Application Of Neutron Injection Rate Detector For AP1000 Nuclear Power Station

With the development of nuclear technology,the safety is the deepest concern of nuclear power.Nuclear power plant AP1000 is the 3^rd nuclear technology optimized and improved on the basis of AP600 by American company Westinghouse,and also the largest energy project of cooperation between America and China.The safety and construction schedule of AP1000 are greatly improved by utilizing design concept of passive and modular construction.And the design philosophy of simplification contracted the nuclear island,like the quantities of both valves and pipes are largely reduced than those of 2^nd generation nuclear power plant.Reactor core power distribution and power output are two significant performance parameters and indexes.Reactor core power must be continuously monitored during the process of fuel loading,start,shut-down and power operation,to guarantee the reactor is in normal,controllable and safe operation.Neutron flux detector is the exact instrument to implement the function of monitoring the reactor core power,providing and transporting signals,directly proportional to neutron flux rate,to nuclear monitoring system,rod position system and safety protection system to achieve the real time monitoring on core operation and play a role of protection.When the normal condition is drifted off,measures of shut-down or special actuation will be used to ensure the safety of reactor.Therefore,correct and real-time monitoring on reactor core power distribution is very important.Neutron detector is a ideal instrument to achieve the above function.This paper introduced the integrated structure of ex-core nuclear measuring system of AP1000 nuclear power plant,analyzed and summarized the operating principle and type selection of neutron flux detector by gathering information and data,and described the signal processing,control and motion of neutron flux detector.By comparison of neutron detectors of AP1000 nuclear power plant and 2^nd plus generation nuclear power plant,the differences of the two plants and the room for improvement have been got,which provides theoretical basis and practical experience for type selection of neutron detector in follow-up projects.In addition,the installation plan of AP1000 outer core nuclear measuring system has been developed and applied in the construction of project.During the installation process,the cables in electrical conduits shall be adjusted in line with the positions of meters.The glass fiber sheath is easily be damaged as the cables may touch the sharp objects on ground grating plate or metal burrs in electrical conduit during the installation process.The damaged sheath will degrade the insulation and then disqualify the subsequent test.The troubleshooting requires removing instruments,taking out the cables or even consuming NIS cable seal connectors which are very expensive and with long procurement cycle.All of these measures will seriously impact the construction period.In order to avoid the occurrence of above situation,a special installation plan and method are set out,and special cable protection tools are developed.In addition,cable connectors are also covered and protected to avoid the damage during unfolding,pulling and adjusting process.The installation experience is also summarized and fed back,achieving one-time success for cable termination with high difficulties and improving the one-time success rate of product installation.Meanwhile,the probability of scrap during installation is greatly reduced,which decreased the production cost and raised the efficiency.