Some cliff notes for those wondering what the fuss is about:

• In 2011, three nuclear reactors in Fukushima went into meltdown and released radioactive contamination into the environment, including oceanwater
• The facilities remain flooded with a volume of contaminated water that has been described as "500 Olympic-sized pools"
• As part of the ongoing effort to clean up Fukushima, Japan wants to eventually remove all of the remaining contaminated water
• Japan's plan to do this involves reducing the radioactivity of the water using a filtration process known as ALPS while staging out water releases over a period of 30 years
• The main remaining contaminant in the water following ALPS filtration is expected to be Tritium, which samples show as existing within the threshold that is considered safe for human consumption.
• This plan was approved by the UN after determining that the radiological impact would be "negligible"
• China and South Korea both oppose the plan. Wang Wenbin, a spokesman for the the Chinese Foreign Ministry was quoted calling the plan "extremely selfish and irresponsible" and stated that "The ocean is humanity's common good, not Japan's private sewer"
• Concerns over Tritium release have been criticized, as other active reactors in the region are known to release similar levels of the substance into the ocean (e.g.: those at the Yangjiang nuclear plant), though it is also worth noting that this criticism hinges upon the assumption that the ALPS filtration process will be as reliable as early results suggest. It requires trusting that Japan will be completely diligent in overseeing their filtration efforts so that radioactive Cesium is not released into oceanwater.