An IAEA perspective on Fukushima

I recently had the pleasure to attend a lecture by Randy Beatty (who has been affiliated with the International Atomic Energy Agency [IAEA] for some time), focusing upon the IAEA's perspective on Fukushima, particularly in terms of our current understanding of the sequence of events (which is still evolving) as well as the IAEA's interactions with the government of Japan and TEPCO (the owner of the Fukushima reactors).

Below is a summary of some of the major topics covered, including a more detailed reconstruction of the accident sequence (and particular, both the relatively small timeframe in which most of the damage occurred) as well as a better understanding of how other, secondary complications such as the hydrogen explosions came about. Finally, more precise estimates of the quantities of radiation released and the direction of its spread shed some light on how many were affected and the relative appropriateness of certain evacuation precautions.

Accident sequence

The "main" narrative of the Fukushima incident is relatively understood, summarized as follows:

• Following the 9.0 earthquake, each of the reactors was shut down, halting the fission reaction
• Backup power from diesel generators came online to operate coolant pumps to remove decay heat from the reactor until these were wiped out by the incoming tsunami; 
• Battery backup power came online to operate these pumps until such power was depleted
• Water inside the reactors began to boil away as it heated up.
• As water boiled away, the fuel rods heated up.
• Water interacted with the extremely hot zirconium cladding, producing free hydrogen (which lead to the hydrogen explosions)
• As the fuel rods heated up, the cladding failed, releasing radioactive fission product gasses. The fuel is also believed to have partially melted when it became uncovered by water, releasing more radioactive materials from the core.
• Cooling was restored by injecting seawater into the reactors to quench the decay heat from the rods and prevent further melting.

What has been perhaps less well-understood are issues such as how much fuel melted, how long the core was not covered by water, and the extent of the radioactive release. A great deal of research work is being conducted at the national laboratories presently to reconstruct what was going on inside the reactors in the first few hours (immediately after the rectors were shut down) in order to characterize what exactly happened; thus our understanding on this point will continue to evolve over the next several years.

One of the key issues that seems relevant in much of the accident sequence is the relative speed at which events progressed. While most of the world witnessed the event as a long, drawn-out drama, much of the damage had already occurred in the first few days (and in particular, the several hours the reactors were without power before seawater injection was applied). 

Courtesy of Randy's presentation, here is a good timeline of what occurred at each reactor.

Unit 1

• March 11, 2:46 PM: External power lost, emergency diesel generators begin to supply power
• March 11, 2:52 PM: Emergency cooling systems (isolation condenser) started
• March 11, 3:37 PM: All AC power lost
• March 11, around 5:00 PM: Fuel exposed, core melt begins
• March 12, 5:46 A.M.: Begin of freshwater injection from fire extinguishing line

The fuel was estimated to have been uncovered for about 2.5 hours. Water injection was estimated to have stopped (due to the loss of power) for 14 hours and 9 minutes. 

Unit 2

• March 11, 2:47 PM: External power lost, backup diesel generators start up
• March 11, 2:50 PM: Emergency cooling system (Reactor Core Isolation Cooling system - RCIC) starts up
• March 11, 3:11 PM: All AC power lost
• March 14, 1:25 PM: RCIC operation stops
• March 14, around 6:00 PM: Fuel exposed, core melt begins.
• March 14, 7:54 PM: Seawater injection from a fire extinguishing line begins

Approximately 30% of the core of Unit 2 was estimated to have been exposed in the 6 hours and 29 minutes in which cooling was unavailable.

Unit 3

• March 11, 2:47 PM: Loss of external power, start-up of emergency diesel generators
• March 11, 3:05 PM: Startup of emergency cooling system (RCIC)
• March 11, 3:41 PM: Loss of all AC power
• March 12, 11:36 AM: RCIC stops due to loss of power
• March 12, 12:35 PM: Startup of HPCI (high pressure core injection) system as a backup cooling measure
• March 13, 2:42 AM: Stop of HPCI
• March 13, around 8:00 AM: Fuel exposed, core melt begins
• March 13, 9:25 AM: Startup of freshwater injection into core from a fire extinguisher line

The fuel thus appears to have been exposed from approximately 1.5 hours, with water injection having been unavailable for about 7 hours.

What this means

Several issues are clear from this timeline of events. First, despite an earthquake beyond the design basis for the reactors, emergency systems largely functioned as intended. Were the backup power systems not destroyed by the following tsunami, it is likely the incident would have largely been contained without incident; indeed, it was the "total station blackout" condition which was the root cause of the radioactive releases (i.e., by allowing the fuel to overheat). In this sense, one criticism made of the Japanese government was in its initial reluctance to accept assistance from outside agents such as the United States, which had offered to airlift in replacement generators when the tsunami destroyed the initial generators. Whether this initial refusal was a face-saving measure or something else remains to be seen, but quite clearly this exacerbated the issue.

The loss of emergency diesel power systems was near-total due to the tsunami; a total of twelve diesel generator units were present at Units 1-6, of which all but one at Unit 6 were wiped out. (This remaining unit was elevated above the tsunami.)

Backup systems such as battery backups appear to have mitigated some of the damage, particularly in the case of Unit 3, where Japanese officials report that the battery backups appear to have lasted approximately 50% longer than their design life (around 18 hours, compared to a design life of 12).

Most stark here is the relatively short time period in which most of the damage occurred - in most cases, the fuel was exposed for only a few hours (up to about 6.5 hours for Unit 2, which experienced the most severe fuel damage). Likewise, following the complete loss of power, it took only a few hours for the core to become uncovered due to water boiling from the core.

Complicating the situation at Unit 2 may have been the hydrogen explosion which occurred in the suppression pool (the donut-shaped cavity at the bottom of the reactor, designed to condense steam from the reactor to recirculate coolant and draw off heat). This appears to have accelerated the damage at Unit 2, explaining the extent of damage seen there.

Finally, most of the radioactive release appears to have occurred within the first three days, following the uncovering of the fuel in the cores of Units 1-3. Due to extremely difficult conditions at the reactors from the earthquake and tsunami (i.e., extreme devastation and an overall lack of electricity, with no instrumentation information from inside the reactor buildings), the overall extent and significance of radioactive releases would not be ascertained until later.

