Prime Minister Narendra Modi witnessed a historic milestone today, marking the entry into the second stage of India's three-stage nuclear program. He observed the commencement of "Core Loading" at India's first indigenous Prototype Fast Breeder Reactor (PFBR) (500 MWe) at Kalpakkam, Tamil Nadu.
Fuel
Uranium oxide pellets are arranged in tubes to form fuel rods, which are used as basic fuel.
Moderator
Material in the core is used to slow down the neutrons released from fission so that they can cause more fission. This material is typically water, but it may also be heavy water or graphite.
Control rods or blades
Neutrons released from fission are slowed down in the core by material, which causes more fission. Common materials used for this purpose include water, heavy water, and graphite.
Coolant
A fluid circulates through the core to transfer heat. In light water reactors, the water moderator also functions as a primary coolant.
Pressurized water reactor (PWR)
The Pressurized Water Reactor (PWR) is the most widely used type of nuclear reactor, with around 300 operational reactors for power generation and several hundred more used for naval propulsion. The design of PWRs was initially developed for submarine power plants. PWRs use ordinary water as both coolant and moderator to control the nuclear reaction.
Boiling water reactor (BWR)
This type of reactor is similar to the PWR but has only one circuit with water at lower pressure (roughly 75 times atmospheric pressure). This results in water boiling in the core at around 285°C. The reactor is designed to function with 12-15% of the water in the top part of the core as steam, which reduces the moderating effect and efficiency in that area.
Pressurised heavy water reactor (PHWR)
The PHWR reactor, also known as CANDU, has been in development since the 1950s in Canada. Since the 1980s, it has also been developed in India. These reactors typically use natural uranium oxide fuel, which contains only 0.7% U-235. Therefore, a more efficient moderator, such as heavy water (D2O), is required