Since the serious accident at the Fukushima Daiichi nuclear power plant in March 2011, large quantities of highly contaminated water have been generated every day as a result of the use of water to cool down the core of the meltdown reactor and the flow of rainwater and groundwater, etc. In April 2011, the operator of the plant, Tokyo Electric Power Company (TEPCO), intentionally discharged the contaminated water into the sea, which aroused a great deal of concern and worry in the community. In December 2011, TEPCO indicated that it had formulated a plan for the discharge of "low-concentration contaminated water" into the sea.
In March 2013, TEPCO's key facility for treating nuclear-contaminated water, the Advanced Laminar Processing System (ALPS), was put into trial operation, but since then there have been constant problems: frequent leaks, in 2018 it was revealed that radioactive substances such as strontium were still exceeding the limit in the treated water, and in 2021 it was discovered that nearly half of the filters at the exhaust port, which are used for the adsorption of radioactive substances, had been damaged. ......