This paper discusses the results obtained during an investigation of WWER-1000 Nuclear Power Plant (NPP) behavior at shutdown reactor during maintenance. For the purpose of the analysis is selected a plant operating s...This paper discusses the results obtained during an investigation of WWER-1000 Nuclear Power Plant (NPP) behavior at shutdown reactor during maintenance. For the purpose of the analysis is selected a plant operating state with unsealed primary circuit by removing the MCP head. The reference nuclear power plant is Unit 6 at Kozloduy NPP (KNPP) site. RELAP5/ MOD3.2 computer code has been used to simulate the transient for WWER-1000/V320 NPP model. A model of WWER-1000 based on Unit 6 of KNPP has been developed for the RELAP5/MOD3.2 code at the Institute for Nuclear Research and Nuclear Energy-Bulgarian Academy of Sciences (INRNE-BAS), Sofia. The plant modifications performed in frame of modernization program have been taken into account for the investigated conditions for the unsealed primary circuit. The most specific in this analysis compared to the analyses of NPP accidents at full power is the unavailability of some important safety systems. For the purpose of the present investigation two scenarios have been studied, involving a different number of safety systems with and without operator actions. The selected initiating event and scenarios are used in support of analytical validation of Emergency Operating Procedures (EOP) at low power and they are based on the suggestions of leading KNPP experts and are important in support of analytical validation of EOP at low power.展开更多
In light of the possibility of reignition when unsealing the closed fire zones, the occurrence of reignition was simulated by a home-made experimental device, hydrogen variety rule from combustion to unsealing was ana...In light of the possibility of reignition when unsealing the closed fire zones, the occurrence of reignition was simulated by a home-made experimental device, hydrogen variety rule from combustion to unsealing was analyzed, the three-stage generation model of hydrogen during reignition in fire zone was put forward and the probability that hydrogen was taken as an indicator gas was discussed. The results show that: when fire zone is ready to unseal, which is filled with hydrogen at a high concentration, it is more prone to reignite.展开更多
Coal is the one of foundations of energy and economic structure in China,while the unsealing of coal mine fres would cause a great risk of coal re-ignition.In order to explore the infuence of pressure-bearing state on...Coal is the one of foundations of energy and economic structure in China,while the unsealing of coal mine fres would cause a great risk of coal re-ignition.In order to explore the infuence of pressure-bearing state on the re-ignition characteristics for residual coal,the uniaxial compression equipped with a temperature-programmed device was built.The scanning electron microscope,synchronous thermal analyzer and Fourier transform infrared absorption spectrometer was applied to investigate the microscopic structure and thermal efect of the coal samples.Moreover,the microscopic efect of uniaxial stress on coal re-ignition is revealed,and the re-ignition mechanism is also obtained.As the uniaxial stress increasing,the number,depth and length of the fractures of the pre-treated coal increases.The application of uniaxial stress causes the thermal conductivity to change periodically,enhances the inhibition of injecting nitrogen on heat transfer and prolonges the duration of oxidation exothermic.The content of oxygen-containing functional groups has a high correlation with apparent activation energy,and coal samples at 6 MPa is more probability to re-ignite while the fre zone is unsealed.Uniaxial stress could control the re-ignition mechanism by changing the structure of fractures and pores.The side chains and functional groups of coal structure are easier to be broken by thermal-stress coupling.The higher the·OH content,the more difcult coal samples would be re-ignited.The research results would lay a solid theoretical foundation for the safe unsealing of closed fre-areas underground,tighten the common bond between the actual industry and the experimental theory in closed fre-areas underground,and provide the theoretical guidance for coal re-ignition preventing.展开更多
Given the problem of harmful gas discharge in unsealing coal mining faces, we numerically simulated the process of change of gas flows and movements, We have pointed out that, at the moment of unsealing a closed stope...Given the problem of harmful gas discharge in unsealing coal mining faces, we numerically simulated the process of change of gas flows and movements, We have pointed out that, at the moment of unsealing a closed stope, the gas discharge is naturally divided into two parts, i.e., the discharge of gas in the working face and that in the goaf, because of the difference in the spatial medium. The absolute volume of gas discharged has a tendency to decrease from its initial peak value to a final stable value. The rate of decrease and the time needed to reach a stable discharge are related to the scale of the mining stope. The discharge of gas from the working face is closely related to the amount of air distributed in the air return way. The most important thing in unsealing a stope is to have the initial peak volume of gas discharged well under control. A commonly used method in solving this problem is at first to use a small amount of air and then increasing it gradually. Our study shows that, by extracting gas from the upper corner, we can use a large volume of air at first in order to shorten considerably the discharge time and improve efficiency, thereby making mining, activitv safer.展开更多
