Simplified method for risk oriented design of structural fire protection measures

On behalf of the German Federal Government a risk oriented simplified method for structural fire protection measures in nuclear power plants (NPP) based on a calculated fire load density qR has been developed. The burning behaviour of combustibles is described by the efficiency of combustion χ. Depending on ventilation conditions, room geometry, fire load density and fuel distribution, the heating up of structural elements is calculated by means of a fire simulation zone model in multiple room configuration. The estimated temperature distribution within the structural element is compared with the temperature distribution gained by the fire conditions described by the standard temperature-time curve (ISO 834) and provides the equivalent time of fire exposure. The simplified design method needs only few empirical functions and design curves which are derived from systematic fire simulation calculations. The described method yields results which are in good correspondence with results from large-scale room fire tests and is comparable to other design methods, e.g. the method as applied in the German standard DIN 18230-1. In addition, heat sinks (e.g. large machines or reservoirs/vessels with fluids) can easily be considered by this methodology. (orig.)