Speaker
Description
Ammonium molybdophosphate (AMP) pre-treatment is widely used for radiocesium (Cs-137) analysis in large-volume seawater samples; however, conventional manual procedures involve substantial operational challenges, including handling of bulk samples (e.g., 60 L), strong-acid dosing for pH adjustment, and potential variability in recovery during settling, supernatant decantation, and sorbent collection. These factors raise concerns regarding operator safety, reproducibility, and throughput in routine monitoring programs.
In this study, an automated AMP pre-treatment tank system was developed, integrating closed-loop acid dosing with pH control, metered AMP addition, programmable mixing and settling sequences, automated supernatant removal, sorbent/precipitate recovery, and clean-in-place (CIP) washing. The performance of the automated system was benchmarked against the conventional manual workflow in terms of (i) cesium recovery yield (radiochemical/chemical yield), (ii) total elapsed processing time, and (iii) operator hands-on time. Manual and automated procedures were each conducted in five independent runs under comparable seawater matrix conditions.
The manual procedure yielded Cs-137 recoveries ranging from 93.29% to 98.15% (mean 96.09%), whereas the automated system achieved recoveries between 88.33% and 96.96% (mean 93.85%). Although the average recovery of the automated process was slightly lower than that of the manual method, it remained within an acceptable and stable range for large-volume seawater radiocesium analysis. In contrast, significant operational benefits were observed: the total elapsed processing time was reduced from 268.5 min (manual) to 215.8 min (automated), and operator hands-on time was markedly decreased from 97.6 min to 22.8 min.
Several automation-related issues were identified, including pH sensor response delay and signal noise, partial clogging in the sorbent recovery line, and mixing motor load alarms. Mitigation strategies such as sensor redundancy, backflush sequences for recovery lines, and torque- or current-based mixing control are proposed.
Overall, the automated AMP pre-treatment workflow demonstrates its potential to maintain comparable recovery performance while substantially improving operator safety, process standardization, and analytical throughput, making it a promising approach for routine and long-term monitoring of radiocesium in large-volume seawater samples.
ACKNOWLEDGMENTS
This work was supported by the Ministry of Oceans and Fisheries (MOF) of the Republic of Korea and the Korea Institute of Marine Science & Technology Promotion (KIMST) (No. RS-2023-00240908).