What is happening with the Fukushima evacuation, and how the radioactivity in Fukushima compares to other places people visit and live. The cleanup, food and fish, and the cost of increased use of fossil fuels.
Many places in the world have high natural background radiation
According to World Nuclear Association,
Naturally occurring background radiation is the main source of exposure for most people, and provides some perspective on radiation exposure from nuclear energy. The average dose received by all of us from background radiation is around 2.4 mSv/yr, which can vary depending on the geology and altitude where people live – ranging between 1 and 10 mSv/yr, but can be more than 50 mSv/yr. The highest known level of background radiation affecting a substantial population is in Kerala and Madras states in India where some 140,000 people receive doses which average over 15 millisievert per year from gamma radiation, in addition to a similar dose from radon. Comparable levels occur in Brazil and Sudan, with average exposures up to about 40 mSv/yr to many people. (The highest level of natural background radiation recorded is on a Brazilian beach: 800 mSv/yr, but people don’t live there.)
Several places are known in Iran, India and Europe where natural background radiation gives an annual dose of more than 100 mSv to people and up to 260 mSv (at Ramsar in Iran, where some 200,000 people are exposed to more than 10 mSv/yr).
Units* are explained at the end of this post.
That list is far from complete; there are a number of other places with high background radioactivity:
• Finland, population 5.4 million, almost 8 millisievert each year (mSv/year)
• parts of Norway over 10 mSv/year
• Yangjiang, China population 2.6 million > 6 mSv/year
• Denver 2.6 million, 11.8 mSv/year
• Arkaroola, South Australia, 100 x more radioactive than anywhere else in Australia. The hot springs are hot because of radioactive decay!
• Guarapari, Brazil where the black sand on the beach comes in at 90 µSv/hr using the 800 mSv/year figure above, but higher recordings have been seen, up to 130 µSv/hr. People are permitted to sit where they will on the beach without wearing any special hazmat outfit.
• Radon was first discovered as a major portion of our exposure when Stanley Watras triggered the alarm at his local nuclear power plant. His basement was more than 800 µSv/hour.
• Etc… Cornwall … etc…southwest France…etc…
• Air travel increases our exposure to radioactivity, by about 4 – 7 µSv/hour, more for the Concorde NY to Paris route.
Numbers provided by different sources vary for a number of reasons. Some sites don’t include our own internal radioactivity, about 0.4 mSv/year. Some look at maximum, some look at maximum people actually live with, some average.
Japanese evacuation categories
Over 160,000 were evacuated in 2011. The Japanese government only allowed return to begin in 2012 where yearly dose would be less than 20 mSv/year the first year back, although decontamination would continue. Restrictions exist for areas not expected to drop below 20 mSv/year by March 2016, 5 years after the accident, and include about half the 20 km (12 mile) evacuation zone. As of now, all towns can be visited, although some visits are restricted, including Futaba, the town closest to the plant, where many houses were destroyed by the tsunami.
The Japanese government has 4 categories for evacuation:
—difficult-to-return zones, with evacuation expected to be at least 5 years from March 2012
—no-residence zones, where people will be able to return earlier
—zones preparing for the evacuation order to be lifted
—planned evacuation zone, “a high-risk zone to the northwest of the plant and outside the 20-kilometer radius that is yet to be reclassified into any of the three other categories.”
Dose equivalent 11/2011
Dose equivalent 3/2013
Dose equivalent at 3/2013 level
Difficult to return
Evacuation order to be lifted
Planned evacuation zone
Table: Radioactivity decline over 17 months.
Of course, the level of radioactivity will continue to decline. This rate of radioactivity decrease is about the same as was seen in the areas around Chernobyl, where cesium declined with a half life of 0.7 – 1.8 years; decline in the zones around the Fukushima plant was about 40% in 1.6 years. The areas around Chernobyl saw a rapid decrease for 4 – 6 years, so it would not be surprising if by January 2015, all rates had dropped by half, and by November 2016, all rates dropped by half again, even without special clean up work. The difficult to return zones would expect to see an average of 2.1 µSv/hr, or a temporary rate of 19 mSv/year, or less, by November 2016. Assuming the Japanese experience is the same as in the areas around Chernobyl, the rate should continue to decline rapidly between 2011 and 2015 – 2017.
