Which of the following process will result into fission reaction ?

Options

A. `""_(92)U^(235)` is bombarded with fast moving neutrons
B. `""_(92)U^(235)` is bombared with thermal neutrons
C. `U^(238)` is bombarded with slow moving neutrons
D. `U^(235)` being unstable breaks into smaller fragments

Answer

To determine which process will result in a fission reaction, we need to analyze the interactions of Uranium-235 (U-235) and Uranium-238 (U-238) with neutrons.

### Step-by-Step Solution:

1. **Understanding Fission**: Fission is a nuclear reaction in which the nucleus of an atom splits into two or more smaller nuclei, along with the release of energy and neutrons. For fission to occur, the nucleus must absorb a neutron and become unstable.

2. **Uranium Isotopes**:
- U-235 is a fissile isotope, meaning it can sustain a fission chain reaction when it absorbs a neutron.
- U-238 is not fissile but can undergo fission under certain conditions, typically when bombarded with fast neutrons.

3. **Neutron Bombardment**:
- When U-235 is bombarded with **fast-moving neutrons**, it can absorb the neutron and form U-236, which is unstable and can undergo fission. However, fast neutrons are less likely to cause fission in U-235 compared to thermal neutrons.
- When U-235 is bombarded with **thermal (slow-moving) neutrons**, it is more likely to absorb the neutron and become U-236, leading to fission. This is because thermal neutrons have a higher probability of being captured by the nucleus.

4. **U-238 Interaction**:
- U-238 can also undergo fission when bombarded with fast neutrons, but it is not as efficient as U-235 with thermal neutrons. U-238 can capture a thermal neutron to become U-239, which is not a fission reaction but can lead to the production of plutonium-239, which is fissile.

5. **Conclusion**: The process that results in a fission reaction is when U-235 is bombarded with thermal neutrons. This leads to the formation of U-236, which is unstable and undergoes fission.

### Final Answer:
The process that will result in a fission reaction is when U-235 is bombarded with thermal neutrons.