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The energy of the fast neutrons emitted in a nuclear fission reactor is approximately

Asked in GUJCET 2018 · Reactors and conditions for fission and fusion

Answer: (1) 2 MeV

Step-by-step solution

Idea: the neutrons that come out at the instant of fission are called fast neutrons — they are born with a share of the ≈200 MeV released, not with thermal energy.

Their average kinetic energy is about 2 MeV.

That is exactly why a thermal reactor needs a moderator: these neutrons must be slowed to about 0.03 eV before ²³⁵₉₂U will capture them efficiently and keep the chain reaction going.

So the answer is about 2 MeV.

Why the other options are wrong

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