At 08:01 PM 5/21/01 -0500, Dan M. wrote:
> > Of course I'm serious. After all, you claim that the radiation risk from
>me
> > is greater than the radiation risk from nuclear power. If the radiation
> > risk from nuclear power is so much less, then why are the safety measures
> > so extremely more strict? Logic dictates that higher risk requires more
> > safety measures, not less.
> >
> >
>There are a few things to be said about this. First, logic often goes out
>the window when people think of nuclear this or nuclear that.
Why do you suppose name of the medical imaging technique was changed from
"NMR" = "nuclear magnetic resonance" to "MRI" = "magnetic resonance
imaging"? The word "nuclear" in the former name did not refer to
radioactivity being involved anywhere in the process, but to the fact that
the process works by causing the _atomic nuclei_ in the molecules in the
body of the person being scanned to vibrate in resonance with the magnetic
field generated by the big magnet surrounding the imaging chamber.
>Look at how
>people can ignore multiple fatalities in some industries and worry about the
>implications of many fewer deaths in another. There have been two
>industrial accidents. One had no deaths directly associated with it. The
>other had 30 (I got that number from anti-nuke websites, so I think it
>isn't low). With Chernobyl, the UN commissioned a very thorough medical
>follow-up, and they have yet to find any increase in the death rate for
>people who were effected by this accident.
Compare that with the annual death rate from accidents involving power
generation from fossil fuels, particularly coal mining.
>And, this accident had three terrible things going on that made it as bad as
>it was:
>
>1) The design was old, long retired from the West at least partially for
>safety reasons
>2) There was no containment building
>3) The workers were playing games with the reactor.
>
>And even with these three causes, none of which would happen in the West
>(the first 2 couldn't, the third is virtually inconceivable...someone
>allowed to play with a billion dollar piece of equipment like that),
Anyone know if the Russian proclivity for vodka was ever shown to be a factor?
> the
>deaths were limited to 30. 30 is indeed 30 too many, but it is not worse
>than 30 people dying on the roads on a weekend or its not as bad as 300
>people dying in a plane crash.
>
>But, these two accidents are listed as proof that nuclear power is
>overwhelmingly dangerous. I don't see the logic in that.
>
>Having said that, let's look at the other part of what you said. Since
>there are elaborate safety measures for nuclear power, it must be more
>dangerous. Well, lets consider flying across the US vs. driving across the
>US. Flying is definitely safer. There are more deaths by car than by
>plane. After millions of miles in each category, there is more than enough
>data to make that conclusion.
>
>Flying has many more elaborate safety measures than driving. Due to cost of
>scale, etc. it is possible to have those safety measures. If the same
>safety measures were used for flying as were used for driving, there would
>be a lot more plane crashes than car crashes. But, that doesn't mean that
>flying is riskier than driving.
>
>A second example. They electricity in your house represents a greater risk
>than the high voltage lines running high in the air. High voltage can kill
>you quicker than low voltage, but it is possible to take safety precautions
>with the high voltage lines that cannot be taken with low voltage lines.
>So, more people die from electrocution from low voltage than high voltage.
>
>Chemical poisoning is the same. Industries can use vast quantities of
>various poisonous substances. If this stuff were simply stored in open
>bottles around the house, it could have devastating consequences. But, with
>the value of the production of these plants, the companies can afford to
>take significant safety measures that the average homeowner cannot. Thus,
>stuff under the sink is the cause of most poisoning deaths.
Also, babies aren't generally allowed to crawl unsupervised through
industrial chemical plants.
>Now, back to nuclear power. The basic rule for nuclear safety is ALARA: As
>Low As Reasonably Achievable. This means that all reasonable effort needs
>to be taken to minimize radiation exposure, even if the exposure is well
>within legal limits. We worked at our company to have exposure limits that
>were a fraction of the legal limits.
>
>Lets look at this with nuclear power. There are megaCuries of radioactive
>material in a reactor. This is not something you want under the kitchen
>sink.
It might discourage the roaches and mice. OTOH, I'm not sure I want to see
any GITD two-headed mice running through the kitchen, either. <g>
>But, workers have to be able to work in a nuclear plant. So what is
>done to follow ALARA.
>
>There are three ways to minimize exposure. They are referred to as TDS:
>Time Distance Shielding.
>
>The exposure to a given source is proportional to the time spent near it.
>So, by reducing the time it takes to do a job in a radiation area from 10
>minutes to 5, one decreases the exposure by a factor of two.
>
>The exposure is also inversely proportional to the distance from the source.
Do you mean 1/r or 1/r^2?
>So, a 1 curie source 1 meter away is more dangerous to you than a 1
>megacurie source 1.5 km away from you.
We had a curie-level source of Cs-137 that we used in the lab. When not in
use it was kept in a "safe" that was actually an old ceramic kiln lined
with two layers of lead bricks*. I believe the weight of the safe was over
1000 pounds: it had wheels mounted on the bottom so it could be moved, but
it took an effort.
*Those are bricks that are the same size as ordinary house bricks -- 2" x
4" x 8" (5 x 10 x 20 cm) -- made of solid lead. When we talk about
"density" in class, I use one of them as a very effective object lesson: I
pass it and a _styrofoam_ brick (such as florists use when arranging
flowers) that I painted to look like the lead brick around the class and
have the students compare the effort needed to pick each up. It
effectively demonstrates that one cannot judge the mass of an object from
its visual appearance.
>The exposure can be minimized by shielding. A sheet of paper can stop an
>alpha particle, a piece of aluminum foil, most beta. Gammas and neutrons
>require more shielding. The gammas from your Sonja are 1.46 Mev, and you
>should really have about 5-6 inches of steel to be sure you've stopped them.
>(If you really want I can run a MCNP model on this. :-) )
>
>Well, at home, that's virtually impossible. ALARA is As Low As Reasonably
>Achievable. It would be unreasonable to expect you to keep your distance or
>only see her for 5 minutes a day, or to keep encased in steel. It would
>interfere with normal functionality. :-)
Lead-lined underpants, made of the same thing as those aprons they use at
the dentist's office, maybe? <vbg>
>With a nuclear plant, this is much easier to accomplish. Through the
>effective use of shielding, the radiation levels in the control room, etc.
>are low. Indeed, lower then in bed with a spouse according to what I've
>been told. I wouldn't doubt that, because once you are within a factor of
>10 or so, it should just take another layer of cinder blocks to get below a
>given level. (This is an off the cuff calculation, but I've had to design
>radiation areas where the outer walls had to be public areas before.) I'm
>sure they don't use cinder blocks, but you get the idea.
Actually, that's exactly what we used around the accelerator
enclosures: _solid_ concrete blocks (another thing that is remarkably
heavy, especially when you have to repeatedly lift them to the top of a
wall) made into a wall 3 feet thick.
And one of those "full-length" mirrors you normally find hanging on a
bathroom door hanging at an angle from the ceiling to give the operator at
the console a remarkably good view over the wall of the entire cyclotron
chamber. Also closed-circuit video cameras, shielded inside grounded
copper-mesh cages against the radio-frequency oscillating magnetic fields
used in the accelerator.
-- Ronn! :)
