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[en] Highlights: • The severe accident issues of LBE-cooled reactors are summarized. • Key processes and phenomena during CDAs of LBE-cooled reactors are discussed. • The systematic framework of severe accident safety analysis of LBE-cooled reactors is given. - Abstract: The safety analysis work is always a key issue for the nuclear power plant licensing. After Fukushima Accident of Japan, the severe accident safety analysis has been more concerned, which would be also very important and essential for the Research and Development (R&D) work of LBE-cooled reactors. So far, a great number of studies on severe accident of LBE-cooled reactors have been carried out. In this paper, a summary of severe accident of LBE-cooled reactors is conducted, which contains almost all the relevant issues on the hypothetical Core Disruptive Accidents (CDAs). Detailed contents of these issues are discussed. The systematic framework of severe accident safety analysis of LBE-cooled reactors is preliminarily given, which aims at providing a useful reference for the further safety analysis research work of this kind of advanced reactor.
[en] Objective: The purpose of this study was to observe the effect of 60Co γ-irradiation on C6 rat astrocytoma cells and investigate the possible mechanism. Methods: Cultured C6 cells were divided into 4 groups to receive different doses of γ-irradiation: control group, 4 Gy group, 16 Gy group, and 64 Gy group. After irradiation the growth curve of cells was made by the methyl thiazolyl tetrazolium (MTF) assay. Flow cytometry was utilized to quantify the percentage of cell apoptosis and the cell cycle distribution 48 h after treatment. P53 and P21 expressions in the cells before and after treatment were analyzed by immunocytochemistry. Results: Significant inhibition of proliferation was found in cells of the 16 Gy and 64 Gy groups. As the irradiation doses were raised, the apoptotic rates were significantly increased [3.1±0.5, 16.7± 0.6, 27.3±0.4 and (36.7±0.7)% for the control, 4 Gy, 16 Gy and 64 Gy groups, respectively, P< 0.01]. Howerver, the necrotic rates of the four groups were not significantly different (P>0.05). Meanwhile, as the doses of irradiation were raised, a significantly larger percentage of cells in G0/G1 phase and a smaller one in S phase were found. The expressions of P53 and P21 were both enhanced after irradiation and the enhancement was dose-dependent. Besides, the expressions of P53 and P21 were positively related and the correlation coefficient was 0.889. Conclusion: The inhibition of proliferation of C6 cells after 60Co γ-irradiation may be realized simultaneously by cell apoptosis, G1 arrest and S delay. The p53-p21 pathway may be involved in this process. (authors)
[en] Objective: To investigate the effect and mechanism of boron neutron capture therapy (BNCT) in C6 glioma cell line. Methods: C6 cells in exponential phase were divided into 6 groups: untreated control, 60Co γ 4 Gy, 60Co γ 8 Gy, nuclear reactor exposure without boronophenylalanine(BPA) 3 Gy, BNCT 4 Gy and BNCT 8 Gy. Cellular morphological change was observed by an inverted microscope, light microscope, fluorescence microscope and electronic microscope. Flow cytometry was used to determine the percentage of apoptosis, necrosis and normal cells 48 h after irradiation. Colony forming assay was used to calculate cell surviving fraction. Results: Typical morphological changes of apoptosis were observed early after irradiation in BNCT group, with a significant increase in apoptotic rates was observed 48 h after irradiation with 63.2% and 88.3% for BNCT 4 Gy and 8 Gy group, respectively (P < 0.05 vs untreated control). BNCT showed stronger growth inhibition than the same dose of y-ray irradiation (P<0.01). The surviving fraction of BNCT group was significantly lower than that of reactor and y-ray control group (P<0.01). Conclusions: Through inducing more apoptosis, BNCT shows much higher relative biological effect than T irradiation on C6 cell line. (authors)
[en] To avoid the inlet unstart at high equivalence ratio and increase the performance of scramjet with ram-mode, a flow control method of boundary-layer ejection is implemented based on the potential thermodynamic process in a turbo-pump supply system of fuel vapor within a cooling channel. The effect of ejection on overall scramjet performance is studied by taking the integration of measures including numerical simulation and stream thrust analysis. Results indicate that the critical backpressure is significantly increased as the ejection total pressure increased, thereby increasing the compression capacity and efficiency, and decreasing the irreversible losses of shock wave and viscous dissipation. For the ejection total pressure of P_t_,_e_j_e = 2.40–4.00 × 10"6 Pa, the critical backpressure ratio is quantitatively increased by 1.18–11.8% along with the utilization of ejection mass flow rate of about 88.0–100% overall mass flow rate of methane fuel gas, and simultaneously the total pressure ratio, kinetic efficiency is also increased by 7.32–13.1%, and 1.63–2.96%, respectively, while the dimensionless entropy increase is decreased by 14.5–26.8%. On this basis, the specific thrust, specific impulse, and total efficiency is increased by 2.84–4.69%, 2.80–4.68%, and 2.87–4.70%, respectively, which re-emphasizes that the boundary-layer ejection is an available fluid control method. - Highlights: • Pressure ratio affects cycle efficiency based on Brayton cycle analysis. • Ejection control concept is defined based on potential thermodynamic process. • Ejection increases compression capacity, efficiency and engine overall performance.
[en] Objective: To investigate the inhibition of boron neutron capture therapy(BNCT) on SHG44 glioma cell line and its mechanism. Methods: Methyl thiazolyl tetrazolium (MTT) assay was used to measure the level of the proliferation of SHG44. HE staining, Hoechst33342 fluorescence staining, transmission electron microscope(TEM) were applied to observe the changes in cell morphology. The effects of BNCT on cell apoptotic rate was observed by flow cytometer (FCM). The expression of Bcl-2 and Bax protein was measured by Western blot. Results: The proliferation of SHG44 was obviously inhibited by BNCT in a dose-dependent manner. The results of FCM showed that the apoptotic cell rate 48 h after irradiation with 4 and 8 Gy 63.2% and 88.3%, respectively. Western blot analysis showed BNCT promoted Bax protein expression, but inhibited Bcl-2 expression. Conclusions: BNCT inhibits the proliferation of SHG44 cell, induces apoptosis and promote the expression of Bax but inhibits the expression of Bcl-2. (authors)
[en] A neutron source of UHZr reactor for C6 glioma cells irradiation is designed by MCNP/4B code. Methods for cell culture, incubation, L-BPA administration, boron concentration measurement and the irradiation experiment are described. Radiobiological effects of C6 glioma cells in vitro, which are induced by BNCT, and the relations between the biological effect and the irradiation dose are studied. The results demonstrate that the cytocidal effect of the BNCT method is much more remarkable than that of gamma radiotherapy at the same absorbed dose. (authors)