And at the moment, there's no way to stop the leak.
Japanese fishermen have had their suspicions of leaks ever since the earthquake and tsunami that triggered the Fukushima meltdown, but the power station's operator, the Tokyo Electric Power Company, and the Japanese government have been secretive about just what is happening.
So should there be concern about the radioactive water leak, just how far will it spread and what will be the effect on fish and other marine life?
Dr Ken Buesseler is a senior scientist at the Woods Hole Oceanographic Institute near Boston in the US state of Massachusetts, and he says there has been sustained release since the 2011 disaster.
Presenter: Richard Ewart
Speaker: Dr Ken Buesseler, senior scientist, Woods Hole Oceanographic Institute, Massachusetts
BUESSELER: We've been looking at Fukushima from the ocean side right, in ships we go out and sample and since 2011, we've seen the isotopes from Fukushima in the ocean, we've said there's a continued persistent leak from the site. But I do think that we have to bear in mind that the release in 2011, at the early stage of the accident was much, much larger than this continued persistent release that we've been talking about here today and that's in the news.
EWART: It does look though that two years after the event, that started this whole process rolling, that they still don't have the situation under control, they being Tokyo Electric Power Company, in particular, and obviously the Japanese government as the overriding influence there?
BUESSELER: Well, you say it's not under control and they also wouldn't admit to what was very obvious to us, to the Japanese, and several lines of evidence that the were continued sources from that site. What's also changing to is that the character of what's coming out, the different isotopes that are radioactive are shifting from being predominantly a caesium concern early on to what might be different isotopes, including strontium 90, if you know something about these isotopes, they accumulate differently in fish and in parts of our bodies, so strontium is called the bone seeking isotope, because it looks like there's calcium in the fish and in our bone, so it has a more long term affect and potentially different health affect to the caesium that's been released earlier.
EWART: What about the likely effects on marine life and fish, in particular. We're talking about the livelihoods of many people here. Is there a genuine concern that there could be a long term seriously damaging affect?
BUESSELER: Well, when you say affect, we're not talking about a direct causing cancer either in humans or fish in those waters, but a concern to our consumption of this seafood that have low levels that overtime if you kept eating levels above that, you would have concerns with your intake and therefore the health risks from eating the seafood. Now it's localised to Japan, because the source greater at the coast, the contaminated fisheries that are closed are exclusively off Fukushima. Fortunately at least for caesium, the isotope levels go down quite rapidly as the fish move across the Pacific, so we've heard of Bluefin Tuna off Santiago being contaminated, but at much, much lower levels than off Japan and therefore no longer of health concerns. So the health concerns I would have are restricted to consumers of seafood products near Japan and for that reason, they've kept those fisheries closed.
EWART: But when we talk about 300 tonnes of radioactive water pouring into the Pacific everyday. It sounds quite dramatic. But obviously we're talking about a vast expanse of water. So what happens to this radioactive water once it starts to merge with the sea water as it were. I mean is it effectively watered down, are we talking about a tiny, tiny amount here?
BUESSELER: Exactly. What happens within even a few kilometres, you get 10 or 100 times less. You go out several 100 kilometres offshore, the concentrations are lower.
We can detect very minute amounts of these isotopes. They were there before this accident, from some of the weapons testings fallout in the 60's, at very low concentration. Now we saw an elevation, particularly in March and April of 2011. This is still a lingering source I recall, but much smaller source and so it's direct contribution across the Pacific would be quite small, compared to what was released two years ago. But lingering concentrations coming into coastal waters could affect coastal Japan fisheries and different isotopes such as strontium 90 as I said before could have different uptake and longer retention in the fish.
EWART: Now famously, we've seen examples of large pieces of debris from the earthquake in Japan that have crossed the ocean and been washed up on the coast of the United States. But I would assume that the radioactive water that is getting into the ocean, by the time it reaches this side of the Pacific, the potential for damage would be very small?
BUESSELER: Yeah, much lower. The debris moves quicker than the ocean currents push the water, because they're wind blown, something like a soccer ball moves quickly across the surface, so we've seen that deris arrive. The plume, the materials, the contaminants from 2011 would be reaching the US West Coast sometime within a year, that type of time frame. But at concentrations that are probably say tens-of-thousands of times lower, slightly higher than what was there before from the 1960s fallout, again there's caesium in every ocean, in every hemisphere, there's other isotopes as well and it will go up slightly and I'll be able to measure that. But that's not going to be our concern on the US West Coast at those levels.