In a nuclear reactor operating at 100 MW, each fission event releases 250 MeV of energy and liberates an average of 2.5 neutrons. How many neutrons are produced per second?

2.5 * 10¹⁸
2.5 * 10¹⁹
6.25 * 10¹⁸
6.25 * 10¹⁹

Correct answer: 6.25 * 10¹⁸

Solution

Fissions per second = Power / Energy per fission = 10⁸ / (4 * 10⁻¹¹) = 2.5 * 10¹⁸. Neutrons per second = 2.5 * 2.5 * 10¹⁸ = 6.25 * 10¹⁸.

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