...thorium/uranium fuels represent a path forward to addressing the issues of depleted uranium valorization to generate the plutonium we will need to slow extreme global heating.

India has a fleet of heavy water reactors (of the CANDU type, of which they are knockoffs) and thus is well situated to exploit this option. The ²³³U that will be generated can be exported and mixed down with depleted uranium and eliminate the expensive and somewhat problematic enrichment systems.

The fast neutron cycle is, of course, a key to succeeding.

All this said, the Kalpakkam reactor is a straight up sodium cooled reactor; these reactors have been a mixed bag, with the scaled up Monju in Japan and the Superphenix in France having not succeeded commercially or in service. The BN-600 in Russia and the EBRII in the US did better. (The Oklo SMR is built around the EBRII technology.)

In discussions with my son I understand a problem that I hope has been considered with Kalpakkam; specifically materials science issues. One of the things that generates a lot of complaints by my son's Ph.D. advisor is that innovative materials are not considered in nominally "new" reactor types, and that people tend to do things the way they've always been done, because they've always been done that way. This is a very bad reason to do something, because it's always been done that way, particularly in light of systems that did not live up to expectations.

Personally, I feel that we need to move beyond sodium as a fast reactor coolant. Before I die, I want to be sure to leave ideas about better options in my son's head. There are many better options I think.

All too prevalent, in so many spheres of human activity.

I remember once reading an ostensible aphorism of "tradition is a set of answers to which we have forgotten the questions", and my immediate reaction was, "do we know the questions are still relevant ?". I believe the context was traditional marriage and family customs, and probably being used to justify something like brideprices for virgins.

Sad to think that in a field built on so many scientifically determined principles, the path of least thought would still be in play.

One has to navigate a number of issues in dealing with complex technology; one of those is the supply chain. It's probably cheaper and easier to do things the old way; more difficult to be innovative, since efforts at innovation can be costly simply because not everything works the first time.

There are some innovative approaches in the new era of nuclear creativity. For example, although I'm not really a FLIBE (BeF₂/LiF eutectic) kind of guy, Kairos has made an effort to bring this new supply chain issue forward for its high temperature reactors. For FLIBE it is probably still true that the optimal structural material is probably that developed in the 1960's, the nickel alloys Inconels and/or Hastelloys. (I say that without being, as my son is, a materials scientist.)

In my own thinking, I have tended not to pay much attention to sodium cooled fast breeders in any other than a general sense. I'm more of a "breed and burn" kind of guy, which work rather like a candle, as Sekimoto put it, although I would modify the concept by employing liquid metal fuels, low melting plutonium alloys, of which there are many of note. This would require, I admit, quite a bit of research, almost certainly costly research.