PART 2.3: ENVIRONMENT and DECONTAMINATION
The radioactive releases to the environment from Fukushima Daiichi are unprecedented in many respects, but also comparable in many ways to releases from other accidents and from nuclear weapons testing. Radionuclides are both persistent in the environment and mobile, and it’s of paramount importance to locate and track them as they disperse through the ocean and migrate into the soil and through watersheds, to know where to expect food species to be contaminated and by how much, and where the places where people live will require remediation, or even abandonment.
2.3.1 — Overview
The levels of radiation in the post-accident environment do not remain constant, but change over time due to physical decay of nuclides, as well as their mobility within ecosystems due to migration into the soil and through watersheds, their dispersion through the oceans, uptake and dispersion by plants and animals, and other processes known collectively as “weathering.” In this section we will deal briefly with the most relevant impacts of Fukushima radiation on the environment.
Presently the scientific consensus is very strong that approximately 80% of the fallout from Fukushima Daiichi was carried over the ocean, while the remaining 20% fell on land. Several reports of the overall releases, their likely timing, and their ultimate deposition on land and in the ocean have been issued by official agencies and other researchers. UNSCEAR analyzed and cited 16 Fukushima source term studies, and noted:
“For 131I the estimates ranged from about 100 to 500 PBq; for 137Cs they ranged, in general, from about 6 to 20 PBq.”
(A very complete list of 16 studies is given in Table B2 of the UNSCEAR report). They acknowledged that the estimate produced by a JAEA team (Terada et al ) was at the lower end of the estimates they considered, and may underestimate the total releases by a factor of about 2. But they felt it fit best with measured observations for deposition on land and so was the most useful for use in estimating doses to people. Another comparison and review of several estimates by organizations including JAEA was released in 2013 by the National Institute for Environmental Studies, and also concluded that release and deposition studies done by JAEA best fit the actually measured Cs-137 deposition pattern:
ENVIRONMENTAL SCIENCE & TECHNOLOGY: Episode Analysis of Deposition of Radiocesium from the Fukushima Daiichi Nuclear Power Plant Accident (Morino et al, 2013)
The JAEA team studying the source term has published a revision to their findings, and raised their estimate of total I-131 releases from 120PBq to 142.9PBq, and Cs-137 releases from 9 PBq to 12 PBq. The revision might lead to some small increases in dose estimates for people in certain areas, keeping in mind that the revision supports prior estimates that about 27% of the release was deposited over land, and 73% of that was over forests, not populated areas.
JAEA source term study:
Atmospheric Chemistry and Physics Discussions: Detailed source term estimation of the atmospheric release for the Fukushima Daiichi Nuclear Power Station accident by coupling simulations of atmospheric dispersion model with improved deposition scheme and oceanic dispersion mode (Katata et al, 2014)
Final version published Jan. 2015
The Science Council of Japan also published a comparison of several estimates in Sept. 2014. Prof. Jay Cullen of the Univ. of Victoria, in British Columbia, who also runs the very informative Fukushima INFORM web site, summarized the findings as such:
“1. The study estimated the atmospheric release of 137-Cs of 19.4 +- 3.0 PBq through the end of March 2011 which is in between previous high and low estimates.
2. Best estimates of direct ocean discharge of 137-Cs to the Pacific in addition to atmospheric deposition are 2.3 to 26.9 PBq and the panel could not determine which model provided the most robust estimate.
3. About 19.5 +- 5% of releases were deposited to land while about 80% ended up in the Pacific Ocean.
4. The distribution of 137-Cs in the ocean can’t be reproduced without atmospheric deposition and direct ocean releases to the Pacific.”
Cullen also notes that the Fukushima 137-Cs releases are notably smaller than the ~100 PBq released by the Chernobyl disaster in 1986.
Marine Chemist Blog : How Much Radioactive Material Was Released by Fukushima? (Sept. 08, 2014)
Science Council of Japan comparison, part 1
2.3.2 — The land environment
Odd though it may seem to say it, we were lucky that only about 20% of the radioactive releases from Daiichi ended up on land. Even that much has caused the displacement of over 100,000 people, and necessitated very costly remediation of farmland and living areas. Fortunately as well, most kinds of environmental radiation is not very difficult to detect and map. This is why SAFECAST exists.
The Japanese government released it’s first radiation map of the 80 km radius area around the plant, based on aerial surveys, in early May 2011. Results of many gov’t radiation surveys have been released since then, with gradually improving access and presentation. Nevertheless, we still feel that the maps and other data are rarely presented in a way that makes them intuitively usable by the general public.
Japan Nuclear Regulation Authority: Monitoring information of environmental radioactivity level
ExtensionSite of Distribution Map of Radiation Dose, etc.
JAEA: Database for Radioactive Substance Monitoring Data
The most recent fallout map was released by the NRA on Feb. 13, 2015.
Safecast’s radiation database includes some data readings taken from aboard ships, as well as some from aircraft (which are not included in our main maps), but over 99% are land-based readings. We are often asked how our data compares to official data, and we usually point out that during the first several of months of the disaster Safecast was often able to publish data for areas of Fukushima and the rest of Japan where little or no official data was available, and today we are still able to provide more detailed coverage than is available on most official maps. Nevertheless, the radiation levels recorded by our volunteers generally match official data within a reasonable margin of error. As our work has demonstrated, ambient radiation levels can effectively be verified by independent citizens’ groups.
