The classification of harmful radiation-induced effects into 'stochastic' and 'deterministic' or 'cancer/heritable effects' and 'tissue reactions' has played a significant role in the recommendations of the International Commission on Radiological Protection (ICRP) over a number of decades. More recently, however, there has been a debate regarding the adequacy of the current scheme for classification of health effects with current scientific evidence. While these scientific aspects are discussed in greater detail in a parallel article, we will emphasise the practical importance of the classification itself here. The setting of dose limits is quite different for 'deterministic' and 'stochastic' effects. In the first case, provided reliable data regarding the threshold doses for radiation effects on a particular tissue are available, the dose limit is supposed to avoid harm altogether. With 'stochastic effects', the expected risks at the dose limit are supposed to be 'tolerable'. Below the dose limit, optimisation must be aimed for based on the 'prudent' assumption that the stochastic risks linearly depend on the dose and that there is no threshold. If the distinction between the two kinds of harmful effects is drawn into question, possible consequences for the system of radiological protection need to be considered, especially in the context of its aims as they currently apply, namely, 'to manage and control exposures to ionising radiation so that deterministic effects are prevented, and the risks of stochastic effects are reduced to the extent reasonably achievable'. It may be necessary, moreover, to discuss if and how the terminology used by ICRP (and others), in particular the terms 'deterministic effects' and 'tissue reactions', should continue to be used for the classification of radiation effects.
Predicting the properties of multicomponent molten salts using density functional theory (DFT) remains challenging because the spatial and temporal scales required to evaluate transport properties and phase behavior are computationally prohibitive. In this work, we develop a moment tensor potential trained using a a DFT dataset of NaCl, KCl, NaCl-KCl mixtures, and the NaK alloy, enabling large-scale molecular dynamics simulations across wide ranges of temperatures and compositions. We systematically evaluate the effect of D3 dispersion corrections and apply the resulting potential to predict liquid densities, diffusion coefficients, radial distribution functions, heat capacities, thermal conductivities, and the NaCl-KCl phase diagram. The model successfully reproduces many temperature- and composition-dependent trends. However, systematic deviations in several absolute properties persist, highlighting the importance of experimental validation and calibration. These findings support a hybrid modeling framework in which first-principles-informed machine-learning potentials provide transferable predictive capability and mechanistic insight, while experimental data incorporated during model development or subsequent engineering assessments is necessary to improve quantitative accuracy.
In the current system of radiological protection, radiation effects are classified as either tissue reactions (also known as deterministic effects) or stochastic effects. The objectives of the system are to manage and control exposures to ionising radiation so that harmful tissue reactions are prevented, and the risks of stochastic effects are reduced to the extent reasonably achievable. Thus, the classification of health effects is a very important pillar of the system of radiological protection. In recent years, there has been debate regarding the adequacy of the current scheme for classifying health effects. Recent publications, including those from ICRP, have highlighted the need for a review of the ICRP scheme for health effects classification. This article outlines the basis for the establishment of ICRP Task Group (TG) 123 and the outlined tasks, the key sources of uncertainties for consideration, the agreed approach and timeline to tackle the above tasks, as well as the links with and dependencies on the other ongoing developments to the system being considered by the other ICRP task groups.
Doping UO2 with Cr modifies the material’s microstructure, enhancing its properties and making Cr-doped UO2 a promising candidate as accident-tolerant nuclear fuel (ATF). Numerous studies have examined the oxidation state and localization of Cr in UO2 but often yield inconsistent results, identifying either Cr2+ or Cr3+ as the most stable oxidation state. In the present study, DFT+U is employed to model the incorporation of Cr in the UO2 matrix, providing insights into the oxidation state of Cr in UO2, in relation to the local atomic configurations. In particular, we investigate the Cr_x^3+ U_1-x^4+ O2−0.5x local configuration recently proposed by EPR and XANES experiments, alongside other theoretical configurations. Cr3+ is found to be the most favorable oxidation state in this configuration, agreeing with the most recent experimental data. This work clarifies the controversy over Cr oxidation states and incorporation sites within UO2, offering critical data for developing efficient and safer nuclear fuels. Doping UO2 with Cr enhances its properties and makes it a promising accident-tolerant nuclear fuel, yet the stable oxidation state of Cr in Cr-doped UO2 remains debated. Here, the authors use DFT+U modeling to reveal Cr3+ as the most favorable oxidation state in Cr-doped UO2, aligning with the most recent experimental results.
A new sensitive method to determine polonium-210 (210Po) and lead-210 (210Pb) in a diversity of environmental samples was developed. For fresh and marine waters, Po was pre-concentrated using a titanium (III) hydroxide (Ti(OH)3) co-precipitation. Solid environmental samples were digested with nitric acid (HNO3) and hydrogen peroxide (H2O2). The alpha thin layer source was prepared using CuS micro-precipitation and 210Po was measured by alpha spectrometry. Lead-210 was left to decay for up to a year and indirectly measured via its progeny, 210Po. The chemical recoveries for 210Po and 210Pb were high, 90% and 97%, respectively, for a large variety of samples and a very low minimum detectable activity (MDA) was obtained. The method was validated using standardized solutions and certified reference materials.
