Uncertainty Analysis Of Fast Neutron Fluence In Pressurized Water Reactor

The pressure vessel of pressurized water reactor is subjected to strong neutron irradiation and embrittlement during operation,and the accumullation of long-term irradiation reduces the toughness of the pressure vessel,which seriously affects the safety of the pressurized water reactor nuclear power plant.In order to accurately evaluate the degree of embrittlement damage and life of the pressure vessel,it is necessary to simulatc and calculate the fast neutron fluence of the pressure vessel.In the shielding simulation calculation,there are many uncertainties in actual engineering,which introduce deviations into the calculation results,affecting the reliability of the simulation calculation results.Therefore,it is particularly important to quantify the uncertainty factors in a typical pressurized water reactor nuclear power plant.Aiming at the uncertainty analysis of fast neutron fluence at the irradiation surveilance capsule of a typical pressurized water reactor nuclear power plant,this paper studies and analyzes the uncertainty factors in the actual engineering and quantifies them based on the uncertainty calculation evaluation criteria,so as to provide reliable data support for the sufficient safety margin of the pressure vessel.Before the simulation calculation of the fast neutron fluence at the irradiation surveilance capsule of a typical pressurized water reactor nuclear power plant,the transport scheme should be determined,and the transport scheme should be determined by NUREG/CR-6115 international benchmark,and the stability of the transport scheme should be guaranteed,and the fast neutron fluence of a typical pressurized water reactor nuclear power plant should be simulated and calculated by this transport scheme.The uncertainty analysis of fast neutron fluence in a typical pressurized water reactor nuclear power plant includes the uncertainty of the transport scheme and the uncertainty of engineering factors.The uncertainty of the transport scheme and nuclear database is determined by comparing the experimental simulation benchmark with the commercial operation nuclear power plant benchmark.The uncertainty of engineering factors is analyzed from three aspects:geometric components,material composition and density changes in the reactor,and neutron source in the core.The uncertainty factors of the geometric components in the reactor are mainly position and size deviations,the changes of material composition and density mainly consider the difference in coolant temperature in different regions,and the core neutron source is judged according to the different fuel consumption depth,and then formulates the engineering analytical uncertainty disturbance scheme,so as to simulate and calculate the engineering analytical uncertainty.Combined with the uncertainty of the transport scheme and the uncertainty of engineering factors,the uncertainty of the fast neutron fluence of a typical pressurized water reactor nuclear power plant is obtained.In this work,the NUREG/CR-6115 international benchmark was used to determine the transport scheme,and the errors were all within 1%through the verification and analysis of the transport parameter errors,indicating the stability and reliability of the transport scheme.Based on this scheme,the fast neutron fluence at the irradiation surveilance capsule of a typical pressurized water reactor nuclear power plant is simulated and calculated,and the relative deviation between the calculation result and the experimental value is about 10%.The uncertainty of the transport scheme was determined by PCA experimental simulations and H.B.Robinson-2 commercial nuclear power plant to be ±6.4%.According to the uncertainty disturbance value,the uncertainty of engineering factors obtained by the simulation calculation is ± 10.56%,and the total uncertainty is ± 12.35%,which meets the relevant standards of engineering applications.The quantitative analysis of uncertainty provides reliable data support for the safety margin of the pressure vessel,which has important safety and economic significance for the pressurized water reactor nuclear power plants.