Maintenance/reliability improvement of safety system

Purpose

1. To aim at maintenance and reliability improvement of safety system for maintaining and managing the stable condition of fuel debris.

Current status

1. With respect to the fuel debris, the circulation cooling system has been installed, the measures are also taken to improve reliability, such as installation of multiple of equipment and the stable cooling condition is being maintained. It is important to continuously maintain and manage the stable condition from the safety perspective.


2. It should be noted that maintaining the stable condition until the commencement of fuel debris retrieval affects ensuring safety during the fuel debris retrieval and has continuity.


3. Therefore, maintaining and improving the functions to control and manage the radioactive material release, to cool a reactor, to prevent criticality and to prevent hydrogen explosion, the cooling of fuel debris and the concentration and amount of radioactive materials are being monitored. In addition, it is important for the monitoring to create databases of plant data so as to effectively manage the plant information, such as temperatures of RPV/PCV and injection flow rate of cooling water.