Radionuclide monitoring through 'The mussel Watch Program' concept in the East Sea of South Korea

Abstract

In 1993, a Russian white paper revealed the dumping of Soviet radioactive waste into the ocean. Liquid radioactive waste (456 TBq) and solid radioactive waste (225 TBq) were dumped into the Okhotsk Sea, from 1966 to 1991. In the wake of this incident, the necessity of systematic radioactivity monitoring of the waters around Korea was raised. China is building and operating nuclear power plants in waters adjacent to Korea and will continue to expand, increasing the possibility of radioactive contamination in waters around Korea due to nuclear accidents in neighboring countries. As large amounts of radioactive materials were released to the ocean due to the accident at the Fukushima nuclear power plant in Japan in 2011, public interest in the possibility of radioactive contamination in the surrounding waters of Korea increased. From 2023, Japan decided to release their contaminated water from the Fukushima nuclear power plant to the ocean so that releasing radionuclides to the environments would be expected to increase. A study on the radioactive contamination of the coast using mussels was proposed in 1975 by Edward Goldberg of the United States, which, with the attention of the NRC and EPA, launched the “Mussel Watch” project for mussels off the coast of the United States. Mussels are wide spread, biological availability is obtained, resistant to pollutions, easy to collect and identify, filter feeders, sessile, large population, commercial products of the sea, efficient bioconcentrate. The sampling sites were chosen on the basis of possible sources of nuclear facility and their outcomes (liquid contaminants) and along the Eastern Sea of South Korea. From the North of the Eastern Sea of South Korea, Sokcho, Pohang and Gyeonju were approximately 30 km north of Uljin, Wolsung and Kori nuclear power plant, respectively. Suyoungman and Oryukdo were approximately 30 km south of Kori and Sinkori, respectively. This study selected Ulleungdo and Dokdo as the reference sites. 134Cs and 137Cs are all showed as MDA values for all the locations. 40K showed as the highest value at the farthest south(Oryukdo), along the coasts and going upward (north), the value is getting lower. We performed ICP-MS for Oryukdo, Dokdo, Ulleungdo since Oryukdo is the first place to flow in from outside of the Korea. To compare with other countries, the magnitudes are different at least 1 to 4 orders for 238U, at least 4 to 6 orders for 232Th.