Development of a probabilistic risk assessment (PRA) methodology for nuclear power plants has been performed over past decades. Particularly, for Fire PRA, the results of a detailed evaluation by the fire prediction models are required for each scenario involving multi-room fire, multi-fire sources, under mechanical-ventilated system and so on, and the related studies are underway to advance the fire prediction models.

As a fire prediction model predicting fire characteristics in a compartment, a two-zone model, which divides the fire room into the hot smoke upper layer and lower layer consist of cool fresh air, is widely used due to the advantages of the brevity of the calculation routine and the reliability of calculation results. Among them, the BRI2 series, developed in Japan, is now reaching the current BRI2002 after several upgrades to improve calculation precision.

However, since the current BRI2002 requires design fire, namely either ‘scheduled heat release rate’ or ‘scheduled burning rate (mass loss rate of fuel)’ as an input data, therefore, it is need to generic user that some degree of knowledge about fire engineering, and it may affect to calculation results.

To solve this problem, in this study, improvement of BRI2002 was carried out in order to calculate directly the heat release rate from fire source by considering heat flux to a fire source.

Assuming the flame shape in the form of a cylinder, thermal radiation effect, in other words, thermal feedback from flame to pool fire source was considered as well as heat feedback from smoke layer, near walls and hot ceiling surface.

Meanwhile, in order to calculate the reduction of the heat release rate due to the decrease of oxygen concentration in the fire room, the correlation between the equivalence ratio and the combustion efficiency is modeled. The equivalence ratio is obtained from both the burning rate of the fuel (amount of vaporized fuel mass from the pool fire source) and the air flow rate into the plume. To consider the situation when oxygen concentration is under 21%, equivalence ratio was calculated using oxygen mass (NOT air mass).

The calculation results such as heat release rate and zone temperature were well corresponded with full-scale experimental data that was tested with various ventilation conditions.


Development of Advanced Fire Zone Model Applicable to Fire PRA for Nuclear Power Plant

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

POWER-ICONE - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.