This is the 2nd article in our Fukushima series. To read the first article in the series, please visit Fukushima: An Examination of a Nuclear Crisis.
Please check back next month for the 3rd article in this series that will discuss the implications on Japan’s trade and products in the aftermath of the Fukushima crisis.
By Harvey Farr
The Fukushima Daiichi reactor meltdowns and hydrogen explosions released approximately 15 percent of the source term released by Chernobyl as atmospheric releases from March 11, 2011 to March 17, 2011. Approximately the same amount of radioactivity has been released to liquids accumulating in the basements and trenches of the facility. Thus far, the reported liquid releases to the ocean are less than 1 percent of the total Chernobyl release, but this estimate is bound to increase. The gaseous and liquid releases have spread contamination throughout northern Japan and created extraordinary challenges for the government, industries and the population at large.
Update on the Current Situation at the Plant
Several months after the Fukushima Daiichi nuclear power plant was hit by the beyonddesign basis earthquake and tsunami, there are still a huge number of obstacles to overcome in order to get the melted cores and plant source term under control. On June 1, 2011 Kazumasa Iwata, president of the Japan Center for Economic Research, said the costs of the accident could range from nearly $71 to $250 billion. The estimate includes $54 billion to buy all land within 20 kilometers (km) of the plant, $8 billion for compensation payments to local residents, and $9 to $188 billion to decommission the plant’s reactors.
It has been determined that fuel meltdowns have occurred at Units 1, 2, and 3. Officially only Unit 1 is confirmed to have melted through the vessel and breached the Drywell at this time, but it is hard to see how the highly contaminated water containing short-lived radionuclides could have accumulated in the other two units if the same had not happened to them.
Japan’s nuclear safety agency increased estimates of the amount of hydrogen produced from 800 to 1,000 kilograms (kg) at Units 1 through 3. About 1,000 kg of hydrogen were produced in the No. 1 reactor when fuel rods began to be exposed two hours after the quake; the cladding oxidized one hour later. At the No. 3 reactor some of the cladding oxidized 43 hours after the quake, also producing 1,000 kg of hydrogen. This explains the massive hydrogen explosions that blew the tops off the No. 1 and 3 reactor buildings. The other massive explosion at Unit 4 was due to a vent line leak that allowed hydrogen from the Unit 3 reactor to accumulate in Unit 4. A smaller explosion at the No. 2 reactor damaged the suppression pool. The agency has not determined the cause of the blast in Unit 2, but calculates that about 800 kg of hydrogen was formed there 77 hours after the earthquake.
There are over 2,000 workers striving to gain control of the melted down cores and contain the radioactivity at Fukushima Daiichi. The No. 2 reactor building has 99.9 percent humidity and high levels of radioactivity, which make it hard for workers in protective gear to work inside for long periods. TEPCO planned to install air filters and run them for three days to lower the contamination and humidity, and then open the building’s doors to let out the air.
Nobuaki Terasaka, head of the NISA, told the House of Representatives Budget Committee on May 16, 2011 that there were a total of 4,956 cases of workers with internal exposure at Japan’s nuclear power plants, excluding the Fukushima No. 1 Nuclear Power Plant, and that 4,766 cases of them involved workers originally from Fukushima who had visited the prefecture after the nuclear crisis. Nagasaki University Hospital reported on June 3, 2011 that at least 40 percent of staffers and medical experts sent to Fukushima by Nagasaki’s prefectural government had internal radiation exposures. They spent approximately one week helping local government offices and medical institutions in Fukushima after the nuclear plant accident in March 2011. Fukushima wants to start screening residents for internal contamination, but the prefecture currently has only one whole body counter and can screen just 10 people per day. It is urging research institutes and others with whole body counters outside the prefecture to help them.
On May 21, 2011, the Japanese government announced it had discovered thousands of cases of workers at nuclear power plants outside Fukushima Prefecture with internal exposure to radiation after they visited the prefecture. The revelation prompted local municipalities in Fukushima to consider checking residents’ internal exposure to radiation.
TEPCO sent nine workers into the Unit 3 reactor building for about 20 minutes on June 9, 2011 to walk-down plans to inject nitrogen gas into the containment vessel and to install a circulating water system to cool the reactors. The workers withdrew after measuring radiation levels of 100 mSv/hr near the reactor’s containment vessel. TEPCO says it intended to limit the workers’ exposure to below 5 milliSieverts/hour. Because all nine workers received higher doses, TEPCO suspended work while considering a course of action.
Regrettably, worker doses exceeding the emergency worker limits of 250 mSv were announced on Friday June 10, 2011. It was determined that two workers’ internal exposures brought them over the emergency worker limits. The two men were on duty in the central control rooms of reactors No.3 and No.4 on March 12, 2011 when the Unit 1 hydrogen explosion occurred. Due to the complete loss of off-site power caused by the tsunami, it is likely that ventilation filtration systems designed to maintain control room habitability during a loss of coolant accident (LOCA) were not functioning.
