It is a type of nuclear reactor that uses: Heavy Water as both moderator and coolant; Natural uranium as the fuel.
It is a key component of India’s indigenous nuclear energy program due to its fuel flexibility and efficient neutron economy.
It is originally developed by Canada. India adopted and indigenised PHWR technology post-1974, after facing restrictions due to the nuclear test at Pokhran-I.
India developed indigenous PHWRs of 220 MWe, 540 MWe, and 700 MWe.
Fission of U-235 in fuel rods produces heat, heavy water moderates neutrons and also cools the reactor core, heated coolant transfers thermal energy to a steam generator.
Advantages:
1.Uses natural uranium-avoids costly enrichment
2.High neutron economy
3.Easier online refueling
4.Indigenous technology
5.Suitable for Thorium-based fuel cycle transition
Challenges:
1.Heavy water is expensive and must be carefully conserved
2.Tritium management is necessary due to its production in heavy water
3.Complexity in design and safety systems
4.Higher initial capital cost.