To get some idea of radioactivity in the area northwest from the Fukushima-Daiichi plant, go to this map which is updated frequently (although we are unlikely to see any change day to day). Note that you can get more detailed information by placing your cursor over the sites; the most radioactive site at the end of September 2013 was 26 µSv/hr. The sensors are in place and sending information to the Japanese NRA (nuclear regulatory agency).
Note: nowhere on this map is as radioactive as a number of places where people travel freely, such as Guarapari, Brazil or Ramsar, Iran.
How is Japan doing on the cleanup?
In November 2011, a team from International Atomic Energy Agency thought that Japan deserved good grades for prompt attention to cleanup, and poor grades for setting reasonable priorities.
In practical terms this translates to focusing on the quickest dose reduction, without unwanted side effects like classifying millions of tonnes of very lightly contaminated topsoil as ‘radioactive waste’. It may be desirable to remove this soil from childrens’ playgrounds, for example, but some of the material may pose no realistic threat to health and could be recycled or used in construction work, said the IAEA team.
Another point of consideration is the handling of large open areas like forests. “The investment of time and effort in removing contamination beyond certain levels… where the additional exposure is relatively low, does not automatically lead to a reduction of doses for the public.” Japanese authorities have already noted that removing some contaminated leaf mold could have a greater harmful effect on some parts of the ecosystem.
The Japanese appear to be spending lots of money to bring the level of radioactivity well below 20 mSv/year, at best only partially following IAEA recommendations:
A further 100 municipalities in eight prefectures, where air dose rates are over 0.23 µSv per hour (equivalent to over 1 mSv per year) are classed as Intensive Decontamination Areas, where decontamination is being implemented by each municipality with funding and technical support from the national government.
Work has been completed to target levels in one municipality in the Special Decontamination Areas: Tamura, where decontamination of living areas, farmland, forest and roads was declared to be 100% complete in June 2013. Over a period of just under a year, workers spent a total of 120,000 man days decontaminating nearly 230,000 square metres of buildings including 121 homes, 96 km of roads, 1.2 million square metres of farmland and nearly 2 million square metres of forests using a variety of techniques including pressure washing and topsoil removal.
Meanwhile, other municipalities hope to receive the classification and the money that goes with it.
What about the food?
Japan allows less radioactivity in the food and water than many other parts of the world. For example, Japan before the accident set their water safety level at 1/5 the level of the European standard, and then lowered it further. Their assumptions of the health effect of various decay rates for food and water appear to me to assume that radioactivity from food and water comes in, but never leaves.
The US standard is 1,200 Bq/L for water, and 1,250 Bq/kg (570 Bq/pound) for solid food.
The World Health Organization standard for infants is 1,600 Bq/L radioactive iodine, and 1,800 Bq/L radioactive cesium (table 6 here).
Similarly the Japanese food standard for radioactivity began lower than that in other countries, and the Japanese lowered it even further. This has repercussions for Japanese farmers—more than a year ago, 30 out of almost 5,000 farms in the relatively contaminated areas farmed rice too radioactive to sell, although it would be safe according to standards elsewhere, but by imposing even more rigorous standards, 300 farms would encounter problems selling their rice.
• The new standards for Japan are 10 Bq/L water, 50 Bq/L milk (because the Japanese drink less milk), and 100 Bq/kg (new standards) for solid foods.
“Scientists say [the much higher international] limits are far below levels of contamination where they can see any evidence of an effect on health.”
There are a number of foods naturally more radioactive than the new Japanese standard, for example Brazil nuts can be as much as 440 Bq/kg. Even though Bq is a decay rate and not a health effect, the health effect from cesium decay and other radioactive atoms normally in food, like potassium, is the same.