To adequately verify the levels of radionuclides in the soil, however, currently requires much more expensive equipment. Cesium and other gamma-emitting nuclides in soil can be adequately measured with equipment similar to that used for measuring food, though detecting strontium, for instance, is a several-day process within the capability of only very sophisticated labs. Many soil contamination maps have been released by Japanese gov’t agencies, including several for Sr-90 and Pu-238, Pu-239, Pu-240, and some university-based researchers have done their own analyses. While few specialists believe that enough soil sampling has been done for these nuclides, it is generally accepted that the overall ratios of cesium to strontium have been adequately characterized. Nevertheless, because these ratios will change over time due to the differences in physical half-life as well as mobility in the environment, improved monitoring is important.
The Minna no Data project has begun an independent crowdsourced soil survey. Not much data is available yet, but over time this should prove to be a valuable resource.
Minna no data soil measurement project.
2.3.2.a — Forests
About 70% of the fallout that fell over land ended up in forests, which will be impossible to effectively decontaminate, and where it will remain bioavailable to plants and wildlife for decades. Radionuclides have essentially hijacked the watershed, turning it into a cesium delivery system (while delivering smaller amounts of other nuclides as well). Fortunately researchers have a lot of experience tracking them in these environments.
It is estimated that the majority of the radioactive substances which fell over land in Japan fell on forested mountains. This is a mixed blessing. It is fortunate because population in Japan, including in Fukushima, is concentrated in valleys and on plains, and the mountains themselves are very sparsely populated. It is unfortunate because most observers have concluded that it will be impossible to adequately decontaminate the forests themselves, and so for many coming years — decades — dose rates in the forests will be higher than elsewhere, sometimes significantly, and people will need to exercise adequate caution when entering them.
Basically, trees and other biota continually recycle cesium and other nuclides within the ecosystem. Typically, for instance, radioactive substances are taken up by tree roots, and a portion ends up in the leaves. These fall and form a layer of ground litter on the forest floor, and as they decay the nuclides migrate into the soil again, where they can be taken again up by roots, thus perpetuating the cycle. Some species, such as mushrooms, easily take up cesium, for instance, and when these are eaten by forest animals some is deposited within their bodies, but all is eventually excreted, and can become bioavailable in the soil again. Nuclides can enter streams and ponds along with mineral and organic matter, and much of it will be transported through the watershed and eventually to the ocean, while a significant portion will end up in streambeds and lakebeds and stay there for years. Near inhabited areas, it has been effective to clear away the contaminated ground litter, and if this is repeated regularly long-term reductions can be made. It is because this is infeasible in most of the mountainous forested areas themselves that it will necessary to restrict access to them until natural radioactive decay and transport have resulted in sufficiently reduced radiation levels.
Environment Ministry info pamphlet about forest contamination (in Japanese)
Several good studies of the radioactive change processes in forests and watersheds affected by the Fukushima disaster have been released:
Forest studies:
Kato et al, 2014
Murakami et al, 2013
Ohte et al, 2013
Hashimoto et al, 2012:
Watanabe et al, 2012:
MEXT, 2012:
Watershed studies:
Evrard et al, 2013
Yamashiki et al, 2014
Lepage, Evrard, et al, 2014:
Chartin Evrard et al, 2013:
NOTE: An increasing amount of data is also available concerning effects observed so far in other animal species in Fukushima, including insects, birds, and mammals. These will be summarized in an upcoming revision to this report.
2.3.2.b — Decontamination progress, plans, effectiveness
The area needing to be decontaminated is huge. When we investigated the results of the techniques being used two years ago, we concluded that it was only partly effective, and that in many situations it made more sense to wait for natural radioactive decay to take its course. In some cases decontamination appears to be what we call an “optical” solution — to show that efforts are being made. But much of the time it can make a big difference in radioactive exposures and doses. Regardless, it’s a management and communication nightmare, and we’re not surprised many residents remain skeptical.
The policies and practices which drive decontamination are rooted in decisions made regarding the health and safety of affected residents, particularly evacuees. Decontamination has been controversial from the start, and has suffered from a lack of transparency in much of Fukushima. We published a long blog post in August, 2013 explaining the thinking behind the official policies and guidelines and evaluating the effectiveness of the techniques. Most of what we wrote then is still valid, and readers interested in knowing more about the policies and the overall background behind the present situation should refer to that post:
Decon or con: How is remediation being managed and how effective is it? (Aug. 2013)
— Issues and problems
Among the most widely cites issues with the decontamination process are:
- Claims that the targeted radiation levels are not low enough to ensure adequate safety
- Inadequate oversight
- The generation and temporary outdoor storage of tons of contaminated debris.
- Lack of responsiveness to requests by citizens for more thorough decontamination to be done of “hot spots” in specific areas.
This situation is ripe for abuse, and back in January, 2013, the Asahi Shimbun published a scathing series of exposes detailing sloppy work practices and fraud, titled “Crooked Cleanup”:
Asahi Shimbun: CROOKED CLEANUP (1): Radioactive waste dumped into rivers during decontamination work in Fukushima, Jan. 04, 2013 (paywalled)
In January, 2013, after these revelations were made, the Environment Ministry issued revised guidelines which presented “Lack of viewpoints of locals and third-parties” as one cause of problems, and suggested “Effective monitoring by a third-party etc.” as part of the solution.
