Japan plans hydrogen production with next-generation nuclear reactor — using heat and only minimal electricity

The HTGR is a type of low-efficiency but ultra-safe nuclear reactor developed by JAEA, in which the core will not melt down even if control rods (made of materials that slow the nuclear reaction) are not deployed or if the gas-cooling system fails — a huge factor in a country that witnessed the devastation caused by the Fukushima nuclear disaster in 2011.

But the HTGR reaches temperatures of 870°C, yielding a lot of waste heat that JAEA believes can be used to make hydrogen, and which it has been studying since 2010.

The process uses waste heat in a thermochemical reaction called the sulphur-iodine cycle, in which hydrogen and oxygen are extracted from water as part of a three-step chemical process.

First sulphur dioxide and iodine are added to water in a process known as the Bunsen reaction, which produces a layered liquid containing sulphuric acid and hydrogen iodide.

These two compounds are separated, either by distillation or by gravity, and the hydrogen iodide is then heated to 500°C to produce hydrogen and iodine.

JAEA’s method also envisages further concentration of the hydrogen iodide solution by putting it through an “electro-electrodialysis” system, in which positively charged hydrogen molecules are separated from negatively charged iodine molecules via a cation exchange membrane.

The sulphuric acid is, separately, heated to 900°C to create oxygen, sulphur dioxide and water, which is usually further separated by condensation. All the base chemicals are then recycled into the process.

The JAEA has been researching the potential for producing so-called “pink” hydrogen using waste heat from the HTGR since 2010, and wants to set up a demonstration plant by the end of this decade.

“We plan to proceed with safety evaluations, including compliance with regulations, and to demonstrate hydrogen production using the HTTR’s [High Temperature Engineering Test Reactor, of which the HTGR is part] nuclear heat by 2030,” the JAEA said.

“JAEA’s final target is the successful demonstration of the coupling of a nuclear reactor and heat application system by connecting a hydrogen production plant to Japan’s first HTGR, that is, the HTTR,” JAEA said.

The government is purportedly planning to take the lead on the HTGR nuclear-to-hydrogen project, until the technology is ready for wider commercial use — however there are currently no figures available for how much of JAEA’s ¥21bn ($138m) decarbonisation and innovation budget was allocated to this project.