Fukushima Daiichi Nuclear Power Plant Disaster

The catastrophic sequence of failures effecting the Fukushima Daiichi Nuclear Power Plant is emblematic of the destruction, chaos and impacts of the Japanese and world economy caused by the 9.0 magnitude 2011 Tohoku Earthquake off the north east east coast of Japan's Honshu Island on February 11, 2011. This interactive site explores the unfolding events and impacts of the earthquake, the tsunami it caused, the effects of the earthquake and tsunami on engineered structures with a focus on Japan's nuclear power plants, and the readily apparent management failures to adequately anticipate and manage risk that exacerbated what were already extreme natural events.

In a world that is facing catastrophic climate change from global warming from our ever increasing use of carbon-based fuels, nuclear power has offered one of the few practical alternatives to carbon-based thermal power for the supply of base-load energy. The Fukushima disaster will be magnified many-fold in exacerbated consequences of global warming if fear of nuclear power generated by this disaster prevents the replacement of carbon-fueled base load electricity generation capacity with nuclear power. We hope, that by helping to understand the sources of failure and its consequences in the Fukushima disaster, we will make nuclear power safer and less scary, such that people, politicians, engineers and managers properly understand and mitigate the risks of nuclear power, versus the well known and politically and socially acceptable risks of carbon-based thermal power.

Because the kind of extreme event leading to the Fukushima disaster is so infrequent in nature, most humans will have had no prior experience in their lifetimes with anything comparable. Following from this lack of experience is the failure of people to accept and appreciate that such natural events do happen, and may well happen sometime in their lifetime. However, until such an event happens in a person's lifetime, they are literally "unimaginable". For most people this is probably a good thing. However, for those engineering, building and managing organizations and potentially dangerous structures, this failure of imagination can greatly exacerbate the effects of natural disaster on innocent bystanders. Although still a relatively small catastrophe compared to the overall effects of the tsunami, the engineering and management failures surrounding the Fukushima Daiichi Nuclear Power Plant Disaster, highlight the consequences of these kinds of failures of imagination.

Thus, to make the unimaginable real to the widest possible audience of engineers, managers, politicians who establish "rules of the game"; and educators who introduce engineering and management students with tools of their trades, this site provides intensely graphical details and documentation sourced from the public domain regarding the origin and consequences for human structures and organizations of the Tohoku Earthquake and the tsunami it generated. Where the Fukushima Daiichi Nuclear Power Plant Catastrophe is concerned, we also show that a lack of imagination by both government regulators of the nuclear power industry and the organization that built the particular power plant contributed to catastrophic engineering failures that could have been mitigated. We also consider the potential for other infrequent but known kinds of natural events to cause devastation comparable to or even greater than that caused by the Tohoku Earthquake.

The Fukushima Number 1 ("Dai-ichi") Nuclear Power Plant

Tokyo Electric Power Company's ("TEPCO") Fukushima No. 1 ("Dai-ichi") complex, located on the NE coast of Honshu Island in Japan, is comprised of six early generation boiling water nuclear power reactors (Fig. 1). Table 1 (below) gives specifications for each of the six reactors. A second, somewhat newer, reactor complex Fukushima Number 2 ("Dai-ni") is located 11.7 km south of the Daiichi plant. The original state of the Daiichi plant, the immediate effects of the earthquake and tsunami, and consequences of TEPCO's failures to keep the reactors under control after they shut down automatically immediately following the earthquake are illustrated in the following sequence of graphics.

Many images have been gathered via Google Earth's and other satellite imagery, other remote sensing, and ground based observations all freely available via the World Wide Web. (Google Earth is freely available. For information on downloading and using it, see Obtaining and Using Google Earth
.) Click on a graphic to go to the normally higher resolution original on the Web. Figure captions include links to related information from the source pages on the Web. Where the link points to a time and location mapped in Google Earth (GEarth), once the position has been located you can zoom in or out and navigate in space to examine details, and if GEarth has access to images captured at different times, you may also be able to navigate to earlier and later images in time. For example, as this is written, GEarth imaged the region around the Fukushima plants in 2003, 2004, and 2011 (Feb 12, 13, 14, 16, 17, 18, and 19). Images on the various dates differ in terms of resolution, cloudiness, and lighting angle.

