During the field work of the core shroud replacement project of Tsuruga power station unit 1 in December 1999, when it had almost 30 years operation experience since the commencement of commercial operation in March 1970, many cracks were detected visually at the shroud support to reactor pressure vessel (RPV) weld metal (Ni-based alloy: Alloy 182) and confirmed with penetrant testing as well as by metallographic observation. Almost all cracks were found to propagate in the axial direction of the RPV ...
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Evaluation on Crack Growth Analysis Model based on the Knowledge obtained from Stress Corrosion Cracking in Ni-based Alloy used for a Long Time in a BWR

The maintenance evaluation for research reactors has been obligated in Japan from 2004 as for power reactors. JAEA (Japan A tomic Energy Agency) has started to evaluate the maintenance for own research reactors on 2004. In this paper, we report th e present status of the maintenance for JRR-3(Japanese Research Reactor No.3), as well as the linear evaluation methods use d. It is found that a series of preventing maintenance task on equipment and building of the reactor is properly performed....
英字タイトル:
Assessment of Preventing Maintenance on Japanese Research Reactor JRR-3

Many Swagelok connections are used in the instrumental tube pipe of Nuclear power plant because Swagelok conne ion is easy to put on and take off quickly. Although Swagelok connection is easy handling, it occurs very sma ll amount of leakage in some case. For the purpose of development of quick repair method for small amount leak e of Swagelok connection, we considered the base technique about the miniature cramp for Swagelok connection....
英字タイトル:
Development of Miniature Cramp for Swagelok Connection Temporary Repair

Magnetic properties derived from major hysteresis loops are sensitive to the microstructures of iron-based steels and have therefore been used for nondestructive evaluation of degradation in ferromagnetic materials contained in structural components. A permeability obtained from ac small field excitation may be a more us eful parameter than one obtained from a major hysteresis loop from the viewpoints of electricity consumption and real-time measurement. In this paper, the relati on between the ac permeabi...
英字タイトル:
Evaluation for Mechanical Properties of Ferromagnetic Steels by AC Permeability

This paper describes localization and cable handling me thod as the underlying techniques for underwater surveyrobot. Map matching method comparing cross-sectional hape data cut from a 3-D CAD with structural shapesmeasured by a range sensor is proposed as the localiza tion. The cable handling system mounted to a robot isdeveloped to operate the cable remotely. Some experime nts to evaluate performance of the proposed techniqueswere implemented at mock-ups of a reactor building and he real field. As a resu...
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Development of underlying techniques for underwater survey robot to decommission nuclear power plants

After 2002, Stress Corrosion Cracking (SCC) came to be detected in the low carbon stainless steel PLR Piping of BWR plants. However, it worked on the improvement of ultrasonic examination technology for PLR Piping in Japan BWR Owners Group (JBOG) , because the mistake of the evaluation was caused as a rare case. In this study, it introduces the improvement of ultrasonic testing technology and evaluation....
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Know-How for the Ultrasonic Examination Practice & Evaluation of PLR Piping

This study demonstrates the possibility of applying magnetic methods to pressure vessel surveillanc e at nuclear power plants. Magnetic hesteresis-minor-loop measurement and TEM observation were pref ormed on thermally aged Fe-1.0wt%Cu model alloys. Minor loop parameters decreased with increasing a ging time. The mechanism is discussed in terms of Cu precipitation behaviors of cold-rolled alloys....
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Relation between Precipitation Behaviors and Magnetic Properties in Cold-rolled FeCu Model Alloys

This study demonstrates the possibility of applying magnetic methods to pressure vessel surveillance at nuclea r power plants. Charpy impact test and magnetic hysteresis-loop measurement were preformed on Fe-1.0wt%Cu model alloys. The ductile-brittle transition temperature and the coercivity increased by cold-rolling and thermal agi ng. This correlation originates from an increase in the dislocation density and a formation of Cu precipitates....
英字タイトル:
Magnetic Properties of FeCu Model Alloys Embrittled by Cold-rolling and Thermal Aging

This study developed an apparatus for the measurement of magnetic properties of tensile test specimen. Experimental results show that the difference shape of BH curves of the steels cold-rolled with different rolling reduction. The coercive force has good correlation with Ductile-brittle transition temperature and Vickers hardness of the specimen. This result indicate s the possibility of nondestructive evaluation for the mechanical properties of tensile test pieces using magnetic methods....
英字タイトル:
NDE for Mechanical Properties of Ferromagnetic Steels using Magnetic Measurement Apparatus

Needs for development of practical technologies such as repair and mitigation, and necessity of conceptual summarization on those technologies are proposed. Temporary repair technology is focused in particular, to discuss its development needs for simple application and effectiveness for short period. Next, aggressive movements for standardization of allowable leak rules and repair technologies including the tentative ones in the United States are pointed out to find a promising orientation of utilizing...
英字タイトル:
Needs for Temporary Repair Technology and Concept of Mitigation