The Japan Atomic Energy Research Institute (JAERI) has been developing necessary dismantling techniques to decommission the Japan Power Demonstration Reactor (JPDR) in the JPDR Decommissioning Program since 1981. A cylindrical geometric machine equipped with diamond sawing and coring units has been developed for activated biological shield dismantlement. This machine is suspended from a crane and moves within the inner cylindrical shaped wall fixes its position with built-in outriggers. Cutting process control and point-to-point control are used for automatic cutting. The paper summarizes current status of the biological shield, diamond sawing and coring technique and dismantling sequence, design of the machine, and a dismantling system.