Pellets of the synthetic zeolite X were loaded with the radioisotopes60Co,63Ni and65Zn. The pellets were then calcined. A secondary ion-exchange step introduced a large cation, barium, into the zeolites with a view to blocking the release of the radioisotopes under leaching conditions. Leaching was carried out over 84 days with synthetic sea and ground waters as well as deionised water. Leach tests were evaluated in terms of cumulative fraction of isotopes released and as diffusion coefficients derived from leaching profiles. Cobalt containing samples were cement encapsulated and further leach studies carried out. Some minor reduction in isotopes release was observed in the presence of barium but this was not consistent.
Authors:K. Kim, J. Bae, B. Park, D. Ahn, S. Paek, S. Kwon, J. Shim, S. Kim, H. Lee, E. Kim, and I. Hwang
A pyrochemical processing has become one of the potential technologies for a future nuclear fuel cycle. An integrated multi-physics
simulation and electrotransport model of a molten-salt electrolytic process are proposed and discussed with respect to the
recovery of pure uranium when using thermochemical data. This study has been performed to provide information for diffusion
boundary layers between the molten salt (KCl-LiCl) and electrode. The diffusion-controlled electrochemical model demonstrate
a prediction of the electrotransport behaviors of LWR spent fuel as a function of the time up to the corresponding electrotransport
satisfying a given applied current based on a galvanostatic electrolysis.
The importance of the thermal behaviour of glasses is illustrated. Some procedural characteristics for glass preparation upon quenching are discussed to distinguish the positive effects of increasing cooling rate. The basic thermodynamic quantities, kinetic data and procedural parameters are listed. The glass-transformation interval is treated in detail to demonstrate the temperature-dependences of heat capacity, enthalpy an Gibbs energy for as-quenched and annealed glasses, exemplifying processes of thermally stimulated reordering. Particular attention is paid to DTA measurements, which are of use for the determination of characteristic temperatures and to for the distinction of possible types of processes which occur upon reheating. Most common cases are illustrated by a series of hypothetical ΔH vs. T and ΔTdtavs. T plots. Different glass formation coefficients based on the onset temperatures are discussed to confirm the general knowledge that their maxima match with concentration regions close to that of invariant melting of the system.
Properties of limestone related to SO2/SO3 reactivity were investigated. Limestone calcined under different conditions (temperature, time and with/without additives)
yield calcines of distinctly different physical structures. The amount of pores and the size of the pores formed during calcination
The main purpose of the present work was to gain a better understanding and more reliable explanation of the temperature regime
for gas desulphurization using Ca-based sorbents in atmospheric fluidized-bed combustors.
Pore size, surface area and pore volume of each calcine were determined by mercury porosimetry and BET methods. At higher
calcination temperature and during longer time, sintering became significant and the obtained calcine had a smaller internal
surface area and thereby the average pore radius increased. The additives such as NaCl also accelerated sintering thus increasing
the pore size. The measurements of porosity were supplemented by scanning electron microscopic observations employed for qualitative
description of the pore structure. SEM micrographs are presented.
Authors:F. Mezahi, H. Oudadesse, A. Harabi, A. Lucas-Girot, Y. Le Gal, H. Chaair, and G. Cathelineau
The dissolution kinetic and structural behaviour of natural hydroxyapatite (N-HA) and synthetic hydroxyapatite (S-HA) was
studied vs. sintering temperature and using ‘in vitro’ experiments. Obtained results highlight the chemical stability of N-HA. Any structural
modification was observed until 1200°C. In the fact S-HA undergoes some modifications. XRD diagrams show the tricalcium phosphate
(TCP) phase formation between 800 and 1100°C and tetracalcium phosphate (TetCP) phase formation at 1200°C. The ‘in vitro’
assay shows that the dissolution was occurred more in N-HA than in S-HA. The formed TCP activated the dissolution kinetic
and then the precipitation phenomena when a continuous dissolution of TetCP leaded to slow down the kinetic precipitation.
Solid-gas phase transition processes of some triazines were studied from kinetic and thermodynamic viewpoint. DSC measurements
and Clausius-Clapeyron equation were used to determine enthalpy values related to these processes. Model-fitting methods (based
on Arrhenius, Šatava equations and Šestk-Berggren equations) and model-free methods (based on Ozawa-Flynn-Wall and Kissinger
equations) allow to hypothesis R2 mechanism. An attempt to determine the activation parameters (ΔH#, ΔG#, ΔS#) related to these processes was carried out. Accordance between the activation enthalpy values with those of activation energy
obtained by means of kinetic methods and with the experimental (DSC) and calculated (Clausius-Clapeyron) enthalpy values was