The biggest flaw with the evacuation triggered by this accident was the lack of advance planning about what actions would be necessary with the situations in the surrounding areas. To worsen the unpreparedness, as discussed in Chapter 3, the most important spot to gather information from the accident site and make judgments, the Offsite Center, was paralyzed, and thus the evacuation proceeded without the local emergency response headquarters function.

Evacuation orders from the central government were incomplete without sufficient information, and moreover, they failed to reach all the local governments in the evacuation zones. Local regions faced hardship in trying to counteract the widespread effect of the nuclear disaster, and to add to that, the earthquake and tsunami had destroyed all means of communication. It was another problem that each local government had to take action against in isolation.

5.2.2 The process of evacuation in response to the accident

For proper understanding of the residential evacuation, we need to review the time progression of events within the power plant and the amount of radiation release to the outside to relate them to evacuation orders from the government nuclear emergency response headquarters (NERHQ). Figure 5.2 plots the relationships. The following paragraphs outline the relationship between on-site events and the progress of evacuation.

At 19:03 on March 11th, Prime Minister Kan declared a state of nuclear emergency following loss of all AC power and failure of water injection by emergency core cooling facilities at Fukushima-1 and established NERHQ. Following this declaration, Fukushima prefecture ordered evacuation of the residents within 2 km of the plant at 20:50.

NERHQ, with the possibility of having to vent the CV to avoid core damage, took a precautionary measure and at 21:23 ordered evacuation from within 3 km of the plant and ordered people to stay indoors in the 3-10 km range. Later with the rise of CV pressure with Unit 1 and failure to vent Units 1 and 2, NERHQ decided to extend the evacuation range to within 10 km at 05:44 on March 12th.

The Unit 1 reactor building exploded at 15:36 on March 12th, and initially not knowing the cause, Prime Minister Kan took heed of the words by the Chairman of the Nuclear Safety Commission (NSC) of possible criticality, and NERHQ further extended the evacuation range to within 20 km and ordered so at 18:25.

The situation at each unit continued to worsen, and the explosions in reactor buildings of Unit 3 at 11:01 on March 14th and Unit 4 at 06:10 on March 15th led to the 11:00 order on March 15th for the residents in the 20-30 km range to stay indoors (Figure 5.3).

Local Response Headquarters at the off-site center should be in charge of ordering evacuations; however, as discussed in Chapter 3, the paralyzed off-site center forced decisions to be made at the prime minister’s office. The cooling status of each reactor and other factors contributed to the decisions. However, each local region within the evacuation range was simply ordered to evacuate, and the local governments with information only available from TV and radio had to decide on the evacuation routes and guide the people in their districts.

Radioactivity is invisible and odorless, and people cannot sense its existence. Therefore, without adequate information, we cannot make any judgments in response to its behavior. In fact, when situations reached the point when external radiation release had turned into a threat, orders to the local governments lacked guidance on whether to stay indoors or to evacuate, and further in case of evacuation, without details of when, where, and how. At the time, even information about radioactivity spread that local governments had to rely on was unavailable.

Without accurate information, the residents were, in response to the expanding evacuation zone, merely told to move away from the plant as far as possible. It was only natural that those that had to evacuate twice and even three times felt that they were being “tossed around” by the authorities.

Although Unit 2 had no hydrogen explosion, its core is estimated to have melted down (core damage), and with the damaged CV, Unit 2 probably released the greatest amount of radiation among all units. Readings from the off-site environmental radiation-monitoring posts were moderate from March 12th to 14th; however, they reached very high levels from the night of March 14th to 15th. It was the time when the core and CV of Unit 2 were damaged. The radiation around the main gate of Fukushima-1 in the morning of March 15th reached as high as 10,000 μSv/h, a level that would cause the cumulative radiation to reach 100 mSv within 10 hours. Epidemiological studies of the atomic bomb victims have shown that a radiation dose of 100 mSv or higher increases the risk of cancer.