On June 11, 2011, Japan’s health and labor ministry said that at least 12 plant workers had been diagnosed with heatstroke. TEPCO spokesman Junichi Matsumoto told a press conference that the company will do its utmost to make progress in the difficult work to get the plant under control. TEPCO has made great strides using temporary structures and converting existing buildings to create sleeping, dining and health clinic facilities to care for the workers.
On June 13, 2011, TEPCO announced that an additional six workers may have received radiation exposures exceeding the government’s annual limit of 250 mSv. Matsumoto, said the findings were based on preliminary assessments of 2,367 of the 3,726 people who worked at the plant in March 2011. As TEPCO and the Japanese authorities complete assessments of the internal exposures, more overexposures may be confirmed. Outside organizations have called for tighter controls on worker exposure and questioned the raising of the emergency limits from 100 mSv to 250 mSv per year.
In response to the reports of overexposures, heat stroke and deteriorating health of the workforce, TEPCO has issued a revised roadmap for recovery of the facility that includes a focus on worker health. The move imposes stricter controls on working hours and creates a system that will automatically record workers’ exposure to radiation. It will also increase the number of devices used to check possible internal exposure. More medical doctors will be on duty around the clock at the site, and new rest facilities will be added.
TEPCO has installed a circulatory cooling system for the spent nuclear fuel pool at the Unit 2 reactor building. The utility says the temperature in Units 1 through 4 have fallen below 100°C. TEPCO is also preparing to install a circulatory cooling system for a spent nuclear fuel pool in the plant’s Unit 4 reactor building. They hope to have it operational by mid-July.
Water Accumulation and Contamination
TEPCO says about 3,000 m3 of radioactive seawater has been stagnant in the basements of the plant’s reactor and turbine buildings since being hit by the tsunami. There are concerns about the corrosive effects on plant systems and equipment that may be needed for the recovery efforts. TEPCO is contemplating processing and releasing the water. The radioactivity levels are about 30 times the release limits. More than 110,000 tons of highly radioactive water has accumulated on the plant’s basements and tunnels with more accumulating every day. The amount is growing by 500 tons/day as freshwater is injected into reactors, and injected and sprayed into the fuel pools in an effort to keep them covered and cool. Heavy rains during Japan’s rainy season are also increasing water levels in the buildings, raising concerns of potential new leaks, overflows and releases to the ocean
On June 13, 2011, it was estimated that the radioactive water accumulating could overflow in about two weeks. On June 10, 2011 TEPCO had postponed a test run of a water decontamination system due to a malfunction. The system is designed to treat 1,200 tons of radioactive water a day. It uses a combination of U.S. and French processing systems to separate oil, remove cesium using zeolite, remove other radioactive constituents using coagulating chemicals, and remove salt from the initial seawater usage. TEPCO expects the systems to reduce the concentration of radioactive material in the water to one-thousandth to one-ten-thousandth of the current level. After it is processed, the water will be re-used for cooling the reactors.
The system’s final test run was suspended on June 16, 2011 after water was found leaking from a U.S.-made device that removes radioactive cesium; the device is one of the major components of the system. Company officials found that an air ventilation valve in one of the containers comprising the device had been damaged. They also discovered that a water valve in another container was closed.
On June 4, 2011, TEPCO said it found steam rising from a crevice in the floor of the Unit 1 Reactor Building that had extremely high radiation levels of 3,000 to 4,000 mSv/ hr. The company said the steam was likely coming from water at a temperature of 50°C that had accumulated in the basement of the reactor building. It is believed that the core meltdown created holes in the pressure vessel and damaged the containment vessel, causing highly contaminated water to leak out and accumulate in the basement of Unit 1. Water samples collected at the end of May from the reactor building’s basement contained 2.5 million Bq/cm3 of Cs-134, 2.9 million Bq/cm3 of Cs-137 and 30,000 Bq/cm3 of iodine-131 (I-131).
True Magnitude of Release Is Unknown
Estimates of the magnitude of the radioactive release from the damaged facility have tended to focus on the airborne fraction and have increased over time. The accident at Units 1, 2 and 4 were rated as 3 on the International Nuclear Event Scale (INES), however on March 18, 2011 the level was raised to a 5. On April 12, 2011, Japan’s nuclear safety agency raised the crisis level from 5 (TMI) to 7 (Chernobyl).
At the time, Japan’s Nuclear and Industrial Safety Agency (NISA) estimated the release at 370,000 terabecquerels (TBq) I-131 equivalents, while Japan’s Nuclear Safety Commission’s calculations estimated 630,000 TBq equivalents had been released. One TBq is equivalent to one trillion (1E+12) Bq, or 27 Curies. This placed the release at approximately 17 million Curies which was reported to equal 10 percent of the source term released by Chernobyl.
