Temper bead welding (TBW) is one effective repair welding method for the large-scale nuclear power plants instead of post weld heat treatment (PWHT). Consistent Layer (CSL) technique is the theoretically most authoritative method among the five temper bead welding techniques. For TBW, toughness is the key criteria to evaluate the tempering effect. A neural network-based method for toughness prediction in heat affected zone (HAZ) of low-alloy steel has been investigated to evaluate the tempering effect...
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Prediction of Toughness in HAZ produced by Temper Bead Welding of Consistent Layer Technique

In 1999, NEL developed the transmit-receive type ECT array probe for steam generator (SG) tubing, called “X-probe”, in cooperation with foreign firms. Recently NEL has developed the advanced ECT array probe, “Smart Array Probe”, characterized with a significantly improved resolution for circumferential cracks. The doubled channels in the circumferential mode have greatly improved the circumferential resolution of Smart Array Probe. With all the circumferential mode channels on the same circle, there i...
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Development and Field Practical Performance of Smart Array Probe

In Japan, the preventive maintenance task of the 600 series nickel basis alloy weld of the reactor vessel (RV) and the steam generator (S/G) safe end weld are pushed forward sequentially, and a defect sizing using the ultrasonic testing (UT) from the inside of the safe end is carried out when the defect was dete cted by surface inspection prior to the work. Some defects are recognized on the S/G safe end and the R/V safe end in Japan, and these defects have occurred in the axial direction of the safe end w...
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Development of Advanced Defect Sizing Technique Using Ultrasonic Testing for Nozzle Welding

Recently, preventive maintenance tasks for welding of safe-end nozzles of reactor vessels and steam generators of PWRs in Japan had been carried out sequentially. Before the maintenance tasks, inspection services were carried out and several crack indications were found by eddy current testing (ECT). These indications were found in the welding which made b y 600 series nickel base alloy and evaluated as stress corrosion cracks which were oriented to the axial direction of the nozzle. Then investigations to...
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Development of the advanced phased array UT technique for accurate sizing of cracks in the nozzlewelding

From the engineering development to actual application of the new maintenance technique used for the maintenance activities of a nuclear reactor in operation, the JANTI Guide line, “the Guideline on the Application Process of a Maintenance Technique“ was developed to clarify activities to be checked or examined in each process. In engineering deve lopment, all activities are provided to be checked or examined at each process followed further, such as standardization process. It is important to carry out sh...
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Guideline on Application Process of Techniques Developed for Maintenance Activities

Alloy 600, highly heat resistant and corrosion resistant, is widely used in nuclear power plant components, such as re actor pressure vessel nozzles and steam generator nozzles. However, some Alloy 600 components have recently experience d defects in Japan and abroad. In this regards, enhanced maintenance measures are required to deal with this problem. This paper describes representative defects; PWSCC in Alloy 600 components and summarizes countermeasures in advance....
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Maintenance Techniques on PWSCC of Ni Alloys Used as PWR Pressure Boundary Materials

In August 2004, a pipe rupture accident occurred at The Kansai Electric Power Company Mihama Unit3. Japan Society of Mechanical Engineers (JSME) recognized that it was an urgent problem to settle the rules on Pipe Wall Thinning Management by Fluid Flow. JSME enacted “rules on Pipe Wall Thinning“ that stipulates the basic requirements of pipe wall thinning management, considering from these situations. In 2006 , JSME enacted the “rules on Pipe Wall Thinning Management for PWR Power Plants” (JSME S NG1-2006...
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Analysis of Data on Pipe Wall Thinning Phenomena by Fluid FlowIn Pressurized Water Reactor Plant

Japanese government has recently addressed a policy to increase capacity factor of existing nuclear PPs to achieve the goal to decrease the emission of CO2. Numerous preventive measures have taken in nuclear power plants to minimize the risk of unexpected long shutdown. Newly developed mitigation measures or repair methods need to be qualified to satisfy regulatory standards, before it is implemented to nuclear power plants. The qualification process needs to comply regulatory standards though it may consum...
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R/D and implement of temper bead welding as newly developed maintenance technique in nuclear power plant

Abstract For the last couple of years, issue of defects in Alloy 600 weld lowered the capacity factor of nuclear power plants. To apply newly developed repair technique, like temper-bead welding that has not been prescribed in technical standards, it is necessary to evaluate its technical applicability to the requirement. In the previous cases, this process has been completed by issuance of no action letter for specific area and condition, utilizing implementation process, such as confirm testing by J...
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Study on implementing newly developed repair welding technique within a limited time frame for nuclear power plant

One year has passed since Electronic Journal of Advanced Maintenance (EJAM) was started on the website of Japan Society of M aintenology (ISM) May 25“, 2009. “New Technology' (NT) is one of the EJAM categories, and introduces widely advanced techniqu es developed or modified for maintenance. Twenty-two NT articles have been introduced on EJAM website so far as of May 25t“, 2010. This report describes the concept of NT, general features of NT articles, actual performance and future wishes for NT....
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Current Status of EJAM ‘New Technology