Impact of Ag2O on the mechanical and shielding features of ZnO- Er2O3-TeO2 glasses

The investigation involves a comprehensive study on the mechanical and shielding features of the zinc erbium tellurite glasses as a function of doped Ag2O content. The mechanical features are estimated for the examined glasses by utilizing the Makishima-Makinzie model. The results showed the mechanical moduli of Young (E), bulk (B), Shear (K), and longitudinal (L) increased with the increment of the Ag2O substitution ratio. Besides, the radiation shielding properties were also studied and discussed. Among the shielding parameters, the linear attenuation coefficient (LAC), half-value layer (HVL), the lead equivalent and transmission rate (TR) were estimated. The linear attenuation coefficient results illustrated that the TZEAg glasses are better compared to the commercial marketing glasses, especially TZEAg5 glasses. Doping of Ag2O content in zinc erbium tellurite glass improves its ability to attenuate the gamma photons. Also, this study revealed the effectiveness of the examined glasses on the fast neutron, where the fast neutron mass removal cross-section ∑R (cm2/g) computed theoretically. The results offered the maximum value of ∑R = 0.019 cm2/g attained for TZEAg1 while the minimum value ∑R = 0.01884 cm2/g for TZEAg5 glass.

Possibility of simulating natural circulation in fast neutron reactors using a light water test facility

The paper evaluates the possibility of modeling the heat transfer phenomena in a liquid-metal coolant using a light water test facility. It considers the natural circulation of the coolant in the upper plenum of the fast-neutron reactor. The sodium-cooled BN-1200 reactor was selected as the reactor installation to be modeled. The development of novel reactor designs must be based on the results of experimental studies. Some problems of modeling thermohydraulic processes in BN type reactors are studied by using sodium test facilities. Experimental studies of natural convection processes using light water test facilities can be considered as a good alternative to those using sodium test facilities. To validate the model, the similarity theory and the “black box” method were used and their principles and applicability were analyzed. Using the “black box” method makes it possible to avoid detailed modeling of such components as the reactor core and heat exchangers, replacing them by a simplified representation of these components to simulate the integral characteristics of the existing real life equipment. The paper considers the basic criteria which determine the similarity of the thermohydraulic processes under study. The governing criteria of similarity were estimated based on the fundamental differential equations of natural convection heat transfer. Based on these criteria, a set of dimensionless values was obtained which show the correlation between the model parameters and the characteristics of the reactor facility. Besides, generalized relationships were derived which can be used to estimate the scaling factors for calculating the key values of the reactor facility based on the model parameters. These relationships depend on the thermal-physics parameters of the working fluids, the geometrical scale value and the ratio of the thermal power of the model to that of the reactor facility, i.e., model-to-reactor thermal power ratio. The conditions under which it is possible to model sodium coolant by light water with adequate accuracy were analyzed. An example is given of the numerical values of the scaling factors for one of the reference light water test facilities. The paper uses the experience of a number of foreign researchers in this field, in particular, the accepted assumptions which do not result in serious loss in modeling accuracy. According to the available estimates, the assumptions used do not result in considerable losses in accuracy. Thus, the natural circulation of the sodium coolant in the upper plenum of the fast-neutron reactor can be simulated with adequate accuracy by using light water test facilities.

Analysis of the Appearance of Micronuclei in the Erythrocytes and Activity of Bone Marrow Cells Proliferation after the Prolonged Low Dose Fast Neutrons Irradiation of Mice

Purpose: To analyze the level of cytogenetic damage and the activity of bone marrow cells proliferation in C57BL/6 mice after prolonged fast neutrons low dose irradiation at 10–500 mGy. Material and methods: Male C57BL/6 mice at the age of 7–8 and 16 weeks were used in the experiments. Irradiation was carried out on an OR-M installation in the field of fast neutrons and gamma quanta using five Pu(α,n)Be radionuclide sources with a high fast neutron yield at a dose rate of 2.13 mGy/h. The frequency of polychromatophilic (PCE) and normochromic (NCE) erythrocytes with micronuclei (MN) and the ratio of PCE and NCE were analyzed using light microscopy after cytochemical staining of the bone marrow cells of control and irradiated mice. The proliferation activity of bone marrow cells was determined by the number of Ki-67+-cells. The parameters of the cell cycle and the level of apoptosis were studied after DNA staining with DAPI using flow cytometry. Statistical processing of the results was carried out according to the Student’s method using the computer program Origin. Results: It was found that prolonged irradiation of mice with fast neutrons at a low dose rate (2.13 mGy/h) at doses from 10 to 500 mGy after 24 h led to statistically significant increase in the frequency of PCE with MN at all studied doses. No dose dependence of this parameter was observed in the studied range. The increase in the frequency of PCE with MN at a dose of 500 mGy was prolonged and persisted for at least 72 h. A significant increase in the frequency of NCE with MN 24 h after irradiation was found only at a dose of 500 mGy, which persisted up to 48 h. At this dose, there was also a decrease in the number of nucleated cells in the bone marrow 24 – 72 h after exposure, a decrease in the number of Ki-67+-cells 24 h after irradiation of mice, a block of the cell cycle in the G2/M phase, and a decrease of cells in the G0/G1 phase, but after 48 h, there were no disturbances in the cell cycle. Conclusion: It has been shown that after a single total prolonged irradiation of mice at low doses (10–500 mGy), when analyzing the frequency of PCE with MN, cytogenetic damage is recorded in the bone marrow, which indicates the genetic danger of exposure to even such low levels of fast neutron irradiation. A decrease in Ki67+ cells and cell cycle arrest at the G2/M phase were found only after irradiation of mice at a dose of 500 mGy and only 24 h after exposure, while the number of nucleated cells in the bone marrow at this dose was reduced, at least to 72 h.

Fast neutron mutagenesis in soybean enriches for small indels and creates frameshift mutations

The mutagenic effects of ionizing radiation have been used for decades to create novel variants in experimental populations. Fast neutron (FN) bombardment as a mutagen has been especially widespread in plants, with extensive reports describing the induction of large structural variants, i.e., deletions, insertions, inversions, and translocations. However, the full spectrum of FN-induced mutations is poorly understood. We contrast small insertions and deletions (indels) observed in 27 soybean lines subject to FN irradiation with the standing indels identified in 107 diverse soybean lines. We use the same populations to contrast the nature and context (bases flanking a nucleotide change) of single nucleotide variants. The accumulation of new single nucleotide changes in FN lines is marginally higher than expected based on spontaneous mutation. In FN treated lines and in standing variation, C→T transitions and the corresponding reverse complement G→A transitions are the most abundant and occur most frequently in a CpG local context. These data indicate that most SNPs identified in FN lines are likely derived from spontaneous de novo processes in generations following mutagenesis rather than from the FN irradiation mutagen. However, small indels in FN lines differ from standing variants. Short insertions, from 1–6 base pairs, are less abundant than in standing variation. Short deletions are more abundant and prone to induce frameshift mutations that should disrupt the structure and function of encoded proteins. These findings indicate that FN irradiation generates numerous small indels, increasing the abundance of loss of function mutations that impact single genes.