Development of methodology for determining the isotopic composition of boron in powder and solid nuclear materials using secondary ion mass spectrometer

Abstract

A method has been developed to determine the isotopic composition of boron (10B/11B) in powder and solid nuclear materials using secondary ion mass spectrometry (SIMS). Isotopic composition of boron in standard sample matrices such as H3BO3, B2O3, B4C (powder) and TiB2 (solid alloy) were measured by the method and compared with the isotopic composition determined from thermal ionization mass spectrometer. Powder samples were ultrasonicated in Milli-Q water and the solutions/slurry obtained were deposited on cleaned silicon wafers, dried under halogen lamp and analysed by SIMS whereas solid alloy sample TiB2 was directly analysed after mechanical polishing and cleaning. Detailed analyses have been carried out using both oxygen and cesium primary ion beams under different analysis conditions. Various elemental and molecular secondary ions were monitored for determining the isotopic composition of boron present in the samples. Standard of boron, NIST-SRM-951 sample was utilized for determining the instrument bias correction factor for different primary beam analysis conditions. The determined instrument bias correction factor was then utilized to measure the isotopic composition of boron in other samples. Surface distribution analysis was also carried out to determine the isotopic distribution of boron deposited on Si wafers. Determination of boron isotopic ratio in refractory nuclear materials (B4C, TiB2) using this method requires minimal sample preparation and avoids commonly used complex dissolution process.