Elastic plastic finite element analysis of a BWR feed water distributor exposed to an extreme pressure load


Elastic plastic finite element analysis of a BWR feed water distributor exposed to an extreme pressure load

Altstadt, E.; Ohlmeyer, H.; Otremba, F.; Weiß, F.-P.

During a hypothetical break of a BWR feed water line, the feed water distributor (FWD) inside the RPV is subjected to a high pressure load for a short time (10 ms). Because of the sudden coolant release from the inner volume of the FWD there is a pressure difference between the inner and outer surface. It is conservatively assumed that the pressure difference nearly can reach the operating pressure for a few milliseconds. The distributor box and the ring line of the feed water distributor are modelled with shell and volume elements capable of being used for large strain analyses with elastic-plastic material behaviour. It is demonstrated by non-linear static calculations (without consideration of the inertia of the material) that a buckling instability occurs at about 60% and 80% of the maximum pressure load. The arc-length method is used for the numerical solution to overcome these points of instability. To evaluate the influence of the dynamics of the process a non-linear transient analysis is done showing that the maximum strain occurs with a time delay to the pressure peak. The maximum plastic strain differs only insignificantly between static and transient solution. Inspite of the large strains the mechanical integrity is maintained during the hypothetical event.

Keywords: BWR; Finite element analysis; Large strain; Plasticity; Transient analysis

  • Lecture (Conference)
    15-th International Conference on Structural Mechanics in Nuclear Technology (SMIRT-15), Seoul, Korea, August 15-20 1999, Proceedings Vol. VII pp. 177-184
  • Contribution to proceedings
    15-th International Conference on Structural Mechanics in Nuclear Technology (SMIRT-15), Seoul, Korea, August 15-20 1999, Proceedings Vol. VII pp. 177-184

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Publ.-Id: 1505