Abstract
Remote handling technology has been systematically developed for nuclear fuel cycle facilities in Japan since 1970s, primarily in parallel with the development of reprocessing and HLLW (High Level Liquid Waste) vitrification process. In case of reprocessing and vitrification process to handle highly radioactive and hazardous materials, the most of components are installed in the radiation shielded hot cells and operators are not allowed to enter the work area in the cells for operation and maintenance. Therefore, a completely remote handling system is adopted for the cells to reduce radiation doses of operators and increase the availability of the facility. The hot cells are generally designed considering the scale of components (laboratory, demonstration, or full-scale), the function of the systems (chemical process, material handling, dismantling, decontamination, or chemical analysis), and the environmental conditions (radiation dose rate, airborne concentration, surface contamination, or fume/mist/dust). Throughout our domestic development work for remote handling technology, the concept of the large scale integrated cell has been adopted rather than a number of small scale separated cells, for the reasons to reduce the total installation space and the number of remote handling equipment required for the each cell as much as possible. In our domestic remote maintenance design, several new concepts have been developed, tested, and demonstrated in the Tokai Virtrification Facility (TVF) and the Rokkasho HLLW Vitrification and Storage Facility (K-facility). Layout in the hot cells, the performance of remote handling equipment, and the structure of the in-cell components are important factors for remote maintenance design. In case of TVF (hot tests started in 1995), piping and vessels are prefabricated in the rack modules and installed in two lines on both sides of the cell. These modules are designed to be remotely replaced in the whole rack. Two overhead cranes and two bilateral servo-manipulators and ITV (Industrial Television) systems for monitoring are installed for Maintenance and also Operation in the cell. These cranes and manipulators are mounted on the bridge to ensure the wide range of operations in the cell and also designed to be remotely maintained themselves by each other. In case of K-facility (active tests stated in 2007) the operating experiences at TVF were reflected to make some improvements on its remote handling system in order to ensure the availability and reduce the cost. There adopted the unilateral servo-manipulator and the auxiliary hoist with remote operation support system, the rack module design for periodically replaced components, and the direct contact maintenance for the in cell cranes and manipulators in the shielded parking space. The glass melter in the vitrification process is designed to be replaced every 5 years, so the remote replacement and dismantling technology for the spent melters have been also developed and installed in TVF and K-facility for 40 years' operation. This paper describes our development experiences on the design, construction, operation, and maintenance of the remote handling systems in nuclear fuel cycle facilities in Japan.
