Thermal transient finite element computation of a mixing Tee by utilizing CFD results

Thermal distribution and fluctuation in any piping component due to turbulent mixing of flows with different temperatures vary greatly. Usually, computational fluid dynamics (CFD) tools are used for estimation of flows in piping components. Fatigue that results from fluctuating thermal mass flow across the components can be computed by coupling the CFD results with structural mechanics based finite element (FE) results. However, this procedure is laborious and computationally very expensive. A fluid temperature function has been developed in this paper as a function of internal wall coordinates and time by interpolating experimental or CFD results. Bicubic interpolation function has been used for accurate interpolation. Finally, a thermal transient FE analysis for an actual Tee from a nuclear power plant (NPP) was performed by using the developed fluid temperature function and interpolated CFD results

Comparative analysis of deterministic and probabilistic fracture mechanical assessment tools

Uncertainties in material properties, manufacturing processes, loading conditions and damage mechanisms complicate the quantification of structural reliability. Probabilistic structure mechanical computing codes serve as tools for assessing leakand break probabilities of nuclear piping components. Probabilistic fracture mechanical tools were compared in different benchmark activities, usually revealing minor, but systematic discrepancies between results of different codes. In this joint paper, probabilistic fracture mechanical codes are compared. Crack initiation, crack growth and the influence of in-service inspections are analyzed. Example cases for stress corrosion cracking and fatigue in LWR conditions are analyzed. The evolution of annual failure probabilities during simulated operation time is investigated, in order to identify the reasons for differences in the results of different codes. The comparison of the tools is used for further improvements of the codes applied by the partners