Env. Ministry: Securing Appropriate Decontamination Works, Jan 2013
Since then, we have asked Environment Ministry representatives on several occasions what the procedure was for becoming a third-party monitor. As recently as Feb. 2015, the reply has been that this has not yet been implemented. Usually, the representatives we’ve spoken with are chagrined to admit this, because many of them recognize the need and feel that it will help lead to better results overall as well as greater trust. We intend to keep asking.
— What’s completed so far?
As we explained in our “Decon or Con” blog post, decontamination of areas which were subject to evacuation orders, known as the “Special Decontamination Area,” which includes 11 municipalities in all, is done under the jurisdiction of the central gov’t, specifically the Environment Ministry. All other areas are grouped in to the “Intensive Contamination Survey Area,” and decontamination there is the responsibility of the respective local governments, with financial and technical support from the central government. This area includes 100 municipalities in 8 prefectures where additional exposure doses exceeding 1mSv/y of were measured, 39 of them in Fukushima, and as far away as Gunma, Saitama, and Chiba.
A total of 13,000 sq. km. (a bit smaller than the state of Connecticut) both inside and outside of Fukushima was over an additional 1 mSv/yr in Nov 2011, and designated for either full decontamination or survey for “hot spot” decontamination:
Asahi Shimbun: Area over 1 mSv per year includes 3% of Japan’s land area, in 8 prefectures. Oct. 11, 2011 (in Japanese)
Information on overall progress can be found at the Environment Ministry’s “Decontamination Information Plaza” website:
Decontamination Information Plaza, main Japanese page
Offsite Decontamination Measures, English info
We pointed out some of the problems with this site and the information it provides back in 2013. It has gradually become more easily usable, but while an effort is being made to have complete and up to date information available, it’s necessary to examine data for each municipality separately, and so it’s difficult to get an overall picture of the current state of progress. Very few dose-rate maps are provided, either.
For the “Prepare to return” (green) and “Residence prohibited” (orange) parts of the evacuated areas, decontamination was declared completed in the towns of Kawamata (houses only), Tamura, Kawauchi, Katsurao (houses only), Okuma, and Naraha in 2014. Kawamata and Katsurao are scheduled to be fully completed in fiscal 2015, and the portions of the other towns which lie in these zones, Iitate, Minamisoma, and Tomioka, are scheduled to be completed in 2016. No decontamination is scheduled yet for the “Difficult to return” (red) zone, nor for nearly unpopulated mountainous portions of Namie and Minamisoma which lie in the orange zone.
Env. Ministry: Decontamination schedules and progress (in Japanese)
In other words, the government expects to complete all decontamination in areas it intends to reopen for evacuees to return to by 2016. This does not mean that ambient dose rates will be reduced to 1 mSv/yr throughout these zones. It also does not mean that no further decontamination will be attempted. Rather, the current thinking is that as long as personal dosimetry results can demonstrate that the majority of the returnee population will incur doses not much above 1mSv/yr, it will be possible to use individual dosimetry results to counsel each person about how to further minimize their doses. Based on what we have seen, the central government does not intend to produce an approved “counseling manual” but has been encouraging local governments to develop their own programs based on local community experience.
As mentioned above, no decontamination is planned yet in the “red” zone, and no timetable has been officially proposed for the return of evacuees to these areas. Nevertheless, based on conversations we’ve had with knowledgeable people, we would not be surprised if the government ordered selective decontamination in some places in this zone a few years from now in the hopes that people who wanted to return could be allowed to do so by 2020. Such a decision, if in fact it is made, will surely be very controversial.
— How much land area has been “decontaminated” at least once?
— In Fukushima (as of March 2015)
In the “Special Decontamination Area” (original evacuation zone), 11 municipalities total:
Total are to be decontaminated: 248 sq km
Decontamination completed:
— Tamura, Kawauchi, Naraha, Okuma
— Total target area: 3500 ha. (35 sq km)
In progress:
— Katsurao, Kawamata, Minamisoma, Iitate, Namie, Tomioka, Futaba
— Total target area: 21,300 ha (213 sq km)
39 municipalities in Fukushima outside of the evacuation zone (in the “Intensive Contamination Survey Area”):
— Work is in progress in most, and has been completed in 3.
— Outside of Fukushima
60 municipalities in Iwate, Miyagi, Ibaraki, Tochigi, Gunma, Saitama, and Chiba (in the “Intensive Contamination Survey Area”):
— Work is in progress in most, and has been completed in 11 towns in Ibaraki and 6 in Gunma.
— Decontamination completion breakdown by category, in Fukushima (as of November 30, 2014):
Households:
185,478 (59.9% of 309,718 planned by end of 2014)
Farm fields :
21,164 ( 70.7% of 29,920 planned by end of 2014)
Public facilities:
6,402 ( 77.5% of 8,263 planned by end of 2014)
Roads:
3,061 km (36.4% of 8,421 km planned by end of 2014)
Most recent info sources:
Fukushima prefecture:
Steps for revitalization in Fukushima Jan 2015
Environment Ministry:
Decontamination progress information, by municipality(in Japanese)
Japan’s Decontamination Efforts and its Effects, July 2014
Progress on Off-site Cleanup Efforts in Japan, Jan 2015
— Interim storage facility
From the start, the problem of where to put soil, plant matter, and other debris removed in the process of decontamination has posed great difficulties. More than one expert we spoke with in 2011 suggested that it made the most sense to deposit it in the most contaminated areas, where it would not measurably increase the overall radiation levels, and, because these areas were expected to be closed to human habitation for a long time, would pose the least additional risk to people. In effect a plan which accomplishes this has gone forward, but as with almost every aspect of post-disaster recovery, it has been fraught with difficulty and delays.
