Similar cracking events have been occurring on steam generator nozzles of Japanese PWR plants since the first case was found at Mihama-2 in September 2007. These cracks were found by eddy current test (ECT) prior to performing a kind of shot peening as a preventive measure on dissimilar metal weld (DMW), a nd were considered as primary water stress corrosion cracking (PWSCC) based on cause investigation. It was pointed out that surface finishing such as grinding or machining played an important role on cra...
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Cracking Events on PWR Steam Generator Nozzles and Its Relationship to Inspection Rules

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....
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Development of Miniature Cramp for Swagelok Connection Temporary Repair

Tsuruga Power Station Unit 2 (1,160 MW, PWR) has been operated since February 1987, and has long term maintenance experience for the past 29-years. Tsuruga Unit 2 is the first plant which applied prestressed concrete vessel (PCCV) in Japan. In-service inspection has been applied to PCCV, and it has been maintained good condition in spite of long term operation. Before the passing of 30 years from the start of operation, a technical evaluation of degradation of the PCCV due to aging needs to be performe...
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Maintenance experience and Plant Life Management for Prestressed Concrete Containment Vessel of Tsuruga Power Station Unit 2

At Tokai No. 2 Power Plant, the fourth monitoring test is conducted to confirm the tendency of reactor pressure vessel steels to become brittle due to neutron irradiation. From the results of the Charpy impact test, the amount of transition of the upper shelf absorbed energy and the related temperature was evaluated, and it was confirmed that there was no significant tendency to embrittlement. We report the results of the 4th monitoring test and discuss the results. ...
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Report of the reactor pressure vessel steel material surveillance test results (the 4th) at Tokai No. 2 Power Station

It has been newly required as a regulatory standard that the blowout panel installed in the reactor building of BWR can be closed promptly when it is opened. In Tokai No. 2 Power Plant, a blowout panel closing device was developed to meet this requirement. In this report, we describe the design of blowout panel closing device and report the result of vibration test conducted in E-Defense....
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Development of reactor building blowout panel closing device for Tokai No.2 power station

At Tokai No. 2 Power Station, a special inspection is conducted in line with the application for approval of extension of operating period. In particular, for reactor pressure vessels, ultrasonic flaw inspection is performed on the base metal part of the trunk which has not been inspected during the conventional in-service inspection. For water supply nozzles, we are conducting eddy current flaw detection inspection for low alloy steel, which is the first in Japan. As a result of these inspections, no defec...
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Reactor pressure vessel inspection for extension of operation period at Tokai No. 2 power station

Tokai No.2 Power Station (Tokai II) has been operated more than 40-years. At 2018,we completed the 40-years Aging Management Technical Evaluation (AMTE), and concluded that most of component and structure would be maintained their integrity by continued existing preservation activities, even assuming the operation period of 60 years. In this paper, we explain several technical matters that were particularly discussed at AMTE, for example, thermal aging for casting stainless steel, neutron irradiation embrit...
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Aging management technical evaluation for Tokai No.2 Power Station