7 - 25 Fission and fusion
● Nuclear reactions, including fission, fusion and radioactive decay, can be sources
of energy
Nuclear fission (核裂變)
● ***Definition: splitting of large atomic nucleus into smaller nuclei (known as daughter
nuclei)
● E.g.: Uranium-235
○ Used as fuel in nuclear reactor, as its nuclei can be split by collision with a
neutron
○ A slow-moving neutron absorbed by a nucleus of U-235:
■ ↑ equation for decay:
U 236 144 89 1
92 → Ba56 + Kr 36 + 3 n0 (3 neutrons)+ γ radiation (+kinetic energy)
○ In nuclear power station, the 3 neutrons emitted by fission of 1 U-235 nucleus
hit other 3 U-235 nuclei respectively, each U-235 nucleus emits another 3
neutrons etc.; process called chain reaction
1
, ○
2
● Nuclear reactions, including fission, fusion and radioactive decay, can be sources
of energy
Nuclear fission (核裂變)
● ***Definition: splitting of large atomic nucleus into smaller nuclei (known as daughter
nuclei)
● E.g.: Uranium-235
○ Used as fuel in nuclear reactor, as its nuclei can be split by collision with a
neutron
○ A slow-moving neutron absorbed by a nucleus of U-235:
■ ↑ equation for decay:
U 236 144 89 1
92 → Ba56 + Kr 36 + 3 n0 (3 neutrons)+ γ radiation (+kinetic energy)
○ In nuclear power station, the 3 neutrons emitted by fission of 1 U-235 nucleus
hit other 3 U-235 nuclei respectively, each U-235 nucleus emits another 3
neutrons etc.; process called chain reaction
1
, ○
2
