• Energy Research

Radiological risk affects the quality of the environment in buildings since population and workers can be potentially exposed to high levels of radiation. Radon gas emanating from both subsoil and building materials represents the most important source of radiation exposure for people. This study investigates the sustainability concept of a small rural village of Ischia Island, named Ciglio, in relation to radiation protection legislation concerning the radiological risk for workers. Radon activity concentration was measured in typical green-tuff dwellings and in water samples collected from a local waterfall E-Perm devices. Moreover, for green tuff as building material, the radon emanation coefficient was calculated by gamma spectroscopy. The results highlight the importance of performing environmental radon monitoring and investigating the radon content of building materials, especially in geographical areas characterized by traditional use of typical stones for constructions. In conclusion, the sustainable development of rural buildings is possible if the radiological risk for inhabitants and workers is assessed in line with the national radiation protection legislation.

Chromosome aberrations induced by X-rays and alpha-particles (LET = 177 keV/microns) were observed at the first mitosis in C3H 10T1/2 cells released from density-inhibited cultures. X-radiation induced more chromosome exchanges than breaks (71% vs 27% of total aberrations), while a predominance of breaks (63%) was observed after alpha-irradiation. A linear-quadratic dose-response relationship was obtained for X-rays, while that for alpha-particles was linear. The RBE values for total aberration induction (ranging from 5.1 at low doses to 4.4 at high doses) were very similar to the RBE for cell killing (from 5.2 to 4.3). The RBE for dicentric induction (approximately 2) was much lower than the RBE for the induction of both breaks (from 7 to 6) and interstitial deletions (from 9 to 7). This behaviour supports the hypothesis that chromosome deletions play a major role in the malignant transformation of 10T1/2 cells. A high correlation between cell killing and number of acentric fragments per cell was found. The number of acentrics/cell at the mean lethal dose was about 1.4. This number was reduced to 1.0 when asymmetrical interchanges, which generally result in very small deletions, were subtracted from acentrics. It could be hypothesized that very small deletions could not impair cell survival. However, an alternative hypothesis related to the aneuploid state of C3H 10T1/2 cells can be formulated. Robertsonian translocations were also observed at the first mitosis. The dose-response curve of these translocations appears to be very similar to the dose-response curve for induction of sister chromatid exchanges (observed at the second mitosis) reported by other authors studying the same cell line. This similarity could indicate a general mechanism of action of radiation on the process of recombination of genetic material.

We measured fluence and fragmentation of high-energy (1 or 5 A GeV) 56Fe ions accelerated at the Alternating Gradient Synchrotron or at the NASA Space Radiation Laboratory (Brookhaven National Laboratory, NY, USA) using solid-state CR-39 nuclear track detectors. Different targets (polyethylene, PMMA, C, Al, Pb) were used to produce a large spectrum of charged fragments. CR-39 plastics were exposed both in front and behind the shielding block (thickness ranging from 5 to 30 g/cm2) at a normal incidence and low fluence. The radiation dose deposited by surviving Fe ions and charged fragments was measured behind the shield using an ionization chamber. The distribution of the measured track size was exploited to distinguish the primary 56Fe ions tracks from the lighter fragments. Measurements of projectile's fluence in front of the shield were used to determine the dose per incident particle behind the block. Simultaneous measurements of primary 56Fe ion tracks in front and behind the shield were used to evaluate the fraction of surviving iron projectiles and the total charge-changing fragmentation cross-section. These physical measurements will be used to characterize the beam used in parallel biological experiments.

Astronauts' radiation exposure limits are based on experimental and epidemiological data obtained on Earth. It is assumed that radiation sensitivity remains the same in the extraterrestrial space. However, human radiosensitivity is dependent upon the response of the hematopoietic tissue to the radiation insult. It is well known that the immune system is affected by microgravity. We have developed a mathematical model of radiation-induced myelopoiesis which includes the effect of microgravity on bone marrow kinetics. It is assumed that cellular radiosensitivity is not modified by the space environment, but repopulation rates of stem and stromal cells are reduced as a function of time in weightlessness. A realistic model of the space radiation environment, including the HZE component, is used to simulate the radiation damage. A dedicated computer code was written and applied to solar particle events and to the mission to Mars. The results suggest that altered myelopoiesis and lymphopoiesis in microgravity might increase human radiosensitivity in space.