On June 6, 2011, Japan’s NISA revised the total amount of radioactive I-131 and Cs-137 released from Units 1, 2 and 3 reactors between March 11 and 17 to 770,000 TBq. Japan’s assessments at Fukushima Daiichi have been based largely on computer models showing heavy emissions of radioactive iodine and cesium from March 14 to 16. Officials have said that the emissions peaked during those days, and have dropped sharply since. There were reported fires, black and white smoke, and steam given off from the units throughout April and May. The fallout data indicates that releases continued well after May 17, 2011, therefore this estimate likely reflects a majority of the airborne release, but not the total quantity.
The airborne emissions are only a portion of the release. The melted cores and damaged fuel pools were cooled by pouring over 500 tons/day of water over them. This led to a large amount of activity escaping the primary systems and Drywells (e.g., containments) in the water that has accumulated in the basements of the Reactor Buildings, Turbine Buildings and associated pipe and electrical tunnels, pits and trenches. The estimated activity in the water accumulated in the buildings on June 3, 2011 was 720,000 TBq; that’s almost as much as the revised estimate of the radiation released into the air between March 11 and 17 at the height of the crisis. This estimate is also bound to be revised upward as has been the case with such preliminary estimates thus far.
One of the unanticipated consequences of the cooling by deluge strategy is the extent to which piping, conduits, penetrations or quake-induced cracks provided pathways for dispersal of the highly radioactive water throughout the plant. By design, this water was not supposed to escape the Drywell, torus and emergency cooling systems. Even in the event of a vessel melt-through, it was supposed to remain in the Reactor Building and re-circulate through the sumps and emergency systems to provide cooling. Given the complete loss of power, submergence and damage from the quake and tsunami, the malfunction of these systems is understandable.
But it does not explain why the Reactor Buildings were so “leaky” (i.e. highly radioactive 40 R/hr water reached the Turbine Building basements early on in the accident). It is important that this decommissioning is conducted in a way that allows examination of plant systems and structures such that a clear understanding of the design improvements necessary to prevent a recurrence of such a disaster are gained.
The radioactivity levels of the groundwater, seawater and ocean floor clearly indicate that large amounts of activity have escaped the confines of the plant as unmonitored liquid releases. On April 1, 2011 signs of groundwater contamination were reported in samples near Unit 1’s Turbine Building. Radioactive iodine 10,000 times the legal threshold was detected. On June 13, 2011, TEPCO announced that strontium-90 (90Sr) was also detected for the first time in groundwater near the reactors’ buildings. Groundwater samples taken at the plant on May 18, 2011 measured 22 Bq/liter for Unit 1 and 6,300 Bq/liter for Unit 2 for 90Sr.
Unlike the atmospheric releases, which are inferred based upon observed environmental radioactivity levels and computer dispersion models, the magnitude of the liquid releases thus far has only been estimated for known leaks using estimated leak rates, durations and actual radioactivity concentrations. Only two identified leaks have been quantified to date at 520 tons of water containing 4,700 TBq from Unit 2, and 250 tons containing 20 TBq from Unit 3. Data indicates that the releases to the ocean continued after these leaks were stopped.
The evacuations have been gradual and expanding throughout the crisis. The mandatory evacuation zone expanded from 3 km to 10 km, and finally remained at 20 km from the plant. People located in the 20 to 30-km band around the plant were advised initially to shelter, then later to leave. A timeline of the evacuation orders, warnings and advice are provided in Table 3; image 1 shows the evacuation zones.
The government has screened a large number of evacuees for contamination. On March 25, 2011, authorities reported that 66 children from near Fukushima were examined for possible thyroid exposure, but no significant exposure was identified. Similar results were reported for 1,083 children screened March 26-30, 2011. As of March 31, 2011, authorities had screened 114,488 evacuees for radioactivity; detectable radioactivity was found on 102 people but limited to their clothing in all cases. By the end of May 2011, Fukushima Prefecture had conducted radioactive screenings of more than 190,000 people, about one-tenth of the prefecture’s population.
On June 1, 2011, an independent French organization, CRIIRAD, reported air survey results of 60 mSv/year at a farm in Iitate Village. This was three times higher than the 20 mSv/year protective action guide being used by the Japanese government for evacuation and sheltering. On June 16, 2011, the government decided to evacuate areas on an individual basis. House to house surveys are being conducted in order to determine specifically in which homes occupants could exceed the 20 mSv threshold. A household that the ministry’s monitoring system shows to be at risk of exposure to more than 20 mSv/year will be examined closely to see if the house can be decontaminated. The task force that established the protocols says it is not appropriate to issue an evacuation order or restrict industrial activities in entire areas.