Spent fuel pools at Unit 4

Condition of spent fuel in the pool

Unlike Units 1-3, Unit 4 was in a scheduled outage for refueling and maintenance prior to the earthquake. Rather, Unit 4's spent fuel pool contained a mixture of older and newer, more recently-ejected fuel (which is hotter, due to a greater amount of short-lived fission products remaining in the fuel).

The loss of power to Unit 4 produced a similar situation to Units 1-3; even though the fission reaction is "off" in the fuel, short-lived radioactive materials in the fuel continues to decay, generating heat. This heat must be removed from the fuel, thus fuel is stored in deep pools of water, generally kept around room temperature and pressure. (In other words, spent fuel pools are quite similar to very deep swimming pools for spent fuel rods). The water serves a dual purpose; first, the water "wicks" away heat from the rods, keeping them cool, and second the water provides an effective shield from radiation emitted by the spent fuel. 

Heat in the cooling pool must be removed, just as is the case of reactors - thus cooling pumps exist to circulate the cooling water in order to maintain the temperature of the pool (and thus the spent fuel). Thus, should these pumps be disabled (due to a loss of power), this water will begin to heat up as well, eventually boiling. However, spent fuel in the pools is generally much cooler than that from fuel in reactors which have just shut down - recall that decay heat falls off exponentially with time, meaning that after a few weeks, the heat emitted by spent fuel rods is much, much lower than that of a reactor which was just shut down. Thus, the loss of coolant would be much slower than that of Units 1-3.

During the crisis, some speculated based upon limited data (little to no actual instrument data from the pool was available due to the lack of power) that the water levels have precipitously dropped; NRC Chairman Gregory Jaczko even (now infamously) speculated that the pools had gone "completely dry."

However, recent images taken of the spent fuel in Unit 4 by the IAEA indicate that the fuel appears to be intact and undamaged; thus an uncovering of the fuel in Unit 4 appears to be extremely unlikely.

Fuel stored in the spent fuel pool at Fukushima Dai-ichi Unit 4. (Image credit: IAEA) 

In addition, the IAEA has tested for radioactive isotope concentrations in the water within Unit 4's spent fuel pool; in the event that the fuel became uncovered or fuel melted, telltale isotopes would be present to indicate this. Current analysis has failed to find these, further indicating that it is unlikely fuel was damaged at Unit 4. Finally, experts familiar with fuel chemistry indicate that radioactive ruthenium (a chemical in the lanthanide family and a common fission product which tends to travel with water) would have been present outside Unit 4 had fuel melt occurred, which has not been found.

However, the drop in the water level which occurred in Unit 4 is still an unknown (due to the lack of instrument measurements inside the building from the power outage) and difficult to determine; experts are currently attempting to perform back-calculations to estimate this.

Source of the hydrogen explosion

One source of speculation and debate was the hydrogen explosion which occurred at Unit 4, in particular how a hydrogen buildup could have occurred in the outer containment building around the Unit 4 spent fuel cooling pool. The presence of hydrogen is a clearly worrisome sign, implying that a sufficient amount of water has either boiled off or leaked to allow the fuel to become uncovered and grow hot enough to enable the hydrogen production reaction. (Fuel which is covered by water cannot get hot enough to allow the reaction between water and the zirconium clad to occur; therefore, the production of massive amounts of hydrogen would imply an uncovering of the fuel.)

Thus, the hydrogen explosion at Unit 4 lead some (such as Jaczko) to speculate that the spent fuel pool had gone "completely dry." However, no signs of fuel damage were observed, indicating that zirconium hydriding from spent fuel rods in Unit 4's pools was extremely unlikely.

Therefore, where did the hydrogen in Unit 4 come from? The IAEA believes that hydrogen may have been vented from Unit 3 to Unit 4 through a "standby gas treatment system" exhaust pipe; this exhaust tube had joint inputs from Units 3 and 4, thus conceivably allowing hydrogen to travel from Unit 3 (where it was being produced following the core becoming uncovered) to Unit 4 (where it subsequently ignited and exploded).

(Left): Standby pipe from Units 3 and 4; (right) Enlarged view of junction (Image credit: IAEA)

Releases of radioactive materials

Thanks to my colleague Alan's ability to read and speak Japanese, this blog has been following dose data around the plant and surrounding area from early on after the accident. However, the IAEA has helpfully compiled a map of further measurements which were taken by ground stations and measurements by aircraft.

Map of air dose plume release from Fukushima. Red: 9-91 microSv/hr,  Orange: 9.5-19 microSv/hr, Yellow: 3.8-9.5 microSv/hr, Green: 1.9-3.8 microSv/hr, Blue: 1.0-1.9 microSv/hr, Indigo: < 1.0 microSv/hr (Image credit: IAEA)

Air measurements conducted around the area of the plants indicate that much of the plume containing radioactive materials traveled northwest (i.e., due to wind); doses outside the main plume spread to the northwest were found to be relatively negligible. Likewise, with the exception of the plume "tail" in the northwest, nearly all of the elevated dose rates in air were concentrated within a radius of 30 km from the plant, calling into question the logic of NRC Chairman Jazcko's order for Americans within 50 miles (around 80 km) to evacuate.

Evacuation areas around Fukushima. (Image credit: IAEA)

As is clear from the evacuation zone map, the Japanese evacuation order of 20 km with a deliberate evacuation of Iidate and Katsurao prefectures appears to be based upon a sound evaluation of the measured exposure rates. Additional precautions in place (e.g., staying indoors and prophylactic measures such as distributing potassium iodine tablets) were implemented in areas within the 30 km radius.   

Approximately 78,000 people were evacuated from the evacuation area (20 km), with an additional 10,000 evacuated from the "deliberate evacuation area" to the northwest (a smaller number due to the relatively low population density in these areas). Residents in the "Evacuation prepared areas" were informed to stay indoors and prepare for a potential evacuation order in the event of further emergencies (e.g., large measured increases in the exposure rate).

