In the maintenance works at nuclear power plant, robots are used because of high r adiation, narrow space and underwater work. Various robots are needed because there is various maintenance works. This is inefficiency. As the solutions, we developed manipulator robots for the access of specialized tools. This study shows manipulato r robots developed by MHI, application example to maintenance works and effectivene ss of manipulator robots. When robotization of maintenance works are considered, ma nipulato...
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The Application of Manipulator Robot for Nuclear Plant Maintenance

A design study of an advanced sodium-cooled fast reactor (Advanced-SFR) has been conducted in Japan Atomic Energy Agency (JAEA). Hot sodium from the fuel assembly can mix with cold sodium from the control rod (CR) channel and the blanket assemblies at the bottom plate of the Upper Internal Structure (UIS). Temperature fluctuation due to mixing of the fluids at different temperature between the core outlet and cold channel may cause high cycle thermal fatigue on the structure around the bottom of UIS. A wate...
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Water Experiments on Thermal Striping Phenomena at the Core Outlet of an Advanced Sodium-cooled Fast Reactor? (1) Proposal of Countermeasures to Mitigate Temperature Fluctuations around Control Rods?

Focusing on the thermal striping phenomena that occurs at a bottom of the internal structure of an advanced sodium-cooled fast reactor (Advanced-SFR) that has been designed by the Japan Atomic Energy Agency, a water experiment using a 1/3 scale 60 degree sector model simulating the upper plenum of the Advanced-SFR has been conducted to examine countermeasures for the significant temperature fluctuation generated around the bottom of Upper Internal Structure (UIS). In the previous paper, we reported the effe...
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Water Experiments on Thermal Striping Phenomena at the Core Outlet of?an Advanced Sodium-cooled Fast Reactor? (2) Proposal of Countermeasures to Mitigate Temperature Fluctuations?around Radial Blanket Fuel Assemblies?

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

山本 智 Satoshi YAMAMOTO Non-Member (Times New Roman 10pt) should be about 150 words. Recently, an application target of the phased array ultrasonic testing (PAUT) has been extended. For the inspection of CASS, low frequency (less than 1 MHz) array probe is required. Low frequency array probe are usually constructed by large pitch element. In the case of linear scanning, the low frequency array probe could not obtain enough number of sound beams which construct a precise B-Scope image owing to non-dense arra...
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Accuracy improvement of the linear scanning phased array UT with a large element array probe

The Fukushima Daiichi nuclear disaster was initiated by the Tohoku earthquake and subsequent massive tsunami on 11 March 2011. To prevent the event as the Fukushima Daiichi nuclear disaster, we had implemented the necessary safety reinforcement measures in Shika Nuclear Power Stations. In this paper, we are going to introduce the flood prevention measures that prevent seawater from entering the power stations. And we also secured emergency power supplies for the case of loss of all AC power supplies. I...
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The Safety Reinforcement Measures at Shika Nuclear Power Station

Phased Array Ultrasonic Testing (PAUT) techniques for complex geometries are greatly progressing. We developed an immersion PAUT which is suitable for complex surface profiles such as nozzles and deformed welded areas. Furthermore, we have developed a shape adaptive beam steering technique for 3D complex surface structures with conventional array probe and flexible coupling gel which makes the immersion beam forming technique usable under dry conditions. This system consists of 3 steps. Step1 is surfac...
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Verification and Application of Beam Steering Phased Array UT Technique for Complex Structures

The structural integrity for Pressurized Thermal Shock (PTS) was evaluated for the RPVs of Japanese Boiling Water Reactors (BWRs). It has been clarified that the BWR RPVs have the sufficient margin of fracture toughness by calculating the stress intensity factor in transitional condition and the acceptance criteria for RPV shell plate which is assumed to be neutron-irradiated in core region for 60 years. ...
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Evaluation of Pressurized Thermal Shock in transitional condition for Boiling Water Reactor pressure vessel

This paper aims at detecting thinning of the back surface of a steel double sided structure. Our proposed technique is characterized by using pulsed eddy current testing with DC magnetization. When a double structural steel is magnetized by DC current, flux leakage is generated as a result of thinning on the back surface. We have shown by the use of simulations that the permeability of the top plate has changed with flux leakage from the back plate. The steel plate without thinning and the steel plate...
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Detecting Thinning on Back Surface of Double Structure of Steel by Pulsed Eddy Current Testing with DC magnetization

At the case of the replacement of instrumentation and/or control system for the common and large capacity facilities such as a compressed service air supply system, it is very important to proceed this work in short period and without any influence to the operation of many number of this users. In order to realize this fundamental requirement, enough consideration, evaluation ,and countermeasures to the risk by FMEA have been executed since planning stage. By means of these activities, a stable operation...
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Achievement of the replacement of the instrumentation and control system during continuous operation of the common and large capacity facilities