New articles published: V. 14 n. 4 (2026)

Comparison between NaI(Tl) and CsI(Tl) detectors in detection of flooded flexible risers using MCNP6

Abstract: Flexible risers are multilayer pipes used in offshore oil production, combining flexibility and mechanical strength through several layers of different materials. Although designed to withstand severe operating conditions, loss of watertightness may occur, allowing seawater ingress that can lead to corrosion of metallic components, degradation of thermal insulation, and mechanical failure, ultimately compromising riser integrity and operational safety. Regular inspection is therefore essential to ensure facility’s operation without riser’s repair interruption. Gamma transmission is a promising technique for this purpose. This study proposes a methodology to detect seawater ingress using two NaI(Tl) scintillation detectors and compares its performance with an array of twenty-three CsI(Tl) scintillation detectors. The results showed excellent agreement between I/I₀ and seawater ingress percentage for both detector configurations. However, NaI(Tl) detectors presented approximately 25 times higher detection efficiency, leading to improved counting statistics, shorter acquisition time, or reduced source activity, depending on operational requirements. In addition, NaI(Tl) detectors enable gamma-ray spectrometry using simpler electronic instrumentation. The results were obtained by simulations with the MCNP computer code. Read full article.