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Friday, December 30, 2011

Tepco 東京電力 and the Toad 蟾蜍 : Neuroethological Reflections on the Failure of A Human Enterprise


“During the week from March 11, I thought several times that I would die.”Director of the Fukushima Dai-ichi Nuclear Power StationMasao Yoshidain his interview with Asahi Shimbun published online Nov. 13, 2011 under the headline "Nuke plant director: 'I thought several times that I would die.'"
“It was a crucial moment when I wasn't sure whether Japan could continue to function as a state.”Prime Minister of Japan His Excellency Naoto Kan published online in The Japan Times under the headline "Tokyo faced evacuation scenario: Kan" published online Sep. 19, 2011.
Looking back on 2011, the year reminded us ever more strongly of our limited power of comprehending risk. The two statements above epitomize the most consequential technological failure of 2011.

The islands of Japan are home to a variety of toads. The video below shows a large specimen of Bufo japonicus formosus or アズマ - 比企ガエル in Japanese. I suppose the people of Japan are well acquainted with this creature.


Toads are not appreciated enough. Important lessons can be learned from the simple behaviors these creatures afford. Neuroethology is a science that examines the nerve cell mechanisms that govern animal behavior. In my post with the title "Prof. Ewert's Toad" published online Dec. 21, 2011, I describe research of the German neuroethologist Jörg-Peter Ewert and his colleagues on the prey catching and predator fleeing of toads.

Image Processing in the Visual System of the Common Toad - Behavior, Brain Function, Artificial Neuronal Net (IWF No. C 1805, 1993) by Prof. Dr. Jörg-Peter Ewert, University of Kassel, Germany, in collaboration with IWF, Knowledge and Media, Göttingen, Germany (courtesy Prof. Ewert).

Prof. Ewert and his colleagues were able to dissect the toads' catching and flight into components of sensory perception and action. The investigators identified nerve cells in the toad's brain crucial to these behaviors. Moreover, they could develop computer models of artificial nerve cell networks emulating the toad's identification of prey or foe and the subsequent decision to attack or retreat. In short, the components of this network can be divided into excitatory nerve cells compelling the toad into action and inhibitory nerve cells that curb one mode of response, that is attack, in favor of the other, that is retreat. Prof. Ewert used these insights to develop software, guiding industrial robots with pattern recognition.

I have been cradling Professor Ewert's fascinating observations in my mind since the beginning of this year. Last March 11, the greatest nuclear reactor accident since Chernobyl in 1986 began to unfold at Fukushima Dai-ichi Nuclear Power Station in the wake of the Tohoku-oki Earthquake and Tsunami.

Fukushima Dai-ichi Nuclear Power Station before Mar. 11, 2011. Reactor units 1(right) - 4 (left) are seen in the foreground, units 5 and 6 are further in background (top left) (courtesy cryptome.org)
The fuel of three nuclear reactors melted down after the loss of coolant, a situation each should have incurred only once in 10,000 years or less, according to probabilistic risk assessment.

Fukushima Dai-ichi Nuclear Power Station after hydrogen explosions in the week after the Mar. 11, 2011, earthquake and tsunami. The explosions devastated the buildings of Units 1(right), 3 and 4. Unit 4 was not operating. The reactor incurred no fuel meltdown. By contrast, the fuel in units 1, 2 and 3 melted down and highly radioactive matter was released in amounts rivaled only by those released after the Chernobyl reactor accident (courtesy cryptome.org)
The meltdowns produced devastating hydrogen explosions that radioactively contaminated land, sea, and air to not yet fully comprehended extent. According to the report of the Japanese government to the International Atomic Energy Agency (page V-9) with the title "Report of Japanese Government to IAEA Ministerial Conference on Nuclear Safety - Accident at TEPCO's Fukushima Nuclear Power Stations (Jun.7, 2011)", about 78,200 residents in the immediate vicinity of the power station were evacuated and have only been permitted to return home for a few hours on occasion. A Japan Times article with the title "Tokyo faced evacuation scenario: Kan" published online on Sep. 19, 2011, reported from a recent interview with the Prime Minister of Japan at the time, Naoto Kan, that His Excellency contemplated the need to evacuate 20 million people from the greater Tokyo area at the height of the reactor crisis. He judged in the interview, “it was a crucial moment when I wasn't sure whether Japan could continue to function as a state.” No other statement could highlight the gravity of that emergency and the need of human organizations to perform adequately in extreme situations.

In the nine months that have passed since the accident, the operator of the Fukushima Dai-ichi Nuclear Power Station Tokyo Electric Power Company, has accomplished stable cooling of the still hot, molten mass of fuel and debris inside the highly compromised reactor buildings. The Japanese government is confronted with a massive environmental clean-up of the radioactive contamination. The challenges involved are unprecedented and daunting. The long-term effects on public health are unknown. Billions of yen will have to be spent to mitigate the damage.

Before this accident, nuclear power generation was considered safe in Japan. How was it possible that the most unthinkable scenario could happen three times in a row? How could the risk of nuclear power generation be that miscalculated?

Why we fail in our risk assessment has preoccupied generations of scholars. Charles Perrow's remarkable book with the title "Normal Accidents: Living with High-Risk Technologies" is still pertinent today. Perhaps, Professor Ewert's insights in the neuroethology of toads may contribute helpful insights.

Our brain takes decisions not unlike the toad's brain. In an area of cerebral cortex known as supplementary motor area for example, excitatory and inhibitory nerve cell inputs weigh in to promote or avert action (Jun and others, 2010; Lo and others, 2009).


Mandelbrot set in html5 (courtesy: Kostas Symeonidis, atopon.org).

Similar to a reverse Mandelbrot set, the fashion in which the nerve cells in our brain interact determines our behavior, which determines how we interact with each other, which determines the structure of human organizations.

Just as the brain consists of networks of nerve cells, human organizations consist of networks of people. Therefore, our mind cannot help, but act adhering to the brain's principles on the next higher level, that is inter-personal social interactions.

