In nuclear engineering and basic reactor physics, approximately how much energy (in mega–electron volts, MeV) is released by the fission of a single atom of uranium-235? Provide the closest standard textbook value used for energy balance calculations.

Introduction:
Nuclear fission of uranium-235 is the cornerstone of many reactor energy calculations. Each fission event converts a tiny amount of mass into energy, distributed among fast fission fragments, prompt and delayed neutrons, prompt and delayed gamma radiation, and the kinetic energy imparted to the recoiling nucleus. Knowing the approximate energy per fission allows quick estimates of heat generation, fuel burnup, and shielding requirements.

Given Data / Assumptions:

• The question asks for the widely accepted average energy release per fission of a single U-235 nucleus.
• We assume thermal-neutron-induced fission and the usual partition of energies among products.
• Answer should be rounded to a convenient, commonly quoted figure for engineering use.

Concept / Approach:
Binding energy differences between the parent U-235 plus a neutron and the daughter fission fragments account for the energy release. Detailed accounting typically gives about 170–180 MeV as kinetic energy of fragments, several MeV in prompt neutrons, around 6–7 MeV in prompt gammas, and additional MeV in beta and gamma from fission-product decay and neutrinos. The gross heat available to the reactor coolant (excluding energy carried by neutrinos) is close to 200 MeV per fission, which is the canonical value used in reactor thermal calculations.

Step-by-Step Solution:
Recall standard breakdown: ~170 MeV fragment kinetic + ~5 MeV prompt neutrons + ~7 MeV prompt gammas + ~6 MeV beta/gamma from decay ≈ ~188 MeV recoverable as heat.Include additional small contributions (capture gammas, etc.) and round to the engineering figure used in textbooks.Adopt the conventional number: approximately 200 MeV per U-235 fission.

Verification / Alternative check:
Reactor heat balance problems, fuel burnup tables, and shielding texts consistently treat the per-fission energy as ~200 MeV, which corresponds to about 3.2 × 10^-11 joule per fission when converted using 1 eV = 1.602 × 10^-19 J.

Why Other Options Are Wrong:

• 20 MeV: An order of magnitude too low; underestimates fragment kinetic energy.
• 500 or 1000 MeV: Far too high for fission; values of that scale are associated with high-energy particle interactions, not thermal-neutron fission of U-235.
• 150 MeV: Closer, but still low compared to the standard engineering figure.

Common Pitfalls:
Confusing total emitted energy with heat recoverable in the coolant. A small fraction is carried away by neutrinos and is not captured as heat, yet the engineering convention still quotes ~200 MeV for convenient calculations.

Final Answer:
200