* Note: I’m pleased to announce a new animated graphic of Fukushima radiation regional effects. Click here.
New Updated map – March 30th
Updated Commentary (March 30th)
The new map incorporates many of the changes requests by readers, while new features include a time series visualization of regional effects, a local site map, selected news reports, and data up through March 30th. Radiation by distance has also been updated to show several trend lines at different dates.
The time series data provided by Marian Steinbech, “A Crowdsourced Japan Radiation Spreadsheet”, was visualized with custom C/OpenGL software to overlay circles on geographic maps of Japan. Recent versions of the data, going back to March 1, can be downloaded from his blog here: http://www.sendung.de/japan-radiation-open-data/. These moments in time were selected to highlight how the radiation has effected Ibaraki prefecture and Tokyo, and demonstrate that while direct gamma radiation dissipates with the square distance law, particle-based radiation also dissipates with distance due to weather scattering. Although much attention has been placed on Tokyo, a very interesting finding was that Ibaraki prefecture, population 2.9 million, has received a radiation dose equivalent to nuclear worker levels while its distance from Fukushima, 100km, places it outside the current evacuation zone of 30km.
From March 17th to 30th, despite media reports which vary widely, indications are that radiation levels continue to decline. Of course, the reactors are still not completely stabilized, so future events are unknown. A significant problem is that huge amounts of seawater pumped in to control reactor temperatures must be discharged somewhere, thus ocean and nearby water measurements have increased significantly. This may be expected to continue so long as large amounts of seawater are pumped in to keep the reactors cool.
Overall, the most concerning factor is the difference between Western and Eastern responses. In the western media, very minute levels of radiation in Nevada and California are presented as if they are a major risk, which is clearly unfounded. Levels may be reported as “two times above normal” in a US city, but the overall background radiation of the world varies by up to 10 times! (0.5 to 5 mSv/year). Even in Tokyo, 206 km away, levels have not yet gone over the equivalent of adding a single CT Scan for the year. Yet the levels are presented as if they are an imminent threat to the west. Meanwhile, in Ibaraki prefecture (100km away), an area with over 2 million people may be exposed to levels unsafe for nuclear workers while the evacuation zone remains at 20km. The total number of people who have died from the earthquake and tsunami is now at 10,743 confirmed dead and 17,443 still missing (likely dead), which is usually reported as an after-thought in new media, while the total number dead from Fukushima nuclear radiation is still less than 100.
News reports, also plotted above, present an inconsistent view of events. Although only 12 articles are plotted in the map above, over 64 articles were reviewed for data accuracy. Some of the key findings are as follows. The most significant problem media faced appears to be how to correctly report radiation levels, which has been inconsistent both in terms of units of measurement, other levels to compare to, and background levels for reference. Friday, March 18th, “A radioactive hazard zone? Chernobly’s example” (CNN), they compare lifetime amounts of radiation in 1 km areas near Chernobyl (350 mSv) to momentary peak radiation levels at the main gate of Fukushima (400 mSv), and thus suggest that recent events are higher. The distances and time spans are not given, only the levels, thus giving an inaccurate picture of events.
On March 25th, several news agencies reported levels at 10,000,000 times above normal. The following day, a retraction was posted in an article called “Utility retests reactor water after radioactivity spikes”. In this follow up, the corrected report says levels were 100,000x above normal at Fukushima, 10,000x above normal at Reactor #3, 1850x above normal at a nearby monitoring post, and 330x above normal for the average person. What does it mean to be 100,000x above normal, and why is this number exactly one hundred thousand? Actual radiation units are never used, and in many cases the baseline upon which this multiplying factor is derived are never given. The entire concept of reporting levels “above normal” is misleading since it fails to address the fact that radiation is cummulative, and thus the duration of time that one is exposed to a given level is of key importance. In FOX News, out of several dozen articles reviewed, only a few provide actual sievert levels, while most articles indicate levels as a factor “times above normal”.
