The dynamics of a fed-batch reactor was studied using the detailed first principle model of the system. The conditions of reaction runaway, the typical sources of hazardous operation in fed-batch techniques are determined. Considering these conditions a model-based control scheme is proposed to ensure robustness. When the stability criterion predicts that the range of operation is safe the cooling is set to its maximum and the temperature is controlled by the reactant feed. Otherwise the reactant feed is stopped and the flow rate of the cooling medium is the control variable.