The principle of controlled chain reaction is used in.

Options

A. atomic energy reactor
B. atom bomb
C. the core of sun
D. artificial readioactivity

Explanation

To solve the question regarding the principle of controlled chain reaction, we can break it down into the following steps:

### Step 1: Understanding Nuclear Fission
Nuclear fission is a process where a heavy nucleus splits into smaller nuclei, releasing a significant amount of energy. This process can occur spontaneously or can be induced by bombarding the nucleus with neutrons.

**Hint:** Recall that nuclear fission involves the splitting of heavy nuclei and is a source of large energy release.

### Step 2: Uncontrolled vs. Controlled Chain Reaction
In an uncontrolled chain reaction, the fission process occurs rapidly and releases an enormous amount of energy in a very short time, which can lead to catastrophic explosions (as seen in atomic bombs). In contrast, a controlled chain reaction is one where the rate of fission is managed to release energy steadily and safely.

**Hint:** Think about how control mechanisms are necessary to prevent rapid energy release in nuclear reactions.

### Step 3: Mechanism of Control
To achieve a controlled chain reaction, certain materials (neutron absorbers or moderators) are used to absorb excess neutrons. This absorption reduces the number of neutrons available to continue the fission process, thus controlling the rate of the reaction.

**Hint:** Consider what materials are typically used in reactors to manage neutron flow.

### Step 4: Application in Nuclear Reactors
The principle of controlled chain reaction is primarily utilized in nuclear reactors, where it is essential for generating power. In these reactors, the fission process is carefully controlled to produce a steady output of energy, which can be harnessed for electricity generation.

**Hint:** Remember that nuclear reactors are designed specifically to maintain a controlled environment for fission reactions.

### Conclusion
The principle of controlled chain reaction is used in **nuclear reactors** for power generation. This allows for the safe and efficient use of nuclear energy.

**Final Answer:** The principle of controlled chain reaction is used in **nuclear reactors**.