Discussion Thread – Japanese nuclear reactors and the 11 March 2011 earthquake « BraveNewClimate: Information on how this started that I had not seen before, from http://www.greenaction-japan.org/modules/wordpress1/index.php?p=2. This explanatory piece arrived at 17:55 from Takeshi Sakagami:
Fukushima Daiichi Nuclear Power Station Unit 2 lost its cooling system at 13:26pm.
Unit 2 was initially expected to have a possible core meltdown earlier than Units 1 and 3. Estimating by the release of information from the Prime Minister of Japan and his Cabinet, as well as news media coverage, the tsunami hit Fukushima Daiichi Nuclear Power Station 50 minutes after the earthquake at 15:40 on the 11th, causing the emergency diesel generators to stop functioning. The Reactor Core Isolation Cooling pump of Unit 2, however, activated its water injection system the moment the reactor automatically shutdown.
A problem occurred at 20:30 when the M/C (Main Switchboard) was submerged underwater. This prevented proper monitoring of pump operations and the reactor’s water levels. The situation had to be managed without proper information from the site.
As a result, at 20:50, Fukushima Prefecture released an evacuation order for those living within 2km of the reactor. The government also released an evacuation order at 21:23 for those living within 3km and a stay-home order for those within 10km of the reactor. The government’s orders were released following prefectural correspondence.
TEPCO and NISA (Nuclear and Industrial Safety Agency) made two predictions for pump malfunctions at 21:00 and 22:00. The prediction for 22:00 had fuel exposure at 22:50, meltdown at 24:50, and a reactor containment “bent” (intentional release of pressure) at 27:20.
At 21:54, water levels were identified as L2(low-low) using temporary power. However, since this temporary power lasted only a short time, there were measures to secure an electric power supply through a power source car. This trial failed, as they could not connect to the source.
The predicted time for meltdown and reactor containment vessel venting (outer air release) passed without successful power connection.
However, the Reactor Core Isolation Cooling pump was operating. This information was discovered 13min after the predicted time for a reactor containment vessel bent. Water injection continued.
While this was happening, the Unit 1 situation got worse, as its pump was not operating. Problems occurred in Unit 1, followed by Unit 3.
Unit 2’s current state of problems include deterioration of the Reactor Core Isolation Cooling pump function, rising pressure in the reactor, and a lowered water level. NISA stated they would try recovering pump functions by lowering pressure through a reactor containment vessel venting (releasing radioactive inner air to the outside). Sea water was used so as to keep as much water as possible in the reactor containment vessel’s suppression pool.