Development of innovative system and technology on MOX fuel production for FBR

Japan Atomic Energy Agency (JAEA) has been engaging the development of MOX fuel to be burned in the FBR in order to efficiently use the limited amount of natural resources. The fundamental technology needed to this near reaching purpose was accomplished through previous two projects, so called Phase 2, and FaCT. Urgently needed subject is its scaling up from experimental scale to industry scale and giving a guarantee on economical profit on the MOX fuel production. It is eagerly required to surely accomplish this requirement until 2015. In this paper, the system of MOX fuel production based on a microwave heating (MH), simplification of traditional processes piled up through many years' experiments, and update approach for upgrading of simplification of our production system are described. Future plan for promoting this strategy is also introduced. 1. Existing system of pellet fabrication. The entire system of MOX pellet fabrication is demonstrated; (a) is the current system, (b) an innovative apparatus newly considered, being a forceful candidate for simplifying the system, (c) sectional side view of press for pressing MOX particles into a die, and (d) hollow type MOX pellet obtained through the press and sintering. In case of current system, Pu/U mixed nitrate solution and Uranium nitrate solution are individually de-nitrated by MH, resulting in MOX powder and UO2 powder. The adjustment of final ratio of PuO2/UO2 is carried out by mixing MOX powder and UO2 powder so as to satisfy the requested value offered from pellet specifications. After that the powder is pressed into a die, sintered, being fabricated a pellet. In these processes, diffusion of MOX dust is the biggest problem which occurs in the route of powder transfer. In addition, the number of process is so many, complicated, and blocking the reduction of production cost. Thus, the prevention of powder diffusion, rationalization of production processes, improvement of economic efficiency, and so on are the subject of present urgency. 2. Rationalization of system and future target. A unique apparatus combining three processing (de-nitration, crushing and granulation) within one globe box (GB) by employing only one tray for common use is shown. Considerable stages can be reduced by means of this new apparatus. We are now attacking the subject to scale up of this new method so as to satisfy the high speed, mass production of MOX powder and particles. 3. Elucidation of de-nitration mechanism. According to our experiments, if a high power microwave is applied to the Uranium nitrate solution to advance the high speed de-nitration, spouting occurred. Due to the spouting, Uranium nitrate solution overflowed from the tray. In order to prevent the overflow, fundamental research on the mechanism of spouting which is generated by the microwave heating (MH) is ongoing by employing water. Up to present, the specific effect of the microwave on liquid heating has been clarified. 4. Introduction of computer simulation technology. The computer simulation on the electromagnetic distribution inside a high power microwave oven is advancing from the point of view to improve the heating efficiency. The computer simulation on behavior of particles which was developed in the ceramics industry is applied to our MOX powder field to improve the yield constant by optimization of production conditions. In this paper, we will totally report our update results and conclusions