https://atomicinsights.com/chinas-high-temperature-reactor-p... has a summary of the past experimental reactors (skip half way down to the heading “Brief high temperature reactor history”), and explains some of the reasons past reactors have failed to be commercialised.
It also explains one central problem with using gas: “Even with higher temperatures and higher efficiency, each core can produce 1/10th of the electricity of light water reactors, but [China’s] HTR pressure vessel is described as ‘the world’s largest and heaviest pressure vessel.’ Pressurized gas has a far lower capacity to move heat than pressurized water.”.
Well yeah, they did not displace PWRs (the heat capacity issue is one of the reasons why molten salt and sodium fast reactors were investigated). But the problem is not the lack of high temperature materials (which is false).
https://atomicinsights.com/chinas-high-temperature-reactor-p... has a summary of the past experimental reactors (skip half way down to the heading “Brief high temperature reactor history”), and explains some of the reasons past reactors have failed to be commercialised.
It also explains one central problem with using gas: “Even with higher temperatures and higher efficiency, each core can produce 1/10th of the electricity of light water reactors, but [China’s] HTR pressure vessel is described as ‘the world’s largest and heaviest pressure vessel.’ Pressurized gas has a far lower capacity to move heat than pressurized water.”.
https://duckduckgo.com/?q=high-temperature+gas+reactor