Time-of-flight ultrasonic measurements were conducted on a thick hexagonal block of 304 type austenitic stainless steel, which was used as a reflector in EBR-II and was irradiated to 23 ~ 33 dpa at 37 0 ~ 410 ?C. The results of ultrasonic-implied void swelling and carbide-induced densification were compared with those obtained by immersion density measurements and transmission electron microscope o bservations. The three types of measurements were found to agree rather well with each other, and the variati...
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Development of a non-destructive inspection technique for detecting irradiation-induced microstructural changes of austenitic stainless steels by use of an EBR-II reflector

Ultrasonic testing was conducted on two long (218-245 mm), Type 304 stainless steel blocks with a hexagonal cross-section (50 mm face-to-face thickness) that were removed from the reflector region of the decommissioned EBR-II reactor. Ultrasonic testing is one of the widely used non-destructive testing techniques for material characterization. Ultrasonic waves, currently used as a non-destructive technique to detect cracks, change as a result of interacting with microstructural components and can be em...
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Development of non-destructive inspection technique for microstructures under irradiation using austenitic stainless steel blocks

The recent situation of nuclear power generation gradually requires not only the economic viewpoint but also even greater efforts in accurate evaluations on safety and availability issues. Accordingly, assessments on the integrity of structural components are critical both now and in the future. Structural materials which suffer from age-related degradations especially should have methods to evaluate degradations due to changes in material properties. It is clear that conventionally used extrapolations of...
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Integration of modeling, database and inspection technique for the prediction of the material behavior under irradiation

We propose an advanced digital twin of artifact systems (DTAS) in which physical and numerical models of structural materials at several time scales and length scales are constructed and integrated, while monitoring and inspection data of structural materials are used as input parameters. As DTAS can reproduce the current state of structural materials and predict their degradation through their service life, it can improve the resilience and give plasticity to artifact systems. A portion of the results rela...
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A digital-twin of artifact systems by synthesizing multiscale modeling and monitoring

In this study, we make a new proposal for the maintenance plan to optimize the total cost, which includes the cost of inspection and replacement, and the damage of the accident. It treats the probability distribution of the initial value and degradation rate of the perfo rmance of equipments. We apply it to the pipe thinning phenomenon in PWR secondary systems....
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A Proposal for the Method to Optimize the Maintenance from the Viewpoint of the Cost and Errors of Inspection

We propose acceleration schemes for self-evolving atomistic kinetic Monte Carlo (SEAKMC), which is a promising technique for meso-timescale simulations while maintaining atomistic fidelity. The significant acceleration by a factor of up to ~100 is achieved through the acceleration schemes. Further, the accelerated SEAKMC is applied to the meso-timescale evolution of a cluster of irradiation-induced defects, and we observed the transformation process of the cluster into an energetically stable configuration ...
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Multi-timescale modeling of structural materials while maintaining atomistic fidelity

Development of methods of detecting degradation of irradiated reactor structural materials is required for successful operation of nuclear power plants. Ultrasonic waves, currently used as a non-destructive technique to detect cracks, change as a result of interacting with microstructural components and can be employed to measure radiation-induced changes in microstructure. Bulk-averaged measurements of microstructural changes can be determined usi ng ultrasonic velocity, attenuation and back-wall echo, wh...
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Development of non-destructive inspection technique for microstructuresunder irradiation using decommissioned materials(1) An experimental approach

Abstract It is desired to develop an ultrasonic inspection technique non-destructively measuring various forms of irradiation-induced degradation in structural components of nuclear reactors. In order to evaluate the depth distributions of ir radiation-induced microstructural changes, we have developed a numerical simulation model of ultrasonic wave changes caused by microstructural changes in austenitic stainless steel based on the developed theory of ultrasonic wave propagation for comparison with experi...
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Development of non-destructive inspection technique for microstructures under irradiation using decommissioned materials(2) An theoretical approach

In many cases, the function loss by fatigue and fracture is considered as the ultimate condition of the artificial structure. While various CAE technologies have been developed, a high-precision calculation algorithm has been developed for material damage during repeated loading, which is assumed to be difficult to describe in a digital twin in a computer virtual space. To make high precision evaluation, material damage from cyclic pre-strain is investigated. Then, material damage depends on not only equiva...
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Construction of a meso-space scale model for constructing a high-precision damage estimation rule

1. 緒言課題をまとめた。これらのプロセス事例調査から、 原子力発電所機器の高経年化に的確に対応するには、 ・ 規制側が新技術の実機適用に関する審査を行う上 高経年化機器の状態を正確に把握するための検査・モで参照すべき技術基準類や国内外事例が多く、時 ニタリング技術、その結果に基づき経年劣化の進展を 間を要する一因となっている。 正確に予測するための評価技術、さらにその結果に応 ・新技術に対して、国内外の複数メーカにより同時 じて必要な対応措置を講じるための対応措置(補修等) ・比較評価を行った場合は、比......
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Research on the applicability of new techniques for status monitoring of ageing equipment