This study presents a simulation-based framework for evaluating scaling factor (SF) models in activated decommissioning waste, emphasizing the importance of material- and activation-dependent heterogeneity. Neutron flux and activation data for the core barrel (CB), thermal shield (TS), and reactor vessel (RV) were generated using MCNP and ORIGEN-S to form a theoretical population. Unlike operational waste, CB and TS exhibited segmented SF distributions driven by neutron flux gradients, deviating from the conventional log-normal assumption. As activation levels increased, distribution nonlinearity became more pronounced. Polynomial regression effectively captured these effects, and regression models outperformed mean-based models in predictive accuracy. However, under realistic uncertainties, their advantage in confidence interval width was lost and prediction stability declined. Mean-based models, while robust, consistently underestimated difficult-to-measure nuclide inventories. To address this, a Gaussian Mixture Model–based zoning method was introduced to enhance sampling representativeness. This approach reduced underestimation and confidence intervals—even with very small sample sizes—and became increasingly effective with larger samples. The RV showed highly uniform behavior due to low activation, suggesting it may be treated as homogeneous waste. As SF confidence intervals are highly sensitive to sampling and analytical uncertainty, sample sizes should reflect these uncertainty sources to ensure reliable inventory estimation.

Liquid scintillation counting (LSC) efficiency for tritium (3H) is calibrated using polynomial quench correction models and uncertainty analysis. We employed a previously published dataset of 3H quench standards, covering a wide range of quench levels. Second-, third-, and fourth-order polynomial models were fitted to the calibration data based on the published relationship between the instrument's quench index and 3H counting efficiency. This was intended to provide representative cases for uncertainty analysis, rather than to identify an optimal functional form. The propagated uncertainties were quantified across the quench range, revealing that the intermediate and high quench regions are particularly sensitive; small errors in quench or calibration yield disproportionately large efficiency uncertainties. In contrast, the low-quenching region exhibited a relatively minor uncertainty contribution. These results highlight the methodological importance of applying rigorous uncertainty propagation to 3H LSC efficiency calibrations. In particular, explicitly accounting for calibration-fit uncertainty via the law of propagation of variances ensures a more reliable activity estimation and alignment with modern metrological standards, which is crucial for the confident quantification of low-level 3H.

The epsilon particles that result from UO2 fuel nuclear fission possess both advantages and disadvantages from a spent nuclear fuel (SNF) management perspective. In this study, the effect of epsilon particles, namely Ru, Mo, and Pd, inherent in simulated UO2 pellets is examined. Various analytical methods have been used to explore the changes in the structural, surface, and electrochemical properties of which contain epsilon particles. A notable finding is that the epsilon particles are not evenly distributed and tend to clump together, transforming into a metallic state after sintering, as detailed in the X-ray diffraction analyses. Energy-dispersive X-ray spectroscopy analyses highlight interesting aspects of the distribution of elements, especially the disappearance of Pd during sintering, which is likely due to its high vapor pressure. Although the lattice structure of UO2 remains unchanged, the sizes of the grains and pores visibly change, which may influence the tendency of UO2 pellet-cracking. Despite the addition of the epsilon particles, the electrical conductivity analyses show no significant changes, suggesting that they act as minor impurities without affecting the structural lattice. However, their possible role as catalysts in electrochemical reactions opens new and interesting areas that require thorough investigation. Moreover, examining the anodic dissolution under various conditions provides detailed insights into UO2 dissolution and oxidation, revealing how epsilon particles subtly influence the oxidative dissolution process. This study clarifies the basic interactions and effects of epsilon particles in UO2 pellets and broadens the path for a deeper understanding and improvement of nuclear fuel matrices and steering advancements in the safe and effective use of nuclear energy.

This study evaluates calibration models for the triple-to-double coincidence ratio (TDCR) method in liquid scintillation counting, focusing on the relationship between TDCR values and detection efficiency for 3H and 14C. Four datasets were analyzed: three reconstructed from published literature and one obtained through original experimental measurements. A nonlinear core function (CF) model was compared with first- to third-order polynomial regressions. Model performance was assessed using root mean squared error (RMSE), mean absolute error (MAE), symmetric mean absolute percentage error (SMAPE), and the Akaike and Bayesian information criteria (AIC and BIC). While the CF model showed superior performance for 3H due to its inherently nonlinear response, simpler polynomial models-particularly linear and quadratic- yielded comparable accuracy for 14C across all datasets. These models also enable analytical uncertainty propagation and offer greater numerical stability. The findings support a model selection strategy that emphasizes simplicity and parameter parsimony without sacrificing accuracy. This work highlights the practical advantage of selecting the least complex model that sufficiently captures the efficiency-TDCR relationship.

