Gamma Irradiation Conditions Research Articles

Suitability of aromatic polyurethanes for use in nuclear applications

Plastic bags are used to facilitate the storage and transport of nuclear materials. In case the storage container becomes damaged, these bags act as a protection barrier against possible contamination. Polyvinyl chloride (PVC) is a polymer commonly used in such applications, but unfortunately, it contributes to the corrosion of the metal container due to HCl evolution. Thus, this work evaluated aging effects on chemical and thermo-mechanical properties of aromatic polyurethanes with the intent to find a replacement for PVC. Aromatic poly(ether)urethanes were aged for up to 21 months under combined gamma irradiation and thermal treatment conditions. A few samples were also placed into actual nuclear storage containers and aged for a similar time period. Experimental techniques, such as FT-IR, NMR, mass spectrometry, TGA, DSC, and tensile tests were employed to characterize two types of polyurethanes, one with and another one without a flame-retardant additive. Our unique aging approach shows that these aromatic polyurethanes are well placed to substitute PVC bags and thus, avoid corrosion of storage metal containers used by the nuclear industry.

Formation of methyl iodide in sodium iodide solutions in the presence of acetic acid and formic acid under gamma irradiation conditions

Formation of methyl iodide in sodium iodide solutions in the presence of acetic acid and formic acid under gamma irradiation conditions

Effect of gamma irradiation on GaN lateral Schottky barrier diodes

The effect of gamma irradiation on GaN lateral Schottky barrier diodes (SBDs) has been investigated. Six gamma irradiation conditions were carried out, namely 100/500 k rad, 1 M rad, 100/500 k rad and 100°C, and 1 M rad and 100°C. All the irradiated devices have a similar parameter variation tendency. There is no change for turn-on voltage. The on-state resistance is reduced from 5.32~5.53 Ω to 5.10~5.26 Ω, while the reverse leakage at -100 V is increased from 3.53~4.99 μA to 4.13~5.79 μA. The interface information extracted is improved slightly, demonstrating the anode/GaN interface is improved, and the passivation/AlGaN interface may be degraded. The slight variation of irradiated performance demonstrates that the GaN lateral SBDs are hardly affected by gamma irradiation.

Mutational effects of chronic gamma radiation throughout the life cycle of Arabidopsis thaliana: Insight into radiosensitivity in the reproductive stage

Organisms living on Earth have always been exposed to natural sources of ionizing radiation, but following recent nuclear disasters, these background levels have often increased regionally due to the addition of man-made sources of radiation. To assess the mutational effects of ubiquitously present radiation on plants, we performed a whole-genome resequencing analysis of mutations induced by chronic irradiation throughout the life cycle of Arabidopsis thaliana grown under controlled conditions. We obtained resequencing data from 36 second generation post-mutagenesis (M2) progeny derived from 12 first generation (M1) lines grown under gamma-irradiation conditions, ranging from 0.0 to 2.0 Gray per day (Gy/day), to identify de novo mutations, including single base substitutions (SBSs) and small insertions/deletions (INDELs). The relationship between de novo mutation frequency and radiation dose rate from 0.0 to 2.0 Gy/day was assessed by statistical modeling. The increase in de novo mutations in response to irradiation dose fit the negative binomial model, which accounted for the high variability of mutation frequency observed. Among the different types of mutations, SBSs were more prevalent than INDELs, and deletions were more frequent than insertions. Furthermore, we observed that the mutational effects of chronic radiation were greater during the reproductive stage. These results will provide valuable insights into practical strategies for analyzing mutational effects in wild plants growing in environments with various mutagens.

High-Performance and Radiation-Hardened Solution-Processed ZrLaO Gate Dielectrics for Large-Area Applications.

