An shorter article on the same subject was recently published in the Japan Times; this blog post provides more technical detail and sources of information.
Of all the conflicts and consequences of the Fukushima Daiichi NPP disaster, the contaminated water issue is one of the most complicated, contentious, and potentially long-term. It’s a multifaceted problem ultimately rooted in the influx of groundwater into the damaged reactor buildings. A large volume of water is pumped into and out of the damaged reactors each day to keep them cool. This is treated to remove salt and most radionuclides and recirculated back into the reactors. If there were no additional water leaking into the reactor basements, this could function as an essentially closed loop. But a volume equal to the additional groundwater inflow needs to be removed from recirculation. It too is treated to remove all radionuclides except tritium, a radioactive form of hydrogen known as H-3, and is being stored in the now familiar rows of tanks onsite at Daiichi. A partially effective underground dam of frozen earth, together with a system of subdrain pumps, has reduced the volume necessary to be removed from about 400 cubic meters per day to about 150-200 cubic meters (though appreciably more when it rains heavily). About 850 large tanks now hold 850,000 tons of tritiated water, and TEPCO says that it will run out of space to store additional water onsite by 2020, so something must be done soon. As far back as 2014, the IAEA recommended a controlled release of this water to the ocean as the safest course of action, and Japan’s Nuclear Regulation Agency (NRA) has made similar recommendations. A Tritiated Water Task Force convened by METI in 2013 examined five options in detail, including evaporating it and releasing it into the atmosphere, releasing it into the atmosphere as hydrogen gas, injecting it into deep geologic strata, storing it underground, and diluting it and discharging it into the ocean. For reasons of cost, available technology, time required, and safety, in its final report issued in June, 2016, the task force concluded that ocean discharge was the least objectionable approach. TEPCO has made it clear that this is its preference as well, and in July of last year Takashi Kawamura, chairman of Tokyo Electric Power Company Holdings, Inc., said publicly that the decision to release the tritiated water had already been made. Many people were alarmed, particularly Fukushima fishermen who expected to be consulted, and the company backpedalled immediately. So far no decision has been officially announced. The reason for the delay in the decision is the very reasonable expectation of a strong public backlash. Meanwhile the window for the decision to be made is rapidly closing.
METI Tritiated Water Task Force Report, June 2016 (English version)
Preliminary Summary Report: IAEA International Peer Review Mission On Mid-And-Long-Term Roadmap Towards The Decommissioning Of Tepco’s Fukushima Daiichi Nuclear Power Station Units 1-4
(Third Mission), Feb. 2015
The strongest and most meaningful opposition comes from Fukushima’s fisheries cooperatives, which have suffered tremendously due to the disaster. Not only were their ports and fishing fleets destroyed by the tsunami, but the market for their fish collapsed after the sale of 44 marine species was prohibited by the Japanese government in 2011 due to radioactive contamination. The public seems largely unaware that in the years since the bans were initiated, the percentage of Fukushima marine products exceeding the 100 Bq/kg allowable level of radioactive cesium has decreased rapidly, and has actually been zero since 2015. People are right to be skeptical of this, perhaps, but it has been confirmed by official testing, by independent researchers, and by testing done by independent citizen groups. Testing is done for each marine variety on a fishing ground-by-fishing ground basis, and as they have gradually been demonstrated to meet the requirements, 34 of the 44 initially banned seafood varieties have been allowed back on the market. Thanks to incrementally improving consumer confidence, the market for Fukushima seafood has slowly improved. The Fukushima fisheries coops justifiably fear that if the tritiated water is released to the ocean, the resulting consumer backlash will totally destroy their livelihoods once again.
METI has jurisdiction over contaminated water releases from nuclear reactors like Daiichi because it is responsible for overseeing energy production systems as a whole, including accident consequences. The NRA, which is part of the Environment Ministry, has specific jurisdiction for nuclear power, and its evaluations and guidance are also important. But ultimately the decision of whether or not to release the tritiated water is TEPCO’s. A company spokesman explained to me recently that government guidelines and recommendations are taken very seriously, and that the company goes to great lengths to meet government expectations. But ultimately these recommendations are non-binding. TEPCO hopes to get the green light from METI and the NRA, and all of them have been delaying their decisions in the hopes that the approval of the fisheries coops can be obtained as well.
