What role does near-pure water play in nuclear power plants in the United States?

Near-pure water plays a crucial role in nuclear power plants, primarily acting as a moderator in the nuclear fission process. In this context, its function is to slow down fast-moving neutrons produced during fission reactions. When these neutrons are slowed down, they are more likely to interact with fuel nuclei (such as uranium-235), leading to a greater likelihood of further fission reactions. This process enhances the efficiency of the nuclear reaction, allowing the plant to generate a sustained power output.

As water absorbs some heat during this process, it transitions into steam, which is used to drive turbines connected to generators, thereby producing electricity. The ability of the water to act both as a moderator and a coolant is crucial for maintaining optimal operating conditions within the reactor, ensuring safety and moderating the rate of fission.

In summary, near-pure water is essential in the nuclear power generation process, effectively moderating neutrons and facilitating a controlled fission reaction while also serving to transfer heat away from the reactor core.