Radiation does not necessarily spread concentrically around the origin. Its irregular spread depends on weather and terrain. In the afternoon of March 15th, when a large amount of radiation was released, the wind started blowing to the northwest, and to make things worse, rain then caused fallout with strong radioactivity in the region approximately 50 km northwest of Fukushima-1. The evacuation orders, immediately after the accident without accurate information about the spread of radioactivity, were made in sequence of larger concentric areas from the plant. Later investigation, however, revealed areas with high concentration of radioactivity formed a shoe-sole-like shape, with Fukushima-1 at the heel, covering as far as the outer rim of Iitate, a village located about 50 km away from the plant in addition to Okuma and Futaba, where the plant is located. As the authorities learned more about the radioactivity spread, they reshaped the evacuation zones to form the same shape. On April 22nd, authorities declared the area within 20 km from Fukushima-1 an “Exclusion zone,” and everybody was evacuated. Outside this area to within about 50 km was partially, where the shoe-sole covered, declared a “Planned evacuation zone.” Areas with minor contamination with a distance of 20-30 km from the plant were declared “Emergency evacuation preparation zone” (Figure 5.4).

About 9 months after the accident on December 16, 2011, the authorities judged the reactor to have stabilized reaching the state of cold shutdown, and on December 26th, with the threshold of the annual accumulated dose of 20 mSv, they divided the area into a “difficult-to-return zone,” “residence limitation zone,” and “evacuation order lift preparation zone.” The zoning was reset on March 7, 2012 after review (Figure 5.5).

5.3.2 Speed of radiation spread

Let us explain the terms and units we have been using so far in this book about the strength and magnitude of radiation.

Sievert (Sv) is the unit for the dose of radiation that affects the human body. The unit milliSievert (mSv) that we see more often is its 1 thousandth, and microSievert (μSv) its 1 millionth. For the impact of radiation on human health, what counts is the total amount of radiation (cumulative dose) the body is exposed to. The intensity of radiation, “air dose,” is expressed with the amount of radiation dose per each hour while the body is at the location. We use microSievert per hour (μSv/h) for hourly exposure and milliSievert per year (mSv/y) for annual exposure. Cumulative dose and air dose are related; e.g., when exposed to 1 μSv/h for 1 year, the total cumulative dose for the year is: 1 μSv/h × 24 hours × 365 days ~ 9 mSv.

As we showed earlier, the area of high air dose is spread in the shape of a shoe-sole, and some spots like Namie and Iitate, that are 30 km away from Fukushima-1 plant, have an air dose as high as 10 μSv/h or higher (as of April 2011). An air dose of 10 μSv/h will result in an annual cumulative dose of 87.6 mSv, and if a cumulative dose that exceeds 100 mSv causes damage to the human health, this 87.6 mSv is a fairly high value.

Ministry of Education, Culture, Sports, Science and Technology (MEXT) published a “Distribution map of radiation dose around Fukushima Dai-ichi & Dai-Ni NPP (as of January 11, 2012)” [1] that estimated the total radiation exposure from March 11, 2011, to March 11, 2012. The document shows a 20 mSv area extending as far as 50 km from Fukushima NPP. Although very unlikely, a person who stayed in the area for 5 years would probably suffer effects of radiation.

Radiation released from NPP is carried by wind (called radioactive plume), and if it rains, then the raindrops will capture the radioactive material and take them down on the ground. In most cases, however, without rain, wind will carry radiation to distant locations and disperse it.

5.3.3 System for Prediction of Environmental Emergency Dose Information (SPEEDI) simulation of radioactive spread

Nuclear Safety Technology Center (NUSTEC), an affiliate company of MEXT, started operating a System for Prediction of Environmental Emergency Dose Information (SPEEDI) in 1986 for use in evaluating methods to protect people from radiation effects.

SPEEDI finds “when,” “in which direction,” and “in what quantity” radiation released from an NPP will spread based on information from the radiation source, terrain, and weather. The system works with radiation release data transferred from TEPCO via NISA to NUSTEC for the simulation, and the results are forwarded to NISA, affected prefectures, the off-site center, and NERHQ.

SPEEDI simulated the reaction to the 1999 JCO criticality accident, and the same task was to be performed for this Fukushima-1 accident. This time, however, the earthquake and tsunami caused damage that disrupted the transfer of release source data to carry out the simulation.

Figure 5.6 shows the SPEEDI calculation from assumed release source data on March 15, 2011, which was the day with the largest amount of radiation release. The air dose map (Figure 5.7) from aircraft monitoring, made available 2 months after the accident, shows a shoe-sole-like area of high dose to back the simulation results by SPEEDI.

