Fusion in the Stars

Nunez & Panogalinog

Nuclear Fusion in stars is one of the most important reasons which make life on Earth possible!

○HOW IS THAT SO ?

65% of your body is made up of Oxygen and 18% is Carbon. These two elements are created through nuclear fusion in stars. So we all are indeed made up of star dust.

All life on Earth exists because the light generated by the Sun produces food and warms our planet.

Fusion is the process that powers the Sun.

Unlike nuclear fission, which releases energy when a heavy atom splits into two lighter elements, fusion releases energy when the nuclei of two light atoms combine to form a heavier nucleus, such as when two hydrogen nuclei fuse to form a helium atomic nucleus.

The fission of an unstable heavy nucleus occurs more easily than the fusion of hydrogen nuclei. This is because the strong electrical forces of repulsion between 2 positively-charged nuclei increases as the 2 nuclei come closer one another.

• When two nuclei come very close to one another at very high temp., the strong nuclear binding force predominates & allows the nuclei to fuse, releasing large amounts of energy. •The reaction products, helium and neutrons, may transfer their kinetic energy to a surrounding coolant. This heat may be used to generate electricity.

Hydrogen Fusion: Energy of the Stars

Stars have large amounts of hydrogen gas.

Four hydrogen atoms fuse forming 1 atom of helium

The mass of 4 hydrogen atoms is greater than the mass of 1 helium atom; the excess mass is converted to a tremendous amount of energy.

This hydrogen helium fusion can power a star for billions of years

Advantages of Fusion Reactors over Fission ones

Deuterium, a fusion fuel, is available in large supply. It can be extracted from ocean waters.

Fusion is relatively cleaner than fission, as no pollutants are released to the atmosphere.

Radioactive tritium is as chemically active as ordinary hydrogen. It may combine w/ oxygen to form radioactive water, although its radiation is weak.

Fusion also produces neutrons. When absorbed by nuclei, the latter can become radioactive. Neutrons are produced only as long as fusion reaction proceeds. When the reaction stops, neutron production also stops.

Scientists have spent around 40 years to make fusion work on Earth & expect to come up w/ the commercial application on 2020.

To make fusion happen, the atoms of hydrogen must be heated to very high temp. of around 100 million degrees C. At these temp., hydrogen gas is completely ionized forming plasma.

Plasma is a gas of charged particles.

Where to Contain the Plasma?

The sun and stars do this by gravity. The more practical approaches being used on Earth are Magnetic Confinement & Inertial Confinement.

Magnetic Confinement

a very strong magnetic field holds the ionized atoms together while they are continually heated by microwaves or other energy sources.

Inertial Confinement

a tiny pellet of frozen hydrogen is compressed and heated by an intense energy beam ,such as laser, so quickly so that fusion occurs even before the atoms can fly apart.

On Earth: Fusion Research On Earth scientists and engineers are working to

reproduce fusion on a smaller scale. However, this is a significant scientific and technical challenge. The Earth does not have the gravitational pressure of the Sun so plasma must be confined and heated to temperatures ten times higher than those in the Sun in order to get a sufficient number of fusion reactions.

Making fusion on Earth requires two heavier types (or isotopes) of hydrogen: deuterium - with a nucleus of one proton and one neutron (an atomic particle with similar mass to the proton but no electrical charge) and tritium (with one proton and two neutrons).

When these two nuclei fuse together they produce a new helium nucleus (also known as an alpha particle) and a high-energy neutron.

In a future fusion power plant, the energy of that neutron will be captured and used to heat steam to generate electricity as in a normal power station, while the electrically charged alpha particle will transfer its energy to the plasma, keeping it hot.

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