Each human enterprise comprises of members who wish to press forward with a promising idea, and members who demand moderation. In as much as the toad's brain, our brain balances cost against benefit. Factions within our organizations constantly struggle with each other over reward-versus-risk estimates. As long as checks and balances are built into our enterprises, we may succeed. By contrast, if one faction dominates the decision making process, either nothing can be achieved, or reckless risk-taking prevails. Through examination of small nerve cell assemblies in the brain, we may therefore attain an improved understanding on how human organizations must function to be successful.

The Fukushima reactor meltdowns represent an example that the unthinkable can happen. The presumption that the reactor design implemented at Fukushima was safe to withstand any fathomable seismic impact had dominated the views of the experts in the field since the inception of the commercial use of nuclear power. Japanese experts now readily acknowledge that the nonchalant attitude that has dominated the nuclear power industry in their country and its governmental regulatory body, the Nuclear and Industrial Safety Agency, (NISA), led to grave underestimations of risk for nuclear power reactors in earthquake and tsunami prone regions (NHKWorld News report with the title "Nuclear experts rethink their future" published online Sep. 20, 2011). Hierarchical report structures steeped in age-old traditions that permeate public and private endeavors like the Amakudari culture of Japan favor top-down instruction, vulnerable to perpetuate flaws in assumption.

In art, music and social relations, Japanese cherish harmony perhaps more than other cultures. Acclaimed medieval warriors like Miyamoto Musashi are equally known for their accomplished works of art, striving for harmony. Yet, like the nerve cells in our brain, our minds struggle every day with conflicting goals and ideas. Shinmen Mushashi represents an excellent example of this antagonism contained in the life of one person. This struggle must be allowed room for consensus to achieve the best possible outcome.

Nerve cell networks have evolved over eons, continuously improving our brain's design. Perhaps, the principles of neuroethology can help us improve the organization of human enterprises, and Professor Ewert's observations, models and simulations on the nerve cell networks underlying simple behaviors may be particularly informative, providing insights into the necessary components and strength of their relationships underlying successful social decision making. Hopefully, we can make use of such knowledge in the new year to develop a better understanding of risk that affects us all.

Acknowledgement
I thank Prof. J.-P. Ewert for teaching me about the neuroethology of toads. I thank Ranulfo Romo and Jeff Schall for sharing their insights into nerve cell mechanisms involved in decision making in the primate cerebral cortex. I am further indebted to simplyinfo.org and the commenters on www.scribblelive.com/Event/Japan_Earthquake5 for keeping me abreast on the latest developments in Japan.

Wednesday, December 21, 2011

Professor Ewert's Toad

About 35 years ago, I was privileged to attend Professor Dr. Jörg-Peter Ewert's seminar at the Institute of Zoology, Johann Wolfgang von Goethe University, in Frankfurt am Main. I was a student at the time. Prof. Ewert paid a visit to tell us about research underway in his laboratory at the University of Kassel on the nerve cell basis of behavior in the common toad Bufo bufo (Ewert, 1992 and 1997). The simplicity of the model caught my eye and remains deeply embedded in my memory to the day.

Behavior
Prof. Ewert and his colleagues had identified two distinct stereotypical behaviors: turning toward an object recognized as prey for catching and turning away in flight from an object recognized as a predator.

The investigators subsequently teased apart the visual cues that led to the opposed behaviors and decomposed the stimuli into the fundamental shapes and features to which the toads respond. Prof. Ewert was able to demonstrate that the toads recognize a cue as prey as long as it moves and is shaped like a thin bar elongated in direction of the movement. When the bar is oriented perpendicular, that is orthogonal to the direction of movement, the toads refrain (Wachowitz and Ewert, 1996). By contrast, if the object is moving and square, it is recognized as a potential predator, and the toads flee.

In 1993, Prof. Ewert produced a fascinating movie on his studies in collaboration with the Institute for Scientific Film (IWF Institut für Wissenschaflichen Film), Göttingen, Germany. The documentary movie can be viewed in three installments with the player below. The first installment demonstrates the visual cues necessary for prey catching.

Image Processing in the Visual System of the Common Toad - Behavior, Brain Function, Artificial Neuronal Net (IWF No. C 1805, 1993) by Prof. Dr. Jörg-Peter Ewert, University of Kassel, Germany, in collaboration with IWF, Knowledge and Media, Göttingen, Germany (courtesy Prof. Ewert).

Nerve Cell Mechanisms
With these observations in mind, the investigators examined the electrical spiking behavior of the nerve cells in the brain that encode the visual information and may explain the toads' decisions (second installment of the documentary).

The most prominent structure processing visual information in the toads' brain is the optic tectum; a layered midbrain structure composed of two hemispheres homologous to the superior colliculus in mammals. The superficial layers of each hemisphere receive input from the retina of the opposite visual hemifield. The retinotectal connections are spatially ordered, establishing a topographic map of the visual field across the tectal hemispheres such that the upper (superior) margin of the visual field is mapped at the midline (medial) of the opposite tectal hemisphere and the outward (temporal) margin of the visual field is mapped toward the animal's tail (caudal)(see Fig. 1 in Gaze and others, 1963). An object moving across the visual field will elicit local nerve cell responses sequentially across the optic tectum, depending on its shape, orientation and direction of movement. Therefore, the timing of local nerve cell excitation originating in the retina and integrated in the tectum constitutes the information instrumental to object recognition.

Recording electrical nerve cell spiking to visual stimulation from fine wire electrodes lowered into the optic tectum, Prof. Ewert and his colleagues could isolate nerve cells that responded only to bars elongated in the direction of movement, suggesting that these cells, called feature detectors, could identify stimulus cues of fundamental importance to the toads' behavior. In further research, the investigators employed metabolic mapping of cerebral activation with the autoradiographic deoxyglucose method of Sokoloff and others (1977) explained in the second installment of the documentary. This functional neuroimaging technique helped localize brain regions activated by the visual stimuli in question.

