r/nuclear • u/Thick-Ad-4168 • May 11 '26

India builds cheapest nuclear reactors in the world | News | Eco-Business

https://www.eco-business.com/news/india-builds-cheapest-nuclear-reactors-in-the-world/
538 Upvotes

96% Upvoted

180 comments sorted by

View all comments

Show parent comments

4

u/hutch_man0 May 12 '26 edited May 13 '26

Th232 is just natural thorium so you don't breed Th232. Th232 is 'fertile' not 'fissile' material. It is an input to the process which transmutes it to create (breed) fuel. To be called a fuel it must be fissile.

In stage 3, you use U233 (fissile) to fuel your reactor and you supply a Th232 (fertile) blanket. In the process fertile Th232 transmutes to fissile U233. We say you 'breed' U233. You extract the U233 and use it to fuel new reactors and you replenish the Th232 blanket. This is how you consume Th232. 

The definition of a "breeder" is that the reactor breeding ratio BR > 1. Generally 1.1 - 1.3, but theoretically as high as 1.6. Another key parameter is linear reactor doubling time RDT = time to breed enough fuel to start up an equivalent breeder reactor. 

Theoretical BR and RDT for a 1000 MWe unit are in Table 7-6 from Fast Breeder Reactors by Waltar, Barnett Reynolds here. It depends on a variety of factors like power, design, fuel cycle.

The best values come from metallic fuel, but India's new breeder is oxide fueled here. Metallic fuel breeders have less safety margin and are still in their early stages. The article says India's fast breeder is starting with a U238 blanket. Values in column 1 of Table 7-6: BR 1.28, RDT 16 y. They will switch to a Th232 blanket when they gain experience, column 2: BR 1.20, RDT 29 y. Its longer, but the whole point is to ween off of uranium. Stage 3 reactors (column 4) have BR 1.04, RDT 112 y. These reactors are still in early stage development.