New Nuclear Power Technologies
Introduction:
There are many new waste disposal technologies which could
prove to be somewhat of a solution to the problem of nuclear waste.
Reprocessing, The Missing Step:
Although not a new technology, reprocessing can be part of
the solution to nuclear waste. When nuclear power was first developed, it was assumed
that spent nuclear fuel would go through a process called reprocessing. In
reprocessing, one of the major transuranic wastes, 239Pu, is
extracted from the spent fuel rods. This 239Pu (plutonium-239)
is fissile and can be reused in power plants. The advantages of this process
are somewhat obvious: The volume of waste is lessened and more fuel is created
for nuclear reactors. However, as with all things, politics can get in the way.
In the US plutonium reprocessing was banned because the recovered
239Pu is weapons grade material. If, after reprocessing, the fuel
is stolen, it could be used by anyone to construct a nuclear weapon. As of a
few years ago, the ban against reprocessing in the US was lifted, but there are
still no operating reprocessing plants in the US because of the heavy
regulations and the anti-nuclear sentiment of the general public. There
are a
few countries which do reprocessing, however. France, for instance, regularly
reprocesses its spent fuel.
High Temperature Breeder Reactors:
Many of us are familiar from television (and hopefully not
from real life experience) of the bar-room game in which a very large man holds
a mug of beer on top of his head and challenges people to punch him. If his
opponent punches him hard enough, the beer falls off and spills all over the man
holding it. The harder the punch, the better chance that the beer will fall off
and the puncher will win. Also, the bigger the man is who is getting punched,
the harder the punch must be to knock the beer down. You might be wondering
why we are talking about a bar-room game. Think of the guy holding the beer as
an atom and the guy punching as a neutron. The transuranic elements are bigger
than uranium and generally don't fission (get their beer knocked off) in a
regular reactor. The neutrons aren't excited enough (don't punch hard enough)
to induce fission in them. However, if they are placed in a high-temperature
reactor in which the neutrons are much more excited (and carry more punch),
there is a much better chance that they will fission.
In a reactor being developed by Argonne National Laboratory in the US, almost
100% of the transuranic nuclear wastes produced through neutron capture can be
caused to fission. Generally, the fission products created have shorter
half-lives and are not as dangerous. This reactor, dubbed EBR-II, uses liquid
sodium as a
coolant, which means that the internal reactor temperature is much, much hotter
than that of a normal PWR reactor, which uses water as a coolant.
Another advantage of EBR-II is that its fuel is not weapons grade
quality.
When the transuranic wastes are separated from the other wastes in the spent
fuel rods, the resultant mix of isotopes can not be used in a bomb. Thus, the
mix can be used as fuel for EBR-II without a chance of it getting stolen
by a terrorist group for use in an explosive device.
Breeder reactors "breed" fuel. That is, they are designed to create
239Pu from 238U through neutron capture. This
"waste" can then be used as
fuel.
