Fiche de révision : Nuclear Energy Principles and Reactions

📋 Course Outline

1. Mass-energy equivalence
2. Nuclear binding and mass defect
3. Deuterium binding energy
4. Alpha decay and energy release
5. Nuclear fusion and energy yield
6. Nuclear fission and chain reactions

📖 1. Mass-energy equivalence

🔑 Key Concepts & Definitions

• Mass-energy equivalence : Mass-energy equivalence is the idea that mass can be converted into energy and energy can be converted into mass.
• Einstein’s formula $E=mc^2$ : Einstein’s formula states that energy equals mass times the speed of light squared.
• Speed of light $c$ : The speed of light $c$ is the constant used in $E=mc^2$, given as $2,997\,924\,58\cdot10^8$ m/s and often rounded to $3,00\cdot10^8$ m/s.
• Energy unit J : In this framework, energy $E$ is expressed in joules (J) when using $m$ in kilograms.

📝 Essential Points

• Using $E=mc^2$, converting $1,00$ kg gives $E=(1,00)\,(c)^2$ joules.
• With $c\approx 3,00\cdot10^8$ m/s, the rounded energy conversion for $1,00$ kg is computed from $E=m(3,00\cdot10^8)^2$.
• $\text{Doel 4}$ has a maximal capacity of $10^{39}$ MW, so the time to match the energy from $1,00$ kg is found by dividing that energy by the power $10^{39}$ MW converted to J/s.

💡 Memory Hook

$E$ grows with $c^2$, so even small masses release enormous energy.

📖 2. Nuclear binding and mass defect

🔑 Key Concepts & Definitions

• Mass defect $\Delta m$ : Mass defect is the difference between the sum of the individual nucleon masses and the mass of the assembled nucleus.
• Strong nuclear force : The strong nuclear force is an attractive force that holds nucleons together at very short distance despite proton repulsion.
• Proton repulsion : Proton charges being positive creates an electric repulsive force that tends to push nucleons apart within a nucleus.
• Released energy $\Delta E=\Delta m\,c^2$ : Released energy equals the mass defect multiplied by $c^2$, for nuclear reactions where mass is converted into energy.

📝 Essential Points

• The source links nuclear stability to strong nuclear attraction counteracting electric repulsion between protons.
• The mass defect is computed as $\Delta m=m_{\text{particles}}-m_{\text{noyau}}$.
• The mass defect corresponds to “mass that disappeared” converted into energy and released in nuclear reactions.
• For any nuclear reaction with converted mass, the same relation $\Delta E=\Delta m\,c^2$ is used to compute released energy.

💡 Memory Hook

If $m_{\text{nucleus}}$ is smaller than $m_{\text{nucleons}}$, the missing mass becomes energy.

📖 3. Deuterium binding energy

🔑 Key Concepts & Definitions

• Deuterium nucleus $^2_1H$ : Deuterium is hydrogen whose nucleus contains one proton and one neutron.
• Deuterium mass values : The source provides an experimental deuterium nucleus mass and the sum mass of free proton and neutron used to form a mass defect.
• Deuterium mass defect $\Delta m$ : For deuterium, the mass defect is the difference between free nucleon masses and the measured deuterium nucleus mass.
• Deuterium released energy $\Delta E$ : The deuterium binding-related energy is obtained by converting the deuterium mass defect into energy using $\Delta E=\Delta m\,c^2$.

📝 Essential Points

• The source gives $m_{\text{noyau}}=3,34348590\cdot10^{-27}$ kg for a deuterium nucleus.
• The sum of free nucleon masses is $m_{\text{particules}}=m_{\text{proton}}+m_{\text{neutron}}=3,3475517\cdot10^{-27}$ kg.
• The mass of a nucleus is less than the sum of individual nucleon masses, so $\Delta m=m_{\text{particules}}-m_{\text{noyau}}$ is positive.
• The source explicitly states that the energy corresponding to $\Delta m$ is released when a proton and neutron combine into a deuterium nucleus.

💡 Memory Hook

Measure nucleus mass, subtract from free nucleon sum, then multiply by $c^2$.

📖 4. Alpha decay and energy release

🔑 Key Concepts & Definitions

• Alpha decay : Alpha decay is radioactive decay where an unstable nucleus emits an alpha particle.
• Alpha emitter Po-218 : The source states that $^{218}_{84}\text{Po}$ is an alpha emitter.
• Total energy released $\Delta E$ : Total released energy in decay is the energy associated with the mass change using $\Delta E=\Delta m\,c^2$.
• Decay equation : A decay equation is the conservation-based nuclear reaction written for a nucleus transforming after emission.

📝 Essential Points

• For $^{218}_{84}\text{Po}$ alpha decay, the source asks you to write the disintegration equation for the process.
• The source asks for the total energy released by this alpha radiation using a mass-change energy calculation.
• When computing decay energy from mass change, the same mass-to-energy method from $\Delta E=\Delta m\,c^2$ applies.

💡 Memory Hook

Write the decay equation first, then convert the mass change into $\Delta E$ with $c^2$.