In the case of this accident, however, even though the direction of radiation spread had been calculated, the residents had to evacuate without knowing how much radiation was spread in which direction just because the radiation release source data were unavailable.

People live with a number of factors that can harm health (Figure 5.8a). Risk factors that can harm people include cigarettes, alcohol, other lifestyle habits, and social stress. Radiation is another one of such factors. The concern with this Fukushima accident is the effect of radiation on human health. Here we will explain the basic knowledge of the relationship of radiation to human health and then discuss the impact of radiation from this accident.

We have to start by classifying radiation that affects human health in two groups. One is “natural radiation” from radioactive material that existed in the world from the beginning. The other is “artificial radiation” from radioactive material placed in the environment by accidents, atomic bombs, and other man-made causes.

Natural radiation exists in cosmic rays from outer space, earth (rock beds and stones), and some other natural objects. This causes external exposure from outside the body and internal exposure through breathing, eating and drinking. Humans are always exposed to natural radiation and cannot hide from its influence.

The amount of natural radiation differs geographically, e.g., an average annual dose from natural radiation in Japan is about 1.5 mSv with the amount in western Japan being about 1.5 times that in eastern Japan (Figure 5.9). The annual world average is slightly higher at 2.4 mSv.

If one lives for 80 years in Japan, the accumulated dose is 1.5 mSv/y × 80 years = 120 mSv. The effect of this natural radiation on the health is not clear; however, there is no noticeable regional difference within Japan (we will discuss external and internal exposure later).

The concern with this accident is the effect of exposure from the radioactive material it released. We have to add the amount due to the accident to the natural radiation in the area.

5.4.2 The impact of nuclear radiation on human health

In evaluating the effect of radiation from the accident, we have two methods: one is to find the dose rate with μSv/y, mSv/y, μSv/h, or mSv/h, and the other is to count the total amount of radiation on one person (accumulated dose). The total dose with a short exposure to high dose and long exposure to low dose are both called accumulated dose. Even if the two cases had the same accumulated dose count, the impact on human health is totally different with instant exposure and an exposure over the whole life.

None of the on-site workers or off-site residents suffered acute radiation syndrome from a large dose within a short period of time. The concern, thus, is long-term effect of chronic dose (i.e., a small amount of radiation received over a long period of time). For humans, we know that an accumulated dose of 100 mSv or more of extended chronic dose increases the risk of cancer (Figure 5.8b).

If the accumulated dose is 100 mSv or less, however, the impact of radiation dose on health is unclear. The reason is that radiation is then just another one of all the risk factors that surround us, and we cannot identify the pure effect of radiation alone.

One may think that as long as the impact of 100 mSv or less accumulated dose on health cannot be denied, we should keep the exposure as low as possible. That is a good practice if circumstances allow it; however, an overly nervous reaction against exposure can cause mental stress and add other risk factors that may affect human health even more.

We have to be aware that we are constantly exposed to natural radiation, and chronic dose is just another risk factor that may affect human health.

5.4.3 Physical and mental effects from nuclear radiation

There are two ways for humans to be exposed to radiation. One is external exposure (i.e., the effect from radioactive material to the outside of the body). The other is internal exposure from radioactive material taken inside the body through breathing or food and beverage consumption. Both external and internal exposure cause physical effects, mainly in the form of damage to the DNA or cancer.

We should not forget, on the other hand, that the mind is also affected by radiation, in addition to physical damage. The most common form of mental damage is the fear of risk to the body (e.g., of developing cancer).

This fear causes people to overreact to radioactive material by making irrational decisions and acting unreasonably. When the whole society is influenced, it gives rise to harmful rumors and can hamper proper evacuation and decontamination. To minimize the impact on the human mind, we need to have an understanding of how radiation affects human health.

Each and every resident from the nuclear accident affected area, in order to lead a life with a calm mind, needs to have their health monitored with proper treatment as needed. Long-term health monitoring is necessary. The collected data will serve as a valuable source of information in understanding the relationship between humans and radiation.

5.4.4 Effects of internal exposure to nuclear radiation

Radioactive material taken into the human body through breathing, consuming food or beverages, or through skin, decays inside the body and emits radiation that affects our cells and DNA. This phenomenon is called internal exposure. The amount of radioactive material taken inside the body reduces over time by being discharged from the body.

