Industrial large-scale urea production creates a number of hazards due to equipment and machine failures as well as service errors. Failures can cause material, environmental and human losses. The work presents the assessment of safety hazards and failure effects for selected emergency scenarios of Mitsui - Toatsu's urea synthesis reactor. A fragment of the process implemented in the synthesis node was covered by HAZOP (Hazard and Operability Study), and the critical points, from the security point of view, were identified. Several emergency scenarios for various types of failures and various effects are presented. The analyzed contingency scenarios include: blocking the valve on the outflow from the reactor and leaks caused by corrosion resulting from the maintenance of improper technological parameters of the process. The work suggested the need for new security measures and modernization of the installation by using the safety function for the selected critical point. The hazards analyzed and the contingency scenarios developed are essential for risk assessment and its possible reduction.