In addition to the optic tectum, prof. Ewert and colleagues observed nerve cell activation in an adjacent area near the midline called the thalamic pretectal area, or pretectum for short. In toads, this area receives input from the opposite eye and sends output to the optic tectum on the same side. Recordings of local nerve cell spiking activity identified cells that are active during avoidance behavior. One type, labelled TH3 cells, responded particularly vigorously when the toads saw large objects extending perpendicularly to the direction of motion, which could signal potential danger. A second type, labelled TH6, was activated by rapidly expanding objects coming at the animals. Yet another type, labelled TH10, responded to large stationary, obstacle-like objects. The investigators suggested that, in conjunction with nerve cells in the vestibular system that process information on the toads' balance, networks of various types of pretectal nerve cells effect the pursuit of different kinds of protective behavior. When the pretectum was damaged by a lesion, avoidance was absent, while orienting towards prey was enhanced, even to stimuli resembling a threat. Prey selectivity was impaired. By contrast, when the optic tectum was damaged, orienting behavior towards prey ceased (Ewert and others, 1996). In sum, nerve cells in the toads' pretectum and tectum govern the decision on prey catching or predator flight.

Further Exploits
In further studies, Prof. Ewert and colleagues uncovered other brain structures involved in the behaviors discussed above. The neurotransmitter dopamine is known for its role in reward-seeking and addiction. Apomorphine augments dopaminergic action. Glagow and Ewert (1999) observed that the systemic administration of apomorphine enhanced the toads' snapping for prey, while diminishing their oriented turning toward it. Functional neuroimaging showed that apomorphine increases stimulus-related nerve cell activity not only in the optic tectum, but also in structures that have been directly implicated in addictive behavior, that is the nucleus accumbens and the ventral tegmental area. By contrast, decreased nerve cell activity was found in the pretectum governing flight, and the striatum known to play a role in fine motor control of visually-guided behavior. In the limbic system implicated in the processing of emotions, the septum showed increased activation, while activation was decreased in the lateral amygdala involved in fear conditioning and emotional learning.

In addition to dopaminergic system effects on the toads' nerve cell activation and behavior, Prof. Ewert and colleagues examined neuropeptide Y which has been shown to affect food intake, playing a fundamental role in eating disorders and obesity. Pretectal nerve cells that connect to tectal nerve cells contain this neuropeptide. Funke and Ewert (2006) showed that topical application of neuropeptide Y suppressed nerve cell activation in the superficial layers of the optic tectum, even after the administration of apomorphine. The finding suggests an inhibitory role for this neuropeptide in the processing of visual cues, supporting the idea that both excitatory and inhibitory nerve cell inputs interact, and may compete, to effect either prey catching or flight.

Applications
The toad's catch or flight behavior may be rigid and innate. By contrast, the key stimuli that trip the behaviors are adjustable. The toad learns through conditioning. A hand holding a worm is first perceived as threat, but after repeated offerings will be recognized as food, even in the absence of a worm. Using the observed nerve cell responses, Prof. Ewert and colleagues were able to develop models of hypothetical nerve cell behavior in simulated networks and algorithms predicting outcome (Ewert, 1992). The last installment of the documentary ends with a proof of concept, demonstrating the successful implementation of the resulting computer application, guiding an industrial manufacturing robot with optical cues.

Epilogue
Prof. Ewert's research on the neuroethology of toad prey catching and flight provides a striking example of the fashion in which seemingly simple decisions are the result of complex nerve cell interactions. Similar strategies have been used to examine the nerve cell basis of decision making in primates (Jun and others, 2010; Lo and others, 2009), providing insights into our own decisions and whether free will exists.

In extrapolation, the brain-based simulation of nerve cell networks may allow us to develop more effective structures of human organization. When I began to revisit Prof. Ewert's work last February, the news broke on the possible entanglement of the owners of the New York Mets in Bernhard Madoff's Ponzi scheme (see Michael Rothfeld and Chad Bray's post with the title "Madoff Trustee Buzzes Mets" published online in The Wall Street Journal Feb. 5, 2011), as well as the entanglements of J.P. Morgan Chase (see David Caruso and Larry Neumeister's report for Associated Press with the title "Madoff trustee: JP Morgan execs warned of fraud" published online in The Wall Street Journal on Feb. 3, 2011) and Citigroup (see Grant Cool's post with the title "UPDATE 1-Citi tried to hand off Madoff exposure - lawsuit" published online on reuters Feb. 22, 2011). A few weeks ago, members of the Madoff family made their stance on the affair known in published books (Truth and Consequences: Life Inside the Madoff Family, The End of Normal) and media appearances.

The different behaviors of the Madoff clients and collaborators mentioned above suggest that people in large organizations like investment banks seem to interact very much like the nerve cells in the toads' brain. Some facilitate action, while others slam on the brakes. Outcome depends on which party prevails. The decisions the banks eventually took were the result of a constant tug of war between those who sought business with Madoff because of the stellar performance of his funds and those who warned that the risks involved could not be assessed, because Madoff and his associates withheld crucial information. By contrast, small organizations with fewer people may favor less optimal risk evaluation and pounce at the apparent golden opportunity without in-depth evaluation.

Nerve cell networks observed in nature and implemented in modeled simulations may inform us about the types and the number of elements, as well as the weight of their interactions, sufficient and necessary for an organization to successfully carry out its mission. The Madoff experience glaringly demonstrates that it is best practice to entrust wealth not into the hands of one person, but an organization with a long-standing record of responsible decision making, since it does not take a brain lesion to cause one person's ability of making prudent decisions to fail. Yet, the financial crisis of 2008 aptly demonstrates that even such organizations may fail when inhibition does not adequately balance excitation. Confronted with uncertainty, caution dictates to spread the risk.

Acknowledgement
I thank J.-P. Ewert for teaching me about the neuroethology of toads and sharing the movie with me.