Preventative measures

As a precautionary measure, potassium iodine (KI) tablets were distributed to residents within 50 km of Fukushima prefecture; 1.51 million potassium iodine pills were distributed to approximately 750,000 residents , while 6,100 grams of KI powder was distributed to 120,000-180,000 individuals. 

Potassium iodine is an effective preventative measure for exposure to radioactive iodine (I-129 and I-131) if taken prior to exposure. Iodine is readily taken up by the thyroid; thus, by flooding the body with stable iodine, any radioactive iodine ingested (due to groundwater and air transport) would be excreted out of the body before being absorbed. (Conversely, radioactive iodine is frequently used for the treatment of thyroid disorders, given that the radioactive dose can be easily targeted specifically to the thyroid.)

Evacuations and relative risk 

A point which must be emphasized again in evacuation decisions such as this is in the relative risk averted through evacuation versus the human costs imposed, particularly in light of an epic natural disaster such as this, with tens of thousands dead or missing and over a hundred thousand displaced. Overly conservative evacuations based upon marginal risks (i.e., outside 20-30 km) place an additional burden upon already strained emergency resources (shelters, medical facilities, etc.) while giving little additional benefit. Even under the best of circumstances (which clearly was far from the case here), broad evacuation orders can result in tremendous hardship; the gains from evacuation must therefore be balanced against the additional burdens imposed.

Relative amount of radioactivity released

Based upon calculations made of the measured activity outside the reactors, the IAEA made an estimate of the relative fraction of material released from each core. Nearly all noble fission product gasses (such as xenon and krypton) were released; however, these are of negligible concern, given the fact that they are chemically inert. Approximately 1% of radioactive iodine was released from Unit 1, with about 0.4 to 0.7% of the iodine released from Units 2 and 3. Finally, for other species (including cesium), less than 1% was determined to have been released into the environment; for Units 2 and 3, this was determined to be around 0.3 to 0.6% of the activity in the core.

Estimates as to the total activity released to the atmosphere put the activity of I-131 released around 1.5 to 1.6x10^17 Bq (one becquerel is one atomic decay per second), and around 1.2 to 1.7x10^16 Bq of Cs-137. (Note that not all of this activity was spread inward; large amounts of this release were likely dispersed over the ocean, where they are greatly diluted.)

Presence of transuranic elements 

One rather persistent rumor among media outlets and particular blogs was reports of transuranic elements (i.e., plutonium and other elements above uranium on the periodic table) being found in soil samples outside the plant, indicating a "blowout" of materials from the core similar to Chernobyl. (in the case of Chernobyl, the resulting fire lofted much of the fuel materials into the air, scattering them much farther than they would have otherwise traveled and allowing heavier species, such as plutonium, to escape).

The IAEA did find reports of small amounts of transuranic materials found near the plants from ground monitoring stations and groundwater samples, however these measurements were found to be inconsistent, with little sustained evidence. One difficulty is establishing a source for these materials, which are not necessarily from the plant itself, given the widespread dispersal of radioactive elements around the globe during the time of above-ground atomic testing. Testing for aspects such as the relative abundance of different isotopic species may help to determine the source (i.e., whether the material is older, such as from bomb testing, or newer), however given the relatively scarce amounts found, it has been difficult to establish a source for these materials, given that they conceivably may have precipitated from anywhere in the area.

Worker and resident doses received

Estimating doses for workers was found to be extremely challenging, due both to the lack of instruments at the facility (from the power outage) as well as the flooding, which either swept away or ruined many of the personal dosimetry meters worn by workers or stored at the plants. Of 7800 workers measured, the average worker dose was about 7.7 microSv (well short of the yearly dose limit); 30 were found to have doses greater than 100 milliSv, while 2 workers were found to have equivalent doses to the skin of about 2-3 Sv (due to contact with radioactive water in flooded buildings, causing minor skin burns similar to a sunburn).

Estimation of doses received by the public was measured primarily by the level of surface contamination (i.e., number of radioactive counts per minute). Most of the 195,354 individuals screened were found to be below the 100,000 counts per minute limit; of those who were found to be above this limit, most of these individuals had residual contamination on clothing only and were cleared after changing clothes and vigorously washing their skin.

Accident classification

One question which came up was in the choice (and chronology) of the accident classification of the Fukushima incident, initially placed as a "3" on the INES scale and moved to a "4," then a "5" (similar to Three Mile Island) and then finally upgraded to a "7" (similar to Chernobyl).

INES accident classification scale (Image courtesy of IAEA) 

With respect to the accident classification, the choice of a classification of "7" (the most severe accident category classification) seems somewhat confusing in light of the limited consequences of Fukushima compared to Chernobyl (whose overall total radioactive releases were nearly ten times that of Fukushima). However, the accident classification itself was based upon the total activity of materials released (e.g., very short-lived materials, while quickly going away, will have a higher relative activity rate), including those released into the ocean (where the effect would be relatively dilute). Thus, the application of a "7" rating was a strictly mathematical decision, based on the threshold value for total release.

On the other hand, the sequence of classifications was a more delicate political matter. As evidence surfaced of the situation growing more severe, TEPCO and the Japanese government were continually required to update the accident classifications. (Likewise, there appeared to be a certain reluctance on the part of TEPCO and others to disclose the full significance of the incident). As the situation progressed, it was clear that TEPCO and others would simply need to concede the severity of the conditions, re-classifying the accident as a "7" in order to "get ahead" of the situation, rather than being seen as continually dissembling[?] and delaying. In as much, while the final classification itself was based upon total measurements, in the IAEA's view the chronology of how these ratings were assigned as the accident unfolded were influenced by concerns over public perception.

Plans for improvements

Much of what will occur in the aftermath of Fukushima will be to determine how nuclear operators can plan for and respond better to similar circumstances in the future. Much of the problems encountered at Fukushima came from the total loss of power at the facilities, followed by the destruction of the backup diesel generator units in the tsunami (a condition known as "station blackout," the worst possible circumstance which can occur at a plant).


Thus, many of the IAEA's recommendations fall under these categories. In addition to recommending that operators and plant designers harden facilities against earthquakes and floods, a key area of focus will be in ensuring that reliable backup supplies of power can be maintained in order to operate cooling pumps following an unexpected plant shutdown. This includes hardening backup generators (placing them out of reach of flood waters) and making dedicate contingency plans such as mobile power vehicles to supply power in the case of a generator failure.


