Natural uranium isotopic composition Identify the approximate fractional composition of the three naturally occurring uranium isotopes in un-enriched natural uranium by percentage.

Introduction / Context:
Natural uranium consists primarily of U-238 with small fractions of U-235 and a trace of U-234. Knowing these percentages is essential for reactor fuel discussions, enrichment calculations, and neutron economy considerations.

Given Data / Assumptions:

• Material: natural (un-enriched) uranium.
• Three isotopes considered: U-238, U-235, U-234.
• We seek widely accepted average percentages.

Concept / Approach:
Standard references report natural uranium as roughly U-238 ≈ 99.28%, U-235 ≈ 0.71%, and U-234 ≈ 0.005–0.006%. Minor variations occur by deposit and measurement method, but these values are the canonical figures used in educational settings.

Step-by-Step Solution:
Select the option with U-238 near 99.28%.Ensure U-235 is about 0.71% and U-234 a trace near 0.006%.Option (a) matches the accepted composition.

Verification / Alternative check:
Reactor physics texts and nuclear data tables corroborate these percentages used in enrichment benchmarks.

Why Other Options Are Wrong:

• Swapped or exaggerated values contradict known natural abundances.
• Any option making U-235 or U-234 the dominant isotope is physically incorrect for natural uranium.

Common Pitfalls:
Confusing the composition of enriched uranium (higher U-235) with natural uranium.

Final Answer:
U234 = 0.006%, U235 = 0.712%, U238 = 99.282%