[ RadSafe ] How many curies were involved in Hiroshima

Brennan, Mike (DOH) Mike.Brennan at DOH.WA.GOV
Mon Jun 20 11:41:05 CDT 2011

I am not sure if the question of how much radioactivity was released at
Hiroshima is a meaningful question, at least when trying to put it in
perspective with Chernobyl and Fukushima.

There are several reasons for this.  The first is that the explosion at
Hiroshima produced blast and heat that killed people (though not
everyone) out to a range past where the radiation dose would cause acute
problems.  At Chernobyl the blast killed a few people (I am not sure how
many), and at Fukushima no one was killed by blast.  

Second, at Hiroshima much of the radiation was produced by fission, so
"curies" isn't an appropriate unit, in much the same way it isn't for
machine produced radiation.  There was a substantial amount of
radioactive material produced, and there was some exposure to people
from the fallout, but that wasn't the main source of dose.  At Chernobyl
a reactor core that was (for a brief time) at more than 100% power was
blasted into the air, then roasted in a graphite fire for days.  At
Fukushima there was a release into the air some hours after criticality
ceased, and a large amount of the radioactive material has been trapped
in water that either went into the ocean or is still on site.  

Third, the isotope mix of what was released is very different between
the three.  This come into play in that the release of, say, 1,000 Ci of
I-131 has different consequences than the release of 1,000 Ci of I-129.
Weapons tend to have a higher percentage of very short half life
isotopes, reactor fuel that has been use a while has a higher percentage
of longer half-life isotopes.  Also, with reactors the amount of time
between the end of criticality and the release will impact both the
amount of activity and the isotope mix.  

I bring all this up because it is a natural tendency to ask questions
like this, then equate "more" with "worse".  In this case, I don't think
that the intentional attacks of Hiroshima and Nagasaki can be
meaningfully compared to Chernobyl and Fukushima.   

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Theo Richel
Sent: Saturday, June 18, 2011 11:17 AM
To: The International Radiation Protection (Health Physics) MailingList;
The International Radiation Protection (Health Physics) Mailing List
Subject: [ RadSafe ] How many curies were involved in Hiroshima

Could anyone please give me some facts on how much radioactivity
(curies) was released in: Fukushima, Hisoshima, Chernobyl

Much appreciated

Theo Richel
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