Natural uranium isotopic composition Identify the approximate fractional composition of the three naturally occurring uranium isotopes in un-enriched natural uranium by percentage.
-
AU234 = 0.006%, U235 = 0.712%, U238 = 99.282%
-
BU234 = 0.712%, U235 = 0.006%, U238 = 99.282%
-
CU234 = 99.282%, U235 = 0.006%, U238 = 0.712%
-
DU234 = 0.006%, U235 = 99.282%, U238 = 0.712%
-
EU234 = 0.060%, U235 = 0.900%, U238 = 99.040%
Answer
Correct Answer: U234 = 0.006%, U235 = 0.712%, U238 = 99.282%
Explanation
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%