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According to NASA's plans, a human travel to the Moon is planned by the end of 2025 with the Artemis II mission, and humans should land on the Moon again in 2026. Exposure to space radiation is one of the main risks for the crew members; while for these short missions the doses from galactic cosmic rays would be relatively low, the possible occurrence of an intense solar particle event (SPE) represents a major concern, especially considering that in 2025 the Sun activity will be at its peak. Quantifying the amount and the effects of such exposure is therefore crucial, to identify shielding conditions that allow respecting the dose limits established by the various space agencies. By exploiting an interface between the BIANCA biophysical model and the FLUKA Monte Carlo radiation transport code, in this work we implemented a male and a female voxel phantom and we calculated absorbed doses and Gy-Eq doses in the various tissues/organs, as well as effective doses, following exposure to the August 1972 SPE, the most intense event of the modern era. The calculations were performed respect the organ dose limits for 30 d missions. A detailed comparison between male and female doses was then carried out, also considering that the Artemis II crew will include a woman. The results showed that female doses tend to be higher than male doses, especially with light shielding. This should be taken into account in mission design, also considering that, in a typical lunar mission, up to 15% of time may be spent in extra-vehicular activities, and thus with light shielding. More generally, this work outlines the importance of performing separate calculations for male and female astronauts when dealing with radiation doses and effects., (Creative Commons Attribution license.)

An alternative approach that is particularly suitable for the radiation health risk assessment (HRA) of astronauts is presented. The quantity, Radiation Attributed Decrease of Survival (RADS), representing the cumulative decrease in the unknown survival curve at a certain attained age, due to the radiation exposure at an earlier age, forms the basis for this alternative approach. Results are provided for all solid cancer plus leukemia incidence RADS from estimated doses from theoretical radiation exposures accumulated during long-term missions to the Moon or Mars. For example, it is shown that a 1000-day Mars exploration mission with a hypothetical mission effective dose of 1.07 Sv at typical astronaut ages around 40 years old, will result in the probability of surviving free of all types of solid cancer and leukemia until retirement age (65 years) being reduced by 4.2% (95% CI 3.2; 5.3) for males and 5.8% (95% CI 4.8; 7.0) for females. RADS dose–responses are given, for the outcomes for incidence of all solid cancer, leukemia, lung and female breast cancer. Results showing how RADS varies with age at exposure, attained age and other factors are also presented. The advantages of this alternative approach, over currently applied methodologies for the long-term radiation protection of astronauts after mission exposures, are presented with example calculations applicable to European astronaut occupational HRA. Some tentative suggestions for new types of occupational risk limits for space missions are given while acknowledging that the setting of astronaut radiation-related risk limits will ultimately be decided by the Space Agencies. Suggestions are provided for further work which builds on and extends this new HRA approach, e.g., by eventually including non-cancer effects and detailed space dosimetry. [ABSTRACT FROM AUTHOR]

In addition to the continuous exposure to cosmic rays, astronauts in space are occasionally exposed to Solar Particle Events (SPE), which involve less energetic particles but can deliver much higher doses. The latter can exceed several Gy in a few hours for the most intense SPEs, for which non-stochastic effects are thus a major concern. To identify adequate shielding conditions that would allow respecting the dose limits established by the various space agencies, the absorbed dose in the considered organ/tissue must be multiplied by the corresponding Relative Biological Effectiveness (RBE), which is a complex quantity depending on several factors including particle type and energy, considered biological effect, level of effect (and thus absorbed dose), etc. While in several studies only the particle-type dependence of RBE is taken into account, in this work we developed and applied a new approach where, thanks to an interface between the FLUKA Monte Carlo transport code and the BIANCA biophysical model, the RBE dependence on particle energy and absorbed dose was also considered. Furthermore, we included in the considered SPE spectra primary particles heavier than protons, which in many studies are neglected. This approach was then applied to the October 2003 SPE (the most intense SPE of solar cycle 23, also known as "Halloween event") and the January 2005 event, which was characterized by a lower fluence but a harder spectrum, i.e., with higher-energy particles. The calculation outcomes were then discussed and compared with the current dose limits established for skin and blood forming organs in case of 30-days missions. This work showed that the BIANCA model, if interfaced to a radiation transport code, can be used to calculate the RBE values associated to Solar Particle Events. More generally, this work emphasizes the importance of taking into account the RBE dependence on particle energy and dose when calculating equivalent doses., Competing Interests: Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Committee on Space Research (COSPAR). Published by Elsevier B.V. All rights reserved.)

