Experience gained from using computation codes for modeling fires at nuclear-powered transport facilities
Keywords:
CFD codes, safety of transport nuclear power facilities, fire accidents at nuclear facilitiesAbstract
The possibility of using computational fluid dynamics (CFD) codes for modeling fires at nuclear facilities is considered. The main objective of the study is to elaborate an algorithm for constructing a model on the basis of CFD codes and to find the optimal parameters of the used models to achieve the best agreement with experimental data. Calculations of fires by CFD codes for two problems are presented. In the first case, a room with a distributed combustible load is described in terms of standard elements like a bookcase, table etc. The main feature of modeling such a case is to select and apply an adequate engineering model representing the pyrolysis of woodwork. The Eddy Dissipation Model, which is often used in engineering calculations, was applied for directly modeling the burning process. The results of calculations are presented by way of comparison with experimental data for typical measurement points. The presented analysis of the results shows that good agreement has been reached between the experimental and calculated data. In the second case, the burning of a localized spill of combustible liquid within the volume of a production premise is considered. One of the major differences of the second case from the first one is that the fire in it terminated once the oxygen in the premise has burnt out. To this end, the original burning model was modified by including a heat flux feedback as fuel vapor enters into the volume. Some other modifications were also introduced into the model, namely, sophisticating the burning model by applying the flamelets approach, taking into account the turbulence anisotropy based on using appropriate second-order models, and calibrating the model parameters. A comparison of the calculated and experimental data shows that acceptable agreement between them has been reached
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