Nuclear power reactors produce energy by initiating and controlling a sustained nuclear chain reaction. Currently, there are 400 such reactors in 32 countries provide about 10 per cent of the world’s electricity. 1. [[Water Cooled Reactors]] 2. [[Gas Cooled Reactors]] 3. [[Fast Reactors]] 4. [[Molten Salt Reactors]] 5. [[Small Modular Reactors]]