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Doug J. Wrote
>Greetings,.....
>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.)..... >Just a "medical-type" trying to better understand a non-medical type event. Just a little refresher for those like me who actually had to look this
up...In other words, how often do we need to remember this stuff???
PER: Operational Health Physics Training
ANL-88-26 (MOE Manual)
Chapter 5 Section E Early Somatic Effects - Acute Radiation
Syndrome
.....For very high whole body doses, there are three basic
forms of early or acute damage. In the range above about 20 Gy (2000 rad),
the dose is fatal within a day or two. The same symptoms appear when the
head suffers sever irradiation, which point to a breakdown of the central
nervous system. This type of acute radiation syndrome is thus referred to
as central nervous system death (CNS death).
For the range 5 - 20 Gy (500 -2000
Rad), symptoms may appear within hours. Death occurs within a week or
so. In this mode, the damage to the lining of the intestinal tract is the
most severe. This from is called gastrointestinal tract death (GI
death). At the lower end of this dose range, it is possible for one to
survive this mode of death only to fall victim to the effects which prevail at
lower doses.
At doses < 5 GY (500 rad), the
most important effect is damage to the blood forming organs. Since these
centers are located in the bone marrow, this mode of death is often called
bone-marrow death. The first signs may appear within a few days,
depending upon the dose, and the total effect may not develop for a few
weeks. Sever changes occur when the dose is >2 Gy (200 rad). In
the range above 3 Gy (300 rad), the damage is severe enough so that death
becomes more and more probable.
......Death occurs in a larger fraction of cases as the dose
increases. If the dose becomes large enough, all cases of exposure result
in death. In the range where survival is possible, the concept of the
median lethal dose (LD50) is used. For man, the best estimate
places the LD50 in the range of 3 to 5 Gy (300-500 rad). Of course, in
this range all would have severe symptoms. NOTE that this dose REFERS TO
SHORT-TERM TOTAL BODY RADIATION (emphasis is mine).
Lethal Dose 50/30 (50% casualties
within 30 day - no medical treatment) is typically given as 450 Rem (450 rad or
4.5 Sv OR 4.5 Gy) acute dose. And the LD 50/60 is estimated to lie in the
range 2.5 to 5 Gy As Ray wrote in answer to Chris "Yes, it would be
more correct to use Gray". The concept of dose equivalence does not apply
to acute exposures greater than about 15 Rem. Of course, I'm sure the
community as a whole has learned much more about effects and the ways of
treatment thanks to Chernobyl since the above sections were
written.
How about it Argonne, can we expect a more up to date 'MOE' any time
soon?
Richard Urban Jr.
Justalowlifecontractradiationprotectiontechnicianscum
Aiken, SC
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