Radiation hardness is important for electronics operating in harsh radiation environments such as outer space and nuclear energy industries. In this work, radiation-hardened solution-processed ZrLaO thin films are demonstrated. The radiation effects on solution-processed ZrLaO thin films and InOx/ZrLaO thin-film transistors (TFTs) were systemically investigated. The Zr0.9La0.1Oy thin films demonstrated excellent radiation hardness with negligible roughness, composition, electrical property, and bias-stress stability degradation after radiation exposure. The metal-oxide-semiconductor capacitors (MOSCAPs) based on Zr0.9La0.1Oy gate dielectrics exhibited an ultralow flat band-voltage (VFB) sensitivity of 0.11 mV/krad and 0.19 mV/krad under low dose and high dose gamma irradiation conditions, respectively. The low dose condition had a 103 krad (SiO2) total dose and a 0.12 rad/s low dose rate, whereas the high dose condition had a 580 krad total dose and a 278 rad/s high dose rate. Furthermore, InOx/Zr0.9La0.1Oy thin-film transistors (TFTs) exhibited a large Ion/Ioff of 2 × 106, a small subthreshold swing (SS) of 0.11 V/dec, a small interface trap density (Dit) of 1 × 1012 cm-2, and a 0.16 V threshold shift (ΔVTH) under 3600 s positive bias-stress (PBS). InOx/Zr0.9La0.1Oy TFT-based resistor-loaded inverters demonstrated complete swing behavior, a static output gain of 13.3 under 4 V VDD, and an ∼9% radiation-induced degradation. Through separate investigation of the radiation-induced degradation on the semiconductor layer and dielectric layer of TFTs, it was found that radiation exposure mainly generated oxygen vacancies (Vo) and increased electron concentration among gate oxide. Nevertheless, the radiation-induced TFT instability was mainly related to the semiconductor layer degradation, which could be possibly suppressed by back-channel passivation. The demonstrated results indicate that solution-processed ZrLaO is a high-potential candidate for large-area electronics and circuits applied in harsh radiation environments. In addition, the detailed investigation of radiation-induced degradation on solution-processed high-k dielectrics in this work provided clear inspiration for developing novel flexible rad-hard dielectrics.

High dose gamma irradiation effects on properties of active layers in ZnO thin film transistors

Solution-based bottom-gate zinc oxide thin film transistors (TFTs) were fabricated, remaining functional and demonstrating stability under extreme gamma irradiation conditions. Unpassivated TFTs were fabricated on samples with different number of ZnO layers grown via sol-gel spin coating technique. The devices were characterized before and after exposure to a cumulative dose of 220 MRad (air) of gamma irradiation. Atomic force microscopy (AFM), x-ray diffraction (XRD), and photoluminescence (PL) were employed to characterize the TFT active layers. Thickness measurements and optical images suggest the removal of the channel surface, conceivably due to cumulative effect of displacement damage near the ZnO surface. Device electrical characteristics were extracted from current–voltage measurements. The impact of displacement damage on the degradation/enhancement of device characteristics as a consequence of surface/bulk effects is discussed.

Brown rice based weaning food treated with gamma irradiation evaluated during storage

The present study was carried out to assess the effect of gamma irradiation (0, 2, 4, 6, 8 and 10 kGy) and subsequent ambient storage conditions (12 months, 32 ± 2 °C) on physcico-chemical, antinutritional, functional, microbiological and sensory properties of brown rice based weaning food. The weaning food was prepared from brown rice, mungbean, apples, and walnuts. The amino acid contents of weaning food showed no clear trend of change with respect to increasing irradiation dose. Rehydration ratio (3.60–1.30%) and swelling power (2.59–1.08 g/g) of irradiated weaning food showed a significant decrease with increased dosage and storage time. The solubility index (1.32–6.18%) significantly increased with increased irradiation doses and storage period. Increased irradiation doses significantly decreased browning index (0.611–0.0.998), and moisture content (8.82–7.85%) while as storage period significantly increased browning index (0.611–0.998) and moisture content (7.85–8.82%) of weaning food. Irradiation doses and storage period showed a non-significant effect on the L* and a*colour values whereas, a significant effect was observed for b* values. Antioxidant activity, total phenol, β-carotene, iron, and calcium contents were improved with irradiation doses and decreased with storage periods. Total plate count, sensory characteristics, phytate, and oxalate contents decreased with an increase in irradiation dose.

Improvement of ionizing gamma irradiation tolerance of Chlorella vulgaris by pretreatment with polyethylene glycol

Purpose: To evaluate the effects of polyethylene glycol (PEG) 6000 pretreatment on growth and physiological responses of eukaryotic microalga Chlorella vulgaris exposed to ionizing irradiation.Materials and methods: The microalgal cells pretreated with different PEG concentrations (0, 5, 10 and 20%) and then exposed to 300 Gray gamma irradiation at a dose rate of 0.5 Gy s−1. The various growth and physiological parameters including algal growth, cell size, the degree of electrolyte leakage (EL) and lipid peroxidation, the content of pigments and proline and the activity of antioxidant enzymes under gamma-free or 300 Gray gamma irradiation conditions were examined.Results: The results showed that PEG stimulated a higher growth and cell size under both stress-free and gamma-stress conditions. The maximum growth and cell size was reported when the algae was pretreated with 10% PEG. A relative increase of catalase activity was observed in all samples after exposing to gamma irradiation. However, the highest value was recorded for the gamma-radiated algae pretreated with 10% PEG. In the absence of PEG, gamma irradiation induced a significant reduction in ascorbate peroxidase activity, but with PEG pretreatment, the enzyme activity remained constant or even increased after gamma irradiation. On the other hand, although gamma irradiation stress generally suppressed the activity of superoxide dismutase in all cells, pretreating the algae with PEG could diminish this suppressing effect at all applied concentrations. Compared to the PEG-free controls, a lower rate of chlorophylls and membrane integrity loss was shown in the PEG-treated algae when exposed to gamma stress. Total carotenoid content in PEG-treated algae was also similar under both gamma-free and gamma-radiated conditions. A PEG-independent increase in proline accumulation was reported under gamma-irradiation treatment.Conclusions: Overall, the results suggested that PEG pretreatment could improve gamma-irradiation tolerance in C. vulgaris probably by stimulating a range of enzymatic and non-enzymatic reactive oxygen species scavenging systems. The microalgae may also consume PEG to break down and use it as an alternative source of carbon during stress which should be further studied in detail.