In an article on Wed, March 23rd, FOX news reports “Japan Commission Estimates Elevated Radiation Outside 30-Km Radius”, where they state that:
“In some parts of cities and towns more than 30 kilometers northwest and south of Tokyo Electric Power Co.’s (9501.TO) Fukushima Daiichi nuclear power station, people may have been exposed to a total of more than 100,000 microsieverts of radioactive iodine since the beginning of the nuclear disaster following the March 11 earthquake and tsunami in Japan, the estimate showed.”
This suggests that people outside the 30km zone have been exposed to 1000 mSv/hr (milli-sieverts/hour). Looking at the map above, this is clearly impossible, as this is the highest level reported directly near the core. If this amount of radiation were found in the surrounding areas, severe radiation sickness would already have been recorded.
Another reporting phenomenon is the unintentional amplification of disaster. On March 22nd, NHK world (a Japanese news source), reports that soil levels 25 miles away are 430x above normal soil levels. They also state clearly that the average exposure to a human being is likely to be only 4 times above normal. In a follow up report by CNN, on the same day, and apparently in the interest of providing a brief summary, this later clarification is omitted. The report states only that soil levels are 430x above normal, which presents an alarming figure. This article is then picked up by smaller networks and outlets, such as Village Voice, that reports a news snippet which states “Japan records soil levels 430x above normal 25 miles away”. The ultimate effect is that western readers receive a greatly amplified report of the disaster.
On March 23rd, based on analysis, Bernie Rano reports in a live interview that “There will be no big impact at all in the United States. This is not damaging radiation in the US.” The Daily Show with Jon Stewart, on March 23rd, catches Nancy Grace (CNN reporter) declaring his entire scientifically-based report as “magic”, when his actual words are “this is science, it is not magic”. How have we arrived at a point where news reporting celebrities with no real knowledge have the right to openly defy independent experts? When experts, defined here simply as those who have actually studied the problem, cannot speak above the background noise of news commentary there is little hope for a coherent picture of reality. Feel free to view the full episode here: http://www.thedailyshow.com/full-episodes/wed-march-23-2011-richard-lewis
Despite current media fluctuations, one can have hope in the future that clear thinking, taken at the proper pace (and perhaps combined with data visualization), can provide the context that allows us to distinguish reality from fiction and to eventually determine the proper perspective on current events.
Radiation Comparison (March 17th, original post)
This map was created to provide a visual way to communicate risks associated with radiation dosage.
All units are converted to mSv/h. Typically, background radiation, chest CT scans, and food levels are given in mSv/year (milli-sieverts per year). More extreme amounts of radiation, such as those found in nuclear disasters like Chernobyl are given in Sv/h (sieverts). To provide a basis for reasonable communication and comparison all units were converted in mSv/h on a logarithmic plot.
Nuclear Incident Levels are shown from 0 to 7, but keep in mind that specific events trigger an incident level rather than radiation dosage. Only at levels 1,2 and 3 are specific dosage limits set. An incident level of 5 was recently set for Fukushima based on melting of exposed nuclear rods.
At 1 mSv/h, cancer risk from radiation is 1 in 20,000 which is still well below the normal cancer risk associated with other causes, 1:25. The onset of radiation poisoning starts at 100 mSv/h. Low level symptoms include itching and nausea, while high level symptoms include dimentia, hemmoraging and death within one day.
Comparison to Atomic Bombs
So far, these levels have only been reached at Fukushima within 100 meters of the unit cores. Distance falloff with radiation is shown in comparison to Chernobyl. Note that there are many other factors, such as prevailing winds, containment of the core, and release of radiation by gas or dust, which will affect the distance profile of radiation exposure. In the case of atomic bombs, such as those released at Hiroshima and Nagasaki, the radiation is 30,000 mSv/h within the crater zone (<1 km). Atomic bombs produce an intense burst of radiation in less than one second, but this radiation is sufficient to cause death in a few days. Other effects, such as vaporization, intense heat and fire, and concussion, are greater causes of death within the immediate area of an atomic blast. Outside this area, the effects of fallout are much more significant as radiactivity is no longer isolated to a specific location, but carried in particles suspended in the air. Thus nuclear explosions, unlike the events of Fukushima or Chernobyl, carry much greater risk since sources of radiation is no longer localized.
