In March 2011, a powerful earthquake off the eastern coast of Japan triggered a tsunami which hit the
Fukushima Daiichi nuclear power plant.
The 14-metre-high waves surged over the fences and knocked out
cooling systems, causing three of its reactors to go into meltdown.
Today, the plant is surrounded by
huge tanks containing over a million tonnes of water used to cool the melting reactor cores.
But the plant's owners are warning that they will run out of space to store them by 2022.
So with time running out, what do you do with all this radioactive wastewater?
We recognise that bringing the contaminated water under control is the most urgent and
a serious problem.
So what's in the Fukushima water that actually makes it dangerous?
According to the Japanese government, there are 62 radioactive isotopes in the water, including carbon-14, which is
used for radiocarbon dating but is also dangerous if ingested and can concentrate in the food chain.
Caesium-137, which causes soft tissue cancer, strontium-90 which causes bone cancer and leukaemia,
and then there's Tritium.
They can get rid of the vast, vast majority of these other elements,
but Tritium, chemically, it's really difficult to separate from water.
And because it's so difficult, Tritium will be left in the water even after the decontamination process,
which gets rid of almost everything else.
And this gets to the heart of the controversy
because the plan is to release this water into the Pacific Ocean which has provoked outrage,
not only in Japan but also in neighbouring countries and with environmental groups around the world.
So how much of a problem is Tritium if it's dumped into the ocean?
Tritium is actually considered to be one of the least harmful radionuclides occurring naturally
in water and air and it's also commonly found in the body.
High doses however do pose a risk.
So the plan put forward by the plant owners and agreed by the Japanese government,
is to dilute Tritium in the water to a radioactivity level below that of drinking water.
But how much is that in practice?
The dose to the consumers who are at most at risk would be about
one microsievert per year.
A microsievert is a way to measure the effect of low level radiation on the human body.
Just to put that in context, some medical diagnostic procedures, like,
a whole body CT scan, would give you about 10,000 microsieverts.
Annually, in the UK, we get about 2, 200 microsieverts of radiation every year.
So the sort of releases we're talking about, radiation doses in the sort of microsievert range
which is radiologically, I would call that insignificant.
This is a commonly held view among scientists but this doesn't do much to reassure the local fishing industry.
It still hasn't recovered from the disaster and sees this as another body blow.
The fishermen know that the perception of the danger of their fish could really significantly
damage their industry and I totally understand that.
For example, in the Fukushima area sales of rice,
which were below the Japanese regulatory limit, still got a value of about 20% less than the market value
because of this perceived risk.
So how do you sell the idea of dumping a million tonnes of even
very mildly radioactive water into the ocean?
You create a mascot.
This is little Mr Tritium.
He was designed to show the Japanese public just how safe Fukushima wastewater is.
He swims peacefully with the other fish, he laughs about in your plumbing and he's so safe you can
even drink him without harm.
Perhaps, unsurprisingly, the public backlash caused him to be retired a day
after appearing on the reconstruction agency's website.
It's really hard to build trust
in these situations and we saw the same after Chernobyl and Fukushima.
Communication of the risk has been really difficult
and the politics kind of takes over.
No matter how safe the process actually is,
it might not count for much in terms of public trust, which is a real problem for the Japanese government,
considering the greatest challenge is yet to come:
how to contain and safely dispose
of the highly radioactive nuclear material from the melted cores of the three reactors.
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