Federal Office for Radiation Protection

Dose assessment in computer tomography (CT) can be performed by Monte Carlo (MC) computer simulation programs. These simulations use realistic computational models of human bodies to estimate organ doses and therefore perform patient-specific dosimetry. In this study, the MC code MCNP 6.2 has been used to calculate the radiation dose for children under a CT scan procedure. For the implementation of the model in the code, an external source subroutine has been developed. An X-ray source with a rectangular centre beam shape was simulated, rotating upwards along the inner surface of a cylinder in a helical manner. To define the key parameters, the user could then specify what kind of CT scanning protocol should be selected. For model validation, MC simulations with a model of the one-year-old male ATOM 704 phantom were done and the results were compared with the outcome of measurements of the phantom using thermoluminescence dosimeters (TLDs) at a GE Brightspeed 16 CT model. A realistic computational model of a 1-year old child was finally used to calculate organ doses. Through the comparison of the data simulated and measured, the implemented CT model was validated and it can now support further investigations of organ doses to children of different body sizes. • A new MCNP 6.2 subroutine was developed and verified to model a helical scanner • Measurements with ATOM 704 paediatric phantom and TLD-100 dosimeters were simulated • Voxelized version of ATOM 704 phantom was created from tomographic images • Organ absorbed dose in ATOM 704 and ICRP 1-year-old reference phantoms was studied

The system of radiological protection (the 'System') developed by the International Commission on Radiological Protection (ICRP) is built on nearly a century of efforts of numerous scientists and practitioners working together internationally. It rests on three enduring pillars: science, ethics, and experience. These pillars support the three fundamental principles that shape radiological protection strategies: justification, optimisation, and application of dose limits. Of note, optimisation of protection must be understood as a flexible and context-sensitive process, which allows identification of the appropriate level of protection, not simply the lowest dose, taking into account economic, societal and environmental factors. The System has proven effective in protecting workers, patients, members of the public, and the environment in all exposure situations. Effects of high doses, where acute injuries to healthy tissue occur, are rarely observed, and mostly due to accidental situations except for unavoidable side effects of radiotherapy. At low doses, the System is supported by application of the linear-no-threshold model. This model enables prudent (that is, carefully considered given existing uncertainties) policy decisions and estimation of risks at low doses by extrapolation from epidemiological data observed at medium and high radiation doses, acknowledging uncertainty without ignoring potential harm.

Abstract A comprehensive multi‐method geophysical strategy is used to investigate two faults in the Northern Upper Rhine Graben. Combining industrial 3D seismic data with our own 2D P‐ and S‐wave seismic, electrical resistivity tomography (ERT) and ground‐penetrating radar (GPR), we created comprehensive subsurface images of the faults. 3D seismic data feature structure from 450 m to 4 km deep, whereas high‐resolution 2D P‐wave data complemented this for depths of 50–600 m. S‐wave seismic imaging revealed disrupted layering and syn‐sedimentary features in the range of 5–250 m depth, whereas ERT measurements further supported the identification of offset horizons and showed syn‐sedimentary activity, particularly down to 10 m depth. GPR results remained ambiguous, though they suggested potential geological features related to fault tectonics. Both faults have varying dip angles and offsets in different stratigraphic units, proving that tectonic movement occurred during sedimentation of the Neogene and Quaternary layers. In general, both faults steepen upwards, forming typically listric shapes. They both offset the base Quaternary by about 35 m. Finally, the very‐near‐surface methods show that the faults extend almost up to the Earth's surface, proving their very recent activity. This project highlights the efficiency of multi‐method geophysical surveys in neotectonic research and seismic risk assessment and emphasizes their role in detailed subsurface analysis. It also contributes to our understanding of potential gas migration along fault zones to the Earth's surface.

The main goal of this study was to enhance the knowledge of the properties of the known octupole rotational band in $^{71}\mathrm{Ge}$, including transition rates, and to investigate whether the band persists to higher spin. An experiment at Florida State University using the $^{62}\mathrm{Ni}(^{14}\mathrm{C},$ $\ensuremath{\alpha}n)$ reaction at 50 MeV was used to produce $^{71}\mathrm{Ge}$ at high spin. An array of ten Compton-suppressed Ge detectors, consisting of three Clover detectors and seven single-crystal detectors, was used to measure the $\ensuremath{\gamma}$ decays in coincidence. An analysis of the resulting coincidence spectra resulted in the placement of 13 additional transitions in the $^{71}\mathrm{Ge}$ level scheme, one of which (1092 keV) extends the octupole band to a $(35/{2}^{\ensuremath{-}})$ state at 8206 keV. However, calculations of the kinematic moment of inertia show that the 1092-keV transition disrupts the rigid rotational pattern and is likely associated with a band crossing, potentially quenching the octupole deformation. Transition strengths inferred from lifetime measurements in the octupole band are not well reproduced by either shell-model calculations using the JUN45 interaction or a semimicroscopic cluster model, while those for the $\ensuremath{\nu}{g}_{9/2}$ band are in good agreement with the corresponding shell-model predictions. Comparisons between the octupole band in $^{71}\mathrm{Ge}$ and negative-parity bands based on ${3}^{\ensuremath{-}}$ octupole states in some neighboring even-even nuclei show both similarities and differences. Systematic trends within the $\ensuremath{\nu}{g}_{9/2}$ bands among odd-$A$ Ge isotopes point to increased collectivity near $N=40$.