References

Wednesday, October 5, 2011

A Great Mind is No More

Steve Jobs passed away. Reuters broke the news 7:56 EST with a post entitled "Apple co-founder Steve Jobs dead at 56". Steve’s advice for us was to live every day as if it was our last. Time is our most precious commodity. He used it well. The United States lost one of her finest innovators and a great human being.


His biography by Walter Isaacson to be published later this month will be interesting.

Sunday, October 2, 2011

Morat-Fribourg, 2011

While I grappled for my old booklets of 25 years ago to reminisce, I discovered to my shame that my edition count was one off in my past posts. I corrected the miscount retroactively. The 78th edition of the race was held today.


Caroline Chepkwony, Kenya (59.09,5), and


Stéphane Joly, Switzerland (53.07,3), won.
Congratulations!

More results and video clips are available here.

Related posts


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Saturday, October 1, 2011

Whiskers, Manatees & The Mind


Harbor seal (Phoca vitulina),
courtesy L. Heafner. 
Unlike the follicles of common hair, the follicles of whiskers, also known as tactile vibrissae or sinus hairs, are complex sensory organs in which the hair is surrounded by a cushioning blood sinus and which are invested with thousands of innervated touch receptors of different type. Vincent (1913) described in great detail the intricate anatomy of the follicles of facial whisker in the rat, and she was the first to recognize the important role they play in tactile exploration and navigation.

Mammals with whiskers are not exclusively terrestrial. Pinnipeds possess whiskers on their snout.  Szymonowicz (1930) was the first to describe the follicular innervation of facial whisker follicles in the harbor seal Phoca vitulina. Recent behavioral studies provide astounding evidence that harbor seals can locate objects by their wake with their whiskers (Dehnhardt and others, 2001).

Not only carnivorous marine mammals seem to make good use of their whiskers that way. Notably, the herbivorous Florida manatee Trichechus manatus latirostris, a subspecies of the West Indian manatee, also appears to use whiskers for underwater exploration and navigation. Moreover, the long whiskers surrounding the mouth are employed for palpating and grasping plant matter when feeding. Florida manatees inhabit shallow, warm coastal waters. When the cold of winter arrives, the animals migrate south and up rivers into ponds and warm springs, where they congregate to forage and socialize.

Much we know about the Florida manatee brain, we owe to the ground-laying research of Professor Roger Reep from the University of Florida at Gainesville and his colleagues. Erica Goode described his work in her article with the title "Sleek? Well, No. Complex? Yes, Indeed." published online in The New York Times on Aug. 29, 2006. The article contains a slide show with Professor Reep's comments entitled "The Mind of The Manatee" which includes detailed photographs of the whiskers. Professor Reep co-authored an exhaustive book on manatees with the title "The Florida Manatee: Biology and Conservation".

The whiskers of the Florida manatee are densest on the face (2,000) with greatest density, roughly 600, in an area between the upper lip and the nose known as the oral disk (Reep and others, 2001).  Another 3,000 cover the remaining body (Reep and others, 2002). Sarko and others (2007) recently described the follicles of the manatee facial whiskers in anatomical detail. Although the facial whisker follicles receive at on average 50 myelinated nerve fibers per follicle almost twice the follicular innervation the whiskers of the rest of the body receive at 30, the heightened sense of touch comprising the entire body surface may represent a great advantage for navigating the dimly lit, muddy waters of the manatee's grazing grounds.

Considering their body size, manatees possess small brains (Reep and O'Shea, 1990). Unlike our heavily convoluted cerebral cortex, the manatee's is smooth showing only one fissure, homologous to our Rolandic fissure, running from top to bottom at the center of the cerebral hemisphere (shown in this NYT graphic with the title "A Sensitive creature"). Compared to ours, the manatee cortex seems thicker, and the gray matter differentiated in more layers. In addition, Professor Reep notes in Erica Goode's article condensations of nerve cells in the deep layers of somatic sensory cortex that may represent the whiskers topographically analogous to the barrels in mouse somatic sensory cortex (Woolsey and Van der Loos, 1970). Interestingly, Professor Reep also found such cell condensations in auditory cortex. The meaning of this finding is not yet understood.

Professor Reep further reports that manatees aptly localize sources of brief tone pips as low as 23 Hz in pitch. The cell condensations in auditory cortex may therefore suggest crossmodal processing of low frequency vibrations sensed with the whiskers. I discussed that rodent whiskers may detect low frequency ground motion in my post with the title "The Quest for the Infrasound Acoustic Fovea" published Oct 12, 2009. Without doubt, uncovering the nerve cell mechanisms underlying manatee behavior will provide exciting novel insights into the detection of low-frequency water motion by whiskered marine mammals and the processing of tactile input for underwater navigation.



If we peer through the above window preferably in the mornings EST, we may once in a while see manatees grazing and socializing in their habitat at Ellie Schiller Homosassa Springs Wildlife State Park, Florida, via their manatee cam (with permission, Susan Strawbridge, Ellie Schiller Homosassa Springs Wildlife State Park).

For close fullscreen examination of manatee whisker action, we must visit the park's manatee cam, which also provides a series of the ten most recent images for an improved sense of the action and detailed information on visitor activities at the park. An actual visit would be most exciting of course.

References
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Monday, July 4, 2011

A Marker to Remember

Villagers in the Alps must not fear tsunamis like the inhabitants of the east coast of Japan. But they must confront snow avalanches which may be highly destructive to home and life as well.

Unlike tsunamis in Japan, avalanches in the Alps recur with great regularity every year. Indeed, some avalanches fall with seemingly clockwork-like precision. Hamlets huddled on the slopes of deep, narrow valleys between towering mountains are particularly at risk. Over the centuries, the villagers maintained logs in which they meticulously recorded the time and date a particular avalanche descended, the precise area affected, the depth of the snow and its composition.


