The industry ministry said Monday it would be safe to release water contaminated by the Fukushima nuclear disaster into the ocean, stressing that on an annual basis the amount of radiation measured near the release point would be very small compared to levels to which humans are naturally exposed.
Discharging the water into the Pacific Ocean over the course of a year would amount to between just one-1,600th and one-40,000th of the radiation to which humans are naturally exposed, the Economy, Trade and Industry Ministry, or METI, told a government subcommittee on the issue.
Water used to cool the melted-down cores and groundwater from close to the damaged plant contain some radioactive materials, and are currently being collected and stored in tanks on the plant grounds.
But space is running out fast, and the government is exploring ways to deal with the waste water — which already totals more than 1 million tons with the volume increasing by more than 100 tons every day.
According to an estimate performed by the ministry, annual radiation levels near the release point after a release would be between 0.052 and 0.62 microsievert at sea, and 1.3 microsieverts in the atmosphere, compared with the 2,100 microsieverts that humans come into contact with each year in daily life.
One member of the subcommittee called on the ministry to provide detailed data showing the impact of different conditions such as ocean currents and weather.
Another member requested more information on the amount of radiation that people will be exposed to internally, depending on how much fish and seaweed they consume.
The waste water is currently being treated using an advanced liquid processing system referred to as ALPS, though the system does not remove tritium and has been found to leave small amounts of other radioactive materials.
The tanks storing the water are expected to become full by the summer of 2022, according to Tokyo Electric Power Company Holdings Inc., the operator of the Fukushima No. 1 nuclear power plant.
The plant was damaged by a magnitude 9.0 earthquake and ensuing tsunami on March 11, 2011.
While government officials stress the safety of releasing the waste water, local fishermen are opposed to discharging it into the ocean due to worries that it would cause reputational damage and impact their livelihoods.
South Korea has also expressed concern over the environmental impact.
In September, Japanese and South Korean officials traded barbs over the issue at a meeting of the International Atomic Energy Agency in Vienna.
A nuclear expert from the IAEA said in 2018 that a controlled discharge of such contaminated water “is something which is applied in many nuclear facilities, so it is not something that is new.”
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