Investigation of fire temperature regime in an underground research laboratory based on numerical modelling

Introduction. Justification of safety of operation of an underground research laboratory for the final isolation of radioactive waste requires, among other things, an assessment of the fire resistance of the rock in which it is constructed. In this case, the choice of the main parameters of the corresponding fire tests is determined by the temperature regime, as well as the duration of heating of the rock during the fire. One of the effective ways to assess these factors, in conditions where there is no possibility of conducting a full-scale experiment or creating a full-scale physical model of the designed object, is computer modelling of fire dynamics.

Aims and objectives. The aim of the work is to assess the temperature regime of the fire in an underground research laboratory, taking into account the influence of geometric parameters and the depth of horizontal mine opening, the characteristics of the ventilation system used, the combustible load, and the thermophysical properties of the minerals enclosing the free space.

Methods. To simulate fire dynamics, the work uses the FDS software platform, designed to carry out the corresponding calculations. The study of the influence of various factors on the results is carried out by modifying the basic model, the rationale and main tuning parameters of which are presented in the corresponding section.

Results and discussion. Based on a series of computer experiments with various tuning parameters of the model, it was found that the calculation results are significantly influenced by: the depth of the horizontal excavation, the energy consumption for heating the rock, the parameters of the ventilation system used, and also, in some cases, the dimensions of the calculation grid cell.

Conclusions. Based on the analysis of the modelling results, a number of features of the research object were identified that should be taken into account when conducting appropriate computer experiments and full-scale tests. The developed computer model can be used to assess the effectiveness of fire protection systems at the facility and study the heating of enclosures under various fire scenarios. The parameters of the temperature regime during the fire obtained from the modelling results can be used to conduct fire tests of rock samples that make up the enclosures of the underground complex structures.

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