This accident released a large amount of radioactive iodine to the outside. Radioactive iodine easily evaporates to spread over a wide volume in the atmosphere and quickly invades the body through breathing, eating, or drinking. Iodine taken inside the body accumulates at the thyroid gland to cause internal exposure. This organ is in the process of growing in infants and is highly active in young people. Children can easily suffer from a thyroid disorder when radioactive iodine accumulates in the thyroid gland.

Filling up the thyroid gland with stable iodine will prevent further accumulation of iodine there, and excessive iodine that arrives later is quickly discharged with urine. This is why taking stable iodine tablets is effective in preventing accumulation of radioactive iodine in the thyroid gland. Iodine, when it enters the body, quickly reaches the thyroid gland; thus, it is important to take the tablets before exposure. It is also said that a diet that includes plenty of seaweed will increase the amount of iodine in the body and thus will block radioactive iodine from reaching the thyroid gland.

Much has been said about iodine exposure with this accident; however, the amount of release and its spread have not really been clarified. The short half-life of 8 days with iodine 131 makes it difficult to take any measurement after time has elapsed after the accident. We can probably only make estimates of the iodine release and distribution based on measurements made immediately after the accident and recorded data of other radioactive material with longer half-lives.

Cesium, on the other hand, dissolves in water; thus, when it enters the body, it reaches and stays in the muscle tissues to cause internal exposure. Its biological half-life (time it takes to be discharged from the body until the radioactivity is half the original magnitude) is about 70 days. For cesium, we currently do not have the equivalent of stable iodine tablets, so we have to take care not to let cesium into the body with food. This is one of the contributing factors that caused the harmful rumor about Fukushima produce.

5.4.5 Effects of external exposure to nuclear radiation

Humans have always been exposed to natural radiation from cosmic rays that reach the earth from outer space and radiation from radioactive materials in the natural environment.

Regions where radioactive material reached were subject to added radiation from the accident to the natural radiation of 1.5 mSv/y. If the accident had added 20 mSv/y, the total amount would have reached 21.5 mSv/y, and the people would have been exposed to 14 times the natural radiation. On the other hand, if the addition caused by the accident was 1 mSv/y, adding it to the original 1.5 mSv/y would only amount to 2.5 mSv/y. The total amount of 2.5 mSv/y is about the same as the world average of annual natural radiation. Decontamination efforts to lower the added dose to about 1 mSv/y are reasonable.

When the authorities discussed the criteria for using school facilities, the value 3.8 μSv/h had a strong message. An outdoor exposure of 3.8 μSv/h with 8 hours of outdoor activity with indoor exposure for the rest of the day, where the exposure is about 0.4 times that from outdoors, sum to a daily exposure of 54.72 μSv. This value multiplies to an annual exposure of 20 mSv. This is how the criterion of 3.8 μSv/h was reached for judging whether schoolyards were acceptable for activities or not.

When we look at external exposure, we must turn our attention, among the radioactive material released by the accident, to cesium 137 with a long half-life of 30 years. Iodine 131 and cesium 134 have relatively short half-lives of 8 days and 2 years, respectively, and their effects do not last very long. Cesium 137, however, with its long half-life of 30 years, once released to the environment, causes long-term effects that render land and houses uninhabitable. This is why cesium 137 is of concern regarding decontamination.

Radiation, however, is just one factor among all others that affect human health. Being overly concerned with the hard-to-accomplish limit of 1 mSv/y and forgetting about other factors will cause us to make the wrong judgment.

The main ingredient of stable iodine tablets is nonradioactive iodine, which prevents buildup of radioactive iodine in the thyroid gland if taken before internal exposure to prevent its damage.

Administering stable iodine tablets is carried out according to procedures set out by the Nuclear Safety Commission of the government advising the local NERHQ, which makes decisions for prophylaxis administration and reports it to central NERHQ. The decision by the headquarters is delivered to each prefecture governor, who then relays the decision to the residents.

The six counties around Fukushima-1 and -2 had stocks of stable iodine tablets following the “Emergency Radiation Exposure Medical Action Procedure” [2]. The prefecture, on March 14th, decided to distribute stable iodine tablets to all residents under age 40 living within about 50 km of the plant and completed the distribution by the 20th.

The largest radiation release, however, took place on March 15th, and prophylaxis distribution after when it was needed most had no point. This event just teaches us how inappropriate the procedure was.

