This modern world would be lost without electricity. It's generated
in various ways, and one way is via nuclear fission. Some people think
it's the best and cleanest way to produce electricity ("at least you know
where the pollution gets stored"). Others think it's pretty
much the work of the devil and will bring on the end of the world. Many
think of it in terms somewhere between these extremes, or just don't think
about it much at all. But in any case, it exists and it's a mechanical
system, and therefore, millwright work is involved.
Quick Millwrighting Lesson of the
Month:
They're awfully picky about measurements and tolerances at nuclear plants.
When millwrights have to measure things very accurately, they use special
tools. One of these is the Vernier Caliper.
This
caliper is made up of two parts which slide across each other as you open
or close it around the item to be measured. One of the jaws is part
of a graduated 'beam scale', and the other is attached to the sliding bar
with the 'vernier scale' on it. These calipers enable readings of as
small as 0.001". There are other millwright tools more accurate than
verniers, but the vernier is useful for its versatility: one tool can
take inside measurements, outside measurements, depth and height measurements,
and can cover sizes from zero up to let's say 15 inches, depending on
the beam length. If you wanted to do all that with micrometers, you'd
need a couple dozen different tools.
To use the verniers, you position the jaws around the work surface to be
measured. This positions the vernier scale in a specific location relative
to the beam scale, and when you know how to read this, you get the measurement
of your work item.
On the beam scale, each inch is divided into 40 equal divisions. That
means each division is equal to 0.025". On the vernier scale, there
are 25 equal divisions each being 0.001". When measuring something,
only one line of the vernier scale will line up exactly with a line on the
beam scale, and that is the line you must find to get your measurement.
What you do first is read the beam scale, at the point where the 'zero' on
the vernier scale passes it. This gives you the number of full inches and
the nearest 0.025" below what the actual reading will be when you're done.
Then you look at the vernier scale to find which line is the one that
lines up with the beam scale. Add this value to the reading you just
took off the beam scale. The total is the actual measurement.
For example, if the vernier scale zero crosses the beam scale at just past
8.325 inches, and the line on the vernier scale which lines up perfectly
is '21', this means the measurement is 8.346 inches. This is because
the '21' means 21 thou, or 0.021", which when added to 8.325 gives 8.346.
Quiz Question:
Of course, this is a lot easier to understand when you have an actual
vernier caliper in your hand to read, than it is to follow in theory. So,
here's a picture of one giving you a reading. (Just read the bottom
numbers on this instrument's beam scale--this particular model is designed
so you can use the top numbers to get readings in fractional inches, which
is not nearly as useful for accurate measuring as thousandths of the inch.)
So, what measurement does it show, to the thous?
Feature Industry - Nuclear Power
Generation
Basically, a nuclear reactor is just a fancy way to make steam. It's
the steam which runs the turbines, and that's how the electricity is generated.
When power is generated from fossil fuel burning, it's still a result
of heat producing steam producing electricity. So the only really nuclear
aspect is how they get the heat to make steam.
Uranium is used as fuel, which when induced to begin a chain reaction, gives
off energy (heat). This heat is transferred to water, and on to steam.
So, what is this chain reaction, anyway? Well, the particles in the
nucleus of all atoms are held together by a binding energy. Large atoms,
like uranium, have more energy. When you split the particles apart,
this energy is released. Some of these particles are neutrons. It
so happens that bombarding the nucleus with neutrons will cause it to split,
which then frees its own neutrons, and they fly on to bombard more nuclei.
And so on. Chain reaction! The trick is to get the right
amount of neutrons in the right proximity to the fuel to get that reaction
running, while keeping it controlled. Different reactor styles used around
the world have differing designs on how to achieve this, but all designs
employ variations on surrounding the fuel core with a moderator (eg
heavy water), use of control rods between the fuel bundles, coolant, etc.
In the end, however, you still have a fuel heating water and steam generating
electricity.
Here are a few links to sites related to nuclear power:
This is a great article about the history of nuclear power, the construction
of the first successful chain reaction pile, and it even mentions the famous
historical millwright who ran the graphite-machining shop!
http://hep.uchicago.edu/cp1.html
The Atomic Energy Control Board is a government agency in Canada which has
the job of regulating nuclear reactors. Here's what they say about
themselves:
http://www.aecb-ccea.gc.ca/menu_e.htm
Well, (although yes, the picture could always have been clearer), you should
still be able to see that the zero is before the one-inch mark,
past the 0.8 mark, and just past the second division between
8 and 9. This indicates that the beam scale reading is 0.850.
Then, going to the vernier scale, it appears that the line which most
closely meets another line above it is the second line past the 5 -- ie,
7. So add 7 thou to 0.850, and you get the measurement:
0.857".
See you on the next monthly update of the Construction Millwright Feature
Page!
Check the archive to see past months' feature industry and quiz:
This
caliper is made up of two parts which slide across each other as you open
or close it around the item to be measured. One of the jaws is part
of a graduated 'beam scale', and the other is attached to the sliding bar
with the 'vernier scale' on it. These calipers enable readings of as
small as 0.001". There are other millwright tools more accurate than
verniers, but the vernier is useful for its versatility: one tool can
take inside measurements, outside measurements, depth and height measurements,
and can cover sizes from zero up to let's say 15 inches, depending on
the beam length. If you wanted to do all that with micrometers, you'd
need a couple dozen different tools.
