Sunday, March 13, 2011

Fukushima Daiichi, Situations at Unit 1, 2 and 3.

From TEPCO's latest press release:
Fukushima Daiichi Nuclear Power Station:
Units 1 to 3: shutdown due to earthquake
Units 4 to 6: outage due to regular inspection
* The national government has instructed evacuation for those local residents within 20km radius of the site periphery.
* The value of radioactive material (iodine, etc) is increasing according to the monitoring car at the site (outside).
* Since the amount of radiation at the boundary of the site exceeds the limits, we decide at 4:17PM, Mar 12 and we have reported and/or noticed the government agencies concerned to apply the clause 1 of the Article 15 of the Radiation Disaster Measure at 5PM, Mar 12. After that, the radiation dose at the monitoring post decreased once. Today, the measured value revamped and the radiation dose measured at site boundary exceeded the limiting value again. As such, at 8:56AM, today, it was determined that a specific incident stipulated in article 15, clause 1 occurred and at 09:10AM, today, notified accordingly.
* In addition, a vertical earthquake hit the site and big explosion has happened near the Unit 1 and smoke breaks out around 3:36PM, Mar 12th.
* Unit 1: We started injection of sea water into the reactor core at 8:20PM, Mar 12 and then boric acid subsequently.
* Unit 2: Reactor has been shut down and Reactor Core Isolation Cooling System has been injecting water to the reactor. Current reactor water level is lower than normal level, but the water level is steady. After fully securing safety, we are preparing to implement a measure to reduce the pressure of the reactor containment vessels under the instruction of the national government.
* Unit 3: High Pressure Coolant Injection System automatically stopped. We endeavored to restart the Reactor Core Isolation Cooling System but failed. Also, we could not confirm the water inflow of Emergency Core Cooling System. As such, we decided at 5.10AM, Mar 12, and we reported and/or noticed the government agencies concerned to apply the clause 1 of the Article 15 of the Radiation Disaster Measure at 5:58AM, Mar 13. In order to fully secure safety, we operated the vent valve to reduce the pressure of the reactor containment vessels (partial release of air containing radioactive materials) and completed the procedure at 8:41AM, Mar 13 (successfully completed at 09:20AM, Mar 13). After that, we began injecting water containing boric acid that absorbs neutron into the reactor by the fire pump from 09:25AM, Mar 13.
* We continue endeavoring to secure the safety that all we can do and monitoring the periphery.

Looking back at the previous press release, they now talk about the failure of one of the cooling systems (unit 3). The borated water quenches any chain reaction so that this water cools the decay heat from the reactor and also stops any potential chain reaction from occurring. Here are some guesses from some folks working in nuclear power plants on what happened for the explosion on top of unit 1 yesterday (i.e. hydrogen or pressure explosion), again those are just guesses.  But as far as I can tell there is no way anybody can say anything about the inside conditions of any of the three cores. In particular, the wording Partial Meltdown seems to be overly used in the media when in fact the fuel rods may have been just damaged. It is indeed a serious situation but there is no need to be hysterical about it mostly because of the containment around the vessel that houses the reactor core. By the way, they seem to have used pure water not sea water in unit 3 showing to me that they seem to very much control that aspect of the process.

When this is over, I'll be buying the book on how the operators went about sustaining a 8.9 earthquake and a tsunami.

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