Volume 113, Issue 7

Radio-chronometric studies on plutonium (Pu) materials require independent measurement of the Pu (parent) content and isotopic distribution as well as concentration and isotopic distribution of the plutonium isotopic decay products. We performed a series of experiments to demonstrate the consistency of separations using the Lewatit MP 800 macroporous anion exchange resin and the AG MP-1M resin with traceable Pu isotopic certified reference material (CRM) standards 136, 137, 138, and 126-A. Two different mesh-sizes of the AG MP-1M resin were tested and the 50–100 mesh size resin was found to work more efficiently for the separation task. Both Lewatit and AG MP-1M resins were found to perform satisfactorily for quantitatively extracting the americium (Am) and uranium (U) progeny as well as gallium (Ga) present as a tracer in the Pu material. Both resins were effective in removing isobaric interferences from the Pu fraction used in isotopic measurements by thermal ionization mass spectrometry (TIMS). To address the co-elution of uranium and gallium, Alizarin red S (ARS) was used as a colorimetric dye to determine the behavior of UO 2 2+ and Ga 3+ on AG MP-1M resin with various acidic solutions as eluents using UV–vis spectra. Poor resolution of these peaks complicated quantitative analysis by UV–vis spectroscopy, but these results were informative in planning automated separation experiments by HPLC. LA-UR-24-28919 .

Crystalline rock is considered a potential host rock for a deep geological repository (DGR) for storing nuclear waste. Biotite is a common accessory mineral found in crystalline rocks such as granite and tonalite that plays an important role in the absorption of selenium (Se). In particular, the radioisotope Se-79 is widely present in spent nuclear fuel, and it is crucial for evaluating the suitability of a DGR for storing nuclear waste. In the anticipated reducing conditions of a DGR, the prevalent oxidation state would be Se (-II). However, the low solubility of Se under reducing conditions means that traditional spectrometry methods are not effective at studying the sorption mechanisms of Se (-II). Therefore, this study investigated the sorption mechanisms of Se (-II) on biotite under reducing conditions by using density functional theory (DFT) calculations to investigate the inner-sphere complex and outer-sphere complex reactions. Both complexes were found to contribute to sorption of Se (-II) on biotite with the outer-sphere complexes being the primary sorption mechanism under the naturally neutral groundwater conditions. The results of the DFT calculations were consistent with the sorption experimental data and the results of the surface complexation modeling, which further confirmed the significance of the inner-sphere and outer-sphere complexes to the sorption of Se (-II) on biotite under a wider range of pH conditions.

The paper introduces two reverse-tandem schemes of the 140 Ba → 140 La radionuclide generator which allow obtaining the daughter radionuclide 140 La for different applications in nuclear spectroscopy and as a tracer for radiochemical separations. The tandem generator system includes two stages: a chromatographic separation of parent and daughter radionuclides based on the main reverse column (cation-exchange column), and purification based on tandem column (extraction column). The main chromatographic separation is carried out in acetic acid media. Use of 140 La preparation with high specific activity in the perturbed angular γγ-correlation method is discussed.

Wastes from tin sulfide ore mining can serve as a secondary raw materials for obtaining rare and rare-earth elements (REE). This work demonstrates the possibility of effectively using instrumental neutron activation analysis (INAA) with a 252 Cf radionuclide source to determine the content of Sc, In and a number of REE content in tailings from tin sulfide ores and monominerallic samples of various compositions. For samples with volumes of 50 cm 3 , with the activation time of 7 days and the measurement time of 1–2 h, the calculated Minimum Detectable Concentrations are sufficient for the quantitative determination of Sc and REE (La, Sm, Eu) below the average upper continental crust concentration (UCC). Elevated levels of strategic metals were detected in samples collected from the tailings dump of the Khrustalnensky Mining and Processing Plant (KhGOK) in Kavalerovo District and the tailings dump of the Krasnorechenskaya Concentrating Mill (KCM) in Dalnegorsk District of the Primorsky Krai, Russia. Elevated concentrations of Sc (2.1 times UCC) and In (1.8 times UCC) were detected in the tailings sample after cassiterite secondary enrichment. A decrease in Sc concentration was detected in the upper layer of the KhGOK tailings dump. Increased In content 141–575 times UCC was detected in tailings samples from KCM. Conducted analyses show the prospects of processing the KCM tailings enrichment for indium by-product recovery. INAA could be applied both to assess the reserves of some valuable metals and develop the technology of their extraction.

Phenolic antioxidants (PhA), a novel antioxidant for natural rubber (NR), were used in the current study. As anti-aging agents, different concentrations of gallic acid (G) or tannic acid (T) were added to NR/PhA composites to increase their heat resistance. The NR/PhA composites’ mechanical, Physico-chemical, and DSC characteristics were evaluated, as well as their thermo-oxidative aging evaluations. This led to a significant improvement in the mechanical properties of the NR/PhA composites, making them superior to the NR/Antage (as a traditional antioxidant) composites. Additionally, the addition of phenolic antioxidants raised the crosslinking density of the NR composites, which significantly impacted the mechanical characteristics. According to the findings, phenolic antioxidants enhanced the NR/silica composites’ resistance to solvent extraction and thermo-oxidative aging, much like Antage. Upon ionizing irradiation, the mechanical characteristics of the vulcanized composites rise with increasing absorbed dose at 10 kGy and then decrease at 30 kGy.

In this study, the gamma radiation shielding properties of tin (Sn)-containing polymer composites were investigated. A polymer matrix was created with cobalt octoate (6 %), methyl ethyl ketone peroxide (MEKP), and unsaturated polyester resin. Then, as filler, Sn was introduced to this polymer matrix at specific rates. The mass attenuation coefficients, linear attenuation coefficients, radiation transmission factor, half value layers, mean free path values, and effective atomic numbers parameters were acquired in order to investigate the gamma radiation attenuation properties of the fabricated polymer composites. The HPGe detector was used to conduct experimental research at 22 distinct energies emitted from 22 Na, 54 Mn, 57 Co, 60 Co, 133 Ba, 137 Cs, 152 Eu and 241 Am radioactive sources in the photon energy range of 59.5–1,408.0 keV. The theoretical results and each acquired experimental result were compared. It was found that the sample encoded with Sn (20 %) provides the best gamma radiation protection among the composites under study.

The optical and radiation attenuation properties of zinc-tellurite glass modified with La 2 O 3 are investigated in this work. The density increased from 3.13 to 4.73 g cm −3 as the concentrations of La 2 O 3 rises, indicating a significant physical property. A shift in absorption to lower energy levels is indicated by the Urbach energy ( E u ) rising from 0.307 to 0.335 and the optical band gap narrowing from 3.36 to 1.36 eV for ( E opt indi ${E}_{\text{opt}}^{\text{indi}}$ ), and from 4.06 to 1.5 eV for ( E opt di ${E}_{\text{opt}}^{\text{di}}$ ). This study concludes that the zinc tellurite glasses doped with La 2 O 3 showed improved optical characteristics for optical semiconducting devices. LAC (cm −1 ) increases from 0.115 to 0.183 at 15 MeV and from 140.97 to 223.49 cm −1 at 0.015 MeV as the La 2 O 3 content increases, indicating a significant improvement in radiation shielding effectiveness. The high (LAC) values indicate enhanced photon absorption, making this glass a strong candidate for radiation shielding in medical applications. Overall, this study indicated that La 2 O 3 could offer better shielding properties to the glass samples.