- Email: [email protected]
Results for the “REIMEP 18” inter-laboratory comparison campaign for the measurement of uranium isotope ratios
A532
Goldschmidt Conference Abstracts 2006
Improved techniques and certified reference materials for nuclear and geological isotope ratio measurements S. RICHTER1, R. WELLUM2 1
Institute for Reference Materials and Measurements, Geel, Belgium ([email protected]) 2 Institute for Reference Materials and Measurements, Geel, Belgium ([email protected]) Isotope mass spectrometry is an important technique for a variety of geological samples analyses. Isotopic measurements made for geological purposes may have important scientific and even legal consequences and therefore require careful quality control. In order to prove the accuracy of isotopic measurements and to calibrate detectors such as secondary electron multipliers (single or multiple ion counters) the use of reference materials is required. This presentation gives an overview about state of the art measurement techniques and reference materials for nuclear isotope ratio measurements, in particular those applicable for geological purposes. At the IRMM several projects for the certification of new reference materials suited for nuclear and geological isotope ratio analyses are ongoing. For instance the re-certification of the IRMM-184 uranium isotopic reference material allows improved quality control and instrument calibration for measurements of close to natural or equilibrium samples with a 234U/238U ratio of approximately 5.5E 5 (Richter et al., 2005). An improved technique for the measurement of 234U/238U ratios for this kind of samples using Faraday detectors for both 234U and 238U will be introduced and compared with previous techniques using an ion counter to detect 234U. On the other hand, for a variety of isotope ratio measurements, e.g., measurements of 230Th/232Th ratios in the order of 6E 6, the use of secondary electron multipliers in ion countering mode is still required. In order to assess the performance of secondary electron multipliers and allow for accurate correction of detector non-linearity, special isotope reference materials are needed (Richter et al., 2001). As a replacement of the wellknown IRMM-072/1-15 series, the new series IRMM-074/1-10 has been prepared, characterized by a 235U/238U ratio of 1 and 233 U/238U ratios varying in 10 steps from 1 down to 10 6. Examples for linearity tests and possible correction procedures for nonlinearity using these isotope reference materials will be given.
References Richter, S., Alonso, A., Ku¨hn, H., Verbruggen, A., Wellum, R., Taylor, P.D.P., 2005. IJMS 247, 37–39. Richter, S., Goldberg, S.A., Mason, P.B., Traina, A.J., Schwieters, J.B., 2001. IJMS 206 (1–2), 105–127. doi:10.1016/j.gca.2006.06.980
Results for the ‘‘REIMEP 18’’ inter-laboratory comparison campaign for the measurement of uranium isotope ratios S. RICHTER, R. WELLUM Institute for Reference Materials and Measurements, Geel, Belgium ([email protected]; [email protected]. int) Inter-laboratory comparisons are organized for a variety of sample types and elements in order assess the performance of isotopic measurements on a worldwide level. The REIMEP 18 (Regular International Measurement Evaluation Program) campaign for the measurement of uranium isotope ratios in nitric acid was started in December 2005. Four samples of 2.5 mg uranium, ranging from depleted up to slightly enriched uranium, are sent to more than 70 participating laboratories, coming mainly from the nuclear safeguards and the isotope geochemistry area, and using a variety of techniques such as aspectrometry, TIMS, ICP-MS, AMS, RIMS, etc. As observed during several REIMEP campaigns done during the past 10 years, REIMEP 18 is designed to show the present state of uranium isotope measurements and gives the opportunity for participating laboratories to evaluate their own performance, to identify possible problems and to improve their own measurement procedures. Due to instrumental improvements in measurement techniques and instrumentation continuously going on over the years, measurement campaigns such as REIMEP are an important and very much appreciated way to achieve an ongoing careful quality control on an international level. Certification measurements at IRMM are performed using recently upgraded techniques for high precision and high accuracy uranium isotope ratio measurements. 235U/238U measurements are performed using a UF6 gas source mass spectrometer, calibrated using synthetic isotope mixtures. 234U/238U measurements, even down to values of 5.5E 5 (equilibrium value) are performed on a TRITON TIMS, using 1E12 Ohm Faraday cup amplifiers for the detection of 234U in order to improve the signal-to-noise ratio, so without the need to use ion counting. 236 U/238U measurements are performed on a TRITON TIMS using a procedure in which 236U was detected using an ion counter and which has been validated using our special synthetic mixtures with 236U/238U = 1E 6, 1E 7 and 1E 8. Details of the sample preparation and certifications will be given as well as comparative results of the measurements made by all (>70) participating laboratories worldwide. Results will be discussed regarding the use of various measurement procedures, calibration techniques, instrumentation, etc. doi:10.1016/j.gca.2006.06.981