Comparison to Chernobyl
In Chernobyl the core itself exploded, releasing large chunks of the reactor core outside the containment vessel. Radiation levels of 10,000 mSv/h were recorded outside the building, where workers used shovels to remove pieces of the radioactive reactor core without knowledge of the material. Since the core itself exploded, radiation produced fallout and suspended radioactive particles similar to a nuclear explosion (but less severe). This had the effect of spreading radioactive material away from the accident center. At Fukushima, the largest peak observed as of March 16th was 1000 mSv/h near the core. While fuel rods have been exposed to air, the release of suspended radioactive particles is much less than at Chernobyl.
Thus far, as of March 16th, the maximum radiation dose at the Fukushima main gate is 11 mSv/h, which presents a cancer risk but is below the onset of acute radiation poisoning. Twenty kilometers away (20km), at the edge of the evacuation zone a level of 0.3 mSv/h was recorded. This is just above the International Limit for Nuclear workers for a full year (100 mSv/year = 0.01 mSv/h. These levels would be severe if they were sustained, but the values recorded represent peak measurements over the past few days. Continuous exposure within the area of 20 km may cause health problems in the future, but is unlikely to cause radiation sickness based on the current status of the accident.
In areas as far away as Tokyo, 206 km, residents and workers from other countries have been evacuating. Recently, countries including USA, France, Britain and Australia were instructing people to leave Tokyo ( http://news.xinhuanet.com/english2010/world/2011-03/17/c_13783578.htm). Is this need to evacuate Tokyo based on radiation from Fukushima warranted? Radiation falls off with the square of distance, so the amount of radiation in Tokyo will be an order of magnitude less than the 20 km evacuation zone. Recent news articles have indicated that radiation in Tokyo is twice the normal background radiation for the city. At first, this may seem significant. Normal background radiation levels in Tokyo were 0.00004 mSv/h. As of March 18th, radiation levels due to Fukushima have been recorded as high as 0.00012 mSv/h, three times background.
However, background radiation in certain cities in Iran, India, China and Brazil are recorded at 0.006 mSv/h, which is fifty times higher than the radiation recorded in Tokyo due to Fukushima. Thus, if one is evacuating from Tokyo to any of these places, exposure will increase because of where one is evacuating to. Considered another way, smoking cigarettes produces greater radiation exposure than that produced by the effects of Fukushima in Tokyo. Of greater concern is the possibility of individual radioactive particles themselves being relocated to Tokyo by importing them in clothing or hair from people inside the Fukushima evacuation zone. Hopefully, measures are being taken to screen residents coming from areas closer to the nuclear plant.
Comparison to Three Mile Island
A recent news article in CNN declared “Fukushima on par with Three Mile Island”, with the implicit subtext that Three Mile Island was the worst disaster in US history, so therefore Fukushima must be very serious. What this fails to address is that Fukushima is significantly worse in many ways. They are similar in that loss of coolant and backup cooling has led to increasing decay heat in a nuclear reaction which has automatically shutdown, but in many other respects they are very different. First, only one reactor at Three Mile Island experienced a partial melting of the fuel rods, while all four out of six independent reactors at Fukushima are undergoing partial fuel melting. Second, the events at Three Mile Island were entirely contained within the reactor vessel, while in Unit 4 at Fukushima a fire was reported in a spent fuel pool outside the primary reactor container. Third, at Three Mile Island, the build up of pressure resulting for lack of coolant led to a moderate internal explosion inside the building, while at Fukushima in Units 1 and 3 the hydrogen explosion was powerful enough to blow the concrete top off the buildings. Fourth, in both accidents it was necessary to release the vessel pressure by venting to the outside air – this is the most significant factor contributing to public exposure to radiation. At Three Mile Island, a single core was vented once (as far as my sources say), which resulted in a voluntary evaluation of the surrounding area. At Fukushima, several cores have been vented multiple times thus far, and a mandatory evacuation has been called for up to 20 km. Ultimately, at Three Mile Island, it was learned much later that 50% of the rods have melted, while at Fukushima it has already been reported that 70% has melted in reactor Unit 1 and 30% in reactor Unit 2.
