Radiation Levels Surge Outside Two Nuclear Plants in Japan

Some FYI from a friend who works for an environmental remediation company and specializes in the radioactive clean-up. He received this email yesterday from another colleague:

Battle to stabilise earthquake reactors
12 March 2011
UPDATE 8: 1.35 pm GMT

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.

Three of Fukushima Daiichi's six reactors were in operation when yesterday's quake hit, at which point they shut down automatically and commenced removal of residual heat with the help of emergency diesel generators. These suddenly stopped about an hour later, and this has been put down to tsunami flooding by the International Atomic Energy Agency (IAEA).

Fukushima Daiichi

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
Unit 4
- 760 MWe BWR, 1978
- Shut for periodic inspection
Unit 5
- 760 MWe BWR, 1978
- Shut for periodic inspection
Unit 6
- 1067 MWe BWR, 1979
- Shut for periodic inspection

Fukushima Daini
Unit 1
- 1067 MWe BWR, 1982
- Automatically shut down
- Offsite power available
- Water level stable
- Preparations for pressure release
Unit 2
- 1067 MWe BWR, 1984
- Automatically shut down
- Offsite power available
- Water level stable
- Preparations for pressure release
Unit 3
- 1067 MWe BWR, 1985
- Automatically shut down
- Offsite power available
- Water level stable
- Preparations for pressure release
Unit 4
- 1067 MWe BWR, 1987
- Automatically shut down
- Offsite power available
- Water level stable
- Preparations for pressure release

The loss of the diesels led the plant owners Tokyo Electric Power Company (Tepco) to immediately notify the government of a technical emergency situation, which allows officials to take additional precautionary measures.


For many hours the primary focus of work at the site was to connect enough portable power modules to fully replace the diesels and enable the full operation of cooling systems.

Pressure and releases
Without enough power for cooling systems, decay heat from the reactor cores of units 1, 2 and 3 has gradually reduced coolant water levels through evaporation. The consequent increase in pressure in the coolant circuit can be managed via pressure release valves. However, this leads to an increase in pressure within the reactor building containment. Tepco has said that the pressure within the containment of Fukushima Daiichi 1 has reached around 840 kPa, compared to reference levels of 400 kPa.

The company has decided to manage this "for those units that cannot confirm certain levels of water injection" by means of a controlled release of air and water vapour to the atmosphere. Because this water has been through the reactor core, this would inevitably mean a certain release of radiation. The IAEA said this would be filtered to retain radiation within the containment. Tepco has confirmed it was in the process of relieving pressure at unit 1 while preparing to do the same for units 2 and 3

Explosion
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.

Raised temperatures
Meanwhile at adjacent Fukushima Daini, where four reactors have been shut down safely since the earthquake hit, Tepco has notified government of another emergency status.

Unit 1's reactor core isolation cooling system had been operating normally, and this was later supplemented by a separate make-up water condensate system. However, the latter was lost at 5.32am local time when its suppression chamber reached 100ºC. This led Tepco to notify government of another technical emergency situation.

Tepco has announced it has decided to prepare for controlled releases to ease pressure in the containments of all four units at Fukushima Daini.

A three kilometre evacuation is in progress, with residents in a zone out to ten kilometres given notice of potential expansion.

Workers
A seriously injured worker was trapped within Fukushima Daiichi unit 1 in the crane operating console of the exhaust stack and is now confirmed to have died. At Fukushima Daiini unit 3 one worker received a radiation dose of 106 mSv. This is comparable to levels deemed acceptable in emergency situations by the UK Health and Safety Executive, for example.

http://www.world-nuclear.org/info/inf18.html
Nuclear Power Plants and Earthquakes
(updated January 2011)

According to Wikipedia's specs on the Daiichi power plant, Unit 1 was designed to handle "peak ground acceleration of 0.18 g (1.74 m/s2) and a response spectrum based on the 1952 Kern County earthquake." Units 2-5 are the same design; Unit 6 is a newer model, and it's specs aren't listed. I can't find the energy of peak ground acceleration for these most recent earthquakes at the nuclear plant's location (they had a 7.2 on the 9th) to determine if they fall inside of that designed range (it was a strong earthquake that generated the tsunami, but also very deep). Does anyone have that info, or know where to find it? If it's not located in the yellow or lower end of the orange on this map, then it would appear as if it was well outside safe parameters: http://neic.usgs.gov/neis/eq_depot/2011 ... xgp_w.html