Avoiding polyatomic interferences in measurements of lanthanides in uranium material for nuclear forensic purposes

Measurements of the lanthanide series with ICP-SF-MS provide low detection limits but suffer from oxides of the lighter lanthanides interfering on the heavier ones. In this work, two different methods to measure the lanthanide series without interferences, were investigated and compared to measuring the lanthanides directly with a standard sample introduction system. It is shown that by using a desolvating sample introduction system during measurements, the impact of polyatomic interferences are eliminated. It is also shown that using chemical separations to separate the elements in the lanthanide series into three fractions almost eliminates polyatomic interferences, while direct measurements with a standard sample introduction system may lead to inaccurate results due to interferences

Evaluation of different methods for measuring 89Sr and 90Sr: Measurement uncertainty for the different methods as a function of the activity ratio

In case of a radiological emergency situation involving e.g. fission of uranium or plutonium, analysis of radioactive strontium will be of importance. The primary radionuclides of interest are90Sr, its progeny90Y and89Sr. A few days following an event,89Sr will be the predominant radioisotope of strontium. Most methods found in the literature are valid and applicable when measuring90Sr, but when samples contain both89Sr/90Sr interference problematics arise. How these interferences are dealt with will have an effect on the uncertainty of the90Sr determination. This work aims at evaluating three measurement approaches, all mentioned in the literature, with respect to the measurement uncertainty when determining90Sr in an emergency preparedness situation and to propose a suitable measurement strategy

Experimental validation of corrections factors for gamma-gamma and gamma-X coincidence summing of Ba-133, Eu-152, and Sb-125 in volume sources

True coincidence summing correction factors for Ba-133, Eu-152 and Sb-125 were determined experimentally for a small volume source and compared with correction factors obtained with three softwares (EFFTRAN-X, GESPECOR and VGSL). The radionuclides investigated have a relatively challenging decay scheme and their spectra are known to suffer from losses due to summation (gamma-gamma, gamma-X and X-X) when measured at close distances on a HPGe detector sensitive to low energy photons. This study shows that the softwares were in good agreement with each other and the experimental data and the calculated activity was consistent with the activity in the volume source

Gamma spectrometry in the ITWG CMX-4 exercise

Low enriched uranium samples of unknown origin were analyzed by 16 laboratories in the context of a Collaborative Materials Exercise (CMX), organized by the Nuclear Forensics International Technical Working Group (ITWG). The purpose was to compare and prioritize nuclear forensic methods and techniques, and to evaluate attribution capabilities among participants. This paper gives a snapshot of the gamma spectrometric capabilities of the participating laboratories and summarizes the results achieved by gamma spectrometry

Comparing results of X-ray diffraction, \ub5-Raman spectroscopy and neutron diffraction when identifying chemical phases in seized nuclear material, during a comparative nuclear forensics exercise

This work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear forensic round-robin exercise. In this work powder X-ray diffraction (p-XRD) is regarded as the reference technique. Neutron diffraction produced a superior high-angle diffraction pattern relative to p-XRD. Requiring only small amounts of sample, \ub5-Raman spectroscopy was used for the first time in this context as a potentially complementary technique to p-XRD. The chemical phases were identified as pure UO 2 in two materials, and as a mixture of UO 2 , U 3 O 8 and an intermediate species U 3 O 7 in the third material

Development and Applications of some Radioanalytical Procedures: Analysis of β- and α-Emitting Radionuclides Using Radiometric and ICP-MS Detection Methods

Analyses of radionuclides are important in environmental monitoring and in research. However, as in the analysis of many other species, interferences may be a problem. In a-spectrometric detection, 238Pu interferes with 241Am, owing to their similar decay energies. In inductively plasma mass spectrometry (ICP-MS), species with the same mass-to-charge ratios will not be resolved by a quadrupole mass filter. However, if interferences are removed prior to measurement, the detection will be specific. Measurement of pure .beta.--emitting radionuclides with radiometric detection will suffer to a high degree from specificity. However, in the analysis of 90Sr, a measurement of the daughter nuclide, 90Y, offers an opportunity. This radionuclide is a high-energy .beta.--emitter, and its short half-life provides an opportunity to verify the half-life. Short-lived radionuclides are often more readily (by means of the detection limit) measured using radiometric detection, because a very small mass is connected to a high activity. On the other hand, long-lived radionuclides are more readily detected using mass sensitive detection, e.g. ICP-MS, if no natural radioactive nuclide of the element is present in the sample. The half-life at which the techniques will be most competitive with respect to the detection limit is of course floating, depending on the methods utilized. Analytical procedures for the assay of some radionuclides in bentonite clay were developed. The radionuclides included are: 90Sr, 99Tc, 236U, 237Np, 239Pu, 241Am and 244Cm. Both radiometric and ICP-MS measurements were used, depending on the half-life of the radionuclides. These analytical procedures were applied to bentonite clay samples from a radionuclide diffusion and spent nuclear fuel leaching experiment. Results regarding the transport of strontium, technetium and some actinides in bentonite clay, as well as the release of these radionuclides from spent UO2 fuel, are presented

Achieving confidence in trace element analysis for nuclear forensic purposes: ICP-MS measurements using external calibration

In this work, problems arising from performing trace element analysis using inductively coupled plasma—mass spectrometry with low measurement uncertainties are addressed. It is shown that some reference materials certified for massic concentration of lanthanides may have either deviating concentrations or underestimated measurement uncertainties. It is also shown that the choice of methods for sample preparation and linear regression to perform external calibration is affecting the outcome of the measurement results and their uncertainties. The results show that, from the selection of methods investigated in this work, the lowest measurement uncertainties can be achieved by using weighted linear regression to evaluate the calibration function and gravimetric dilutions of samples

Uncertainty evaluation in gamma spectrometric measurements: Uncertainty propagation versus Monte Carlo simulation

Calculation and reporting of combined measurement uncertainties are important in decision making processes, and a more proper uncertainty estimation can reduce the risk and/or the cost associated with decisions for example after radiological incidents and in free release measurements of radioactive waste. However, sound decisions demand a sound uncertainty estimation. In this work we present the possible consequences when uncertainty propagation is applied to gamma-ray spectrometry measurements involving assumed probability density functions for an efficiency transfer having different metrological quality by comparison with Monte Carlo simulations

Implementation of calculation codes in gamma spectrometry measurements for corrections of systematic effects

Four calculation codes were implemented on experimental data to calculate corrections of common systematic effects within high resolution gamma spectrometry. The detector parameters were sparsely optimized to imitate the usage that can be expected from personnel with limited experience. The transfer of the efficiency from the calibration geometry (60 ml, density 1.0 g/cm(3)) to 200 ml geometry (density 1.5 g/cm(3)) failed with all codes, which was discouraging. However, a majority of the other corrected activities deviated with less than 10 % from the reference activity values, even for density corrections or when corrections had been calculated for new source-detector-geometries. Smaller deviations, around 5 % or less, were achieved when corrections were done within the calibrated geometry. This shows a robustness of the calculation codes even if the in-data is not perfectly optimized