In order to improve the operational reliability of automatic closure system(hereinafter referred to as "flap gates") used at air conditioning openings of buildings as a measure to protect Hamaoka NPP against tsunami, outdoor exposure test of actual equipment and components , And grasped the deterioration tendency. By making use of the exposure test results in maintenance, we were able to set up a reasonable and appropriate maintenance cycle and to enhance the safety of the Hamaoka NPP. ...
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Degradation characteristics of flap gate under outdoor environment

In May 2011, at Hamaoka-5, the main condenser thin tube was damaged and seawater intruded to the reactor facility. It was purified to a level where corrosion did not occur by replacing the intruding water. However a few years later, the leak occurred from the stainless steel welded joint. It is presumed that the cause is that crevice corrosion was caused by the welded part of stainless steel with high corrosion sensitivity, the inflow of chloride ions, and the crud deposits. And in this study, we aim to elu...
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Elucidating the corrosion of the stainless steel welded joint caused by seawater intrusion at Hamaoka-5

In this research, research into the causes of the event of piping micro leakage of Hamaoka Nuclear power plant Unit 5 was carried out .Due to main condenser tube damage in May, 2011, seawater flowed into the reactor and other facilities of Unit 5. After that, piping purification was carried out and kept filled with water. Crevice corro- sion was confirmed at the leakage piping and it was estimated to happen at purification process. The leakage piping would not be cleaned sufficiently in the purification pro...
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Investigation on leakage point of welding part of control rod drive system piping of Hamaoka NPS unit5.

In the process of achieving cold shutdown of Hamaoka Nuclear Power Station Unit 5 on May 14, 2011, sea water flowed into the reactor and other equipment due to main condenser tube leakage. By clean-up operation, chloride ion concentration went below 10 ppm, the target prescribed to prevent crevice corrosion. On Dec, 2015, the component health assessment had summarized by surveys focusing on material corrosion, deposit and residual chloride. Since, each equipment have been under wet or dry lay-up condition. ...
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Cleanup and lay-up around reactor pressure vessel related to sea water intrusion event at Hamaoka Nuclear Power Station Unit 5

Based on the fact that Hamaoka Nuclear Power Station is located in the hypocenter area of the Nankai Trough giant earthquake, we have voluntarily made efforts to improve safety, such as seismic margin improvement work, even before the occurrence of the Tohoku-Pacific Ocean Earthquake. Furthermore, after the Fukushima Daiichi accident, we have voluntarily continued risk reduction activities such as tsunami countermeasures and severe accident countermeasures. This time, we will introduce the outline of the sa...
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Safety measures of Hamaoka Nuclear Power Station

Hamaoka Nuclear Power Plant Units 1 and 2 have been decommissioned since 2009. The decommissioning of the plants are currently in the process of dismantling the facilities around the reactor area as the second stage. We will introduce various decommissioning works being carry out at these plants....
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Hamaoka Nuclear Power Plant Units1 and 2 decommissioning work status

In June 2018, the leakage of gases around the exhaust pipe attached to emergency diesel generator of Hamaoka Nuclear power plant Unit 5 and the breakage of an exhaust pipe expansion joint were found. As a result of investigation, we estimated that the cause of the event were the hit marks on the bellows of the expansion joint and low cycle fatigue caused by usual operation of the generator. It was estimated that the hit marks were made when the expansion joint was installed to the exhaust pipe. This paper s...
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Investigation on breakage of the exhaust pipe expansion joint of diesel generator (B) of Hamaoka NPS unit5

Fact finding survey of actual RPV in decommissioning Hamaoka-1 has been under conducting. All boat samples was already transported to a domestic post irradiation examination facility (NFD). At NFD, irradiated materials were investigated as introduced in the 15th JSM conference. This is the progress report describing new results obtained after the conference....
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Research on reactor pressure vessel in Hamaoka-1 (Part 2) - Material research utilizing decommissioning NPS -

Fact finding survey of actual reactor pressure vessel in decommissioning Hamaoka nuclear power station has been conducted. All boat samples was already transported to a domestic post irradiation examination (PIE) facility. During the PIE, un-irradiated archive materials was also investigated for better understanding of cladding HAZ in base metal, as introduced in the 14th JSM conference. This is the progress report describing some new results obtained after the conference....
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Research on reactor pressure vessel in Hamaoka Unit 1 - Material research utilizing decommissioning NPS -

We began a research about material degradation by using some pieces of concrete and metal taken from Hamaoka Nuclear Power Station (NPS) Unit 1 that is currently being decommissioned. A research project on the aging concrete structures has been conducted since FY2015. This report describes the physical properties such as compressive strength on the aging inner wall concrete....
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Physical Properties on the Aging Concrete of Hamaoka Unit 1 - Material research utilizing decommissioning NPS -