I personally believe that is the last best hope of humanity, and I often state, that opposing nuclear energy is borderline insane and almost certainly immoral to the point of criminal.
If you know anything about me, you should know that.
The current fleet of nuclear reactors represents a great engineering, scientific, environmental and human success, but this infrastructure is largely based on technology that was developed in the 1950's and 1960's.
Like many other high tech devices, aircraft come to mind, nuclear energy is not risk free and there have been expensive and (in the case of Chernobyl) deadly failures, but like aircraft - which are the safest traveling devices in terms of deaths/100,000 km - nuclear energy is vastly superior to everything else, not perfect, but just infinitely better, which should be enough, but somehow isn't.
To answer your question:
High temperature reactors were studied extensively in the 1950's and 1960's and some were tested. It can be said that materials science at that time was relatively primitive compared to what we know now. As I remarked elsewhere, the British had moderately successful high temperature reactors, but largely they were electricity generating machines.
One of the most important tools for understanding materials was the development of the Kohn Sham equations, which were developed in the 1950's and 1960's well before the computer power existed to utilize them. The overwhelming majority of the functioning nuclear reactors in the world were designed before that computer power existed to use this theorem/equation. This work was developed by Nobel Laureate and Holocaust Survivor Walter Kohn. KS - and more advanced refinements - are now routinely used to address many questions in materials science and, for that matter, biological and chemical science.
There have been many more recent developments in both the theory, DFT and OFDFT, and practice of materials science since Kohn began publishing his work. Were it not for public stupidity, I'm sure we could develop outstanding reactors, but as of this decade, we are facing a period in which ignorance is triumphant, hopefully a brief reactionary interlude, but one never knows.
I have not kept up to date on the latest developments in high temperature reactors per se, although I have been very interested in refractory materials. Last I looked, the Chinese were exploring high temperature reactors and coupling them to the somewhat less than ideal (from my perspective) sulfur iodine hydrogen cycle. I believe they have a 10 MW high temperature gas cooled reactor operating, I'm not sure. People are always publishing sulfur iodine papers and modifications, and perhaps, because of a quirk originating with General Atomics
My son will be researching very high temperature refractories this summer in Europe, totally by coincidence, as a result of his academic success. I had nothing at all to do with it by the way. Nevertheless I'm really intrigued by this work, which involves both chemical structure and nanostructure applications, and I hope he'll be able to teach me something when he returns.
I've been daydreaming quite a bit myself about very high temperature reactors using liquid plutonium (and various eutectics) as a fuel, based on some preliminary work carried out in the late 1950's and early 1960's. I've spent quite a bit of time collecting and reading literature on this concept, which I believe deserves another serious look. I believe these types of reactors, in a "breed and burn" setting can definitely be structured to produce continuous hydrogen/carbon oxide cycles. If what I imagine is realistic, these would be remarkable machines, built and structured with what some people, not me, regard as "waste."
As my son's scientific abilities grow, I'm trying to drop these concepts into his mind, wherever he has time or interest. I will certainly not live to see anything like this, and no matter how much I've learned, in now way do I have the prestige or resources to see this thing through, but I'm impressed by my son's mind, and proud father that I am, I can hope he may have both the resources and prestige.
I'm hoping, beyond my son, for a generation less stupid than mine. Some of the kids I've met have been very impressive, very impressive.
That's all I've got. I've got hope.
What we're doing now is so wrong as to boggle the mind.
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