Tomography for partial-defect verification : experiences from measurements using different devices

摘要: The fuel assemblies used at the Swedish nuclear power plants contain typically between 100 and 300 rods. An experimental technique has been demanded for determining relative activities of specific isotopes in individual rods without dismantling assemblies. purpose is to validate production codes, which requires an accuracy <2 % (1 σ).Therefore, a new, non-destructive tomographic measurement irradiated developed. includes two main steps: (1) gamma-ray flux distribution around assembly recorded, (2) interior source reconstructed. use detailed transport calculations reconstruction procedure enables accurate determination rod-by-rod distribution.To investigate achievable, laboratory equipment constructed, including model with well-known 137Cs. Furthermore, instrument constructed built in-pool measurements on plants.Using equipment, 1.2 was obtained σ). resulted repeatability 0.8 %, showing that can be achieved using this instrument. agreement data POLCA–7 code measured 3.1 σ).Additionally, there safeguards interest verifying no fissile material diverted from assemblies, i.e. have removed or replaced. applicability demonstrated spent assembly. detection both removal rod as well replacement non-active investigated detail quantitatively established equipment.