5) NUCLEAR ENERGY
I) FISSION REACTIONS
As large Uranium nuclei split into smaller nuclei, small amounts of matter
are converted into energy; the energy converts water to steam which then
generates electricity.
--Uranium:
The most common form of uranium, U-238, is nonfissionable. Through several
steps, the concentration of the fissionable isotope U-235 is increased
from 0.7% (in uranium ore) to 3% in fuel pellets. As uranium nuclei fission,
they release neutrons that then can cause other nuclei to fission in a
chain reaction. Control rods can be lowered into a reactor to absorb neutrons
and thus slow the reaction. Water surrounds the reactor core and acts as a coolant: it also serves
as a moderator which slows the neutrons down to make them more effective.
Some types of reactors (BWR or boiling water reactors) use the same water
from the reactor (radioactive) to generate electricity; others (PWR--pressurized
water reactor; HWR--heavy water reactor) have 2 separate water circuits.
BWRs and PWRs use normal water (and are therefore LWRs--light water reactors);
HWRs use "heavy" water which contains deuterium. Other types
of reactors use carbon dioxide or helium as coolants (GCR-gas-cooled reactor;
HTGCR-high temperature GCR).
Problems:
1) accidents may release hazardous radiation into the environment
a) 1957 the center of plutonium production in the U.S.S.R. in the Ural
Mts. suffered the worst accident in history; although the details and
effects are still secret, several hundred square miles were effected,
30 towns and villages in the area are now deserted and no longer appear
on maps
b) 1957 an explosion in Liverpool released radioactivity that may have
caused premature cancer in 33 individuals
c) 1979 TMI (Three Mile Island): due to lack of coolant, 62 tons of reactor
core (about half) melted. $1 billion was spent in the cleanup. Although
the health effects are still being debated, most feel the effects were
minor through luck alone, this accident could have been much worse.
d) 1986 Chernobyl: 2 explosions blew off a 1,000 ton roof. The immediate
effects were that 36 people died and 237 hospitalized with acute radiation
sickness (many may eventually develop cancer). Experts estimate that 5-10,000
may die prematurely from cancer and thousands more will have other problems
such as cataracts and sterility; 135,000 were evacuated, many of which
can never return home. Much of the information is still secret and the
cleanup cost about $14.4 billion. Interestingly, the above numbers represent
the original estimates. Secret documents released in 1995 after the breakup
of the USSR reveal that 125,000 died and another 576,000 are potential
victims; the total cost may reach $300 billion. The results would have
been worse if the accident had occurred during the day or if the wind
had been blowing toward the city of Kiev.
e) Potential accidents: The year after the Chernobyl accident, the U.S.
closed a similar military plant in Washington state in which 54 serious
safety violations had occurred from 1985-86; the Peach Bottom plant in
Pa. was shut down in 1987 when operators of the control room were found
sleeping while the reactor was at full power. Not only have workers broken
safety codes from ignorance or disobedience, Congressional hearings in
1987 showed that high level NRC (nuclear regulatory commission) members
have destroyed documents, obstructed criminal investigations, given advance
warnings of surprise inspections, suggested ways of evading safety regulations,
and intimidated lower level staff that give too many safety violations
(American Chemical Society, 1994).
2) Storage
Storage sites of wastes must be permanent since Cesium-137 and Strontium-90
will be radioactive for hundreds of years, Plutonium-239 for thousands.
In the U.S., 280 million liters of highly-radioacative liquid, 21,000
metric tons of highly radioactive solid, and 2 million cubic meters of
low radioactive solid waste awaits disposal; the first U.S. storage site
deep underground (600 meters) may be completed by 2010 (at which point
73 nuclear power plants will no longer have space to store their wastes).