Biomedical applications at high-energy particle accelerators have always been an important section of the applied nuclear physics research. Several new facilities are now under constructions or undergoing major upgrades. While the main goal of these facilities is often basic research in nuclear physics, they acknowledge the importance of including biomedical research programs and of interacting with other medical accelerator facilities providing patient treatments. To harmonize the programs, avoid duplications, and foster collaboration and synergism, the International Biophysics Collaboration is providing a platform to several accelerator centers with interest in biomedical research. In this paper, we summarize the programs of various facilities in the running, upgrade, or construction phase.

Space radiation is acknowledged as one of the main health risks for human exploration of the Solar system. Solar particle events (SPE) and the galactic cosmic radiation (GCR) can cause significant early and late morbidity, and damage mission critical microelectronics. Systematic studies of the interaction of energetic heavy ions with biological and electronic systems are typically performed at high-energy particle accelerators with a small subset of ions and energies in an independent and serialized way. This simplification can lead to inaccurate estimations of the harmful radiation effects of the full space radiation environment on man and machine. To mitigate these limitations, NASA has developed an irradiation system at the Brookhaven National Laboratory able to simulate the full GCR spectrum. ESA is also investing in ground-based space radiation studies in Europe, using the current and future facilities at GSI/FAIR in Darmstadt (Germany). We describe here an advanced hybrid active-passive space radiation simulation system to simulate GCR or SPE spectra. A predefined set of different monoenergetic 56Fe beams will be fired on specially designed beam modulators consisting of filigree periodic structures. Their thickness, composition and geometry per used primary beam energy are optimized via 1D-transport calculations in such a way that the superposition of the produced radiation fields at the target position closely simulate the GCR in different scenarios. The highly complex modulators will be built using state-of-the-art manufacturing techniques like 3D-printing and precision casting. A Monte Carlo simulation of the spectrum produced in this setup is reported.

Accelerator-based measurements and model calculations have been used to study the heavy ion radiation transport properties of materials in use on the International Space Station (ISS). Samples of the ISS aluminum outer hull were augmented with various configurations of internal wall material and polyethylene. The materials were bombarded with high energy Fe ions characteristic of a s ignificant part of the Galactic Cosmic Ray (GCR) heavy ion spectrum. Transmitted primary ions and charged fragments produced in nuclear collisions in the materials were measured near the beam axis, and a model was used to extrapolate from the data to lower beam energies and to a lighter ion. For the materials and ions studied, at incident particle energies from 1037 MeV/nucleon down to at least 600 MeV/nucleon, nuclear fragmentation reduces the average dose and dose equivalent per incident ion. At energies below 400 MeV/nucleon, the calculation predicts that as material is added, increased ionization energy loss produces increases in some dosimetric quantities. These limited results suggest that the addition of modest amounts of polyethylene or similar material to the interior of the ISS will reduce the dose to ISS crews from space radiation; however the radiation transport properties of ISS materials should be evaluated with a realistic space radiation field.

Abstract Applied nuclear physics is an essential part of the research activity at many particle accelerators. New, large accelerator facilities are currently under construction in Europe, Asia, and USA. These machines will be able to produce radioactive ion beams, and to increase the intensity and the energy of the heavy ions well beyond the limits currently available at the therapy or research facilities. The upcoming facilities open new opportunities for research in biomedical applications that require these special properties, such as particle radiography, radioactive beam imaging, ultra-high dose rates and new ions for therapy. Moreover, space radiation research and materials science can successfully exploit these new centers. The new facilities can pave the way to many future applications of nuclear physics for the benefit of the society. In this paper we will summarize the current status of applied sciences at high-energy accelerators, describe the characteristics of some of the machines under construction (FAIR, NICA, RAON, ELI) and discuss the new opportunities offered by these facilities in applied sciences. [ABSTRACT FROM AUTHOR]

