Micromagnetic Characterization of Operation-Induced Damage in Charpy Specimens of RPV Steels

Abstract

The embrittlement of two types of nuclear pressure vessel steel, 15Kh2NMFA and A508 Cl.2, was studied using two different methods of magnetic nondestructive testing: micromagnetic multiparameter microstructure and stress analysis (3MA-X8) and magnetic adaptive testing (MAT). The microstructure and mechanical properties of reactor pressure vessel (RPV) materials are modified due to neutron irradiation; this material degradation can be characterized using magnetic methods. For the first time, the progressive change in material properties due to neutron irradiation was investigated on the same specimens, before and after neutron irradiation. A correlation was found between magnetic characteristics and neutron-irradiation-induced damage, regardless of the type of material or the applied measurement technique. The results of the individual micromagnetic measurements proved their suitability for characterizing the degradation of RPV steel caused by simulated operating conditions. A calibration/training procedure was applied on the merged outcome of both testing methods, producing excellent results in predicting transition temperature, yield strength, and mechanical hardness for both materials.

Investigation of the Influence of Neutron Irradiation on Cladded Nuclear Reactor Pressure Vessel Steel Blocks by Magnetic Adaptive Testing

“…Similar to the results reported previously on Charpy specimens [8], neutron irradiation caused measurable changes in the material properties. Neutron irradiation at low fluences generates a significant modification of the material properties [14], while a further increase of the neutron fluence causes a saturation for higher fluence levels. This means that the present results on RPV blocks are in good correlation with the expectation, based on previous measurement.…”

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

“…The 3MA process should be calibrated on a calibration set of samples (with well-known properties, such as DBTT or hardness) [ 10 , 18 ]. For mechanical-technological materials characterization, the measuring parameters are registered by the PC and are further processed having performed all measurements and analyses, the software delivers the magnetic fingerprint (MFP) of the material properties, which can be used for quantitative and qualitative materials characterization.…”

“…The general conclusion of these efforts was that a reasonable correlation had been found between the nondestructively measured magnetic parameters and the destructively measured DBTT if the above mentioned methods are applied [ 8 , 9 , 10 ]. It seems that magnetically measured parameters have a better potential to characterize the material embrittlement than the conventional destructive methods.…”

Magnetic Investigation of Cladded Nuclear Reactor Blocks

“…In several previous works [16,20,[25][26][27] irradiated Charpy samples were measured using magnetic methods, and results of magnetic measurements were compared with the destructively measured ductile to brittle transition temperature (DBTT). However, for the full inspection of nuclear reactors, blocks cut from RPV steel should be also measured, not only samples of Charpy geometry.…”