RE: Japanese dose readings - for real?

["Boyce, Dale" <DBoyce@intiso.com>]

You can't use the 1/r^2 at a mile to scale doses.  Air shielding is the
dominant factor in dose reduction at that distance scale. Two kilometers of
air is 260 g/cm^2.  For one mev gammas the attenuation due to absorption in
air would be a factor of 7E-8.  I don't have numbers at hand for absorption
of neutrons, but it should be significant.  The 400 R at one meter would
become 5.9E9 R/hr if we were talking gamma dose and correct for absorption.

Dale Boyce
dboyce@intiso.com

For those of you that have noticed my absence over the last few months,
I've moved to Texas.....

> -----Original Message-----
> From:	Brian Rees [SMTP:brees@lanl.gov]
> Sent:	Thursday, September 30, 1999 3:56 PM
> To:	Multiple recipients of list
> Subject:	Re: Japanese dose readings - for real?
> 
> Andy,  as usual, good points.  There is the potential to deliver 3.1 mSv
> IN
> AN HOUR, neutron,  from a criticality at 2 km, the rub being that it's in
> ms or even us (milli seconds or micro seconds).  Since it appears that the
> assembly is pulsing (not unexpected), dose rates will rapidly peak, and
> fall off as the solution heats, looses reactivity, shuts down, and fission
> product decay predominates.  When the solution cools, it can reassemble
> and
> burst again.  The 10x background at 2 km also sounds reasonable, that'd
> work out to ~ 400 R/hr at 1m using 1/r2 thumb rule.  
> 
> It's hard to tell what they're using to measure levels, and that could
> fuzz
> the real picture considerably,  time will tell...
> 
> (my own opinion)
> 
> Brian Rees
> Los Alamos National Laboratory 
> Los Alamos Critical Experiments Facility
> Operational Health Physics
> brees@lanl.gov
> 
> 
> At 02:23 PM 9/30/99 -0500, you wrote:
> >>As of late Thursday night, 3.1 millisievert
> >>of neutrons per hour, or about 15,000
> >>times the normal level of radiation, was
> >>detected two kilometers (1.2 miles) from
> >>the accident site,'' an Ibaraki Prefecture
> >>official told Reuters. 
> >
> >----------------
> >
> >Does anybody know who measured this dose, if they were using appropriate
> >instruments, if they were reading their instruments correctly, and if
> they
> >knew what they were doing?  If we don't know these things then, in my
> >opinion, this is just a rumor that may or may not reflect reality.  I
> would
> >think that dose readings this high should be verified by competent
> personnel
> >before they are accepted.
> >
> >Andy
> >
> >Andrew Karam, CHP              (716) 275-1473 (voice)
> >Radiation Safety Officer          (716) 275-3781 (office)
> >University of Rochester           (716) 256-0365 (fax)
> >601 Elmwood Ave. Box HPH   Rochester, NY  14642
> >
> >Andrew_Karam@URMC.Rochester.edu
> >http://Intranet.urmc.rochester.edu/RadiationSafety
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