# High-temperature engineering test reactor

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Research reactor in Ōarai, Ibaraki, Japan

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The **high-temperature engineering test reactor** (**HTTR**) is a graphite-[moderated](/source/Neutron_moderator) gas-cooled [research reactor](/source/Research_reactor) in [Ōarai, Ibaraki](/source/%C5%8Carai%2C_Ibaraki), Japan operated by the [Japan Atomic Energy Agency](/source/Japan_Atomic_Energy_Agency). It uses long hexagonal fuel assemblies, unlike the competing [pebble bed reactor](/source/Pebble_bed_reactor) designs.

HTTR first reached its full design power of 30 MW (thermal) in 1999. Other tests have shown that the core can reach temperatures sufficient for [hydrogen production](/source/Hydrogen_production) via the [sulfur-iodine cycle](/source/Sulfur-iodine_cycle).[1]

## Technical details

The primary coolant is helium gas at a pressure of about 4 megapascals (580 psi), the inlet temperature of 395 °C (743 °F), and the outlet temperature of 850–950 °C (1,560–1,740 °F). The fuel is uranium oxide ([enriched](/source/Enriched_uranium) to an average of about 6%).

## See also

- [Very-high-temperature reactor](/source/Very-high-temperature_reactor)

- [Hydrogen economy](/source/Hydrogen_economy)

## References

1. **[^](#cite_ref-1)** Hanawa, Kazunari (4 April 2024). ["Japan eyes hydrogen production using next-gen nuclear reactor"](https://asia.nikkei.com/Business/Energy/Japan-eyes-hydrogen-production-using-next-gen-nuclear-reactor). *Nikkei Asia*. Retrieved 4 April 2024.

## External links

- [HTTR](https://www.jaea.go.jp/04/o-arai/nhc/en/faq/httr.html) at the [JAEA](/source/JAEA) website.

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