Environment Ministry explanation of interim storage plan, 2014 (in Japanese):
Currently, decontamination debris is stored in large bags stacked in large mounds in about 75,000 locations across Fukushima, where they now form a familiar part of the landscape of nearly every town. The government has rented these temporary storage plots from the landowners, in most cases with the stipulation that the debris would be removed within 3 years, at which point an “interim” storage site, where the debris would be processed and kept for 30 years, was expected to be ready.
A 16 sq. km site, roughly the same size as Haneda Airport, surrounding Fukushima Daiichi and straddling the evacuated towns of Futaba and Okuma, has been selected, and detailed plans completed. While the prefectural and local governments have approved the plan, landowners have been reluctant to sell their land, and only 0.4% of the necessary land (0.6 sq km) has been secured for use. Contact information for only roughly half of the 2365 landowners has been determined, and most of those who have been approached have refused so far. Regardless, the first test hauls of soil were scheduled to begin on March 13, 2015. 43,000 cubic meters of soil, about 0.2 % of the total that needs to be moved, are expected to be carried in during the first year as transportation tests.
Fukushima Minpo News: Construction work begins for interim nuclear waste storage in Futaba, Okuma towns, Feb. 4, 2015
When completed, the interim storage site will include covered landfill for contaminated soil, constructed differently for soil above and below 8000 Bq/kg; “volume reduction” facilities, a euphemism for incinerators to reduce tree branches and other burnable debris to ash, which can be more easily stored; secure concrete storage buildings for casks filled with waste over 100,000 Bq/kg, such as the incineration ash; water purification facilities for groundwater that might be affected; sorting facilities; and administration and other buildings. When in full operation, this will be a very, possibly unprecedentedly, large landscape devoted to radioactively contaminated waste. Nevertheless, upon examining the proposed plans, technical experts we have consulted have said that the facilities represent the state of the art and reflect a high consideration being given to safety and minimizing further consequences to the environment.
Safecast has been establishing a network of fixed, realtime radiation sensors in Fukushima and elsewhere, and believe this site should have robust third-party monitoring of both air and water. Further, no consensus has been reached about what to do with the debris after the specified 30 years have elapsed. Some proposals, such as to send it to other prefectures to be used in land reclamation and road construction, are certain to face enormous public opposition. On the other hand, it is difficult to predict what public sentiment might be like, and what technological options might be available, 30 years from now.
— Decontamination cost estimates:
It is challenging to find up-to date information on costs for most aspects of the disaster. Several different agencies as well as TEPCO each prepare their own budgets and provide summaries, but determining how much money various agencies provide to each other and to Fukushima Pref., for instance, is extremely difficult.
In March 2014, NHK compiled estimates from the government and TEPCO, and provided a summary of expected total costs, including ¥2.5 trillion for decontamination:
NHK: Cost of the nuclear powerplant accident after three years: 11 trillion yen (in Japanese)
These figures are fairly close to others compiled by Prof. Oshima of Ristumeikan Univ, in October 2014 - ¥2.48 trillion- quoted in this article by former Prime Minister Kono Taro:
Huffington Post: What is the true cost of nuclear power? Taro Kono, Oct. 17, 2014
These can be compared to the early estimate of ¥1.15 trillion released in Dec 2011 by the Cabinet Office:
Report of cost verification committee, Dec. 19, 2011
Finally, in Feb., 2015, Environment Ministry staff in Fukushima told us that the official cost estimates were: — ¥2.5 trillion for decontamination — ¥1.1 trillion for the interim storage site
(Our thanks to Antonio Portela for assistance in compiling this data)
— Travel in the area
Route 6 reopened:
Since shortly after the start of the accident, a 14 km section of Route 6, which passes through the towns of Tomioka, Okuma and Futaba in the “Difficult to return” evacuation area near the Daiichi plant, had been closed to normal traffic, but was reopened at midnight on Sept. 14, 2014. Prior to this, people wanting to travel from Iwaki and other towns on the coast to the south of the plant, to Minamosoma and other towns north of it, were forced to take a long detour to the west that required three or more extra hours of driving. The reopening of this stretch of road has made north-south travel through the coastal part of the prefecture immensely easier. Side roads remain closed except for people with necessary permits, and due to a higher risk of radiation, people are not allowed on this stretch of road on motorcycles, bicycles, or on foot. Safecast volunteers soon uploaded data from the area showing dose rates over 5 uSv/hr..
Fukushima Minpo News: Vehicle ban on part of Route 6 lifted, entire highway reopened to traffic, Sept. 15, 2014
Joban expressway open:
The Joban Expressway runs close to the coast from Saitama Prefecture through Tohoku. Nearly complete at the time of the disaster, a 14.3 km section in Fukushima between Tomioka and Namie remained undone, and work on it essentially came to a standstill due to radiation risks and other priorities. The final section was opened for public use on March 1, 2015. Decontamination and construction techniques intended to reduce doses to travelers were implemented; Safecast volunteers logged radiation levels over 7 uSv/hr soon after it was opened.
