Direct Compositional Characterization of (U,Th)O₂ Powders, Microspheres, and Pellets Using TXRF

Abstract

A total reflection X-ray fluorescence (TXRF) analysis method for direct compositional characterization of sintered and green (U,Th)O2 samples in different forms (e.g., pellets, powders, and microspheres) without sample dissolution has been developed for the first time. The methodology involves transfer of only a few nanograms of the sample on the TXRF sample support by gently rubbing the samples on supports or taking their tiny uniform slurry in collodion on the sample support, drying them to make thin film, and measuring the TXRF spectra of the specimens thus prepared. This approach minimizes the matrix effects. Uranium determinations from the TXRF spectra of such specimens were made with respect to thorium, considering it as an internal standard. Samples having uranium atom percent (at%) from 0 to 100 in (U,Th)O2 were analyzed for uranium in comparison to thorium. The results showed an average precision of 2.6% (RSD, 2σ, n = 8). The TXRF-determined results deviated from expected values within 5%. The TXRF results were compared with those of biamperometry with good agreement. The lattice parameters of the solid solutions were calculated using their XRD patterns. A good correlation between lattice parameters and TXRF-determined U at% and between TXRF-determined U at% and expected U at%, calculated on the basis of preparation of (U,Th)O2 solid solutions, was obtained. The developed method is capable of analyzing (U,Th)O2 samples directly with almost negligible sample preparation and is well suited for radioactive samples. The present study suggests that this method can be extended for the determination of U,Th and Pu in other nuclear fuel materials (e.g., nitrides, carbides, etc.) in the form of pellets, powders, and microspheres after suitable modifications in sample handling procedure.

Direct Determination of Oxidation States of Uranium in Mixed-Valent Uranium Oxides Using Total Reflection X-ray Fluorescence X-ray Absorption Near-Edge Spectroscopy

“…However, Tiwari et al have reported that not only the sample amount but particle size also plays an important role during the consideration of sample absorption effect in the TXRF geometry. , It was shown that particle size above 1 μm only severely affects the emitted TXRF fluoresce intensity. In one of our earlier studies on the determination of U and Th in their mixed oxide pellets using TXRF, we have shown that the particle size of the analytes that stick on the TXRF sample support during the rubbing process ranges between 200 and 500 nm. In this study also we have used similar sample preparation, and therefore, such small particles shall not pose much absorption effect.…”

“…In addition the sample can be studied as such after sticking a few particles on TXRF supports without any processing, e.g., pelletization with boric acid or cellulose or dispersion in hexane. For an effective sample preparation, a very small amount of sample may be rubbed on TXRF sample support, and this specimen may be probed for TXRF-EXAFS or XANES measurements. Recently, a study for finding out the uranium oxidation state in U 4 O 9 and U 3 O 8 has been reported using the U M 5 edge .…”

Selective Micellar Extraction of Ultratrace Levels of Uranium in Aqueous Samples by Task Specific Ionic Liquid Followed by Its Detection Employing Total Reflection X-ray Fluorescence Spectrometry

“…Quartz was used as a sample support for TXRF measurements on which a few microliters of the sample was deposited and dried. The complete details of this spectrometer is given elsewhere . For TXRF measurements, a live time of 1000 s was used.…”

“…The complete details of this spectrometer is given elsewhere. 40 For TXRF measurements, a live time of 1000 s was used. The U concentration in the supernatant was determined by using ICP-quadrupole MS (VG PlasmaQuad PQ2 Turbo Plus).…”

Direct non-destructive total reflection X-ray fluorescence elemental determinations in zirconium alloy samples

“…Moreover, during dissolution and matrix separation procedures, there is a probability that additional impurities may be introduced in the sample solutions. Therefore, non-destructive analytical methods are always desirable for elemental characterization of such samples, as such methods require minimum sample preparation and avoid the dissolution as well as separation steps (Acharya et al, 2004;Dhara et al, 2015). For radioactive materials, the non-destructive methods have an added advantage of producing no or a very small amount of analytical waste.…”