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BackgroundCore fuel salt emergency drain system designed for fuel salt drain and afterheat removal, provides a safe shutdown mode for a molten salt reactor (MSR). It has important significance to evaluate reliability of the system for the safety of MSRs.PurposeThis study aims to quantitatively analyze the failure probabilty of the system and identify the pivotal factors that affecting the system failures, and provide suggestions for optimization of the system in engineering application.MethodsFirst of all, the fault tree analysis was employed to model the reliability of the core fuel salt drain system of MSRE through RiskSpectrum software. Then, the minimum cut sets and importance analysis was adopted to identify the most important basic event in fault tree of the system. Finally, two optimization methods, i.e., reduce the use of welds in bayonet cooling thimbles, and use different types of valves to isolate cooling gas flow of freeze valve, were proposed.ResultsThe results show that failure probability of the system is 5.62×10-4, and the identified pivotal factors affecting the system failures are welds leakage failures of thimbles and common cause failure of two groups valves of freeze valve. The optimization methods based on results of fault tree analysis can significantly reduce the system failure probability.ConclusionsThis study provides reference value for design and engineering application of the core fuel salt emergency drain system for MSRs.

BackgroundIn the reactivity initiated accidents under low power operating conditions of molten salt reactor (MSR), different reactivity insertion rates will trigger different emergency shutdown signals. At the same time, the initial conditions such as the initial reactor power and the temperature coefficients of reactivity affect the accident process and cause differences in accident consequences.PurposeThe study aims to conduct a sensitivity analysis of the impact of the reactivity insertion rate, the initial reactor power, and the reactivity temperature coefficient on transient consequences.MethodsFirst of all, 7 reactivity insertion rate conditions were selected and simulated through RELAP5-TMSR.Then, 25 combinations of the initial reactor power and the temperature coefficients of reactivity were assumed as initial conditions. Finally, the effects of these three parameters on the consequences of the accident were discussed separately by using local sensitivity analysis method.ResultsThe insertion rate that causes a concurrent trigger of the high outlet temperature and the high-power shutdown signal leads to the most unfavorable consequence. The difference between the peak temperatures of the fuel salt and structural materials and their respective initial values under the worst reactivity insertion rate condition is negatively correlated with initial power. However, the temperature difference of each parameter caused by different initial power does not exceed 3 ℃. The difference between the peak temperatures decrease first and then increases with the increase of the temperature coefficients of reactivity, but the maximum difference does not exceed 0.5 ℃.ConclusionsUnder low power operating conditions of MSR, the consequences of reactivity introduced events are highly sensitive to the reactivity insertion rate and low sensitivity to the initial power and temperature coefficients of reactivity.

Summary: The trip setpoint parameters of a molten salt reactor have been analyzed by performing multiple linear regression (MLR) method. In the analysis, a reactivity‐initiated accident with inadvertent control rod withdrawal accident under low power condition was considered as the initiating event. A total of 285 cases located from 20 235 thermal‐hydraulic simulation runs have been divided into identification dataset (70%) and test dataset (30%) for MLR. MLR models show that the maximum fuel salt temperature and corresponding control rod extraction rate follow a quite convincing linear hypotheses relationship with trip setpoint parameters. Sensitivity analysis gives the sensitivity rankings of trip setpoint parameters. And the predictive values of three significantly influential trip setpoint parameters with different margin considerations have been acquired quantitatively. [ABSTRACT FROM AUTHOR]

Background: The underlying mechanisms of neuropathic pain remain unclear. This work aimed to investigate the role of Sirtuin3 (SIRT3), an nicotinamide adenosine dinucleotide+-dependent histone deacetylase, in the development of neuropathic pain induced by type 2 diabetes mellitus (T2DM) and to explore the associated mechanisms.Methods: Diabetic neuropathic pain (DNP) in rats was induced by high-fat diet/low-dose streptozotocin. The pain behaviors were examined using the von Frey and Hargreaves tests. The levels of SIRT3, manganese superoxide dismutase (MnSOD) and catalase (CAT) were determined using Western blot and RT-qPCR. The acetylation, phosphorylation and ubiquitination of forkhead box class O3a (FoxO3a) were analyzed by immunoprecipitation and Western blot.Results: SIRT3 expression and activity were significantly reduced in the spinal dorsal horn of DNP model rats. Overexpression of spinal SIRT3 reversed the pain hypersensitivity in the DNP model rats, but knockdown of spinal SIRT3 mimicked the pain effect, eliciting pain hypersensitivity in normal rats. Moreover, overexpression of spinal SIRT3 in DNP model rats increased the FoxO3a level and upregulated the antioxidant genes MnSOD and CAT by deacetylating FoxO3a and inhibiting FoxO3a phosphorylation and ubiquitination. Knockdown of spinal SIRT3 in normal rats decreased the FoxO3a level and downregulated MnSOD and CAT by inhibiting the deacetylation of FoxO3a and further increasing FoxO3a phosphorylation and ubiquitination.Conclusions: These results suggest that, by deacetylating FoxO3a and further reducing its phosphorylation, ubiquitination and degradation in the spinal dorsal horn, SIRT3 stabilizes FoxO3a protein and inhibits oxidative stress, resulting in pain alleviation in T2DM model rats. [ABSTRACT FROM AUTHOR]

Background: The underlying mechanisms of neuropathic pain remain unclear. This work aimed to investigate the role of Sirtuin3 (SIRT3), an nicotinamide adenosine dinucleotide+-dependent histone deacetylase, in the development of neuropathic pain induced by type 2 diabetes mellitus (T2DM) and to explore the associated mechanisms., Methods: Diabetic neuropathic pain (DNP) in rats was induced by high-fat diet/low-dose streptozotocin. The pain behaviors were examined using the von Frey and Hargreaves tests. The levels of SIRT3, manganese superoxide dismutase (MnSOD) and catalase (CAT) were determined using Western blot and RT-qPCR. The acetylation, phosphorylation and ubiquitination of forkhead box class O3a (FoxO3a) were analyzed by immunoprecipitation and Western blot., Results: SIRT3 expression and activity were significantly reduced in the spinal dorsal horn of DNP model rats. Overexpression of spinal SIRT3 reversed the pain hypersensitivity in the DNP model rats, but knockdown of spinal SIRT3 mimicked the pain effect, eliciting pain hypersensitivity in normal rats. Moreover, overexpression of spinal SIRT3 in DNP model rats increased the FoxO3a level and upregulated the antioxidant genes MnSOD and CAT by deacetylating FoxO3a and inhibiting FoxO3a phosphorylation and ubiquitination. Knockdown of spinal SIRT3 in normal rats decreased the FoxO3a level and downregulated MnSOD and CAT by inhibiting the deacetylation of FoxO3a and further increasing FoxO3a phosphorylation and ubiquitination., Conclusions: These results suggest that, by deacetylating FoxO3a and further reducing its phosphorylation, ubiquitination and degradation in the spinal dorsal horn, SIRT3 stabilizes FoxO3a protein and inhibits oxidative stress, resulting in pain alleviation in T2DM model rats., Competing Interests: Competing interests: None declared., (© American Society of Regional Anesthesia & Pain Medicine 2021. No commercial re-use. See rights and permissions. Published by BMJ.)