Other factors include features such as means to mitigate hydrogen production in circumstances such as this, through the installation of hydrogen "recombiners" (which steadily burn hydrogen rather than allow it to accumulate) and dedicated "blow-out" panels to allow for emergency venting of hydrogen from the outer containment buildings. It was noted that over 300 metric tons of hydrogen was produced in the three reactor units (in other words, over 300,000 kilograms), thus leading to the rather dramatic hydrogen explosions witnessed.


Other recommendations focus upon measures for emergency response, such as procedures for handling nuclear emergencies. A particular complication in the case of Japan was in the widespread devastation beyond the scope of the plants themselves; many workers at the plant were uncertain about the safety of their homes and families, leading to confusion and initial difficulties in maintaining sufficient staff levels to respond to the emergency at the plants.

Proposed safety systems upgrades (click for larger version; image credit: IAEA)

Finally, the IAEA recommends regulatory reforms such as instilling a more thorough safety culture and reinforcing the regulatory safety infrastructure by fostering a greater separation of regulators and utilities, which have been frequently criticized for enjoying too cozy of a relationship in Japan. An additional criticism made was in that preservation of economic assets (e.g., the reactors) was potentially prioritized above safety in the early stages of the response, delaying such measures such as seawater injection (an emergency measure to cool the core which almost certainly would mean a total economic loss for the reactor unit).

Final thoughts

Nuclear safety is a constantly-evolving process; the events at Fukushima will undoubtedly be studied by engineers and scientists for years to come in order to develop better safety features and response techniques to ensure maximum possible safety to the public. To some degree however, there comes a point where one plans against the essentially unpredictable (for example, a record earthquake and tsunami); thus, not every measure can simply be preventative in nature, but rather in how to respond to and mitigate such events. (Examples of this include hardening backup generators and designing robust containment buildings to prevent radioactive releases.)


It likewise is useful to place events like this in context; while it is clear that Fukushima was an extremely serious event in hindsight (it would now appear to be far more serious than Three Mile Island, although less serious than Chernobyl), the consequences must be compared to the risks encountered by the available alternatives. For example, one consequence of the earthquake was the destruction of a hydroelectric dam, destroying over a thousand homes. Liquefied natural gas facilities were also destroyed in the earthquake, leading to further casualties. By comparison, the only person who has died as a result of the Fukushima disaster was not even killed by a radioactive release, but rather was killed by a falling crane.


Risk is an unfortunate fact of life, and in particular of energy production. This applies to all forms of energy production, not just nuclear - each form of energy production comes with equivalent risks and trade-offs, including economics, pollution (for example, the radioactive releases from coal plants in smokestacks are far higher than that of nuclear plants), land utilization (diffuse energy sources such as solar and wind consume enormous land footprints), etc. There is, alas, no "free lunch" when it comes to energy. The best that we can hope for is to understand and minimize risks by constantly striving for better and safer designs and better ways of responding to accidents.


In particular, it is worth noting that the Fukushima plants were of a prior vintage - built in the 1960's and nearing retirement. Newer plants built at Fukushima Dai-ini did not suffer nearly the same consequences as those at Dai-ichi, in part due to enhanced safety features within the designs. Likewise, plant designs being proposed today take advantage of decades of engineering experience, including advances in technology (particularly in advanced computing - perhaps the most amazing thing about much of the existing nuclear fleet is that it was designed with pencils and slide-rules...). New designs such as small modular reactors promise further enhancements in safety.


Ultimately, safety will be an ongoing challenge, one not entirely technical in nature. After Three Mile Island, one of the most radical changes to the U.S. nuclear industry was a focus on human factors - particularly looking at aspects such as instruments in the control room, operator training, and instilling a safety culture. Similar lessons may ultimately have to be internalized in the case of Japan.


It has often been said, "Experience is the harshest teacher, and her lessons the most expensive." For the Japanese, no doubt this case is little different.


A special thanks to Randy Beatty and the IAEA for both presenting and making these resources available to me.

Small Modular Reactors and the Economics of Nuclear

My colleague (and member of my dissertation committee) Dr. David McNelis had an excellent Op-Ed in the Raleigh News and Observer yesterday touting the safety and economics advantages of small modular reactors (SMRs). A snippet:

In contrast to a conventional nuclear plant, SMRs could be added one at a time in a cluster of modules, as the need for electricity rises. The cluster's costs would be paid for over time, softening the financial impact.

The modules could be factory assembled and be delivered by rail to an existing nuclear plant site. In such a configuration, one SMR could be taken out of service for maintenance or repair without affecting operation of the other units.

Most SMRs would be situated beneath the ground to provide better security. Typically they would operate for many years - possibly decades - without refueling and produce far less waste than conventional reactors.

Significantly, almost all of the SMR development is being done with private financing. Companies are using their own resources to develop the small reactors, without government support from mandates or subsidies of the sort that renewable energy sources now require.

As the kids say, do read the whole thing.

SMRs are an interesting, potentially game-changing addition to the nuclear energy market in my opinion, namely due to their ability to overcome one of the chief barriers to the rapid deployment of nuclear energy units right now: high capital costs.

Prohibitively high capital costs (most new reactors are starting with price tags around $4 billion or so) present utilities with a double-whammy of sorts: first in that raising so much capital is in itself a difficult undertaking, particularly compared to the total capitalization of the types of utilities making these investments. (This is where the typical rhetoric about "betting the farm" comes into play, despite the fact that the low fuel and operating costs and very high capacity factors make nuclear units veritable cash cows once electricity begins to flow. Ultimately, such investments require tying up a large portion of an individual utility's assets for several years before any money is generated.) Second, due to the large amounts of money involved and generally long construction times, utilities get hammered on costs by paying interest upon interest; in other words, interest accrues on money they borrow from the moment construction begins, meaning that the "cost of money" is a rather significant factor in nuclear construction. Finally, given both the large amounts of money and extended timelines involved, investors will thus typically demand a "risk premium" - similar to the kind of interest rate premium an ordinary borrower without stellar credit would have to pay on bank loans an credit cards. This too can significantly raise the cost of capital for building new units.

