An approach to coupled thermal hydraulics and structural mechanics problems for the MEGAPIE spallation source target

Abstract

SUMMARYThis paper describes some novel heat transfer and stress analysis problems that arose in the context of demonstrating the cooling principle of a liquid-metal neutron spallation source target. The design studies using computational fluid dynamics (CFD) resulted in an optimum flow configuration being defined for the coolant circulation. Simultaneously, stresses in the structural components were examined using finite element method (FEM) techniques. Central to the coupled CFD/FEM analysis strategy was the construction of an interface program, which enabled different specialist groups to carry out the thermal hydraulics and structural mechanics analyses using different commercial or in-house software packages within a common project, and with fully consistent model data. For the studies reported here, the commercial CFD code CFX-4 and the commercial structural analysis codes ABAQUS and ANSYS have been employed. Results for steady-state operation of the target show that the critical lower target components are adequately cooled, and that stresses and displacements are well within tolerances. Transient analysis of a beamtrip and power-up event is also described, showing that no stress crisis occurs.

Computational Fluid Dynamic Studies of the MEGAPIE Spallation Source Target and Safety Vessel

“…Analysis of the accident sequence requires the coupled application of a CFD tool-in our case CFX-4 12) -and a structural analysis code-in this case ABAQUS 16) -with transient data being interfaced between them. 4) The lower target schematic given in Fig. 15(a) illustrates the accident sequence.…”

Computational Fluid Dynamic Studies of the MEGAPIE Spallation Source Target and Safety Vessel

“…The temperature contours clearly reflect the elliptical form of the beam footprint. Again, the associated stress analysis 4) revealed that, despite the strong temperature gradient in the centre of the window, the high stress concentrations actually occur in the outer section, near the flow guide attachment points, where the material is thicker and curvatures are high. The calculation also revealed that the internal D 2 O pressure (corresponding to a 6 bar overpressure) has a nontrivial effect on the stress distribution.…”

“…A Computational Fluid Dynamic Studies of the MEGAPIE Spallation Source Target and Safety Vessel transient, conjugate heat transfer calculation was performed, starting from a normal operating mode, with the beam at full power. Data files 4) containing the information needed to compute the stresses were written at specified time intervals during the run (50 ms over most of the transient, but 5 ms around the time of maximum stress). This procedure also allowed checking of the time-step dependence of the results.…”

“…This required the simultaneous application of advanced computational fluid dynamic (CFD) tools and structural analysis (or finite element method, FEM) programs, and the existence of an effective data interface between them. 4) This coupled CFD/FEM approach became a key component of the R&D support to the construction of the MEGAPIE target, the various tasks being carried out collaboratively by different groups using different numerical tools. Simultaneously, special-effect experiments, using both simulant and actual materials, were performed [5][6][7] in order to provide effective validation data for the numerical simulations.…”