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. ...
英字タイトル:
Cleanup and lay-up around reactor pressure vessel related to sea water intrusion event at Hamaoka Nuclear Power Station Unit 5

Recently, the threat of terrorists is increasing in all of the world. In addition to that, the terrorists are trying to invade to an important facility by not only from land and air but also underwater. So, underwater monitoring system is highly demanded for the monitoring of the costal important facilities such as power plants. Then, NEC suggest Harbor Monitoring Network System for monitoring a terrorist approaching from land, air, and underwater. In this paper, we focus on underwater monitoring system usi...
英字タイトル:
Safety improvement of coastal important facilities using Harbor Monitoring Network System

強度試験に用いる鋼材を原子炉内の限られたスペースで中性子照射させる必要から、小型試験片による試験技術は原子炉圧力容器の監視試験のキー技術であり、継続して開発が続けられてきた。当所で開発と実用化を目指してきた試験技術から、現行の監視試験片の1/8以下の大きさで破壊靭性を評価できる技術と、直径8mm、板厚0.5mmという小型円板でと引張強度特性を評価する技術を紹介する。 ...

A maintenance management suitable to nuclear power plants (NPP) at R&D stage was discussed. Objectives of maintenance management of NPP at R&D stage was first clarified. Next, applicability of codes for maintenance management of commercial NPP to NPP at R&D stage was discussed. Then, requirements and consideration for maintenance management of NPP at R&D stage was proposed. Finally, an example that the proposal was applied to setting maintenance program of sodium-cooled fast reactor was presented. ...
英字タイトル:
Proposal of Maintenance Management of Nuclear Power Plants at R&D Stage by Taking Account of Their Features

A maintenance management suitable to nuclear power plants (NPP) at R&D stage was discussed. Objectives of maintenance management of NPP at R&D stage was first clarified. Next, applicability of codes for maintenance management of commercial NPP to NPP at R&D stage was discussed. Then, requirements and consideration for maintenance management of NPP at R&D stage was proposed. ...
英字タイトル:
Proposal of Maintenance Management of Nuclear Power Plants at R&D Stage by Taking Account of Their Features (1) Basic Requirements

A maintenance management suitable to nuclear power plants (NPP) at R&D stage was discussed. Objectives of maintenance management of NPP at R&D stage were first clarified. Next, applicability of codes for maintenance management of commercial NPP to NPP at R&D stage was discussed. Then, requirements and consideration for maintenance management of NPP at R&D stage was proposed. In this paper, requirements on maintenance program of NPP at R&D stage were clarified and an example that the proposal was applie...
英字タイトル:
Proposal of Maintenance Management of Nuclear Power Plants at R&D Stage by Taking Account of Their Features (2) case study

At the Fukushima Daiichi Nuclear Power Station, it is critical to (1) confirm the presence of fuel debris inside the PCV that could be melted fuel as a result of the hydrogen explosion followed by the accident; and (2) conduct in-depth investigations prior to decommissioning. However, the conditions inside the PCVs were unknown. Under this circumstance, International Research Institute for Nuclear decommissioning (IRID) and Toshiba ESS jointly developed devices that can access to the lower part of a PCV and...
英字タイトル:
Development of Remotely-Operated Devices for Investigation Inside Primary Containment Vessel (PCV) of Fukushima Daiichi Nuclear Power Station Unit 2 and 3 and Survey Results

In the Fukushima Daiichi Nuclear Power Plant unit 1, isolation condenser (IC) should play an important role in core cooling during the station blackout. To evaluate cooling capacity of the IC, two phase flow analyses with the TRAC-BF1 code and experiments simulating the IC were conducted. The analyses for the actual BWR indicated that the decay heat could be removed if the IC worked properly at 18:18. However, our results showed that core uncovery occurred at 17:30, which leaded to hydrogen production f...
英字タイトル:
Study on Evaluation of Cooling Capacity of Isolation Condenser in Fukushima Daiichi Unit 1

Working Group on Application Enhancement of Repair Replacement Technology has been established since September 2015, for the purpose of studying specific measures to create an environment that Japanese utilities can easily make corrective actions such as repair replacement technology applicable to Nuclear Power Plant to improve the safety of their own plants, and meetings have been held five times until the end of April 2016. In this paper, discussions on the WG meetings so far are shown, as well as th...
英字タイトル:
Current Status of WG on Application Enhancement of Repair Replacement Technology

The water level in the fuel zone is an important parameter to conduct properly accident management. In the Fukushima Daiichi Nuclear Power Plant accident, measurement error of the water level occurred, which was caused by evaporation of water in a reference leg. To measure the water level properly, the reference leg connected to the condensing chamber must be filled with water. We focused on the method called backfill to keep the performance of water level gauge during severe accident. Backfill is applied ...
英字タイトル:
Study on keeping performance of water level gauge under the severe accident.