WSJ: Highway to Open Near Fukushima Nuclear Plant; No Exits Allowed, Feb. 19, 2015
Rail lines:
Prior to the disaster, primary coastal rail service in Fukushima was provided by JR East’s Joban Line, which connected Ueno Station in Tokyo to the Tohoku region. Service on this line has been restored except for a section between Tatsuta and Haranomachi, which runs through the “Difficult to return” evacuation zone (including the towns of Tomioka and Namie), and one between Hamayoshida and Komagamine, further north of the plant near the town of Soma. Inspections and repair work are currently underway to restore service to all but the section between Tomioka and Namie. A bus service was begun between Tatsuta and Haranomachi on Jan 31, 2015. Meanwhile, Tomioka Station, which had stood in a partially destroyed, overgrown state since 2011 and has drawn many journalists and visitors, was dismantled in March 2015.
Other rail service in Fukushima has been restored.
JR East: Expected impacts of the Great East Japan Earthquake on train operation, Jan. 31, 2015
JR East: Overall damage situation in areas preparing for the lifting of evacuation orders, June 17, 2011
JR East: Concerning service between Hamayoshida and Komagamine, Sept. 27, 2012
2.3.3 — The Ocean
The radioactive releases from Fukushima Daiichi to the ocean were huge, but not necessarily unprecedented. Many teams of oceanographers have been tracking and sampling the nuclides as they make their way across the Pacific, and predictions they made two years ago about how long it would take the ocean “plume” to reach the coast of North America, and how much cesium would be in it when it got there, have proven to be very accurate. As predicted, the levels are lower than in the 1970’s. But the plant is still leaking and major releases of contaminated water cannot be entirely ruled out. Meanwhile, the radioactive contamination on the seabed off the Fukushima coast has been mapped, and experts agree that only time will reduce the ongoing impact on marine species there, including many dining table mainstays. Close monitoring of the ocean environment is extremely important and will continue to be for years to come.
2.3.3.a — Measurement overview
Since most of the radioactive releases from Fukushima Daiichi ended up in the ocean, either as fallout from the air or directly through contaminated water leaking from the site, they have warranted close scrutiny and monitoring. Because there have been large previous releases of radioactivity to the ocean, such as from nuclear weapons testing, from the Chernobyl accident, and from nuclear sites such as Sellafield in the UK, as more data has been gathered since 2011 it is becoming possible to make reasonable comparisons. Oceanographers from several countries have been monitoring radiation levels in the ocean for decades, since well before the Fukushima disaster, and their historical data and understanding of how these materials disperse through the ocean environment is crucial to our understanding.
Oceanographic survey teams sprang into action soon after the start of the Fukushima accident, and the hard data they have collected since then has helped fill in gaps in our knowledge about the quantity and composition of the radioactive releases, and to predict the levels of radioactivity that will reach other countries around the Pacific rim, and when. Future large releases are not out of the question, however, so while the situation is steadily improving now, there are imaginable scenarios in which it could possibly become worse again.
Some reliable estimates of Cs-137 levels in the ocean for comparison are (not including Sr-90 or other nuclides): — N. Pacific 2011 (pre-accident), remaining from testing: 76 PBq
Initial releases: — Fukushima to atmosphere (high estimate, Stohl et al) 23–50 PBq — Fukushima atmos to ocean (Aoyama, 2013) 15 PBq — Fukushima Direct to ocean, most common estimates 15–30 PBq
Ongoing water releases: — From rivers per year (Buesseler, 2012) less than 0.012 PBq — From groundwater per year (Aoyama, 2013) 0.01 PBq — 10 years at these rates combined: 0.22PBq
Highly contaminated water in the lower levels of the power plant (rough estimates): — (Nishihara, 2011, Ebisawa, 2012): 140- 276 PBq
It’s worth comparing these to what has been released at Sellafield: — Sellafield to ocean total (mainly Irish Sea): 39 PBq — Sellafield to ocean 1975 (Norway gov. data) per year: 5 PBq — Sellafield to ocean now per year: 0.001 PBq
In the following sections we will briefly describe what recent survey data shows about radiation levels in the ocean and seabed within 100 km of Fukushima, and in the deep ocean beyond that.
2.3.3.b — Within 100km
Most of the available data for waters within the 100 km zone is from Japanese government agencies, researchers working under Japanese government grants, or from TEPCO, but some independent surveys have also been done. There have been instances in the past of ocean researchers not being allowed to publish their Fukushima-related data, but none have come to light since 2012. When compared to independently collected data, measurements published by government agencies and by TEPCO have generally held up, and problems are usually ones of omission — locations for which data should probably be made available but is not. Regardless, we are gradually able to form a fairly clear picture of what is happening both in the water itself and on the seabed.
This detailed 2014 document from the Nuclear Regulation Authority of Japan (NRA), drawn up in conjunction with several other agencies, explains what is measured where, how frequently, and by whom:
NRA: Implementation Guides on Sea Area Monitoring, April 01, 2014
Monitoring in the port area of Daiichi itself is done by TEPCO weekly. Samples are taken by TEPCO or a governmentt agency from about 20 set locations within 2 km of Daiichi on a weekly basis in most cases; from about 30 locations within 20 km of on a weekly, biweekly, or monthly basis; and from about 30 locations within 100 km on a monthly basis, in addition to another 31 points immediately offshore of Fukushima Prefecture, also on a monthly basis. Ocean sampling of nearby prefectures is done at intervals ranging from biweekly to once every 6 months, depending on location. In addition, about 10 points within 300 km are sampled once every 6 months, and another four within 1000 km are sampled yearly. Both seawater and seafloor sediment in Tokyo Bay, Sendai Bay, and areas off of the mouths of major rivers are also monitored several times a year.