Effect of gamma radiation dose on the performance of negative-index fiber Bragg gratings

The effect of gamma radiation dose (∼1 MGy) on the performance of negative-index fiber Bragg grating (FBG) formed by prolong UV laser exposure (type-IIa grating) and prolong thermal exposure (thermally regenerated grating) is presented for the first time. It is observed that for both negative-index gratings, the radiation-induced shift in Bragg wavelength and temperature sensitivity were less than 37 pm and 0.06 pm / ° C, respectively. The performance of negative-index grating is also compared with that of positive-index grating (type-I) under the same gamma irradiation conditions. It is observed that variation in Bragg wavelength, reflection intensity, and temperature sensitivity was lower in negative-index gratings compared to that of positive-index grating. The effect of radiation is analyzed in terms of “radiation-optic coefficient” for all FBGs. The different behavior of the FBG is linked with a different mechanism responsible for the formation of negative- and positive-index FBGs.

Formation of CH3I in a NaI and methyl alkyl ketone solution under gamma irradiation conditions

We investigated the effects of concentrations of NaI and methyl alkyl ketone on the formation of methyl iodide under gamma irradiation conditions. Without irradiation, the formation of methyl iodide does not occur. For the formation of methyl iodide, the solution pH should be brought to lower than 6 by radiolytic decomposition of ketones and air. At a pH below 6, the iodide was oxidized into iodine, allowing for the formation of CH3I from the reaction of iodine and the CH3 radical. When the concentrations of NaI and methyl alkyl ketone were similar, the concentration of methyl iodide was generally at its highest, and as the gamma dose increased, the concentration of methyl iodide increased.

FT-IR investigations on effect of high doses of gamma radiation-induced damage to polystyrene and mechanism of formation of radiolysis products.

The present article focuses on the influence of gamma irradiation and post-irradiation storage conditions on FT-IR spectra of 1mm thick polystyrene irradiated with 51, 77 and 129kGy. The increase in amplitude corresponding to 3600, 3400 and 2100cm- 1 stretching frequencies clearly showing the formation of O-H and C=O bonds (~ 25%). On prolonged storage (2160h) in the dark, there is an increase in O-H group (~ 28%). The electron cloud facilitates the formation of hydroxyl group in irradiated polystyrene. The post-irradiation treatment with heat conversely showed a reduction of O-H, C-H and C=O (9-16%) groups due to radical-radical recombination at higher temperatures and light intensities. This investigation finds its applications in memory devices, optical sensors, radiation dosimetry and different space and radiation facilities.

Ionizing Radiations (Alpha, Beta, Gamma) Effects on CdS / P-Si Heterojunction Solar Cell for Electrical and Optical Properties

The effect of ionizing radiations (Alpha, Beta, Gamma) in CdS/p-Si heterojunction solar cells are discussed in this paper. The short-circuit current density parameters before Gamma irradiation conditions have been improved up to 35 mA/cm2 and after Gamma irradiation was 30 mA/cm2. The open circuit voltage before Gamma irradiation was 0.59 and 0.565 V after Gamma irradiation. The limitations of these devices were discussed by investigating the dependence of electrical and efficiency parameters in function of radiation time. The efficiency of the cell before radiation was equal to (11.2%) whenever, after the impact of both Alpha, Beta, and Gamma was follows, 4.7, 4.9, and 5.1% respectively. The fill factor before and after Gamma irradiation was 54.5 and 53 %. Studying and analyzing the cells using the I-V, with the change of time rate of Gamma radiation played a critical role in reducing the efficiency of solar cells. The campaign was carried out with different doses of a series of solar cells by exposing them to different time. The deterioration parameters of CdS/p-Si solar cells by Gamma radiation led to strongly supports the results of minority carrier lifetime, which clearly showed diminishing minority carrier lifetime with increasing radiation dose.

