- The D-T (deuterium-tritium) fuel cycle
is the most promising one at the moment for
controlled fusion
for fusion power.
Note the
D-T (deuterium-tritium) fuel cycle
is a one-step nuclear burning
process.
The multi-step nuclear burning
processes that happen in
stars
(i.e., the
proton-proton chain reaction
and the CNO cycle) are much
too complicated to implement
in fusion reactors.
Note also the first step of the
proton-proton chain reaction
(the nuclear burning of
2
hydrogens (H)
to 1
deuteron (D,H-2))
is much too slow to implement just by itself
in fusion reactors.
- The heart of the
D-T (deuterium-tritium) fuel cycle
fuses exothermically
deuterium (D, H-2)
(the hydrogen
isotope
whose nucleus
has one proton and one
neutron:
i.e., heavy hydrogen)
and
tritium (T, H-3)
(the hydrogen
isotope
whose nucleus
has one proton and two
neutrons:
i.e., heavier hydrogen)
to helium-4 (He-4) and create
electrical power
(HRW-1109).
- The reaction is NOT part of
PP chain reaction
that powers some stars
(e.g., the Sun).
There is NO abundant tritium
in nature (see below).
As noted above, the
PP chain reaction
is much too complex and too slow for feasible
fusion reactors
(see HRW-1109;
nuclear_burning_pp.html).
- Actually, there is nothing magical about how
controlled fusion creates the
electrical power:
the controlled fusion
generates heat energy
which powers a heat engine
which powers an
electric generator
which creates electrical power.
Except for the heat energy
source, everything is the same in principle as for
conventional nuclear-fission
nuclear power
or
fossil-fuel power.
- A bit of terminology:
Formally, deuterons are the
nuclei of
the deuterium
atom;
tritons are the
nuclei
of the tritium
atom.
In practice, one often uses the terminology loosely: e.g.,
deuterium for
deuterons
and vice versa.
- Fusion power is great.
- The fuel is practically limitless.
1 in every 6700 hydrogens
on Earth
is a deuterium
(HRW-1109) and we have a lot
water (H2O).
Collecting the deuterium is
expensive, but NOT that expensive.
Tritium is a
radioactive isotope
with half-life of 12.32
Julian years,
and so large amounts to NOT
exist in nature,
but it can be bred in
fission reactors
(see
Wikipedia: Tritium: Production).
By the by, a
half-life is a sort of
mean lifetime of a atomic nucleus
before
radioactive decay.
More exactly, half a sample of
a radioactive isotope will
decay on average after one
half-life.
- The difficulty with fusion power
is that it is difficult to make
plasmas
hot enough (∼> 10**7 K) and control them.
Recall, a plasma is an ionized gas.
If such a plasma
touches a wall made of a solid,
it vaporizes the wall and cools.
The main solution to the control problem has always been
to contain the plasma
with magnetic fields rather than
solid containers.
But magnetic containment and extraction of
heat energy there from has its
own difficulties.
- The advantages of fusion power:
- Limitless fuel as aforesaid---as long
as you have
fission reactors
to breed tritium.
Note the
breeder fission reactors
do NOT have to be optimized for
energy generation.
- Fusion power
is inherently safe because
fusion reactors have NO
chance of having becoming uncontrolled.
If anything goes wrong, they just stop reacting and turn off---in fact,
that's the problem so far: the
fusion reactors
are pretty much off.
This is unlike conventional
fission reactors which
are always on the verge of
nuclear meltdown.
- Fusion reactor
technology in itself is NOT
necessarily a
nuclear weapons proliferation
concern.
Fusion reactors
do NOT directly connect to
bomb manufacture.
Fission reactors are
always related to nuclear weapons
since their fuel
(uranium-235 (half-life 0.7038 Gyr)
or
plutonium-239 (half-life 24110 years))
can be used to make
fission bombs.
The
breeder fission reactors
for tritium can be kept
in safe countries which
just export
tritium for
fusion reactors
in other countries.
Note fusion bombs
must always be ignited by
fission bombs
and are NOT related technologically to
fusion reactors.
By the by, if anyone knows
how to ignite fusion bombs
from a chemical-reaction
explosion, they are keeping very quiet
about it.
- Fusion reactors
generate
radioactive waste
with only short half-lives???.
It can just be buried in the ground and forgotten about since in a few decades it
is harmless????.
Let's hear it for Yucca Mountain---the
Dracula of
deep geological repositories for nuclear waste---it
always rises from the dead.
This is unlike the radioactive waste
from fission reactors
which can have very long
half-lives, and so requires
quasi-eternal stewartship: i.e.,
high-level radioactive waste management
including of
mixed waste.
Of course, the
breeder fission reactors
for tritium will produce
long-lived radioactive waste,
and so everything is NOT happy.
- The disadvantages of fusion power:
- The
fusion power dream
has been with us since circa 1945
and seems good for another
80 plus
years
(see Fusion power: History of research).
Experimentally,
controlled fusion has been done, of course.
But whether commercial energy
generation is possible is still uncertain.
It may be technologically out of reach.
- The breeder fission reactors
for tritium
are a
nuclear proliferation risk
and a source of
radioactive waste
- The use of fusion power
may be obviated by the use of
renewable energy
(most importantly
solar power
and wind power).
Say 80 plus
years
fusion power arrives, but
we already have all the
commercial energy we need and want
from renewable energy.
In this case,
much of the research into
fusion power would have
been a waste of time and effort.
- One can conclude that
fusion power is wonderful---except
for the NOT working part.
Can it work? Maybe, but yours truly is losing faith.
And there's an old saying: "fusion power
is the energy of the
future---and it always will be."
- Circa the 2020s, the
big fusion power
international research project is
ITER (construction 2013--2025).
But experiments with the
D-T (deuterium-tritium) fuel cycle
are expected to
start way off in
2035
(see
"Fuel for world's largest fusion reactor ITER is set for test run", Elizabeth Gibney, 2021, Feb22, Nature).
So don't hold your
breath for abundant
fusion power.
- For further elucidation, on
nuclear physics, see
Nuclear physics videos
below
(local link /
general link: nuclear_physics_videos.html):
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