The following documents provide good graphs of how radiation levels in seawater have changed at several offshore sample points since March, 2011. To summarize the findings: within 20 km of Daiichi concentrations of Cs-124, Cs-137, and I-131 reached as high as 100,000 Bq/L in March 2011. The I-131 decayed and disappeared within a few months, while the Cs levels had dropped to approximately 10 Bq/L a year later. As the graphs show, since 2013 they have occasionally exceeded 10 Bq/L within 20km at some points, but have generally been 1 Bq/L or lower. At 20–30 km, and out to 100 km, since 2012 they have consistently been 0.01 Bq/L or less. Between 100–300 km, they have consistently been between 0.001–0.01 Bq/L.:
NRA:Change of the radioactivity concentration of the seawater in off-shore sea area (bet. 30–100 km)
NRA: Change of the radioactivity concentration of the seawater in outer sea area (bet. 100–300 km)
Recent results:
— Daiichi Port test results:
TEPCO’s port water test results from March 13, 2015, show that cesium was detected at low concentrations (1.3- 7.5 Bq/L) at 4 of the 8 sample points, and was undetected at the others. Tritium, maximum levels of 11Bq/L, was detected at 7 of the 8 points, and gross beta, maximum of 41 Bq/L, at 4 points. Water in the inner port (intake channel) is moderately higher, with consistent single or double digit detections of both Cs134 and Cs 137, tritium up to 460 Bq/L, and gross beta up to 140 Bq/L:
Recent tests from the immediate vicinity outside the port show Cs undetected at all but 1 of 7 locations, up to 11 Bq/L of gross beta at two locations, and 1.7 Bq/L of tritium at one:
While these levels are currently quite low considering the ongoing contaminated water problems onsite, test results in this area frequently show higher levels. It is possible that TEPCO does not report sampling results from some locations which are more likely to give higher readings, and that occasional releases that happen during the intervals between testing may go undetected. The standard disclaimer that there is no independent verification of these results applies.
— Test results between 2–100 km:
This NRA document from March 10, 2015 gives detailed recent test results for sample points between 2–100 km.
NRA: Sea Area Monitoring, March 10, 2015
— Within 2 km: Cesium is either undetected or below 1 Bq/L at 12 sample points; similar for other nuclides.
— Between 2–20 km: Cesium is either undetected or below 0.1 Bq/L (most below 0.01 Bq/L) at 28 sample points; similar for other nuclides (at 11 samples points at which they were tested for).
— Between 20–100 km: Cesium is either undetected or below 0.01 Bq/L at 40 sample points, detected at below 0.1 Bq/L at one point; similar for other nuclides (at 11 samples points at which they were tested for).
— Seabed test results
As it does within watersheds on land, through biological and physical processes a portion of the cesium and other radionuclides in seawater eventually settles into sediment on the seabed. This is of concern primarily because it becomes bioavailable there to bottom-feeding species, such as flounder, as well as many filter feeders, such as shellfish, and remains in the foodchain. For this reason even in areas where most marine species show little or no radioactive contamination, bottom feeders might be high enough to be of concern. This has been borne out by seafood testing of fish caught near Daiichi. Monitoring of seabed sediment is therefore very important.
Currently, seabed monitoring is being done by government agencies, by the Japan Coast Guard, and by other researchers. Not surprisingly these have revealed the existence of seafloor “hotspots” not unlike those on land, sometimes at a surprising distance from Daiichi itself. Excellent work is being done to map the radiation on the seabed, and to understand the processes by which undersea hotspots form.
— — Seabed data from TEPCO
Recent seabed sampling by TEPCO of 43 locations, mostly within 20 km of Daiichi, show that while combined Cs-134 and Cs-137 levels at most sample points are below 100 Bq/kg, they reach as high as 800 Bq/kg at a handful of locations. As other sampling has shown, points on the seabed farther from the plant can be higher than those closer to it:
— — Seabed data gathered by ocean researchers:
Some of the most informative data on seabed radiation comes from a team of researchers from the University of Tokyo, the National Maritime Research Institute, and Kanazawa University, who used a newly developed towed gamma ray spectrometer to map radiation and seafloor topography in an offshore area of approximately 50 km by 25 km. While they found an average concentration of Cs-137 of about 90 Bq/kg, they found 20 locations 4km offshore which were over 1000 Bq/kg, and others 6 km offshore as high as 2000 Bq/kg. In addition, locations surveyed off the mouth of the Abukuma River in Miyagi showed 1300 Bq/kg (at 1.6 km) and 2700 Bq/kg (at 2.5 km). Previous studies have identified seafloor hotspots of a few hundred Bq/kg as far as 15 km offshore.
These researchers determined that the hot spots occurred in places where the seabed has muddy depressions, as opposed to being sandy or rocky, and depends on particular patterns of current flow. The researchers also identified similar hotspots south of Daiichi, which they suspect is most likely due to cesium deposited there by currents during the first weeks of the accident.
Seafloor survey map showing undersea hotspots 15 km offshore.
