Well, I suppose that one helpful thing this discussion does for members
of the forum is to provide a "real feel" for some SI units that most
people know very little about. It's one thing to say that 1 Gy stands
for 1 J of absorbed energy by a kilogram of tissue but it's another
matter to know some typical values and their implications. And it
provides an opportunity to relate sieverts to grays.
CNN today provided an interesting web page
http://thechart.blogs.cnn.com/2011/03/15/what-you-should-know-about-radiation/
that linked to an FDA web page of interest:
http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115329.htm
The latter provides typical radiation dosages experienced in some common
medical procedures. Those levels are comparable to values we've been
discussing here.
Even though I no longer go to sea on submarines or operate nuclear
reactors, I reckon my Navy training on nuclear and radiological matters
is still useful.
Jim
On 2011-03-17 0958, [email protected] wrote:
Jim (Frysinger),
We recognize you as the most experienced authority on radiation reporting to
this forum. Please continue the good work.
Gene.
--- Original message ----
Date: Wed, 16 Mar 2011 22:54:01 -0500
From: "James R. Frysinger"<[email protected]>
Subject: [USMA:50063] Increased dosage limits
To: "U.S. Metric Association"<[email protected]>
I see in today's news that the "Fukushima 50" (50 workers at the site of
reactor 4 at the Fukushima plant) have been authorized to exceed their
normal annual dosage limit of 20 millisieverts (20 mSv). Their limits
were raised to 100 mSv and then later to 250 mSv.
Up to this "acute" dosage of 250 mSv, no significant radiological
effects are expected (for 50 % of such exposed workers), by most
radiological health personnel. Above that, workers might suffer
radiation burns (akin to sunburns) and noticeable changes in their blood
cell counts. As is the case in all fields, the dosage at which this is
expected to set in is debatable, with some touting a lower dosage and
some a higher dosage. And of course, people vary in their responses to
challenges to their health.
This higher dosage limit of 250 mSv is rarely authorized for
occupational workers but this is not the first time that a national
authority has done so. Susequently, these workers are likely to be
reassigned away from radioactive fields, at least for several years,
while their health is monitored closely. A few medical treatments (even
beyond potassium iodide and chelating agents) are available, but I'm not
knowledgeable enough to discuss those in depth.
LD50 dosage (at which 50 % of such exposed people are expected to die)
is usually considered to be 10 times this emergency dosage, that is, 2.5
Sv (2500 mSv).
By the way, I am talking about whole-body radiation here. Ingestion of
radioactive gas or particles is a different matter and there are too
many variables to discuss it here.
If there are any others here with experience working with nuclear power
reactors or with comparable experience in radiological controls, feel
free to jump in here! So far, I seem to be the only one who has run off
at the mouth on this stuff.
Jim
--
James R. Frysinger
632 Stony Point Mountain Road
Doyle, TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
(F) 931.657.3108
--
James R. Frysinger
632 Stony Point Mountain Road
Doyle, TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
(F) 931.657.3108
