[en] Under a framework of JAERI-KEK joint project of high intensity proton accelerator, we have been carrying out a conceptual study of an experimental facility dedicating to the development of transmutation technology using the accelerator driven sub-critical system (ADS). The facility consists of two buildings; named as Transmutation Physics Experiment Facility and Transmutation Engineering Experiment Facility. The former facility is designed to evaluate the neutronics of a fast neutron sub-critical system with a spallation source, to examine the performance of a hybrid system driven by an accelerator, and to study the transmutation properties of minor actinides and long-lived fission products. This report summarizes the present status of the design study of the facility, in particular, focusing on the proton beam injection technique, principal specifications and the safety design policy. (author)