Amer Al-Qaaod

The production, attenuation, and absorption of secondary cosmic rays (SCR) are influenced by atmospheric parameters such as air pressure and temperature. To reliably correlate SCR flux measurements with atmospheric ionization driven by energetic particle precipitation, these dependencies must be quantified. Monte Carlo simulations enable detailed modeling of stochastic interactions between cosmic radiation and atmospheric components, providing a robust framework for analyzing underlying physical processes and predicting SCR flux under varying atmospheric conditions. This study introduces a simulation model based on the Monte Carlo N‐Particle (MCNP) code, integrating atmospheric profiles from radiosonde data to model the production, absorption, and attenuation of SCR. The model's accuracy was validated through comparisons with the PHITS (Particle and Heavy Ion Transport code System)‐based Analytical Radiation Model in the Atmosphere (PARMA) and experimental ground‐based muon count measurements. It was subsequently used to investigate the dependence of muon flux on atmospheric pressure and temperature up to 20 km altitude. Results reveal a complex relationship between muon flux and atmospheric variables, particularly in the troposphere and lower stratosphere, where pressure correlations and barometric coefficients exhibit both positive and negative values depending on altitude. The model provides a valuable tool for investigating interactions between SCR and climate variables such as humidity and cloud coverage. Furthermore, the model can be coupled with dosimetry models to assess the biological effects of SCR, including deoxyribonucleic acid (DNA) damage, genomic instability, cellular dysfunction, and long‐term health risks such as cancer.

Combined radiation exposures—pairings of ionizing and non-ionizing radiation—are increasingly relevant in medical, spaceflight, and environmental contexts. This systematic review evaluates their radiobiological effects and therapeutic applications, focusing on synergistic interactions and underlying biological mechanisms. A comprehensive search of PubMed, Google Scholar, Semantic Scholar, bioRxiv, and Europe PMC identified studies published from the 1960s through 2025. Eligible studies assessed biological responses to different radiation types applied either simultaneously or within 24 h, with minor exceptions. A total of 172 studies were included and categorized into radiobiological, therapeutic, and space radiation domains. Due to the predominance of mechanistic research, no formal risk-of-bias tool was applied; methodological limitations were assessed qualitatively. Findings were synthesized narratively by radiation type and domain. Synergistic and additive effects were frequently observed, with responses influenced by dose, sequence, radiation type, and DNA repair dynamics. Therapeutic combinations often enhanced efficacy, while space radiation studies revealed multifaceted biological damage. This review provides a consolidated reference for advancing research and applications involving combined radiation exposures, emphasizing the need for mechanistic insight and standardized protocols in therapy, radiation protection, and spaceflight. This study was funded by project 21GRD02 BIOSPHERE (European Partnership on Metrology, Horizon Europe) and reported per PRISMA 2020 guidelines; no protocol was registered.

Combined radiation exposures—pairings of ionizing and non-ionizing radiation—are increasingly relevant in medical, spaceflight, and environmental contexts. This systematic review evaluates their radiobiological effects and therapeutic applications, focusing on synergistic interactions and underlying biological mechanisms. A comprehensive search of PubMed, Google Scholar, Semantic Scholar, bioRxiv, and Europe PMC identified studies published from the 1960s through 2025. Eligible studies assessed biological responses to different radiation types applied either simultaneously or within 24 hours, with minor exceptions. A total of 172 studies were included and categorized into radiobiological, therapeutic, and space radiation domains. Due to the predominance of mechanistic research, no formal risk-of-bias tool was applied; methodological limitations were assessed qualitatively. Findings were synthesized narratively by radiation type and domain. Synergistic and additive effects were frequently observed, with responses influenced by dose, sequence, radiation type, and DNA repair dynamics. Therapeutic combinations often enhanced efficacy, while space radiation studies revealed multifaceted biological damage. This review provides a consolidated reference for advancing research and applications involving combined radiation exposures, emphasizing the need for mechanistic insight and standardized protocols in therapy, radiation protection, and spaceflight. Funded by project 21GRD02 BIOSPHERE (European Partnership on Metrology, Horizon Europe). Reported per PRISMA 2020 guidelines; no protocol registered.