Each of these factors thus conspires to keep many smaller players out of the market. Instead, many have sought to invest in smaller, more scalable alternatives such as natural gas, which has nearly the opposite economics of nuclear: low capital costs (i.e., each unit is of a relatively small capacity and can be built quickly) and relatively high fuel costs as a fraction of the cost of electricity. (While nuclear's fuel cost for electricity is around 10%, natural gas can be around 70-80%). Nor has the price of natural gas ever been historically stable (at least in the last 15 years).

Unless, of course, this is your definition of "historically stable." (Source: EIA)

SMRs have the potential to change the economics of the game by several means. First, many proposed SMR designs are engineered to be mass-produced and pre-fabricated in factories, rather than built on-site. This could tremendously push down prices while also shortening construction times, thus ameliorating what is currently one of nuclear's biggest weaknesses at the moment.

Meanwhile, the "small" in SMRs also may have potentially positive implications for both cost and safety: SMRs can be potentially built into the ground, using the surrounding earth as containment, due to their relatively small size. Given the lower total power and nuclear material within the reactor, it can be said to have a lower overall "radiological footprint," meaning simplified safety planning.

Finally, the "right-size" power of SMR capacity may allow them to be sold in a greater number of markets - places both where a new full-sized reactor is too big for the needs of a community (for example, Fort Calhoun, north of Omaha, is the smallest reactor in the U.S. nuclear fleet, clocking in at only 500 MW; compare this to currently proposed new reactor designs, which begin in the neighborhood of 1000-1100 MW). Likewise, the smaller size means that for utilities only looking to incrementally expand capacity, small reactors may prove to be competitive with alternatives such as natural gas turbines.

One point which I think nuclear advocates tend to allow themselves to be blindsided to at times is in the fact  that above all else, it is economics which will ultimately determine the future of the nation's electricity portfolio. Factors like politics certainly come into play (particularly such issues as energy portfolio mandates, etc.), and likewise factors such as safety can never be understated. Nor should public acceptance ever be ignored, much as it has to the industry's peril in the past. However, those ultimately committing the funds to expand energy sources are the utilities, many of whom answer either directly to shareholders or to ratepayers. In this regard, they have an obligation in either sense to produce power as profitably or affordably as possible.

Thus, the decision for utilities will always ultimately come down to economics, something that nuclear advocates cannot simply ignore. I don't necessarily doubt the assertions of fellow advocates such as Rod Adams, who assert that fossil fuels have a strong interest to defend in continuing to sell their products. (Although I will say that I also don't necessarily buy the idea that those who argue natural gas is currently more economical based on short-term factors are necessarily on the fossil fuel dole, either.) But the fact remains - for nuclear to succeed, it must be able to compete, head to head, dollar for dollar.

Nuclear energy has tremendous advantages to offer, in that is clean, abundant, and easily the most energy-dense source we have available at our disposal. Yet at the end of the day, decisions over energy investments do not necessarily come down to these factors: they come down to economics, and often (regrettably) economic return over the short-term. This may be where SMRs ultimately change the game for nuclear, then - namely, by bringing the advantages of nuclear to bear in a more economically attractive package.

Why I'm not worrying about Fort Calhoun (and you shouldn't either)

Given the recent flooding along the Missouri River and my own personal connection to the area, I've been following the news regarding Fort Calhoun (or "Fort Kaboom" as it is sometimes pejoratively known) with a great deal of interest. (Likewise, I'm sure several readers of this blog from the area are doing the same.) And of course, given recent circumstances, some degree of misinformation is to be expected, particularly from those pushing an agenda.

In particular, there have been reports (of rather dubious origin) claiming that Russia's Federal Atomic Energy Agency (FAAE) is reporting that the International Atomic Energy Agency has provided them information on a supposed "information blackout" regarding conditions at the plant, including a "potential near meltdown condition." Never mind of course that the plant has been in a state of cold shutdown (i.e., no power being produced) for over a month (since April 9th), given that it was under a scheduled outage for refueling and maintenance when the flooding began. In other words, a "meltdown" in the sense of Three-Mile Island (or even Fukushima, in which the core was shut down immediately after the earthquake) is physically impossible.

Further, a brief review of the IAEA's website reveals no such alarming news. In addition, any large radiation releases from the plant would be immediately detected by any number of independent radiation monitors not under the control of the NRC, thus making any claim that the administration has somehow orchestrated a "media blackout" all the more laughable. (Not to mention the sheer implausibility of such a blackout, considering the government's inability to control other recent releases deemed sensitive.) More than a grain of salt would be warranted, here.

Other claims include that a brief control room fire has lead to a catastrophic loss of power to the pumps circulating cooling water to the spent fuel cooling pools, inviting the inevitable comparisons to Fukushima Daaichi Unit 4 (e.g., where water levels became a concern after several days following the earthquake). However, the NRC has reported that the fire was quickly contained and that power was restored. Further, unlike Fukushima, while the flooding is most serious, operators are not facing the crisis situation at Fukushima, which involved a total station blackout and a struggle to cool three recently shutdown reactors, all while dealing with the natural devastation from a record earthquake and tsunami. In other words, the situations don't even remotely compare.

The NRC's blog recently deflated several ongoing myths regarding Ft. Calhoun, including the following:

• The FAA has not "closed" the airspace over Ft. Calhoun*. The airspace above domestic nuclear plants has been restricted as of September 11, 2001 for security reasons. Given the attention on Ft. Calhoun, OPPD requested that the FAA issue a "gentle reminder" to pilots regarding this fact.
• The brief control room fire did briefly interrupt power to the spent fuel cooling pumps, but these pumps are not currently offline, nor is there currently a danger of the spent fuel pools boiling over and exposing the fuel rods.

Other rumors include the idea that somehow Ft. Calhoun will be overrun by the rising flood waters, thereby washing away the backup diesel generators and producing a similar station blackout condition as experienced by Fukushima. However, several notable differences exist. First, a flood is a far slower, far more predictable process than a tsunami; as a result, operators have had more than adequate time to prepare earth berm flood defenses at the plant. These defenses were erected per federal guidelines well before the flooding began. Second, the backup power generators at Fort Calhoun are in hardened structures (again, unlike Fukushima), minimizing the overall risk of a total "station blackout" condition.