On the face of it, this hope is not totally unfounded, as there is an important precedent. The fisheries coops have been approving the release of water from two specific sources onsite at Daiichi for several years. One is a bypass system uphill of the reactors that intercepts groundwater before it reaches the reactor area. The other is a subdrain system that pumps water from the area around the reactors. In both cases, the water has relatively low levels of radioactive contamination, and is treated to remove radionuclides and then tested by TEPCO and third-parties (JAEA and the Japan Chemical Analysis Center). If the radioactivity is lower than TEPCO’s self-imposed target levels of 1 Bq/L each for Cs137 and Cs134, 5 Bq/L for Gross beta (including strontium), and 1500 Bq/L for tritium — all of which are many times lower than the limits for drinking water set by the WHO — the fisheries coops agree to its release. This agreement has been in place since 2014 for the bypass water, and since 2015 for the subdrain water. It appears to have been functioning smoothly, with over 350,000 tons of bypass water and about 500,000 tons of subdrain water released so far. The participation of third-parties in the monitoring has been the key to gaining trust in the measurements.
TEPCO – Water Discharge Criteria for Groundwater Bypass, February 3, 2014
WE’VE BEEN HERE BEFORE
The tritium in the tanks at Daiichi is much more radioactive than the subdrain or bypass water, however. The concentration levels of tritium in the tanks ranges from about 0.5 to 4 million Bq/L, a total of about 0.76 PBq (trillion Bq) in all. No decision has been made about how much is likely to be released per day, but technical and cost estimates have been based on 400 cubic meters (tons) per day, roughly equal to the maximum daily inflow of groundwater. It is expected that releases would continue for about five years. Under the scenarios being discussed, the water would be diluted to 60,000 Bq/L before being released to the ocean. This number alone seems alarming, but is the concentration level that has been legally allowed to be released from Japanese nuclear power plants and reprocessing facilities such as Tokaimura for decades. The science regarding what is likely to happen to the tritium in terms of dispersal by ocean currents and effects on fish and other biota is fairly well understood, primarily because of decades of monitoring done in Japan and near similar facilities abroad, such as Sellafield in the UK and LaHague in France. Data from the French government shows that the LaHague reprocessing plant releases about 12PBq (12 trillion Bq) per year, and the maximum concentration of tritium in the surrounding ocean has been about 7Bq/L. This means that the amount released yearly from LaHague is over 12 times the total being stored at Daiichi, and the daily release rate is over 20,000 times that expected in Fukushima. Dr. Jota Kanda, a professor at the Department of Ocean Sciences, Tokyo University of Marine Science and Technology, observed that the dispersal and further dilution of tritium is rapid, and says, “Based on what we’ve seen at La Hague, it seems likely that under the ocean release scenario being considered now, tritium concentrations in the ocean off Fukushima will not exceed a few Bq/L and will likely remain close to the background level.” Globally, the background levels of tritium in water currently range between 1 and 4 Bq/L, which includes 0.1 to 0.6 Bq/L that is naturally-occurring and more than doubled by tritium remaining from nuclear testing. In oceans, tritium concentration levels at the surface are around 0.1 to 0.2 Bq/L. For comparison, naturally occurring tritium in rainwater in Japan between 1980-1995 was between 0.5- 1.5 Bq/L, and prior to 2011 in Fukushima rivers and tap water was generally between 0.5-1.5 Bq/L. In the US, the EPA standard for tritium in drinking water is 740 Bq/liter, while the EU imposes a limit of 100Bq/L.
