To assess the safety of disposal of radioactive waste material in concrete, curing conditions and time of leaching radionuclide137Cs have been studied. Leaching tests in concrete were carried out in accordance with a method recommended by IAEA1.
This paper presents results from studies made to determine the leachability of137Cs from immobilized evaporator sludge from a Pressurized Water Reactor with cement. Leaching of137Cs from cement matrix using three methods based on theoretical equations has been developed. These were: Method I, diffusion equation derived for a plane source model, Method II, rate equation for diffusion coupled with a first-order reaction. The leaching data were also analyzed by an empirical method employing a polynomial equation —Method III. Results presented in this paper are examples of data obtained in a cement testing project which will influence the design of a future radioactive waste storage center.
The base mix refractory concrete is corundum-based, containing corundum as refractory aggregate and CAC as hydraulic binder, with a spinel as an additive. The authors investigated the dehydration reactions which occur from the moment when water is added (at the beginning of components mixing), to the moment when installed refractory concrete lining is put into the service. Sintering process kinetic of low-cement content refractory concrete was investigated by means of differential thermal analysis at four different heating rates (5, 10, 20, and 30 °C/min). Thus, temperature was increased from 20 to 1100 °C. It was noticed that first dehydration step occurs at lower temperatures, indicating at a desorption of physically adsorbed and interlayer water molecules. Second dehydration step, at higher temperatures is due to dehydroxylation of the lattices and decomposition of the interlayer anions.
The objective of this work is to investigate the impact of the geometric dimensions of parabolic trough collector (PTC) in the optical, energetic and exergetic efficiency. The module of the commercial LS-3 PTC is examined with SOLIDWORKS FLOW SIMULATION in steady-state conditions. Various combinations of reflector widths and receiver diameters are tested. The optical and the thermal performance, as well as the exergetic performance are calculated for all the examined configurations. According to the final results, higher widths demands higher receiver diameter for optimum performance. For inlet temperature equal to 200 °C, the optimum design was find to be 3000 mm width with 42.5 mm receiver diameter, with the focal length to be 1840 mm (this is kept constant in all the cases). The results of this work and the presented methodology can be used as guidelines for the design of optimum PTC in the future.
We examined the concentrations of vitamin E (vit E), sulphydryl groups (-SH), total protein and protein electrophoretic profiles in the hepatopancreas, the gills and muscle of three freshwater crayfish species: Noble crayfish (Astacus astacus), stone crayfish (Austropotamobius torrentium) and spiny cheek crayfish (Orconectes limosus). Vit E concentration in the hepatopancreas of O. limosus was lower compared to A. astacus, while in the gills of O. limosus it was lower compared to both A. astacus and A. torrentium. The concentration of -SH groups was lower in the hepatopancreas of A. astacus compared to A. torrentium and O. limosus. In the gills of A. astacus and A. torrentium the concentration of -SH groups was higher compared to O. limosus. Protein concentration was higher in the hepatopancreas of A. torrentium compared to A. astacus and O. limosus. A lower protein concentration in muscle of A. torrentium was found compared to O. limosus and A. astacus. Electrophoretic analysis of proteins indicated species and tissue specifities between investigated crayfish species. Our results represent the first study of its kind and provide the basis for future studies that will consider our reported parameters as potential biomarkers for biomonitoring of basic environmental conditions and some anthropogenic impacts.