Speaker
Mr
Hiroyasu Tanigawa
(Japan)
Description
Crucial issues on the path to fusion power are the development of plasma facing and breeding blanket materials which are capable of withstanding high neutron fluences and high heat fluxes. Reduced activation ferritic/martensitic (RAFM) steels are now considered to be the candidates for structural applications in the fusion demonstration reactor, DEMO, because they have a sound engineering basis. But it is also well recognized that the severe DEMO operating conditions, especially 14MeV fusion neutron irradiation, could cause extra degradation of mechanical properties, such as the loss of plastic deformability which is not covered by current design codes. Thus, estimation methods of materials behavior under 14MeV fusion neutron irradiation and a design methodology for highly irradiated structure have become indispensable elements in DEMO developments.
A critical issue is the materials loss of ductility under irradiation. This loss of plasticity could finally result in unstable crack propagation, when fracture or fatigue crack propagation is the failure mode. 14MeV fusion neutron irradiation effects, especially helium effects, are anticipated to enhance this irradiation induced loss of plasticity. Reports of helium effects such as extra hardening, increment of fatigue crack propagation rate, or increased ductile-brittle transient temperature shift indicate that a certain amount of helium could increase the possibility of unstable fracture. These results are based on simulation irradiation experiments, thus a mechanistic understanding of these property changes based on microstructural analyses is essential.
As of today, there are indications from many studies and helium effects can be modeled or estimated, however, it is mandatory to verify fusion neutron irradiation effects at an early date with 14MeV neutron irradiation. Above all else, the estimation and early experimental verification of the critical condition is found to be essential, up to the condition where no significant 14 MeV fusion neutron irradiation effects are expected and fission irradiation data can be used for design activity, regarding to the fact that an intense 14MeV neutron source – IFMIF - will not be available before 2020’, and only the fission irradiation database and complementary modeling is available for design activity until that time.
Collaboration (if applicable, e.g., International Tokamak Physics Activities)
Broader Approach Activity, JAEA/DOE collaboration
Country or International Organization of Primary Author
Japan
Primary author
Mr
Hiroyasu Tanigawa
(Japan)
Co-authors
Dr
Anton Moeslang
(Karlsruhe Institute of Technology)
Dr
Chikara Konno
(Japan Atomic Energy Agency)
Dr
Dai Hamaguchi
(Japan Atomic Energy Agency)
Dr
Eberhard Diegele
(Fusion For Energy)
Dr
Hideo Sakasegawa
(Japan Atomic Energy Agency)
Dr
Hiroyasu Utoh
(Japan Atomic Energy Agency)
Dr
Hisashi Tanigawa
(Japan Atomic Energy Agency)
Dr
Kenji Tobita
(Japan Atomic Energy Agency)
Dr
Kentaro Ochiai
(Japan Atomic Energy Agency)
Dr
Lance L. Snead
(Oak Ridge National Laboratory)
Dr
Masami Ando
(Japan Atomic Energy Agency)
Dr
Mikhail A. Sokolov
(Oak Ridge National Laboratory)
Dr
Mikio Enoeda
(Japan Atomic Energy Agency)
Dr
Roger E. Stoller
(Oak Ridge National Laboratory)
Prof.
Ryuta Kasada
(Kyoto University)
Prof.
Shuhei Nogami
(Tohoku University)
Dr
Steven Zinkle
(Oak Ridge National Laboratory)
Dr
Takanori Hirose
(Japan Atomic Energy Agency)
Dr
Toshiya Nakata
(Japan Atomic Energy Agency)
Dr
Youji Someya
(Japan Atomic Energy Agency)
Dr
Yutai Katoh
(Oak Ridge National Laboratory)