<strong>Aim:</strong><span style="font-family:Verdana;"> To describe the epidemiological, therapeutic and prognostic aspects of eclampsia at the second reference hospital in the urban commu...<strong>Aim:</strong><span style="font-family:Verdana;"> To describe the epidemiological, therapeutic and prognostic aspects of eclampsia at the second reference hospital in the urban commune of Ségou in Mali.</span><span style="font-family:;" "=""> </span><b><span style="font-family:Verdana;">Patient and Methods:</span></b><span style="font-family:Verdana;"> This was a descriptive, cross-sectional, analytical, retrospective and prospective study based on a comprehensive de-engineering.</span><span style="font-family:Verdana;"> It covered a 3-year period from January 1, 2010 to December 31, 2012 and involved 176 cases.</span><span style="font-family:;" "=""> </span><b><span style="font-family:Verdana;">Results:</span></b><span style="font-family:Verdana;"> The incidence of eclampsia during the study period was 2.9%. Classically, it occurred in 74.4% in young primigeste, in 73.9% in the</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">3</span><sup><span style="font-family:Verdana;">rd</span></sup><span style="font-family:Verdana;"> trimester of pregnancy and 26.1% of cases during postpartum. We recorded maternal complications such as retro-placental hematoma, acute kidney failure and delivery hemorrhage. The case fatality rate was 2.3% or 4 cases of maternal death. At the fetal level, there was 29.5% prematurity, 31.8% neonatal suffering, 11.4% hypotrophy, 11.9% </span><i><span style="font-family:Verdana;">in</span></i></span><i><span style="font-family:;" "=""> </span></i><i><span style="font-family:Verdana;">utero</span></i><span style="font-family:Verdana;"> fetal death and 7.4% early neonatal death.</span><span style="font-family:;" "=""> </span><b><span style="font-family:Verdana;">Conclusion:</span></b><span style="font-family:Verdana;"> The maternal-fetal prognosis remains reserved despite the progress made in the management of eclampsia in our services.</span>展开更多
文摘This paper discusses the results obtained during an investigation of WWER-1000 Nuclear Power Plant (NPP) behavior at shutdown reactor during maintenance. For the purpose of the analysis is selected a plant operating state with unsealed primary circuit by removing the MCP head. The reference nuclear power plant is Unit 6 at Kozloduy NPP (KNPP) site. RELAP5/ MOD3.2 computer code has been used to simulate the transient for WWER-1000/V320 NPP model. A model of WWER-1000 based on Unit 6 of KNPP has been developed for the RELAP5/MOD3.2 code at the Institute for Nuclear Research and Nuclear Energy-Bulgarian Academy of Sciences (INRNE-BAS), Sofia. The plant modifications performed in frame of modernization program have been taken into account for the investigated conditions for the unsealed primary circuit. The most specific in this analysis compared to the analyses of NPP accidents at full power is the unavailability of some important safety systems. For the purpose of the present investigation two scenarios have been studied, involving a different number of safety systems with and without operator actions. The selected initiating event and scenarios are used in support of analytical validation of Emergency Operating Procedures (EOP) at low power and they are based on the suggestions of leading KNPP experts and are important in support of analytical validation of EOP at low power.
基金supported by the National Natural Science Foundation of China (No.50604014)the Program for New Century Excellent Talent Project(No.NCET-08-0838)the Research Fund of the State Key Laboratory of Coal Resources and Safe Mining,CUMT (No.09KF11)
文摘In light of the possibility of reignition when unsealing the closed fire zones, the occurrence of reignition was simulated by a home-made experimental device, hydrogen variety rule from combustion to unsealing was analyzed, the three-stage generation model of hydrogen during reignition in fire zone was put forward and the probability that hydrogen was taken as an indicator gas was discussed. The results show that: when fire zone is ready to unseal, which is filled with hydrogen at a high concentration, it is more prone to reignite.
基金funding provided by the National Natural Science Foundation of China(52074108 and 51874124)the Project supported by Fund for Creative Talents of Henan Colleges in China(22HASTIT012)+1 种基金the Key Science and Technology Program of Henan Province(212102310007)It also supported by the Scientifc Research Foundation of the Higher Education Institutions of Henan Province in China(22A620001).
