High-temperature engineering test reactor
The high-temperature engineering test reactor is a graphite-moderated gas-cooled research reactor in Ōarai, Ibaraki, Japan operated by the Japan Atomic Energy Agency. It uses long hexagonal fuel assemblies, unlike the competing pebble bed reactor designs.
HTTR first reached its full design power of 30 MW in 1999. Other tests have shown that the core can reach temperatures sufficient for hydrogen production via the sulfur-iodine cycle.