Radiation and Nuclear Safety Authority

<strong class="journal-contentHeaderColor">Abstract.</strong> Spatially resolved estimates of road transport emissions are fundamental for tackling challenges of air pollution and greenhouse gas emissions. Emission estimates at 0.05&deg; x 0.1&deg; resolution are provided in the widely used CAMS-REG regional European emissions inventory. For the road transport sector, several improvement opportunities were identified: Firstly (1) an underestimation of ca. 35 % of NOx emissions in comparison to 8 independent urban inventories; secondly (2), artefacts in the spatial distribution in Eastern European non-EU countries; thirdly (3), the necessity of labour-intense downscaling methodologies to create high-resolution urban inventories from the fixed resolution dataset. To overcome these, emissions for all road links in the domain (n=59,710,490) were estimated using gap-filled activity data (AADT) from OpenStreetMap and OpenTransportMap. Gap filling was performed with random forest models trained on land-use and road information data. Model performance was <em>R</em>²: 0.63&ndash;0.74 and MAE(AADT): 1570&ndash;2028, with better performance for larger roads. Up-to-date emission factors were applied on road links using a novel maximum-speed&ndash;based classification. To generate the CAMS-REG v8.1 inventory, the resulting spatial distribution was used as a proxy map, together with national totals. The new dataset lowered the difference-to-city inventories to 19 % for absolute NOx emissions, and can be flexibly gridded to high resolutions. Median increase in urban emission share is 24 % compared to national totals, and non-EU cities see large increases (e.g. Istanbul, +197 %; St. Petersburg, +288 %) in attributed emissions due to the updated spatial distribution. Two case studies (London and Milan) show an increased spatial correlation, from <em>R</em>² &asymp; 0.3 using CAMS-REG v4.2 to <em>R</em>² &asymp; 0.6, with CAMS-REG v8.1 against the local inventory. Vector and gridded versions of the emission dataset and spatial distribution are available at <a href="https://doi.org/10.5281/zenodo.15688723" target="_blank" rel="noopener">https://doi.org/10.5281/zenodo.15688723</a> (Hohenberger et al. (2025)).

The Passive Gamma Emission Tomography (PGET) instrument, authorized by the International Atomic Energy Agency (IAEA) for verification of spent nuclear fuel, aims to reconstruct 2D cross-sectional images of spent fuel assemblies (SFAs), identify missing or present fuel pins, and quantify fuel pin activities. Although the first two objectives are reliably achieved, accurate determination of fuel pin activities remains a challenge due to intense self-shielding and scattering effects. We have developed a linear inverse approach that addresses these effects and demonstrated superior image quality and identification accuracy in simulation studies. This approach frames the image reconstruction process as an inverse problem, relying on a physics-based forward model of the PGET system. We improved our forward model by incorporating collimator septal penetration and detector scattering effects. The enhanced forward model enables near-real-time sinogram simulation and system matrix calculation, which is> 100,000 times faster than 3D Monte Carlo simulations. The model was validated through simulations of VVER-1000 and VVER-440 SFA, and a relative difference of 3.7% in counts was achieved between MCNP and our forward model. Based on this enhanced model, we successfully reconstructed images from the simulated data, identified 100% of the fuel pins, and achieved an average uncertainty of 2.3% in activity quantification. We applied the reconstruction method to measured data of VVER-440 SFAs, successfully imaging all the pins, including the innermost ones, and identifying the water channel within the SFA. The high accuracy and low computational cost of our forward model demonstrate its potential for real-world inspection scenarios and enable future algorithm development.

This paper presents deterministic approaches chosen to predict the effect of stress corrosion cracking, creep, pitting corrosion and general corrosion on the lifetime of copper in disposal conditions of spent fuel. The interest in copper in Finland and Sweden is because of the plans to use it as a corrosion shield for the cast iron canister containing high activity nuclear waste. Our approach is based on assessing whether the occurrence of different types of corrosion can be excluded in the disposal conditions. If this is not the case, we shall recommend the maximum corrosion penetration to be predicted on the basis of experimental results and to assess whether this is below an acceptable level. We have applied this approach to show that the occurrence of stress corrosion cracking in the presence of nitrite ions in the disposal conditions can very likely be excluded. In addition, we have shown that assessing the occurrence of localised corrosion due to bicarbonate ions and the occurrence of general corrosion in the disposal conditions requires further experimental work.

In June 2020, observations of anthropogenic radionuclides in Estonia, Finland, and Sweden that were not related to any acknowledged environmental release led to a comprehensive investigation on the source and cause of the unusual emissions. Several of the observed radionuclides were on the list of Comprehensive Nuclear-Test-Ban Treaty (CTBT) relevant radionuclides as an indicator of a potential nuclear test, and warranted detailed investigation. While analysis of aerosol samples coupled with Atmospheric Transport and Dispersion Modelling (ATDM) is a standard approach for environmental particulate releases, several new techniques were employed to better characterize the samples that allowed for useful inferences to be made. These inferences were crucial in forming the ultimate hypothesis for determining the facility type and location of the release.

The Cohort Study of Mobile Phone Use and Health (COSMOS) has repeatedly collected self-reported and operator-recorded data on mobile phone use. Assessing health effects using self-reported information is prone to measurement error, but operator data were available prospectively for only part of the study population and did not cover past mobile phone use. To optimize the available data and reduce bias, we evaluated different statistical approaches for constructing mobile phone exposure histories within COSMOS. We evaluated and compared the performance of 4 regression calibration (RC) methods (simple, direct, inverse, and generalized additive model for location, shape, and scale), complete-case analysis, and multiple imputation in a simulation study with a binary health outcome. We used self-reported and operator-recorded mobile phone call data collected at baseline (2007-2012) from participants in Denmark, Finland, the Netherlands, Sweden, and the United Kingdom. Parameter estimates obtained using simple, direct, and inverse RC methods were associated with less bias and lower mean squared error than those obtained with complete-case analysis or multiple imputation. We showed that RC methods resulted in more accurate estimation of the relationship between mobile phone use and health outcomes by combining self-reported data with objective operator-recorded data available for a subset of participants.

