D38 CFD modeling and validation of a GEN-IV reactor mockup under seismic load

This document reports on the modelling and simulation of the mockup of ALFRED, a GEN-IV reactor, under seismic load. The mockup has been built and operated, in water, by VKI in collaboration with CRS4 and ANN. It is inspired by the current ALFRED design and it is focused on the representation of the main components present in the upper plenum, still maintaining an open connection with the lower bulk. The experimental mockup is shortly presented. The geometry of its numerical counterpart is described. The numerical modeling was described in the deliverable D13“Sloshing CFD modeling and validation with SHAKESPEARE first experimental campaign” and required some few adaptations to this new application, which are explained here. The simulation results are shown and then compared with the experimental ones. First, the technical feasibility of the numerical mockup is ascertained. Second, the comparison is done on artificial harmonic forcing. Then, simulations are performed with existing seismic loads taken from the last 20 years major earthquake in Italy in 2016, applying the necessary scaling. The methodology is reused to investigate on the mockup seismic signals of higher amplitude, from Romania in 1977 and Turkey in 2023. The wave amplitude is measured as well as the force induced on the vessel and the DHR components. We then concentrate on the simulation of the 2011 Japan earthquake causing the tsunami that was the initial trigger of the Fukushima incident. We observe that the highest intensities of the forces applied to the vessel and the components arise from the seismic high frequency component. It is therefore compulsory to first and foremost strongly filter this component by means of carefully designed damping systems. With a numerical low pass filter at 1 Hz which mimics a possible damping system, the peak force on the mock-up vessel is reduced by a factor of 20. Nevertheless, the effect of sloshing can be observed but remains much lower than the direct effect of the seismic acceleration.

@TechReport{MP24d,
  author       = {Moreau, V. and Profir, M.},
  title        = {D38 CFD modeling and validation of a GEN-IV reactor mockup under seismic load},
  institution  = {CRS4},
  month        = {august},
  year         = {2024},
  type         = {Deliverable of the  EURATOM PASCAL project No 945341},
  keywords     = {PASCAL, sloshing, CFD, simulation},
  url          = {https://publications.crs4.it/pubdocs/2024/MP24d},
}