessary to have a very rapid individual mixing of fresh catalyst. This has to be designed in a process specific manner so that sufficient refreshment of powder in the spraying zone occurs, in order for the catalyst to stick to the polymer surface as separate particles. The method used to achieve this should be developed further by each polyolefin producer in a proprietary way, including the design of advanced control systems, methods of prediction and avoidance of reactor melt-down.