Predicting the transition-temperature shift(TTS)induced by neutron irradiation in reactor pressure-vessel(RPV)steels is important for the evaluation and extension of nuclear power-plant lifetimes.Current prediction mo...Predicting the transition-temperature shift(TTS)induced by neutron irradiation in reactor pressure-vessel(RPV)steels is important for the evaluation and extension of nuclear power-plant lifetimes.Current prediction models may fail to properly describe the embrittlement trend curves of Chinese domestic RPV steels with relatively low Cu content.Based on the screened surveillance data of Chinese domestic and similar international RPV steels,we have developed a new fluencedependent model for predicting the irradiation-embrittlement trend.The fast neutron fluence(E>1 MeV)exhibited the highest correlation coefficient with the measured TTS data;thus,it is a crucial parameter in the prediction model.The chemical composition has little relevance to the TTS residual calculated by the fluence-dependent model.The results show that the newly developed model with a simple power-law functional form of the neutron fluence is suitable for predicting the irradiation-embrittlement trend of Chinese domestic RPVs,regardless of the effect of the chemical composition.展开更多
The crystal structure evolution of the Cu-rich nano precipitates from bcc to 9R during thermal aging was studied in nuclear reactor pressure vessel （RPV） model steels. The specimens, contained higher copper and nick...The crystal structure evolution of the Cu-rich nano precipitates from bcc to 9R during thermal aging was studied in nuclear reactor pressure vessel （RPV） model steels. The specimens, contained higher copper and nickel contents than commercially available one, were heated at 890 ~C for 0.5 h and then water quenched followed by tempering at 0（50 ~C for I0 h and aging at 400 ~C for 1000 h. It was observed that bcc and 9R orthogonal structure, as well as 9R orthogonal and 9R monoclinic structure, coexist in a single Cu-rich nano precipitate. Further analyses pointed out that Cu-rich nano precipitates of bcc structure were not stable, it may preferentially transform to 9R orthogonal structure and then to 9R monoclinic structure. This results showed that the crystal structure evolution of the Cu-rich nano precipitates was complex.展开更多
During a hypothetical severe accident of light water reactors,the reactor pressure vessel(RPV) could fail due to its creep under the influence of high-temperature corium.Hence,modelling of creep behavior of the RPV is...During a hypothetical severe accident of light water reactors,the reactor pressure vessel(RPV) could fail due to its creep under the influence of high-temperature corium.Hence,modelling of creep behavior of the RPV is paramount to reactor safety analysis since it predicts the transition point of accident progression from in-vessel to ex-vessel phase.In the present study we proposed a new creep model for the classical French RPV steel 16 MND5,which is adapted from the "theta-projection model" and contains all three stages of a creep process.Creep curves are expressed as a function of time with five model parameters θ_i(i=1-4 and m).A model parameter dataset was constructed by fitting experimental creep curves into this function.To correlate the creep curves for different temperatures and stress loads,we directly interpolate the model’s parameters θ_i(i=1-4 and m) from this dataset,in contrast to the conventional "theta-projection model" which employs an extra single correlation for each θ_i(i=1-4 andm),to better accommodate all experimental curves over the wide ranges of temperature and stress loads.We also put a constraint on the trend of the creep strain that it would monotonically increase with temperature and stress load.A good agreement was achieved between each experimental creep curve and corresponding model’s prediction.The widely used time-hardening and strain-hardening models were performing reasonably well in the new method.展开更多
文摘Predicting the transition-temperature shift(TTS)induced by neutron irradiation in reactor pressure-vessel(RPV)steels is important for the evaluation and extension of nuclear power-plant lifetimes.Current prediction models may fail to properly describe the embrittlement trend curves of Chinese domestic RPV steels with relatively low Cu content.Based on the screened surveillance data of Chinese domestic and similar international RPV steels,we have developed a new fluencedependent model for predicting the irradiation-embrittlement trend.The fast neutron fluence(E>1 MeV)exhibited the highest correlation coefficient with the measured TTS data;thus,it is a crucial parameter in the prediction model.The chemical composition has little relevance to the TTS residual calculated by the fluence-dependent model.The results show that the newly developed model with a simple power-law functional form of the neutron fluence is suitable for predicting the irradiation-embrittlement trend of Chinese domestic RPVs,regardless of the effect of the chemical composition.
基金financially supported by the National Basic Research Program of China(No.2011CB610503)National Natural Science Foundation of China(No.50931003)Ministry of Major Subject of Shanghai(No.S30107)
文摘The crystal structure evolution of the Cu-rich nano precipitates from bcc to 9R during thermal aging was studied in nuclear reactor pressure vessel （RPV） model steels. The specimens, contained higher copper and nickel contents than commercially available one, were heated at 890 ~C for 0.5 h and then water quenched followed by tempering at 0（50 ~C for I0 h and aging at 400 ~C for 1000 h. It was observed that bcc and 9R orthogonal structure, as well as 9R orthogonal and 9R monoclinic structure, coexist in a single Cu-rich nano precipitate. Further analyses pointed out that Cu-rich nano precipitates of bcc structure were not stable, it may preferentially transform to 9R orthogonal structure and then to 9R monoclinic structure. This results showed that the crystal structure evolution of the Cu-rich nano precipitates was complex.
基金support from the research programs of APRI,ENSI and NKSsupport of the scholarship awarded by the China Scholarship Council(CSC)。
文摘During a hypothetical severe accident of light water reactors,the reactor pressure vessel(RPV) could fail due to its creep under the influence of high-temperature corium.Hence,modelling of creep behavior of the RPV is paramount to reactor safety analysis since it predicts the transition point of accident progression from in-vessel to ex-vessel phase.In the present study we proposed a new creep model for the classical French RPV steel 16 MND5,which is adapted from the "theta-projection model" and contains all three stages of a creep process.Creep curves are expressed as a function of time with five model parameters θ_i(i=1-4 and m).A model parameter dataset was constructed by fitting experimental creep curves into this function.To correlate the creep curves for different temperatures and stress loads,we directly interpolate the model’s parameters θ_i(i=1-4 and m) from this dataset,in contrast to the conventional "theta-projection model" which employs an extra single correlation for each θ_i(i=1-4 andm),to better accommodate all experimental curves over the wide ranges of temperature and stress loads.We also put a constraint on the trend of the creep strain that it would monotonically increase with temperature and stress load.A good agreement was achieved between each experimental creep curve and corresponding model’s prediction.The widely used time-hardening and strain-hardening models were performing reasonably well in the new method.
