Year
1995
Abstract
A major activity of \"PERLA\", the PERformance LAboratory of the Joint Research Center of the European Union is to select, procure and characterize Uranium and Plutonium working reference materials representative of the nuclear materials, subject to safeguards verification measurements by means of increasingly precise NDA techniques. These reference materials ensure the traceability of the measurements back to international standard units. They are used to develop, improve and calibrate the NDA instruments and to train the inspectors to operate these instruments correctly. The paper describes the approach adopted for the procurement, production and characterization plans of LEU standards in the form of UO2 pellets, U3O8 powders, pins and a mock up PWR fuel element. Homogeneity tests, weighing protocols, humidity checks and impurity analysis were performed on the feed materials (UO2 powders) and on the final product materials (U3O8 powders and UO2 pellets). The sampling and the analytical scheme followed for the characterization and the analytical results obtained are presented and statistically evaluated. The characterization of these reference materials carried out by four experienced analytical laboratories allows a certification of the uranium content and isotopic abundance with small confidence intervals in a minimal time and minimal analytical effort.