Write few uses of heavy water.

Explanation

**Step-by-Step Solution:**

1. **Definition of Heavy Water:**
- Heavy water is chemically represented as D2O, where D stands for deuterium, an isotope of hydrogen.

2. **Use as a Moderator in Nuclear Reactions:**
- Heavy water is primarily used as a moderator in nuclear reactors. Its role is to slow down the neutrons produced during nuclear fission, allowing for a sustained nuclear reaction. This is crucial for maintaining the chain reaction necessary for the reactor to operate efficiently.

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