State an advantage and a disadvantage of heavy-water reactors compared to light-water reactors.

Nuclear reactors are devices used to generate energy through controlled nuclear reactions. They come in different types, including heavy-water reactors (HWR) and light-water reactors (LWR). The main distinction lies in the type of moderator used:
• Heavy-water reactors use deuterium oxide (D2O) as a moderator.
• Light-water reactors use ordinary water (H2O) as a moderator.
Moderators are essential in nuclear reactors as they slow down neutrons, making them more likely to cause fission when they collide with uranium atoms. Both reactor types have their own set of advantages and disadvantages, impacting fuel requirements, efficiency, and cost.

Deuterium oxide, commonly referred to as heavy water, is chemically similar to ordinary water. However, it contains deuterium, a heavier isotope of hydrogen. In the context of nuclear reactors, heavy water is valued for its superior neutron moderation properties. This means it is more effective at slowing down neutrons, enhancing the likelihood of fission.
This efficiency allows heavy-water reactors to use unenriched uranium, which is less costly than enriched uranium. However, producing and maintaining heavy water is challenging. It requires specialized facilities and complex processes, adding to the operational costs of heavy-water reactors.

Unenriched uranium is natural uranium which has not undergone enrichment to increase the percentage of the isotope U-235. For light-water reactors, fuel typically needs to be enriched to increase its efficiency. This enrichment process is expensive and involves advanced technology.
Heavy-water reactors, however, can use unenriched uranium as fuel. This is a significant advantage since unenriched uranium is more plentiful and cheaper to acquire. By eliminating the need for enrichment, heavy-water reactors reduce the overall fuel cost. This makes them an appealing option despite the higher operational costs associated with deuterium oxide maintenance.

Operational costs are a crucial consideration in the design and choice of nuclear reactors. The costs include all expenses related to running and maintaining the reactor:
• Heavy-water reactors have higher operational costs due to the need to produce and maintain deuterium oxide.
• Specialized facilities and equipment are necessary to keep heavy water pure and effective.
In contrast, light-water reactors typically have lower operational costs because regular water (H2O) is easier and less expensive to handle. Yet, the lower operational costs of LWRs are offset by the higher fuel costs if they use enriched uranium.
Ultimately, the choice between heavy-water and light-water reactors involves balancing fuel costs against operational expenses, considering the specifics of the application and available resources.