It is proving hard to get Japan out of my mind. The continual drip, drip of ever worsening news about the Fukushima nuclear plant has somehow overwhelmed the continuing awfulness of the consequences of the natural disaster itself. I guess the tangible disaster, vast though it is, is somehow more determinable than the unseen, unknown quantity of danger residing in the reactors, or outside them, in Fukushima.

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For whilst heroic Japanese rescue teams busy themselves with retrieval, rehabilitation and reconstruction in the stricken tsunami areas, the news out of the plant talks to us in terms we have never been asked to comprehend before. Suddenly we are confronted by ‘millisieverts’ (mSv).

At times we are told that whatever is happening is only inflicting some small proportion of what we are bombarded with when be undergo an X-ray. Then at other times we are informed that the entire plant has had to be evacuated because of the state of immediate radioactive fall out. Yesterday we were given a figure of “ten million times what is safe”. Then we were told that that figure was “untenable” and that a new reading would be taken.

In amongst the state of the sea, the drinking water, the air, and Japanese travellers to China (hospitalised in some cases), we are told dollops of physical detail about the plant.

It seems today that although a mains cable has been re-connected to the critical cooling systems, in reactors 2 and 3, this has never reactivated the actual cooling system. Then we are told that there is highly radio active water lying on the floors of the reactors. We are now told that this may have something to do with broken fuel rods.

Oh, and for good measure, we are told that the radioactive iodine in sea water off the coast of Fukushima has reached the wonderfully precise level of 1,850 times the legally permissible level. Then again the legally permissible levels may be so low, that even 1,850 times that level is still very low.

Read more in the Channel 4 News Special Report on Japan

The problem is that we don’t really know. And now many are beginning to wonder whether “they” know. We keep being brought back to Chernobyl. But my tangible memory of Chernobyl, as a reporter, is that sheep meat in parts of Wales and Cumbria, at one stage, became too contaminated to be consumed.

So what becomes of a big, and presumably continuing, dumping of radioactive material in sea water off Japan. When will it pitch up off Cornwall? Never? Do we know? Will it cause cancers? Will it kill eventually? These days we are told Chernobyl actually killed relatively few people. It deformed some babies, cancer rates increased, but somehow precision in the world’s worst nuclear accident, even after all these years, eludes us.

Read more: how will Fukushima crisis hit nuclear power?

George Monbiot argued in the Guardian on Saturday that the damage from nuclear was still massively outweighed by the damage we are anyway doing daily to the global climate system, merely living on the planet in the way that we do.

Many will be prepared to contemplate the idea that he may be right. Even so, the continuing problem of Fukushima seems to be that it is telling us that “they”, the authorities, do not actually have a clue what is going on. As a consequence “they” cannot possibly be able to quantify what the fall-out from it all will be and how it will be expressed.

I’m afraid I must resort to our old friend Donald Rumsfeld once again. We are in the zone of the “unknown unknowns”. And until “they” can returns us to the realm of the “knowns” we are bound to continue mistrusting “them”, and worrying about “it” – the nuclear.