Question

which of the following isotopes normally fissionable (A) \({ }_{92} \mathrm{U}^{233}\) (B) \({ }_{92} \mathrm{U}^{238}\) (C) \({ }_{92} \mathrm{U}^{235}\) (D) \({ }_{93} \mathrm{~Np}^{239}\)

Short answer

The normally fissionable isotope among the given options is (C) \({ }_{92} \mathrm{U}^{235}\).

Step-by-step solution

Option A: \({ }_{92} \mathrm{U}^{233}\)

The isotope \({ }_{92} \mathrm{U}^{233}\) is fissile, which means it can sustain a chain reaction when bombarded with thermal neutrons. Therefore, \({ }_{92} \mathrm{U}^{233}\) can be considered as a fissionable isotope.

Option B: \({ }_{92} \mathrm{U}^{238}\)

The isotope \({ }_{92} \mathrm{U}^{238}\) is fertile, meaning it can be converted into a fissile isotope (\({ }_{92} \mathrm{U}^{239}\)) when it captures a neutron. However, it doesn't usually undergo fission when bombarded with thermal neutrons. So, \({ }_{92} \mathrm{U}^{238}\) is not considered as normally fissionable.

Option C: \({ }_{92} \mathrm{U}^{235}\)

The isotope \({ }_{92} \mathrm{U}^{235}\) is fissile and can sustain a chain reaction when bombarded with thermal neutrons. Therefore, \({ }_{92} \mathrm{U}^{235}\) is considered as a normally fissionable isotope.

Option D: \({ }_{93} \mathrm{~Np}^{239}\)

The isotope \({ }_{93} \mathrm{~Np}^{239}\) is a transuranic element that can undergo fission when bombarded with fast neutrons, but not thermal neutrons. Therefore, it is not normally considered as fissionable.

Final Answer

Based on the given options, the normally fissionable isotope is: (C) \({ }_{92} \mathrm{U}^{235}\)