The United States has received 1.7 metric tons of high-assay low-enriched uranium (HALEU) from Japan in what officials described as the largest single international uranium shipment in the history of the National Nuclear Security Administration (NNSA).

The transfer was carried out through a partnership between the U.S. Department of Energy’s NNSA, Japan’s Ministry of Education, Culture, Sports, Science and Technology, and the Japan Atomic Energy Agency. The material originated from Japan’s Fast Critical Assembly program, which has been shut down.

HALEU is considered a key fuel source for next-generation nuclear reactors. Unlike conventional reactor fuel, it contains a higher concentration of uranium-235, allowing advanced reactors to operate more efficiently, for longer periods, and with smaller reactor designs.

The shipment arrives as the United States pushes to establish a domestic HALEU supply chain to support emerging advanced nuclear technologies. The material will now be processed under the Department of Energy’s HALEU Availability Program to help bridge fuel supply gaps for future reactor developers.

Fueling advanced reactor push

“NNSA is breaking records with rapid approvals and decision making to support America’s nuclear industry,” said NNSA Administrator Brandon Williams. “Supplying advanced reactor designs with HALEU fuel is vital to making America energy dominant in pursuit of President Trump’s vision to strengthen our nuclear industrial base.”

The agency said the shipment also supports broader nuclear nonproliferation goals. HALEU is seen as a lower-risk alternative to highly enriched uranium and plutonium, which have historically raised weapons proliferation concerns.

Officials noted that the transferred uranium was no longer needed in Japan after the closure of its Fast Critical Assembly program. Instead of remaining unused, the material will now support the growing demand for advanced nuclear fuels in the United States.

Advanced reactors under development in the U.S. are expected to rely heavily on HALEU fuel because of its ability to improve reactor efficiency while reducing reactor size and extending operating cycles.

Japan-US nuclear partnership

“This milestone accelerates our progress towards a secure and independent energy future, while reaffirming our commitment to nuclear nonproliferation,” said Dr. Matthew Napoli, NNSA’s Deputy Administrator for Defense Nuclear Nonproliferation. “Through this partnership with Japan, we are fueling the next generation of nuclear power, and solidifying America’s energy dominance.”

The project was completed with support from the UK’s Nuclear Transport Solutions and Civil Nuclear Constabulary, which assisted in the transport and security operations linked to the uranium transfer.

The shipment also aligns with recent U.S. efforts to accelerate advanced nuclear reactor deployment and reduce reliance on foreign nuclear fuel supplies. Earlier policy initiatives have emphasized building a domestic nuclear fuel ecosystem capable of supporting commercial and national security reactor programs.

HALEU has become increasingly important as multiple U.S. companies race to commercialize small modular reactors and other advanced nuclear systems designed for power generation, industrial applications, and defense-related energy needs.

The announcement comes amid growing global interest in nuclear energy as countries seek stable, low-carbon power sources capable of supporting expanding electricity demand from artificial intelligence infrastructure, manufacturing, and electrification.