Experimental Research And Numerical Simulation Of Depositional Mechanism Of Particle-like Corrosion Products In Primary Loop

In the long term operation of the nuclear power plant system, particle-like corrosion products released from reactor structural materials, such as Inconel and stainless steel, are deposited on the surfaces of both the pipes and the primary reactor system. The pHenomenon of such corrosion products are mainly deposited in steam generator, provide it with the additional deposit surface. The corrosion product’s deposit surface not only increase the deposition rate of such corrosion products but also more easily absorb more Co-60for its porous structure.The thickness of the corrosion products could decrease the steam generator heat transfer efficiency with increasing coolant flow resistance and the risk of local stress corrosion. All those factors above caused by deposition have negative implications on the operation of steam generator.In this paper,the characters of deposition and transportation of particle-like corrosion products are analyzed based on the variations of the pH, particle size and curvature radius,as follows:Firstly, we was conducted the experiment research that use0.1mol/L LiOH to adjust pH value of re-circulating water. It is found that the value around pH=8.2of water could realize the maximum deposition and particle diameter equal to5μm is the most easily deposited on the surface of the segment tube, other things being equal.Secondly, for any tubes, section7of those tubes is the location where deposition is the maximum,corresponding to the deflection angleθ=101°～136°. If we neglect some secondary force exerted upon on the particle concerned, this deposition tendency is a universal significance.Thirdly, by comparing tubes with different bend radius, the deposition law shows that the deposition amount at upward section of bended segment is greater than the downward section one. This deposition phenomenon could be accounted for the fact that energy attenuation in the process of particle-wall collision.Fourth, based on the energy attenuation in the process of particle-wall collision, a new physical model about particle deposition was proposed to predict the deposition on the inner surface of heat transfer tube. The model differential equations was made discrete and then written using C program language and compiled into FLUENT software.Finally, in this paper, three different turbulent models with different wall functions were adopted to ensure the most appropriate model for the numerical solution.The model RNG k-s with enhanced wall treatment were used considering the computing cost and precision. Through the research at the fully developed inlet condition, we can get the following main conclusions:1). In the interval [Z/D>-3.5,θ<22.5°] and [θ>157.5°,Z/D<3.5], the results shows that there is a nonlinear relationship between deflection and pressure coefficient;2.In the interval θ=[22.5°～157.5°],on the contrary,there is a linear relationship between deflection and pressure coefficient.