Penultimate Power has teamed up with the Japanese Atomic Energy Agency (JAEA) with the goal of building a high-temperature gas-cooled reactor in the UK by 2029.

The announcement comes after the UK's Department for Business, Energy and Industrial Strategy (BEIS) opened the Generic Design Assessment (GDA) to advanced nuclear technologies in May 2021.

The GDA is the onerous process to license a technology in the UK, run by the Office for Nuclear Regulation and the Environment Agency. The regulators have introduced "new flexibilities" to the GDA process to ensure the UK’s readiness for advanced nuclear technologies, with the modernised GDA having three steps rather than four.

Penultimate Power UK said it is aiming to be the first to register with the new licensing regime with the EH HTGR, a helium-cooled reactor that uses TRISO fuel.

Subject to government approval the aim is to “have the first operating by 2029 and 20 units a year from early 2030s,” it added.

“This is Generation IV technology, moving on from pressurised water reactors (PWRs). The EH HTGR is inherently safe at far less cost. It uniquely provides carbon-free heat up to 950C for industrial processes, including green hydrogen at point of use,” said Candida Whitmill, managing director Penultimate Power UK.

“Following the recent trade deal with Japan we are delighted to be working with such a trusted international partner. JAEA are acknowledged global experts on HTGR technology. JAEA has proved HTGR safety, capabilities and financial viability over ten years of operation,” she added.

Penultimate Power UK claims that the first EH HTGR unit will cost in the region of £100m, with reductions for future units. Unlike water-cooled pressurised water reactors, the unit is not restricted to coastal locations, and is expected to operate at 45% efficiency (vs. 32-34% for a PWR) and produce 75% less waste. Units are expected to last 60 years.

“Units will be built in a factory based on Teesside, bringing long-term quality jobs to the North East and across the Northern Powerhouse region,” said Alastair Balls, Penultimate’s lead on Economics and Commercial Development.

The UKSMR consortium announced last month ( that it is aiming to have the first design to be assessed by regulators in the second half of 2021, which will keep it on track to complete its first unit in the early 2030s.