SB: Re: bizarre assertions about radiation

[Derek Roff <derek@unm.edu>]

someone wrote:

> Remember too, when getting all excited about radiation:
> 1.  There is always a degree of natural radiation.
> 2.  Radioactive substances gradually lose there toxicity.
> 3.  Chemical toxins, unless there is a chemical breakdown
> process stay toxic forever.

Although I will agree that many people misjudge the risks involved 
with radiation, I find statements 2 and 3 above to be strange in 
their juxtaposition, and misleading in the context of their 
presentation.  #1 above is correct, there is always a degree of 
natural radiation.  I'm not sure how relevant that is to the 
discussion of home safety.  Radon can be termed "natural radiation," 
since it is not produced by man.  It is a significant health risk in 
some places, and not in others.  "Natural background radiation," the 
average radiation level measured at the earth's surface, is a health 
risk, but we can't get away from it easily.  Houses with radon 
problems can have radioactivity hundreds or thousands of times higher 
than the "background" levels.  And it's all natural.

Radioactive substances gradually lose their radioactivity, if not 
their toxicity.  The half-life of uranium 238, one of the more common 
radioactive substances in the earth's crust, is 4.47 billion years. 
That is roughly equal to the age of the earth.  The half-life of 
uranium 235, which is concentrated for weapons and nuclear reactors, 
is about 700 million years.   Uranium 238 decays into other 
radioactive elements, which emit alpha, beta and gamma radiation, and 
have half-lives ranging from 160 micro-seconds for polonium 214 to 
245,000 years for uranium 234.  The end of the process is lead 206, 
which is not radioactive, but is chemically toxic and carcinogenic. 
Many radioactive elements are chemically toxic as well.

All this leads me to believe that waiting around for "Radioactive 
substances [to] gradually lose there toxicity" is not a viable option 
for the owner-builders of most straw-bale houses.

> Even highly radioactive substances, such as spent fuel rods
> within a few years (5? 15?) cool off to the point that they are
> about as radioactive as the original ore.

I don't know a lot about mining, but this is absurd.  Uranium miners 
in New Mexico, at least as late as the 1980s, worked underground 
digging uranium ores wearing no more protective equipment than 
dosimeters, which measure radioactive exposure after the fact.  No 
special clothing was required.  On the other hand, spent fuel rods of 
reactors are classed as high-level radioactive waste.  They may not 
be optimum for nuclear power plants, but spent fuel rods are anything 
but well spent.  According to a Kennesaw State University report, 
quoting the Uranium Information Center,

"Spent fuel from nuclear reactors contains considerable amounts of 
U-235 and Pu-239. After 3 years in a reactor, 1,000 lbs. of 
3.3-percent-enriched uranium (967 lbs. U-238 and 33 lbs. U-235) 
contain 8 lbs. of U-235 and 8.9 lbs. of plutonium isotopes along with 
943 lbs. of U-238 and assorted fission products. Separating the U-235 
and Pu-239 from the other components of spent fuel significantly 
addresses two major concerns. It greatly reduces the long-lived 
radioactivity of the residue and it allows purified U-235 and Pu-239 
to be used as reactor fuel." 
<http://chemcases.com/nuclear/nc-13.htm>

A spent fuel rods contains almost all of its original uranium 238 
(U-238), a quarter of its original U-235, 8.9 pounds of plutonium 239 
(Pu-239), and roughly 15 pounds of other radioactive fission 
products, which are created during the operation of the reactor.  The 
half-life of Pu-239 is 24,000 years.  I conclude that 5 to 15 years 
are unlikely to have any significant effect on the major radioactive 
components of spent fuel rods.

Anyone planning to build an energy-efficient home, as most of us 
SBers are, will probably try to build a tight home.  Proper 
ventilation will be important for many reasons.  Poor ventilation, 
and the existence of a basement, will increase the likelihood of 
radiation problems.  If radiation is present at the site, it must be 
carefully addressed, or it will be a health risk for the life of the 
building.

Derelict Rough

Derek Roff
Language Learning Center, Ortega Hall Rm 129, University of New Mexico
Albuquerque, NM 87131  505/277-7368 fax 505/277-3885
Internet: derek@unm.edu

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