[en] It is the objective of this demonstration test program to ensure safe transport of the vitrified high active wastes resulting from reprocessing plants of COGEMA at La Hague and of BNFL at Sellafield, which will be returned to Japan according to the contracts signed by the reprocessors with Japanese utilities. In this program, transportable casks for vitrified wastes are being designed and fabricated, and subjected to drop tests and thermal tests, etc. to assure that the requirements are satisfied in accordance with the performance and acceptance standards prescribed in the transport regulations for radioactive material. Since design specifications of both type of transportable casks for vitrified wastes being developed by COGEMA and BNFL have not yet been finalized, the demonstration test cask designed combines the COGEMA and BNFL cask with specific structural features of both types. This paper gives a description of the design concept and configuration of this HYBRID-type demonstration test cask, as well as the test plan for normal and accident conditions hereafter. (author)