Thermal simulation of sodium heated once through steam generator for a fast reactor

In typical sodium cooled fast reactors, steam generators (SG) transports heat from hot liquid sodium to high pressure feed water. Feed water gets heated and converted to superheated steam and is used to roll the turbine. In SG, tubes are in triangular pitch pattern and shell in cylindrical shape, making some non-uniform gap at periphery allowing sodium to by-pass resulting radial thermal difference. Estimation of this thermal difference is very important in order to design a provision to accommodate the maximum differential thermal expansion among tubes and shell and to resist maximum thermal cycles faced by SG in its design life. A detailed three-dimensional thermal analysis of a sector model of SG with 30 m long tube is performed by combining a commercial Computational Fluid Dynamic code with in-house one-dimensional code DESOPT. The analysis is also validated with in-house experimental test facility results. From the analysis, the radial and axial temperature distributions and the differential temperature between tubes and shell are estimated for commercial fast breeder reactors SG for normal operation and typical plugged tube conditions and the results are highlighted in this paper. The results would form input for the estimation of differential thermal expansion of shell and tubes of SG and design of tube-sheets.