Fig. 1. The Fukushima Dai-ichi ("No. 1") Nuclear Power Plant complex is located in Fukushima Prefecture, north eastern Honshou Island (the "Tohoku" region of Japan. It comprises 6 reactors and associated steam turbines and generators, and a variety of fuel storage, plant safety and maintenance, and administrative facilities. Major features of the site are identified in the following illustrations.

Along with several others on this site, Fig 1, is sourced from Cryptome.org. (See Wikipedia for more information on Cryptome). See LINK for an even higher resolution picture of reactors 3 and 4, sourced from http://media.silive.com/advance/photo/japan-earthquake-7cf6904af34330f6.jpg

Fig. 2. Google Earth's satellite view of the plant complex captured on 25 December 2003. Click the picture to open this location in Google Earth. Note that the plant is in full operation as determined by the plumes of cooling water exhausted from the northeast and southeast corners of the plant. Individual reactor complexes are numbered. Numbers are placed on the turbine/generator halls, and the reactor buildings are the nearly square buildings immediately to the left of the turbine/generator halls. See also Satellite Imaging Corporation's view of the site from 15 November 2009.

Table 1
Specifications of the Fukushima Daiichi Nuclear Reactors a

Reactor #
 1  2  3 b 4
 5 6
 MK 1
MK 1
 MK 1
 MK 1
 Mk 1
Mk 2
Power (MW) 460
 784  784 1,100
Tons U
 69  94 94
No. fuel assys
 400  548  548  548 548
Start construction
 29/09/67  27/05/69
 8/05/72  22/12/71  16/03/73
Start operation
 26/03/71 18/07/74
 12/10/78  18/04/78  24/10/89
Status 11/03/2011
 full power
 full power
 full power
 de-fuelled  shut down
 shut down

Notes: (a) Sourced from Challenges of Tepco / Nuclear Power Generation / Facts & Figures

(b) Reactor was loaded with a mixture of Uranium and Plutonium

GE Mark 1 reactor design

The GE Mark 1 containment design was marketed as being less expensive to build than others, and was adopted by many organizations around the world. Fig 4. Illustrates the general configuration of many of these installations and Fig. 5 illustrates the steel work of the primary containment and suppression ring. Although all GE Mk 1 reactors had the same style of containment, they varied in size and details of their layouts, as in the differences between Fukushima Daiichi 1 versus 2 through 5. Reactor 6 followed an improved design. Several things should be noticed about this design. (1) The torus of the suppression chamber sits outside of the primary containment vessel and provides major penetrations through what is supposed to be a last resort able to contain products of meltdowns. (2) The secondary containment structure (i.e., the strong reinforced concrete building containing the primary containment and the suppression chamber) does not extend beyond the floor of the refueling deck.  (3) This refueling deck includes the (a) fresh fuel pond, (b) spent fuel pond and (c) the gantry cranes required to lift the concrete cap blocks, the top of the primary containment vessel, and the top of the reactor pressure vessel that must be removed to allow refueling to be done. This deck is only enclosed by a fairly lightweight industrial shed.

Spent fuel rods are highly radioactive and release substantial heat from decay of unstable fission products, and must be aggressively  cooled by continuous immersion in water until the rate of decay declines to a level that allows the rods to be transferred to dry storage.

Fig. 3. Main structures in the GE Mark I reactor design. The reactor vessel contains the uranium core and control rods that control the rate of nuclear fission in the core. The flask shaped steel containment structure is intended to prevent radioactive fuel and fission products from escaping to the environment, no matter what. The steel containment is immediately surrounded by a thick reinforced concrete shell that serves to reinforce the steel containment structure. Together these provide the primary containment. The space between the cylinder of the reactor vessel is normally dry and is called the drywell. The base of the primary containment is surrounded by a large steel doughnut-shaped structure called the suppression chamber partly filled with water. In the case of abnormal operation venting excessive steam pressure from the reactor vessel into the drywell, the large vent lines conduct pressurized steam into the suppression chamber where contact with the cold water condenses the steam to reduce pressure in the containment vessel.

Fig. 4. Nearly completed steel work of the primary containment of a GE Mark I nuclear reactor under construction. The size of the structure is indicated by the workers in the foreground. See Will Davis' real time blog, Atomic Power Review for more details on the evolving disaster. Davis was a US Navy Reactor Operator; qualified Reactor Operator on S8G and S5W submarine reactor plants and provides the thinking of a qualified nuclear power plant operator as he analyses and interprets a goldmine of near real-time mountain of raw data issued by Tepco and other Japanese authorities.

