Environmental Pros and Cons of Nuclear Power:
In-class presentation,
Presentation overview:
Intro:
·
What do you think of when you hear “nuclear power”?
o
People in the class answered “evil” and “dangerous,”
to take two example
o
Out of over 3,000 respondents to this question in a
survey, only 2.5% responded with positive images
o
This perception is completely unrealistic; I’ll try
to prove that to you.
·
Outside of
·
It’s safer than you think and provides the type of
power necessary to run this planet
·
Far less pollutive than fossil fuels
·
Make your own decisions based on these facts:
Topic 1:
Nuclear Material
·
Uranium, discovered to provide energy in 1939 is one
of the most abundant elements in Earth’s crust
·
Uranium is currently mined through both strip and
drill mining processes then enriched via leaching (provides potency necessary
for fission)
o
Uranium mining harmful to the environment b/c actual
removal of Earth
o
Sulfur and other toxic chemicals used in refining
process
o
Only small quantities of useable Uranium are
gained-wasteful process
·
Two main isotopes: U-238 and U-235
o
238 is relatively stable in the short term
o
235 (occurring at .7% naturally) has less “nuclear
glue” (neutrons) and decays in such a way as to cause spontaneous splitting, or
fission, of the atom and the shooting off of one additional neutron
o
235 is useful in nuclear
reactors and must constitute about 3% of a total mass of Uranium for perpetual
fission to occur. It is enriched through
processes mentioned above.
·
Uranium is radioactive
o
Nucleus decays
o
Emits alpha and beta particles (harmful, but easily
stopped)—dangerous mainly in gas form if inhaled
o
Emits gamma particles, or nucleotides, which can seep
into water and air and cause radiation poisoning
Topic 2: Nuclear Reactors
Link:
http://www.ida.liu.se/~her/npp/demo.html
A simulation of a nuclear reactor; also useful for this explanation.
·
Nuclear reactors use radioactive material to produce
electricity
·
This process involves the following basic steps:
create fission, which produces heat, which heats water, which rises via
convection (and may or may not turn to steam), and turns large turbines
creating electromagnetic energy on the order of megawatts.
o
Fission, as we have seen, is almost exclusively the
product of U 235 and puts off tremendous amounts of heat energy
o
Devices in the core of the reactor shoot neutrons at
a 3kg ball (critical mass) of Uranium, causing a fission reaction which shoots
off more neutrons, causing a chain reaction in one of three states
§
Sub-critical: fission shuts down
§
Critical: fission stable and perpetual
§
Super-critical: fission unstable and unable to
infinitely perpetuate
o
Aluminum rods control the flow of neutrons to limit
reaction and prevent super-critical state, which can lead to a “meltdown” but
NOT an explosion
o
[here we segued into a brief discussion of a nuclear
weapon vs. a nuclear reactor]
§
a reactor has creative potential, a weapon
destructive
§
weapons us primarily plutonium, a useless substance
for reactors
§
weapons use explosives to combine two large hunks of just
sub-critical radioactive mass so that they suddenly become super critical
§
the result is a large explosion which also spreads tremendous
radiation
§
such an explosion cannot happen with a reactor
o
The fission reaction produces heat which warms water
flowing through the reactor core
o
Water in a reactor may either be pressurized so that
it remains liquid at very high temperature, or it may be allowed to boil and
create steam
o
Either way, the water rises and turns enormous turbines
that electricity
o
Huge towers are simply cooling towers where hot water
can exchange heat with surrounding air—they are not the reactor itself
·
The only waste products from this process are steam
and radioactive nuclear waste
Topic 3: Radioactive Waste
·
Radioactive
uranium 238 and 235 from reactors has half-lives of 4.5b years and 740m years,
respectively.
o
Elements
are considered safe after 10 half lives
o
This
means that it will take 45 billion years before this material is safely inert
o
This
is much longer than the present life of the universe
·
How
is it possible to store something for such a long time?
o
Waste
is now packed in barrels and stored dry or placed in pools of water to absorb
the radiation, but these are only temporary solutions
§
[we
discussed the advantages and disadvantage of such storage and realized that
even now, such means of disposing of waste are dangerous]
o
Current
government limitations only require waste be stored safely for 10,000 years
o
Suggestions:
underground in dry area (to prevent seeping into ground water) with minerals to
block and man-engineered barriers
o
But:
10,000 years ago, writing didn’t even exist, so will signs be enough to prevent
future digging at site?
·
We
have a basic solution, but how do we find a location to store the waste?
o
NIMBY
principle has been the guiding factor in decision making
o
[discussion
of NIMBY—in the long run it leaves no where to put the stuff! Work together to find some solution]
·
Currently,
we have chosen
o
Meets
all characteristics for a good site
o
Increasing
tectonic activity in the area may create future problems
o
Discussion:
Questions
asked
·
Storage
debate: is there a safer way to store waste than at
·
Rationality
of fear: a pound of uranium can take the place of a million gallons of
gasoline, more than a car can use in a lifetime. Will uranium ever be used in non-naval
vehicles? Should it be?
·
·
Would
nuclear power have existed without nuclear weapons? Does the potential to make weapons from
nuclear material justify not using it for anything?
·
Is
nuclear power worth it?
From here to the end of our allotted time, we discussed
primarily the efficacy of nuclear power, especially considering its dangerous
waste products and the costs of mining uranium.
We compared it to fossil fuels and came to a number of conclusions. The most common was that nuclear power, which
provides, for example, 80% of