Cone beam computed tomography (CBCT) may provide essential additional image guidance to endovascular abdominal aneurysm repair (EVAR) operations but also significant radiation exposure to patients if scans are not carefully optimized. The purpose of our study was to define the image quality requirements for intraoperative EVAR CBCT imaging and to optimize the CBCT exposure parameters accordingly. A Multi-Energy CT phantom simulating a large patient was used by replacing the central phantom cylinder with a custom water-filled insert including an EVAR stent. Different exposure parameters covering a range of radiation qualities and dose levels were used to define the optimal image quality level regarding stent graft evaluation (compressed, bent, or collapsed). The radiation dose was measured with a calibrated air kerma-area product (KAP) meter and organ doses were calculated based on Monte Carlo simulations and a mathematical patient model. Based on the results, updated exposure parameters with the highest mean energy and lowest dose level available were recommended. With the updated protocol, the radiation exposure could be significantly decreased. The KAP value decreased from 9720 μGy·m2 to 440 μGy·m2 and reference point air kerma from 351 mGy to 16 mGy (a reduction of 96%) and organ doses of the organs in the irradiated region decreased on an average 91%. The new protocol resulted in acceptable clinical image quality based on testing with clinical cases.

Measurements of the natural radiation background, specifically in the upper troposphere and low stratosphere, are important in order to compare and eventually inter-calibrate different experimental set-ups, as well as to provide a reliable basis for improving the existing models related to the environmental radiation in the Earth's atmosphere. Here, we report results from a new zero-pressure stratospheric balloon flight in the frame of the HEMERA-2 mission, obtained by measurements performed with a small portable device, (MDU)-1 Liulin. We derived the altitude profile of the atmospheric radiation in the Arctic region, namely in between Esrange Kiruna, Sweden and Rovaniemi, Finland. The preliminary analysis shows a good agreement between the measurements and Oulu models for atmospheric ionization and exposure to radiation.

The purpose of this study was to acquire up-to-date information on nuclear medicine treatments in Europe and on the implementation of the requirements of the Basic Safety Standards Directive in HERCA Heads of the European Radiological Protection Competent Authorities (HERCAs) member states. An electronic survey was distributed to competent authorities of 32 HERCA member states. The questionnaire addressed 33 explicitly considered treatments using 13 different radionuclides, and for each treatment, a similar set of questions was included. Questions covered the use of treatments, hospitalisation of patients and radioactive waste management related to therapeutic nuclear medicine involving other radionuclides than the well-known 131I. The survey also covered justification of treatments, individual treatment planning, involvement of a medical physics expert (MPE) and radiation protection instructions given to the patient at the time of release. Responses were obtained from 20 HERCA countries. All of these countries used Na[131I]I for benign thyroid diseases and thyroid ablation of adults. 223RaCl2 (Xofigo®) for bone metastases, 177Lu-somatostatin analogues for neuroendocrine tumours and 177Lu-labelled PSMA for castration resistant prostate cancer (PC) and PC-metastases were used in 90%, 65% and 55% of countries, respectively. Only a few countries had specific criteria for hospitalisation and waste management for new therapeutic nuclear medicine. Regulatory requirements for justification of new therapeutic nuclear medicine were in place in almost all countries. Individual treatment planning was required for all therapies in 55% and for some therapies in 28% of the responding countries. Implementation of the requirement for MPEs to be closely involved in nuclear medicine practices varied to a great extend among countries. Almost all responding countries answered that some radiation protection instructions existed for patients released after treatment with radionuclides other than 131I treatment, however only few countries had developed specific guidelines in the field.

Mortality was studied in a cohort of 4831 men from Estonia who participated in the environmental cleanup of the radioactively contaminated areas around Chernobyl in 1986–1991. Their mortality in 1986–2020 was compared with the mortality in the Estonian male population. A total of 1503 deaths were registered among the 4812 traced men. The all-cause standardized mortality ratio (SMR) was 1.04 (95% CI 0.99–1.09). All-cancer mortality was elevated (SMR 1.16, 95% CI 1.03–1.28). Radiation-related cancers were in excess (SMR 1.20, 95% CI 1.03–1.36); however, the excesses could be attributed to tobacco and alcohol consumption. For smoking-related cancers, the SMR was 1.20 (95% CI 1.06–1.35) and for alcohol-related cancers the SMR was 1.56 (95% CI 1.26–1.86). Adjusted relative risks (ARR) of all-cause mortality were increased among workers who stayed in the Chernobyl area ≥ 92 days (ARR 1.20, 95% CI 1.08–1.34), were of non-Estonian ethnicity (ARR 1.33, 95% CI 1.19–1.47) or had lower (basic or less) education (ARR 1.63, 95% CI 1.45–1.83). Suicide mortality was increased (SMR 1.31, 95% CI 1.05–1.56), most notably among men with lower education (ARR 2.24, 95% CI 1.42–3.53). Our findings provide additional evidence that unhealthy behaviors such as alcohol and smoking play an important role in shaping cancer mortality patterns among Estonian Chernobyl cleanup workers. The excess number of suicides suggests long-term psychiatric and substance use problems tied to Chernobyl-related stressors, i.e., the psychosocial impact was greater than any direct carcinogenic effect of low-dose radiation.