文摘Coal is the one of foundations of energy and economic structure in China,while the unsealing of coal mine fres would cause a great risk of coal re-ignition.In order to explore the infuence of pressure-bearing state on the re-ignition characteristics for residual coal,the uniaxial compression equipped with a temperature-programmed device was built.The scanning electron microscope,synchronous thermal analyzer and Fourier transform infrared absorption spectrometer was applied to investigate the microscopic structure and thermal efect of the coal samples.Moreover,the microscopic efect of uniaxial stress on coal re-ignition is revealed,and the re-ignition mechanism is also obtained.As the uniaxial stress increasing,the number,depth and length of the fractures of the pre-treated coal increases.The application of uniaxial stress causes the thermal conductivity to change periodically,enhances the inhibition of injecting nitrogen on heat transfer and prolonges the duration of oxidation exothermic.The content of oxygen-containing functional groups has a high correlation with apparent activation energy,and coal samples at 6 MPa is more probability to re-ignite while the fre zone is unsealed.Uniaxial stress could control the re-ignition mechanism by changing the structure of fractures and pores.The side chains and functional groups of coal structure are easier to be broken by thermal-stress coupling.The higher the·OH content,the more difcult coal samples would be re-ignited.The research results would lay a solid theoretical foundation for the safe unsealing of closed fre-areas underground,tighten the common bond between the actual industry and the experimental theory in closed fre-areas underground,and provide the theoretical guidance for coal re-ignition preventing.
基金Project 50574038 supported by the National Natural Science Foundation of Chinathe Scientific Research Foundation of Liaoning Technical University (No.2004-241)
文摘Given the problem of harmful gas discharge in unsealing coal mining faces, we numerically simulated the process of change of gas flows and movements, We have pointed out that, at the moment of unsealing a closed stope, the gas discharge is naturally divided into two parts, i.e., the discharge of gas in the working face and that in the goaf, because of the difference in the spatial medium. The absolute volume of gas discharged has a tendency to decrease from its initial peak value to a final stable value. The rate of decrease and the time needed to reach a stable discharge are related to the scale of the mining stope. The discharge of gas from the working face is closely related to the amount of air distributed in the air return way. The most important thing in unsealing a stope is to have the initial peak volume of gas discharged well under control. A commonly used method in solving this problem is at first to use a small amount of air and then increasing it gradually. Our study shows that, by extracting gas from the upper corner, we can use a large volume of air at first in order to shorten considerably the discharge time and improve efficiency, thereby making mining, activitv safer.
文摘<strong>Aim:</strong><span style="font-family:Verdana;"> To describe the epidemiological, therapeutic and prognostic aspects of eclampsia at the second reference hospital in the urban commune of Ségou in Mali.</span><span style="font-family:;" "=""> </span><b><span style="font-family:Verdana;">Patient and Methods:</span></b><span style="font-family:Verdana;"> This was a descriptive, cross-sectional, analytical, retrospective and prospective study based on a comprehensive de-engineering.</span><span style="font-family:Verdana;"> It covered a 3-year period from January 1, 2010 to December 31, 2012 and involved 176 cases.</span><span style="font-family:;" "=""> </span><b><span style="font-family:Verdana;">Results:</span></b><span style="font-family:Verdana;"> The incidence of eclampsia during the study period was 2.9%. Classically, it occurred in 74.4% in young primigeste, in 73.9% in the</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">3</span><sup><span style="font-family:Verdana;">rd</span></sup><span style="font-family:Verdana;"> trimester of pregnancy and 26.1% of cases during postpartum. We recorded maternal complications such as retro-placental hematoma, acute kidney failure and delivery hemorrhage. The case fatality rate was 2.3% or 4 cases of maternal death. At the fetal level, there was 29.5% prematurity, 31.8% neonatal suffering, 11.4% hypotrophy, 11.9% </span><i><span style="font-family:Verdana;">in</span></i></span><i><span style="font-family:;" "=""> </span></i><i><span style="font-family:Verdana;">utero</span></i><span style="font-family:Verdana;"> fetal death and 7.4% early neonatal death.</span><span style="font-family:;" "=""> </span><b><span style="font-family:Verdana;">Conclusion:</span></b><span style="font-family:Verdana;"> The maternal-fetal prognosis remains reserved despite the progress made in the management of eclampsia in our services.</span>