On June 1, 2011, it was reported that evacuees from the no-entry zone around the Fukushima Daiichi nuclear plant returned briefly to their homes to collect their cars. There were 21 evacuees from Kawauchi Village and 38 from Minamisoma City who participated in the first car retrieval operations. The participants from Kawauchi gathered in a
gymnasium to receive instructions. They then changed into protective clothing and boarded a bus that took them to their homes. They were allowed to stay in the area for about two hours and had up to 10 minutes to start their cars. Vehicles whose engines would not restart had to be left behind. Japan Automobile Federation workers accompanied the participants to help them address problems. The participants were told to keep the windows of their vehicles closed and to refrain from using air conditioners to keep out radioactive materials. After the cars were driven out of the no-entry zone, the vehicles were checked for contamination. Similar visits, in which residents of other areas were able to gather personal belongings, proceeded until June 9, 2011.
On June 17, 2011, a government panel proposed that Japan’s nuclear evacuees receive monthly compensation of 100,000 yen for mental suffering experienced during the first six months. The panel devised a draft plan for payments to people who were forced to evacuate or seek shelter by government order. The panel has yet to decide what will happen after one year of payments. The Radiation Effects Research Institute’s association, which includes a Japanese government-affiliated foundation (Radiahoping to conduct investigations on evacuees’ health over several decades. This is to improve data on effects of radiation exposure and to ease evacuees’ anxieties over radiation.
Emergency Response Preparedness Lessons Learned
It was reported on June 12, 2011 that Japanese off-site emergency response centers were unprepared to cope with the radiological conditions encountered in Fukushima. More than 15 billion yen, or $190 million, was spent to build the “off-site centers” in the wake of the September 30, 1999 criticality accident at a nuclear fuel processing plant in Tokai Village in Ibaraki Prefecture. The off-site center that was built about 5 km from the Fukushima Daiichi power plant was rendered nearly dysfunctional due to the rise in radiation levels. An investigation report revealed that officials from only three out of more than 20 required organizations assembled at the off-site center at around 10:00 PM on March 11, 2011, 7 hours after the earthquake. The office was moved to another location within four days.
NHK News contacted 14 off-site centers around the country, excluding those in Fukushima and Miyagi Prefectures, and asked them about their levels of preparedness. More than 90 percent said they did not have filtering equipment in place to prevent radioactive substances from entering the buildings, as required by law. More than 70 percent said they did not have air-lock type double doors. Off-site centers are situated between 2 km and 13 km from their plants. The government’s nuclear safety agency says it is regrettable that the off-site center in Fukushima did not function properly, and that it plans to conduct a review of how the off-site centers should be set up, based on the lessons learned from the Fukushima accident.
The International Atomic Energy Agency reported that the Japanese government’s complicated organizational structure caused it to respond more slowly than it should have to the nuclear accident at Fukushima. The agency advised Japan to streamline its regulatory structure so it can hand down decisions more quickly.
A series of anti-nuclear demonstrations were held across Japan on Saturday June 11, 2011. About 2,400 protesters took part in a rally in central Tokyo. Gathering in Minato Ward, they called for the closure of nuclear power plants and a change in the government’s energy policies.
Fallout Levels and Distribution
On June 4, 2011, it was learned that the Japanese government had early indications of widespread fallout from core damage that was withheld from the public. A reading on March 12, 2011 showed radioactive tellurium was detected 7 km away. Three hours before the data was collected, the government expanded the radius of the evacuation area around the plant from 3 km to 10 km, but the NISA reported at a news conference several hours later that the nuclear fuel was intact. The government also failed to disclose the high radiation levels in weeds 30 to 50 km from the plant. On March 15, 2011, 123 million Bq of radioactive I-131 per kilogram were detected 38 km northeast of the plant. The nuclear safety agency said it deeply regretted not releasing the data. It has been very difficult to obtain information on the levels of fallout outside the 80-km zone.
On March 19, 2011, U.N. and World Health Organization officials said there was no sign that harmful levels of radiation were drifting into Tokyo or other large cities in Japan. “Dose rates in Tokyo and other cities remain far from levels which would require action; in other words, they are not dangerous to human health,” Graham Andrew, an official with the U.N.’s IAEA, told reporters according to Reuters. The IAEA reported on March 20, 2011 that the first measurements in Tokyo by the Agency’s newly arrived radiation monitoring team the day before showed no indication of I-131 or Cs-137.
IAEA data on airborne radioactivity levels in Tokyo (Table 4) shows that the airborne radioactivity sampling started after the hydrogen explosions that occurred on or before March 15, 2011. This is well after the initial Unit 1 hydrogen explosion on the 12th. Fukushima Daiichi is 240 km north of Tokyo. A recent map (Figure 3), modified to include dpm/100 cm2) published by the DOE and Japanese Ministry shows contamination from 3 million to 30 million Bq/m2 surrounding the plant.
