The atomic number of uranium-235 is 92, its half-life is 704 million years and the radioactive decay of l kg of 235U releases 6.7X10^13 J. Generally, radioactive material is considered safe after 10 half-lives.
Assume that a nuclear powerplant can convert energy from 235U into electricity with an efficiency of 35%, the electrical transmission lines operate at 90% efficiency, and flourescent lights operate at 22% efficiency.
1.) What is the overall efficiency of converting the energy of 235U into flourescent light?
2.) How much energy from 1 kg of 235U is converted into flourescent light?
1) Let us say that x energy is available in the Uranium. Conversion to electricity: 0.35x Transmission efficiency = 0.9 x 0.35 = 0.315x Light efficiency = 0.22 x 0.315x = 0.0693x
Overall efficiency = 0.0693 * 100 = 6.93%
2) Energy released = 6.7 x 10¹³ J Energy converted = 6.7 x 10¹³ x 0.0693 = 4.64 x 10¹² Joules
