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Curtin University
Oklo Fossil Reactors

Things to do and think about

Not all the answers are available on these pages (try searching the web yourself to find the answers).

  1. Who predicted the existence of and who discovered the first natural fission reactors?
  2. What are the critical factors needed to start a nuclear (natural or man made) fission reactor?
  3. Why is the 235U/235U ratio an important indicator for the presence of a natural nuclear reactor?
  4. What other factor (beside the U isotope ratio) confirmed the natural nature of the nuclear reactions at Oklo?
  5. How many years are there between:
    • the operation of the Oklo ‘natural’ and first ‘man made’ fission reactors?
    • the first man made natural reactor and the prediction of natural fission reactors
    • the prediction and the discovery of natural fission reactors
  6. What role did Enrico Fermi play in the development of the first man made nuclear reactor?
  7. The actual shape of fission reactors (man made or natural) is critical to their operation. This is because, to sustain the chain reaction, it is important to retain as many neutrons as possible inside the reactor. To illustrate this:
    • draw on a piece of graph paper as many shapes as you can (rectangles, squares, circles, ovals etc) each having approximately the same area.
    • Determine the area (A) of each shape (count up the number of small squares inside the shapes
    • Now measure or calculate the perimeter or distance (d) around the outside of each shape.
    • Calculate the area (A) to perimeter (d) ratio (A/d).
    • Shapes with the highest A/d ratio will be the most efficient for a fission reactor – can you think why this would be so?
    • The above example is for a 2 dimensional structure but what would be the case for a 3 dimensional structure?
  8. In the year 5025, USS Enterprise astronauts orbit the planet Taurus V and detect large amounts of concentrated U undergoing fission. Based on this, what can you say about the age, geology and life forms on Taurus V ?

If you get stuck or you are curious to find out more email the author (Dr Robert Loss) at: r.loss@curtin.edu.au