Concerning the apprehensions about naturally occurring radioactive materials (NORM) residues, the International Atomic Energy Agency (IAEA) and its member nations have acknowledged the imperative to ensure the radiation safety of NORM industries. Residues with elevated radioactivity concentrations are predominantly produced during NORM processing, in the form of scale and sludge, referred to as technically enhanced NORM (TENORM). Substantial quantities of TENORM residues have been released externally due to the dismantling of NORM processing factories. These residues become concentrated and fixed in scale inside scrap pipes. To assess the radioactivity of scales in pipes of various shapes, a Monte Carlo simulation was employed to determine dose rates corresponding to the action level in TENORM regulations for different pipe diameters and thicknesses. Onsite gamma spectrometry was conducted on a scrap iron pipe from the titanium dioxide manufacturing factory. The measured dose rate on the pipe enabled the estimation of NORM concentration in the pipe scale onsite. The derived action level in dose rate can be applied in the NORM regulation procedure for on-site judgments.

1. Introduction
2. Materials and Methods
    2.1 MCNP Simulation for Pipe Residues
    2.2 The LaBr3(Ce) Detector System
    2.3 Radiation Measurement of the ResidualScale of the Pipe
3. Results and Discussion
    3.1 MCNP Simulation Results
    3.2 Deriving Equivalent Dose Rate for ActionLevel
    3.3 In Situ Measurement of Pipe Scale
4. Conclusion
Conflict of Interest

• Wanook Ji(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea)
• Yoomi Choi(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea)
• Zu-Hee Woo(2Korea Institute of Nuclear Safety, 62, Gwahak-ro, Yuseong-gu, Daejeon 34142, Republic of Korea)
• Young-Yong Ji(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea) Corresponding author