29th Symposium on Fusion Technology (SOFT 2016)

P1.176 Effect of irradiation hardening on deformation behavior of blanket structures fabricated by F82H

5 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 176

Poster I. Materials Technology P1 Poster session

Speaker

Takeshi Miyazawa (Japan Atomic Energy Agency)

Description

The box structure of water-cooled solid breeding (WCSB) blanket fabricated by F82H is being developed in Japan for the DEMO reactor. In the DEMO operation, the structural materials in the region of first wall (FW) will be exposed to severe fusion neutron irradiation. One of the issues is the loss of ductility for the structural materials due to severe fusion neutron irradiation. In the case of in-box loss of coolant accident (LOCA), the pressure of the pressurized water reactor (PWR) will be loaded inside the box structure and then cause the large deformation of the structural materials. The objective of this work is to estimate the effect of irradiation hardening on deformation behavior of the blanket structures under the internal pressure assuming in-box LOCA. Structural analysis of the box-shaped blanket with a surface crack at the coolant corner was conducted by elastic-plastic finite element analysis (FEA). True stress vs. true strain curve of F82H-IEA-heat tested at 300 ^ooC was employed for the FEA. The curve for irradiated F82H-IEA-heat was estimated based on engineering stress-strain curve and true fracture strain estimated from reduction of area. The Isotropic hardening rule was employed for the plastic deformation behavior of the materials. The internal pressure of 15.5 MPa was applied to cooling channels and the inner surface of the box-shaped blanket. FEA was conducted in order to evaluate the crack-tip stress fields. Irradiation hardening of structural materials suppressed crack-tip opening under applied internal pressure.  However, the high stress triaxiality factor (STF) for irradiated materials was widely distributed ahead of crack-tip compared to that for unirradiated materials. Therefore, irradiation hardening was prone to accelerate the ductile crack propagation. Further analysis on the crack initiation and propagation behavior will be discussed in this paper.