If there is only one site (Yucca Mt., Nevada), nuclear wastes from all
over the country must be shipped there be truck and train. Currently there
is 30,000 tons of nuclear waste at 75 sites that must, by law, be moved
by 1998
In 1986 a number of secret documents were uncovered showing that from
1957-85 at least 30 incidents were kept secret while officials assured
the public there was no danger of contamination; most weapons facilities
have been operated with gross disregard for the surrounding public. Before
1970, the U.S. dumped 90,000 barrels of waste in the oceans. Before 1983,
European countries dumped 90,000 metric tons of radioactive waste; the
barrels began leaking years ago. The USSR disposed of 20 nuclear reactors
(7 loaded with fuel) and millions of liters of radioactive waste into
the ocean (double the amount of all other nuclear powers combined).
3) Costs
The costs of generating nuclear energy have soared, in part due to increased
safety regulations. As a result, there is less impetus to develop nuclear
energy since more economical energy sources are available. In 1970 nuclear
power produced electricity at about half the price of a coal plant; in
1990 the price was double. In U.S., no new nuclear power plants have been
ordered since 1975 and 108 previous orders have been canceled. The magazine
Forbes called nuclear power plants "the largest managerial disaster
in U.S. business history" costing about 1 trillion dollars.
Nuclear power plants must be shut down (decommisssioned) after a certain
number of years. This includes removing all radioactive materials (high
risk), mothballing under constant guard for several decades, and entombing
the reactor in concrete. The costs of decommissioning may be $1-3 billion
for the immediate removal and $225 million for dismantling (about 2-10
times original contruction costs). Some reactors have already been shut
down and await decommissioning; many fear that costs will simply be passed
down to the nest generation if appropriate actions are not taken.
The U.S. has the greatest number of nuclear plants worldwide (at 104)
but they only generate 20% of our electricity as opposed to 76% in France,
73% in Lithuania, 57% in Belgium, 53% in Slovak Republic, and 47% in Ukraine.
In the United States, more than 90% of all nuclear power plants are east
of the Mississippi, requiring long travel to disposal sites such as Yucca
Mountain (Kemp, 2004). The U.S. currently has 104 plants, of which 55
will be retired by the year 2010. If no new plants are built, there will
only be 41 reactors operating in 2010. Four U.S. plants (20 worldwide)
are retired and await decommissioning; this may reach 70 (225 worldwide)
by 2010. The 100 plants in operation in the U.S. make require $200 billion-1
trillion to decommission. Most agree that another plant will probably
never be built in U.S. Once regulations concerning nuclear energy are
lifted and they must compete in a free market, as many as 1/3 may close.
Throughout the world, there is a renewed interest in nuclear energy. In a number of countries where the future of nuclear energy was bleak, preliminary studies are underway to expand it. In the
--after Kemp, 2004
--after Kemp, 2004
Breeder Reactors: use U-238 as a fuel since it is much more common and
since U-235 resources may only last another century. It creates fissionable
Plutonium-239 as a byproduct. The dangers include the use of sodium which
can lead to fires (as in France) and the production of Plutonium which
is hazardous and might be stolen for use in weapons.
II) Fusion Reactors: Unlike nuclear fission, which involves the splitting of a large atomic nucleus into two smaller nuclei, nuclear fusion involves the joining of two small atomic nuclei to form a larger one. In a hypothetical fusion reactor, deuterium and tritium nuclei would fuse to form large amounts of energy (the deuterium that could be collected from 1 cubic mile of seawater could generate more energy than all the world's fossil fuel resources).
Although fusion reactors would potentially solve all of the world's energy problems, the temperature of the reaction may prevent the technology from ever being developed. The temperatures needed to initiate a reaction would be similar to those found at the sun's core (100,000,000 degrees C). High temperatures and large amounts of energy would be difficult to contain since all known materials would vaporize. Strong magnetic fields may be the only hope.
OTHER
Electrical vehicles can reduce carbon emissions by half but vehicles must increase their power and potential distance before they become widely marketable (IPCC, Document III, 2007). The sale of hybrid cars in the U.S. rose from almost 8 thousand in 2001 to 207 thousand in 2005 (IPCC, Document III, 2007).
Some have proposed that solar panels could be attached to satellites in space which would use a beam of microwaves to transmit energy to earth (Oida, 2007).