Abstract High-energy charged particles in space pose a severe threat to the health and safety of astronauts. This is especially the case in deep space exploration owing to the absence of magnetic field protection as present in low Earth orbit (LEO) manned spaceflight. This has necessitated the investigation and development of effective space radiation protection materials and methods. Manned space missions produce a significant amount of trash, which can be compressed by a heat melt compactor (HMC) to reduce space utilization. The trash would also be sterilized during the compaction process and the extracted water can be recycled. The processed trash can potentially be used for space radiation protection, with the benefit of reduced launch load. In this study, the Monte Carlo method was used to acquire information about the primary and secondary radiation particles that emerged from different radiation shields made from an HMC-processed model trash of a manned space mission, as well as those made from aluminum and water, which are common, and currently used space radiation protection materials. The types and energies of the considered incident radiation particles were based on space radiation environment spectra. A comparison of the space radiation protection capacities of the different shields revealed that HMC-processed trash was superior to aluminum and water. Processed trash thus promises to be a practicable alternative to water for the construction of radiation emergency areas for future deep space missions as the mission proceeds and the water is consumed. Highlights • The particles and energies are choosing according to the space radiation environment. • Both emergent energies and information of secondary emergent particles are analyzed. • Space radiation protection capacity of HMC-processed trash is superior to Al and H 2 O. • HMC-processed trash can be used to protect against SPEs without added launch load. [ABSTRACT FROM AUTHOR]

Radiation detectors based on diamond are attractive for radiation protection applications in space and aviation due to their radiation hardness, large breakdown voltage, fast signal collection, and low noise, thus representing a valid alternative to silicon-based detector devices. In this paper, we study the tissue equivalence of diamond in proton and \alpha particle radiation fields typical of galactic cosmic rays and solar particle events. We determine a method to convert microdosimetric response from diamond to water by means of Geant4 simulations. Results are presented showing that a simple geometrical scaling factor (\sim 0.32) of linear dimensions is adequate to convert experimentally obtained microdosimetric energy deposition spectra in diamond to equivalent microdosimetric energy deposition spectra in water. [ABSTRACT FROM PUBLISHER]

Abstract: Analyses of the epidemiological data on the Japanese A-bomb survivors, who were exposed to γ-rays and neutrons, provide most current information on the dose–response of radiation-induced cancer. Since the dose span of main interest is usually between 0 and 1Gy, for radiation protection purposes, the analysis of the A-bomb survivors is often focused on this range. However, estimates of cancer risk for doses larger than 1Gy are becoming more important for long-term manned space missions. Therefore in this work, emphasis is placed on doses larger than 1Gy with respect to radiation-induced solid cancer and leukemia mortality. The present analysis of the A-bomb survivors data was extended by including two extra high-dose categories and applying organ-averaged dose instead of the colon-weighted dose. In addition, since there are some recent indications for a high neutron dose contribution, the data were fitted separately for three different values for the relative biological effectiveness (RBE) of the neutrons (10, 35 and 100) and a variable RBE as a function of dose. The data were fitted using a linear and a linear-exponential dose–response relationship using a dose and dose-rate effectiveness factor (DDREF) of both one and two. The work presented here implies that the use of organ-averaged dose, a dose-dependent neutron RBE and the bending-over of the dose–response relationship for radiation-induced cancer could result in a reduction of radiation risk by around 50% above 1Gy. This could impact radiation risk estimates for space crews on long-term mission above 500days who might be exposed to doses above 1Gy. The consequence of using a DDREF of one instead of two increases cancer risk by about 40% and would therefore balance the risk decrease described above. [Copyright &y& Elsevier]