On the 16th, the local response headquarters ordered “stable iodine tablet administration when leaving the 20 km zone” to the prefecture and 12 related counties; however, the prefecture did not make orders for prophylaxis distribution because the 20 km zone had already been evacuated.

In addition, on March 13th, the Nuclear Safety Commission advised administering stable iodine tablets to those with exposure doses over a limit during the screening. The advice, however, did not make it to the local response headquarters.

Some counties around Fukushima-1, however, made their own decisions to distribute stable iodine tablets to their residents. As we discussed in Chapter 3, Miharu, based on the rise of radiation at Tohoku-EPCO Onagawa NPP on March 14th and the weather forecast on March 15th, decided to distribute and administer stable iodine tablets.

Officers of Fukushima prefecture, who learned about the distribution and administration, ordered Miharu to stop the distribution and recover those already given out for the reason that the central government had not given orders to do so. The county did not follow the halt and recall order.

Such confusion was the result, as we will discuss later, of operations run by people with poor understanding of stable iodine tablets and their role in radiation protection.

5.5.2 Inadequate evacuation process

When a large amount of radiation was released to the outside on March 15th at 11:00, authorities ordered residents in the 20- to 30-km range from the plant to take shelter indoors. The city of Minamisoma led an evacuation of the residents that elected to leave the city. There were three routes that extended out from the city. The southbound route passed near Fukushima-1, and the northbound route ran along the coast, which might have been blocked by damage from the earthquake and tsunami. Most of those who opted for evacuation, thus, took national route 114 (a.k.a. Tomioka Ocean Road) that extended northeast from Fukushima-1 toward Iitate and Kawamata (Figure 5.10).

At the time, however, the wind was blowing to the northeast, and the rain worsened the situation by dropping radiation in the 20- to 30-km section northeast of Fukushima-1 at levels higher than other areas. The fleeing residents, without knowing the situation, ran toward the area with highest level of radiation fallout.

The radiation spread would have been known if the SPEEDI simulations were made available. The residents could have made proper judgments if the direction of escape and the time were right. Without this crucial information, the residents of the city of Minamisoma, who were only informed that danger was on its way, decided to flee the area instead of hiding indoors. If they had stayed indoors at this time, effects of radiation would have been smaller, and even if they had decided to leave anyway, they could have gone in the right direction with information from SPEEDI. The residents learned the facts later and were furious about what happened. Their anger comes as no surprise.

5.5.3 Evacuation routes within each county

Without prior evacuation plans to counter nuclear disasters, evacuation orders were issued and the counties had to make their own judgments and act accordingly.

After the accident, Futaba, immediately north of the plant, and Okuma, at the south, were evacuated. The evacuation order stated to “get out” without telling the destination. Some regions were lucky to use buses arranged by the central government, but most counties prepared means of transportation on their own and fled away from the plant.

As the evacuation zone extended, many evacuees had to make two or more relocations. Futaba had to move from one place to the next, and many of its residents ended up in the far city of Kazo in Saitama prefecture. People of Okuma also passed through multiple counties to reach Aizuwakamatsu far in the west.

Namie, with most of its population in the exclusion zone, fled to Nihonmatsu, and Tomioka ran to Koriyama. Some residents of Minamisoma near the plant travelled through regions of high radiation as we explained earlier.

Figure 5.11 shows the original residence of the evacuees and where they ended up. The figure shows the chaotic relation between the original place of residence and where the people found sanctuary. Some evacuees, in search of safe places, had to make long relocations. The figure is evidence that reveals the lack of effective evacuation plans prior to the accident.

5.6.1 Common misconceptions on radioactivity

A severe accident in an NPP means possible leakage of radioactive material to the outside. People, without proper knowledge of its impact on the human body and the environment, seem to have overreacted to all sorts of information. The overreaction made the situation worse.

Without proper knowledge, many of us make judgments and take actions based on wrong assumptions. These include harmful rumors.

Harmful rumors started with fresh food products. Many believed produce and seafood from the Fukushima and Tohoku areas were contaminated with radioactive material and avoided them even if their safety was confirmed by inspection. People thought that was the way to protect their own health.

Another form of harmful rumors was other parts of the country refusing to dispose of rubble that the tsunami left behind. Some even thought radioactivity transfers to others through physical contact with the evacuees, repeating the same rumors that broke out at the time of the 1999 JCO accident.

