On 30/08/2012 18:35, harry wrote:
On Aug 30, 9:07 am, Martin Brown
wrote:
On 30/08/2012 08:33, dennis@home wrote:

"harry" wrote in message
...

If it was as safe as you seem to think, the could have stayed at home.

That is the whole point, they could have stayed at home.

Some of them anyway. But the authorities didn't know that at the time.

I don't think the zone at 400mSv and above would be good to live in and
I would not be thrilled to live with more than 100mSv per year
(equivalent to 100 years industrial nuclear worker permitted dose if
memory serves, or 50 years spent as long haul flight crew).

Some areas needed to be evacuated and some were not evacuated in a
timely fashion so that hot rain fell on them. It wasn't all that hot in
the general scheme of things but it was a lot more than civilians are
supposed to be exposed to routinely. Therein lies the problem.

The difficulty is with hot airborne particles that can get into the
lungs. You can survive a lot better with filtered air. Blocking
radioactive iodine uptake in people is also important early on.

The authorities chose to move people away because they were unsure what
would happen next and whether a major containment breach with massive
releases of radiation was in progress. They were in a no win situation.

So the "authorities" were unsure yet wehave all these experts here
think you could have a picnic right next door?

The problem during the emergency was that with very limited data early
on they had no idea how bad it was going to get and with exposed fuel
getting mad hot it looked like it was possibly going to get a lot worse
and quickly. An impression that was amplified when the two hydrogen
explosions occurred causing further problems on site.

We have the advantage of 20:20 hindsight now and accurate maps of the
actual dose rate. They chose to evacuate everywhere that had above 20mSv
or 3x typical annual exposure. They could probably have gone higher but
would have had to convince a sceptical and worried public.

Given the logistical problems 100mSv was probably a more rational choice
of threshold for evacuating completely. Initially they didn't know where
was hot and where was not - rain plays a part in this.

So you are saying things could have been a lot worse?

http://www.nytimes.com/interactive/2...ia/Conditions-
at-Fukushima-Plant-Improve-But-Return-Home-Will-Take-Years.html

Probably not all that much worse although they didn't have as much by
way of fully exposed burning core and fuel rods unlike Chernobyl.

The point about evacuation is that you need to do it before there is
significant radiation about otherwise you can end up spreading hot
particles around the country. Once the contaminated zone is defined
stuff that is used there stays inside unless it is carefully
decontaminated to avoid spreading radioactivity elsewhere.

It is ironic that the stress of evacuation and living in shelters has
probably killed many more people already than the radiation exposure.

You also seem to have forgotten that they were dealing simultaneously
with the aftermath of a very powerful earthquake that had trashed a lot
of other infrastructure so nothing was straight forward.

--
Regards,
Martin Brown