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RE: lochbaum on radiation
"If we keep doing what we're doing, we'll keep getting what we're
getting."
Chris A. Marthaller
Sr. Training Coordinator - WIPP
marthac@wipp.carlsbad.nm.us
(505) 234-8661
Obviously, only my own views
-----Original Message-----
From: x [mailto:netngatr@magnolia.net]
Sent: Monday, May 08, 2000 9:49 PM
To: Multiple recipients of list
Subject: Re: lochbaum on radiation
>Dave's two cents. Now is radiation all the same, or are there
"differences"? Or our
>we looking at the same thing in two different ways?
Somewhat. Maybe my limited expertise can help explain below.
>> Regarding your question about radiation, there are differences in the
biological
>> effects from different kinds of background radiation,
That's correct. Different TYPES of radiation (alpha, beta, gamma,
neutron) deposit energy in different concentrations along their
interaction paths because of different interaction mechanisms.
Several things to keep in mind:
The energy of the original radiation is typically different for
different isotopes
Different TYPES of radiation will produce different ion pair
concentrations (depends on mass and charge)
It takes roughly 33.9 ev to produce an ion pair in water or soft tissue
Number of ion pairs produced are different for different ENERGY of
radiation (should be easy to see that a 500 ev electron will produce
fewer ion pairs than a 700 ev electron)
Given an alpha and electron of same energy, the more massive and more
highly charged particle radiation (alpha) will tend to have a shorter
and straighter travel path than the less massive and less charged
electron, but produces more ions per unit distance of travel (ion pair
concentration). But, a 500 ev alpha produces the same quantity of ion
pairs as a 500 ev electron, although in different concentrations per
cell traveled. The electron will have a lower concentration of ion
pairs per cell traveled, but will affect more cells.
Again, the number of ion pairs produced will depend on the TYPE and
ENERGY of the original radiation which varies among isotopes and hence
biological effects will be different (for different TYPES and different
ENERGY).
>> differences in the biological effects from different kinds of
man-made radiation,
That's correct. See above.
>> and therefore differences between biological effects of background
and man-made radiation.
Not correct. This is a very subtle but circular reference.
It is true that there are different biological effects WITHIN naturally
occurring radiation because there are different TYPES and different
ENERGY radiations.
It is also true that there are different biological effects WITHIN
man-made radiations because there are different TYPES and different
ENERGY radiations.
BUT, if we consider the SAME TYPES and SAME ENERGY of natural background
and man-made radiations, they are the same. It matters not the origin,
it is the end result (energy deposited, number of ion pairs, and
concentration of ion pairs) that produces the biological effect.
>> The differences are due to the energy levels involved and to the
pathways for damage.
Correct, but not complete. Energy is a prime consideration, as well as
total activity, pathway, chemical composition, tissue of deposition,
age, cell division rate, and a host of other variables.
BUT, given variables that are EQUAL for both natural and man-made, the
effects are EQUAL. It takes roughly 33.9 ev to generate an ion pair in
water or soft tissue (again, variable depending on the type of tissue).
Because the number of ion pairs and ion concentration produced depend on
the original TYPE and ENERGY of the radiation, it matters not whether
it is naturally occurring or man-made.
That's enough, it's past my bedtime.
Richard Sumrall, RRPT
rsumral@entergy.com
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