On the positive side, in all four reactors the radioactive fuel rods are still contained within their primary vessels – which was not the case at Chernobyl. Based on news reports, I am strongly tempted to say that the media is attracted to equivalent comparisons with Three Mile Island because it likes to focus on the sufferings of westerns more than those around the world, or the history of Three Mile Island – or perhaps there is still a significant amount of pressure to downplay the seriousness of the events at Fukushima. At present, however, I would agree with the International Nuclear Event scale rating Fukushima at Level 5, “accident with wider consequences”, which resides above Level 4 at Three Mile Island, ”accident with local consequences”, but still well below Level 7 at Chernobyl which was a “major accident”.
Another positive aspect is that the response at Fukushima is probably much more adequate than either Three Mile Island or Chernobyl. Nuclear standards and procedures are much more detailed now than before. Instrument panels are better designed now, which was one of the primary factors contributing to the Three Mile Island incident. The danger of radioactive materials is known, so that rescue workers and fire teams know what they are dealing with; problems that were not addressed well at Chernobyl. The fact that three reactors have partially melted with loss of cooling to all of them, yet there has not been any containment breach yet, is practically a marvel of management of limited human and material resources. Of course, it would have been nice if the reactors could be designed to be automatically cooled in the event of a power loss, but I’m no nuclear engineer. These are the dangers of fission-based nuclear power. Personally, I’m looking forward to fusion, which is an inherently stable power souce (See: http://en.wikipedia.org/wiki/National_Ignition_Facility and http://en.wikipedia.org/wiki/ITER)
The Fukushima incident is clearly a cause for concern. As the events unfold, the question is whether the peak radiation levels will go much higher than the 8000 mSv/h currently reported near the core. This level already represents a significant radiation incident, which places Fukushima along side other major nuclear accidents. To achieve the same status as Chernobyl, however, levels would have to be at least ten times higher than the current peak, which is unlikely to happen unless there is a core meltdown or explosion as there was at Chernobyl. At present, fuel rods are still contained within the core. For the sake of those in Japan, and the immediate area, we can hope the radiation levels will not go any higher.
Fukushima Accident Events
The map above also shows specific events that took place after the start of the crisis. Data for on-site measurements of radiation levels were taken from TEPCO Press Releases, March 17th (http://www.tepco.co.jp/cc/press/betu11_j/images/110317e.pdf). The timing of events are from several sources listed on the Wikipedia page for Fukushima I Nuclear Accident.
Interestingly, the times of particular events such as hydrogen explosions, pressure increases, fires, and cooling failures do not coincide with any of the peaks in the radiation levels. In fact, none of the events corresponds with a peak. There could be several causes for this. First, the times of events may be reported incorrectly. While the time of the hydrogen explosions is likely to be exact, since these are such noticeable events, times reported for cooling failures and fires may be inexact due to the nature of these events. Often, in the wikipedia article reporting these events, as single source is used as the only citation for a particular event in several locations in the article. Thus, one may suspect that times reported by the news agencies themselves are possibly inaccurate. Only after a thorough analysis could we be sure that the news is presenting correct data based on its own sources.
The main cause for a lack of coincidence between events and radiation peaks is likely to be the underlying physics at the site. A cooling failure is unlikely to be a peak, since it represents the start of the problem. A hydrogen explosion may also not be a radiation peak, since it does not directly release radiation. A fire, such as the one that occurred in the fuel pool in Unit 4, is a more likely source of a direct radiation, but this is difficult to correlate due to the nature of fires. The only event in the graph that does correlate with radiation release is the intentional release of pressure, which is necessary to keep the core from exploding.
Needless to say, an uncooled, partly controlled nuclear reaction is a complex phenomena. The data presented in the map above is all the more complex because it represents the activities at four nuclear unit simultaneously, each at different distances from the recorded data location (main gate). There are likely main different phenomena taking place within these cores which could not be fully understood without computer simulation. The many other peaks in the graph have no correlation to reported events thus far. I find it interesting that several curves show a particular profile, with a sharp peak followed by a gradual falloff of a specific shape. A question for a physicist would be, how do you explain the profile curve of these events, and would it be possible to simulate or even predict the overall data curve based on the events that took place? If so, this would be a useful tool for estimating the effects of other incidents similar to Fukushima.