Microstructural assessment of damaged materials in FBR assessment of creep damage in weldment

Momma, Yoshio*; ; ; ; ; Aoto, Kazumi

JNC TN9400 2000-044, 22 Pages, 2000/03

JNC-TN9400-2000-044.pdf:1.37MB

ln the past the microstructural observation was mostly applied to understand the materials behavior qualitatively in R&D of the new materials and the life prediction for the fast breeder reactor components. However, the correlation between the changes in properties and microstrutures must be clarified to ensure the structural integrity. Particularly we are interested in the method to correlate the long-term properties and microstructural changes at high temperatures. The current research is to quantify the changes in microstructure of the weld metal for the welded structure of the reactor vessel. ln this research we have conducted creep testing of the weld metals at 823 and 873K up to 37,000h. Two types of the weld metals (16Cr-8Ni-2Mo and 18Cr-12Ni-Mo) were subjected to the creep testing. Based on the areas of the precipitates, the microstructural characterization with time and creep damage was attempted. The creep strength of the 16Cr-8Ni-2Mo weld metal is lower than that of the 18Cr-12Ni-Mo one at higher stresses, shorter times. But there is a trend toward to become similar strength with lower stresses and increasing times. The creep-rupture ductility of the 16Cr-8Ni-2Mo weld metal is superior to that of the 18Cr-12Ni-Mo one. The creep-rupture takes place at the interface of the sigma () phases precipitated in the delta () ferrites at 823K lower stresses and 873K. The amount of precipitates in the 16Cr-8Ni-2Mo weld metal is smaller than that in the 18Cr-12Ni-Mo one at each temperature and stress. Also it is apparent that the amount of the precipitates is primarily responsible to the decomposition of the phase, because the amount of the residual ferrites measured by the Magne-Gauge reduces with times. Using the Larson-Miller parameter it was possible to correlate the amount of the precipitates linearly with the LMP values.

Development of fatigue testing techniques using solid round bar miniature specimens

Imagawa, Yuya; Toyota, Kodai; Onizawa, Takashi

no journal, , 

no abstracts in English

Development of the material strength standard of 316FR steel and modified 9Cr-1Mo steel for next-generation fast reactor in Japan

Onizawa, Takashi; Toyota, Kodai; Imagawa, Yuya; Okajima, Satoshi; Ando, Masanori

no journal, , 

In order to realize a fast reactor that achieves both safety and economic efficiency at a high level, Japan Atomic Energy Agency (JAEA) is developing the material strength standard for fast reactor design. JAEA has developed the material strength standard based on the acquired data and its evaluation results, and the standard have been incorporated in the Japan Society of Mechanical Engineers (JSME) code, Rules on the Design and Construction of Nuclear Power Plants, Section II, Fast Reactors (JSME D&C FRs Code). This paper describes the standard that recently incorporated in the JSME D&C FRs code and ongoing studies for improvements in the near future.