Topographic map of the surroundings of the village of Obergoms, Vs, Switzerland, showing the extent of avalanches (hatched) recorded in February, 1951, plus the paths of avalanches (arrows) noted between 1700 and 1999 (courtesy http://www.obergommer.ch).  
With the help of this knowledge, the villagers grew protective forests on the slopes above and erected barriers to hold back the snow masses on summits and ridges. They were able to designate uninhabitable zones that were indefensible. This tradition of prudence rooted in generation-old experience represents a powerful example telling us that our survival depends in no small way on our awareness of history and our willingness to learn from it.

Report of Japanese Government to the IAEA Ministerial Conference on Nuclear Safety, Fig. III-1-17.
Similarly, based on age-old experience with tsunamis, villagers in the Aneyoshi neighborhood of the modern-day city and fishing port of Miyako, Iwate Prefecture, on the northeast coast of Japan aptly erected a roadside marker, warning future generations that if they built their homes downhills from this point, their lives would be in peril (for review see Hideo Takagi's remarkable opinion piece with the title "Preserving the Remains in Areas Struck by the Tsunami-Applying the Aftermath of the Tragedy to Disaster Education and Enlightenment" posted on the Daily Yomiuri online). The humble stone monument can be seen in the left photograph above. The debris besides the road visible in the right photograph documents that the Tohoku-Oki Earthquake and Tsunami on Mar. 11, 2011, starkly proved the stone's inscription true (photograph below).

The marker's warning (photo by Dr. Masayuki Oishi).
The catastrophe exacted the greatest loss of lives in Japan's post-war history. Moreover, quake and tsunami devastated the Fukushima Dai-ichi Nuclear Power Station on the shores of the Pacific Ocean outside Fukushima City, precipitating the third nuclear reactor accident with fuel melt-downs in the history of the commercial use of nuclear power only rivaled by Three Mile Island in 1979 and Chernobyl in 1986. Four reactors suffered destructive explosions, radioactively contaminating air, land, and sea with yet unfathomable consequences. Mitigation is ongoing. The health of hundreds of thousands of people is at stake.


Radiation dose meter at Fukushima Medical University 35 miles from the stricken nuclear power station. The readings are continuously updated. In the week after the quake, dosemeter readings in Fukushima City spiked above 20 μSv/h. At this dose, we are exposed to an effective absorbed dose of 0.175 Sv in a year which corresponds to 17.5 rem; a dose that nuclear industry professionals perhaps accumulate over their entire career.

Perhaps, one day monuments similar to that on the road near Miyako will be erected in Fukushima at a safe distance from the ruins of the Fukushima Dai-ichi Nuclear Power Station, reminding future generations on their quest for ever more energy not to proceed beyond this point, because the price exacted is too high.

Related Posts

Sunday, July 3, 2011

Fukushima: Failure by Design


This post concludes my quatrology of essays touching on peculiarities of the reactor accident at the Fukushima I (Daiichi) Nuclear Power Station on the northeastern coast of Japan as a result of the Tohoku-Oki Earthquake and Tsunami on Mar. 11, 2011. I will continue to update the content of the series as new information crucial to the discussed issues becomes available.

This essay once more is of technical nature, seeking to examine potential system failures that led to the fuel core melt-downs and melt-throughs at the three reactor units that were producing power at the Fukushima Daiichi Nuclear Power Station on the day of the earthquake and tsunami. The fourth unit with extensive damage was shutdown at the time and the fuel was stored in its spent fuel pool. Forceful explosions resulted from excessive accumulation of hydrogen in the buildings of the four units. The hydrogen was produced by radiolysis and oxidation of the cladding of superheated fuel rods. Radioactive material in amounts only superseded by the Chernobyl reactor accident, 1986, was released into the atmosphere and into the ocean with yet unfathomable consequences for public health. The lives of hundreds of thousands of residents around the plant will be profoundly affected. Fukushima Prefecture alone is home to roughly 3 million people.

The calamity has been unfolding on the heel of the utter destruction of coastal villages and towns owing to the earthquake and tsunami. According to the Report of the Japanese Government to the IAEA Ministerial Conference on Nuclear Safety, page III-10, released last month, 24,769 persons were reported dead or still missing on May 30, 2011. The examination of technicalities of the reactor disaster must pale compared with the human toll exacted. However, this essay may help shine a light on shortcomings in design that may pertain as well to other nuclear power reactors around the world and help prevent yet another disaster that added in unprecedented ways to this human tragedy of mind-shattering proportion.
Schema of a boiling water reactor (BWR) with a Mark I primary containment system consisting of the pear-shaped drywell and the ring-shaped suppression chamber which contains a pool of water used to depressurize the containment when needed. The drywell houses the reactor pressure vessel (maroon) with the fuel core in which steam is produced for power generation (courtesy NRC).
The four greatly damaged boiling water reactors, BWRs for short, at Fukushima Daiichi Nuclear Power Station possess the same Mark I primary containment system, consisting of a pear-shaped drywell connected to a massive ring-shaped suppression chamber, also known as wetwell. However, major differences in reactor protection system design were implemented based on the time of construction. Unit 1 is the oldest. Indeed, the unit represents the oldest commercial nuclear power reactor in Japan. It was completed in 1970 and is considered a third generation BWR (BWR-3). Among the nuclear reactors in the US, the one at Oyster Creek Nuclear Power Station, Lacey Township, New Jersey, which is considered a BWR-2, and Unit 2 at Dresden Nuclear Power Station, Morris, Illinois, which is considered a BWR-3, appear to resemble the design of Fukushima Daiichi Unit 1 most closely. By contrast, Units 2, 3 and 4 follow the more recent BWR-4 design, which is most common for operating BWRs in the US today.

The video below provides an overview on BWR-3 reactors and Mark I containment systems in the US and a good impression of the structures' dimensions:


Though Units 1, 2 and 3 incurred loss of coolant accidents with fuel core melt-downs and, very possibly, melt-throughs penetrating their primary containments, differences in design, particularly of systems that cool reactor cores and vent gas and steam, may help explain the observed differences in event sequence and thrust.

