The Westinghouse Nuclear Safety Advisory Letter NSAL-09-8 investigated the possibility of presence of vapor in RHR （residual heat removal） system in modes 3/4 LOCA （loss-of-coolant accident） conditions. This conce...The Westinghouse Nuclear Safety Advisory Letter NSAL-09-8 investigated the possibility of presence of vapor in RHR （residual heat removal） system in modes 3/4 LOCA （loss-of-coolant accident） conditions. This concerns the Westinghouse standard three-loops plant for which the RHR is the low pressure part of the St （safety injection）. In some cases one or both RHR trains may become inoperable for SI function. As a response to this letter, Westinghouse Electric Belgium is providing RELAP5 analyzes for Westinghouse NSSS （nuclear steam supply system） European plants to assess the thermal hydraulic behavior of the RHR suction piping system for ECCS （emergency core cooling system） initiation events postulated to occur during startup/shutdown operations. Several concerns including condensation induced water hammer and voiding at the RHR pump have been investigated. As a conclusion, the analysis allowed to define the bounding hot leg temperature conditions under which both RHR trains remain safely operable. These bounding conditions are then implemented by the customer in their OPs （operating procedures） to achieve safe operations and successful accident management.展开更多
To investigate the non-linear hydrodynamics in horizontal gas-liquid bubblyflow, time-series data of local void fraction were obtained using a double sensor probe. Bothdeterministic chaos and stochastic analyses were ...To investigate the non-linear hydrodynamics in horizontal gas-liquid bubblyflow, time-series data of local void fraction were obtained using a double sensor probe. Bothdeterministic chaos and stochastic analyses were used to diagnose the dynamic behaviors in thesystem. The power spectra of the local void fraction exhibited no single distinct peak, indicatingthe aperiodic nature of the variation of the local void fraction. The kolmogorov entropy andcorrelation dimension of the attractor reconstructed from the time-series data by the embeddingmethod were to be positive and very large, the Hurst exponent computed from the rescaled rangeanalysis was found to be larger than 0. 5, indicating the non-linear chaotic feature of the system.The Kolmogorov entropy and the correlation dimension decrease with increasing liquid superficialvelocity, and the correlation dimension changes less if the gas superficial velocity is high. On theother hand, the fluctuation of local void fraction in horizontal gas-liquid bubbly flow could beconsidered to take place due to the zigzag motion of bubbles with different shape, size andvelocity.展开更多
文摘The Westinghouse Nuclear Safety Advisory Letter NSAL-09-8 investigated the possibility of presence of vapor in RHR （residual heat removal） system in modes 3/4 LOCA （loss-of-coolant accident） conditions. This concerns the Westinghouse standard three-loops plant for which the RHR is the low pressure part of the St （safety injection）. In some cases one or both RHR trains may become inoperable for SI function. As a response to this letter, Westinghouse Electric Belgium is providing RELAP5 analyzes for Westinghouse NSSS （nuclear steam supply system） European plants to assess the thermal hydraulic behavior of the RHR suction piping system for ECCS （emergency core cooling system） initiation events postulated to occur during startup/shutdown operations. Several concerns including condensation induced water hammer and voiding at the RHR pump have been investigated. As a conclusion, the analysis allowed to define the bounding hot leg temperature conditions under which both RHR trains remain safely operable. These bounding conditions are then implemented by the customer in their OPs （operating procedures） to achieve safe operations and successful accident management.
文摘To investigate the non-linear hydrodynamics in horizontal gas-liquid bubblyflow, time-series data of local void fraction were obtained using a double sensor probe. Bothdeterministic chaos and stochastic analyses were used to diagnose the dynamic behaviors in thesystem. The power spectra of the local void fraction exhibited no single distinct peak, indicatingthe aperiodic nature of the variation of the local void fraction. The kolmogorov entropy andcorrelation dimension of the attractor reconstructed from the time-series data by the embeddingmethod were to be positive and very large, the Hurst exponent computed from the rescaled rangeanalysis was found to be larger than 0. 5, indicating the non-linear chaotic feature of the system.The Kolmogorov entropy and the correlation dimension decrease with increasing liquid superficialvelocity, and the correlation dimension changes less if the gas superficial velocity is high. On theother hand, the fluctuation of local void fraction in horizontal gas-liquid bubbly flow could beconsidered to take place due to the zigzag motion of bubbles with different shape, size andvelocity.
