Possible explanation on a difference of microstructural evolution in fcc and bcc metals during temperature change after irradiation, is given based on atomistic evaluation of the binding states of helium to a matrix void, a dislocation and a grainboundary. It is here emphasized that the difference of helium bubble formation in those metals is pro duced by the fact: helium atoms are most strongly trapped by a matrix void in bcc metals, while a grainboundary is a strongest trapping site in fcc metals. These ...
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Theoretical Insight into a Difference of Helium Bubble Formation in Austenitic and Ferritic Steels during Post-Irradiation Welding

Challenging efforts are discussed to establish an advanced methodology for prediction of material's property and performance changes by irradiation, which will be necessary by all means for the advanced reactor maintenance technology in the future. The changes of material's properties and perfor mance caused by irradiation, such as irradiation-induced hardening, ductility loss, and material's degradation leading to reduction in reactor lifetime, are primarily determined by microstructural changes in materi...
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How can we predict microstructural changes caused by the multiscale irradiation process occurred in materials havingcomplicated and hierarchical structures?

Fuel cladding is one of the key components in a fission reactor to keep confining radioactive materials inside a fuel tube. During reactor operation, the cladding is however sometimes breached and radioactive materials leak from the fuel ceramic pellet into the coolant water through the breach. The primary coolant water is therefore monitored so that any leak is quickly detected, where the coolant water is periodically sampled and the concentration of, for example the radioactive iodine 131 (I-131), is...
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Monte Carlo Modeling for Realizing Optimized Management of Failed Fuel Replacement

In order to establish the nuclear power system with sufficient safety, a lot of continuous efforts towards pursuing further plant safety should be made, not only at the plant design and construction stages, but also at the plant maintenance after start using as aging management. In many cases, plant aging are associated with material's degradation due to irradiation, cycle fatigue loading, high temperature, high pressure, etc. It is therefore very important that the degradation of materials under those se...
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Theoretical evaluation of oxidation behavior of fuel cladding in light-waterreactor for prediction of fuel reliability

1.はじめに方法である. 例えば運転開始 60 年後の材料劣化の程度を知りたいとしても,実際の照射場を使ったのでは, 軽水炉高経年化対策のひとつに,原子炉圧力容器鋼 材料照射データの取得に 60年もかかってしまう. そこ の中性子照射脆化対策がある.これは,中性子照射にで,中性子エネルギーや中性子束の高い代替の「加速」 よって徐々に劣化する原子炉圧力容器鋼に対する保全照射場を使うことにより,60年よりも短い年数で材料 計画策定を意味するが,このとき必要になる技術課題照射データを取得する.しかしながら,こう......
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Establishment of the irradiation correlation rules of reactor materialstowards the advanced plant life management