With 5–7 month long duration missions at 51.6° inclination in Low Earth Orbit, the ionizing radiation levels to which International Space Station (ISS) crewmembers are exposed will be the highest planned occupational exposures in the world. Even with the expectation that regulatory dose limits will not be exceeded during a single tour of duty aboard the ISS, the “as low as reasonably achievable” (ALARA) precept requires that radiological risks be minimized when possible through a dose optimization process. Judicious placement of efficient shielding materials in locations where crewmembers sleep, rest, or work is an important means for implementing ALARA for spaceflight. Polyethylene (CnHn) is a relatively inexpensive, stable, and, with a low atomic number, an effective shielding material that has been certified for use aboard the ISS. Several designs for placement of slabs or walls of polyethylene have been evaluated for radiation exposure reduction in the Crew Quarters (CQ) of the Zvezda (Star) Service Module. Optimization of shield designs relies on accurate characterization of the expected primary and secondary particle environment and modeling of the predicted radiobiological responses of critical organs and tissues. Results of the studies shown herein indicate that 20% or more reduction in equivalent dose to the CQ occupant is achievable. These results suggest that shielding design and risk analysis are necessary measures for reducing long-term radiological risks to ISS inhabitants and for meeting legal ALARA requirements. Verification of shield concepts requires results from specific designs to be compared with onboard dosimetry. [Copyright &y& Elsevier]

The exposure to galactic cosmic radiation (GCR) is a major health concern for astronauts. Crewed missions with durations of several years are foreseen in future space exploration projects such as permanent habitats on the Moon and flights to Mars. This aim requires elaborate space radiation shielding concepts and a proper understanding of the underlying radiation physics and radiobiology as well as their interplay. In the present work, Monte Carlo simulations to assess the performance of different materials (polyethylene, aluminum, Moon regolith) as thick shields (up to 400 g/cm 2 ) against GCR were conducted using the FLUKA code. Absorbed dose, dose equivalent and the mean quality factor at 1 cm depth in the ICRU sphere as a function of shielding thickness were calculated in a spherical shell configuration for both solar minimum and solar maximum GCR conditions. Large differences were observed in the performance of the studied materials as thick GCR shields. Special attention was paid to the build-up and moderation of secondary neutrons. A method to reduce the neutron contributions to ambient dose equivalent by means of a two-layer shielding combination is proposed. The present study can be useful for considerations on thick shielding of Moon or Mars habitats built from local regolith., (Copyright © 2022. Published by Elsevier B.V.)

For precision cancer radiotherapy, high linear energy transfer (LET) particle irradiation offers a substantial advantage over photon-based irradiation. In contrast to the sparse deposition of low-density energy by χ- or γ-rays, particle irradiation causes focal DNA damage through high-density energy deposition along the particle tracks. This is characterized by the formation of multiple damage sites, comprising localized clustered patterns of DNA single- and double-strand breaks as well as base damage. These clustered DNA lesions are key determinants of the enhanced relative biological effectiveness (RBE) of energetic nuclei. However, the search for a fingerprint of particle exposure remains open, while the mechanisms underlying the induction of chromothripsis-like chromosomal rearrangements by high-LET radiation (resembling chromothripsis in tumors) await to be elucidated. In this work, we investigate the transformation of clustered DNA lesions into chromosome fragmentation, as indicated by the induction and post-irradiation repair of chromosomal damage under the dynamics of premature chromosome condensation in G0 human lymphocytes. Specifically, this study provides, for the first time, experimental evidence that particle irradiation induces localized shattering of targeted chromosome domains. Yields of chromosome fragments and shattered domains are compared with those generated by γ-rays; and the RBE values obtained are up to 28.6 for α-particles (92 keV/μm), 10.5 for C-ions (295 keV/μm), and 4.9 for protons (28.5 keV/μm). Furthermore, we test the hypothesis that particle radiation-induced persistent clustered DNA lesions and chromatin decompaction at damage sites evolve into localized chromosome shattering by subsequent chromatin condensation in a single catastrophic event—posing a critical risk for random rejoining, chromothripsis, and carcinogenesis. Consistent with this hypothesis, our results highlight the potential use of shattered chromosome domains as a fingerprint of high-LET exposure, while conforming to the new model we propose for the mechanistic origin of chromothripsis-like rearrangements. [ABSTRACT FROM AUTHOR]

