Zetta Joule
Houston, US · Founded 2023 · 39 employees on LinkedIn · 1 known investors
ZettaJoule develops advanced small modular reactors based on modernized high-temperature gas-cooled reactor (HTGR) technology, drawing on operating data from Japan's HTTR. Its helium-cooled, graphite-moderated ZJ reactor is designed to generate high-temperature heat up to 950 °C and electricity for industrial and commercial sectors such as oil and gas, chemical manufacturing, mining, steelmaking, and data centers.
Also known as ZettaJoule · ZettaJoule KK
Founders & leadership
Zetta Joule was founded in 2023 by Mitsuo Shimofuji, Jeffrey Harper, Kazuhiko Kunitomi, and Rumina Velshi.
Investors · 1
Company profile
researched Aug 2026ZettaJoule is an advanced nuclear energy company developing a small modular reactor (SMR) based on high-temperature gas-cooled reactor (HTGR) technology. Its ZJ reactor is designed with a thermal generating capacity of 30 MWth and heat output of up to approximately 950 °C, which the company describes as roughly 600 °C higher than conventional water-cooled reactors. The company positions itself as modernizing the established, publicly available technology of Japan's High Temperature Engineering Test Reactor.
The design targets four output categories: high-temperature process heat, combined heat and power, hydrogen production, and around-the-clock electricity. Named end markets include oil and gas, chemicals (ammonia, polymers and e-fuels), steelmaking, mining and refining of rare earths, lithium and critical minerals, transportation and sustainable aviation fuel, data centers, district heating, microgrids, residential and commercial users, community energy systems, and desalination. Planned facilities are described as energy campuses with architectural treatment intended to integrate with surrounding environments.
The company also operates a workforce subsidiary, the ZettaJoule Reactor Operating Company (ZROC), intended to recruit students and trainees at local, regional and national levels for roles as nuclear engineers, plant operators and technicians.
Founding story
ZettaJoule's name refers to U.S. Department of Energy projections that annual global energy demand will reach one zettajoule — 10²¹ joules — by 2050, which the company cites as the need its clean heat and power technology is intended to address.
Business model
ZettaJoule intends to sell energy rather than reactors, offering a 24/7 clean-energy-as-a-service model in which it owns, operates and staffs the nuclear facilities while customers may participate solely as off-takers. The company states this arrangement provides customers with financing and operational benefits and removes the burden of managing a nuclear plant.
Energy-as-a-service: the company owns, operates and staffs the facility and customers can take output under off-take arrangements rather than owning nuclear assets.
▸Full profile — market position, technology, go-to-market, geography
Market position
The company describes itself as the only Western advanced SMR developer modernizing the publicly available technology of Japan's High Temperature Engineering Test Reactor, and emphasizes heat output well above that of conventional water-cooled reactors.
Differentiation claims center on high-temperature output up to 950 °C enabling applications inaccessible to water-cooled reactors, use of an existing operating test-reactor technology base rather than an unproven design, AI-based digital twins for operations, an energy-as-a-service commercial structure, and an in-house workforce pipeline through ZROC.
Technology
The ZJ reactor is a high-temperature gas-cooled reactor (HTGR) design rated at 30 MWth and designed to operate at temperatures up to 950 °C, covering and exceeding the 300–850 °C range the company associates with chemical operations. The design derives from Japan's High Temperature Engineering Test Reactor. The company states its modernized design uses artificial intelligence and AI-based digital twins to streamline operations, reduce costs, accelerate delivery and limit human error.
Go-to-market
Direct engagement with industrial off-takers through the company's sales contact channels, supported by sector-specific solution offerings for oil and gas, chemicals, transportation, steelmaking, mining, data centers, communities and desalination, and by an owner-operator service model that removes nuclear operating responsibility from the customer.
Industrial and infrastructure energy users, including oil and gas operators, chemical manufacturers, steelmakers, mining and refining operations, aviation and shipping fuel producers, data center operators, municipalities and district heating systems, microgrid and residential/commercial users, and desalination projects.
Geography
The company describes an international team and operates a Japanese entity, ZettaJoule KK, alongside its ZROC subsidiary.
Compiled by commissioned research from 2 cited public sources — announcements, filings, and press listed under research sources below.
Key figures
latest reportedCompany-reported or press-reported figures, each dated to when it was claimed — not independently audited.
▸Research sources · 2
primary sources listed
- Zetta Joulezetta-joule.com · web
2 public sources were cited for this profile; the first-party ones are listed here.
Frequently asked questions
- What does Zetta Joule do?
- ZettaJoule is developing high-temperature gas-cooled small modular reactors delivering process heat and power up to 950 °C.
- Who founded Zetta Joule?
- Zetta Joule was founded by Mitsuo Shimofuji, Jeffrey Harper, Kazuhiko Kunitomi, Rumina Velshi in 2023.
- Who are Zetta Joule's investors?
- Zetta Joule's investors include Globis Capital Partners.
- Where is Zetta Joule headquartered?
- Zetta Joule is headquartered in Houston, US.