Water pollution by metals is increasing. An electrode material, copper hexacyanoferrate (CuHCF), for capacitive deionization (CDI) to remove Co2+ from wastewater was developed. The asymmetric electrode structure of the CDI overcomes the limitations of traditional activated carbon electrodes (low ion removal capacity, ion removal rate, and charge efficiency). The specific capacitance of the CuHCF electrode (216.7 F g−1) at 1 mV s−1 was higher than that of a traditional electrode (92.0 F g−1), and its deionization capacity was 156.85 mg g−1 in 50 mg L−1 aqueous Co2+ (charge efficiency = 68.4

The radioactive cesium species (e.g., 137Cs) in radioactive waste have necessitated the development of strategies for its selective removal from contaminated water. In this study, we synthesized nickel-modified Prussian blue/maghemite (NiPB/γ-Fe2O3) composite materials exhibiting high selectivity for Cs ions. The composites were synthesized via a facile hydrothermal reaction, and their magnetism was confirmed through an X-ray magnetic circular dichroism measurement. The composites selectively separated Cs from solutions containing alkali and alkaline earth metal cations, with a removal efficiency of ≥ 99.7 %. The synthesis mechanism involved the hydrothermal reaction, including partial oxidation and subsequent γ-Fe2O3 formation. The maximum adsorption capacity of the NiPB/γ-Fe2O3 composites, assuming successful magnetic separation, was determined to be 102 mg g−1 using the Langmuir adsorption model. The powder X-ray diffraction patterns revealed enhanced crystallinity in the composites compared to NiPB, with a distorted structure framework from face-centered cubic to rhombohedral. XAS spectra showed changes in vibration peaks due to hydrothermal treatment, indicating partial oxidation of Fe(Ⅱ) to Fe(Ⅲ). The composites exhibited superparamagnetism, whereas NiPB showed no magnetization. These findings highlight the potential of NiPB/γ-Fe2O3 composites in environmental remediation and radioactive waste management, providing an effective solution for Cs removal from contaminated systems.

The influence of the Nd-doping ratio and oxygen vacancies on the structural properties and electrochemical reactivity of U1-yNdyO2-x (x ≈ y/2, y = 0.02, 0.06, and 0.1) solid solutions was investigated using X-ray diffraction, Raman spectroscopy, and cyclic voltammetry. Defect structures induced by oxygen vacancies were observed with Raman spectroscopy, which showed that Raman modes shifted to higher wavenumbers with increasing doping ratio. This result is indicative of a crystal lattice disorder caused by oxygen vacancies. The wavenumber shifts and relative ratios of the Raman modes were indicators of the composition and oxygen vacancies, respectively, of the U1-yNdyO2-x solid solutions. The oxygen deficiencies of the solid solutions were estimated from the relation between the doping ratio and lattice parameter calculated from X-ray diffraction patterns. Cyclic voltammetry revealed that changes in the Nd content influenced the electrochemical reactivity of hypo-stoichiometric U1-yNdyO2-x, which increased with increasing Nd content. The results of this study provide fundamental data to improve the understanding of spent nuclear fuel.

To efficiently degrade organic pollutants, photocatalysts must be effective under both ultraviolet (UV) radiation and sunlight. We synthesized a series of new metal-organic frameworks by using mild hydrothermal conditions. These frameworks incorporate three distinct bipyridyl ligands: pyrazine (pyr), 4,4 '-bipyridine (bpy), and 1,2-bis(4-pyridyl)ethane (bpe). The resulting compounds are denoted as [Cu(pyz)(H2O)(2)MF6], [Cu(bpy)(2)(H2O)(2)]MF6, and [Cu(bpe)(2)(H2O)(2)]MF6H2O [M = Zr (1, 3, and 5) and Hf (2, 4, and 6)]. All six compounds exhibited a two-dimensional crystal structure comprising infinitely nonintersecting linear chains. Compound 3 achieved 100% degradation of methylene blue (MB) after 8 min under UV irradiation and 100 min under natural sunlight in the presence of H2O2 as the electron acceptor. For compound 5, 100% MB degradation was achieved after 120 min under sunlight and 10 min under UV light. Moreover, reactive radical tests revealed that the dominant species involved in photocatalytic degradation are hydroxyl (center dot OH), superoxide radicals (center dot O-2(-)), and photogenerated holes (h(+)). The photodegradation process followed pseudo-first-order kinetics, with photodegradation rate constants of 0.362 min(-1) (0.039 min(-1)) for 3 and 0.316 min(-1) (0.033 min(-1)) for 5 under UV (sunlight) irradiation. The developed photocatalysts with excellent activity and good recyclability are promising green catalysts for degrading organic pollutants during environmental decontamination.