The risk assessment quantities called lifetime attributable risk (LAR) and risk of exposure-induced cancer (REIC) are used to calculate the cumulative cancer incidence risks for astronauts, attributable to radiation exposure accumulated during long term lunar and Mars missions. These risk quantities are based on the most recently published epidemiological data on the Life Span Study (LSS) of Japanese A-bomb survivors, who were exposed to γ-rays and neutrons. In order to analyze the impact of a different neutron RBE on the risk quantities, a model for the neutron relative biological effectiveness (RBE) relative to gammas in the LSS is developed based on an older dataset with less follow-up time. Since both risk quantities are based on uncertain quantities, such as survival curves, and REIC includes deterministic radiation induced non-cancer mortality risks, modelled with data based on the general population, the risks for astronauts may not be optimally estimated. The suitability of these risk assessment measures for the use of cancer risk calculation for astronauts is discussed. The work presented here shows that the use of a higher neutron RBE than the value of 10, traditionally used in the LSS risk models, can reduce the risks up to almost 50%. Additionally, including an excess absolute risk (EAR) baseline scaling also increases the risks by between 0.4% and 8.1% for the space missions considered in this study. Using just an EAR model instead of an equally weighted EAR and excess relative risk (ERR) model can decrease the cumulative risks for the considered missions by between 0.4% and 4.1% if no EAR baseline scaling is applied. If EAR baseline scaling is included, the calculated risks with the EAR- and the mixed model, as well as the risks calculated with just the ERR model are almost identical and only small differences in the uncertainties are visible., (Copyright © 2020. Published by Elsevier B.V.)

Biomedical applications at high-energy particle accelerators have always been an important section of the applied nuclear physics research. Several new facilities are now under constructions or undergoing major upgrades. While the main goal of these facilities is often basic research in nuclear physics, they acknowledge the importance of including biomedical research programs and of interacting with other medical accelerator facilities providing patient treatments. To harmonize the programs, avoid duplications, and foster collaboration and synergism, the International Biophysics Collaboration is providing a platform to several accelerator centers with interest in biomedical research. In this paper, we summarize the programs of various facilities in the running, upgrade, or construction phase., Competing Interests: Conflict of Interest: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

As manned spaceflights beyond low Earth orbit are in the agenda of Space Agencies, the concerns related to space radiation exposure of the crew are still without conclusive solutions. The risk of long-term detrimental health effects needs to be kept below acceptable limits, and emergency countermeasures must be planned to avoid the short-term consequences of exposure to high particle fluxes during hardly predictable solar events. Space habitat shielding cannot be the ultimate solution: the increasing complexity of future missions will require astronauts to protect themselves in low-shielded areas, e.g. during emergency operations. Personal radiation shielding is promising, particularly if using available resources for multi-functional shielding devices. In this work we report on all steps from the conception, design, manufacturing, to the final test on board the International Space Station (ISS) of the first prototype of a water-filled garment for emergency radiation shielding against solar particle events. The garment has a good shielding potential and comfort level. On-board water is used for filling and then recycled without waste. The successful outcome of this experiment represents an important breakthrough in space radiation shielding, opening to the development of similarly conceived devices and their use in interplanetary missions as the one to Mars., (Copyright © 2018 The Committee on Space Research (COSPAR). Published by Elsevier Ltd. All rights reserved.)

During interplanetary missions, astronauts are exposed to mixed types of ionizing radiation. The low 'flux' of the high atomic number and high energy (HZE) radiations relative to the higher 'flux' of low linear energy transfer (LET) protons makes it highly probable that for any given cell in the body, proton events will precede any HZE event. Whereas progress has been made in our understanding of the biological effects of low-LET protons and high-LET HZE particles, the interplay between the biochemical processes modulated by these radiations is unclear. Here we show that exposure of normal human fibroblasts to a low mean absorbed dose of 20 cGy of 0.05 or 1-GeV protons (LET ∼ 1.25 or 0.2 keV/μm, respectively) protects the irradiated cells (P < 0.0001) against chromosomal damage induced by a subsequent exposure to a mean absorbed dose of 50 cGy from 1 GeV/u iron ions (LET ∼ 151 keV/μm). Surprisingly, unirradiated (i.e. bystander) cells with which the proton-irradiated cells were co-cultured were also significantly protected from the DNA-damaging effects of the challenge dose. The mitigating effect persisted for at least 24 h. These results highlight the interactions of biological effects due to direct cellular traversal by radiation with those due to bystander effects in cell populations exposed to mixed radiation fields. They show that protective adaptive responses can spread from cells targeted by low-LET space radiation to bystander cells in their vicinity. The findings are relevant to understanding the health hazards of space travel., (© The Author 2015. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.)