Fort Calhoun Nuclear Generating Station (Image credit: AP)

In addition, Dan Yurman at Idaho Samizdat has also been busy spiking the rumors regarding Fort Calhoun. Among other things, he reports that the earth flood walls provide protection for another 5-foot rise in floodwaters (currently at 1005 feet); the diesel generators have an additional foot of protection from flooding. 

One of the chief things to keep in mind in all of this is that natural disasters aren't something which is simply neglected by nuclear plant operators; in fact, quite the opposite. Given the Missouri river's history, contingency plans against cases such as this are part of the standard operating protocol for any plant like Ft. Calhoun. Given that, my own personal concern is far more focused upon the fact that the reported flooding could last for through August, drastically impacting eastern Nebraska and western Iowa.

*Update: As one reader points out, OPPD has requested additional temporary airspace restrictions over Ft. Calhoun, banning all aircraft in a radius of two nautical miles (about 2.3 miles or 3.7 km) under a flight altitude of 3500 feet. (In other words, low-flying aircraft.)

Why I became a nuclear engineer

In celebration of the fact that I will be conducting my final defense for my doctorate in nuclear engineering next Friday, I wanted to change gears a little bit and take on a bit more of a personal subject. Namely, I'd like to talk a little bit more about why I chose to go into nuclear engineering in the first place.

Nuclear advocates like Suzy Hobbes and the Nuclear Literacy Project have spoken about the need to put a human face to nuclear engineering. My own hope here is to perhaps inspire a conversation among many nuclear professionals, each of whom have had their own path into nuclear energy, as both engineers and advocates. I'll follow up on this post with links to others' responses as they roll in.


In the beginning...


Unlike many whose views on energy were shaped by the Oil Crisis of the 1970s, I was born much later (well, perhaps not that much later). Late enough at least that the specter of large-scale energy shortages seemed like distant history to me growing up. Nor did I take the path of many who came into nuclear engineering through the nuclear navy (although I did consider the option at the time). In that sense, you might say that my experience is perhaps more representative of the newer generation of nuclear professionals entering the workforce, those born in the 1980's (like me) and 1990's.

For me growing up, nuclear energy always seemed like a bit of an underdog, having been born between the time of Three Mile Island and Chernobyl. Nuclear technology held untapped promise of plentiful energy whose time essentially came and went. I grew up in the time where nuclear power plants were a lot like classic cars: beautiful to behold, but they just don't make 'em anymore. (Incidentally, where I grew up received about 20% of its power from the now currently-famous Fort Calhoun nuclear plant). The 90's were generally a time where nuclear energy was viewed as being on the downward slope: not a single new plant had been built in the U.S. since I had been born while enrollment in university nuclear engineering programs was in a slow decline.

Suffice it to say, a career in nuclear energy didn't exactly seem like a viable career option at the time. This began to change just around the time I started my undergraduate years, but the "Nuclear Renaissance" was still well-off in the horizon at that point.

"Nuclear power is great, but..."

Meanwhile, nuclear power, when not associated with the bumbling Homer Simpson or the barely-operational Springfield Nuclear Power Plant, it was spoken of in terms of the ultimate intractability: how to deal with spent fuel waste. In other words, "Nuclear energy is great, but what do we do about the waste?" It is perhaps the most prevalent question many of us encounter even still today.

Among my friends and colleagues in physics, nuclear energy was generally viewed in very favorable terms - lovable but misunderstood. It was a working assumption that nuclear power was safe - this was science after all, and science we'd done half a century ago (even if the public didn't get this). Yet even our conversations turned inevitably to, "But what do you do about the waste?" Being physicists, we appreciated quite well the long-term nature of the half-lives of actinides in spent fuel (such as plutonium, neptunium, and americium). And of course, being physicists, we had all kinds of crazy solutions.

"Well, couldn't we just blast it into the Sun?"
"What if we buried it a deep ocean trench?"
"How about we ship it to Antarctica?"

Needless to say, I was actually a little shocked when these options actually came back up once I was taking a waste management class as options which were considered but otherwise seen as impractical. (Namely I was shocked because these were ideas being tossed around by smart people who otherwise knew very little about nuclear engineering overall - we just liked the idea of a thought problem.)

It wasn't until much later that I would by chance read an article in Scientific American talking about the untapped energy potential in nuclear fuel, and in particular how much of what we consider "waste" is in fact a recoverable resource. By mass, about 97% of "spent" nuclear fuel is recoverable - and with these recoverable elements taken out, the bulk of the toxic radioactivity is gone after around 300 years, rather than over millions of years.

At that point, the potential for nuclear energy seemed blatantly obvious to me, having that issue solved. I began to become a more passionate advocate; my greatest frustration overall was simply, "Why are we not taking advantage of this?" But even still, the business of building and operating nuclear power units was for someone else - I was still a physicist, after all.


"Very interesting. So how does that help people?"

Going forward a few years to when I was finishing my master's degree in Nuclear Physics. It was the mid 2000's by this point (so you can probably guess my age by now). I was happily at work involved with an experiment at the Relativistic Heavy Ion Collider (RHIC), looking into collisions of heavy particles to try and unravel some of the secrets of what fundamentally makes up atoms at the sub-atomic level, and ultimately where all matter in our universe came from.

This of course was pure science at its best: deep mystery, fundamental questions, and absolutely zero immediately foreseeable practical applications. It was first and foremost simply about satisfying a deep curiosity. And of the wonders of this work, I was a tireless evangelist, trying to impress upon anyone and everyone I could about the deep wonder about the mysteries we were unfolding. (This would include even the woman who would become my wife - the very fact that she tolerated my rambling about this research during our first date and actually agreed to go on a second indicated she was a keeper...)

Around that time, I was spending a holiday with my extended family nearby, proselytizing about the wonder and mysteries we were investigating. One of my older cousins listened with polite attention, and when I was finished, he asked me, "That all sounds very interesting. So how does it help people?"

