A thermal nuclear reactor uses enriched uranium as its fuel. This is fuel in which the ratio of U-235 to U-238 has been artificially increased from that found in naturally-occurring ore.
Explain the interactions of neutrons with U-235 and U-238 nuclei in a thermal nuclear reactor, describing how each isotope responds.
The amounts of U-235 and U-238 in natural uranium ore decrease over time due to radioactive decay at different rates.
A sample of uranium ore today contains 850 g850\text{ g}850 g of U-238. The mass of U-238 in this sample was greater 2.50×109 years2.50 \times 10^9\text{ years}2.50×109 years ago.
Show that the mass of U-238 in this sample at that time was about 1.25 kg1.25\text{ kg}1.25 kg.
decay constant of U-238 =1.54×10−10 year−1= 1.54 \times 10^{-10}\text{ year}^{-1}=1.54×10−10 year−1
A thermal nuclear reactor requires a minimum of 3.0%3.0\%3.0% of its total uranium mass to be U-235.
2.50×109 years2.50 \times 10^9\text{ years}2.50×109 years ago, the sample from part 2 contained 42 g42\text{ g}42 g of U-235.
Deduce whether the sample had a high enough U-235 content to be used in a thermal nuclear reactor at that time.
