TOWARDS A DIAMEX PROCESS FLOWSHEET USING HIGH ACTIVE CONCENTRATE (HAC)
The efficiency of MA recovery in the DIAMEX process has already been demonstrated using HAR. The next step aims at the demonstration of reprocessing from HAC as feed, in view of an industrial application. The volume reduction would reduce the size of the installation and thereby the costs of the process. The first step towards the demonstration of a DIAMEX process using HAC is the production of the genuine solutions. In ITU about 9 L HAR raffinate has been prepared, from PUREX reprocessing of 1.4 kg of MOX fuel, and characterised in order to produce HAC for the upcoming extraction tests. For this purpose, the HAR is subjected to a concentration/denitration process to obtain HAC with a final acidity compatible with the DIAMEX operating conditions, i.e. around 3 M HNO3. This process has been tested and optimised using HAR-simulate. Promising results were found for concentration factors (CF) of 6 to 8. At CF of 39 a significant co-precipitation of lanthanides occurred.
Towards a DIAMEX process using high active concentrate. Production of genuine solutions
Summary The efficiency of Minor Actinides (MA) recovery in the DIAMEX process has already been demonstrated using High Active Raffinate (HAR). The next step aims at the demonstration of reprocessing from High Active Concentrate (HAC) as feed, in view of an industrial application. The volume reduction would reduce the size of the installation to be used and thereby the costs of the process. The first step towards the demonstration of a DIAMEX process using HAC is the production of the genuine solutions. In the hot cell facility of ITU (Institute for Transuranium Elements), a HAR solution has been prepared, from small scale PUREX reprocessing of MOX fuel, and successfully subjected to a concentration/denitration process to obtain HAC. A final concentration factor (CF) of about 10 and an acidity of 4 M were reached. In the experiment a precipitate mainly composed of Sr, Zr, Mo, Sn and Ba was formed. MA precipitation was not significant (< 0.001%).
Prevention of Barite Sag in Oil-Based Drilling Fluids Using a Mixture of Barite and Ilmenite as Weighting Material
Drilling high-pressure high-temperature (HPHT) wells requires a special fluid formulation that is capable of controlling the high pressure and is stable under the high downhole temperature. Barite-weighted fluids are common for such purpose because of the good properties of barite, its low cost, and its availability. However, solids settlement is a major problem encountered with this type of fluids, especially at elevated downhole temperatures. This phenomenon is known as barite sag, and it is encountered in vertical and directional wells under static or dynamic conditions leading to serious well control issues. This study aims to evaluate the use of barite-ilmenite mixture as a weighting agent to prevent solids sag in oil-based muds at elevated temperatures. Sag test was conducted under static conditions (vertical and inclined) at 350 °F and under dynamic conditions at 120 °F to determine the optimum ilmenite concentration. Afterward, a complete evaluation of the drilling fluid was performed by monitoring density, electrical stability, rheological and viscoelastic properties, and filtration performance to study the impact of adding ilmenite on drilling fluid performance. The results of this study showed that adding ilmenite reduces sag tendency, and only 40 wt.% ilmenite (from the total weighting material) was adequate to eliminate barite sag under both static and dynamic conditions with a sag factor of around 0.51. Adding ilmenite enhanced the rheological and viscoelastic properties and the suspension of solid particles in the drilling fluid, which confirmed sag test results. Adding ilmenite slightly increased the density of the drilling fluid, with a slight decrease in the electrical stability within the acceptable range of field applications. Moreover, a minor improvement in the filtration performance of the drilling fluid and filter cake sealing properties was observed with the combined weighting agent. The findings of this study provide a practical solution to the barite sag issue in oil-based fluids using a combination of barite and ilmenite powder as a weighting agent to drill HPHT oil and gas wells safely and efficiently with such type of fluids.