Nuclear energy

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Content – Forms of energy

 


 
Nuclear energy is the energy in the nucleus, or core, of an atom. Energy is what holds the nucleus together.

Nuclear energy can be used to create electricity, but it must first be released from the atom. In nuclear fission, atoms are split to release the energy.

In a nuclear power plant nuclear fission takes place at a controlled manner to produce electricity. The feed is pellets of uranium. In the reactor, atoms of uranium are broken apart. As they split, the atoms release small particles. The particles cause other uranium atoms to split, starting a chain reaction. The energy released from this chain reaction creates heat.

Fission and Fusion

There is basically one nuclear process currently used for commercial energy production, that is fission.

Fission

Fission implies splitting of large atoms normally uranium or plutonium into two smaller atoms,. To split an atom, it needs to be hit by a neutron. Several neutrons are then released splitting other nearby atoms, producing a nuclear chain reaction releasing substantial energy, generating heat that is normally turned into electricity.

Fusion

Fusion is combining two small atoms such as Hydrogen or Helium to produce heavier atoms and energy. These reactions can release more energy than fission without producing as many radioactive byproducts. Fusion reactions occur in the sun, generally using Hydrogen as fuel and producing Helium as waste. This reaction has not been commercially developed yet.

The table shows the energy density of a few materials. When uranium undergoes nuclear fission it attains a very high energy density.

MaterialEnergy Density (MJ/kg)
Wood14,5
Ethanol27
Coal33
Crude oil41.9
Diesel43,4
Natural Uranium (LWR)5.7×105
Thorium (breeder)7.9×107

Nuclear binding energy

The energy required to break down a nucleus into its component nucleons is called the nuclear binding energy.

Nuclear binding energy is usually expressed in terms of kJ/mole of nuclei or MeV/nucleon.

Formula – Nuclear energy

Mass defect and nuclear binding energy
The basis for calculating the nuclear binding energy for a substance is the equation.

E= mc^2  or
m= \dfrac{c^2}{E}

We first need to calculate the mass defect to to be able to calcutlate the potential for releasing energy when fission takes place.

To calculate the mass defect we subtract the nucleus mass of the base material from the combined mass of the base material components:

Mass c (combined mass)    = MP + MN (Mass Neutron)

MP =Mass Proton = nP*amuP

MN =Mass Neutron = nN*amuN

Dm = Mass c – MassBM

Then to convert the mass defect into energy we first need to convert the mass defect into the unit Kg and then into its energy equivalent:

Dm(amu) * 1.6606 x 10-27 kg/nucleus

1amu = 1.6606 x 10-27 kg

c = 2.9979 x 108 m/s

E = mc2 = (Dm(amu) *1.6606* 10-27 kg/nucleus) * (2.9979 x 108 m/s)2

E = DM*1,4924483 *10-10 J/nucleus

To convert this into KJ/Mol the following conversion applies:

E= DM*1,4924483 *10-10 J/nucleus * 6.022 x 1023 nuclei/mol* (1 kJ/1000 J) * = DM*8,9875 1010 kJ/mol of nuclei.

Avogadro’s Number = 6.022 x 1023 nuclei/mol