Tomio Kawata, a fellow at the Nuclear Waste Management Organization of Japan, said in a research report published May 24, 2011 that the DOE Map shown in Figure 3 indicates that about 600 km2 are contaminated with accumulated Cs-137 above the evacuation criteria used for the Chernobyl dead zone. Soil samples in areas outside the 20-km exclusion zone around the Fukushima plant measured more than 1.48 million Bq/m2, the standard used for evacuating residents after the Chernobyl accident.
The high contamination levels created by the fallout are creating challenges for Japan both inside and outside the evacuation areas. On June 1, 2011, it was reported that snow in the mountains in Fukushima Prefecture contained radioactive contamination at levels above the safety limit for drinking water. Researchers from Fukushima University performed the analysis with a local environmental group. They sampled snow in 31 locations and at different altitudes from seven peaks around Fukushima city, from mid-April 2011 through early May 2011. The results showed that snow in 14 locations contained more than 200 Bq/kg of radioactive Cs, the adult safe limit for drinking wa
ter. A sample of snow from an altitude of 1,300 meters contained 3,000 Bq/kg of Cs. Fukushima University Vice President Akira Watanabe warned mountain climbers not to drink river water or gather edible wild plants, now that high levels of radioactivity in the snow have been confirmed.
On June 5, 2011, it was reported that high radiation levels were detected above roadside drainage ditches in Fukushima Prefecture. Japan’s Nuclear Safety Commission measured radiation levels at 1 meter from the ground at a business district in the prefectural capital on May 24 and 25, 2011. They detected radiation of 100 μSv/hr in the mud from fallout that accumulated in the mud and leaves, and noted the need to remove the debris from ditches along busy streets.
Highly radioactive debris is still being found outside the buildings at the site. On June 6, 2011, a piece of debris about 5 centimeters in diameter with radiation levels of 950 mSv/hr was removed from the west side of the Unit 3 reactor building. So far, TEPCO has removed about 280 containers of radioactive debris from around the buildings.
The Japanese government is considering how to deal with disposal of contaminated rubble and debris within the evacuation area. Incineration and burial have been authorized in some areas. Radioactive substances have been detected in sludge at wastewater treatment facilities in at least 16 prefectures, mainly in eastern Japan. The Japanese government has issued guidelines for disposing of sewage treatment sludge that allows up to 8,000 Bq/kg (216 pCi/g) to be buried after waterproofing (e.g. solidification) steps are taken. Sludge containing more than 100,000 Bq/kg (2,700 pCi/g) is to be stored at facilities shielded by substances like concrete.
The Japanese government has started experiments on ways to remove radioactive material from farmland. One experiment is to swamp rice paddies with water in the hopes that it will wash away radioactive substances. Another idea is to plant phytoremediation crops such as sunflowers and amaranthus that are known to absorb radioactive substances from the soil.
Agriculture minister Michihiko Kano said that he hopes the methods will be effective in decontaminating farmland and that, if any prove to be effective, they will be introduced immediately. The minister and officials later sowed sunflower and amaranthus seeds at experiment sites. The plants will be tested in August 2011 to measure how much radioactive material has been absorbed.
On June 8, 2011, the Ministry of Education, Culture, Sports, Science and Technology reported conducting strengthened monitoring of environmental radioactivity levels nationwide since March 12, 2011. In order to meet recent increasing demand for the monitoring of air dose rates at 1 meter above the ground, which is the living space for people, on June 8, 2011 MEXT requested that all 47 prefectures conduct monitoring of air dose rates by using portable survey meters, in addition to other items already being monitored.
Despite the obviously high levels of contamination in the 80-km zone around Fukushima Daiichi, the Japanese government seems to be making estimates of cumulative exposure to institute the 20 mSv evacuation guide based upon air dose rates, and expressed surprise when internal contamination was reported on personnel that visited the area.
As of June 11, 2011, fallout levels across Japan were, for the most part, not detectable, except for Fukushima Prefecture, where extremely low Cs-134 and Cs-137 levels in the 6 to 7 Bq/m2 are reported periodically.
Liquid Releases and Marine Monitoring
As with the fallout data, the liquid release data is incomplete and estimates of the overall release have tended to increase with time. In April 2011, TEPCO found highly contaminated water flowing from the intakes of the No. 2 and No. 3 reactors. The company was forced to release slightly irradiated water to make space to store highly radioactive water in the facility. TEPCO estimates the total accumulated radiation dispersed in the sea is more than 4,700 trillion Bq. On May 21, 2011, TEPCO released a computer simulation showing dispersal routes and densities of radioactive water along the Pacific coast of Japan. The simulation showed contaminated water spreading southward along the coast on April 11, 2011 while maintaining its radioactivity concentration. The water had reached a point about 150 kilometers south of the plant by May 1, 2011, with the radiation density decreasing. On May 11, 2011, the water began to spread east on the Kuroshio current.