The health impacts of the radioactive Radon are well-documented by the World Health Organization (WHO) and numerous studies. Geogenic Radon Potential (GRP) refers to the natural production of Radon by the Earth, independent of anthropogenic influences. GRP has been a focal point of research aimed at understanding the factors influencing radon variability and its spatial distribution. However, the limited availability of systematic soil-gas radon concentration measurements, along with other constraints, often leads to coarse-resolution modeling of GRP. With the availability of adequate and quality data, regional studies can be promising in investigating these influencing factors, and modelling of GRP hazards at finer spatial scales. This study uses GRP survey data provided by the Hessian Agency for Nature Conservation, Environment and Geology (HLNUG) to develop machine learning models for predicting the spatial distribution of GRP in the state of Hessen, Germany, and to produce a high-resolution GRP hazard map. The models employed include Random Forest Regressor (RF), Support Vector Regressor (SVR), Gradient Boosting Regressor (GBR), and Multi-Layer Perceptron Regressor (MLPR). The dataset comprises 1,509 GRP sampling points for an area of about 21.000 km², and 37 potential predictors related to geology, soil characteristics, and climatic variables—key factors known to influence radon levels. Sequential Feature Selection (SFS) and a 5-fold spatial cross-validation strategy were employed to mitigate autocorrelation effects and enhance model generalization. Model performance was evaluated using multiple metrics and compared against ground-truth values and local geology. Results revealed that the RF and GBR models outperformed others, achieving R² scores of 0.69 and 0.65 on the validation dataset, respectively, while the SVR and MLPR models underperformed. Predicted GRP values ranged from 8.9 to 178.2 for RF and 1.7 to 268.4 for GBR. Geological and soil properties emerged as the dominant predictors of GRP variability in Hessen, with predicted maps highlighting a strong dependence on local geological features. High-risk areas were effectively identified by the RF model. The study also highlights the need for additional measurements in data-scarce regions and the exploration of hybrid physics-based models that integrate domain-specific knowledge into spatial predictions.

Purpose High-linear energy transfer (LET) radiation is generally thought to be more biologically effective in various tissues than low-LET radiation, but whether this also applies to the circulatory system remains unclear. We therefore reviewed biological studies about the effects of high-LET radiation on the circulatory system. Conclusions We identified 76 relevant papers (24 in vitro, 2 ex vivo, 51 in vivo, one overlapping). In vitro studies used human, bovine, porcine or chick vascular endothelial cells or cardiomyocytes, while ex vivo studies used porcine hearts. In vivo studies used mice, rats, rabbits, dogs or pigs. The types of high-LET radiation used were neutrons, α particles, heavy ions and negative pions. Most studies used a single dose, although some investigated fractionation effects. Twenty-one studies estimated the relative biological effectiveness (RBE) that ranged from 0.1 to 130, depending on radiation quality and endpoint. A meta-analysis of 6 in vitro and 8 in vivo studies (selected based on the feasibility of estimating the RBE and its uncertainty) suggested an RBE of 6.69 (95% confidence intervals (CI): 2.51, 10.88) for in vitro studies and 1.14 (95% CI: 0.91, 1.37) for in vivo studies. The meta-analysis of these 14 studies yielded an RBE of 2.88 (95% CI: 1.52, 4.25). This suggests that high-LET radiation is only slightly more effective than low-LET radiation, although substantial inter-study heterogeneity complicates interpretation. Therapeutic effects have also been reported in disease models. Further research is needed to better understand the effects on the cardiovascular system and to improve radiation protection.

The International Commission on Radiological Protection (ICRP) Task Group 120 (TG120) is developing ICRP recommendations for radiological protection for a wide range of radiation accidents and malicious events, complementing those given in ICRP Publication 146 (2020) for large nuclear accidents. The scope includes accidents involving criticalities, operating faults, and fires and explosions in nuclear facilities, inadvertent damage to sealed radiation sources, as well as malicious events, such as sabotage of nuclear facilities or materials, use of radiological dispersal devices, the contamination of food and drinking water supplies, and the deployment of nuclear weapons. A template has been designed to collate relevant information on a wide range of case studies and hypothetical malicious scenarios to ensure that the recommendations developed are broadly applicable and comprehensive. For all scenarios, a graded approach to protection is being taken, accepting that specific guidance may be required for some distinctive aspects, for example, protection during times of armed conflict. This paper provides an overview of the scenarios and scope of the work of TG120, including some of the radiological and non-radiological impacts of radiation emergencies, along the response and recovery timeline.

Purpose In cases of radiological or nuclear events, biological dosimetry enables decisions whether an individual was exposed to ionizing radiation and the estimation of the dose. Several statistical methods are used to assess uncertainties. The stringency of the applied method has an impact on the lowest dose that can be detected. To obtain reliable and comparable results, it is crucial to harmonize the applied statistical methods. Materials and methods The decision threshold and detection limit of the statistical methods were derived for variable cell numbers. The coverage of the 95% confidence intervals as well as the false-positive and false-negative rates of the methods were compared based on simulations. The evaluated methods included a graphical method, the propagation of errors and a Bayesian method. Results The minimum resolvable doses, the doses at the detection limit and the coverage were relatively variable between the compared methods. The Bayesian method showed the best coverage, lowest resolvable doses and had false-positive rates close to 5%. The graphical method with the combination of two 83% confidence intervals also showed promising results. The other methods were either too conservative or underestimated the uncertainties for some doses or cell numbers. Conclusions The assessment of the lower dose limits is a central part of biological dosimetry and the applied statistical methods have a strong influence on the interpretation of the results. Simulations enable comparisons between methods and provide important information for the harmonization and standardization of the uncertainty assessment.