Recommended reading

Challenges of TEPCO:

Environmental Sustainability Report See especially:

Energy and Resources: See especially
Tepco News: Presentations & Handouts
Corporate Information: See especially
  • Corporate Ethics and Compliance
  • Business Risk
  • Annual Report 2007 (p. 7 Group Management Challenges and Policies for the Future; pp. 10-11 Interview with President Tsunehisa Katsumata - Q&A on data tampering; p. 12 Preventing the Recurrence of Data Tampering at Power Generation Facilities; p. 13 Corporate Ethics and Compliance)
  • Annual Report 2008 (Snapshot p. 2 para 2 on shutdown of TEPCO's largest nuclear power plant Kashiwazaki-Kariwa due to the July 2007 Niigatakan Chuetsu-Oki earthquake; p. 3 Consolidated Financials - note major loss in 2007 due to shutdown; pp. 4 - 5 To Our Shareholders and Investors - discusses earthquake effects & way ahead; pp. 7 - 9 Interview with President discussing earthquake issues; pp. 14-17 Kashiwazaki-Kariwa Nuclear Power Station Restoration Initiatives; p. 18 - 29 Management Challenges and Solutions)
  • Annual Report 2009 (Snapshot see continuing effects of Kashiwazaki-Kariwa shutdown due to the July 2007 Niigatakan Chuetsu-Oki earthquake; pp. 5 -  12 An Interview with President Masataka Shimizu - after 2 years only 1 of 7 power units at Kashiwazaki-Kariwa back in commercial operation

Effects of the 2011 Tohoku Earthquake and Tsunami on Fukushima Daiichi

At 2:46 PM (Japan time) a magnitude 9.0 earthquake struck off the north east coast of Honshu Island, Japan. This is tied to be the third strongest earthquake in the world since 1900. Although unusually strong and not predicted by Japanese seismologists, the mechanism of the earthquake is very well understood and typical of those that can occur in plate tectonic subduction zones associated with seafloor trenches along coasts such as those off Washington State in the US, the Aleutian Islands, Japan, Indonesia, and the South American west coast (see the EarthquakeData page in this site or Tohoku, Japan M9.0 Educational Slides (PPT version) for details of this earthquake). Apparently any of these subduction zones have the potential to generate magnitude 9 and larger earthquakes.

As a result of the earthquake the Oshika Peninsula near Sendai moved 5.3 m to the ESE and 1.2 m down, and the Fukushima coast near the reactors moved about 2.1 m to the E and 0.5 m down (see Attachment 1 and Attachment 2 to press release 19/03/2011, According to seafloor measurements of the Japanese Coastguard Geospatial Information Authority of Japan. (Note: for Japanese language sources such as these press releases, use Google as your browser search engine and set it to translate automatically. Although certainly not idiomatic, the translations are normally intelligible).
However, based on measurements of established sea-floor markers by the Japan Coast Guard (translation w/o graphics), the earthquake moved the sea floor above the epicenter 24 meters to the ESE and lifted it by 3 m, displacing several km2 of seawater, to create the most extreme tsunami to hit Japan in more than a century.

Fig. 5. Fukushima Daiichi reactors 1-4 on 12/03/2011. Tsunami effects on the power plant are detailed on Tsunami Damage to Power Plants.

Because of Japan's long experience with earthquakes, outside of Sendai (close to the epicenter and built on alluvial soils, the earthquake caused few fatalities and by comparison to the ensuing tsunami, little structural damage. The reactors were subjected to shaking from the earthquake calculated to be between 0.75 to 0.80 G (Table 2). Fig. 5 taken prior to the explosion of the reactor 1 building, shows no obvious sign of structural damage to the facility from the earthquake, although power from the national grid needed to power emergency cooling was lost. In any event, testifying to their robustness against seismic damage, three operating reactors at Daiichi and four at Daini executed their emergency shutdown (SCRAM) normally, and the emergency diesel generators replacing the mains power needed to drive emergency cooling functions started normally.

Damage to the Reactors

Fig. 6. State of the Daiichi reactors 1 - 4 on 20 March 2011 seen in an oblique view from the east as they continue to spew radioactive materials into the environment. Note: all figures can be expanded by clicking on them and using the zoom function in your browser to compare details down to resolutions of less than a meter.

