Readings at the plant, taken at 10.20am, varied considerably. Edano told reporters that the highest level around one of the reactors was 400 millisieverts, with a reading of 100 millisieverts around another.
We\’ve moved from microsieverts to millisieverts and yes, we are now very definitely in the range which is dangerous to human health.
One nuclear worker who has commented around here says that his annual measured dosage is around 2 millisieverts.
Four points occur to me.
1) We are assuming that the difference between micro and milli hasn\’t got garbled somewhere along the line. I wouldn\’t put much weight on this but it\’s not impossible that it has.
2) Let\’s compare it to Chernobyl. There, right by the reactor, levels were (according to WikiP) 30,000 roentgens. 3,600 sieverts. There are one thousand milli sieverts to one sievert. So we\’ve perhaps reached 400/3,600,000 or roughly 1/1o,000 th of the level of Chernobyl radiation.
3) Dosage in a particular place and time is what matters to that person in that place and time. What matters to us as a whole is total dosage released. We have no information on this at present but it would be astonishing if there was as much as 1/10,000 th of Chernobyl released.
4) Finally, it depends hugely on what it actually is producing the radiation. If it\’s the hydrogen build up, which will contain N16, then this is a problem for those actually on the site. But for anyone more than a few hundred metres away it isn\’t: half life is about 5 seconds when it turns back into O16, that thing we all breathe all the time. If it\’s Cs 137 say, (a product of the actual fission process in the rods itself) then this will be around for a lot, lot, longer. And is thus more of a danger.
If the reports are true then this is worse than I thought it could be. And if the reports are true, the amounts of radiation are larger than we can make jokes about Banana Equivalent Doses about. But even assuming the reports are true it isn\’t as bad as some will paint it.
Stick with the 1/10,000 th of a Chernobyl for a moment.
Just one accident like Chernobyl can release 35 times as much radiation in 10 days as the total radioactive emissions from coal power plants on the entire planet Earth over the course of a century. The Chernobyl accident is estimated to have released 25–50 million curies (1–2 exabecquerels) (IAEA estimations), whereas the collective radioactivity resulting from all coal burning worldwide between 1937 and 2040 is estimated to be 2,700,000 curies or 0.101 EBq).
Call that century of coal emissions 10% of a Chernobyl. We are at 1,000 th of that. Maybe 6 weeks of what coal fired plants pump out all the time.
And that is assuming that what is coming out of Fukushima is long lived radionucleides, rather than that very short lived N16 etc.
More information needed, obviously.