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March 12, 2011

Battle to stabilise earthquake reactors - Fukushima Daiichi unit 1

Attention is focused on the Fukushima Daiichi and Daini nuclear power plants as Japan struggles to cope in the aftermath of its worst earthquake in recorded history. An explosion has been seen at the site and seawater is now being injected to the plant

Tepco - Plant Status of Fukushima Daiichi Nuclear Power Station


Press Release (Mar 12,2011)
Plant Status of Fukushima Daiichi Nuclear Power Station (as of 1PM March 12th )


All 6 units of Fukushima Daiichi Nuclear Power Station have been shut down.
Unit 1(Shut down)
- Reactor has been shut down and steam in reactor has been cooled by
isolation condenser, but it is now stopped. Because pressure level in
reactor containment vessel is increasing, following the national
government instruction, we are implementing a measure to reduce the
pressure of the reactor containment vessels in order to fully secure
safety.
Reactor water level is decreasing, we will continue injecting water step
by step.

Unit 2(Shut down)
- Reactor has been shut down and we continue injecting water by Reactor
Core Isolation Cooling System. Current reactor water level is lower than
normal level, but the water level is steady. Following the national
government instruction, we are preparing to implement a measure to reduce
the pressure of the reactor containment vessels in order to fully secure
safety.

Unit 3(Shut down)
- Reactor has been shut down and we continue injecting water by Reactor
Core Isolation Cooling System. Following the national government
instruction, we are preparing to implement a measure to reduce the
pressure of the reactor containment vessels in order to fully secure
safety.

- Currently, we do not believe there is any reactor coolant leakage inside
the reactor containment vessel.






Fukushima Daiichi from World Nuclear News

Unit 1
- 439 MWe BWR, 1971
- Automatically shut down
- Water level decreasing
- Pressure release implemented
- Explosion observed with unknown effect
- Containment believed intact
- Seawater injection has started

Unit 2
- 760 MWe BWR, 1974
- Automatically shut down
- Water level lower but steady
- Preparations for pressure release

Unit 3
- 760 MWe BWR, 1976
- Automatically shut down
- Preparations for pressure release

The Explosion at unit 1

Television cameras trained on the plant captured a dramatic explosion surrounding unit 1 at around 6pm. Amid a visible pressure release and a cloud of dust it was not possible to know the extent of the damage. The external building structure does not act as the containment, which is an airtight engineered boundary within. According to reported comments attributed to chief cabinet secretary Yukio Edano, the containment has not been comprimised.

Monitoring of Fukushima Daiichi 1 had previously shown an increase in radiation levels detected emerging from the plant via routes such as the exhaust stack and the discharge canal. Tepco have said that the amount of radioactive material such as iodine it is detecting have been increasing. The amount of radiation at the site boundary now exceeds a regulatory limit triggering another set of emergency precautions.

To protect the public from potential health effects of radioactive isotopes of iodine that could potentially be released, authorities are preparing to distribute tablets of non-radioactive potassium-iodide. This is quickly taken up by the body and its presence prevents the take-up of iodine should people be exposed to it.

The injection of seawater into the building followed 8.20pm and this will be followed by addition of boric acid, which is used to inhibit nuclear reactions.

Over the last several hours evacuation orders for local residents have been incrementally increased and now cover people living within 20 kilometres of the power plant.

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