V.V. Gusarov

Experimental studies of oxidic molten corium-vessel steel interaction

The experimental results of molten corium-steel specimen interaction with molten corium on the Rasplav-2 test facility are presented. In the experiments, cooled vessel steel specimens positioned on the molten pool bottom and uncooled ones lowered into the molten pool were tested. Interaction processes were studied for different corium compositions, melt superheating and in alternative (inert and air) overlying atmosphere. Hypotheses were put forward explaining the observed phenomena and interaction mechanisms. The studies presented in the paper were aimed at the detection of different corium-steel interaction mechanisms. Therefore certain identified phenomena are more typical of the ex-vessel localization conditions than of the in-vessel corium retention. Primarily, this can be referred to the phenomena of low-temperature molten corium-vessel steel interaction in oxidizing atmosphere.

Severe accident management concept of the VVER-1000 and the justification of corium retention in a crucible-type core catcher

First ex-vessel core catcher has been applied to the practical design of NPPs with VVER-1000 reactors built in China (Tyanvan) and India (Kudankulam) for severe accident management (SAM) and mitigation of SA consequences. The paper presents the concept and basic design of this crucible-type core catcher as well as an evaluation of its efficiency. The important role of oxidic sacrificial material is discussed. Insight into the behaviour of the molten pool, which forms in the catcher after core relocation from the reactor vessel, is provided. It is shown that heat loads on the water-cooled vessel walls are kept within acceptable limits and that the necessary margins for departure from nucleate boiling (DNB) and of vessel failure caused by thermo-mechanical stress are satisfactorily provided for.

Magnetic properties of synthetic Ni3Si2O5(OH)4 nanotubes

The present study focuses on the magnetic properties of the nanotubular Ni3 Si2 O5 (OH)4 pecoraite, the structural analogue of chrysotile, obtained by hydrothermal synthesis. The cell parameters of the material, determined by X-ray diffraction, are , , and . The element analysis revealed the decrease of the Ni:Si ratio after hydrothermal treatment. The synthesized nanotubes have bigger outer and inner diameters in comparison to chrysotile. Using a vibration sample magnetometer, we determined the temperature of the ferromagnetic transition (23.7 K), of the ion in pecoraite and the blocking temperature (18 K).

The thermal behavior of mixed-layer Aurivillius phase Bi13Fe5Ti6O39

The mixed-layer perovskite-like compound Bi13Fe5Ti6O39 with Aurivillius phase structure Bim+1Fem−3Ti3O3m+3 (mxa0=xa05.5) was synthesized by the solid-state reactions method. The thermal behavior of Bi13Fe5Ti6O39 in the range from 2 to 1450xa0K was studied by the differential scanning calorimetry, the impedance spectroscopy and the analysis of temperature dependences of the permittivity and magnetization. The temperature of decomposition and the temperatures of phase transitions were determined. It was shown that Bi13Fe5Ti6O39 combines the ferroelectricity with the magnetic ordering below the temperature 173xa0±xa04xa0K. The data obtained in thermal measurements showed that the thermal behavior of mixed-layer compound Bi13Fe5Ti6O39 and Aurivillius phases Bim+1Fem−3Ti3O3m+3 with an integer m was analogous. The mechanism of thermal degradation Bi13Fe5Ti6O39 was described as sequential peritectic decomposition into compounds of the same homologous series having a smaller m (mxa0≤xa05.5). Bi13Fe5Ti6O39 has a semiconductor-like type of conductivity and undergoes high- and low-temperature phase transitions.

Ternary eutectics in the systems FeO-UO2-ZrO2 and Fe2O3-U3O8-ZrO2

The systems FeO-UO2-ZrO2 (in inert atmosphere) and Fe2O3-U3O8-ZrO2 (in air) were studied. For the FeO-UO2-ZrO2 system, the eutectic temperature was found to be 1310°C, with the following component concentrations (mol %): 91.8 FeO, 3.8 UO2, and 4.4 ZrO2. For the Fe2O3-U3O8-ZrO2 system, the eutectic temperature was found to be 1323°C, with the following component concentrations (mol %): 67.4 FeO1.5, 30.5 UO2.67, and 2.1 ZrO2. The solubility limits of iron oxides in the phases based on UO2(ZrO2,FeO) and UO2.67(ZrO2,FeO1.5) were determined.