A2 Daily A Level Physics question

A researcher compares the energy released per initial nucleon in two devices: a D–T fusion plasma where D + T → He‑4 + n, and a thermal reactor where U‑235 typically fissions into two fragments near A ≈ 120. Use these approximate average binding energies per nucleon: D ≈ 1.1 MeV; T ≈ 2.8 MeV; He‑4 ≈ 7.1 MeV; U‑235 ≈ 7.6 MeV; typical fission fragments near A ≈ 120 ≈ 8.5 MeV. Which statement must be true based on a one‑step estimate using changes in binding energy per nucleon?

1. A Fission gives more energy per initial nucleon; it is roughly three to four times that from D–T fusion on this basis.
2. B The energy released per initial nucleon is about the same for both processes, differing by less than around 10%.
3. C D–T fusion releases several times more energy per initial nucleon than U‑235 fission, because the increase in average binding energy per nucleon is about 3–4 MeV for fusion but only about 1 MeV for fission. (correct)
4. D Neither comparison is valid here, because the nucleon count changes in fusion and binding energy per nucleon cannot be used to estimate the energy change.