Research and Application of Neutron Moderation Technology in Nuclear Instrumentation System of NPP

The neutron moderation technology of nuclear instrument system (RPN) in nuclear power plant is researched. By analyzing the detection mechanism, neutron spectrum, measurement requirements, layout requirements and so on, the detector moderating mechanism, the structure, the material, the thickness and the length of moderator are systematically researched, and the moderating verification method is formed. The neutron source experiment is performed by establishing moderator verification platform, indicating that the detection efficiency and output of detector has been significantly improved after adding moderator. Combined with the experiment verification, a moderator application scheme for an advanced reactor detector assemblies has been researched and realized independently. The moderator application scheme can meet the measurement and layout requirements of detector assemblies, and it has been applied to an advanced third-generation pressurized water reactor in China, and the research results have certain reference value for the research and design improvement of other reactors.