On December 9, the Mainichi Newspaper reported on page 2 of its morning edition that, "If the reactor condenser had started running within an hour after the tsunami struck, the meltdown of the Unit 1 reactor would not have occurred. (JNES analysis)". The facts are as follows.
We are aware of the press release stating that, "Per the results of the JNES analysis of the isolation condenser of Unit 1 of Fukushima Daiichi Nuclear Power Plant, if the reactor condenser had begun running within an hour after the tsunami struck, the meltdown of the Unit 1 reactor would not have occurred."
We think that the relationship between the isolation condenser of Unit 1 and the damage to the reactor is as follows.
The isolation condenser was out of control and lost its function via the automatic isolation interlock operation due to the blackout caused by the tsunami.
Per the result of the Accident Analysis Codes (MAAP) analysis, the water level of the reactor dropped in a short time and the reactor core was exposed (at 5:46 pm, reached the top of the active fuels) due to high decay heat after the reactor shutdown.
Thereafter, the DC power of the isolation condenser (system A) was restored at 6:18pm, the isolation valves (3A valve, 2A valve) were opened, and we confirmed the emission of steam. At 6:25 pm, the 3A valve was closed since the steam generation stopped. The MAAP results reveal that the core was already exposed at that time. Therefore, our evaluations conclude that irrespective of whether the isolation condenser was running or not, the core was damaged as a result.
Concerning isolation condenser operations, as personnel acted in strict accordance with the established protocol set down in the Operation Manual, we do not believe there were any operational oversights.
© Tokyo Electric Power Company Holdings, Inc.