We provide the material synthesis method, crystal structure information, and characterization of a novel mixed-valent metal oxide KIn0.33IIITe0.67VITe2IVO7, closely related to zirconolite (CaZrTi2O7), a radioactive waste immobilized material, having a 3D framework. The reported metal oxide containing an alkali-metal cation (K+), main-group cation (In3+), tellurate, and tellurite has been synthesized as both single crystals and a pure polycrystalline phase through a hydrothermal synthesis method. Single-crystal X-ray diffraction indicates that KIn0.33Te2.67O7 crystallizing in the orthorhombic space group Cmcm (No. 63) reveals a 3D framework structure with a 1D channel consisting of Te/InO6 octahedra and TeO4 polyhedra. An interesting transition reaction from KIn0.33Te2.67O7 to KIn(TeO3)2 under hydrothermal conditions at 230 °C is discussed.

The overestimation and underestimation of the radioactivity concentration of difficult-to-measure radionuclides can occur during the implementation of the scaling factor (SF) method because of the uncertainties associated with sampling, radiochemical analysis, and application of SFs. Strict regulations ensure that the SF method as an indirect method does not underestimate the radioactivity of nuclear wastes; however, there are no clear regulatory guidelines regarding the overestimation. This has been leading to the misuse of the SF methodology by stakeholders such as waste disposal licensees and regulatory bodies. Previous studies have reported instances of overestimation in statistical implementation of the SF methodology. The analysis of the two most popular linear models of the SF methodology showed that severe overestimation may occur and radioactivity concentration data must be dealt with care. Since one major source of overestimation is the use of minimum detectable activity (MDA) values as true activity values, a comparative study of instrumental techniques that could reduce the MDAs was also conducted. Thermal ionization mass spectrometry was recommended as a suitable candidate for the trace level analysis of long-lived beta-emitters such as iodine-129. Additionally, the current status of the United States and Korea was reviewed from the perspective of overestimation.

Most thickness measurement techniques using X-ray radiation are unsuitable in field processes involving fast-moving organic films. Herein, we propose a Compton scattering X-ray radiation method, which probes the light elements in organic materials, and a new simple, non-destructive, and non-contact calibration-free real-time film thickness measurement technique by setting up a bench-top X-ray thickness measurement system simulating a field process dealing with thin flexible organic films. The use of X-ray fluorescence and Compton scattering X-ray radiation reflectance signals from films in close contact with a roller produced accurate thickness measurements. In a high-thickness range, the contribution of X-ray fluorescence is negligible, whereas that of Compton scattering is negligible in a low-thickness range. X-ray fluorescence and Compton scattering show good correlations with the organic film thickness (R2 = 0.997 and 0.999 for X-ray fluorescence and Compton scattering, respectively, in the thickness range 0–0.5 mm). Although the sensitivity of X-ray fluorescence is approximately 4.6 times higher than that of Compton scattering, Compton scattering signals are useful for thick films (e.g., thicker than ca. 1–5 mm under our present experiment conditions). Thus, successful calibration-free thickness monitoring is possible for fast-moving films, as demonstrated in our experiments.

Novel mixed-valent titanium tellurium oxides, Ti1-xTexTe3O8+x (compound A, B, and C for x = 0, 0.1, and 0.12) were synthesized from TiOSO4 center dot xH(2)SO(4)center dot xH(2)O, TeO2, and H3BO3 using hydrothermal reaction conditions. The crystal structures of the materials were confirmed and refined using single-crystal X-ray diffraction. The compounds have three-dimensional framework structures consisting of TiO6 or Ti/TeO6 octahedra and asymmetric TeO4 polyhedral groups. The cell parameter of compound A, B, and C increased with the increase in the Ti - O bond distance in the TiO6 octahedron and is attributed to the increase in the Te6+ cation doping level. Detailed characterizations of the prepared materials, including Infrared, UV-visible diffuse reflectance, Raman spectra, thermogravimetric analyses, out-of-center distortion, and dipole moment calculations were performed.

Spent nuclear fuel (SNF) is a complex, heterogeneous system in terms of its chemical composition and microstructure because of many fission products. Among them, ε-particles such as Mo, Ru, Ru, Pd, and Tc in SNF, are not included in the crystal lattice of UO2 but are found in boundaries trapped in pores [1]. It is known that ε-particles could affect on structural change and chemical reactivity of UO2. For example εparticles has an important role for oxidation/corrosion of UO2 [2]. In this study, Mo-doped CeO2 was prepared as a simulated spent fuel and studied to understand the effect of ε-particles on physicochemical properties of spent fuel. Scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), and Xray diffraction (XRD) were used to characterize Modoped UO2 and optimize the preparation process of the target sample.

