Nuclear Fission

Nuclear Reaction

1. In a nuclear reaction, the mass of the parent particles will become less (know as mass defect). The defected mass is then converted into energy called the nuclear energy.
2. In short, nuclear energy is the energy released owing to the defect of mass in a nuclear reaction.
3. There are 2 types of nuclear reaction
1. nuclear fission
2. nuclear fusion
4. Nuclear fission is the process of splitting nucleus into 2 smaller nuclei whereas nuclear fusion is the process which 2 small nuclei combine to form a larger nucleus.

Nuclear Fission

1. Nuclear fission is a process involving the splitting of a heavy nucleus into two nuclei of roughly equal mass and shooting out several neutrons at the same time.
2. Nuclear fission seldom occurs spontaneously. Usually, it occurs when the heavy nucleus is bombarded by a neutron.
3. Fission reaction resulting from neutron absorption is called induced fission. Nuclei that undergo fission without initial neutron absorption are undergoing spontaneous fission.
4. Two typical examples of fission reactions:
1. $U+n\to Ba+Kr+3n+Energy$
2. $U+n\to Xe+Sr+2n+Energy$

Example 1
In a nuclear reaction, the mass difference in the reaction is 1.5 x 10^-8kg. Find the heat released in this reaction. [Speed of light = 3.0 x 10⁸ ms^-1]

Answer:
Mass defect, m = 1.5 x 10^-8kg
Heat released,
$$\begin{array}{l}E=m{c}^2\\ E=(1.5\times {10}^{-8}){\left(3.0\times {10}^8\right)}^2\\ E=1.35\times {10}^{9}J\end{array}$$

Example 2
A nuclear explosion released 8.2 x 10¹³ J of energy. What is the mass defect of uranium-235 in this reaction?
[Speed of light = 3.0 x 10⁸ ms^-1]

Answer
$$\begin{array}{l}E=m{c}^2\\ (8.2\times {10}^{13})=m{\left(3.0\times {10}^8\right)}^2\\ m=\frac{8.2\times {10}^{13}}{{\left(3.0\times {10}^8\right)}^2}\\ m=9.11\times {10}^{-4}kg=0.911g\end{array}$$