To prevent such harmful rumors caused by wrong knowledge, we have to arm ourselves with the right knowledge about radioactive materials, especially those that are released by nuclear reactor accidents.

5.6.2 Radioactive half-life

To learn about radioactive material, we need to understand “half-life.” Radioactive material decays over time and changes into material that has no radioactivity. Half-life is the time it takes a specific radioactive material to decay (the phenomenon of an atom emitting radiation to turn itself into another type of atom) until the amount of its radiation is half the original size. Half-life is different with each radioactive material, e.g., Plutonium, with a large atomic weight, hardly dissolves in any liquid, and it has a long half-life of about 20,000 years; it almost emits radiation permanently.

There were three radioactive materials of concern that spread to the outside with this accident; iodine 131 with a half-life of about 8 days, cesium 134 with about 2 years, and cesium 137 with 30 years. We will later discuss iodine 131 and cesium 137 because their amounts, behaviors, and sizes of effects were of concern.

Radioactive materials released from the Fukushima nuclear reactor floated in the air as a radioactive plume, like an invisible cloud. The wind carried the radioactive materials far and wide. As time passed, they started to fall on the ground and on leaves.

If rain falls from above the radioactive plume, clusters of radioactive material and lumps of water (raindrops) collide, and raindrops that have captured radioactive material fall on the earth (i.e., soil grains and surfaces of leaves). Areas highly contaminated by rain with radioactive material are called “hot spots.” This is shown in Figure 5.12.

Figure 5.13 shows a sketch of what the residents of the village of Iitate, one of the hot spots, felt and thought about. The sketch is based on comments from them. The comments were “Invisible clouds of radioactivity came from the other side of the southeast hills and the ‘radioactivity’ fell on and got stuck to our rice patties, produce fields, houses, and forests.”

Some of the fallen radioactive materials were washed away with the rainwater. That is why higher radiation was measured in rain gutters, water ditches, and naturally formed rain channels. Radioactive material that was not washed away, on the other hand, stuck to soil particles, leaves, and roof shingles and stayed there even after the water evaporated. Radioactive material molecules that got stuck to other object surfaces cannot be washed away even with brushes. Figure 5.14 shows the mechanism.

It is a natural desire to remove the radioactive material that spread out from the nuclear plant. Unlike chemically disinfecting poison with neutralizers, we do not have processes for erasing radioactivity.

The accident released several types of radioactive material, and the one that matters the most in terms of decontamination is cesium 137 with a half-life of 30 years. Cesium 131, that can accumulate in the thyroid gland, has a half-life of 8 days, and it quickly changes into a non-radioactive material called xenon. Cesium 134 has a half-life of 2 years, and so 2 years after the accident, about half of it had changed into barium 134. Cesium 137 emits radiation to turn into nonradioactive barium 137. The amount of radiation with cesium 137 reduces to half the original in 30 years, a quarter in 60 years, an eighth in 90 years, and about one-tenth in 100 years. We can only count on decay of radioactivity in dealing with released radioactive material.

Under these conditions, the best practice is to acknowledge the existence of radioactive materials, take measures to minimize their impact on humans, and wait for time to pass so the radioactivity decays.

The central and local government agencies are currently working on plans to gather the soil and leaves contaminated with radioactive material and store them at designated places. The motivation is to ease people’s anxiety in living close to radioactive material without thinking about the amount of radiation. If we, however, open our eyes to reality, such measures are likely to fail. This is because areas that are named for storage and others in the route of transportation are refusing to take those roles.

5.8.2 Local storage of radioactive material

Are we out of measures to handle the situation? No, not really. We are left with one method. That is to store the radioactive material “on-the-spot” so it does not affect our daily lives.

Here we will explain the actual ways of “on-the-spot disposal.”

The simplest and most effect method is to build mounds of radioactive material (Figure 5.15a). For example, if we scrape 5 cm of soil off the surface of a 25 m × 25 m area and build a mound, its height will be 1.25 m (Figure 5.15a).

These mounds copy what our ancestors did in handling volcanic ash. Japan is a land of volcanoes and has a long history of dealing with volcanic eruptions. When volcanic ash hampered the farm work, people gathered the ash in one place and built ash mounds [5] and resumed their farm work. We can apply this ancient wisdom to decontamination. We can gather the contaminated soil and store it where it was scraped and wait for the radiation to decay. This method, however, leaves the contamination in sight of people in the area and can weigh on their minds.

