Deposition Of Corrosion Products In Primary Coolant Of Nuclear Power Plant On Pipeline

The chemical source term control in the main loop of PWR is an important part of the reactor source term control when the reactor is shut down.The activation of corrosion products causes more than 90% of the reactor radiation when the fuel cladding is not damaged.The operating experience of many nuclear power plants in the world shows that the poor hydrochemical environment is the main factor leading to the increase of the intensity of the radiation field outside the reactor.Therefore,this paper conducts theoretical and experimental research on the deposition problem of the main loop cooling system pipes,and comprehensively analyzes the characteristics of the activation corrosion products of the source term and the optimal hydrochemical environment.First of all,the characteristics of the main loop of the nuclear power plant pipe sediment content of numerical calculation,characteristics of the pipeline are straight,bend(on the bay,level,under the curved),cut-off valve,pipe,conditions for different pipe diameter,pressure,flow rate,the results of numerical analysis it is concluded that the fluid dynamics of each pipeline deposition mechanism,deposition of each pipe hot spots,In the same working condition,the sediment content of the elbow was the largest,concentrated in the center of the inner and outer wall of the elbow,which laid a theoretical basis for the subsequent elbow experiments.Secondly,according to the main operation facilities and their locations of pressurized water reactor nuclear power plant,an experimental platform for the deposition characteristics of activated corrosion products was built.The variation of the deposition characteristics of activated corrosion products with axial and circumferential angles was tested by using a 90° horizontal bend pipe,and the deposition experiments for 7,14,20,26 and 30 hours were carried out.XPS and ICP were used to detect the deposition behavior of particles on the horizontal elbow,and the deposition situation at different axial and circumferential angles was quantitatively analyzed.The results show that the deposition is the most serious in the region with axial Angle of 30°～75° and circumferential Angle of 15°～345°,and the deposition rule of each particle is different with time,which is consistent with the simulation results.Furthermore,in order to reduce the deposition content of pipelines,this paper improved the experimental platform and carried out experiments in view of the changes in the water chemical environment in the cooling system pipelines,mainly the changes in p H.The 90° bend pipe was still taken as the experimental object to study the deposition characteristics of corrosion products on the pipe wall under the condition of liquid-solid two-phase flow.According to the quantitative analysis of XPS and ICP,the p H of the lowest deposition amount of each element was obtained under the condition of experiment 4: first,boron and lithium bed experiment for 16.5h and then boron bed experiment,with an initial input of 0.6mg /kg Li OH.Finally,this paper has been improved a good activation corrosion products of the sedimentary characteristics of different content of hydrogen peroxide test bench of particle deposition in acidic and alkaline environment characteristic experiment,experiment of different working conditions are 38 h,and by XPS,ICP detection and quantitative analysis,it is concluded that the minimum deposit amount of hydrogen peroxide working condition for experiment.Boron,lithium bed,The initial input was0.6 mg/kg Li OH and 30 ml hydrogen peroxide was added.