Tae-Hyeong Kim , Dong Woo Lee , Jeongmook Lee a,c , Junghwan Park , Jong-Yun Kim a,c and Sang Ho Lim a,c  Nuclear Chemistry Research Team, Korea Atomic Energy Research Institute, Daejeon, 34057, Republic of Korea Department of Nuclear and Quantum Engineering, Korea Advanced Energy Research Institute, Daejeon, 34141, Republic of Korea Department of Radiochemistry and Nonproliferation, University of Science and Technology, Daejeon, 34113, Republic of Korea Corresponding author: leejm@kaeri.re.kr, slim@kaeri.re.kr

This study explored the crystallographic characterization of zirconium, zirconium-based samples containing minor alloying elements, simulated Zircaloy-4, and simulated ZIRLO at a temperature range of 30–870 °C using in situ high-temperature X-ray diffraction. The results from Pawley refinement demonstrated that the lattice thermal expansion along the a-axis direction is suppressed by the tin element, in contrast to the other minor alloying elements. Moreover, the simulated ZIRLO possesses the enhanced resistance for lattice thermal expansion compared to the simulated Zircaloy-4, indicating that a ZIRLO cladding has a better performance in suppressing the change in the lattice constants under a thermal environment.

a Nuclear Chemistry Research Team, Korea Atomic Energy Research Institute, 111 Daedeok-daero 989 Beon-gil, Yuseong-gu, Daejeon, 34057, Republic of Korea b Department of Radiochemistry & Nuclear Nonproliferation, University of Science & Technology, Gajeong-ro 217, Yuseong-gu, Daejeon, 34113, Republic of Korea c Department of Chemistry, Sogang University, Baekbeom-ro 35, Mapo-gu, Seoul, 04107, Republic of Korea

Dong Woo Lee a, Jeongmook Lee a, Tae-Hyeong Kim a, Junghwan Park a, Jong-Yun Kim a,b and Sang Ho Lim a,b,* aNuclear Chemistry Research Team, Korea Atomic Energy Research Institute, 111, Daedeok-daero 989 Beon-gil, Yuseong-gu, Daejeon, 34057, Republic of Korea bDepartment of Radiochemistry & Nuclear Nonproliferation, University of Science and Technology, Gajeong-ro 217, Yuseong-gu, Daejeon, 34113, Republic of Korea *Corresponding author: slim@kaeri.re.kr

The radionuclide inventory in radioactive waste from nuclear power plants should be determined to secure the safety of final repositories. As an alternative to time-consuming, labor-intensive, and destructive radiochemical analysis, the indirect scaling factor (SF) method has been used to determine the concentrations of difficult-to-measure radionuclides. Despite its long history, the original SF methodology remains almost unchanged and now needs to be improved for advanced SF implementation. Intense public attention and interest have been strongly directed to the reliability of the procedures and data regarding repository safety since the first operation of the low- and intermediate-level radioactive waste disposal facility in Gyeongju, Korea. In this review, statistical methodologies for SF implementation are described and evaluated to achieve reasonable and advanced decision-making. The first part of this review begins with an overview of the current status of the scaling factor method and global experiences, including some specific statistical issues associated with SF implementation. In addition, this review aims to extend the applicability of SF to the characterization of large quantities of waste from the decommissioning of nuclear facilities.

The coverage and temperature dependence of ZIRLO cladding with H 2 O adsorption are studied using synchrotron-based high-resolution photoemission spectroscopy (HRPES). Based on the analytical results of the Zr 3 d , O 1 s , C 1 s , and Sn 3 d HRPES profiles prior to H 2 O adsorption, we determine the surface compositions of O 2− , hydroxyl OH − , chemisorbed H 2 O, zirconium carbide, adventitious carbon, Sn metal, and SnO 2 in ZIRLO. When ZIRLO is exposed to H 2 O molecules, the relative proportion of zirconium metal decreases, whereas that of the total zirconium oxides increases, suggesting the reaction between H 2 O and the zirconium metal in ZIRLO. On annealing a sample with 1000 L H 2 O on ZIRLO at 300 °C, Zr 2 O 3 and ZrO 2 decompose, and oxygen diffuses into the bulk, thereby reducing the oxidation states of zirconium on the surface. Moreover, at this temperature, the excess H 2 O molecules on ZIRLO are thoroughly desorbed and tin element is diffused into the bulk in ZIRLO.

Lattice-doped UO2 pellets have been used as the simulated fuels to investigate the physical and chemical properties of spent nuclear fuel [1-5]. Because of spent nuclear fuel is consisted of mainly UO2 (95%) and minor elements such as radioactive fission products and actinides, lattice-doped UO2 is good model system to confirm influence of those minor elements on physicochemical behavior of UO2. For example, Gddoped UO2 was prepared and investigated to study the influences of trivalent rare earth on structure and corrosion of UO2 [3,4]. Its physical and chemical properties could be useful information to make strategies for long-term management of spent nuclear fuel including deep geological disposal. In this study, Ce-doped UO2 have been investigated the effect of Ce-doping on the UO2 structure and its electrochemical behavior.