Journal of Radioanalytical and Nuclear Chemistry最新文献

The sodium waste stream has been immobilized into cementitous waste form with simultaneously high waste loading and chemical durability. The incorporation of Na₂CO₃ (5–15 wt.%) with growth of CaCO₃ slow down the formation of C–S–H gel, while the higher amount of Na₂CO₃ incorporation ratio (20–30 wt.%) leverages pH elevation and confined carbonate diffusion to enhance hydrated silica formation and silicate diversity. Compressive strength above 10 MPa and 7 MPa before and post freeze-thaw test can be achieved, with the long term Cs release rate around 5 mg/(m² d) can be seen, suggesting the robustness of the cementitous waste form.

A continuous flow-through, real-time radioxenon sensor array has been designed to monitor either ¹²⁷Xe or ¹³³Xe tracer gas as part of a series of underground chemical explosions in the Low-Yield Nuclear Monitoring (LYNM) Physics Experiment 1 (PE1). The sensors are pairs of shielded thallium-doped sodium iodide gamma-ray detectors that surround a gas measurement chamber. Each measurement chamber is connected to a sampling location in the geology surrounding the chemical explosion or in the access tunnel. The first experiment in the series, PE1 A, occurred in 2023 and the system quantified the ¹²⁷Xe tracer gas in the gas sampling lines for four weeks following the experiment execution. The array generated a set of radioxenon concentration time series with a 15-min resolution that will be used to refine subsurface gas transport models.

In this study, borosilicate glasses with different ZrO₂ contents were synthesized at 1200 °C and used to immobilize simulated TRPO waste. The effects of ZrO₂ content on the solid solution limit, microstructure, mechanical properties, and chemical stability of the solidified bodies were systematically analyzed. The results showed that with the increase of ZrO₂ content, the solid solution limit of TRPO waste increased from 20 to 30 wt%, and the degree of amorphization of the solidified bodies could be improved. The addition of ZrO₂ raised the number of bridging oxygen bonds in the solidified body and enhanced the degree of polymerization of the glass structure. For samples containing 4 wt% ZrO₂, the highest Vickers hardness and density values were 6.57 GPa and 2.89 g cm⁻³. Moreover, the 42-day normalized leaching rates of Ce, Nd, La, and Pr in the solidified bodies were about 10⁻⁵ g m⁻² d⁻¹. This work provides useful ideas for the optimization of the solidification matrix materials for high-level radioactive waste.

Graphical abstract

Thermally-treated spent ion-exchange resins (OIXRs) were immobilized by mixing 1 wt% ash with a metakaolin geopolymer. Stable ¹³³Cs simulated ¹³⁷Cs. Year-long semi-dynamic leaching experiments at pH 12.5 monitored changes in pH, conductivity and dissolved ions. Na, Al, Si were rapidly released into solution and 32% of Cs leached within 28 days. Ca uptake dominated, driving Na-Ca exchange and progressive N–A–S–H to C–A–S–H transformation. XRD, FE-SEM–EDX and ²⁷Al/²⁹Si MAS-NMR showed depolymerization, Ca-rich precipitates and loss of tetrahedral Al. Despite 59% Cs loss after 1 year, results demonstrate the matrix’s long-term chemical evolution and its promise as a sustainable OIXR wasteform.

Radiochronometry is a valuable tool for nuclear forensics for the determination of model ages to aim to understand a materials processing history. Interpretation of chronometers can be challenging in complex materials with discordant model ages observed. Measurements of helium resulting from the alpha decay of actinide materials are investigated to see if they correlate to ages and/or dates of casting or last heat treatment. We present the analysis of several plutonium samples, including CRM 126a via electrode furnace-gas analyser set up, to determine the suitability of helium as an additional chronometer. Additionally, a preliminary investigation into the carry-over of helium from plutonium metal into oxides formed at different temperatures, is reported.

To date, radiopharmaceuticals containing micro-sized carriers of radionuclides are actively being studied, as well as their use in radioembolization instead of ⁹⁰Y-containing microspheres. For such purposes, bentonite clays widely studied as a carrier of drugs seems perspective but their research as carriers of radionuclides in nuclear medicine is almost absent. In this study, bentonite samples were tested for the first time as a platform for a wide range of therapeutic radionuclides. Optimal conditions for the sorption of di- and trivalent therapeutic isotopes by the studied samples were identified. Stability in model biological media was investigated. Adsorption isotherms for the corresponding elements were obtained using the Freundlich and Langmuir models, and ΔG of the adsorption processes were determined. As a result, the studied samples were found to be promising carriers of bismuth (^212,213Bi) and ²²⁵Ac isotopes, including an “in vivo generator” ²²⁵Ac/²¹³Bi, opening up prospects for further research in laboratory animals.

Thermodynamic and experimental approaches were used to examine the stable phases, chlorination, and evaporation of chloride products during carbonization–chlorination decontamination of Cs- and Co-contaminated ion-exchange resins. Cs₂SO₄ was the stable phase for Cs under carbonization at 800 °C. Chlorination at 1000 °C for 30 min resulted in conversion and evaporation ratios of 0.925 and 0.314, respectively. Residual CsCl was completely removed by an additional heat treatment. For Co, Co₃O₄ was the primary carbonization product. At 900 and 1000 °C, only CoO was detected. Chlorination at 1000 °C led to conversion and evaporation ratios of 0.701 and 1.00, respectively.

Sodium salt waste (SSW) mainly contains sodium salts and ⁹⁰Sr/¹³⁷Cs, with a complex composition. This review presents the advantages and disadvantages of typical immobilization materials, focuses on analyzing the advantages of geopolymers in immobilizing SSW, and addresses the problems that need to be solved in the future, such as the solidification efficiency caused by the change of SSW compositions and the decline in the durability of the geopolymer waste–forms due to salt residues. The article also proposes coping strategies, including optimizing the solidification method through a multi–phase coexisting structure and improving the material durability through sintering technology.

This work presents ongoing efforts to develop a real-time program for detecting the direction and general location of a neutron source using the NoMad detector, a 15-tube He-3 array. This program is part of a larger proof-of-concept system focused on real-time neutron multiplicity monitoring, with potential applications during fuel debris removal at Fukushima Daiichi units 1, 2, and 3. The approach employs a random forest regression model, which predicts neutron source locations by learning the relationship between neutron count rates from the NoMad detector and the corresponding source positions. For real-time implementation, the system is designed to continuously collect neutron count data across all 15 tubes of the NoMad detector, feeding this data into the trained model to estimate the neutron source's location. To manage transient variations in count rates, a sliding time window approach will be applied, while optimization efforts aim for low-latency computation to support on-the-fly source localization. The random forest algorithm’s capacity to manage the non-linear relationship between neutron count rates and spatial positions is expected to address challenges from fluctuating neutron backgrounds and noise in high-radiation settings. Results for source location accuracy, latency, and resilience to background radiation fluctuations will be presented. Beyond Fukushima Daiichi, this system will have applications in nuclear nonproliferation and accident response, where its ability to provide real-time source location information will aid in critical decision-making.