Prototype Fast Breeder Reactor (PFBR)
Context:
- Recently Prime Minister Narendra Modi witnessed the start of the process of core-loading the indigenous Prototype Fast Breeder Reactor (PFBR) at the Madras Atomic Power Station in Kalpakkam which is in Tamil Nadu.
What is the PFBR?
- The Prototype Fast Breeder Reactor is a machine that produces more nuclear fuel than it consumes.
- Its core-loading event is being hailed as a “milestone” due to the fact that operationalisation of the PFBR will mark the start of stage II of India’s three-stage nuclear power programme.
India’s three-stage nuclear power programme:
- India’s three-stage nuclear power programme was formulated by Homi Bhabha in the 1950s.
- The aim of this program is to utilize the country’s uranium and thorium reserves to their maximum extent to produce nuclear power.
- In the first stage, natural uranium fuelled Pressurised Heavy Water Reactors (PHWRs) produce electricity while generating plutonium-239 as byproduct.
- PHWRs are chosen for the first stage because they can be refueled while operating at full power, which helps in maximizing the reactor’s capacity factor.
- However, the amount of power that can be generated in this stage is limited by India’s modest reserves of uranium.
- The second stage involves the use of Fast Breeder Reactors (FBRs).
- These reactors use a mixed oxide fuel made from plutonium-239, obtained from the first stage, and natural uranium.
- In these reactors, the uranium-238 present in the mixed oxide fuel transmutes to additional plutonium-239.
- Thus, the FBRs not only generate power but also produce more fuel than they consume, hence the name ‘breeder’.
- The design of these reactors also allows for a significant increase in the utilization of the country’s uranium reserves.
- The third and final stage is based on Thorium-232 to uranium-233 fuel cycle.
- The abundant thorium available in India is converted to uranium-233 in Reactors.
- Uranium-233 is a fissile material which can be used to produce electricity in Thermal Reactors.
- This stage is crucial for long term sustainability of nuclear power in India.
How does the PFBR work?
- PHWRs will use natural or low-enriched U-238 as the fissile material and produce Pu-239 as a byproduct.
- This Pu-239 is combined with more U-238 into a mixed oxide and then this mixture is loaded into the core of a new reactor together with a breeder blanket.
- This is the material the fission products in the core react with to produce more Pu-239.
- A breeder reactor is a nuclear reactor which produces more fissile material than it consumes.
- In a ‘fast’ breeder reactor, the neutrons aren’t slowed which allows them to trigger specific fission reactions.
- The PFBR is designed to produce more Pu-239 than it consumes.
- It uses liquid sodium which is a highly reactive substance, as coolant in two circuits.
- Coolant in the first circuit enters the reactor and then leaves with heat) energy and radioactivity.
- Through heat-exchangers, it transfers only the heat to the coolant in a secondary circuit.
- The latter transfers the heat to generators to generate the electricity.
