Nuclear Fission

Nuclear reaction in radioactive elements

What is Nuclear reaction?

There are two types of nuclear reaction in radioactive elements – they are nuclear fission and nuclear fusion

Nuclear fission

This is nuclear reaction which can be defined as a process in which an unstable nucleus split into two parts of comparable mass.
Fusion was discovered by Hann and strassman in 1938, when they bombarded uranium (Z=96) with neutrons. They found the resulting radiation to be a radioactive isotope of barium (Z=56) and krypton(Z=36). These results were interpreted as showing that uranium nuclei were splitting into two parts (fragments) called the fission fragments. Also in this nuclear reaction, two or three neutrons also appear along with the fission fragments.

Examples of fission

{ { { \begin{matrix} 235 \\ 92 \end{matrix}U+\begin{matrix} 1 \\ o \end{matrix}n\longrightarrow \begin{matrix} 144 \\ 56 \end{matrix}Ba+\begin{matrix} 89 \\ 36 \end{matrix}Kr+3\begin{matrix} 1 \\ 0 \end{matrix}n+Q } } }

{ { { { \begin{matrix} 235 \\ 92 \end{matrix}U+\begin{matrix} 1 \\ o \end{matrix}n\longrightarrow \begin{matrix} 148 \\ 37 \end{matrix}La+\begin{matrix} 85 \\ 35 \end{matrix}Br+3\begin{matrix} 1 \\ 0 \end{matrix}n+Q } } } } 

Where Q =Nuclear energy produced

The total energy of fission fragment is about 200MeV

Nuclear fusion

It is also nuclear reaction, and is   define as a process whereby two or more light nuclei join together to form a heavy nucleus with release of enormous energy

Binding energy

The neutrons and protons in a stable nucleus by nuclear forces , so to pull them apart energy is needed and this energy needed is called the binding energy of nucleus. The greater the binding energy the more stable is the nucleus

The Einstein mass energy relation

In 1905, Albert Einstein published his special theory of relativity, one of the conclusion from this is that mass and energy are equivalent and they are related by the equation E=∆mc2

The difference between the masses before and after reaction, ∆m, correspond to the reaction energy, E, where C is the speed of electromagnetic radiation. For ∆m to equal 1 kg, the amount of energy produced is 9x1016J. Conversely, a 1Mev gamma ray can be converted into a given mass of 1.78 x10-30Kg

Chain reactions in nuclear reaction

If one of the neutrons produced by the first fission hits a second uranium nucleus the letter will also split and the process will continue causing a very number of fission reactions. This reaction is called chain reaction.
A chain reaction occurs on the fission of uranium only when the quantity of uranium is large.
If uranium is small and undergoes fission reaction the secondary neutrons escape from the sides before they cause fission. So to sustain chain reaction there must be sufficient pure uranium-235 known as the critical mass to avoid neutrons from being lost from the sides before they cause further fission

Atomic bomb chain nuclear reaction

Atomic bomb explosion occurred when two pieces of uranium with both masses below the critical mass whose sum is greater than the critical mass are brought together at the right time. Then there will be an increase in uncontrolled chain reaction and massive explosion with extensive destructive effects

Nuclear reactor

Nuclear reactor is a system in which a controlled nuclear chain reaction is used to produce energy. In a nuclear power plant the energy is used to generate steam which operate a turbine and rotate electric generator( dynamo) . The main application of nuclear reactors is for generation of electric power.

Other application include

(a) production of artificial radioactive elements or isotopes
(b) for medical research
(c) for production of high intensity neutron beams and fissionable nuclides

Advantages of fusion over fission (nuclear reaction)

1. Fusion is easily achieved with hydrogen
2. The raw materials required for fusion are more readily available
3. Fusion produces less dangerous by-products
4. Fission reaction produces much larger release of nuclear energy

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