Identify the correct sequence of concentration in increasing order of the following uranium isotopes in naturally occurring uranium: (A) U-233 (B) U-234 (C) U-235 (D) U-238
Choose the correct answer from the options given below:

Correct option is A

In naturally occurring uranium, the abundances of isotopes are as follows:
· U-238: ≈ 99.2745% — the most abundant
· U-235: ≈ 0.72%
· U-234: ≈ 0.0055%
· U-233: Not naturally occurring in any significant amount; it's a synthetic isotope produced in reactors
Thus, in increasing order of concentration:
U-233 < U-234 < U-235 < U-238
Additional Information:
· U-233 is used in thorium fuel cycles but is not found in natural uranium.
· U-234 is present due to the decay chain of U-238.
· U-235 is fissile and used in nuclear reactors and weapons.
· U-238 is fertile and can be converted into Pu-239 in reactors.