Initial indications of the severity of the leakage to the sea became apparent in late March and early April 2011. Prior to this, radioactivity detected in the limited sampling of seawater was attributed largely to fallout. JAIF reported I-131 at 180 Bq/cm3 or 4,385 times higher than regulatory limit, detected in samples taken 330 meters south of the discharge canals on the afternoon of March 30, 2011. Samples at 330 meters south of the canals tended to be higher than the samples at the canals; a general upward trend was occurring at both locations at that time. The sampling also revealed Cs-137, which has a half-life of 30 years, at a level 527 times higher than the legal standard.
On April 6, 2011, TEPCO reported they were successful at stopping high activity water, reading 100 rem/hr, from leaking into the ocean at the Unit 2 Intake Structure through a 20-centimeter wide crack in a cable storage pit. Sample results from April 5, 2011 indicated there was a major source of the seawater contamination with I-131 levels 280,000 times the 40 Bq/liter limit.
Activity levels in seawater near the plant decreased after the initial leak was stopped. A sample taken 30 meters from the plant was 600 to 1,000 times the limit, however the results dropped to less than 100 times the limit at 330 meters from the discharge canal once the leak was stopped.
TEPCO implemented engineering controls to try to contain the radioactivity in the intake structures and the plants quay. On April 13, 2011, two temporary steel plates (three plates in total) were installed to stop water from leaking out of the inlet bay, and a silt fence was installed in front of the Screen of Units 3 and 4 to prevent the spread of the contaminated water.
Seawater levels have dropped significantly in offshore samples at 30 and 330 meters to within a factor of 10 of the limits. Additional measures to reduce radioactivity being released include lowering five sandbags filled with Zeolite between the Inlet Screen Pump Room of Unit 2 and Unit 3. The utility installed fences around water intakes outside reactors 2 and 3 to prevent leaked wastewater from spreading out to sea. But as of June 9, 2011, radioactive Cs was still being found outside the fences, in amounts above government-set safety levels. The utility installed two filtering devices near the reactors’ water intakes in early June 2011. After a test-run, TEPCO plans to filter a maximum of 30 tons of contaminated water per hour from inside the fence and to discharge the decontaminated water into the sea.
On May 6, 2011, plans for an ambitious wide area survey (seawater, seabed sediment, marine air dust) off the coasts of Miyagi, Fukushima and Ibaraki prefectures was announced. The “Marine Environment Radioactivity Comprehensive Assessment Project” is being coordinated by the Marine Ecology Research Institute while it is conducting Sea Area Monitoring (mid-May to July 2011). Multiple institutes and agencies are cooperating in the extensive sampling of seawater and marine life. Sample analysis will be conducted by the Japan Atomic Energy Agency. The Marine Ecology Research Institute is taking samples in wider sea areas off the coasts of Miyagi, Fukushima and Ibaraki prefectures. This will survey the status of marine radioactivity levels and determine consistency with radioactivity concentration distribution simulations. The plan is to have the samples analyzed by the Japan Chemical Analysis Center. A chartered ship of the Fisheries Research Agency will take water samples when it conducts its resource assessment survey, which will be analyzed by the Marine Ecology Research Institute. The study will include expansion of Marine Products Monitoring by the Fisheries Agency (May onwards). In order to strengthen the radioactive substance surveys of marine products, the Fisheries Agency created the “Basic Policy on Radioactive Substance Inspections of Marine Products,” and notified related prefectures. Sea Area Monitoring by TEPCO will be included. Sampling and monitoring (of sea water and seabed sentiment), in addition to surveys conducted at an early stage along the Fukushima Prefecture coast and 15 kilometers offshore from Fukushima Daiichi NPP, will be conducted on the Ibaraki Prefecture coast.
On May 16, 2011, TEPCO reported that 90Sr was detected at a level 170 times higher than the standard in samples taken near the water intakes outside reactor No. 2. At the reactor number 3 water intakes, the level was 240 times higher than the legal safety limit. As of the beginning of June 2011, activity levels remain high at the intake structures with I-131 still present at levels up to 25 times the 40 Bq/L limits. On June 13, 2011, TEPCO reported that 90Sr, at a level 53 times higher than the safety standard, was detected in samples taken from inside an inlet used exclusively by the nuclear plant.
