Safety of chemical processes and plants is a matter of high priority. The design of an inherently safer process is one of very beneficial ways of achieving this goal. The paper describes the method of designing an inherently safer process for a chosen set of equipment and materials involved by applying non-linear optimization. The optimization is aimed at finding an operational mode, which guarantees safety of the process under normal conditions and provides maximal attainable safety in case of one typical accident scenario - cooling failure. Discussion covers problem statement, choice of the optimization criteria, appropriate methods for defining control variables. An important practical challenge is stability analysis of the optimized process mode with respect to permissible deviations of control parameters and variables from the estimated values. The original method for the stability analysis of a non-stationary process is proposed. It comprises simplified preliminary evaluation method followed by the more detailed numerical optimization-based analysis. Several examples illustrate application of the methods proposed. (C) 2012 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.