Re: Exposures in Japan Accident

[dsimpson@unlnotes01.unl.edu]

I have not seen any information yet on the ratio of neutron dose to gamma dose
in the Japan accident.
However I looked up some information about a similar accident that occurred in
Oak Ridge TN in 1958 that might give us some ideas.  In both accidents, a
solution of Uranium went critical in a tank (actually a 55 gallon drum in Oak
Ridge), while people were in the area.  An extensive report was prepared about
the Oak Ridge accident that included dose reconstructions.  These
reconstructions indicated that the absorbed dose (rad) consisted of
approximately 75% gamma and 25% neutron for those relatively close to the event.
Like the Japan event, the criticality in Oak Ridge did not immediately shut
down, but apparently pulsed for about 15 minutes.  The neutron dose was
primarily high energy (80% in the Mev range).  Obviously, the Japanese values
could be significantly different, based on the types of materials in the area,
shielding, etc. but this might give a first order approximation of how the dose
was distributed between the two components

++++++++++++++++++++++++++++++++
David R. Simpson, Ph.D. CHP
Radiation Safety Officer
University of Nebraska - Lincoln
DSIMPSON1@UNL.EDU
++++++++++++++++++++++++++++++++


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