Status on the development of the fabrication and analysis equipment of the pseudo fuel debris

In the Fukushima Daiichi Nuclear Power Station (1F) decommissioning, the fuel debris needs to be treated with great care from the standpoint of criticality safety, due to the uncertainty of its chemical composition and physical state. Japan Atomic Energy Agency (JAEA) has been planning to perform critical experiments at the new STACY, which is a heterogeneous thermal neutron system consisting of fuel rods and light water moderator. In the criticality experiment at the new STACY, pseudo fuel debris samples are used to acquire data for validation of the system used for 1F debris criticality safety assessment. The pseudo fuel debris will be prepared and analyzed at the Back-end Fuel Cycle Key Elements Research Facility (BECKY) adjacent to the new STACY to realize flexible and rapid experiment preparation and analytical evaluation. The pseudo fuel debris preparation equipment and analytical equipment are installed at BECKY to evaluate the critical properties of fuel debris with high accuracy in dimension and chemical composition. The pseudo fuel debris is a pellet with a diameter of 8 mm and a height of 10 mm containing uranium oxide and structural materials (iron, silicon, zirconium, etc.). The pellets are made by mixing, pressing and sintering uranium dioxide powder and structural materials powder. This article briefly introduces the preparation and analytical equipment at BECKY, and the pseudo fuel debris pellets prepared using these equipment. (author)