Radiation protection calibrations are performed in reference radiation fields established according to ISO 4037-1 standard. Accurate X-ray tube voltage measurements are necessary for X-ray radiation qualities, because many relevant parameters, most importantly, conversion coefficients from air kerma to operational quantities, depend on tube voltage. The standard requires invasive measurements using a calibrated voltage divider, but this requires significant additional investments and is relatively complicated. Other, non-invasive, methods exist, but they are not recommended by the standard. In this paper, the invasive and non-invasive methods are compared and their uncertainty budgets are analyzed. Tube voltage range between 40 kV and 150 kV was investigated. Comparison between different methods is excellent within the reported uncertainties, with only 2 non-conforming results, out of 91. The results show that non-invasive methods, such as linear extrapolation by spectrometry, spectrometric practical endpoint, and X-ray multimeters can be used to achieve the measurement uncertainties that meet the requirements for most of standard X-ray radiation qualities, which makes them a viable alternative to voltage dividers.
The structural and compositional characteristics of the powder ceramic waste were investigated using XRF, FTIR, XRD, and SEM–EDS analyses, confirming a highly crystalline structure, the characteristic ZrSiO4 tetrahedral vibrations, and a homogeneous elemental distribution dominated by ZrO2 and SiO2. The radiological assessment indicated activity concentrations of 238U (2429 ± 100.6 Bq kg−1), 226Ra (2527 ± 86 Bq kg−1), 232Th (513.3 ± 48.7 Bq kg−1), and 40K (193.14 ± 13.5 Bq kg−1). The calculated radiological hazard indices exhibited relatively high values, including radium equivalent activity (3278 ± 155 Bq kg−1), absorbed dose rate (1488 ± 69 nGy h−1), and annual effective dose (1.8 ± 0.1 mSv y−1), all of which were substantially higher than the corresponding internationally recommended reference values. Additional radiological indicators further demonstrated the elevated radiological characteristics of the investigated waste and highlighted the need for appropriate radiation protection and waste management measures. These findings are primarily attributed to the elevated activity concentrations of Naturally Occurring Radioactive Materials (NORM) present in the investigated ceramic waste. Overall, the investigated zirconium silicate waste was classified as TENORM, emphasizing the need for appropriate regulatory control, radiological screening, radiation protection measures, and controlled waste management strategies to ensure its safe handling and potential reuse.
Molten-salt electrorefining (ER) is essential for purifying chemically active metals, including plutonium, that cannot be processed in aqueous systems. However, systematic experimental studies linking operating parameters to ER performance and reliable process-monitoring criteria remain limited. In this work, tin–nickel (Sn-Ni) electrorefining in a LiCl-KCl-CaCl 2 eutectic is employed as a non-radioactive surrogate to investigate the effects of anode composition, temperature, and SnCl 2 seeding concentration. Kilogram-scale ER experiments were conducted using an automated operating protocol that monitored voltage, current, static refining resistance, and back-electromotive force (back-emf) as run termination indicators. Product yield, faradaic efficiency, and refined-metal purity were quantified through post-run mass balances and chemical analysis. All conditions produced refined Sn with ≥99.5 wt% purity. Increasing SnCl 2 seeding concentration and operating temperature improved product yield, whereas increasing Ni impurity in the anode feed from 2 to 3 wt% significantly reduced yield and faradaic efficiency. Comparison of monitoring metrics showed static refining resistance to be more consistent and reliable than back-emf for identifying run completion, as back-emf exhibited false positives and missed late-stage transitions. These results provide practical guidance for ER process control and reinforce the Sn-Ni system as a surrogate for molten-salt electrorefining of plutonium.
Understanding the dissolution behavior of UO 2 in carbonate-bearing groundwater is critical for predicting the long-term release of uranium from spent nuclear fuel in geological disposal environments. This study investigates the pH-dependent interfacial dissolution of UO 2 in these environments to identify distinct reaction regimes governed by surface chemistry. Two uranium oxide models with contrasting structural characteristics were examined: structurally disordered electrodeposited UO 2+x films and well-crystallized sintered UO 2 pellets exhibiting terrace-step morphologies. Dissolution processes were monitored using a combination of quartz crystal microbalance (QCM), atomic force microscopy (AFM), Raman spectroscopy, and inductively coupled plasma mass spectrometry (ICP-MS). Both materials exhibit consistent biphasic dissolution kinetics, characterized by an initial rapid uranium release followed by a slower, steady-state regime. Dissolution is accelerated under mildly acidic carbonate conditions (pH 6.0) and suppressed under highly alkaline conditions (pH 12.0). Under representative groundwater conditions (pH 8.0), the UO 2 surface develops a relatively stable interfacial layer involving partial oxidation and surface-bound carbonates. These findings demonstrate that pH-controlled interfacial chemistry and initial defect density fundamentally dictate uranium dissolution, providing critical mechanistic insights for predicting radionuclide release in deep geological repositories.
Multi-element-doped UO 2 SIMFUEL pellets were fabricated by high-pressure compaction and sintering at 1550–1700 °C under a reducing atmosphere to simulate chemically complex, high-burnup-equivalent fuel compositions. SEM, XRD, EDS, and ICP-MS characterization revealed pronounced microstructural evolution with increasing sintering temperature. Sintering at 1700 °C promoted substantial grain coarsening and densification up to 96.3% theoretical density, reducing interconnected porosity and effective grain boundary area relative to pellets sintered at 1550 °C. This microstructural stabilization enhanced resistance to aqueous dissolution during one-year semi-dynamic leaching tests conducted at 25–90 °C in accordance with the ASTM C1308 protocol. Dopants partitioned into chemically resilient metallic ε-type phases and more soluble dopant-bearing oxide regions, giving rise to element-specific dissolution kinetics governed by phase chemistry and microstructural connectivity. Mo release reflected both normalization artifacts and genuinely faster dissolution at lower burnup. Beyond compositional effects, elevated leaching temperatures consistently accelerated elemental release and were accompanied by subtle lattice contraction, consistent with partial oxidation of the fluorite matrix. Collectively, these processing–microstructure–dissolution relationships provide mechanistic insights for improving the chemical durability of multi-component fluorite-structured nuclear fuels in aqueous environments.