From a Woods Hole article on seafood,
In one study by the consumer group Coop-Fukushima, [Kazuo Sakai, a radiation biophysicist with Japan’s National Institute of Radiological Sciences,] reported, 100 Fukushima households prepared an extra portion of their meals to be analyzed for radioactivity. The results showed measurable amounts of cesium in only three households, and in all cases showed that naturally occurring radiation, in the form of potassium-40, was far more prevalent.
The article contains a statement by a Japanese pediatric oncologist, recommending massive removal of top soil, etc so that levels of radioactivity were below natural background in the US, with the idea of reassuring Japanese citizens.
Ironically, some suggested, the Japanese government’s decision to lower acceptable radiation limits in fish may have actually heightened consumer fears instead of dampening them. Deborah Oughton, an environmental chemist and ethicist at the Norwegian University of Life Sciences, related that the Norwegian government, when faced with high radioisotope concentrations in reindeer meat as a result of Chernobyl, decided to raise acceptable limits from 600 to 6,000 becquerels per kilogram. The move was made, she explained, to protect the livelihood of the minority Sami population that depends on reindeer herding for its survival.
Weighed into the judgment, she added, was the issue of dose: The hazard involves not only how high the levels are in meat, but how much you eat—and Norwegians rarely eat reindeer meat more than once or twice a year. The decision had no impact on sales of reindeer meat.
The larger point, Oughton said, “is that public acceptance with regard to these issues comes down to more than becquerels and sieverts. It is a very complex issue.” And nowhere more complex than in Japan. Alexis Dudden of the University of Connecticut offered a historian’s perspective when she suggested that “both at the local level and the national level, some discussion needs to take into consideration Japan’s particular history with radiation.”
What about the fish?
According to the KQED interview with Matt Charette (minute 14:15 – 15), 20% of fish obtained near Fukushima prefecture come in at above the Japanese standards.
The Japanese allow 100 Bq/kg fish, <1/10 as much radioactivity as Americans (and everyone else). Within 20 km (12 miles) of the plant, they are finding that 40% of the bottom dwelling fish off Fukushima don’t meet the Japanese standards. While most of these will meet international standards, two greenling caught in August 2012 came in at 25,000 Bq/kg (subscription needed).
All fish, particularly the bottom dwelling fish are tested from this region and those that flunk are not sold in Japan or exported.
According to Fukushima-derived radionuclides in the ocean and biota off Japan, in Proceedings of the National Academy of Sciences, the level of cesium in fish would need to be about 300 – 12,000 Bq/kg to become as important as the radioactive polonium-210 found in various fish species. Potassium-40 is also an important source of radioactivity in ocean fish. Only a small portion of fish tested in 2011 had become half as much more radioactive than ocean fish are naturally. Eating 200 gram piece of fish (typical restaurant portion) at >200 Bq cesium/kg is equivalent to eating an uncontaminated 200 g banana.
Fishing has begun again off the coast:
Out of 100 fish and seafood products tested, 95 were clear of radioactive substances and the remaining five contained less than one-10th of the government’s limit of 100 becquerels for food products, it added.
Cost of switching to fossil fuels
Japan is now operating full time old power plants meant to operate while the nuclear plants are down, and it is challenging to keep them on. Much of the $40 billion annual increase in the cost of fossil fuels (to $85 billion) since March 2011 is due to replacing nuclear power with fossil fuels.
Japan’s greenhouse gas emissions are up about 4%, even with reduced electricity available, 10% for electricity.
* Units: One microsievert (µSv) = 1 millionth of a sievert. One millisievert (mSv) = 1 thousandth of a sievert. The model predicts approximately for the general population that 10 man Sieverts = 1 cancer, 20 man Sieverts = 1 death. Most major organizations assume a lower health effect for low doses (below 100 mSv or below 10 mSv) or for a low dose rate.
Sieverts include decay rate, type of decay (some types of decay do more damage), and tissue type—they are a health effect.
There are 8,760 hours/year. Multiply values for µSv/hour by 8.76 to get mSv/year. Since radioactivity is disappearing rapidly from the area around Fukushima-Daiichi, round down a bunch to get your actual exposure over the next year if you move back today.