Marine Pollution Bulletin: Distribution of local 137Cs anomalies on the seafloor near the Fukushima Dai-ichi Nuclear Power Plant (Thornton, et al, 2013)
Seafloor sediment monitoring (Thornton, et al, 2013)
See also:
Biogeosciences: Spatiotemporal distributions of Fukushima-derived radionuclides in nearby marine surface sediments (Kusakabe, et al, 2013)
— — Seabed data from the Japan Coast Guard:
The Japan Coast Guard has been monitoring seawater nuclides since 1959, and seabed nuclides since 1973, and to date have released post-accident data for surveys done in 2011, 2012, and 2013. The seabed sampling focuses on important coastal cities, but there are no sampling points close to shore between Tokyo and Sendai, and so no coastal sampling for Fukushima (though they sample water at several points further out to sea). They give almost no interpretation of their findings, but simply report the levels and whether changes were detected compared to previous years.
The Coast Guard regularly samples 8 seabed locations. In their 2013 survey, Cs-137 was detected at all 8, all of which had less than 10Bq/kg concentrations, except for Tokyo which had 55 Bq/kg, and Sendai which had 246 Bq/kg. Cs-134 was detected only at Sendai (107 Bq/kg), Tokyo (22 Bq/kg), and Niigata (2.5 Bq/kg). The implication is that the Cs-137 in places where no Cs-134 was found is not from Fukushima but predates it, and is probably leftover from nuclear testing or Chernobyl. It should be noted that overall the Cs levels in the seabed off Japan are higher than they were in 2011, and have declined slightly since 2012. This reflects the process of continued deposition from rivers which feed into Tokyo and Sendai bays, which has been confirmed by other researchers. On the other hand, the Coast Guard data also shows that Cs levels in seawater spiked in 2011 and quickly declined afterward. Radiation in the seawater at the points sampled is generally lower than at anytime prior to 2002.
Sr-90 was also detected at all seabed sample points, in the range of 0.020–0.099 Bq/kg, an order of magnitude lower than it was immediately following the Chernobyl accident. This makes it difficult to say what proportion of it is due to Fukushima. Most specialists agree that the Sr-90 currently being detected is most likely primarily residual, leftover from nuclear tests and the Chernobyl accident.
The Japan Coast Guard radiation monitoring reports (in Japanese) can be found here:
Japan Coast Guard radiation monitoring reports, top page
2011 radiation monitoring report
2012 radiation monitoring report
2013 radiation monitoring report
2.3.3.c — The wider Pacific:
A lot of attention has been given to the potential effects of Fukushima radiation in the Pacific Ocean as a whole, and on the west coast of North America in particular. SAFECAST published a lengthy report about this on our blog in January, 2014, most of which is still applicable, and has been confirmed by more recent findings. It gives citations for many relevant studies, and we recommend that interested readers consult it:
Fukushima Across the Pacific, Jan. 2014
As we said at the time, several teams of ocean scientists have been closely monitoring the progress of the ocean “plume” as it crosses the Pacific. These scientists reached a consensus in 2012–2013 that the the Cs-137 levels in the waterborne Fukushima radiation now reaching the North American Pacific coast will peak at between about 0.004 and 0.010 Bq/L, compared to about 0.001–0.002 Bq/L before the accident, will stay that way for a few years, and should start declining again around 2017. Percentage-wise this means it will be 2 to 10 times the pre-existing Cs levels, which we could consider is a lot, especially since the entire Pacific will be affected.
Graph showing predicted levels of Cs-137 in the Pacific over a decade. Black represents the western Pacific; green: North America; light blue: Hawaii; blue: Baja California; red: Aleutians.
While Fukushima released quite a lot of Cs-137 to the oceans, the amount appears to be comparable that from Chernobyl, about 1/10 of that from global testing, and only a tiny fraction of the natural radiation (mainly Uranium 238 and Potassium 40) that has always been there.
Some of the post-Fukushima Pacific Ocean studies are simulations that begin with estimates of how much radiation was released, where the wind and ocean currents are likely to have taken it, what resulting ocean contamination can be expected, and how it is likely to change over time. Other studies are primarily based on measurements of seawater at different depths, and of the seabed, which can be used by researchers doing simulations to cross-check their assumptions and conclusions, and to refine their simulations. Because the methodologies and the aspects taken into consideration vary from study to study, different simulations result in slightly different estimates of the level of ocean contamination the Pacific will experience. But they all agree that while the increase in radioactivity in the ocean off Hawaii, Alaska, and California will be measurable, it will also be very small.
As a press release from the Woods Hole Oceanographic Institute pointed out, “This is an evolving situation that demands careful, consistent monitoring to make sure predictions are true.”
A very good study published in Feb. 2015 by scientists associated with Canada’s Department of Fisheries and Oceans describes the movement of the Fukushima ocean plume (technically called a “radioactivity signal”) across the Pacific, and its current status:
They conclude:
— It arrived at a sample point 1,500 km west of British Columbia, Canada, in June 2012.
— It had spread onto the Canadian continental shelf, i.e., close to but not reaching the coast, by June 2013.
— By February 2014, it had increased to a value of 2 Bq/m3 (0.002 Bq/L) throughout the upper 150 m of the water column, resulting in an overall doubling of the pre-existing fallout background from atmospheric nuclear weapons tests.