The reactor turbine feed loop represents the main circulation loop for steam and water during normal reactor operations, transferring the heat generated by nuclear fission to the turbine that drives the electric power generator. Water condensed in the turbine condensers continuously replenishes coolant in the 500-m3 reactor pressure vessel (RPV), preventing the fuel core from overheating. In addition to serving as coolant, water is used to moderate neutron fluxes between the fuel rods, enabling a controlled, sustained nuclear chain reaction.

After a seismic SCRAM like at Fukushima, main steam isolation valves shut the turbine loop off. Though the safety rods are inserted to stop nuclear fission, decay of neutron-activated radioactive isotopes continues to produce heat which keeps the reactor water temperature above boiling. Steam and pressure build in the RPV. Once a setpoint is reached, the safety/relief valves of the automatic depressurization system (ADS) succinctly depressurize the RPV to prevent damage to the vessel, venting steam into the suppression pool. As a consequence of the depressurization, the water level in the RPV falls rapidly unless water is injected. The emergency core cooling system, or ECCS for short, consists of several interrelated standby systems that can be used to achieve replenishment with auxiliary feedwater.

Schema showing IC (BWR-3) and RCIC (BWR-4) standby cooling systems (Stoll U, 2011).
In addition to high pressure coolant injection (HPCI) and massive low pressure coolant injection (LPCI) pumps, the isolation condenser (IC) constitutes a third-line option of injecting auxiliary water into the RPV during the shutdown of BWR-3s like Fukushima Daiichi Unit 1. The IC condenses steam from the RPV and reintroduces the water near the vessel head entirely passively driven by convection and gravity. No pumps are needed. According to the scram log of Unit 1, the IC was initiated immediately after the seismic SCRAM, but had run dry for unknown reasons within two hours (see previous post with the title "Fukushima: Failure of the Mind" published May 17, 2011).

In BWR-4s, by contrast, the IC is replaced with the reactor core isolation cooling (RCIC) system [USNRC Technical Training Center, Boiling Water Reactor GE BWRA4 Technology Technology Manual (Rev 0197), Chapter 2.7: Reactor Core Isolation System]. At Fukushima Daiichi, the RCIC and the HPCI are housed in rooms on the northern and southern corner, respectively, on the first basement level outside the western wall of the reactor buildings. The main component of the RCIC system is a turbine-driven pump which can discharge water through the uppermost feedwater line into the RPV at 400 gallons, or roughly 1.5 m3, per minute. Compared to the HPCI at 19 m3 per minute and the LPCI at 150 m3 per minute, the RCIC's capacity seems small. Its pump would need five hours and a half to fill the entire RPV. However, the rate suffices to replace the boil-off anticipated 15 minutes after shutdown.

Control room whiteboard with operator notes on Unit 2 through the first hour after the seismic SCRAM. The entry at 15:01 mentions the RCIC system the first time (courtesy TEPCO).
The RCIC pump's turbine is fed from the main steam line with the steam produced by the reactor decay heat. The exhaust is discharged into the suppression chamber pool. Alternating and direct current are needed for system initiation. Once started, however, the RCIC system should be capable of running controlled by battery-powered direct current alone. Alas, the pump has a distinct history of operational failures mainly because of governor valve malfunction [Boardman, JR (1994) Operating Experience Feedback Report - Reliability of Safety-Related Steam Turbine-Driven Standby Pumps. NUREG-1275, Vol. 10].

The Terry Corporation, now part of Dresser-Rand, manufactured most turbines of the kind used to drive RCIC pumps in US BWRs. Reaching full capacity within two minutes from start-up, the pumps are aligned by default to remove water from the condensate storage tank, also known as the contaminated condensate storage tank, and inject it into the RPV. If tank water is unavailable or if the suppression chamber pool reaches a preset level, valves automatically direct the suction path via a 16-inch pipe to the torus.

Example of a Terry RCIC turbine.
However, the NRC post-inspection letter to Exelon Nuclear below dated Jun. 29, 2004, provides evidence that RCIC suction isolation valves have failed in US reactors in the past because of inadequate control design.

List of Inspection Reports 2004004[964]


Outboard piping downstream from the pump is commonly not as seismically resistant as the inboard piping from the suppression chamber which is considered existential to reactor safety. If the RCIC design at the Fukushima Daiichi reactors had been the same as that mandated in the US, the inferior seismic rating of the parts of the RCIC loop downstream of the pump could have contributed significantly to the inability of delivering adequate coolant to Units 2 and 3 after the earthquake.

According to Jake Adelstein and David McNeill's post with the title "Meltdown: What Really Happened at Fukushima?" published online in the Atlantic Wire on Jul. 2, 2011, eyewitnesses report that the earthquake immediately inflicted widespread, substantial damage to piping at the station. The quake may have ruptured less seismically-hardened RCIC piping, providing a continuous escape route for coolant, steam, and non-condensible gases, e.g. hydrogen and radioactive noble gases, from the suppression chamber. The suppression chamber pool, however, supplies the coolant for the emergency core cooling system.

This photograph taken May 10, 2011, added Feb. 27, 2012, shows the pair of steam vent pipes for isolation condenser subsystem A and B, exiting the reactor building of Unit 1 in the middle of the wall immediately under the refueling floor. Note the vent pipe surrounded by debris is uncapped. This must be the vent from which steam was observed emanating in the hours after the quake (courtesy Daisuke Tsuda).
In normal operation, the tall stack towers between Units 1 and 2 and Units 3 and 4 at Fukushima Daiichi Nuclear Power Station are designed to vent filtered, decontaminated off-gases from the main steam turbine [Row TH (1973) Radioactive Waste Systems and Radioactive Effluents]. By contrast, separate shorter stacks attached to the reactor building walls vent uncontaminated effluents from the buildings, e.g. the steam vents of Unit 1's isolation condenser in the photograph above. If increased levels of radioactivity are detected, the effluents will be routed through the standby gas treatment system to the stack. This system also filters gases from the primary containment. Compared to the towers, the stacks for uncontaminated effluents are short, ending just above the roofline. One is still visibly intact on the northwest corner of Unit 2.

