American Nuclear Society

Home / Publications / Journals / Fusion Science and Technology / Volume 75 / Number 5

Japan’s Efforts to Develop the Concept of JA DEMO During the Past Decade

Kenji Tobita, Ryoji Hiwatari, Yoshiteru Sakamoto, Youji Someya, Nobuyuki Asakura, Hiroyasu Utoh, Yuya Miyoshi, Shinsuke Tokunaga, Yuki Homma, Satoshi Kakudate, Noriyoshi Nakajima, the Joint Special Design Team for Fusion DEMO

Fusion Science and Technology / Volume 75 / Number 5 / July 2019 / Pages 372-383

Technical Paper /

Received:June 15, 2018
Accepted:March 26, 2019
Published:June 20, 2019

This paper summarizes the evolution of Japanese DEMO design studies in a retrospective manner by highlighting efforts to resolve critical design issues on DEMO. Japan is currently working on the conceptual study of a steady-state DEMO (JA DEMO) with a major radius Rp of 8.5 m and fusion power Pfus of 1.5 to 2 GW based on water-cooled solid breeding blanket with pressurized water reactor water condition (290ºC to 325ºC, 15.5 MPa). Such a lower Pfus allows to find realistic design solutions for divertor heat removal. Recognizing that divertor heat removal is one of the most challenging issues on DEMO, the divertor design has been carried out in different approaches, including numerical divertor plasma simulation, magnetic configurations, heat sink design, etc. It is noteworthy that the latest divertor simulation led to a design window allowing divertor heat removal of the peak heat flux of <10 MW/m2. The breeding blanket (BB) design has been concentrated on simplification of the internal structure and pressure tightness of the BB casing against the in-box loss-of-coolant accident. Due to a large amount of radioactive waste generated in periodic replacement of in-vessel components, downsizing of waste-related facilities has come to be regarded as a significant design issue. A possible waste management for reducing temporary waste storage was proposed, and its impact on the plant layout was assessed.