Determination of boron contained in a cementitous matrix used for the transport or the storage of radioactive waste

Abstract

Neutron shielding materials, containing boron as the neutron absorbing element, are used as a biological protection in nuclear materials storage and transportation casks. In the present work, boron in the form of colemanite powder (Ca2B6O11·5H2O), was incorporated in a cementitious matrix. Localized quantification of boron is required to confirm that a homogeneous distribution in the matrix has been achieved. The elemental analysis of a neutron-shielding cement matrix containing boron in minor quantities (less than 1 to 2 wt% of boron) was made.The elemental analysis of mineral materials requires dissolution in most cases. The first challenge encountered was the determination of a dissolution protocol that leads to total dissolution of materials, namely cement, colemanite and other minerals, without losing volatile compounds such as borates. The next challenge was the elemental analysis itself. Numerous elements are present in the obtained solutions and could interfere with boron determination. Different boron titration techniques are reviewed out in order to choose the most suitable.In practice, the quantification of boron using an ICP-AES was very satisfactory but a second titration technique was needed to confirm ICP-AES results. The titration of boron using the carminic acid assay was chosen. In order to remove interfering ions, a simple laboratory made purification device was set up. A protocol was developed in order to measure the boron concentration by the carminic acid assay. This led to consistent data with ICP-AES results.