The ozone layer in the Earth’s atmosphere filters solar radiation and limits the unwanted effects on humans. A depletion of this ozone shield would permit hazardous levels of UV solar radiation, especially in the UVB range, to bombard Earth’s surface, resulting in potentially significant effects on human health. The concern for these adverse effects intensifies if we consider that the UVB solar radiation is combined with secondary cosmic radiation (SCR) components, such as protons and muons, as well as terrestrial gamma rays. This research aims to delve into the intricate interplay between cosmic and solar radiation on earth at the cellular level, focusing on their synergistic effects on human cell biology. Through a multidisciplinary approach integrating radiobiology and physics, we aim to explore key aspects of biological responses, including cell viability, DNA damage, stress gene expression, and finally, genomic instability. To assess the impact of the combined exposure, normal i.e., non-malignant human cells (skin fibroblasts, keratinocytes, monocytes, and lymphocytes) were exposed to high-energy protons or gamma rays in combination with UVB. Cellular molecular and cytogenetic biomarkers of radiation exposure, such as DNA damage (γH2AΧ histone protein and dicentric chromosomes), as well as the expression pattern of various stress genes, were analyzed. In parallel, the MTS reduction and lactate dehydrogenase assays were used as indicators of cell viability, proliferation, and cytotoxicity. Results reveal remaining DNA damage for the co-exposed samples compared to samples exposed to only one type of radiation in all types of cells, accompanied by increased genomic instability and distinct stress gene expression patterns detected at 24–48 h post-exposure. Understanding the impact of combined radiation exposures is crucial for assessing the health risks posed to humans if the ozone layer is partially depleted, with structural and functional damages inflicted by combined cosmic and UVB exposure.

In 2020, the ICRU released a new report which includes the re-definition of the operational quantities used in radiation protection and new conversion coefficients from physical quantities to operational radiation protection quantities. An assessment of the ambient and personal dose conversion coefficients for the reference neutron fields of radionuclide sources at PTB is necessary based on these new definitions. In this work, a numerical estimation of the conversion coefficients of moderated and unmoderated ²⁵²Cf and ²⁴¹Am-Be neutron sources based on ICRU57 and ICRU95 reports and using spectrum data available in the ISO 8529-1 standard and at PTB are discussed. Two numerical approaches are used for this estimation to ensure the reliability of the calculated values: a direct calculation using MCNP6, and cubic interpolation of conversion coefficients datasets written in Python. The results show large differences between the spectrum-averaged operational quantities for the current and new conversion coefficients of up to 23%. The choice of spectrum data affects conversion coefficient values by 6–8%.

Knowledge of the neutron spectra of reference fields is very important for calibration purposes. This paper presents new calculations of the neutron spectra and dosimetric parameters of a D₂O moderated ²⁵²Cf source assembly used to produce a neutron reference field at the Physikalisch-Technische Bundeanstalt (PTB), based on recent ²⁵²Cf fission neutron spectrum data and conversion coefficients for operational radiation protection units recommended by the International Commission on Radiological Protection (ICRP) report 57. Neutron fluence and dose calculations were carried out using a detailed simulation model of the source assembly implemented using MCNP6 and the cross-section data library ENDF/B-VIII.0. The PTB moderator was compared with the International Organization for Standardization, ISO 8529 model and to previous calculations done at PTB. The results show differences to the previous calculations performed at PTB of the order of 5% and a slight discrepancy with the ISO 8529 moderator model regarding the values of the operational quantities.

The neutron reference field produced by a heavy-water moderated ²⁵²Cf source is used at PTB for calibrating neutron-measuring devices. Knowledge of the precise neutron spectrum is very important for the investigation of operational radiation protection quantities. Recently, new fission spectrum data of ²⁵²Cf has been proposed based on the latest nuclear data library version. At PTB, earlier calculations for the D₂O moderated ²⁵²Cf neutron source were carried out more than 20 years ago, thus updated and more detailed calculations are required. In this paper, a detailed simulation model of the PTB moderated ²⁵²Cf source assembly has been prepared and investigated using new spectral data and two different Monte Carlo transport codes MCNP6.1 and PHITS3.22, with ENDF/BVIII.0, ENDF/B-VII.1, ENDF/B-V, and ENDL85 evaluated nuclear data libraries. The results show that the evaluated nuclear data libraries influence the calculated operational quantities by (3-5) %. The dosimetric quantities calculated with the PHITS code and the ENDF/B-VII.1 data library agree well with the MCNP6 results.

In this paper, the feasibility of high-level radioactive waste transmutation in accelerator driven system sub-critical reactor assembly, has been studied for two zone's model and with three different core configurations. The inner zone has a fast neutron spectrum and the outer one has a thermal neutron spectrum. The subcritical core is coupled with external neutron source of energy 14 MeV (D-T source). The effects of high level waste isotopes sample (238Pu, 239Pu, 240Pu, 241Pu, 242Pu, 241Am, 243Am, 244Cm, and 245Cm) distribution on the neutron spectrum and burnup performance in the inner zone have been investigated and discussed, by proposed three core configurations non-uniform, uniform, and spiral. The burnup calculations have been performed for one-year operation cycle for all the all proposed models. This work shows that one can effectively transmute most of the actual minor actinides isotopes in the inner fast spectrum zone of the proposed system, with optimal distribution of these isotopes.