Day Three (July 15, 2010)

[A-5] Maintenance Methods and Welding Technology (Part I)

A-5-1

Application of a Blockage Clearing Method for Drain Pipes in Hamaoka Nuclear Power Plant

Haruhisa HAYASHI (CHUBU Electric Power Co., lnc.)

Abstract
Pipe blockages are caused by an accumulation of sand and rust within the drainage pipes of Hamaoka Nuclear Power Plant, and it is hoped that an efficient blockage clearing method can be established. For these purposes, we have investigated and selected general purpose monitoring equipment for the interior surfaces of pipes and blockage clearing equipment. We have also made applicability assessments using full-sized mockup equipment, the same as actual drainage pipes. Furthermore, we have tested the effectiveness of equipment on actual pipes blockage. The effective blockage clearing method and its application for drain pipes in Hamaoka Nuclear Power Plant its described.

Keywords
drainage pipes, blockages, blockage clearing method

A-5-2

Development of temper bead welding by under water laser welding

Takeshi FUKUDA, Masataka TAMURA, Yuichi TONGU, Wataru KONO, Masaki YODA, Minoru OBATA and Yasuo MORISHIMA (TOSHIBA CORPORATION)

Abstract
Toshiba has developed temper bead welding by under water laser welding as SCC counter measure for aged components in PWR and BWR nuclear power plants. Temper bead welding by under water laser welding technique recovers toughness of low alloy steel reactor vessel by employing proper the number of cladding layers and their welding conditions. In this report, some evaluation results of material characteristics of temper bead welded low alloy steel are presented.

Keywords
Under water laser beam welding, Temper bead welding, low alloy steel

A-5-3

Confirmation test of IHSI for pipe with crack

Takao SASAYAMA (TOSHIBA CORPORATION) and Satoshi HONGO (IHI Corporation)

Abstract
This study is confirmed IHSI which is one of preventive maintenance techniques for stress corrosion cracking, can be applied to pipe with crack. The results were applicable under certain conditions by the test which was used pipe with 3 / 8 depth crack. Following four items were confirmed by this test. 1. Not affect for cracks and joints, 2. Residual stress would be improved with the tip of the crack and can be suppressed with crack growth, 3. Residual stress would be improved around the crack, 4. It can be effective for preventing SCC at non crack area.

Keywords
Crack, IHSI, Stress Improve, SCC, Residual Stress, Preventive maintenance

A-5-4

Development of Seal Welding Repair Technology for CRD Stub-tube

Masaaki TANAKA, Takashi ITO (Hitachi-GE Nuclear Energy, Ltd.), Koichi MATSUMOTO and Yoichi MAHARA (Babcock-Hitachi K.K.)

Abstract
Seal welding is a repair method when crack by Stress Corrosion Cracking (SCC) is found in weld portion of core internals including pressure boundary component in nuclear power plant. Seal welding is welded directly on surface of existing SCC crack and prevents SCC propagation by isolating SCC crack from reactor water environment. In this study, development of seal welding technology using automatic TIG Welding was executed, and the applicability of seal welding method to CRD stub-tube weld portion was confirmed by examination of full scale weld test and analysis.

Keywords
Seal welding, SCC, CRD Stub-tube, TIG Welding, Embeded SCC

A-5-5

INLAY Method Using the Cylindrical Container for Reactor Vessel Outlet Nozzle of PWR for Ohi Nuclear Power Station

Shigeki ICHIKI, Hiroki IWAHASHI, Norio TERADA (The Kansai Electric Power Co., INC.), Yasuo NAKAMURA and Kazuhide YAMAMOTO (Mitsubishi Heavy Industries, LTD.)

Abstract
Preventive maintenance techniques against PWSCC found in Alloy 600 welds have been applied progressively，however，in February 2008, a defect of PWSCC had been found in an outlet nozzle to safe-end weld of Reactor vessel of PWR in Ohi Nuclear Power Station Unit 3 during an outage. Then the defect was removed and after its safety was confirmed, the unit was placed in operation. In the next outage, INLAY method using the cylindrical container was applied and repair welding for the removed part was performed. In addition, circumferential grooving to remove Alloy 600 of the inner surface of the outlet nozzle and circumferential welding with PWSCC resistant Alloy 690 were applied. This circumferential grooving and welding techniques were also applied for all outlet nozzles of Ohi Unit 4 as a preventive maintenance.

Keywords
INLAY, Cylindrical Container, Reactor Vessel Outlet Nozzle, PWSCC, Temper Bead Welding

A-5-6

Application of 3D Laser scan Technique on MHI

Junichi NISHITANI, Mahiro YAMAGAMI, Syunji TANAKA, Tomokazu IWATA (Mitsubishi Heavy Industries, LTD.), Fumitoshi NAKAO and Kazuhito NAKASHIMA (Nuclear Plant Service Engineering Co., Ltd.)

Abstract
Mitsubishi Heavy Industry inc.(MHI) has widely evaluated design of configuration and piping, interference check, workability, work plan by utilize as-built data (using 3D laser scanner) of some compornent and piping etc. set up in Atomic Power Plants(APPs) . This paper introduces some definite applied instance of results obtained by 3D laser scan in which MHI has been engaged.

Keywords
3D Laser scanner，as-built data, panorama photograph, 3D-CAD Modeling, 3D-data failing system, Reduction of Radiation, Maintenance management system

A-5-7

Three-Dimensional Measurement System for In-Vessel Visual Inspection

Tetsuro AIKAWA, Yoshinori SATOH, Tatsuya OODAKE, Makoto OCHIAI and Yasuhiro YUGUCHI (Toshiba Corporation)

Abstract
The main roles of in-vessel visual inspection (IVVI) are to detect cracks on the surface of internal structures and measure the length of the cracks. For accurately performing those matters by visual inspection, inspectors sometimes need to obtain three-dimensional (3D) measurements of cracks and 3D shape of the surface. We have been developing a prototype system to obtain 3D measurements. This system is based on stereo vision technique and has only one measurement head that has an inner movable camera module. This paper reports the outline of the prototype measurement head and its performance.

Keywords
In-Vessel Visual Inspection, Image Processing, Three Dimensional Shape

A-5-8

The Application of Manipulator Robot for Nuclear Plant Maintenance

Yukifumi KOHATA, Jun FUJITA, Ken ONISHI, Hiroyuki TSUHARI and Fumihiro HOSOE (Mitsubishi Heavy Industries, LTD.)

Abstract
In the maintenance works at nuclear power plant, robots are used because of high radiation, 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 manipulator robots developed by MHI, application example to maintenance works and effectiveness of manipulator robots. When robotization of maintenance works are considered, manipulator technology is very effective solution means. We achieved efficiency improvement and the reliability improvement by developing a high generality manipulator.

Keywords
Power Plant Maintenance, Manipulator, Robot

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