抄録
As part of the LONG Term OPerationS (LongOps) research and development program, Remote Applications in Challenging Environment (RACE), Sellafield Ltd and Tokyo Electric Power Company Holdings (TEPCO) have joined forces to develop the Next Generation Digital Mock-up (NG-DMU) for nuclear decommissioning and remote handling applications. TEPCO plans to conduct Fuel Debris Retrieval (FDR) in Fukushima Daiichi Nuclear Power Station Unit 3 prior to other units based on the “Mid-and-Long-Term Decommissioning Action Plan”. NG-DMU would be a valuable tool not only for efficient planning of the operations but also for use during the remote operations in FDR. In the early phases of the development, the elicitation of NG-DMU requirements occurs before the specific concept development of robotic equipment, which poses a significant challenge. Task analysis is used as an effective method to facilitate requirement capture for NG-DMU and support some aspects of the FDR implementation. Furthermore, the challenging environment of the Fukushima site complicates the Use Case Analysis even more. The uncertainty and complexity of the environment of the pedestal for supporting a Reactor Pressure Vessel inside the Primary Containment Vessel (PCV) and low maturity of the FDR strategy make the identification of the tasks and their sequence non-trivial. Site surveys provide valuable information about the environment. However, a complete representation of the environment is not available during task analysis, and certain assumptions have still to be made. For example, it is known that solid debris lumps and deposits remain at the bottom of the pedestal, and broken structures are piled up over it but the exact physical relationship between the structure and the debris is not yet established. Similarly, several assumptions have been made about the remote handling equipment which consists of a long reach arm, a multiple degree of freedom manipulator and an end-effector concept, referring to the promising devices for small scale FDR for Unit 2. This paper describes in more detail the task analysis process followed for the FDR to identify and prioritize tasks that can be supported by the NG-DMU and support its definition. The process involves several steps, from setting operational goals, breaking down tasks into manageable sets, with initial and final boundary conditions, etc. It is demonstrated that task analysis is a valuable tool for the development of a DMU that can be reconfigurable and easily adaptable to cover a range of operational needs or changes in the assumptions earlier in the development phase.
