Environmental Engineering Reference
In-Depth Information
The reactors in operation today are dubbed second generation, while the
reactors that will be built over the next ten to fifteen years are generally
described as third generation, even though they are refinements of second
generation reactors. The vast majority of second - and third - generation
reactors are pressurized water reactors or boiling water reactors. These
have two main drawbacks:
An inefficiency
in the requirement for a secondary loop of water to
be heated (in order to produce turbine-turning steam) by the primary
loop of water that passes through the reactor core.
Production of a lot of waste
from fuel that passes only once through
the reactor and is then stored.
So work is underway to design a fourth-generation reactor that helps to
ease one or other of these problems.
One of these designs is a supercritical water-cooled reactor (SCWR),
which heats water under pressure - as we have seen in supercritical coal
plants - beyond its critical point, becoming a homogenous fluid that can
drive a turbine directly, without steam. Another is the high temperature
gas-cooled reactor (HTGR), which heats helium, and which can then be
used to drive a turbine directly. The other main family of possible fourth
generation reactors are called fast reactors(“fast” refers to the type of neu-
trons in the nuclear reaction). These fast reactors are variously termed
sodium-cooled, gas-cooled and lead-cooled, depending on the type of
coolant used. (It should be noted that coolant is a bit of a misnomer here,
being fantastically hot: the coolant conveys the heat from the nuclear
reaction.) The advantage of fast reactors is that they can burn up nuclear
waste or drastically reduce it in volume and toxicity. The disadvantage is
they can be used to “breed” weapons-grade plutonium.
Future fusion - fantasy or feasible?
There is an alternative to nuclear fission. It's called nuclear fusion, and it's
an attempt to replicate the power of the sun, no less. It is worthy of men-
tion because in pursuit of this goal the major governments of the world
have joined together to spend €10bn on the Iter project.
The rationale for attempting nuclear fusion rests on, to the layman, a
bizarre fact of physics. Namely, while the splitting of an atom in nuclear
fission can release the enormous energy that binds the atom's particles,
