Numerical simulations of passive scalar transfer near a heated wall at high Prandtl and Schmidt numbers were carried out. In these flows, the scale of the smallest structures of the turbulent scalar field are smaller for a factor equal to the square root of the Prandtl number than the dimensions of the smallest turbulent eddies. These analyses have shown the negligible influence of the smallest turbulent scales of the passive scalar field on the bulk passive scalar transfer and on the lower statistics of the turbulent passive scalar field.

COBISS.SI-ID: 20806695

In some hypothetical severe accident scenarios, it is assumed that the reactor core melts and spills into the reactor cavity. The contact of the core melt with water could trigger a steam explosion. We have performed the first analysis of a kind, with which we estimated the expected pressure loads on the cavity structures during an ex-vessel steam explosion in a typical pressurized water reactor, and also estimated the vulnerability of cavity structures. A vulnerability analysis of reinforced concrete reactor cavity walls to different characteristic steam explosions was also performed.

COBISS.SI-ID: 19921703

A three-dimensional two-fluid convective boiling model for pressurized water reactors was developed. The boiling model was validated on low-pressure experiments (3 bar) with refrigerant R-113 and on high-pressure experiments with water (30 to 150 bar). The model was used to simulate boiling flow in the real flow channel between fuel rods of the reactor core, where the effect of mixing vanes was also taken into account. The simulations enabled the analysis of the evolution of the two-phase flow structure in the flow channel and the estimation of the heat loads on the fuel rods.

COBISS.SI-ID: 21322279

A multiscale model that describes the behaviour of a polycrystalline material, composed of randomly sized, shaped and oriented grains, was used for a study of microstructurally short cracks. We mainly observed crack parameters that are related to crack growth and direction change. Observed configurations included straight cracks contained within a single grain and cracks, kinked on the boundary between two grains. The observed parameters significantly depend on the random crystallographic orientations of grains in the crack vicinity.

COBISS.SI-ID: 20960807

A method for assessment and decreasing of vulnerability of strategic facilities was developed. The method integrates physical modeling of explosions, analysis of materials strength, phenomenological models of the causes of damage, injuries to human beings and probabilistic safety assessment with qualitative and quantitative assessment of unwanted scenarios. The results indicate how far from strategic objects the physical barriers should be placed in order that the damage of explosions does not destroy the facility.

COBISS.SI-ID: 20286247