In a nuclear reactor, what is the function of:
The coolant

Explanation

### Step-by-Step Solution:

1. **Understanding the Nuclear Reactor**: A nuclear reactor is a device used to initiate and control a sustained nuclear chain reaction. It generates heat through nuclear fission, where heavy atomic nuclei split into smaller parts.

2. **Heat Generation**: During the fission process, a significant amount of heat is produced. This heat is essential for generating steam, which can then be used to drive turbines for electricity generation.

3. **Role of the Coolant**: The primary function of the coolant in a nuclear reactor is to remove the excess heat generated during the fission process. If this heat is not effectively removed, it can lead to overheating and potential damage to the reactor core.

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