Application of RCC-MR for the structural design of tube sheet of intermediate heat exchanger for a sodium cooled fast reactor

• The structural mechanics behavior of tube sheets has been studied in detailed by FEM analysis software CAST3M.
• Practical guidelines are provided to accurately derive the primary stress intensities particularly at the interface.
• Linearization of stress components along the radial directions and the effect of filet radius at the interfaces have been covered in detailed.
• Estimation of creep–fatigue damage as per RCC-MR.
• These investigations thus help to optimize the design of IHX tube sheets with high confidence.

The structural mechanics behavior of tube sheets of a sodium to sodium heat exchanger for a fast reactor, with circular tube holes pattern, less addressed subject in the literature, is investigated in detail. The tube sheet design rules recommended in the French design code RCC-MR-2007 and the associated solid mechanics basis are explained. A finite element analysis of tube sheets of intermediate heat exchanger of a typical 500 MWe pool type fast reactor is presented to study the effects of some specific parameters viz., (i) small solid rim portion with connecting shell and (ii) grooves on rim area. For the analysis, the distribution of holes on the last row is assumed to be symmetric and axial stiffening of tubes on tube sheet is included toward realistic estimation of stresses in the tube sheets. The effects are studied on the primary and secondary stresses induced along the interface between solid to perforated region. The aspects covered include linearization of radial and circumferential stress components, thereby deriving primary membrane and bending stress intensities along the radial directions with particular focus at the interfaces between solid portions and perforated portions including the effect of filet radius at the junction of tube sheet and shell. These investigations thus help to optimize the design of IHX tube sheets with high confidence. The analysis has been carried out by CAST3M, a structure analysis software granted by CEA, France.