11:56pm EDT:
From NEI:
At 11:01 pm EDT, Tokyo Electric Power Co. confirmed that an explosion occurred at Fukushima Daiichi Unit 3. The reactor's building wall and ceiling were blown off. TEPCO officials said it was likely a hydrogen explosion as occurred at Unit 1 Friday, but did not have enough information to confirm this.
Official Release from TEPCO:
White smoke around the Fukushima Daiichi Nuclear Power Station Unit 3
At approximately 11:01am, an explosive sound followed by white smoke occurred at the reactor building of the Unit 3. It was believed to be a hydrogen explosion.
According to the parameter, it is estimated that the reactor containment vessel remains intact. However, the status of the plant and the impact of radioactive materials to the outside environment are presently under investigation.
Some workers have sustained injuries. Ambulances are on their way to care for them.
TEPCO continues to take all measures to restore the safety and security of the site and are monitoring the site's immediate surroundings.
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Latest Update from TEPCO:
At approximately 11:01am, an explosive sound followed by white smoke occurred at the reactor building of the Unit 3. It was believed to be a hydrogen explosion.
According to the parameter, it is estimated that the reactor containment vessel remains intact.
However, the status of the plant and the impact of radioactive materials to the outside environment are presently under investigation. (previously announced)
As of 12:00 am, 4 TEPCO employees and 2 workers of related companies have sustained injuries (all of them are conscious) and ambulances are on their way to care for them.
As of 11:44 am, the measured value of radiation dose near MP6 is 20μSv/h (2.1 mrem/h) and the radiation level remains stable.
TEPCO continues to take all measures to restore the safety and security of the site and are monitoring the site's immediate surroundings.
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At 2:46PM on March 11th 2011, the turbines and reactors of Fukushima Daiichi Nuclear Power Station Unit 1 (Boiling Water Reactor, rated output 460 Megawatts) and Units 2 and 3 (Boiling Water Reactor, Rated Output 784 Megawatts) that had been operating at rated power automatically shutdown due to the Tohoku-Chihou-Taiheiyou-Oki Earthquake.
(previously announced)
In response, water injection into Unit 2's reactor were being carried out by the Reactor Core Isolation Cooling System. However, as the Reactor Core Isolation Cooling System failed today, it was determined that a specific incident (failure of reactor cooling function) stipulated in article 15, clause 1 has occurred at 1:25 pm today.To refresh your memory on what Article 10 and Article 15 say:
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Article 10
(1) When a nuclear emergency preparedness manager has been notified that a radiation dose above the limit specified by a Cabinet Order has been detected, pursuant to the provisions of a Cabinet Order, near the border of an area w...here the nuclear site is located or has discovered such fact for him/herself, he/she shall, pursuant to the provisions of an ordinance of the competent ministry and the nuclear operator emergency action plan, immediately notify the competent minister, the competent prefectural governor, the competent mayor of a municipality and the related neighboring prefectural governors (in the case of the occurrence of an event pertaining to transport outside the nuclear site, the competent minister, and a prefectural governor and the mayor of a municipality who have jurisdiction over the place where said event has occurred) to that effect. In this case, the competent prefectural governor and the related neighboring prefectural governors shall notify the mayors of related surrounding municipalities to that effect.
Article 15
(1) In the case of falling under any of the following items, the competent minister shall, when he/she finds that a nuclear emergency situation has occurred, immediately report necessary information concerning the situation to the Prime Minister, and submit a draft of a public notice under the provisions of the next paragraph and a draft of an instruction under the provisions of paragraph 3 to the Prime Minister:
(i) where the detected radiation dose pertaining to a notification which the competent minister has received pursuant to the provisions of the first sentence of Article 10, paragraph 1 or the radiation dose detected at a radiation measurement facility and by a measuring method, both of which are specified by a Cabinet Order, exceeds the radiation dose specified by a Cabinet Order as the condition of an abnormal level of a radiation dose;
(ii) in addition to what is listed in the preceding item, where an event specified by a Cabinet Order as an event that indicates the occurrence of a nuclear emergency situation has occurred. (i) where the detected radiation dose pertaining to a notification which the competent minister has received pursuant to the provisions of the first sentence of Article 10, paragraph 1 or the radiation dose detected at a radiation measurement facility and by a measuring method, both of which are specified by a Cabinet Order, exceeds the radiation dose specified by a Cabinet Order as the condition of an abnormal level of a radiation dose; (ii) in addition to what is listed in the preceding item, where an event specified by a Cabinet Order as an event that indicates the occurrence of a nuclear emergency situation has occurred.
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Cyrus,
ReplyDeleteCan you provide some context for this 2nd explosion? What led up to it, was it expected, how do they proceed now, etc?
Jenny: My understanding was that this was similar to what happened at Unit 1. Basically, as the cladding on the fuel got very hot, water interacts with zirconium to produce hydrogen. This hydrogen built up in the facility.
ReplyDeleteI believe they were hoping to avert this buildup in Unit 3, as they had less problems with cooling Unit 3 (they did not lose diesel power, and began filling with seawater immediately when emergency coolant injection failed). However, this appears to be like Unit 1 in that it has not damaged the "primary" containment, but rather the outer part of the building containing equipment such as cranes, etc.
Cyrus informs me that Units 2 and 3 did in fact lose diesel as well.
ReplyDeleteHowever, my understanding is still that they had experienced fewer problems maintaining coolant levels in Unit 3 than in Unit 1, and had vented earlier in the process - thus, the expectation of a similar hydrogen explosion at Unit 3 had been diminished.
Jenny, check one of my earlier posts that talks about zirconium hydriding and the explosion seen at unit 1.
ReplyDeleteAll I can say is that High Pressure Core Injection that was being powered by other means than the primary diesel engines stopped. Water level likely began to lower and as a result they started pumping sea water in. Right now, it seems unit 3 has similarly repeated the steps of unit 1 without any significant radiation release when venting steam from containment.
As long as there is water covering the core, salty or otherwise, the reactor is 'happy'.
There are more unsubstantiated claims about unit 2 right now. More on that later in the day.