Rutile-type SMAW electrodes: Quantification of NORM using CR-39 and gamma spectrometry for internal dose assessment

This study investigated the potential radiological risks associated with inhaling fumes from 10 commercial shielded metal arc welding (SMAW) electrodes by testing the hypothesis that flux composition significantly influences internal dose. Activity concentrations of 238 U, 232 Th, and 40 K were measured using high-purity germanium (HPGe) gamma spectrometry and CR-39 alpha-track detectors to establish a baseline for material-based analysis. To move beyond deterministic assumptions, workplace inhalation was evaluated through empirical air sampling yielding 4–6 mg/m 3 fume mass and a Monte Carlo simulation of 10,000 iterations to account for variable release rates and particle sizes ranging from 0.3 to 5.0 μm AMAD. Results indicated bulk flux activity ranged from 12 to 59 Bq/kg for 238 U and 23 to 45 Bq/kg for 232 Th, with a strong positive correlation (r ≈ +0.87) suggesting common geological origins in minerals such as zircon or monazite. While individual Rutile samples represented the upper bound of measured activity, analysis of variance (ANOVA) showed no significant difference between Rutile and Basic electrode group means (p > 0.05), indicating high intra-group geological variability. The probabilistic mean Annual Effective Dose (AED) was found to be 0.74 mSv/yr, which remains below the primary 20 mSv/yr occupational limit but exceeds the 0.01 mSv/yr exemption level. Furthermore, the Excess Lifetime Cancer Risk (ELCR) reached 0.88 x 10 -3 , evaluated against international benchmarks to characterize long-term stochastic effects. These findings suggest that while radiological impacts vary significantly by batch, the implementation of the ALARA principle through local exhaust ventilation and material selection remains a prudent approach to managing occupational health.