All remaining highly enriched uranium from the Japan Atomic Energy Agency's Japan Materials Testing Reactor Critical Assembly has now been returned to the USA. Japan and the USA have been cooperating for many years to repatriate HEU from Japanese research reactors to the USA.
Japan's last high-enriched uranium-fuelled research reactor is to be converted to low-enriched uranium fuel under a new agreement between the US Department of Energy National Nuclear Security Administration and Japan’s Ministry of Education, Culture, Sports, Science and Technology.