At the time, I gave a rambling and not very convincing answer about how science leads us to unexpected developments. It was of course true, in a sense - for example, much of what we consider a mundane part of our modern lives now trace their existence back to the development of quantum mechanics; specifically, anything involving a semiconductor (which of course includes computers, cell phones, and all other forms of digital electronics).

The question lay dormant in me for a long time, however, festering every now and then. I couldn't help but think that I wanted to do something with my career to make a positive difference in the world. And while scientific discovery was both interesting and fulfilling, how it "helped" people was mostly a vague abstraction.

When I was a young child, my first ambition (before wanting to be a physicist) was to be an inventor - namely so I could help to invent things that would one day truly help create a better world. My ideas were ultimately not that great (although who can really blame an eight-year old for that?), but the fundamental motivation was still there.


From physicist to educator...

I left graduate school and went in a different direction for awhile, becoming a science educator at a museum in Chicago. My thought was that perhaps I could use my love of science and teaching to reach out to people and show them some of the wonders of the world, even perhaps to help inspire the next generation of scientists and engineers. My sense of childlike wonder was still quite infectious - it was truly easy, a joy even, for me to find the energy and enthusiasm to explain just how awe-inspiring the universe around us is and how we are just beginning to understand it. I loved teaching; I truly enjoyed being a teaching assistant in graduate school and I loved teaching anyone who would listen (especially children) about the wonders all around us in the universe.


...to engineer...

One thing that struck me while I working as an educator was a series of lectures by climate scientists being held at the museum (particularly with the focus of how satellites were just beginning to paint a picture of climate change). I'd never really been one to doubt the idea of anthropogenic climate change in general (the basic physics, after all, seemed dead simple to a physicist or anyone who'd spent time with a hot car in summer); only the degree of which was ever really in dispute for me.

At this point, the severity of the issue began to seem inescapable to me. I was first and foremost a scientist, and perhaps still a bit of an inventor - what was I doing about this? How would I help?

(To make bit of an aside here - my politics and personality don't exactly make me the stereotypical environmentalist and/or sandal-wearing hippie. Throw out the term "organic" and I'm as likely to roll my eyes; mention "alternative medicine" and I'll likely start to grumble about hippie nonsense. But it's hard not to look at  what appears to be fairly obvious science when it comes to climate change and not be just a little worried.)

I remember looking over Lake Michigan at the Chicago skyline at night, seeing a glimmering monument to the abundance and progress that plentiful energy had brought us. At that point, it seemed obvious: the only way we'd ever be able to seriously confront the issue of carbon emissions while continuing to maintain anything close to our level of prosperity was to begin to seriously embrace nuclear energy in earnest. Nothing else could provide both the abundant level of energy that our economic prosperity has come to depend upon while  staving off an eventual ecological catastrophe. Even then, I was skeptical of wind energy (the availability and energy density alone made it seem impractical), solar seemed like a distant pipe dream, and so-called "clean coal" an absolute lie. And the alternative - essentially asking people to live in caves, eschewing modernity altogether - was unthinkable.

By that time, I had a voracious interest in the Generation-IV nuclear designs then being touted - concepts like the Very High Temperature Reactor (VHTR), which could produce energy at much higher efficiencies and even perhaps be used for process heat in other applications like hydrogen (remember the "hydrogen economy?") or the pebble-bed reactor, which promised the ultimate level of safety. Nuclear technology was actually something new and exciting to me once more - and I wanted to be one of its pioneers.

And so with that I threw the dice - leaving a stable job for a complete risk, going back to grad school and not knowing what the future might hold


...to nuclear researcher

Of course, in my wild enthusiasm, what I perhaps would overlook was the fact that despite the fact that the Nuclear Renaissance was in bloom, we still weren't exactly building that many new reactors, and Gen-IV reactors were a decade or more away from even being remotely commercial concepts. And of course, like many kinds of "sexy" science, I'd also overlook the fact that the real beginning "design" work was already done; they didn't need people to design Gen-IV reactors, they needed people to run simulations on aspects like how neutrons are created and absorbed, as well as "thermal hydraulics" (i.e., where heat is created in the reactor and where it goes). Having absolutely no background in nuclear engineering, it was a task I wasn't even remotely qualified for at the time (despite my training as a physicist). It also lacked some of the urgency that I (rather naively) came in with.

It was perhaps a twist of fate that the director of graduate programs at the time I interviewed at NC State would be the person who would later become my adviser; or, incidentally, the reason I was admitted to NC State to begin with. (My undergraduate academic record he described dismally as, "not very impressive," but he took great notice of my passion; it was ultimately this, and the potential for research that he saw in me, that lead to his decision to recommend my admission.)

My adviser is perhaps a bit of an outlier in terms of personality, much like me. Beyond the simple technical challenge, at his core he is someone who is driven by ethical concerns - especially in terms of how we can make a better world, leading him into nuclear engineering, and particularly his focus, which focuses more upon what one might call the "social" issues of engineering, such as public perception of risk, nonproliferation and safeguards, and nuclear waste management. I realized working with him that there still were challenges to be solved, with the potential to do enormous good in the world.

This is where I would develop a passion for challenges like how we can close the nuclear fuel cycle by recovering the long-lived elements in spent fuel, rather than throwing it all away intact. This as well struck me as the place where I might be able to make a real positive difference, helping to finally clear the path of the last barriers to the much broader deployment of nuclear energy.

Even now, in my view, the issue of nuclear waste management is the last true barrier to widespread public acceptance of nuclear energy. Despite everything that has occurred with Fukushima, I believe that the reactors we have now and more importantly, the reactors we will build, are fundamentally safe, and will continue to get safer with the advance of technology and experience. Thus, it is not fundamentally an issue of safety that stands in the way of nuclear energy development, but a public understanding that we have a plan for spent fuel beyond simply dumping it all into a (very well-studied) hole in the ground and hoping for Mother Nature to do her best. (Please don't mistake me - I think Yucca Mountain was by all accounts technically sound - just also a tremendous waste.)

Of course, what I know now is that closing the nuclear fuel cycle is also not strictly a technical problem - it is one with a wide array of social, political, and economic challenges. But some of these problems too can be attacked via technical means - namely by investigating ways to make reprocessing cheaper and easier and developing solutions to allow us to guard against its potential misuse.

