Study On Dynamic Response And Measures Of Seismic Reduction And Anti-explosion Of Nuclear Island Subjected To Strong Earthquakes And Blast Loads

Reinforced concrete structure of NPP is the significant infrastructure to ensure the safety of nuclear power engineering, and the safety of NPP during operation service is the key issue of the construction and development of the NPP. Because of the uncertainty and randomness of the earthquake ground motions, NPP may suffer from beyond design basis earthquake (BDBE) or strong earthquakes in the operation of the structure, and the BDBE can result NPP in damage, even cause nuclear leakage. Seismic safety evaluation of NPP in operation period is still a crucial content of disaster prevent and mitigation research of nuclear engineering. Due to the significant of NPP, NPP possible targets for terrorist attacks or intentional explosions, once the NPP suffers bomb attack, it will cause serious nuclear disaster and most undesirable impact on the people and environment. Therefore, study on the dynamic response and damage mechanism of the NPP subjected to strong earthquakes or explosions, investigation on the feasibility of shock absorption and anti-explosion measures are critical issues for the construction of NPP.The dynamic response, damage mechanism, fluid-structure interaction (FSI), sloshing of water, shock absorption, optimum design of water storage tank under safe shutdown earthquake (SSE) have been investigated; The shock wave propagation characteristics of internal explosion in reinforced concrete containment, dynamic response behaviors and anti-explosion measures of reinforced concrete containment vessel are systematically and deeply studied to solve the critical issues and technique problems of NPP, some conclusions with theoretical and practical value are obtained. The major contents and innovation of this paper are concluded as follows:(1) The influence rule of the base isolation on the dynamic responses and response spectra of the nuclear island, internal equipment and pipes are studied, and the connection types of the pipes for the isolated structure are also investigated in this paper. Based on the principle of base isolation, the performance index of acceleration response, displacement response, story displacements and decreasing amplitude ratio of both isolated and non-isolated nuclear island subjected to SSE are compared and analyzed. The influence law of isolation system on floor response spectra of internal critical equipment and pipes are studied, the inherent relations of vertical predominant frequencies between internal equipment, pipes and base isolation system are significant investigated subjected to earthquakes. It is concluded that the vibration reductions in vertical direction of internal important equipment and pipes for nuclear island buildings under earthquake are well solved by isolation systems, the maintenance difficulty of the damper setting and the installation difficulty of isolated devices for internal equipment and pipes are also reduced. The feasibility and safety links of isolated equipment and pipes are solved perfectly.(2) The present work investigates the adaptability of the isolated nuclear island under the near-fault ground motion, far-fault ground motion, pulse wave and high frequency wave. The influence rules and impact mechanism of seismic performance for isolated and non-isolated structures subjected to various components of near-fault ground motions are discussed through the analysis of the dynamic response and floor response spectra of isolate and non-isolated nuclear island subjected to near-fault ground motions, pulse wave and high frequency wave. The variation law of floor response spectra for isolated and non-isolated nuclear island is also deeply revealed. The damage abilities of the same magnitude near-fault and far-fault ground motions for isolated and non-isolated nuclear island buildings are studied and compared in order to verify the feasibility and adaptability of the isolated nuclear island building under near-fault ground motion.(3) The present work proposes the optimum scheme of the air intake and water level of shield building. The influences of different design cases on natural frequencies of shield building are analyzed at the base of initial design of shield building considering FSI effects of water tank. The dynamic response and mechanism of stress distribution of shield building subjected to earthquake loads are studied. The water level height, shape and height of air intakes which affected natural frequency of shield building are optimally designed. Finally, the optimal design schemes of air intakes shapes and heights are obtained and confirmed in this paper.(4) The optimum scheme of vibration reduction for water tank of AP1000NPP shield building is proposed in present work. The fully coupled and precise model of water storage tank for API000NPP is established based on the ALE coupled algorithm and FSI effects. The dynamic responses of water storage tank subjected to El-Centro and artificial earthquake which satisfied with RG1.60spectrum are analyzed. The mechanics and relationships of displacement response and acceleration response with water level height, air height, height ratio of water, mass ratio of water and oscillation frequency of water tank are parametrically analyzed and extensively revealed. The optimum water level of water tank in reducing seismic response is discussed. In the condition of initial water level for AP1000, six optimal design schemes of water storage tank are proposed and the optimal design scheme of baffle in reduction of vibration are obtained.(5) The accuracy and reliability of the ALE coupling algorithm in simulation of problems of blast and shock wave is verified. The fully coupled numerical model of reinforced concrete containment of CPRI000is established considering the high strain rate effect of concrete and the complex of the interaction between blast loading and structure. The variation law of low field dynamic response and peak pressure when the containment vessel subjected to internal blast for different scale distance and explosion charges is investigated. The accuracy and reliability of coupled model is verified by comparing results with the experiment and empirical equations.(6) The present work proposes the anti-explosion measures of decompression valves and gas recover device. The variation relationships of incident wave, reflected wave and peak pressure in containment are deeply analyzed based on the ALE and FSI model. The vulnerable place or components of containment are obtained and the anti-explosion measures and decompression valves are designed. It is concluded that the installation of anti-explosion measures of decompression valves and gas recover device in containment are feasible and reliable.