Effect of gamma irradiation and fiber surface treatment on the properties of bagasse fiber-reinforced waste polypropylene composites

ABSTRACTBiocomposites of waste polypropylene (WPP) with bagasse fiber as reinforcing component can be readily prepared based on waste management application. Bagasse was subjected to chemical treatments using sodium hydroxide (NaOH) and vinyl triethoxysilane to modify the fiber properties. Scanning electron microscope and Fourier-transform infrared spectroscopy were used to elucidate fiber modification after treatments. Compounding of WPP at various ratios of bagasse was produced by melt mixing. Treated and untreated fiber composites were investigated under conditions of gamma irradiation at 20 kGy. In general behavior, at different fiber loadings, treated biocomposites have better properties than untreated one and fiber treated with silane is the best. Furthermore, treated biocomposites represented more biodegradability under soil than untreated one. The results of mechanical properties showed that the as-prepared fiber composites have superior irradiation-resistant properties.

Effect of Gamma Irradiation on 2-Acetyl-1-pyrroline Content, GABA Content and Volatile Compounds of Germinated Rice (Thai Upland Rice).

Aroma intensity in rice is related to the level of 2-acetyl-1-pyrroline (2AP). The accumulation of 2AP in rice has been synthesized via l-proline metabolism by inactive betaine aldehyde dehydrogenase enzyme (BADH2), which activates 2AP accumulation. Meanwhile, active BADH2 inhibits 2AP accumulation but activates γ-aminobutyric acid (GABA) accumulation. The improvement of 2AP content in rice has been reported under certain conditions, such as high salinity, water treatment, and reduction of high intensity solar exposure. In this study, we conducted the effects of gamma irradiation on 2AP content, GABA content and volatile compounds of germinated rice (Thai upland rice). Our results showed that the GABA content was highest when rice seeds germinated within a 24-h. The 2AP content of irradiated rice (germinated within a 24-h duration) was higher than non-irradiated rice for all gamma doses, particularly at 20 Gy, which showed a 23-fold higher level of 2AP than non-irradiated rice. On the other hand, the reduction of the GABA content of irradiated rice was caused by an increase in the gamma dose. At 300 Gy, irradiated rice had a GABA content approximately 2.6-fold lower than non-irradiated rice. Moreover, we observed that a reduction of volatile compounds occurred when increasing gamma dose. However, some volatile compounds appeared in the irradiated rice at gamma doses of 60 Gy, 80 Gy, 100 Gy and 300 Gy. Furthermore, we observed that the level of Octanal, which is the compound most related to aroma intensity, of irradiated rice was stronger than that of non-irradiated rice. Our results demonstrate for the first time that 2AP and GABA contents are sensitive to gamma irradiation conditions. Moreover, the results indicate that the gamma irradiation technique can be used to improve the aroma intensity of rice.

The effect of gamma-irradiation conditions on the immunogenicity of whole-inactivated Influenza A virus vaccine

Gamma-irradiation, particularly an irradiation dose of 50kGy, has been utilised widely to sterilise highly pathogenic agents such as Ebola, Marburg Virus, and Avian Influenza H5N1. We have reported previously that intranasal vaccination with a gamma-irradiated Influenza A virus vaccine (γ-Flu) results in cross-protective immunity. Considering the possible inclusion of highly pathogenic Influenza strains in future clinical development of γ-Flu, an irradiation dose of 50kGy may be used to enhance vaccine safety beyond the internationally accepted Sterility Assurance Level (SAL). Thus, we investigated the effect of irradiation conditions, including high irradiation doses, on the immunogenicity of γ-Flu. Our data confirm that irradiation at low temperatures (using dry-ice) is associated with reduced damage to viral structure compared with irradiation at room temperature. In addition, a single intranasal vaccination with γ-Flu irradiated on dry-ice with either 25 or 50kGy induced seroconversion and provided complete protection against lethal Influenza A challenge. Considering that low temperature is expected to reduce the protein damage associated with exposure to high irradiation doses, we titrated the vaccine dose to verify the efficacy of 50kGy γ-Flu. Our data demonstrate that exposure to 50kGy on dry-ice is associated with limited effect on vaccine immunogenicity, apparent only when using very low vaccine doses. Overall, our data highlight the immunogenicity of influenza virus irradiated at 50kGy for induction of high titre antibody and cytotoxic T-cell responses. This suggests these conditions are suitable for development of γ-Flu vaccines based on highly pathogenic Influenza A viruses.

