The impact of oxic and thermal transient phases on corrosion of carbon steel in a cementitious environment was studied through three in situ experiments (Tournemire underground research laboratory, France). For 2 years, heated metallic samples (80°C) were placed in direct or indirect contact with two different cementitious materials: a low-pH bentonitic cement grout (BCG) and a Portland cement paste material (CEM I). Mineralogical and microstructural analyses were carried out in an attempt to identify the combined effects of pH, chemistry and microstructure properties associated with such specific cementitious media on steel corrosion mechanisms. Additionally, in situ electrical resistance corrosion sensors allowed continuous monitoring of the corrosion rates corresponding to each of the three field experiments. Post-mortem characterization indicated that metallic samples embedded in low-pH BCG were heavily damaged and exhibited high corrosion rates. Conversely, steel samples in contact with a highly alkaline CEM I environment appeared to be much less impacted by corrosion processes and revealed extremely low corrosion rate values. A comparison between these field experiments observations and results previously obtained through complementary laboratory mock-up tests finally enabled the evaluation of the impact that variations in geometrical/design aspect existing between in situ and laboratory tests can induce on material degradation.
Models of the severe-accident SAFR module used to calculate the cladding melt relocation along the fuel pin surface during its melting are presented in relation to severe accidents in fast-neutron reactors cooled by liquid metal. The choice of the basic system of equations and closing relations is presented. The models are validated based on experiments on melting and flow of cladding simulator melts. The error of calculating the cladding mass loss due to its melting and flowing along the fuel pin surface is estimated.
The experimental results on the structure of the two-phase “liquid metal-gas” medium in vertical channels depending on the gas flow rate and channel diameter are presented. Lead-bismuth melt at a temperature of 160°C was used as a liquid medium, and argon was used as a gas phase. Data were obtained on the shape of gas bubbles, temporary changes in the gas content in channels, histograms of gas content distribution, and features of the slug flow of gas in the metal melt.
Приводится обзор подходов к моделированию фильтрации подземных вод в трещиновато-пористых средах, обсуждаются их достоинства и недостатки. Описывается DFM-модель, реализованная в программном комплексе GeRa. Данный подход позволяет явно учитывать геометрию трещин и водообмен между трещинами и пористой матрицей. Предлагается использование многоточечной аппроксимации потоков на трещине методом конечных объемов на основе О-схемы. Демонстрируется применение реализованной численной схемы к решению практической задачи оценки водопритока к подземным выработкам в трещиноватом горном массиве.
