Study of Accident Progression in Unsealed WWER-1000/V320 Reactor during Maintenance

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.

Effect mechanism of nitrogen injection into fire-sealed-zone on residual-coal re-ignition under stress in goaf

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.

Maternal-Fetal Prognosis of Eclampsia at the Second Reference Hospital in the Urban Commune of Segou in Mali

Aim: To describe the epidemiological, therapeutic and prognostic aspects of eclampsia at the second reference hospital in the urban commune of Ségou in Mali. Patient and Methods: This was a descriptive, cross-sectional, analytical, retrospective and prospective study based on a comprehensive de-engineering. It covered a 3-year period from January 1, 2010 to December 31, 2012 and involved 176 cases. Results: 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 3rd 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% in utero fetal death and 7.4% early neonatal death. Conclusion: The maternal-fetal prognosis remains reserved despite the progress made in the management of eclampsia in our services.