July less than the mass of the four
1945, fusion was artificially created for the first time after scientists collected
the first understanding into the physics of the sun. This is when the sun and
other stars seem to produce limitless energy as they constantly transform
hydrogen into helium by the process of fusion. Fusion is a thermonuclear
process which means that the atoms have to be astonishingly hot in order to be
stripped of their electrons so they can bounce around freely in a plasma. Stars
are able to create these incredibly high temperatures due to the fact that they
are so massive so that the pressures in their cores generates the heat to
squeeze the nuclei together.
that we could potentially create clean, limitless energy was sparked. More than
ten times the energy is made by fusion than fission for each gram of fuel used
meaning that it would almost completely replace nuclear fission power stations
as well as other forms of energy if an efficient reactor was built. However,
for the past 70 years we have tried to recreate the fusion power of stars by
magnetic confinement and by inertial confinement but it currently takes more
energy to initiate the fusion reaction than the output energy. Although humans
have been successful in producing uncontrolled nuclear fusion reactions which
is mainly used to make the hydrogen bomb, all the tremendous energy from this
uncontrolled reaction is released at once in an immensely destructive manner. However,
we have not been able to produce a controlled nuclear fusion reaction where the
same amount of energy is released but over a gradual period of time.
so bright due to their massive release of energy from nuclear fusion as they
convert hydrogen into helium. It releases a lot of energy due to the large
difference between the mass of the hydrogen nucleus and the helium nucleus
which is made. The mass of the 4He atom is about 0.8% less than the
mass of the four 1H atoms. This lower mass of the fusion products is
turned into a considerable amount of energy due to the equation E=mc2.
several requirements needed for nuclear fusion or nucleosynthesis to occur in
stars. Firstly, a substantial energy barrier of electrostatic forces must be
overcome since the nuclei, having had their electrons stripped, will both have
a positive charge and will repel one another otherwise. To overcome this, the
nuclei can tunnel through coulomb forces by the quantum effect. The coulomb
barrier is the smallest for hydrogen’s isotopes compared to 1H which
is why a deuterium-tritium fuel is used in nuclear fusion reactors. The
resulting energy barrier from using D-T is about 0.1 MeV.
One type of
fusion is Magnetic Confinement Fusion (MCF). This uses magnetic and electric
fields to heat and squeeze the hydrogen plasma imitating our sun. Hundreds of
cubic metres of D-T (deuterium-tritium) at a density of less than a milligram per
cubic metre are confined by a magnetic field at a few atmospheres pressure and
heated to fusion temperature. The power needed to start the reaction will be
about 70 megawatts, with a power yield of about 500 megawatts. The heat
produced by this reaction will heat water to make steam which will then go on
to drive electrical turbines to produce electricity.
type of fusion is Inertial Confinement Fusion (ICF). This uses pulses from super
powered lasers that are focussed very precisely on the surface of a pellet of
fuel (D-T) which causes an implosion. During the final part of the implosion,
the fuel core reaches 100 times the density of lead and ignites at 100,000,000°C.
Although fusion can be achieved, the technology of both MCF and ICF has a
long way to go until there is a net power output. Although deuterium can be
found easily in seawater and is therefore in abundance, tritium is much harder
to get with there being an estimated 20kg on Earth and most of it being tucked
away in nuclear warheads making it very expensive. However, helium-3 may make a
good substitute. Although it is very rare on Earth, the Moon may have large
quantities of 3He due to being bombarded by it for billions of years
due to the Moon’s lack of magnetic field. Therefore, many countries and
companies have shown interest in mining helium-3 from the Moon’s surface.
be many advantages to using nuclear fusion as an energy source with the main
one being that it would be a clean energy, producing no greenhouse gases unlike
the burning of fossil fuels and there would be no nuclear waste. Since there is
no chain reaction, there is no risk of what happened at nuclear fission
stations (Chernobyl or Fukushima) where radioactive material was released into
the surrounding area after a meltdown. The fuel would likely be very cheap
since about 1 part in 5000 of the hydrogen in seawater is deuterium which is
the main source of nuclear fusion.
As well as
there being many advantages, fusion does not come without its disadvantages.
Its main con is at an economical point of view as billions of either dollars or
pounds would have to be invested into research funding with a possibility that
it simply isn’t possible to achieve a net energy output on Earth. This money
could be spent on different sources of energy such as renewable energy which
has been proven. Power plants would also be incredibly expensive to build as
they require extremely high temperatures which is hard to contain.