Vent stack on northwest corner of the reactor building of Unit 2.
Roughly 29 seconds into the report below, the footage suggests that steam was already emanating from the reactor building rooflines when the first tsunami waves arrived, probably through these short stacks.


At 15:29, that is approximately the same time the footage above was recorded, a monitor about a mile from the reactor buildings sounded radiation alert according to Yuji Okada, Tsuyoshi Inajima and Shunichi Ozasa's post with the title "Fukushima May Have Leaked Radiation Before Tsunami" published online on Bloomberg News May 19, 2011. The source of the radioactivity may have been contaminated steam from the suppression chamber, escaping through the short stacks via damaged valves and broken piping of standby cooling systems like the RCIC. Once the fuel rods in the reactor core super-heated because of the persistent loss of coolant, their zircalloy cladding reacted with water to produce large amounts of hydrogen that accumulated in the reactor buildings, until the gas detonated in violent explosions.

It is important to note that neither the widely-acknowledged extended offsite power outage nor the failure of onsite emergency diesel generators may have caused the standby coolant systems to malfunction. Rather, the constant leakage of coolant through shattered loops in these systems may have prevented effective reactor core cooling and may have been detrimental to further attempts of cooling with the addition of seawater during the days after the earthquake and tsunami. The loss of coolant eventually would lead to extensive uncovering of reactor fuel cores, core melt-downs and the eventual melt-throughs of highly radioactive material.

The operator of the Fukushima Daiichi Nuclear Power Station known as Tokyo Electric Power Company, or TEPCO for short, apparently paid little heed to maintenance and improvements of emergency equipment instrumental for a successful cold shutdown after a loss of coolant accident. TEPCO's probabilistic risk assessment predicted a temblor of the strength of the Tohoku-oki Earthquake to happen only once in ten-thousand years or less (Report of the Japanese Government to the IAEA Ministerial Conference on Nuclear Safety, figure III-2-3, page III-39). Loss of coolant accidents may be met by similarly anemic standby cooling systems at any nuclear power station with such reactors in an earthquake zone.

Acknowledgement
This post would have been impossible without the contributors to Japan Earthquake Live and the invaluable information on SimplyInfo.org.

Related Posts
Addenda
  • According to the report of Japan's Nuclear and Industrial Safety Agency (NISA) to the International Atomic Energy Agency with the title "Report of Japanese Government to the IAEA Ministerial Conference on Nuclear Safety - The Accident at TEPCO’s Fukushima Nuclear Power Stations -", June 2011, Unit 1 possessed two redundant isolation condensers and a high pressure coolant injection (HPCI) system, whereas the other units were equipped with one RCIC system and one HPCI system. The HPCI system consists of a turbine-driven pump and a turbine-driven booster pump which can be used when the RPV pressure approaches design basis. The suction paths are the same as for the RCIC (07/6/11):
    NISA system diagram of Unit 1 (Fig. IV-2-1), showing two isolation condensers on the left of the reactor.












Flow Rates for Standby Cooling Systems at Fukushima Daiichi Nuclear Power Station according to the NISA report to the IAEA in June, 2011, Tab IV-2-1 (07/06/11).
Total Coolant Injection Rate [m3/min]
Unit 1 2 3
HPCI 14.7 16.0 16.0
LPCI N/A 116 128
RCIC N/A 1.6 1.6
  • NISA's report confirms the above cited claim by Bloomberg News that elevated levels of radioactivity were detected on the station premises after the quake and before the tsunami. I quote from the report's page V-18:
    “After the earthquake, measured values of GM measuring tubes were higher than usual in reactor facilities, while values measured at monitoring posts installed in the surrounding monitoring areas of Fukushima Dai-ichi NPS showed no anomaly. (Attachment V-9 Measured results of monitoring posts)” (07/18/2011).
  • In addition, on page 12 of NISA's report, we find the following description of the attempts of cooling the core of Fukushima Daiichi Nuclear Power Station's Reactor 3 after the earthquake and tsunami:
    “The Reactor Core Isolation Cooling System (RCIC) was manually started at 15:05 on March 11. It stopped automatically at 15:25 on the same day due to the rise of the reactor water level. It was started manually at 16:03 on the same day, and the RCIC stopped at 11:36 on March 12. The High Pressure Core Injection System (HPCI) automatically started due to the reactor low water level (L-2) at 12:35 on the same day, and the HPCI stopped at 2:42 on March 13. The reason for that appears to be a drop of pressure in the reactor. The other probable cause could be water-vapor outflow from the HPCI system.”
    NISA hypothesizes further:
    “..., the fuel appears to have been exposed due to a drop of the reactor water-level at around 08:00 on March 13, and the core started melting afterwards.

    On Jul. 28, 2011, TEPCO released a handout with the title "Factors of fluctuation in plant parameters such as reduction of the pressure in Reactor during operation of High Pressure Coolant Injection System" with which the company hopes to clarify that the HPCI coolant loop remained intact, contrary to speculations proffered earlier in the NISA report. Inspection of the graphs provided in this document shows that the RCIC system resumed function one more time shortly after noon on Mar. 12 and stopped again in the early morning hours of Mar. 13.

RPV water level time courses for Unit 3, based on trial analysis with a Modular Accident Analysis Program (MAAP)  and measurements. Matching up time lines, RICI is synonymous with RCIC system.
In accord with the hypothesis entertained in my post, RCIC failure remains the most likely cause that precipitated the reactor's demise. During the morning hours of Mar. 13 after the RCIC had come to its final halt, RPV pressure rose rapidly and its water level dropped decisively, uncovering the core.

