Breaking: There are [now confirmed] reports of yet another explosion at Unit 4, presumably associated with the fire.
Japan’s Prime Minister gave a press conference at 11:00 a.m. (Tokyo) Tuesday and an official overseeing the nuclear emergencies answered questions about the status of the four units at Fukushima Nuclear Station.
The briefing part revealed there has been an explosion and fire at Unit 4 which, as of the presser, they were still trying to control. [Later reports say it's [now] extinguished.
Unit 4 had not been operating when the quakes hit last week and was supposedly in safe cold shutdown. However, cooling at that reactor is still required for the spent fuel pools, and its absence is a problem that can allow heat buildup from residual radioactive decay. The damage associated with this fire caused a significant radiation leak and apparently an explosion.
Officials suggested that this source, and not solely or necessarily the explosion at Unit 2, may be the source of highly elevated radiation readings at the Station. Because of increased levels, the government evacuated about 800 non-essential personnel from the Fukushima Daiichi Station, leaving only 50 workers to continue with sea water injections at all units.
The Government also directed that the public evacuation radius be set at 20 kilometers, and that between 20 and 30 km, residents remain indoors. Later reports note detecting higher levels of radiation in Tokyo and other cities.
The official emphasized the very high levels of radiation near Unit 4, with the measurement units being expressed in mili-sievert levels instead of micro-sievert levels. Whereas before we had as high as 8,217 micro-sievert/hour, the new readings were more like 300-400 mili-sieverts/hour near Unit 4. The official noted this level is clearly dangerous to humans.
The official said that as of 6:00 a.m. Tuesday, all but 50 workers involved in water injections have been evacuated. Sea water injections are still bein attempted at Units 1, 2, and 3. [earlier reports suggested they only had the fire equipment to deal with one plant at a time.]
Following is a paraphrase of the Q and A with the official overseeing nuclear issues:
Q. How are you sure the pressure vessel has not been damaged?
A. Water injection has been maintained. And pressure has been stabilized; we have to continue those efforts.
Q. How serious is fire at Unit 4?
A. I mentioned it first because it occurred earlier.
Q. Is there damage to part of the containment vessel?
A. There is a high probability that it was. [May be a mistranslation of terms here]
Q. Radiation levels a threat to the public?
A. Very little possibility of harm to public
Q. Status of fire at Unit 4?
A. Still working to extinguish the fire at Unit 4.
Q. Evacuation radius?
A. Out to 20 km = evacuate. Considering out to 30 km; but for now, just stay indoors.
Q. Radiation readings related to damage to Unit 2?
A. Explosion at #4 reactor could have caused that [after explosion?]
Q. What if fire continues?
A. We’re making every effort to put it out. The spent fuel is not going to “catch fire” in general sense, but its heat likely caused the fire. Fire is in building area; but it’s best to extinguish to keep temps down and prevent release of radiation.
Q. Further release from other units?
A. Possible some could have been released. Ask TEPCO. But current high readings are from this fire/explosion at Unit 4, not from the Unit 2.
Q. What is your advice?
A. [Repeats evac and remain indoors] Minimal amounts may spread further, but further away the level is lower, so stay calm.
In another Onadaga plant, the levels will not cause damage to health.
A. For people between 20-30 km range, there are towns that overlap/in beetween. He calls them out. [About 8-10 towns]
Q. Sec. Gen. of IAEA says you asked for experts?
A. Not aware of any Japanese request to IAEA, but after quake, we’ve asked for support from various countries.
Q. Neutron radiation?
A. That was from Unit 3, because of its nature [fuel type]
Q. How long to extinguish Unit 4 fire, given you think it’s source of radiaion?
A. Working on it.
Q. Are you ontinuing to inject water at all units?
A. Yes. Thank you for your questions.