scholarly journals Analysis of Magnetic Nondestructive Measurement Methods for Determination of the Degradation of Reactor Pressure Vessel Steel

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5256
Author(s):  
Gábor Vértesy ◽  
Antal Gasparics ◽  
Ildikó Szenthe ◽  
Madalina Rabung ◽  
Melanie Kopp ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Neutron Irradiation ◽  
Pressure Vessel ◽  
Measurement Methods ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Magnetic Parameters ◽  
Brittle Transition ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition

Nondestructive magnetic measurement methods can be successfully applied to determine the embrittlement of nuclear pressure vessel steel caused by neutron irradiation. It was found in previous works that reasonable correlation could be obtained between the nondestructively measured magnetic parameters and destructively determined ductile-to-brittle transition temperature. However, a large scatter of the measurement points was detected even in the cases of the non-irradiated reference samples. The reason for their scattering was attributed to the local inhomogeneity of material. This conclusion is verified in the present work by applying three different magnetic methods on two sets of Charpy samples made of two different reactor steel materials. It was found that by an optimal magnetic pre-selection of samples, a good, linear correlation can be found between magnetic parameters as well as the ductile-to-brittle transition temperature with low scattering of points. This result shows that neutron irradiation embrittlement depends very much on the local material properties.

Bayesian Uncertainty Evaluation of Charpy Ductile-to-Brittle Transition Temperature for Reactor Pressure Vessel Steels

2020 ◽  
Author(s):  
Hisashi Takamizawa ◽  
Yutaka Nishiyama ◽  
Takashi Hirano
Keyword(s):  
Transition Temperature ◽  
Test Temperature ◽  
Pressure Vessel ◽  
Credible Interval ◽  
Irradiation Embrittlement ◽  
Brittle Transition ◽  
Pressure Vessel Steels ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
Reactor Pressure

Abstract The irradiation embrittlement of reactor pressure vessel steels can be predicted using the ductile-to-brittle transition temperature (DBTT) shift obtained from Charpy impact tests. For the structural integrity assessment considering irradiation embrittlement, it is necessary to set margins for various uncertainties. It is important to understand what and how much factors contribute to the uncertainty. In the present study, a 34% credible interval value of Charpy DBTT at a 41J energy level (T41J) was evaluated by estimating the probability distributions of Charpy test data using Bayesian statistics. To fit the Charpy transition curves, a hyperbolic tangent with coefficients whose uncertainties depend on the test temperature was used. The probability distribution of T41J was estimated using Monte Carlo sampling and Bayesian inference. It was clarified that 34% of the credible-interval values of T41J before and after irradiation unchanged for base and weld metals when the number of specimens and test temperature were equivalent under un-irradiated and irradiated conditions. When the Charpy transition curve was determined by 12 specimens loaded in a surveillance test capsule, the estimated uncertainty of T41J was about 5 °C.

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