Press Conference by the Chief Cabinet Secretary

JAPANESE

CHIEF CABINET SECRETARY EDANO I will now announce some newly received information on the Unit 3 reactor at the Fukushima Daiichi Nuclear Power Station. Note that this information does not require any new steps to be taken with regard to evacuation; there is no change to the evacuation conditions already announced. I therefore ask that you act calmly in response to my remarks.

First, with respect to the Unit 3 reactor, as the water levels had dropped in the pressure vessel, at precisely 09:05 a safety valve was opened to reduce the pressure in the vessel. At 09:08 injection of pure water into the vessel began. As a result the water levels rose, allowing the cooling of the reactor core.

After that, there was mechanical trouble with the pump used to inject pure water. Swift steps were taken to switch to sea water, which was then injected into the reactor core. In the beginning of this operation there was instability in the water injection, as a result of which the water level in the reactor vessel fell considerably. In response to this, personnel worked hard to ascertain all details regarding the seawater injection operation, and the water level began once again to rise stably.

Let me repeat this. At one point the water injection situation grew unstable, and the water level dropped. For this reason, the reactor core was no longer submerged at one point. Personnel strove to confirm the situation and took steps in response, and the water level began rising once again. During this period, the reactor core was insufficiently cooled, and projections are that a large amount of hydrogen was created in the reactor chamber. There is a possibility that this hydrogen pooled at the top of the reactor structure.

To repeat: there is a possibility that hydrogen had collected at the top of the reactor structure, or the outermost portions of the structure. For this reason, the chance has arisen that the Unit 3 reactor could see a hydrogen explosion like that seen yesterday in the Unit 1 reactor structure. I wanted to report this to you as soon as possible.

In terms of the ongoing monitoring of radioactivity levels, the latest situation is as follows. Figures had remained stable at approximately 50μSv since around 10:00 this morning, but from around 13:44 levels began to rise, and at 13:52 a reading of 1,557.5μSv was observed. However, according to the latest data handed to me immediately before I came here now, as of 14:42 the level had decreased to 184.1μSv.

Consequently, the highest reading that has been detected was 1,557.5μSv. To put this in perspective, the amount of radiation received during a single medical stomach X-ray examination is 600μSv. Even at the highest level of radiation detected, therefore, a person in the location for an hour would have been exposed to 1,557μSv of radiation?slightly less than the equivalent of three stomach X-rays. This figure has already dropped to 184.1μSv. Incidentally, the equivalent figure for a round-trip flight from Tokyo to New York is around 200μSv.

This is the situation as it stands. The possibility cannot be ruled out that hydrogen is being produced and is collecting at the top of the reactor structure. But even in the event that another explosion like yesterday’s does occur, then?just as was the case yesterday?this will not result in any problem within the reactor itself or the containment vessel. Even if an explosion does occur, it will be limited to the area outside the reactor itself, and the structure of reactor and the containment vessel are designed to withstand an impact on that level.

Furthermore, even if an explosion or similar event does occur, because the levels of radiation in the nearby area are as I have indicated, we do not believe that this would cause a situation that would put the health of evacuees in the vicinity at risk. I am releasing this information immediately because of the concerns we have raised about a possible explosion or similar event, and because it has become clear that this possibility cannot be ruled out.