Natural Nuclear Reactor at Oklo

In 1972, French scientists discovered a natural nuclear reactor at the Oklo mine in Gabon. They found less Uranium-235 than expected, leading to the realization that a natural reactor had existed there two billion years ago. This reactor functioned with Uranium-235, neutrons, and groundwater, which controlled the reaction by slowing down neutrons. The reactor cycled on and off for thousands of years, eventually depleting its Uranium-235 and ceasing operation. This discovery showed that nature had created a nuclear reactor long before humans did.

What unusual observation did French scientists make at the Oklo mine in 1972?

• The discovery of a new element

• An increase in uranium concentration

• A lower concentration of Uranium-235 than expected

• The presence of a new uranium isotope

What is the key isotope needed for nuclear reactions that was found at Oklo?

• Thorium-232

• Uranium-235

• Plutonium-239

• Uranium-238

Which of the following is NOT a condition necessary for a natural nuclear reactor?

• Neutrons to initiate the reaction

• High temperatures

• A method to control the reaction

• Presence of Uranium-235

How did the groundwater at Oklo contribute to the reactor's operation?

• It absorbed excess energy

• It increased the temperature

• It provided additional uranium

• It slowed down neutrons to sustain the reaction

What happened when the groundwater at Oklo boiled off?

• The reaction intensified

• The reactor exploded

• The uranium concentration increased

• The reaction stopped

For approximately how long did the natural reactor at Oklo operate?

• Thousands of years

• Millions of years

• Hundreds of thousands of years

• A few years

What eventually caused the natural reactor at Oklo to stop?

• A natural disaster

• The depletion of Uranium-235

• An increase in water levels

• A decrease in neutron production

What was the average power output of the Oklo reactor?

• 10 kilowatts

• 50 kilowatts

• 100 kilowatts

• 200 kilowatts

What does the Oklo discovery demonstrate about nature?

• Nature cannot sustain nuclear reactions

• Nature's reactors are more powerful than human-made ones

• Nature can create nuclear reactors

• Nature relies on human intervention for nuclear reactions

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