Portable gamma-ray instrumentation for inspecting pipe wall thickness: Monte Carlo and experimental investigations

Abstract

This study aims to assess the efficacy of low energy gamma-ray based instrumentation for inspecting the wall thickness of metallic pipes in industrial situations. The primary motivation behind this work is to explore the feasibility of using a Monte Carlo approach, specifically FLUKA simulations, for radiation-based industrial applications. To achieve this objective, laboratory experiments and FLUKA simulations were conducted using 59.5 keV gamma-rays and a NaI(Tl) scintillation detector. The purpose was to detect changes in pipe wall thickness due to erosion and corrosion, enabling timely intervention to prevent any negative consequences. The ability, scoring commands and geometry design of the FLUKA Monte Carlo code were validated in this study by comparing the computed values of gamma-ray scattered/transmitted intensity with experimental data. Regression lines were derived from the computed and experimental data for scattered and transmitted intensity, providing valuable information for pipe wall inspection. The technique exhibited high sensitivity to changes in the wall thickness of metallic pipes, with a detection capability of 1 mm. However, for higher wall thickness, the sensitivity of the low-energy gamma-ray technique decreased due to the influence of overlying scattering/absorption components in the obtained spectra. The maximum sensitivity limit was found to be for a wall thickness of ∼8 mm for metallic pipes. The excellent agreement between simulation results and actual laboratory methods validates FLUKA's high efficacy in checking the condition of industrial pipelines.