AbstractRadionuclides are widely known to produce serious problem when released and dispersed in the environment because they can contaminate humans through food chains, affecting metabolic process and causing health diseases to the population. A large amount of radionuclides is produced as waste during the process of nuclear facility operation, maintenance, and decommissioning. Wastewater contains many radioactivemetal ions. During the last three decades, after Chernobyl accident and then that of Fukushima, several techniques have been developed for the removal of radionuclides from the environment and from wastewater aiming of inertization. One of the most recent techniques, and in continuous progress, is the radionuclides removal by adsorption using natural and/or synthesized materials having high retention capacity and being resistant to radiation. The most used type of material, cheap and easy-to-find, is zeolite due to its high ion exchange capacity, adsorption efficiency and abundance. This work concerns a preliminary study on zeolites identification for the removal of radionuclides in wastewater samples from the fuel storage of the former nuclear power plant of Latina, Italy. The activity concentration of the radionuclides in the samples was investigated by γ- and α-spectrometry. The wastewater samples contain the radionuclides 137Cs, 60Co and 241Am, and the best solution for their removal was discovered to be the zeolite A. The obtained results can be enlarged to all former Italian nuclear facilities.

We have recently reported the kinetics of chromosome rejoining and exchange formation in human lymphocytes exposed to gamma rays using the techniques of fluorescence in situ hybridization (FISH) and premature chromosome condensation (PCC). In this paper, we have extended previous measurements to cells exposed to charged particles. Our goal was to determine differences in chromatin break rejoining and misrejoining after exposure to low- and high-linear energy transfer (LET) radiation. Cells were irradiated with hydrogen, neon, carbon or iron ions in the LET range 0.3-140 keV/microm and were incubated at 37 degrees C for various times after exposure. Little difference was observed in the yield of early prematurely condensed chromosome breaks for the different ions. The kinetics of break rejoining was exponential for all ions and had similar time constants, but the residual level of unrejoined breaks after prolonged incubation was higher for high-LET radiation. The kinetics of exchange formation was also similar for the different ions, but the yield of chromosome interchanges measured soon after exposure was higher for high-LET particles, suggesting that a higher fraction of DNA breaks are misrejoined quickly. On the other hand, the rate of formation of complete exchanges was slightly lower for densely ionizing radiation. The ratios between the yields of different types of aberrations observed at 10 h postirradiation in prematurely condensed chromosome preparations were dependent on LET. We found significant differences between the yields of aberrations measured in interphase (after repair) and metaphase for densely ionizing radiation. This difference might be caused by prolonged mitotic delay and/or interphase death. Overall, the results point out significant differences between low- and high-LET radiation for the formation of chromosome aberrations.

We report results for chromosomal aberrations in human peripheral blood lymphocytes after they were exposed to high-energy iron ions with or without shielding at the HIMAC, AGS and NSRL accelerators. Isolated lymphocytes were exposed to iron ions with energies between 200 and 5000 MeV/nucleon in the 0.1-1-Gy dose range. Shielding materials consisted of polyethylene, lucite (PMMA), carbon, aluminum and lead, with mass thickness ranging from 2 to 30 g/cm2. After exposure, lymphocytes were stimulated to grow in vitro, and chromosomes were prematurely condensed using a phosphatase inhibitor (calyculin A). Aberrations were scored using FISH painting. The yield of total interchromosomal exchanges (including dicentrics, translocations and complex rearrangements) increased linearly with dose or fluence in the range studied. Shielding decreased the effectiveness per unit dose of iron ions. The highest RBE value was measured with the 1 GeV/nucleon iron-ion beam at NSRL. However, the RBE for the induction of aberrations apparently is not well correlated with the mean LET. When shielding thickness was increased, the frequency of aberrations per particle incident on the shield increased for the 500 MeV/nucleon ions and decreased for the 1 GeV/nucleon ions. Maximum variation at equal mass thickness was obtained with light materials (polyethylene, carbon or PMMA). Variations in the yield of chromosomal aberrations per iron particle incident on the shield follow variations in the dose per incident particle behind the shield but can be modified by the different RBE of the mixed radiation field produced by nuclear fragmentation. The results suggest that shielding design models should be benchmarked using both physics and biological data.