Nuclear Processes

1. Nuclear Processes Fission & Fusion

2. Fission vs. Fusion

3. Fission vs. Fusion • In nuclear fusion, two nuclei combine to form a more massive nucleus. • Fusionmeans the merging together of different elements to make a new element. • In nuclear fission, a massive nucleus splits into two lighter nuclei. • Fissionmeans breaking something up into parts.

4. Mass Energy Equivalence • In the nucleus the strong interaction binds the nucleons tightly together. • When nucleons are bound together by the strong interaction, their energy is reduced — they go into a low-energy state. • The binding energy of a nucleus is the energy required to break up the nucleus into its individual protons and neutrons.

5. Mass Energy Equivalence

6. Mass Defect • The law of conservation of mass says that mass is never created or destroyed. • It is surprising that accurate measurements show that a bit of mass disappears when nuclei form from their individual nucleons: • the mass of a nucleus is less than the sum of the masses of the individual protons and neutrons that make up the nucleus. • This missing mass is called the mass defect

7. Law of Conservation of Mass-Energy • Mass can be transformed into energy and energy can be transformed into mass. • This explains the mass defect: when nucleons are bound together, their energy is reduced, so their mass is also reduced. • The binding energy of a nucleus is the mass-energy equivalent of its mass defect.

8. Mass Energy Equivalence Determine the mass-energy equivalent of 1.0 kg of gasoline.

9. Nuclear Reactions

10. Nuclear Fission Fission is the reaction in which a massive nucleus splits into two or more lighter nuclei. • Spontaneous Fission: Spontaneous fission occurs when an unstable isotope splits into two or more smaller nuclei without any external interaction. • It is only seen in nuclei with atomic mass numbers above 230 (elements near thorium). • Induced Fission: a nucleus absorbs a neutron, forming a highly unstable isotope that breaks up almost instantly into two lighter nuclei

11. Nuclear Fission Thorium-230 decays to polonium-218 by three alpha decays. Write the equations for the reactions. Use a periodic table.

12. Nuclear Fission

13. Nuclear Fusion The dominant fusion reaction in stars the size of our Sun or smaller is the proton-proton chain.

14. Nuclear Fusion Another form of fusion is neutron absorption.