📖 5. Nuclear fusion and energy yield

🔑 Key Concepts & Definitions

• Nuclear fusion : Nuclear fusion is the process in which two light nuclei combine to form a heavier nucleus.
• Fusion reaction in a reactor : The source’s fusion reaction is given explicitly for a fusion reactor setting.
• Hydrogen isotopes $H^2_1$ and $H^3_1$ : The source labels the reacting hydrogen isotopes in the fusion reaction as $H^2_1$ and $H^3_1$.
• Energy yield from mass change : The energy yield in fusion is obtained from the conversion of a fusion mass defect into energy using $\Delta E=\Delta m\,c^2$.

📝 Essential Points

• The source fusion reaction is $H^2_1+H^3_1\rightarrow He^4_2+n^1_0$.
• For the fusion reaction, the source asks for the percent of total mass converted into energy.
• For that same reaction, the energy released “per $He$-4 nucleus” is computed from the reaction’s mass difference using $\Delta E=\Delta m\,c^2$.

💡 Memory Hook

Fusion: add light nuclei, subtract final mass, convert the missing mass to energy.

📖 6. Nuclear fission and chain reactions

🔑 Key Concepts & Definitions

• Nuclear fission : Nuclear fission is when a heavy nucleus splits into smaller nuclei, releasing energy as part of the mass converts to energy.
• Fission sites : In practice, the source places fission in nuclear power plants and atomic bombs.
• Nuclear chain reaction : A nuclear chain reaction is a sequence where fission releases neutrons that can trigger further fission events.
• Multiplication factor $n$ : The source defines $n$ as the average number of new fissions triggered by one fission.
• Neutron slowing in water : The source states that neutrons must be slowed in water before they can induce further uranium fission.

📝 Essential Points

• Fission in the source uses heavy nuclei bombarded with neutrons until the nucleus becomes unstable and breaks into smaller nuclei.
• The source’s fission example is triggered when $^{235}_{92}U$ absorbs a neutron and produces $^{89}_{36}Kr$, $^{144}_{56}Ba$, and three neutrons.
• The source provides the mass-equation form $m_{\text{before}}=m_{\text{after}}+\Delta m$ for the process and asks you to compute the released energy $\Delta E_0$ from that $\Delta m$.
• Chain reaction behavior depends on $n$: $n=1$ keeps power constant, $n<1$ ends the reaction, and $n>1$ increases fissions per second and power.
• In a reactor, the source states that neutrons are slowed in water, then can cause fission of new uranium nuclei to continue the chain reaction.

💡 Memory Hook

Think “domino”: each fission may knock over $n$ more fissions.

⚠️ Common Pitfalls & Confusions

1. Students may mix up $m_{\text{particules}}-m_{\text{noyau}}$ with $m_{\text{noyau}}-m_{\text{particules}}$, flipping the sign of $\Delta m$.
2. Students may confuse nuclear fusion and nuclear fission, which the source treats as different processes.
3. Students may use the rounded $c=3,00\cdot10^8$ m/s in one step and the exact $c=2,997\,924\,58\cdot10^8$ m/s in another without consistency.
4. Students may compute chain reaction outcomes by thinking $n$ is “neutrons released” instead of “new fissions triggered on average.”
5. Students may forget that the source’s fusion and fission examples include specific emitted particles (like neutrons) and must be included in reaction bookkeeping.
6. Students may treat the “missing mass” as lost rather than converted into energy using $\Delta E=\Delta m\,c^2$.
7. Students may interpret “energy release per $He$-4 nucleus” as the reaction total rather than computing using the $He^4_2$ produced in the reaction step.

✅ Exam Checklist

1. Use $E=mc^2$ with the given $c$ values to compute the energy released for converting $1,00$ kg of mass.
2. Convert the energy from $1,00$ kg into a production time by dividing by $10^{39}$ MW (Doel 4 maximum), converting MW to J/s.
3. Define mass defect $\Delta m$ and write its calculation formula $\Delta m=m_{\text{particules}}-m_{\text{noyau}}$.
4. Explain, using the source’s forces, why the nucleus does not disintegrate despite electric proton repulsion.
5. Compute the energy released from a mass defect using $\Delta E=\Delta m\,c^2$.
6. For deuterium, use the provided values $m_{\text{noyau}}=3,34348590\cdot10^{-27}$ kg and $m_{\text{particules}}=3,3475517\cdot10^{-27}$ kg to find $\Delta m$ and then $\Delta E$.
7. For $^{218}_{84}\text{Po}$, write the alpha-decay disintegration equation and calculate the total released energy from the mass change.
8. For the given fusion reaction $H^2_1+H^3_1\rightarrow He^4_2+n^1_0$, compute (i) the percent of total mass converted to energy and (ii) the energy released per $He$-4 nucleus.
9. For the given fission example starting from $^{235}_{92}U$ absorption of a neutron, write the reaction equation.
10. Use the source’s mass-equation form $m_{\text{before}}=m_{\text{after}}+\Delta m$ to compute the released energy $\Delta E_0$ for that fission.
11. Determine which regime applies from the sign of $n$: constant power ($n=1$), shutdown ($n<1$), or growth ($n>1$).