Update #1: TEPCO reactor by reactor status report at Fukushima (PDF file): http://goo.gl/lKwdz
Update #2: New technical analysis here
Update #3: A 2nd explosion (apparently another hydrogen explosion) has occured at Unit #3. Yukio Edano says that water injection at Unit 3 is reported to be continuing, the indications are the containment vessel is still safe. More here:
Another hydrogen explosion has rocked the Fukushima Daiichi nuclear power plant, this time at the third reactor unit. Initial analysis is that the containment structure remains intact.
The blast that occurred at 11.01am today was much larger than the one seen at unit 1 two days ago. An orange flash came before a large column of brown and grey smoke. A large section of the relatively lightweight roof was seen to fly upwards before landing back on other power plant buildings.
Chief cabinet secretary Yukiyo Edamo appeared on television shortly afterwards to identify the blast was a hydrogen explosion. He said contact had been made with the plant manager whose belief is that the containment structure, important to nuclear safety, remains intact. The rationale for that statement, Edamo said, was that water injection operations have continued and pressure readings from the reactor system remained within a comfortable range.
Pressure and radiation readings
Pressure readouts from the period after the explosion were within a relatively normal range: 380 kPa at 11.13 and 360 kPa at 11.55am. These compare with comfortable levels yesterday of 250 kPa, reference levels of 400 kPa, and a high of 840 kPa recorded at unit 1 on 12 March.
Radiation readings on site remained low after the blast, albeit elevated from normal operation. In the service hall the reading was 50 microSieverts per hour. At the entrance to the plant the figure was 20 microSieverts per hour.
At 12:30pm, the radiation dose measured at a monitoring point on the Fukushima Daiichi site indicated a level of 4 microSieverts per hour. However, a subsequent reading at 1:55pm showed a reading of 15 microSieverts per hour but an increase of radioactive material was not confirmed. A monitoring post at the Fukushima Daini plant – some 10 kilometres south of the Fukushima Daiichi plant – indicated no change in the radiation dose there.
Cooling and pressure control
Fukushima Daiichi 3 was yesterday the subject of sustained efforts by engineers working to ensure that adequate cooling water was available for decay heat removal. Seawater was being injected into the reactor vessel and pressure had been relieved to comfortable levels.
A statement from Tepco shortly after the blast said that pressure had risen again to 530 kPa by 6.50am. The company determined this was ‘abnormal’ at 7.44am and declared the matter officially to government. It began to gradually relieve the pressure, and carried out a “tentative evacuation” of the site, until it reached a level of 490 kPa at 9.05am.
From Kyodo News:
Chief Cabinet Secretary Yukio Edano said the plant operator Tokyo Electric Power Co. confirmed that the 11:01 a.m. blast did not damage the container of the No. 3 reactor, allaying concerns that the explosion may have caused a massive release of radioactive substance. TEPCO said three workers, including its employees, were injured by the blast. All of them suffered bruises. ”According to the plant chief’s assessment, the container’s health has been maintained,” Edano told a press conference.
Here are some of the best updates available on the Japanese nuclear power plant situation (14 March 2011), following the massive earthquake and subsequent tsunami. In short, the nuclear reactor situation at Fukushima units #1 and #3 has stabilised with full containment intact (see below), and all other plants in the affected area are in cold shutdown.
This morning I talked to Channel 9′s “Today” program (3 min video — alas MSN don’t allow vid embedding so click on the picture to go to the off-site stream)
An excellent ‘Frequently Asked Questions’ document has been prepared by the Nuclear Energy Institute with 19 questions and answers (download 7-page PDF here). Definitely read this. A further news stream is here: http://resources.nei.org/japan
A very clear and readable statement (see 3 page document here) is also available, from the Federation of Electric Power Companies of Japan. Again, very worthwhile.
World Nuclear News provides a regularly updated commentary: Efforts to manage Fukushima Daiichi 3. The bottom line:
Unit 1: Seawater injection continues and it is thought the reactor core is now sufficiently cool. Safety regulators consider reactor pressure of 353 kPa an indication of a stable condition.
Unit 2: The normal reactor core isolation cooling system is in use. Fuel rods are covered by about 3.8 metres of water.
Unit 3: Operations to relieve pressure in the containment of Fukushima Daiichi 3 have taken place after the failure of a core coolant system. Seawater is being injected to make certain of core cooling. Malfunctions have hampered efforts but there are strong indications of stability.
Reactors 1, 2 and 3 were in operation at Tokyo Electric Power Company’s (Tepco’s) east coast Fukushima Daiichi nuclear power plant when the magnitude 9.0 earthquake struck. Three other reactors were already shut for inspection but all three operating units underwent automatic shutdown as expected. Because plant power and grid power were unavailable during the earthquake, diesel generators started automatically to supply power for decay heat removal.
This situation continued for one hour until the plant was hit by the tsunami wave, which stopped the generators and left the plant in black-out conditions.
The tsunami wave that hit the plant measured at least 7 metres in height, compared to the maximum 6.5 metre case the plant was designed to cope with.
The loss of power meant inevitable rises in temperature within the reactor system as well increases in pressure. Engineers fought for many hours to install mobile power units to replace the diesels and managed to stabilise conditions at units 2 and 3.
However, there was not enough power to provide sufficient coolant to unit 1, which came under greater and greater strain from falling water levels and steady pressure rises. Tepco found it necessary yesterday to vent steam from the reactor containment. Next, the world saw a sharp hydrogen explosion destroy a portion of the reactor building roof. The government ordered the situation brought under control by the injection of seawater to the reactor vessel.
Depleted Cranium reflects on how this situation must be explained to the public: This is Our Generation’s Three Mile Island – Lets Not Screw it Up
Of course, newspapers are already speculating on the implications of these events for nuclear power in places like Australia: Meltdown fears spark ‘turning point for world’ — the closing comments were from me:
Professor Barry Brook, an environmental scientist at the University of Adelaide, said the effect on the Australian debate depended on whether it would be ”argued on a rational basis or an irrational basis”.
A rational debate would acknowledge that Japan’s largest recorded earthquake produced an incident at a 40-year-old reactor that was ranked at a level less than the Three Mile Island emergency, he said. ”I think the nuclear reactors have come through remarkably well.”
Over the coming days and weeks, there will need to be a detailed and clear-headed analysis of exactly what happened (as further information emerges), and the short- and long-term implications. I will endeavour to cover these issues in detail, from many angles, on BraveNewClimate.com