Kiyofumi Moriyama

Minimum film-boiling quench temperature increase by CuO porous-microstructure coating

Increase in the minimum film-boiling quench temperature, TMFB, is achieved with microstructured CuO particles, and attributed to local cooling (fin effect) by the microstructure causing liquid–solid contact. A periodic structure is obtained using electrochemical deposition of 1 μm diameter particles on brass sphere diameter 15 mm forming unit-cell porous cones of average height L = 100 μm and base diameter D = 20 μm. Fin analysis predicts the cone tip cooling to the homogeneous nucleation temperature of water (∼330 °C), while the base temperature is at 600 °C. This causes liquid–solid contact during quenching, and analysis suggests the fin effective thermal conductivity ⟨k⟩ and fin characteristic length L2/D are key to this liquid–solid contact that influences TMFB.

Simulation of melt jet breakup experiments by JASMINE with an empirical correlation for melt particle size distribution

ABSTRACT We modified JASMINE code, a fuel–coolant interaction simulation code developed at Japan Atomic Energy Agency (JAEA), to extend the applicability for ex-vessel melt coolability assessment. The modification included addition of a melt particle size distribution model based on an empirical correlation and a simple non-local radiation heat transfer model, improvement in the treatment of melt particle generation, and re-agglomeration of settled particles. The modified code was tested by simulating melt jet breakup experiments, namely selected cases of ALPHA/GPM series with alumina–zirconia mixture and steel melt by JAEA, and FARO experiments with urania–zirconia mixture by Joint Research Center Ispra. Simulation results showed that the code reproduces the experimental results well for the cases with a deep subcooled water pool where the melt breaks up completely. On the other hand, significant underestimation of heat removal from the melt and overestimation of agglomeration of settled melt was encountered for conditions with a shallow or saturation temperature water pool. The melt agglomeration behavior in the simulation was sensitive to model parameters on the agglomeration criterion and heat transfer depending on conditions.