The plan to dump radioactive wastewater from the ruins of the Fukushima Nuclear Power Plant into the ocean is looking more likely than ever after receiving a preliminary thumbs up from Japan’s nuclear regulator.

The proposal to release the treated wastewater from the nuclear plant into the Pacific, passed as a bill by the Japanese Cabinet in August last year, took another big step forward on Wednesday following a decision by Japan’s Nuclear Regulation Authority (NRA) to allow a one-month public comment period on the plan. The NRA will give the official approval of the plan to go ahead next year after the public comment period finishes on June 18.

If it does receive the final green light, which many are expecting it to, the power plant operator TEPCO hopes to start releasing the irradiated water from the site after treatment into the ocean starting around spring 2023. 

It has been over 11 years since the Fukushima nuclear disaster struck on March 11, 2011, in what became one of the worst nuclear accidents in history. It started when a magnitude 9.0 earthquake triggered a devastating tsunami that slammed into the east coast of Japan. The tsunami waves crashed into the Fukushima Daiichi nuclear power plant, cutting off power to three reactor cores. Without power to the coolers, the three cores went into meltdown, sending significant amounts of radiation into the surrounding environment.

Among the many troubles left behind by the disaster, TEPCO has been lumbered with hundreds of tanks containing over 1.25 million tons of contaminated water used to cool the reactors during the incident. 

The plan to discharge the contaminated water into the sea has proved controversial with both local people and some parts of the international community, raising fears about the impact it may have on ecosystems and human health. 

However, a number of reviews and studies have suggested that the plan is safe. The International Atomic Energy Agency looked into the proposal earlier this year and concluded in April that Japan has made good progress with its planned water discharge, but it still wanted to see more information before it’s implemented.

The contaminated water is treated to remove the vast majority of radioactive elements, leaving behind tritium, one of the two radioactive versions of hydrogen. While tritium is toxic, it is naturally occurring and experts say that the amount in the environment will be negligible when diluted across the entire ocean. It’s only considered one of the least harmful radionuclides; it’s so harmless, in fact, it's the stuff that is put on wristwatches so they glow in the dark. 

A paper earlier this year modeling how the radioactive water would diffuse across the world's oceans found that the pollutants will cover almost the whole North Pacific region after around 1,200 days, reaching as far as the coast of North America to the east and Australia to the south. By day 3,600, the pollutants will cover almost the entire Pacific Ocean. It's thought the tritium will be traceable in the ocean for up to 40 years, but will be extremely diluted amid the vast Pacific Ocean.