The high abundances of the high field‐strength elements in ilmenite and rutile make these minerals particularly suitable for hafnium isotopic investigations. We present a technique for separating Hf by ion exchange chemistry from high‐TiO2 (> 40% m/m) minerals to achieve precise Hf isotopic composition analyses by MC (multiple collector)‐ICP‐MS. Following digestion and conversion to chlorides, the first elution column is used to separate iron and the rare earth elements, the second column is designed to separate most of the titanium from Hf, an evaporation step using HClO4 is then performed to remove any trace of HF in preparation for the third column, which is needed to eliminate any remaining trace of titanium. The modified chemistry helped to improve the yields from < 10 to > 78% as well as the analytical precision of the processed samples (e.g., sample 2033‐A1, 176Hf/177Hf = 0.282251 ± 25 before vs. 0.282225 ± 6 after). The technique was tested on a case study in which the Hf isotopic ratios of ilmenite and rutile (analysed prior to the chemistry improvement) were determined and permitted to evaluate that the origin of rutile‐bearing ilmenite deposits is from the same or similar magma than their, respectively, associated Proterozoic anorthosite massifs (Saint‐Urbain and Lac Allard) of the Grenville Province in Québec, Canada.
The dismantling of the BR3-PWR reactor leads to the production of large masses of contaminated metallic pieces, including structural materials, primary pipings, tanks and heat exchangers. One of the main objectives is to demonstrate that we can minimise the volume of radioactive waste in an economical way, by the use of alternative waste routes, such as recycling of material in the nuclear world, free release of material in the conventional industry after melting or free release of material after thorough decontamination. The SCK•CEN launched a decontamination program with the aim to free release as much of the dismantled metallic material as possible.
The selected chemical decontamination process, so-called MEDOC® (MEtal Decontamination by Oxidation with Cerium), is based on the use of cerium IV as strong oxidant in sulphuric acid with continuous regeneration using ozone. An industrial installation has been designed and constructed in close collaboration with Framatome-France. This installation started to operate in September 1999 for the treatment of the metallic pieces arising from the dismantling of the BR3 reactor. Since the installation starts up, 21 tons of contaminated material has been treated batchwise with success.
Up to now, MEDOC® has been accomplished as a batch process in which the decontamination reactor is loaded with a basket containing the contaminated material. The SCK•CEN is now considering the possibility of using the MEDOC plant to decontaminate large components before cutting them, such as the BR3 -steam generator and the pressurizer. The decontamination solution will be circulated between the MEDOC plant and the steam generator during the consecutive decontamination cycles. Each cycle will comprises a decontamination step followed by a regeneration step. For the steam generator, 30 cycles are estimated to be needed to reach the free release level after melting. The decontamination studies of large components are ongoing and take into account the technical aspects, the radiological and classical safety aspects, as well as financial aspects.
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