This is all about the revival of pebble-bed reactors, which were attemped several decades ago but had problems with the graphite pebbles breaking down and releasing graphite fragments that clogged the pipes, basically. China is way ahead on this with helium-cooled versions. The big deal is that in the event of complete power loss (see Fukushima) they go into shutdown without melting down, although if the coolant lost and replaced with air you would get a nasty Chernobyl-style graphite fire. Still an improvement in safety. See:

> "Several high-temperature thermal neutron–spectrum pebble bed reactors are being commercialized. China has started up two helium-cooled pebble bed high-temperature reactors. In the United States, the X-Energy helium-cooled and the Kairos Power salt-cooled pebble bed high-temperature reactors will produce spent nuclear fuel (SNF) with burnups exceeding 150 000 MWd per tonne. The reactor fuel in each case consists of small spherical graphite pebbles (4 to 6 cm in diameter) containing thousands of small TRISO (microspheric tri-structural isotropic) fuel particles embedded in the fuel of zone these pebbles."

(2024) "Safeguards and Security for High-Burnup TRISO Pebble Bed Spent Fuel and Reactors"

https://www.tandfonline.com/doi/full/10.1080/00295450.2023.2...

and

https://www.powermag.com/nuclear-milestone-chinas-htr-pm-dem...