# Nuclear energy

Nuclear energy is the energy given off during a nuclear reaction. There are 2 types of Nuclear reactions Fission (sounds like division) and Fusion (to fuse to things together), these reactions give off energy

Nuclear is a form of energy we can harness

The following is when, where and who made it come true, with a brief description of the nature of this energy.

http://www.sei.ie/Schools/Secondary_Schools/Subjects/Physics/Unit_2_-_Energy/Mass_as_Energy/

Principles of fission and fusion.

Fission is when one atom splits up and becomes at least two other atoms. This only happens on the occasion if a huge impact causes the larger parent atom to rupture. One such way of causing this to happen is the bombarding of large atoms with neutrons. Like i said before Fission sounds like division, this might help you remember what is happening. The atom is dividing into smaller pieces.

*not to scale

The blue dots are neutrons, these have a small mass of 1.009 amu.

The letters AMU stands for atomic mass units, 1 amu = 1.660467x10-27 kg. Not very big.

Okay so lets add up the masses on the left and on the right .... your turn.

n + U =

Mo + La + 2n =

Are they the same ?

Where does the mass difference go ?

With the exception of 1H, the experimentally determined mass of an atom is always less than the sum of the masses of the component particles (protons, neutrons, and electrons) by an amount called the mass defect of the nucleus. The energy corresponding to the mass defect is the nuclear binding energy, the amount of energy released when a nucleus forms from its component particles. In nuclear fission, nuclei split into lighter nuclei with an accompanying release of multiple neutrons and large amounts of energy. The critical mass is the minimum mass required to support a self-sustaining nuclear chain reaction. Nuclear fusion is a process in which two light nuclei combine to produce a heavier nucleus plus a great deal of energy.

So calculate the difference in mass, remember if the products are lighter than the reactants this mass difference is actually converted into energy by the formula E = mc2, so calculate the loss in masses and thus the energy liberated from the mass

Harnessing Energy from Nuclear Fusion

Fission Reactor

A simulation on Uranium 235, showing the use of moderators (neutron absorbers)

http://library.thinkquest.org/17940/texts/java/Reaction.html

no longer in service :(

The 4 typical reactions of U235 + a neutron are

fix this

use the masses in the maths tables.

In classical physics, mass and energy are separately conserved. In an explosion, if all the debris including even gaseous material were to be recoverable, it would be found that the number of individual atoms had not changed. In 1905 however, Einstein in his theory of Special Relativity had predicted that mass itself is a form of energy and that a stationary mass m has a ‘rest’ energy of mc2 where c is the velocity of light in a vacuum. In nuclear reactions such as radioactive decay, where one nucleus is transformed into another, it is the conservation of total (i.e. rest + kinetic) energy

together with the conservation of momentum that governs the process. It is customary in atomic, nuclear and particle physics to use the electron volt as a unit of energy, because the joule is a very large unit in this context.

The uranium decays at rest so that the two decay products must leave in opposite directions to conserve momentum

Enriching Uranium

Enriching Uranium, really means to increase the amount of fissible material U235 in a sample of Uranium.

Most of the 495 commercial nuclear power reactors operating or under construction in the world today require uranium 'enriched' in the U-235 isotope for their fuel.

Uranium found in nature consists largely of two isotopes, U-235 and U-238. The production of energy in nuclear reactors is from the 'fission' or splitting of the U-235 atoms, a process which releases energy in the form of heat. U-235 is the main fissile isotope of uranium.

U235 will fission / split when a neutron strikes it, but U238 will absorb the neutron which makes it useless to sustain a nuclear reaction

Natural uranium contains 0.7% of the U-235 isotope. The remaining 99.3% is mostly the U-238 isotope which does not contribute directly to the fission process (though it does so indirectly by the formation of fissile isotopes of plutonium). Most reactors are Light Water Reactors (of two types - PWR and BWR) and require uranium to be enriched from 0.7% to 3% to 5% U-235 in their fuel.

http://world-nuclear.org

FUSION,

Fusion

Especially read how Leo Szilard changed the world.

less harmful by-products

More abundant raw material

less harmful by-products

Mass-energy conservation in nuclear reactions: E = mc2

Mass and energy are equivalent and can be interchanged.

Einstein’s equation, E = mc2, relates mass and its energy equivalent.

Conversion of mass to energy is the source of the energy released in nuclear reactors.

1 atomic mass unit of mass, when anhilitated, provides 931 MeV of energy.

When fission occurs, the products have less mass than the reactants. That is, in the above reaction one atom of Beryllium 141, one atom of Krypton 92, and three neutrons have less mass than one atom of Uranium 235 and one neutron. This loss of mass is realized as an increase in energy according to Einstein's equation E = mc2.

a whole site devoted to Albert Einstein

More energy available

Fission of Pu-239: 17.3 kt/kg

Fusion of pure deuterium: 82.2 kt/kg

Appropriate calculations.

The Sterritt debate ....

Fusion Vs Fission

Nuclear reactor (fuel, moderator, control rods, shielding, and heat exchanger).

A moderator slows down the neutron, this makes them less likely to be absorbed by U238 and leaves more neutrons for the U235.

So a moderator keeps the nuclear reaction going.

Games Nuclear plant

http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway/living_future/3_fuels_for_power3.shtml

Fusion: source of Sun’s energy.

The sun produces a vast amount of energy as about 6 × 108 tonnes of hydrogen are converted every second. The earth, because of its size and distance from the sun, receives about 0.00000005% of this energy as heat and light.

Nuclear weapons.

for all you need to know about nukes !

http://physics.info/weapons/

Environmental impact of fission reactors.

The shares of individual countries with respect to the world total consumption of nuclear energy

When things go wrong Japan March 2011

http://www.bbc.co.uk/news/world-asia-pacific-12726591

And the continuing saga of the Japanese Reactors ....

http://c21.phas.ubc.ca/article/why-cant-you-just-turn-nuclear-reactor

Development of fusion reactors.

Audiovisual resource material.

Interpretation of nuclear reactions.