The AMoRE (Advanced Mo based Rare process Experiment) collaboration is searching for neutrinoless double beta decay of 100Mo using low radioactive CaMoO4 scintillation crystals. But the raw materials for growth of CaMoO4 crystal are contaminated by various radioactive contaminants such as uranium and thorium. Furthermore, there are no commercially available calcium and molybdenum compounds which have required level of radioactive contamination. In order to achieve required levels of purity, calcium and molybdenum salts should be purified. In this research we mainly focused on purification of calcium carbonate from radionuclides and chemical contaminants. A combination of ion exchange chromatography with subsequent precipitation from aqueous solution was used. Our current purification method based on wet chemical process, therefore aqueous solution of calcium carbonate (CaCO3) powder is prepared in 65% nitric acid. Ion exchanger based on granular manganese dioxide (MDM = MnO2 granules) sorbent was then used for selective ion exchange of contaminants in the initial stage of purification while barium sulphate and lead sulphate are used for direct sorption method. Precipitate of calcium carbonate from this solution was obtained by 25% aqueous ammonia (NH4OH) and ammonium carbonate [(NH4)2CO3]. Samples were collected at each purification step and analyzed for ICP-MS measurements. From ICP- MS results decontamination factor for each contaminant was then calculated.
Deep purification was obtained from impurities of iron, strontium, barium (radium), uranium and thorium occurred using the ion exchange of MnO2 resin as compared to BaSO4 and PbSO4.
Thesis Advisor: Prof. Hongjoo Kim