Development And Application Of Passive Gamma Scanning Equipment For Nuclear Fuel Element

Passive gamma scan is a kind of non-destructive testing method,gamma rays radiated by fuel assemblies are used to reflect fuel assemblies condition but needn't additional radioactive source.It could ensure the manufacture efficiency and effective reduce cost of production.The thesis takes nuclear fuel element as research object,and develops the passive gamma scanning equipment based on nuclear fuel assemblies'automated production.The thesis also makes overall evaluation for inspection system's detectability and application.This paper studies main contents including as follows:According to the characteristics of the nuclear fuel element automatic production line,passive gamma scanning online detection process are analyzed,and presented the source type overall design scheme of gamma scanningequipment.For the counts influenced by aged pellets during scanning,use the proportional characters of 234Paamplitude and counts,subtractbackground counts from total counts in low energy,and correct the effect of 234Pa on 235U scan.About the problem of enrichment measured value smaller than nominal value in annular pellets,a kind of compensation method is provided and used in annular zones measuring.For pellet stack length measurement,it set a new unit about length corresponding paths by standard rod,and calculates pellet stack length according the unit.Modularity designs are used to mechanical structure of passive gamma scanner.According to equipment movement procedure,automation and control system are designed.According to passive gamma scan characters,special standard rods are developed and used to establish calibration methods for different inspection items.This paper performs evaluation for mean enrichment,off-spec pellet and pellet stack length based on 95×95,90×90confidence levelstatistical methods.At the same time,set the reject limits of each inspection item.