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Nishiyama, Yutaka; Ebihara, Kenichi; Yamaguchi, Masatake; Onizawa, Kunio; Matsuzawa, Hiroshi*
no journal, ,
The effect of dose-rate on grain-boundary phosphorus (P) segregation in neutron-irradiated reactor pressure vessel steels has been determined by scanning Auger electron microprobe. The neutron flux ranged from 1
10
to 110
n/cm
/sec up to a fluence of 110
n/cm at 290
C. The comparisons made between the model prediction using rate equation and experimental observations indicate that the grain-boundary P is not affected by the dose-rate in the present range.
Katsuyama, Jinya; Tobita, Toru; Nishiyama, Yutaka; Onizawa, Kunio
no journal, ,
The metallurgical structures and fracture toughness in heat-affected zone (HAZ) of rector pressure vessel (RPV) steels have been studied. Typical RPV plates and their butt-weld joints were produced by multi-pass welding. Inhomogeneity of metallurgical structures such as grain size and phase distribution in HAZ of weld joints has been characterized by microscopic observation and thermal analysis by finite element method. Based on these results, several kinds of simulated HAZ materials varying grain size and microstructure were produced from the plates. Results showed that there were clear differences in mechanical properties such as fracture toughness among typical HAZ materials and the base plate. Preliminary results of neutron irradiation tests are also presented for base metal and some simulated HAZ materials.
Takeuchi, Tomoaki; Kuramoto, Akira*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Hasegawa, Masayuki*; Yoshiie, Toshimasa*; Katsuyama, Jinya; Nishiyama, Yutaka; Onizawa, Kunio
no journal, ,
The dose dependence of the micro structural evolution and its correlation with hardening of the reactor pressure vessel (RPV) steel irradiated with neutrons is investigated. The two kinds of A533B-1 steels of different chemical compositions irradiated at JMTR with the almost same flux from 1.6 to 1.910n cm
s
and the wide range of dose from 0.32 to 9.910
n cm are studied using the Vickers micro hardness, the positron annihilation, and the three-dimensional local electrode atom probe (LEAP) techniques. Results indicate that the gradual hardening of the high impurities steel from the middle to the late stage is caused by the solute nano-clusters enriched with Cu, Si, Mn, Ni, and P. It is also suggested the rapid hardening of both steels at the early stage of irradiation is caused by mainly matrix defects, especially small size vacancies and/or dislocations.
Yamaguchi, Masatake; Ebihara, Kenichi; Nishiyama, Yutaka; Onizawa, Kunio; Matsuzawa, Hiroshi*
no journal, ,
From first-principles (using VASP), we calculated the energy parameters such as the formation and migration energies of point defect (vacancy or interstitial) and the defect-phosphorous (P) complexes in bcc Fe and fcc Ni. For bcc Fe system, the stability of a Fe-P mixed dumbbell pair and an interstitial P are similar with each other. Although there are some differences, our results are in overall agreement with the other previous results using SIESTA code. For fcc Ni system, on the other hand, the Ni-P mixed dumbbell cannot be stabilized and thus only interstitial P is formed.