Research On Aerosol Movement And Deposition Character Of AP1000 Under Severe Accidents

Pressurized water reactor nuclear power plant may produce a large number of aerosol and release into the containment under the severe accident.The radioactive aerosol will do great harm to the staff,the public and the environment.AP1000 is the key three generations of nuclear power technology to develop and construct in a future period time in China.Thus to study the movement and deposition characteristics of aerosol in the AP1000 containment under severe accident will help to remove the aerosol and provide advanced reference for the system design and optimization of passive nuclear power pressurized water reactor.The relationship between aerosol deposition and gas temperature and pressure、relative humidity、gas and aerosol properties in AP1000 when severe accidents happen are analyzed using CFX software by setting different working conditions.The results showed that:(1)Under different working conditions,the overall aerosol velocity trace distribution are similar.There will be four symmetrical vortexes in the up and down head of the containment,and the maximum velocity also appears at the vortex in up and down head,but with different temperature and pressure,the size and shape of the trace and the maximum velocity are different,the greater the pressure and temperature,the greater the spiral bending degree and the maximum velocity.(2)Aerosol concentration distribution in vertical plane is generally similar,from low to high concentration distribution is high in the low head,the up-head aerosol concentration is low.The concentration distribution is high on both sides of edge location,and is low near the center in the horizontal plane.But with the increase of temperature and pressure,the concentration of the aerosol deposition quantity increases gradually.(3)The concentration distribution is high on both sides of edge location,and is low near the center in the horizontal plane.But with the increase of temperature and pressure,the concentration of the aerosol deposition quantity increases gradually.(4)Under different humidity conditions,the velocity trace of different kinds of aerosol are similar with the dry air condition.But with different humidity,the shape of the trace and the maximum velocity are different.the bigger the humidity is,the bigger the spiral bending is.The shape of the velocity is like M type.But the greater the humidity is,the smaller the maximum velocity is and the greater of the aerosol deposition.(5)Under same working condition,the overall velocity trace distribution of different aerosols are similar.but with different aerosol,the concentration of the aerosol of I2 is the biggest,and the UO2 is the smallest.(6)The shape of the trace and the maximum velocity are different.the bigger the humidity is,the bigger the spiral bending is.The shape of the velocity is like M type.But the aerosol with 9um size,has the smallest velocity and concentration,and the aerosol with 2um size,has the largest velocity and concentration.Through the study it was found above,the movement and deposition mechanism changing with conditions 、aerosol material and size in severe accident in AP1000 nuclear power station is got.The greater the temperature and pressure of air space,the greater the deposition concentration of aerosol;the aerosol deposition concentration will be affected by aerosol types under the same conditions;when the humidity of the air space is larger,aerosol deposition concentration will be larger than that of the same working condition of dry air.The greater the temperature and pressure of air,the natural cycle and heat transfer between the internal fluid and cold wall is larger,temperature and pressure increase heat swimming and turbulent deposition,the thermophoresis and turbulence deposition will increase due to temperature and pressure increasing,and the greater the humidity is,the greater the viscosity of fluid is,leading to the greater the velocity of aerosol,and the larger the concentration deposition of the aerosol.Different aerosol particle size,will affect the Kn number,which is an important factor of influencing thermophoresis deposition.The smaller the particle size is,the greater the Kn number is,and the smaller the thermophoresis deposition concentration is.