Research on Passive Gamma Emission Tomography Method for Corrosion Detection of Liquid Lead-Bismuth Coolant

摘要: Lead-cooled fast reactors are considered the next generation of nuclear reactors. One of the main challenges in developing lead-based fast reactors is the corrosion of structural materials by the liquid lead-bismuth coolant, as well as the formation of oxide particulates.It is an urgent need to develep a high-resolution non-destructive testing method for the detection of oxides and corrosion in pipeline of liquid lead-bismuth coolant. This paper investigates the feasibility of passive gamma emission tomography (PGET), a technique that utilizes gamma rays emitted by the lead-bismuth coolant, which is activated by neutrons in the reactor core, to inspect the lead-bismuth coolant pipelines corrosion. A simulation model of the PGET system was developed, including the test pipeline, collimator, and detector array. Projection data were obtained using the Geant4 Monte Carlo method. Image reconstruction was performed using the Algebraic Reconstruction Technique (ART), Maximum-Likelihood Expectation-Maximization (MLEM), and Ordered-Subsets Expectation-Maximization (OSEM), and an edge extraction method is proposed. With a collimator length of 90 mm and hole diameter of 1.1 mm, the reconstructed images achieved a resolution of 1.5 mm.