The Study For¹⁸F Dust Transport Characteristic In Reactor Body And Control Rods’ Drive Mechanism Leakage Monitoring System Sampling Tube Of PWR

The primary loop pressure boundary of Nuclear Power Plant contains high temperature, high pressure and strongly radioactive coolant water. Due to the effect of mechanical wear and chemical corrosion, the pressure boundary of primary loop reactor body and control rod drive mechanism will leak, once the leakage occurred, radioactive water primary loop will leak into the containment, causing radiant pollution, at the same time this can bring about water loss accident of reactor core and affect the safe working of nuclear power plant, so the leakage monitoring is very important about the reactor primary loop pressure boundary.18F is one nuclide of β+decay, which is generated by nuclear reactions in the primary circuit water, they are in the high concentrations, its half-life is as long as109.7minutes,18F leaks with the coolant water,then adsorbed by dust in the containment and change into18F dust.making this nuclide as tracer.We can get the primary circuit pressure boundary leakage rate by measuring the18F radioactivity in the containment, which is the new technology and new methods of monitoring circuit pressure boundary leakage rate,it is also a new trend of the primary circuit pressure boundary leakage monitoring technology.We can calculate the transmission efficiency of18F dust from its settlement characteristic,and transmission efficiency is very important to source term,and thus it provides a theoretical basis for the development of the Nuclear Power Plant online leakage monitoring device. So the study of18F dust transport characteristic essential.In view of the frequency of nuclear leakage accident, the development of18F monitoring device is imperative.The article first introduces four of the primary circuit pressure boundary leakage monitoring methods,this paper first overviews now gas-particle multiphase flow research status in quo and research methods.This paper select the appropriate model in accordance with the actual situation of the Nuclear Power Plant,after the analysis of gas flow characteristic,the RSM model is selected.After the analysis of the forces acted on the particles posed by the gas flow,and the order comparison between those forces,combining the newly research results,some forces such as Magnus force are neglected.The particle motion equation is established.In the discrete process the mostly used method,the control volume method and QUICK format are used.In the study of gas-particle flow numerical simulation,the SIMPLE arithmetic is often adopted,select Standard algorithm as pressure process.Under these conditions,this paper simulate and analysis the velocity distribution of gas using CFD in2D and3D sampling tube,making calculation and analysis with movement locus,speed change and sedimentation characteristics in the same sampling flow rate of different particle size.This article selects three kinds inlet velocity and five particle diameter according to the scope of the sampling flow.Under the same inlet velocity,18F dust’s settlement trend is not obvious and highly transmission efficiency when its diameter is0.1μm to5μm,as the particle size increased dust deposition trend become clear.18F dust’s settlement trend is obvious and low transmission efficiency when its diameter is5μm to20μm.In addition,under the same particle diameter,18F dust’s settlement trend is obvious and low transmission efficiency when its inlet velocity decreases.Ultimately,we can get fitting equation under different initial speed transmission efficiency about dust particle size.