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Re: Criticality Accident Conditions

One place to start looking regarding characterizing the radiations from 
criticality events is ANSI N16.2-1969, "Criticality Accident Alarm System."  
It is important to keep in mind that the purpose of a criticality alarm system 
is to warn others.  The criticality event generally happens too quickly for an 
alarm system to help those directly involved.  The purpose is to get others 
out of the area and initiate an emergency response. If the event involves a 
moderated criticality, there is the possibility of the system cycling between 
critical and noncritical configurations.  For example, if the event is due to 
suspended material settling out in the bottom of an unsafe geometry container, 
the initial criticality will tend to be self limiting, since the energy 
release will resuspend the material.  It will tend to settle back, however, 
causing a recriticality.  Thus, the alarm system also is a warning that 
another event may happen. 
 
The protection of those working with fissile materials has to rely on rigid, 
conservative limits on quantities, concentrations, enrichments, and 
geometries; plus, on some occasions, the use of poisons.  It seems clear that 
in the recent event, some of these limits were violated. 
 
The opinions expressed are strictly mine. 
Bill Lipton 
liptonw@detroitedison.com





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Can anyone point me in the direction of literature which accurately 
describes the types and energies of radiation produced in a Criticality 
event, along with dose rate profiles, time durations etc.?  We have been 
asked to comment on whether a personal alarming dosimeter could provide 
useful warnings for personnel involved in recovery operations after an 
initial event, especially where there is a possibility of a second or 
repeated criticality condition.

No information has been forthcoming yet about what, if any, warning systems 
were in use at the Russian facility.

However, if the figures between 5 and 50 Gy are correct, it sounds unlikely 
that any kind of monitor would have been able to get the unfortunate Dr 
Zakharov out of his lab in time to avoid a significant dose, due to his 
proximity to the offending materials.

Is it policy for the Russian authorities to share their knowledge of the 
truth to assist others in avoiding a repeat?

Robert J Fletcher
Siemens Environmental Systems Ltd.
Robert.Fletcher@poole.siemens.co.uk
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