Graphite-moderated core, passively cooled with sodium filled heat pipes: https://antaresindustries.com/ https://antaresindustries.com/ It also uses a Brayton

Graphite-moderated core, passively cooled with sodium filled heat pipes: https://antaresindustries.com/ https://antaresindustries.com/ It also uses a Brayton cycle generator with nitrogen instead of steam. (See 03, 04, 06 in their schematic outline.)