At the end of May 2011, Greenpeace released the results of its monitoring carried out from May 3-9, 2011, with samples analyzed at laboratories in France and Belgium. Greenpeace said radioactive materials beyond safe limits were found in 11 types of fish, shellfish and seaweed, some of which are not on the government’s checklist. It said a type of fish caught in Onahama Port in Iwaki City had 857 Bq of radioactive Cs per kilogram, 1.7 times the safety limit. Radioactive iodine and Cs beyond permissible levels were also found in oysters, sea cucumber and seaweed collected from other ports in Fukushima Prefecture. Radioactive materials were also found in seaweed drifting in waters about 50 kilometers southeast of the Fukushima Daiichi nuclear power plant. Greenpeace said its data showed contamination spreading over great distances from the plant. The Fukushima prefectural government said contaminated seafood will never reach the market because fishing has been banned in nearby waters.
Japan’s science ministry detected high levels of radioactive Cs in seafloor samples collected off Miyagi and Ibaraki Prefectures at the end of May 2011. The ministry collected samples from 12 locations along a 300-km stretch off Fukushima prefecture’s Pacific coast between May 9th and 14th. Radioactivity was found in all locations. Radioactive Cs-137, measuring 110 Bq/kg or about 100 times the normal level, was found in samples collected from the seabed 30 kilometers off Sendai City and 45 meters beneath the surface. Samples collected from the seabed 10 kilometers off Mito City and 49 meters beneath the surface measured 50 Bq, or about 50 times the normal level. Professor Takashi Ishimaru of Tokyo University of Marine Science and Technology says plankton likely absorbed the radioactive substances carried by the current near the sea surface, and then sank to the seabed. He said monitoring must be stepped up over a larger area, as radioactive materials in the seabed do not dissolve quickly and can accumulate in the bodies of larger fish that eat shrimp and crabs living on the sea floor.
As of June 9, 2011, most far-off shore readings (30 km) were not detectable. Near-shore samples have caesium-134 (Cs-134) and caesium-137 (Cs-137) at detectable concentrations, but all are below the 60 and 90 Bq/kg limit respectively.
Controversy Over Safe Limits for Schools
On April 19, 2011, MEXT released “Notification of interim policy regarding decisions on whether to utilize school buildings and outdoor areas within Fukushima Prefecture,” (2011, Sports and Youth Bureau, MEXT No. 134 dated, April 19, 2011). In the interim policy, MEXT stated it was appropriate to minimize radiation exposure to pupils and children attending schools and day care centers as much as possible, and that outdoor activities and outside school should be restricted as much as possible where air dose rates of 3.8 μSv/h or more were measured in the schoolyards or playgrounds.
Some schools near the damaged Fukushima Daiichi nuclear power plant are urging children to continue to wear long sleeves in summer to limit their exposure to radioactive fallout. The move was a response to parents’ concerns about radioactivity.
The air dose rate guide level was adopted to maintain the annual dose between 1–20 mSv. If, for 365 days, a child spends eight hours a day in a schoolyard at a dose rate of 3.8 micro Sv/h, and stays indoors 16 hours, where the dose rate does not exceed 1.52 micro Sv/h, the annual dose received would reach 20 mSv. Parents felt that the upper threshold of 20 mSv a year was unacceptable and noted that it was the same level the International Commission on Radiological Protection recommends for nuclear plant workers. It should be noted that the EPA PAG for evacuation and sheltering recommends 1 rem a year, but is flexible at 1 to 5 rem per year. The Japanese government is within the acceptable range of international standards.
Around 400 protesters, many from areas around the plant, flocked to the Education and Science Ministry to demand a rethink on the new limit. On May 23, 2011, a group of Fukushima parents visited the Education Ministry and submitted a petition bearing more than 15,000 signatures protesting the 20 mSv/year criteria. The parents wanted the government to take as many measures as possible to reduce children’s radiation exposure, such as removing contaminated topsoil from schoolyards. A ministry official admitted that the 20 mSv yearly level is not necessarily an appropriate limit for children and they will consider all possible measures to reduce radiation risk.
MEXT will aim to reduce the annual dose that pupils and others receive in school to 1 mSv or less this fiscal year. They will also provide financial assistance, under the framework of the school facility disaster reconstruction project, and will take measures to reduce the radiation doses received by pupils and others in respect to the soil of schoolyards or playgrounds, based on the results of surveys conducted by MEXT on Fukushima Prefecture. This plan targets schools where air dose rates of 1 μSv/h or more are measured in schoolyards or playgrounds, which means that soil-related dose reduction measures would be effective. Financial assistance will be provided according to the wishes of the entities that have established the schools.
In Fukushima, 15 elementary and middle schools are part of a project to remove the upper layer of soil where radiation levels measured above 3.8 micro Sv/hour, as well as 13 nursery schools where levels of over 3.0 microSv/hour were detected.
At the end of May 2011, work began to remove radioactive contaminated topsoil from school grounds in Fukushima Prefecture. The decontamination work began in 26 elementary and junior high schools in Fukushima City. The municipality says it expects the removal of the topsoil to substantially lower radiation levels at the school to about 0.6 μSv/hr.