In that sense, so many years later now, I can finally answer my relative's question with a much greater degree of confidence. It's why I'm passionate about what I do - because from my perspective, this is what I can do to leave a better world for my children and their children. And I'm sure I'm not the only nuclear engineer who thinks this way.

So it's with some excitement that I look forward beyond next week, to the point where I truly begin my career as a nuclear engineer... and scientist.

Small Nuclear Reactors are Needed for Charter Cities of the Future

What's the difference between North Korea and South Korea? How about Hati and the Dominican Republic? And what's the major difference between China last century and today? Stanford economist Paul Romer thinks he has an answer:

Bad Rules versus Good Rules

Bad laws and policies (rules) prevent win-win situations. They are almost ubiquitous in all nations with stunted economic growth. One of Dr. Romer's examples is electricity - many people in the world are prevented from getting hooked up with electricity due to bad rules that govern the electric grid, the buying, and selling of power. It's not hard to imagine how this can happen. The "old fashioned" way of structuring an electric grid is generally a regulated monopoly (USA) or a state-run operation (UK). In Dr. Romer's example, when the price was set too low for the company to make a profit, they had no incentive to expand the infrastructure, and those paying the price had no incentive to lobby for something different.

Some places have been testing the waters with a different set of rules in the electricity market, a common structure today is a so-called "Independent System Operator" that runs a market which others feed into and participate in. In the future, small investors could gain access to this market through the smart grid. Innovations in real time pricing could allow a system of rules that lets everyone participate in the management of our power distribution and production. Unfortunately, history has examples of bad rules in the electricity market as well.

The nuclear industry in the United States is no stranger to the consequences of bad rules. There are a host of reasons for the slowdown in nuclear plant builds in the USA at the end of the 70s, but the most powerful one is that the investors couldn't count on the rules not changing. As the regulatory process was changing quickly, there was no guarantee that the design you commit to at the start would be good enough by its finish. No decision was final, and everything was subject to a change later, political or otherwise.

So what's the deal with charter cities?

You start with a Charter. It specifies the rules, and these have to be good enough to attract investment in the new city. The model has to have choice built into it, which is why it is being proposed for uninhabited land. Some amount of foreign, or international, administration is utilized and ease of doing business is maximized. Hong Kong is said to be a historical example of this, and it had tremendous influence on the rest of the nation and the world. It offers opportunities to the poor by allowing them a way to hurtle the numerous institutional problems that are holding them back. This is what Dr. Romer laid out in his 2009 TED talk.

Since then, the idea has gained traction, and the Honduran congress has passed a constitutional amendment to establish just such a charter city (a "special development region", as of yet agnostic to location) with a stunning 124-1 vote, twice. This will give people in Honduras a choice. Many people who would have otherwise migrated to the United States (as 10s of 1000s do now), will instead choose to move to this new city that has the same kinds of opportunities. He just delivered another TED talk about this:

Also see:
http://chartercities.org/

Supposedly, you need around 1,000 km² for such a city (you may need 100 km² just for the airport). Honduras supposedly has plenty of empty space that can be a blank slate for such a city.


But the idea is not without its problems. We all understand that cities are higher density and can be more eco-friendly because of that, but what about the invisible supply chain for a city? Where are you going to get all the materials, food, electricity, and all other inputs that must come from the land to supply the city? Plus, when we consider the nations that prospered because they had good rules, life got better and people inevitably used more electricity. Much more. Where will all that additional electricity come from? And how can we possibly get it without destroying more beautiful land like we set aside for the city itself? How do we keep a new city from destroying an environment many times its size?

Just imagine a dozen charter cities blooming around the world in the next 2 decades. Imagine the millions, maybe billions, of people they could lift out of poverty. Maybe we can even imagine powering these cities by a clean energy source that destroys no more land.

Nuclear Power + Rising Economies = The Way to Go

The entire nation of Honduras has a population of about 8 million and consumes on average about 750 MW of electricity. Imagine a new city with 1 million people. If they consume at the same intensity as Hondurans do now, that would be 100 MW. If they consume at the same intensity as people in the United States, we are looking at 1,500 MW average.

Consider the Flexblue - a small nuclear reactor design in development by a few French companies. This one could see market in the coming decade like many small reactor designs, but this particular one would be underwater. The modules would produce 50 MW to 250 MW of electricity each and could be grouped together. They would be 60 m to 100 m underwater "a few km" offshore. Think about that, this image shows a generating station sufficient to power the city we're talking about.


What would this look like? I tried to piece this together somewhat true to scale, and this is what I get:


Actually, I had to go a little further out to get ~200 ft depth since this area seems to have a particularly shallow coastline. The transmission also presents no particular problem, as we use undersea cables for just this type of thing today. What about the exclusion zone? Done. Emergency planning radius? A 10 mile radius for this extends about as far as the coastline in my picture. Also consider the inherent safety available from the abundant coolant source of the ocean. Even should a Fukushima-like accident occur there, the Iodine, Cesium, and Strontium would spread through the ocean, and not through the air. Where does Honduras get its electricity from now? It's 36% from Hydroelectric, 3% from biomass, and 60% from conventional thermal plants.

Finally, why would , or why would this not, work? Rules. It's no mystery that such charter cities would be powered, initially at least, by foreign direct investment. It's likely that the same would apply for a power source. Like every piece of infrastructure, no one will invest if there are not good reliable rules for the project. Although this goes for everything related to the charter city project, good rules for nuclear power development and considerably harder to come by in this world.

An interview on nuclear with a local student

I recently did an interview with a local high school student (name withheld for privacy), and I wanted to share my responses both in that there's several good questions, and more importantly how outreach efforts like this are essential for nuclear professionals. I've tried to keep my answers at a relatively accessible level, so if it seems like I am perhaps glossing over some of the finer technical details, it's because my goal here was to make my response accessible to as wide of an audience as possible.
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(On a side note: I apologize for the recent lull in postings - in particular, I've been bogged down trying to complete my PhD dissertation, with a defense date in approximately three weeks. As you can likely surmise, it's been a little busy here. More updates to come soon.)