Re: Tokaimura doses

["Dukelow, James S Jr" <jim.dukelow@pnl.gov>]

Frazier Bronson, Susan Gawarecki, and P Barring wrote:
-----Original Message-----
Subject: Re: Tokaimura doses

Susan Gawarecki wrote:
"Did they test "control" coins also?  Is there any Zn-65 content in the
average non-irradiated 5-yen coin?"

Frazier Bronson wrote:
My reply:

After the IRPA meeting in Hiroshima, I attended a VERY interesting workshop
on the JCO criticality accident. The workshop was organized by the Japan
Health Physics Society. One of the speakers [Komura, from Kanazawa Univ.,
plus 4 others] talked about Au-198 activation in gold jewelery.  The
measured values correleated well with distance, and with a neutron
transport code calculation.  The induced activation from the JCO accident
equaled the natural environmental neutron production value at approximately
2000 meters from the site [in the direction presented]. Of course, they
needed a quite sophisticated measurement system to detect these low
activities, especially from 1000m out.  They also measured activated Hg
from a thermometer at 600m from the source.  Other speakers talked about
Na-24 activation in soil and people, which were quite easily measured
hundreds of meters from the source.

However, given the good instrumentation available today, being "easily
measured" doesn't necessarily correlate to a "non-trivial"
dose/contamination, at least in our technical eyes.  However, in the
general public and new media, I suspect that it does.

frazier

and P Barring wrote:
------------------------------
Date: Wed, 30 Aug 2000 10:30:14 -0500
From: PBarring@kdhe.state.ks.us
To: radsafe@romulus.ehs.uiuc.edu
Subject: Re: Tokaimura doses -- a retry of an earlier posting

I never said that public response would be rational.  If the same thing had
happened in the US I think the Facility Manager would have been lynched and
ALL food produced within 50 miles would have been dumped on the company
president's lawn.  The Japanese have reacted quite calmly IMHO.

As for activated yen . . .   Was there any measurable dose coming off the
coins?  I am assuming the dose levels you refer to are neutron dose rates
when the mix flashed and not continuous dose rates now.  Also were the
coins compared to coins from outside the area?

 I don't want to argue over trivialities here.  The accident was stupid and
the repercussions will continue to plague us for some time.  This is a
fact, but lets keep some perspective. 

	<snip>

Jim Dukelow responds:

There is no indication that any "control" coins were tested, but the
distance/dose relationship of the tested coins looks pretty reasonable.

The inferred doses are those arising from the neutrons produced during the
criticality.  I don't know what the relative contribution would be from neutrons
diffusing from the location of the criticality vs volatile delayed-neutron
fission products being carried away from the plant by the wind.  All of the
coins out to a distance of 320 meters were taken from locations at headings
between SSE clockwise to WNW and all of the coins from headings ranging from SE
clockwise through N.  The Kohno and Koizumi letter does not indicate if those
constraints on the locations are related to wind direction or to the location of
occupied residences.  What the authors were measuring was the 1115.5 keV gamma
from Zn-65 decay.  A quick review of Radioactivity in the Environment by Ron
Kathren seems to confirm my intuition that there are no significant
non-anthropogenic sources of Zn-65.

I agree with the need to keep perspective.  What surprised me in the Kohno and
Koizumi letter was the size of the inferred prompt neutron dose at some distance
from the criticality.  Our instructions here at the Hanford Site for responding
to a criticality alarm are to run as fast as possible out of the building and
assemble in the staging area, which, typically, will be located at about 100
meters from the building.  The Tokaimura inferred 100 meter doses were 220 mSv.
Hmmm!

Best regards.

Jim Dukelow
Pacific Northwest National Laboratory
Richland, WA
jim.dukelow@pnl.gov

These comments are mine and have not been reviewed and/or approved by my
management or by the U.S. Department of Energy.
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