The on-the-spot disposal actually done in schoolyards and some other places is “soil flipping” (Figure 5.15b). This method is effective; however, the cost and labor involved are too great, and it has not been done elsewhere.

A method similar to soil flipping is “ground plowing.” We can call this method “agricultural soil flipping,” which is not as complete as soil flipping. Ground plowing uses a plowing machine to dig into the soil and mix the surface with the soil underneath. The method is similar to flipping. However, it can only lower the air dose by mixing the contaminated surface soil with that underneath, and it is incomplete compared to flipping, which puts the radioactive material underground.

A more effective disposal method is to dig a deep hole to bury the contaminated material and cover the surface with clean soil (Figure 5.15c).

The burying method is first to open a deep hole in one corner of the land, and put the clean soil to the side. The contaminated soil is then scraped off the surface to a depth of 5 cm and placed in the hole. Once all the contaminated soil is buried in the hole, the clean soil that was placed to the side is then replaced on the top. This method hides the contaminated material from the human living space and not only eliminates the radiation effect on humans but also removes the mental burden of having to look at it.

We now look into the practicality of this burying method in detail with the authors’ assumptions. Cesium 137 (cesium in the remainder of this section) released from the nuclear reactor dissolved into water (rain), fell on the ground, and passed over the ground with water. Cesium dissolved in water travels with the water running through grains of soil. When cesium contacts the surface of soil grains, e.g., silica (SiO₂), it adheres to the crystal surface with electric force (ionic force) to make atomic bonding. Once this bond forms, the cesium does not easily dissolve into water again (Figure 5.16). In other words, the soil grains capture the cesium and do not let go.

This mechanism has been the subject of research [6]. Some evidence that supports the idea has been found in the contaminated area. Here are some examples:

• Radioactive dose is higher on the roof, in the gutter, and in concrete flow channels, and its level does not change over time.

• Brushing alone does not lower the dose level on shingles and road surfaces, unless the surface is scraped off.

• Radioactive dose is highest at the surface and drops exponentially in the depth direction. Most of the cesium is bonded to the soil within a 3 cm depth, and thus, scraping off 5 cm of soil from the surface will remove the contaminated soil (Figure 5.17).

• The distribution remains unchanged over time and only reduces exponentially with time.

• 2 years after the nuclear accident, cesium is barely detected in water streams. Occasionally heavy rain will result in a small amount of cesium. This is because cesium is attached to small grains of soil and is not dissolved in the water.

These facts (with assumptions), observed 2 years after the accident, suggest that cesium, no longer floating in midair or water, has attached itself to solid objects like soil grains or leaves and is unlikely to dissolve out into water.

We do not have to put the contaminated materials into plastic bags if cesium will not dissolve into water and we can just bury them in deep holes so they will not affect our lives. All we have to do then is to wait for the radioactivity to decay over time.

Our ideas here have not been verified; however, we believe they are on the right track. When we look at the serious suffering in areas devastated by nuclear accidents, we need to seriously evaluate such measures. We strongly hope that practical solutions like this one will make their way to becoming counter measures.

5.8.3 Looking for a practical solution

The decontamination process now gathers all the contaminated materials in one spot with plans to move them to a remote location away from our daily lives for storage. Transportation and storage will lead to conflicts among regions, and we will not reach any conclusion. If we stick to the plan of gathering and storing contaminated material in large quantities, the decontamination will stall. Then without ways to recover their former lives, local regions will stay devastated, and their recovery will be even more difficult.

We believe, with the assumption that we cannot erase radioactive materials, the most practical solution is the on-the-spot disposal method of “burying” them. We hope that the forced evacuees will initiate their own action without waiting for decisions by central and local governments. Decontamination of the mountain forests, that cover two-thirds of the entire Fukushima prefecture, has not even started. We have to decontaminate a wide range of mountain forests so people can use their houses, schools, and office buildings with confidence. The current decontamination just of areas close to houses, schools, and office buildings is not at all sufficient.

All of us must have the right understanding about dealing with radioactive material and share the knowledge. We then have to quickly find and carry out the actions that everyone agrees to, whether it is decontamination or returning home. Otherwise, delayed decontamination will further delay the returning home and other regional activities down the road.