Year
2008
Abstract
The ABACC-Brazilian-Argentine Agency for Accounting and Control of Nuclear Materials performs safeguard inspections jointly with the IAEA-International Atomic Energy Agency at enrichment plants in Brazil and Argentina. Particularly, at enrichment plants in Brazil that use centrifuge enrichment process, routine and unannounced inspections are performed and UF6 samples are taken from process lines and cylinders to verify the uranium enrichment conformity with design/operator declarations. ABACC has developed a UF6 sampling method for enrichment determination (named ABACC-Cristallini Method) which uses a fluorothene P-10 tube type containing alumina pellets that absorb and hydrolyze UF6 directly during the sampling. The alumina pellets retain up to few hundreds milligrams of U (in a solid compound – UO2F2) without the need of using liquid nitrogen during sampling. This new method has advantages compared to the currently used method that uses a Hoke tube as: the UF6 sample content left at the installation (archive sample) will be lower and less reactive, the laboratory procedures for manipulating the sample will be much easier, the residual uranium retained at the laboratory will be much lower, the sampling device is less expensive, there will be saves in transport cost as well, and it is relatively safer concerning radiological protection aspects during transportation. This paper describes the physical principle of the new method, the experiments carried out at laboratory taking into account different process parameters foreseen in real cases, and the development of a procedure for recovering the uranium retained inside the alumina pellets for the U enrichment measurement. The behavior of the new method is compared to the traditional one, showing no loss of accuracy for the enrichment determination with real UF6 samples taken from enrichment plants. The qualification strategy applied to the new method for routine safeguard application at the enrichment plants is presented in this paper as well.