Version 2 of the ISIS computer code, software for the digital simulation of fires in nuclear installations developed at the IRSN's Fire Research and Development of Uncertainty and Simulation Methods Laboratory (Limsi) has been available as open source software on the Internet since January 2010.
This new version contains improvements to the models that were in the previous version, and features the addition of a pyrolysis model.
The radiation model initially formulated for opaque media is now valid for a semi-transparent gray medium. This model can be used to calculate the radiation intensity emitted by a fire and to correctly predict the heat flows received by the walls of the rooms where the fire is burning. The soot production models have also evolved, providing finer handling of the soot production, oxidation, and transport processes.
The pyrolysis model available in this new version will allow users to calculate the power released by the fire, which constitutes a first step in the predictive simulation of fires. Until now, this crucial piece of data for the problem had been supplied by the user as part of the data set for the software.
When evaluated during a benchmarking process organized in the context of the international PRISME program conducted by IRSN under the auspices of the OECD, the new version of ISIS produced results deemed to be very satisfactory, of comparable quality to those of the FDS computer code developed by NIST (USA). ISIS will soon be enriched with new models developed by the Laboratory for the Study of Fire in a Contained Environment (Etic), a joint fire research unit created in 2010 by the IRSN and the University Institute for Industrial Thermal Systems (IUSTI).