Japan plans to start sending seawater in an underwater tunnel built to release nuclear-contaminated water into the ocean from the Fukushima Daiichi nuclear power plant on June 12, local media reported on Friday citing news from the plant's operator, Tokyo Electric Power Company (TEPCO).

According to TEPCO, the tunnel has been filled with about 6,000 tonnes of seawater this week for a two-week test before releasing the nuclear-contaminated water from the plant to a point about one kilometer offshore.

Japan is likely to officially begin its plan to dump the nuclear-contaminated wastewater into the ocean as early as the beginning of July. So far, the implementation of Japan's plan still needs to await the outcome of the International Atomic Energy Agency's (IAEA) meeting in late June.

In spite of the damage to the marine ecology and environment, Japan unilaterally pushed forward the discharge plan and constantly made excuses for its claim that "nuclear wastewater is safe."

However, the content of Cs-137 (a radioactive element that is a common byproduct in nuclear reactors) in the marine fish caught in the harbor of the Fukushima Daiichi Nuclear Power Plant is 180 times that of the standard maximum stipulated in Japan's food safety law, according to a statement released by the Chinese embassy in Japan on Monday, referring to data from a report released by TEPCO.

It also pointed out that there are more than 60 radionuclides, including tritium, carbon-14, cobalt-60, strontium-90 and iodine-129, in the nuclear-contaminated water. Some long-lived nuclides may spread with ocean currents and result in a bioconcentration effect, which will increase the total amount of radionuclides in the environment and cause unpredictable hazards to the marine ecosystem and human health. 

Earlier, TEPCO admitted that tritium, a mildly radioactive form of hydrogen, cannot be removed from the wastewater, but insisted it is not harmful to human health, which has aroused the opposition of many experts.

"When tritium gets inside the body, it's at least as dangerous as any of the other radionuclides. And in some cases, it's more than double as dangerous in terms of the effects of the radiation on the genetic material, on the proteins," Timothy Mousseau, professor of biological sciences at the University of South Carolina, told a press conference in Seoul.

Japan insists that the purified "treated water" is no different from the normal discharged water from a nuclear power plant. 

Li Song, China's Permanent Representative to the UN and other international organizations at an IAEA board of governors meeting held on Monday in Vienna pointed out that Japan has adjusted the concept that the discharge of nuclear-contaminated wastewater from Fukushima into the sea, which is completely different from the normal operation of nuclear power plants.

"It is 'unacceptable' for Japan to push forward the discharge plan without verifying the long-term reliability of relevant technology and purification equipment in an attempt to cover up the danger," said Zhang Kejian, chairman of China Atomic Energy Authority at the meeting.

Regardless of raging opposition from home and abroad, Japan has been rushing to dump the wastewater into the ocean, which has incited protests from local civic groups as well as neighboring nations and communities within the Pacific Islands.

A spontaneous protest was held in front of the headquarters of TEPCO in Tokyo on Wednesday evening. Holding banners and flags with slogans that read "Don't discharge polluted water into the sea" and "Don't pollute the ocean for all," the protesters said that the discharge of nuclear-contaminated water in the ocean is a highly irresponsible act.

On the same day, Green Korea United, an environmental group, also staged a protest in front of the Japanese embassy in Seoul, calling the discharge an "international crime" that will transfer the risk of further pollution to the world through the seas.

Sumio Konno, former employee of the Fukushima Daiichi Nuclear Power Plant, strongly voiced his anger at the Japanese government's plan, warning of the serious economic and health implications of such a move which he said will "haunt our children's future."

"Most people are against the plan of discharging wastewater into the sea, as it will affect fisheries and agriculture. People also think that if the wastewater goes into the sea, they will never have delicious sea fish again, and the fish will have no buyers. If people suspect the fish to be poisonous, they will not want to eat them," Konno told CMG in an interview in May.

The discharge of nuclear wastewater into the ocean has raised concerns about the safety of sea products in many places.

On June 8, Hong Kong's environment chief said that Hong Kong will ban seafood from high-risk regions near Fukushima at once if Japan starts to dump nuclear-contaminated water from its crippled Fukushima Daiichi nuclear power plant into the Pacific Ocean.

Ahead of the release of the wastewater, some South Korean shoppers are buying salt and seafood in bulk to store at home and retailers are stockpiling in fear of a supply shortage. According to South Korea's Ministry of Oceans and Fisheries Sea salt prices have gone up by nearly 27 percent in the first week of June from two months ago, but the authority attributed the price increase more to bad weather and lower production in recent months than panic buying.

On March 11, 2011, a magnitude-9.0 earthquake struck off the coast of Fukushima Prefecture in Japan. An earthquake-triggered tsunami engulfed the Fukushima Daiichi nuclear power plant, causing core meltdowns in units one to three and leading to the worst nuclear crisis since Chernobyl.

In April 2021, the Japanese government announced its controversial plan to release wastewater into the Pacific Ocean, and said in January this year that the discharge will start "in the spring or summer."

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