The structural integrity of reactor pressure vessels (RPVs) is an important issue in the field of nuclear power plants. The RPV contains a reactor core, which is impossible to substitute. The pressurized thermal shock (PTS) loading is a critical issue in assessing the safety of RPV. The most severe situation takes places during cold water injection in the cold legs when the emergency core cooling system (ECCS) is operated due to LOCA. Under these circumstances, the PTS loading may lead the RPV to brittle fr...
英字タイトル:
3D-CFD and FEM Based Deterministic PTS Analysis for Optimizing RPV Maintenance Strategy

The structural integrity of a reactor pressure vessel (RPV) is significant for nuclear plant safety. In assessing the integrity of the RPV, one of the most severe situations to be considered is pressurized thermal shock (PTS) during emergency water cooling. Many efforts have been made to understand this PTS, and these efforts assumed symmetric reactor cooling injection. However, once extreme circumstances occur, such as a major earthquake, some of the cooling injections will fail. This failure makes symmetr...
英字タイトル:
Pressurized Thermal Shock Analysis of a Reactor Pressure Vessel for Optimizing the Maintenance Strategy: Effect of Asymmetric Reactor Cooling

Reactor pressure vessel (RPV) steels are subjected to neutron irradiation that can lead to loss of fracture toughness. One of the critical issues for RPV structural integrity is related to the pressurized thermal shock (PTS) event. Risk assessment is important for safety evaluation and maintenance planning of a nuclear power plant. In this study, a new method was developed to assess a failure risk of RPV at PTS event for the risk-based maintenance. The failure risk was caused by fluctuations of stress...
英字タイトル:
Risk-based Optimization of Reactor Pressure Vessel Maintenance

The structural integrity of a reactor pressure vessel (RPV) is important part of nuclear power plant safety. Pressurized thermal shock (PTS) takes place when the emergency core cooling system (ECCS) is operated and the coolant water is injected into the RPV due to a loss-of-coolant accident (LOCA). With the neutron irradiation, PTS loading may lead a RPV to fracture. In the present study, optimization of RPV maintenance is considered, where two different attempts are made to investigate the RPV integri...
英字タイトル:
From the Viewpoint of Maintenance, the Probabilistic Integrity Evaluation of Reactor Pressure Vessel

In Japan, the government decided that nuclear power was used as one of the energy sources for base load energy. Nuclear power plants are required more safety. The plant safety have kept since the start of operation due to the maintenance. Since the maintenance plan should be continued improving, there is still issues for improvement in the plan. In this study, we systematize the methods of the plant maintenance. We review the maintenance plan of reactor pressure vessel and fuel cladding tube and indic...
英字タイトル:
Advanced maintenance methodology was developed for the keeping integrity of reactor pressure vessel

Reactor pressure vessel (RPV) steels are subjected to neutron irradiation that can lead to loss of fracture toughness. One of the critical issues for RPV structural integrity is related to the pressurized thermal shock (PTS) event. Risk assessment is important for safety evaluation and maintenance planning of a nuclear power plant. In this study, a risk assessment method of failure of reactor pressure vessel at PTS event was developed for the risk- based maintenance. The failure risk was caused by fluctua...
英字タイトル:
Reduce the risks associated with irradiation embrittlement of RPV steels: Approach from simulation of microstructural change in steels during irradiation

The prediction of the initiation and propagetion of irradiation-assisted stress corrosion cracking is one of the issues for aging countermeasures in nuclear power plants, and it is desirable to improve the accuracy of the prediction. In recent years, theoretical calculations have shown that irradiation defects introduced by neutron irradiation generate internal stress. Therefore, in this research, we calculate the increase of internal stress using the molecular dynamics method when irradiation defects are f...
英字タイトル:
Influence of internal stress by irradiation defect formation on irradiation assisted stress corrosion cracking