Re: some details on the criticality in Japan

[g2v13a@swbell.net]

Greetings,

May I ask for some information that may help some of us understand the doses
better.  (I am mostly involved in total body irradiation for leukemia ...)
In medical TBI treatments a beam of 6-10 MV x-rays is used with doses of
250-300 cGy are commonly given (split between two exposures) per day to a
total of between 900 - 1200 cGy (depending upon institutional preferences).
Based upon my observations of these patients over the years, I am suprized to
be hearing that 6-8 Sv in one exposure of less than one hour can cause death
within 6 hours or severe cns (etc.) symptoms within 8 hours.  Admittedly, I
have dealt only in fractionated x-ray (medical) exposures.  My questions are
(for this type of event) :
1) What is the likely dose to the three persons described in the media
reports ?
(6-8 Sv does not seem to be consistant with the reported symptoms.)
2) What are the likely photon and neutron dose components ?
3) What is the likely "x-ray" equivalent photon spectra ?
4) What is the likely neutron energy distribution ?

Just a "medical-type" trying to better understand a non-medical type event.

Doug J.
------------------------------------------------------------
Thomas Gleich Harrison wrote:

> Undoubtedly a steam/vapor powered explosion within an enclosed container.
> If the Keff was estimated to be approx 1.044 it wouldn't take much of an
> expulsion of material from the tank to reduce the Keff to less than one
> and kill the fission process, which is probably what has happened. If the
> fission process is continuing then much of the radiation yield might have
> a detectable fast neutron component... which could be easily seen and
> would probably be in a pulse mode if measured directly in the absence of
> shielding. The residual radiation field is probably from fission product
> decay I would think. Also usually the proximity of workers to a mixing
> tank while in the process of a dump is not immediate ..... if the blast
> was sufficient to remove a portion of a roof then death would probably
> result from trauma injuries prior to radiation sickness if the workers
> were the same distance from the tank.
>  The tank cap may be what tore a hole in the roof...
>
> just my opinion(s).....
>
> Tom Harrison
> RSO/Physics
> University of North Texas
> tomh@jove.acs.unt.edu
>
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