At schools where mechanical diggers were hard to come by, parents shoveled the soil themselves. The steps produced immediate results: radiation readings in topsoil outside Ando’s school dropped from 1.32 μSv to 0.25 μSv/hr, compared to a pre-disaster reading of 0.04 μSv.
Under government rules, children should not play outdoors for more than an hour a day if radiation levels exceed 3.8 μSv/hr. “Even though the readings are better, they’re still much higher than they were before the accident. I don’t think we’ll ever be able to get back to those days,” said Oyama’s Principal, Hiroyuki Ando.
In late May 2011, Kawamata Town announced it was handing out dosimeters provided by Kinki University to about 1,500 children at local kindergartens, day care centers, elementary and junior high schools. Part of the town falls within the evacuation zone. Children will be asked to put on the monitors to measure their radiation exposure. The dosimeters will be sent once a month to check their cumulative levels of exposure. While Date City, 60 kms away from Fukushima Daiichi, is outside the evacuation zone, in early June 2011 the estimated radiation levels at preschool locations topped the evacuation level of 20 mSv/yr. The city has decided to distribute dosimeters to all kindergarteners and school children to monitor their radiation exposure. The city has allocated about $300,000 to distribute dosimeters to about 8,000 children at local schools. Mayor Nishida said that the city decided to take the broad scale measurements as parents are deeply concerned about their children’s radioactive exposure.
On June 19, 2011, about 80 parents and teachers at Tsukidate Elementary School thoroughly washed windows and verandas with high-pressure water jets and brushes to decontaminate their children’s school. Yokohama City, located hundreds of kilometers from Fukushima Daiichi, has begun radiation testing of vegetables for school lunches. The city began testing in response to parents’ concerns about whether the food served in schools is safe for their children, given the widespread fallout from the Fukushima plant.
Based on the above information, it appears that Japan is making decisions and monitoring exposures based upon external radiation levels without factoring in inhalation or ingestion using dose conversion factors from documents such as the EPA’s Federal Guidance Report Number 11. It is likely that the doses to members of the public are within the 1 to 5 rem evacuation criteria recommended by the U.S. EPA. Still, the lack of fallout data prior to March 18, 2011, the high contamination levels found in the 80-km zone, the surprise over internal depositions, and the exclusive focus on external cumulative radiation exposures indicates that better information on actual contamination and exposure levels will be obtained in the coming months.
It is apparent that the amount of radioactive material that has escaped to the environment remains to be determined. Fallout data appears to indicate releases occurred after March 17, 2011, the end date of the current estimate. The cooling strategy has created a large liquid release of activity from the reactor cores. The magnitude of the liquid release to the site groundwater and ocean remains to be determined but it is likely much larger than the estimates for the two known leaks that have been quantified.
There are lessons learned that must be considered for emergency response. The under-representation of the off-site organizations that reported to the emergency response center is understandable given the scale of the overall disaster caused by the tsunami and the strain this must have placed on local emergency response organizations. However, hardening the emergency response centers for direct radiation, airborne radioactivity and contamination control, and defining the chain of command, roles and responsibilities are valuable lessons for Japan.
The creeping expansion of the evacuation zones and the apparent failure to factor internal exposures into the 20 mSv/year protective action guide for evacuation and sheltering seems to indicate that the dose assessment and the evacuation process could continue for several months. It is also apparent that Japan faces a huge radiological clean-up effort off-site as well as on-site to deal with contaminated rubble and debris, to clean up areas and materials that concentrate cesium, and to decontaminate and reclaim domestic and commercial buildings and agricultural land. The impact on the marine life and coast of Japan around Fukushima could also have long-term impacts in a culture that is deeply connected to the sea.
The impacts of this disaster on Japan’s stagnating, export driven economy and the long-term geopolitical implications for the region remain to be seen. China only recently surpassed Japan as the world’s second largest economy. It is in all our interest to ensure as rapid a recovery as possible for Japan, and to learn as many lessons as possible to prevent and mitigate the consequences of such a disaster in the future.
About the Author:
Harvey Farr is senior project manager and health physicist for Radiation Safety and Control Services (RSCS), www.radsafety.com. He has been a nuclear power consultant since the early 1980s. Recent adventures include Fukushima situation reports for FoxNews, recommendations for Vessel Contamination Protection for Japanese ports and cargo, and supporting ZionSolutions for Zion decommissioning with short stints as acting VP Environmental Health and Safety, and as Director Radiation Protection. Decommissioning experience includes projects for Todd Shipyards, Maine Yankee, Connecticut Yankee, Yankee Rowe, Millstone I, Humboldt Bay and Bradwell in the U.K.