— The total levels of Cs-137 off the North American coast will likely reach maximum values of 3–5 Bq/m3 (0.003- 0.005 Bq/L) by 2015– 2016, similar to the levels that existed there during the 1980’s.
— By 2021 the levels will decline and become closer to the pre-Fukushma fallout background of about 1 Bq/m3 (0.001 Bq/L).
This research also confirms that the best predictions made by others in 2012–2013 have been on the whole very accurate.
PNAS: Arrival of the Fukushima radioactivity plume in North American continental waters (Smith et al, 2015)
— Good sources of information about ocean radiation:
Dr. Ken Buesseler and his team at Woods Hole Oceanographic Institution (WHOI) were some of the first researchers to monitor Fukushima radiation in the ocean, and to try to effectively inform the wider public about what was happening. The WHOI website has several informative articles about the Fukushima issue:
WHOI Oceanus: Special feature, “Fukushima and the Ocean,” 2013
WHOI: FAQ: Radiation from Fukushima, last updated August 26, 2014
WHOI Oceanus: How Is Fukushima’s Fallout Affecting Marine Life? May 2, 2013
WHOI Oceanus: Radioisotopes in the Ocean: What’s there? How much? How long? May 1, 2013
In addition, WHOI began a citizen science program to sample water on the Pacific coast of North America and elsewhere, called “Our Radioactive Ocean.” The program has been extremely successful so far, and the results of dozens of samples taken by individuals and groups who have supported the project can be seen on the project website:
Another excellent source of information is the Fukushima INFORM website, which has very informative and up-to-date summaries of recent scientific findings compiled by Dr. Jay T. Cullen of the University of Victoria in British Columbia. The INFORM project is also citizen science based, and is building a network of volunteers to collect monthly samples for the next three years, which will be analyzed at university laboratories, and will help us understand the arrival and intensity of the Fukushima contaminated seawater plume. The project includes both seawater and biota.
Fukushima INFORM top page
Fukushima INFORM: More Citizen Science Seawater Monitoring Results: No Fukushima Contamination Detected, Feb. 16, 2015
Fukushima INFORM: Monitoring Results For Sockeye Salmon and Steelhead Trout Collected Summer 2014, Dec. 1, 2014
— Summary:
Because the bulk of the radioactive releases from Fukushima ended up in the ocean and not on land, they have been less directly bioavailable for humans than ground contamination has been. The store of historical knowledge and experience about marine radioactivity which oceanographers have been able to provide also works in our favor, in terms of monitoring changes and predicting effects. The ocean is a very complex set of systems, and is imperfectly understood, but we feel the challenges are greater on land where food is grown and most people actually live. Also, the way radionuclides quickly disperse in the ocean stands in marked contrast to how they are actually stored and recycled in forest environments. In that sense, and in many others, we were lucky. But there’s no room for complacency.
Looking at the big picture, the continuing releases from Daiichi to the ocean are a concern, but don’t add much to the overall total released to the ocean by the accident so far. While the continuing releases are notable and need to be stopped, as the data at the beginning of this section suggests, even after several years at the current rates they will probably add less than 1% to what the initial releases dumped. Meanwhile, researchers like Buesseler, Kanda, and Aoyama have done a good job of describing how even the current continuing release levels have kept bottom feeders within a few km of the plant more contaminated than they would be without it, and how they keep even fairly distant seafloor hotspots hot. It’s a real and measurable consequence, but at the same time the continuing releases don’t noticeably affect, for instance, the overall amount and timing of the contamination spread across the Pacific.
Science Magzine: Fishing for Answers off Fukushima (Buessleler, 2012) (paywalled)
Another more recent paper brings together a wide variety of data on concentrations of Cs-137 and Sr-90 in seawater and marine life to illustrate the changes these have undergone since March 2011, and the possible implications:
Nature: Fukushima radionuclides in the NW Pacific, and assessment of doses for Japanese and world population from ingestion of seafood (Povinec, Hirose: 2015)
Again, in terms of effects on the Pacific ocean, the best research suggests that while they’re not fully comparable, nuclear testing and the range of effects seen then is the closest overall precedent to Fukushima scale-wise, though while the testing almost certainly dumped several times more radiation in total than Fukushima did, it was also spread out over decades instead of all at once. Fukushima also resulted in extremely high concentrations near Japan in March-April 2011 that have only a few historical parallels in the contamination from testing, such as from Pacific surface tests.
Because of the way it’s often discussed, this will seem counter to conventional wisdom, but if we go by the data, in terms of direct discharges to the ocean Fukushima is of a similar magnitude to Sellafield, and possibly less severe. Because of this Sellafield will probably provide the most applicable lessons about damage to the ocean environment, with the caveat that the Irish Sea is very different from the Pacific in terms of currents and ecosystem.
We’d also like to point out that the emergence of two very well organized citizen science projects for monitoring ocean radiation, Our Radioactive Ocean and FukushimaINFORM, is some of the best news to come out of the disaster. There are citizens-based projects in Japan for monitoring food contamination and ambient doses in residential areas, but so far we have not seen any similar efforts emerge for forests, watersheds, or other ecological zones. The professional researchers investigating these areas are overextended and overworked, and we would like to encourage them to seek out citizen scientists to share the load, and for citizens to look for such opportunities.
(end of section 2.3)
TO OTHER SECTIONS:
2.1- Issues at Fukushima Daiichi Nuclear Powerplant (FDNPP)
2.3- Environment and Decontamination