Exposure of luminous marine bacteria to low-dose gamma-radiation

The study addresses biological effects of low-dose gamma-radiation. Radioactive 137Cs-containing particles were used as model sources of gamma-radiation. Luminous marine bacterium Photobacterium phosphoreum was used as a bioassay with the bioluminescent intensity as the physiological parameter tested. To investigate the sensitivity of the bacteria to the low-dose gamma-radiation exposure (≤250 mGy), the irradiation conditions were varied as follows: bioluminescence intensity was measured at 5, 10, and 20°С for 175, 100, and 47 h, respectively, at different dose rates (up to 4100 μGy/h). There was no noticeable effect of gamma-radiation at 5 and 10°С, while the 20°С exposure revealed authentic bioluminescence inhibition. The 20°С results of gamma-radiation exposure were compared to those for low-dose alpha- and beta-radiation exposures studied previously under comparable experimental conditions. In contrast to ionizing radiation of alpha and beta types, gamma-emission did not initiate bacterial bioluminescence activation (adaptive response). As with alpha- and beta-radiation, gamma-emission did not demonstrate monotonic dose-effect dependencies; the bioluminescence inhibition efficiency was found to be related to the exposure time, while no dose rate dependence was found. The sequence analysis of 16S ribosomal RNA gene did not reveal a mutagenic effect of low-dose gamma radiation. The exposure time that caused 50% bioluminescence inhibition was suggested as a test parameter for radiotoxicity evaluation under conditions of chronic low-dose gamma irradiation.

Effect of aluminum metal surface on oxidation of iodide under gamma irradiation conditions

The effects of aluminum surface on I− oxidation under gamma irradiation were investigated. Without irradiation, only O2 oxidized I− at pH < 2, and aluminum expedited the oxidation reaction. With irradiation, the radiolysis products from water and air oxidized I− into $${{\text{I}}_{3}}^{ - } .$$ At pH 6, the H2O2 radiolysis product reduced $${{\text{I}}_{3}}^{ - }$$ into I−. A smaller amount of $${{\text{I}}_{3}}^{ - }$$ was observed in pH 1.9 and 3.3 solutions in contact with aluminum under irradiation because oxidants preferentially oxidize aluminum rather than I−. Moreover, for pH < 6.0, even less $${{\text{I}}_{3}}^{ - }$$ was formed by aluminum exposed to air because air radiolysis products also preferentially oxidized aluminum.

Aging of magnesium stearate under high doses gamma irradiation and oxidative conditions

In nuclear waste packages conditioning processes, magnesium stearate is widely used because of its high lubricating properties. For safety purposes, the radiolytic degradation of these organic materials has to be better understood to be able to predict their aging in repository conditions. This study reports the radiolytic degradation of magnesium stearate, using gamma-rays at room temperature and under air. Modifications were followed using different analytical tools (XPS, ATR-FTIR, ICP-AES, ATG and mass spectrometry). It has been observed that molecules mainly formed up to 1000kGy of gamma irradiation dose under radio-oxidation are alkanes, hydroperoxides, double bonds in the aliphatic chain, carboxylates with aliphatic chain shorter than the one of stearate and ketones. At a dose of 4000kGy, dicarboxylic acids are observed: the formation of these molecules needs a dose of at least 1000kGy to be created under radio-oxidation. These observations allow us to propose a non-exhaustive degradation mechanism of magnesium stearate under gamma-irradiation at room temperature and under air.

Mechanochemical devulcanization and gamma irradiation of devulcanized waste rubber/high density polyethylene thermoplastic elastomer

Waste rubber (WR) powder was introduced in a two-roll mill in the presence of various ratios of curatives to develop sheets of devulcanized waste rubber (DWR). The product has been investigated by FTIR, TGA and SEM. A thermoplastic elastomer (TPE) was prepared by blending the obtained DWR with high density polyethylene (HDPE) at different feed ratios under conditions of gamma irradiation, 25, 50, 100, and 150kGy. The mechanical parameters of the blend: tensile strength, elongation at break, and hardness (Shore D) were studied. In addition, blend characterization using FTIR spectra, gel fraction, TGA and SEM was discussed.

The gamma ray response of alanine film dosimeters at low temperatures

The response of alanine film EPR dosimeters was studied for low temperature gamma irradiation conditions (77–293K) in the dose interval from 6.3 to 80kGy. It was found that the response of the dosimeter decreases with decreased irradiation temperature and saturates at lower doses for lower irradiation temperatures. The analysis of the EPR signal suggests that the radical species formed at low temperature are the same as those used for dosimetry at room temperature, but with different concentrations. Their concentrations evolve as the temperature of the sample increases until the usual EPR signal used at room temperature is obtained.