| The Control rod drive mechanism(CRDM)is an essential part of the nuclear control and safety protection system of the third-generation pressurized water reactor.CRDM makes the control rod lift,drop,hold or fast insert according to the operator’s instructions by driving the linear movement of control rod.Then the start-up,shutdown and power regulation of the reactor can be realized.In order to develop a new type of control rod drive mechanism based on the third-generation nuclear technology,it is necessary to decompose the existing drive mechanism comprehensively and systematically,clarify the structure composition,stress status,motion attribute and other information,and deduce the possible failure mode and further optimization direction.At present,the research on CRDM only stays at the system level,lacking of effective hierarchical decomposition.In the study of force,researchers often focus on the properties of single force and ignore the unified study of the whole force.In the field of fluid and dynamic simulation of CRDM,the existing methods select a single time point,which can not well cover all the motion process.In terms of fault analysis and structure optimization,the current mainstream method is through physical test and experience judgment,which is lack of a set of systematic methods and processes,and needs to spend a lot of time and cost.Therefore,decomposing the system structure,considering the overall situation of the movement,and establishing a standardized process are important research contents in the development process of CRDM.Aiming at the problems of simulation analysis,fault diagnosis and structure optimization of the new control rod drive mechanism in the development process,the following four aspects of research work are carried out in this paper:(1)Taking CRDM of the third-generation magnetic-lifting nuclear power as the object,this paper analyzes the cooperation form and movement steps of various parts when it realizes the function of reactive power regulation and emergency shutdown.Based on the FMA structural decomposition theory,the three-level structure of the driving mechanism in function-motion-action is decomposed,and 6 groups of independent meta-action units are obtained.(2)Based on the geometric structure of CRDM in the third-generation magneticlifting nuclear power,the fluid simulation model and simulation calculation process of CRDM are established.Taking the flow field state at the key moments of the different meta-action units of CRDM as the research object,the conventional method and the dynamic mesh method are used in the Fluent software to simulate and analyze,and the corresponding fluid resistance and fluid flow conditions are obtained.The differences between the two methods are analyzed,and specific using suggestions are given.(3)Based on the geometric structure of CRDM in the third-generation magneticlifting nuclear power,the dynamic simulation model and simulation calculation process of CRDM are established.The dynamic simulation of the different motion processes of the CRDM are carried out in Adams software,and the corresponding motion data are obtained.Based on the meta-action,the failure mode of the CRDM during the movement process and the failure impact are analyzed,the cause and location of the failure are summarized,and the components that play a key role in the failure are determined.(4)An optimization design method for latch is proposed.By analyzing the design variables of the latch and the force of the movement process,the factors affecting its life are explored,and the life optimization goal is established.The optimization variables are screened out by the pre-experimental design,and the approximate model of the latch life was built through the second experimental design.The multi-objective optimization algorithm is used to optimize the model and form the best design scheme of the latch.Finally,by analyzing the sensitivity of the main variables to the optimization goal,the design guidance for the next generation of new latch is obtained. |
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