Study On The Ultimate Capability Of Nuclear Concrete Containment Vessel Structure Subjected To Strong Earthquakes And Loss Of Coolant Accident

With the growth of global energy requirements and the increasingly exhaustion of fossil energy resources,nuclear power,as a kind of clean,highly efficient,environmental benign and economic energy,has been widely accepted and constructed around the world.However,several nuclear power accidents make people turn pale at the only mention of nuclear radiation,Fukushima nuclear accident has brought about worldwide re-examination and attentions about the safety of nuclear power.The prestressed concrete containment vessel(PCCV)is taken as elastic material,not considering the material nonlinear properties,but the uncertainty of ground motion and improvement of design intensity maybe suffer the beyond design basis ground motion and bring server catastrophe.Besides,loss of coolant accident(LOCA)is also the most common disasters during the operation of nuclear power plants,which will cause the leakage of radioactive material.Therefore,the study on the ultimate capability of the prestressed concrete containment vessel under seismic and LOCA is very important for the safety of nuclear power.Based on the CPR1000 prestressed concrete containment vessel structure,the integral prestressed reinforced concrete stress-strain curves of dome and cylinder were built,we obtained the allowed seismic capability of PCCV under far-field and near-field ground motion,and the destruction process of PCCV under far-field and near-field ground motion;the loss of coolant accident after seismic time history analysis were studied,the destruction process under LOCA after far-field and near-field ground motion was illustrated,the function between the internal pressure capability and experienced peak ground acceleration(PGA)was established,the allowed destruction seismic fragility and ultimate collapse seismic fragility were researched,the standard of internal pressure capability to evaluate the LOCA after seismic loading were proposed;the high confidence of low probability of failure(HCLPF)of PCCV was confirmed,the functions between failure probability and experienced PGA and guarantee rate were established.The major contents and conclusions are as follows:1)Because of the complicated configurations of reinforcement steels and tendons in the prestressed concrete containment vessel,it's very difficult to analysis the structure by finite element software.Thus,the integral stress-strain relationships of dome and cylinder body were built,disscused the different principal stress axes under uniaxial loading,and studied the different loading ratios under biaxial loading.The reliability of the analytical results was validated by simple reinforced concrete experiment and several finite element simulations analyses.2)The properties of PCCV under design basis earthquake were studied,the failure process and allowed capability under far-field and near-field ground motion was researched.It was found that the structure is under elastic stage when the peak ground acceleration is below 0.3g;and it is at the nonlinear stage gradually above 0.3g.3)The ultimate internal pressure capability and its failure model at loss of coolant accident were investigated.The internal pressure capability after far-field and near-field ground motion are also studied,the degradation rate of the pressure capability with the experienced peak ground motion were build,the function between the capability and PGA under far-field and near-field ground motion are established.The results indicated that the internal pressure capability will keep invariant when the PGA is lower than 0.3g,but the capability will be decrease when the PGA exceeds 0.3g.4)The seismic fragility curves under far-field and near-field ground motion of PCCV were studied,obtaining the failure seismic loaidng and collapse seismic fragility under different guarantee rates.And the internal pressure capability after seismic loading as the seismic fragility curves was proposed,and the pressure capability fragility after far-field and near-field ground motion are built,the high confidence of low probability are obtained,the function between failure probability and experienced PGA and guarantee rate were established.