RPV pressure level time courses for Unit 3, based on trial analysis with a Modular Accident Analysis Program (MAAP) and measurements. RICI is synonymous with the RCIC system.
A safety/relief valve was opened, relieving the pressure into the primary containment at around 9:00 on Mar. 13. At 5:20 on the following day, the operators vented the suppression chamber with hardened venting. At 11:01, a massive hydrogen explosion severely damaged Unit 3 (07/29/11).
  • Photograph taken Oct. 3, 2008. The reactor buildings of Unit 1 (top, slightly offset toward the right) to 4 (bottom) are situated on the the left, the turbine buildings on the right  (cryptome.org). The condensate storage tanks consist of the four large white tanks in front of the turbine buildings on the oceanside. According to this Nuclear Engineering International News post with the title "Fukushima Daiichi plant is running out of wastewater storage space" published April 8, 2011, their storage capacity ranges from 1,900 m3 at Unit 1 to 2,500 m3 at the other three units.
    According to the Shift Supervisor Task Handover Journals for Units 1,2 and Units 3,4 released by TEPCO, the condensate storage tanks were about two-thirds filled on March 11. The volume could have fed the RCIC pumps for roughly 19 hours. Once the water in the tanks was running low, the operators had to switch the suction isolation valves, setting the suction path to the suppression chamber of the primary containment as alternate source for the RCIC and HPCI systems. At Unit 2, the tank was two-thirds full. The supply should have lasted for 16 hours, if it had been used for the RCIC system alone. In actuality, it lasted only 12 to 13 hours. According to the update of the Government of Japan to the International Atomic Energy Agency with the title "Additional Report of Japanese Government to IAEA - Accident at TEPCO's Fukushima Nuclear Power Stations Transmitted by Nuclear Emergency Response Headquarters, Government of Japan, 15 Sep 2011", page II-93, “from 04:20 to 05:00, March 12, as water level of the Condensate Storage Tank (CST) decreased and also in order to control rising of the S/C (suppression chamber) water level, the water source for the RCIC was switched from the CST to the S/C for the RCIC to continue injecting water.” The change of source appears to have accelerated the reactor's demise. The suction isolation valves may have failed (10/30/2011).
  • According to Cook and others (1981), the steam-driven pumps of the RCIC and the HPCI system are set to trip when the temperature near the equipment reaches 93.3 °C. Both pumps suck coolant for the core from the condensate storage tank. Once the tank is exhausted, suction is aligned with the suppression chamber pool. TEPCO operators repeatedly opened the safety relief valves of Units 2 and 3 to release high temperature steam from the reactor pressure vessel into the suppression chamber pool, progressively elevating the water temperature.
    RCIC and HPCI are components of the emergency core cooling system (ECCS). The suction header for the cooling water both systems pump into the reactor pressure vessel is at the bottom of suppression chamber (courtesy: simplyinfo.org).
    In simulations by Hoshi and Hirano (2012), the water exceeded 95 °C at the bottom of Unit 3's suppression pool where the suction head for the RCIC and HPCI systems are located, surpassing the trip points of the RCIC and HPCI pumps. Excess temperature in the suppression pools therefore is a probable cause for these systems at Units 2 and 3 to fail on the third day of the accident (09/03/2013).
    Simulated suppression pool temperature at Unit 3 (Hoshi H, Hirano M, 2012).

Friday, May 27, 2011

A Fukushima Mother's Letter

Steven L. Herman, Voice of America (VOA) Bureau Chief/Correspondent in Seoul, relayed this message. I could not help, but repost it:

When Tomoko-san, a mother of two in Fukushima City, heard from an NGO worker that I was going to be in Fukushima to report on a story about radiation levels at local schools, she was kind enough to volunteer her time to speak to me – and handed me this letter. I promised to translate it and share it with you. So here it is:

“To people in the United States and around the world,


I am so sorry for the uranium and plutonium that Japan has released into the environment. The fallout from Fukushima has already circled the world many times, reaching Hawaii, Alaska, and even New York.


We live 60 kilometers (37 miles) from the plant and our homes have been contaminated beyond levels seen at Chernobyl. The cesium-137 they are finding in the soil will be here for 30 years. But the government will not help us. They tell us to stay put. They tell our kids to put on masks and hats and keep going to school.


This summer, our children won’t be able to go swimming. They won’t be able to play outside. They can’t eat Fukushima’s delicious peaches. They can’t even eat the rice that the Fukushima farmers are making. They can’t go visit Fukushima’s beautiful rivers, mountains and lakes. This makes me sad. This fills me with so much regret.


Instead, our children will spend the summer in their classrooms, with no air conditioning, sweating as they try to concentrate on their lessons. We don’t even know how much radiation they’ve already been exposed to.


I was eight years old when the Fukushima Daiichi plant opened. If I had understood what they were building, I would have fought against it. I didn’t realize that it contained dangers that would threaten my children, my children’s children and their children.


I am grateful for all the aid all the world has sent us. Now, what we ask is for you to speak out against the Japanese government. Pressure them into taking action. Tell them to make protecting children their top priority.


Thank you so much,


Tomoko Hatsuzawa
Fukushima City
May 25, 2011”

Addenda
  • No love lost: Anguished Fukushima citizens face off with government representatives at a town hall meeting held Jul. 19, 2011, to discuss the consequences of the Daiichi reactor accidents. The government of Japan promised differently in its report with the title "Report of Japanese Government to the IAEA Ministerial Conference on Nuclear Safety - The Accident at TEPCO’s Fukushima Nuclear Power Stations -" to the International Atomic Energy Agency dated June, 2011. The following claim is excerpted from the report's chapter X (www.kantei.go.jp): “In order to allay health concerns of the residents, screening and decontamination of the residents will definitely be implemented. A health counseling hotline was opened and on-site health counseling, and mental care is provided to ensure that residents’ health is properly managed.” (07/26/11).
A badge expressing parents' concern (08/25/11).
Related Posts

Video Message from Katsutaka Idogawa, Mayor of Futaba Town. from Atsushi Funahashi on Vimeo.
This is a Video Message of Katsutaka Idogawa, Mayor of Futaba Town, Fukushima. It was meant towards German/International audience at Berlin International Film Festival 2012, where NUCLEAR NATION, a documentary of Futaba refugees, was premiered in February.



You can read its text here;

http://nuclearnation.jp/en/?p=135