Validation of the extended COCOSYS cable fire model based on a generic FLASH-CAT approach

Abstract

Fire simulations and analytical validation approaches have gained more and more relevance, in particular with respect to fire safety assessment of operating nuclear power plants (NPPs). For providing an added value to the regulatory authorities and the technical safety experts authorized by them suitability and applicability of the analytical tools applied such as fire simulation codes need be known and demonstrated.The COCOSYS (Containment Code System) code developed by Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) gGmbH contains i.e. models for simulating cable as well as liquid fuel fires. In NPPs, cables represent a non-negligible fire load as initial fire source or contributor to fire spreading.To overcome some generic deficiencies of the existing so-called simple cable fire model in COCOSYS the model has been improved based on a more generic FLASH-CAT approach. The extended model uses a time dependent mass loss rate (MLR) density profile, can consider composite materials to regard the increase of the heat of combustion during the fire development and is able to consider under-ventilated conditions.The model was validated on several experiments performed in open atmosphere and confined environment by the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN) and conducted within the PRISME 2 and PRISME 3 Projects, launched by the Organisation for Economic Co-operation and Development (OECD) Nuclear Energy Agency (NEA). One main objective is to provide one single set of input parameters for each cable type, which can be used under different ventilation conditions. The paper presents capabilities and remaining limitations of the new model.