Question:medium

Nuclear reactor in which U-235 is used as fuel uses 2 kg of U-235 in 30 days. Then, power output of the reactor will be (given energy released per fission = 185 MeV):

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$1$ eV = $1.6 × 10^-19$ J.
Updated On: May 24, 2026
  • 43.5 MW
  • 58.5 MW
  • 69.6 MW
  • 73.1 MW
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The Correct Option is B

Solution and Explanation

To determine the power output of the nuclear reactor using U-235 as fuel, we need to follow these steps:

  1. Calculate the energy released per fission event in joules. The energy released per fission is given as 185 MeV. We convert this energy into joules using the conversion: \(1 \, \text{MeV} = 1.60218 \times 10^{-13} \, \text{J}\).
  2. Number of atoms of U-235 in 2 kg: The number of atoms is found using Avogadro's number and the molar mass of U-235, which is approximately 235 g/mol.
  3. Total energy released from 2 kg of U-235 is calculated by multiplying the energy per fission with the number of fission events.
  4. Calculate the power output: Power is energy per unit time. Use the total energy and the time period (30 days converted to seconds) to find power.

Let's perform these calculations:

  • Energy per fission in joules: \(185 \, \text{MeV} \times 1.60218 \times 10^{-13} \, \text{J/MeV} = 2.963 \times 10^{-11} \, \text{J}\)
  • The number of atoms in 2 kg of U-235: \(\frac{2 \times 10^3 \, \text{g}}{235 \, \text{g/mol}} \times 6.022 \times 10^{23} \, \text{atoms/mol} = 5.124 \times 10^{24} \, \text{atoms}\)
  • Total energy released: \(5.124 \times 10^{24} \, \text{atoms} \times 2.963 \times 10^{-11} \, \text{J} = 1.517 \times 10^{14} \, \text{J}\)
  • Time in seconds for 30 days: \(30 \times 24 \times 3600 = 2592000 \, \text{s}\)
  • Power output: \(\frac{1.517 \times 10^{14} \, \text{J}}{2592000 \, \text{s}} = 5.85 \times 10^{7} \, \text{W} = 58.5 \, \text{MW}\)

Therefore, the power output of the reactor is 58.5 MW.

The correct answer is thus: 58.5 MW

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