Trace metal assay of thorium based fuels by ICP-AES after microwave dissolution

Full text: Estimation of impurities in nuclear fuel materials like Th/U/Pu is essential prior to their introduction into a reactor. Trace metallic constituents affect the neutron economy, fuel density and fuel fabrication processes. As thorium is an important fuel material for future reactors, its analysis for impurities is also essential. The fuel for AHWR critical facility is (Th,Pu)O2 and (Th-U)O2 consisting of approximately 3-4% of PuO2 and 233UO2. However, assay of metallic impurities in such fuel requires quantitative separation of the major matrix from the analytes as Th, U, Pu have rich emission spectrum. ICP-AES is the most suitable technique for trace metal determination because of its simplicity and simultaneous multielement determination capability coupled with adequate sensitivity, analytical range and good precision than other techniques. The present paper describes the analysis of thorium-based fuels for trace metal content after their chemical separation from the major matrix. As thorium has only one oxidation state (IV), its dissolution under normal conditions is very difficult and time consuming. Therefore, a new method under microwave was used for dissolution. Few samples of AHWR type fuel consisting of thorium and 2.5% UO2 were dissolved by microwave dissolution technique and analysed for trace impurities by ICP-AES. The results obtained were validated by analyzing ILCE Thoria samples, which have also undergone same process of dissolution and separation