Pressurized heavy-water reactor facts for kids
A pressurized heavy-water reactor (often called a PHWR) is a special type of nuclear reactor. It was first developed in Canada. These reactors commonly use uranium as their fuel.
What makes PHWRs unique is that they use heavy water (which is a special kind of water called D2O) for two main jobs. First, it acts as a coolant, which means it takes away the heat created by the reactor. Second, it works as a neutron moderator. This means it helps slow down tiny particles called neutrons. Slowing neutrons helps the reactor work better.
The heavy water coolant is kept under high pressure. This allows it to get very hot without boiling. Even though heavy water is more expensive than regular water, it helps the reactor use its fuel very efficiently. This means PHWRs can often run without needing to "enrich" their fuel. Enriching fuel is a process that makes the uranium more powerful, but it's also very costly. Using heavy water helps save money on that step.
Contents
How a PHWR Works
A PHWR creates energy by splitting atoms in a process called nuclear fission. This process releases a lot of heat.
The Role of Heavy Water
Heavy water is special because it contains a heavier version of hydrogen called deuterium. This makes it very good at slowing down neutrons. When neutrons are slowed down, they are more likely to hit uranium atoms and cause them to split. This helps keep the nuclear reaction going steadily.
Cooling the Reactor
The heavy water also circulates through the reactor core. It absorbs the heat produced by the splitting atoms. Because it's under high pressure, it can get very hot without turning into steam. This hot heavy water then transfers its heat to another system, which creates steam. This steam then spins a turbine to generate electricity.
Advantages of PHWRs
PHWRs have some important benefits that make them useful for generating power.
Using Natural Uranium
One big advantage is that PHWRs can use natural uranium as fuel. Most other types of nuclear reactors need uranium that has been "enriched." This means the uranium has been processed to increase the amount of a specific type of uranium atom (Uranium-235). The enrichment process is complex and expensive. Because PHWRs don't need enriched fuel, countries can save money and don't need special enrichment factories.
Safety Features
PHWRs are designed with several safety features. The use of heavy water as both a coolant and moderator helps keep the reactor stable. They also have systems to shut down the reactor quickly if there's a problem.
Related pages
Images for kids
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This graph shows how likely Uranium-235 is to split when hit by neutrons. Slower neutrons (lower temperature) are generally better at causing fission.
See also
In Spanish: Reactor de agua pesada a presión para niños