According to Tepco, following the earthquake, both plants were struck by several tsunami waves, the first arriving at Daiichi at 3:27 PM - 41 minutes after the earthquake. (See Tsunami Damage to Power Plants.) Based on waterlines seen on buildings, the entire building platform (10 m above sea level) was inundated to 4 to 5 m above ground level. Probably breaking waves destroyed critical equipment in the seawater cooling system located on the shore side of the plant and flooded the turbine/generator halls, including the emergency diesel generators. Irrecoverable loss of back-up electrical power led to a cascading sequence of failures leading to disasters that evolved to produce the next worst nuclear catastrophe to the explosion of the Russian Chernobyl reactor on 16 April 1986, as we explore in more depth (see page for The Unfolding Nuclear Disaster)

The loss of electrical power to emergency cooling and control and monitoring systems led to overheating and probable partial core meltdowns of the just shut down reactors 1 to 3.
Oxidizing zirconium cladding on overheated fuel rods robbed oxygen from steam to release hydrogen gas. Because of dangerously high steam pressures in the primary containment and suppression chambers steam, radioactive gas, and hydrogen had to be vented into reactor buildings to prevent bursting of the containment.

As shown in the video below, on 12 March, hydrogen released into the reactor building detonated, producing a visible shock wave and shattering the building above the reactor fueling floor and substantially damaging buildings across the road behind the reactor building (see Fig. 6).

Detonation of reactor 1 building.

Hydrogen in building 3 then exploded on 14 march as shown in the next video. Substantial building components can be seen falling out of the explosion cloud that probably accounts for the large hole in reactor 3's turbine/generator hall and buildings across the road behind the reactor (see Fig. 6).

Explosion of Reactor 3 Building

To allow maintenance to be done within reactor 4's primary containment, all 94 tons of its fuel had been transferred from the reactor vessel into the adjacent spent fuel cooling pond (see Fig. 3, left column), adding this inventory to spent fuel already there. Fuel in the cooling pond overheated and released enough hydrogen to cause an explosion of the reactor building comparable to those affecting buildings 1 and 3. In this scenario it seems that the exposed fuel may have also have partially melted and burned.

Reactor 2 exploded internally 6:14 am on 15 March 2011:

The explosion of reactor 1 had apparently perforated the reactor 2 building, allowing hydrogen gas released into the building to disperse before rising to an explosive concentration. However, According to Tepco water level in the reactor 2 pressure vessel apparently fell enough to leave the fuel exposed for a while. Then, a
t 6:14 am on 15 March, an explosion was heard inside the building, that was followed by the release of radioactive vapors requiring evacuation. The suspicion is that there was a hydrogen explosion in the primary containment or suppression chamber in the building basement (see Fig. 4, left column), causing a breach of containment.

Fig. 6 (above) taken on 20 march shows the states of reactor buildings 1 to 4 subsequent to their respective explosions. Steam can be seen rising into the air from reactors 2, 3, and 4. Reactor 1 (the smallest of the 6 Daiichi reactors) seems passive. Reactor 2 may have ruptured its containment or suppression torus (directly connected to the containment) and is spewing steam from a hole in the side of the building made by operators to allow hydrogen gas to dissipate. Reactor 3, that was burning a mixed plutonium and uranium fuel, is steaming vigorously, and the cooling pond of Reactor 4 containing a complement of highly radioactive spent fuel together with the full 94 ton load of active fuel recently removed from the core is also steaming visibly - after having been on fire.

GeoEye provides a sliding comparison of satellite views of the four reactors on 15 November 2009 vs
17 March 2011.

Table 2
Seismic Impact on Fukushima Daiichi Reactors

Source: Tepco Press Release (1 April 2011)
Calculated maximum acceleration for each reactor base along 3D vector:
1: 691; 2: 718; 3: 638; 4: 470; 5: 680; 6: 588
Calculated maximum acceleration in each building along the 3D vector:
1: 804; 2: 750; 3: 761; 4: 759; 5: 769; 6: 755
Scram thresholds for each of the reactors are 135 gal horizontal and 100 gal vertical

Issues relating to knowledge, risks and management

Subsidiary pages on this site explore circumstances and failures that turned a devastating earthquake and tsunami into what is already the second worst nuclear disaster the world has suffered since the nuclear bombings that ended the Second World War.