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Nuclear Fission and Fusion


Akoranga 9 Ngā Whāinga Ako 🔗


Recall 🔗

There are three types of nuclear reactions

  1. Radioactive decay ($\alpha$, $\beta$, $\gamma$)
  2. Nuclear fission
  3. Nuclear fusion

Fission 🔗


Question 🔗

If the protons are positively charged, why don’t they repel each other and the nucleus break apart?


Electrostatic Force vs. Nuclear Force 🔗


Radioactive Isotopes 🔗


Absorption of a Nucleon 🔗


Pātai: Write 2x nuclear equations to express this reaction 🔗


Whakatika 🔗

\begin{aligned} & {}^{1}{0}n + {}^{235}{92}U \rightarrow {}^{236}{92}U \
& {}^{236}
{92}U \rightarrow {}^{92}{36}Kr + {}^{141}{56}Ba + 3{}^{1}_{0}n \end{aligned}

Extra pātai: What do you think the three neutrons produced do?



Nuclear Fusion 🔗


Whakatika 🔗

\begin{aligned} & {}^{3}{1}H + {}^{2}{1}H \rightarrow {}^{4}{2}He + {}^{1}{0}n \end{aligned}


Producing Energy: Mass Balance 🔗

\begin{aligned} & {}^{3}{1}H + {}^{2}{1}H \rightarrow {}^{4}{2}He + {}^{1}{0}n \end{aligned}

  1. Calculate the total mass of the reactants.
  2. Calculate the total mass of the products.

Theory of Relativity, $E = mc^{2}$ 🔗


During the fusion process, the total mass is not conserved because some of the mass of the fusing nuclei is converted to energy.

\begin{aligned} & E = mc^{2} \end{aligned}


Pātai: Smoke Detector 🔗



Pātai: Nuclear Fission 🔗


Pātai: Nuclear Reactor 🔗


Tips for the Assessment 🔗

  1. EXPLAIN your answers.
  2. Watch out for the numbers NOT in standard forms (e.g. $\times 10^{-27}$)
  3. Half-life – Draw a graph!!!
    • Don’t forget about the shape of the exponential curve
  4. Nuclear Equations – double check the atomic numbers and the mass numbers
  5. $E = mc^{2}$ – SHOW CLEAR WORKING