Goldschmidt Conference Abstracts 2006
Improved techniques and certified reference materials for nuclear and geological isotope ratio measurements S. RICHTER1, R. WELLUM2 1
Institute for Reference Materials and Measurements, Geel, Belgium ([email protected]) 2 Institute for Reference Materials and Measurements, Geel, Belgium ([email protected]) Isotope mass spectrometry is an important technique for a variety of geological samples analyses. Isotopic measurements made for geological purposes may have important scientific and even legal consequences and therefore require careful quality control. In order to prove the accuracy of isotopic measurements and to calibrate detectors such as secondary electron multipliers (single or multiple ion counters) the use of reference materials is required. This presentation gives an overview about state of the art measurement techniques and reference materials for nuclear isotope ratio measurements, in particular those applicable for geological purposes. At the IRMM several projects for the certification of new reference materials suited for nuclear and geological isotope ratio analyses are ongoing. For instance the re-certification of the IRMM-184 uranium isotopic reference material allows improved quality control and instrument calibration for measurements of close to natural or equilibrium samples with a 234U/238U ratio of approximately 5.5E 5 (Richter et al., 2005). An improved technique for the measurement of 234U/238U ratios for this kind of samples using Faraday detectors for both 234U and 238U will be introduced and compared with previous techniques using an ion counter to detect 234U. On the other hand, for a variety of isotope ratio measurements, e.g., measurements of 230Th/232Th ratios in the order of 6E 6, the use of secondary electron multipliers in ion countering mode is still required. In order to assess the performance of secondary electron multipliers and allow for accurate correction of detector non-linearity, special isotope reference materials are needed (Richter et al., 2001). As a replacement of the wellknown IRMM-072/1-15 series, the new series IRMM-074/1-10 has been prepared, characterized by a 235U/238U ratio of 1 and 233 U/238U ratios varying in 10 steps from 1 down to 10 6. Examples for linearity tests and possible correction procedures for nonlinearity using these isotope reference materials will be given.
References Richter, S., Alonso, A., Ku¨hn, H., Verbruggen, A., Wellum, R., Taylor, P.D.P., 2005. IJMS 247, 37–39. Richter, S., Goldberg, S.A., Mason, P.B., Traina, A.J., Schwieters, J.B., 2001. IJMS 206 (1–2), 105–127. doi:10.1016/j.gca.2006.06.980
Results for the ‘‘REIMEP 18’’ inter-laboratory comparison campaign for the measurement of uranium isotope ratios S. RICHTER, R. WELLUM Institute for Reference Materials and Measurements, Geel, Belgium ([email protected]; [email protected]. int) Inter-laboratory comparisons are organized for a variety of sample types and elements in order assess the performance of isotopic measurements on a worldwide level. The REIMEP 18 (Regular International Measurement Evaluation Program) campaign for the measurement of uranium isotope ratios in nitric acid was started in December 2005. Four samples of 2.5 mg uranium, ranging from depleted up to slightly enriched uranium, are sent to more than 70 participating laboratories, coming mainly from the nuclear safeguards and the isotope geochemistry area, and using a variety of techniques such as aspectrometry, TIMS, ICP-MS, AMS, RIMS, etc. As observed during several REIMEP campaigns done during the past 10 years, REIMEP 18 is designed to show the present state of uranium isotope measurements and gives the opportunity for participating laboratories to evaluate their own performance, to identify possible problems and to improve their own measurement procedures. Due to instrumental improvements in measurement techniques and instrumentation continuously going on over the years, measurement campaigns such as REIMEP are an important and very much appreciated way to achieve an ongoing careful quality control on an international level. Certification measurements at IRMM are performed using recently upgraded techniques for high precision and high accuracy uranium isotope ratio measurements. 235U/238U measurements are performed using a UF6 gas source mass spectrometer, calibrated using synthetic isotope mixtures. 234U/238U measurements, even down to values of 5.5E 5 (equilibrium value) are performed on a TRITON TIMS, using 1E12 Ohm Faraday cup amplifiers for the detection of 234U in order to improve the signal-to-noise ratio, so without the need to use ion counting. 236 U/238U measurements are performed on a TRITON TIMS using a procedure in which 236U was detected using an ion counter and which has been validated using our special synthetic mixtures with 236U/238U = 1E 6, 1E 7 and 1E 8. Details of the sample preparation and certifications will be given as well as comparative results of the measurements made by all (>70) participating laboratories worldwide. Results will be discussed regarding the use of various measurement procedures, calibration techniques, instrumentation, etc. doi:10.1016/j.gca.2006.06.981