Title : Optimization of radio-analytical method for 3H radioactive contamination in marine products
Abstract:
Recently, the interest in radioactivity has increased significantly in relation to the domestic and international issue such as discharges of radioactive waste water from the Fukushima nuclear power plant into the ocean. The Ministry of Food and Drug Safety (MFDS) has established analytical methods for 134Cs, 137Cs, 131I, 238Pu, 239Pu, 240Pu and 90Sr in order to monitor imported foods and strengthen the management of radioactivity in foods. However, the analytical method for total 3H (TFWT, HTO and OBT), one of the radioactive isotopes generated by nuclear facilities and nuclear material exposure accidents, was absent. Therefore, government ministries are extending the monitoring of radioactivity in the marine products. In this study, we tried to development an analytical method for total 3H, analysis applicable to marine products. In order to analyze 3H in the marine products, the sample was mixed with scintillation cocktail (Gold Star) in a scintillation vial after pre-treatment procedures such as homogenization, combustion, distillation (sub-boiling), and then, measured using a liquid scintillation counter (LSC) after placed in the dark and cool tray of LSC during at least 300 min. The weight of fresh sample such as flatfish, salmon, scallop and etc., homogenized was 10 g, the 3H of fresh sample was collected in the 9 mL of 0.1 MHNO₃by combustion. The combustion gases were air and oxygen, and oxygen gas was automatically supplied when the sample-zone furnace temperature reaches 500℃. The catalyst was Pt-alumina. Distillation time was over 150 min and the ratio of the sample and the scintillation cocktail was 9:11. The measuring time of LSC was over 240 min and the MDA was below 10 Bq/kg. The LSC condition for radio-analysis of 3H in the marine products were as follows; the instrument was Hidex-300SL (Oy, Finland), external standard source was EU-152, the window channel was 10-150, coincidence time was 20 ns, counting time was 3600 sec, vial repeat was 4 times.