Speaker
Description
Design of the Water Cooled Ceramic Breeder (WCCB) blanket includes beryllium multiplier layers. At elevated temperature, beryllium reacts with steam in an exothermic reaction producing beryllium oxide and hydrogen. Such situation may occur in WCCB in case of the rupture of one of the cooling pipes in the blanket module. This process occurs locally in a complex 3D geometry of the blanket containing several different granular levels and a network of cooling pipes and structural supports. The process is also inherently unsteady since reaction rate depends on concentration of steam and pure beryllium which changes in time. In order to perform detailed analysis of the process the model of the reacting flow through porous media was developed and introduce into 3D CFD code. In this model granular beds are introduced as porous solids simplifying the model geometry, and reducing typical mesh size to manageable amount of tens of millions of elements. Reaction rate between solid beryllium and steam is obtained from experimental results, and depends on temperature and concentration of the reactants. Differential equation for beryllium oxide fraction is introduced, allowing obtaining distributions of beryllium oxide in space and time. Multicomponent flow consisting of a homogenous mixture of steam and hydrogen is considered flowing through the porous solid with variable properties. Sink and source terms for steam and hydrogen fractions are determined by local beryllium oxide mass fraction source according to molar ratios of beryllium steam reaction. Conjugated heat transfer approach is applied to calculate heat transfer in support structures as well as coolant flow, simultaneously with the porous medium steam flow in a blanket’s granular beds. The model is validated using experimental data on beryllium steam reaction for granular bed samples.
| Eligible for student paper award? | No |
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