Study On The Determination Of Impurities In Uranium Compounds By Inductively Coupled Plasma Mass Spectrometry

Uranium compounds are important nuclear fuel materials. The performance of nuclear fuel in the reactors depends on the chemical composition of its impurities, especially those elements with high cross section, causes thermal neutrons absorption, reducing the fuel efficiency. It is very important that confirming the type and determining the concentration of the impurities elements in uranium compounds during the nuclear fuel produce processing. Several techniques can be used in determination of impurities in uranium-based nuclear fuel, such as EDXRF(Energy-Dispersive X-Ray Fluorescence), FAAS(Flame Atomic Absorption Spectrometry), GFAAS(Graphite Furnace Atomic Absorption Spectrometry), ICP-OES(Inductively Coupled Plasma Optical Emission Spectrometry) or ICP-MS(Inductively Coupled Plasma Mass Spectrometry). The advantages of ICP-MS over the traditional techniques are lower detection limit, simpler spectra, higher dynamic range, higher sensibility, fast analysis speed, low sample consumption and ease operation, is applied to determine trace and ultra-trace level elements in environmental monitoring, nuclear safeguards, and nuclear forensic studies. It is known that lots of studies on determining small amounts of impurities in uranium compounds, but a little research on multi-element determination, so it is necessary to establish a method which can simultaneous determinate dozens of elements in uranium compounds.This thesis introduces the principle of the ICP-MS and its applications in determination impurities of nuclear uranium compounds. It does research in two aspects: the direct determination of impurities in nuclear grade uranium compounds by ICP-MS and ICP-MS in combination with tributyl phosphate extraction chromatography(CL-TBP) applied to detect impurities in nuclear grade uranium compounds. The sample was dissolved by nitric acid, then using ICP-MS direct determination of 46 impurities in uranium matrix. The recovery of the method was in range of 93%~113% for impurities. The procedure developed was verified using the Certified Refernece Materials. The concentration of the uranium matrix below 500 mg·L-1 the analytical agrees well. The method is simply, time-saving and accurate which provide relative standard deviations of the verified elements were less than 17%.The chromatography behavior of a tributyl phosphate levextrel resin was investigated for the separation of impurities from the high concentration uranium matrix, the experiment conditions were determined as follows: concentration of 5 mol·L-1 nitric acid as pro-equilibratd solution and impurities eluent. A quartz column of diameter 3 mm was packed with 12.5 cm height of CL-TBP with adsorption column capacity of 0.148 g uranium(equivalent to 1.0 g dry resin). Deionized water was choosing as uranium desorption solution. The method was used CL-TBP as stationary phase, and concentration of 5.0 mol·L-1 nitric acid as mobile phase, using inductively coupled plasma mass spectrometry to determine the concentration of 41 impurities in effluent solution. The recovery of the method was in range of 91%~109% for impurities. The method is accurate and precise, provided excellent analytical date for proposed Certificate Reference Materials(CRMs), offered standard deviations of the verified elements were less than 20%. Using the established method, we have determined the impurities in urano-uranic oxide(U3O8) samples and quality control reference materials(NBL CRM 124). The testing results are consistent with the certified values of reference materials, meeting the requirement of quality control. Participating the inter-laboratory comparison for analysis of impurities held by institute, we achieved the acceptable score.