Fujita et al, Environmental Tritium in the Vicinity of Tokai Reprocessing Plant. Journal of Nuclear Science and Technology, 44:11, 1474-1480
Matsuura, et al, Levels of tritium concentration in the environmental samples around JAERI TOKAI. Journal of Radioanalytical and Nuclear Chemistry, Articles, Vol. 197, No. 2 (1995)295-307
METI Task Force Report supplement: About the physical properties of tritium,
Yamanishi Toshihiko, 2013
LaHague tritium release data, cited in METI Task Force Report supplement, p6
Michio Aoyama: Long-term behavior of 137Cs and 3H activities from TEPCO Fukushima NPP1 accident in the coastal region off Fukushima, Japan. Journal of Radioanalytical and Nuclear Chemistry, 2018
Tsumune et al: Distribution of oceanic 137Cs from the Fukushima Dai-ichi Nuclear Power Plant simulated numerically by a regional ocean model. Journal of Environmental Radioactivity 111 (2012) 100-108
Povinec, et al, Cesium, iodine and tritium in NW Pacific waters – a comparison of the Fukushima impact with global fallout. Biogeosciences Discuss., 10, 6377–6416, 2013
Dr. Kanda further explains that biological organisms such as fish have different concentration factors for different radionuclides. When the ambient level of Cs137 in seawater is 1 Bq/L, for instance, some fish species may show values approaching 100 Bq/kg. But for tritium (H3) the ratio is 1:1, and 1 Bq/L in seawater will result in 1Bq/kg in fish. Again, at La Hague, which has had a much higher release of tritium for decades, the concentrations in marine wildlife near the point of release between 1997-2006 has ranged from 4.0 – 19.0 Bq/kg, with a mean of 11.1 Bq/kg. Using this as a guideline, Kanda estimates that even with an ongoing release of 60,000 Bq/L of tritium offshore of Daiichi, the fish a short distance away are unlikely to exceed 1 Bq/kg. This can, and must be, confirmed by conscientious monitoring.
What about health effects to humans? Though the release from Daiichi would be many times smaller than what is ongoing from LaHague or Sellafield, and the levels in the ocean after release seem likely to be close to that in normal rivers and rainwater, it is understandable that people would be concerned about risk. The scientific consensus is that tritium presents a much lower risk than radionuclides such as radioactive cesium, radioactive iodine, or strontium. This is reflected in allowable limits in drinking water which are generally tens or hundreds of times higher for tritium than for these others, ranging from 100 Bq/L in the European Union, 740 Bq/L in the US, 7000 Bq/L in Canada, 30,000 Bq/L in Finland, and 76,103 Bq/L in Australia. The WHO limit for tritium in drinking water is 10,000 Bq/L. Allowable limits in food have in most cases not been established. While these limits reflect a general scientific consensus that tritium presents a very low risk, the wide range of official values suggests scientific uncertainty about how it actually affects the human body.
Because in its most common form, known as HTO, tritiated water behaves almost identically to water, it is eliminated from the human body with a biological half-life of 10 days, the same as for water. But when it is incorporated into living things or organic matter, a fraction of it binds with organic molecules to become organically bound tritium, known as OBT. In this form it can stay in the body for years, and its risks, while assumed to be fairly low, are not fully understood. Dr. Ian Fairlie, a UK-based researcher who has published widely on the risks of tritium exposure, believes that current guidelines underestimate the nuclide’s true risk. Fairlie points out that there is a long-running controversy among experts regarding the risks of OBT, which many believe are higher than official guidelines currently recognize. Many official agencies, like France’s IRSN, have issued reports that recognize these uncertainties, and Fairlie believes that the research findings indicate that the dose from OBT should be increased by a factor of 5 compared to HTO.
The following three references were added June 8, 2018 in response to questions regarding dose uncertainties for tritium:
ASN (Autorité de Sûreté Nucléaire) Tritium White Paper, 2010 (French with English summary starting p.288) This is an encyclopedic report on all aspects of tritium, focusing on effects on the environment and living things.
Fournier and Jaunet, Two years of a pluralistic work: ASN published a white paper on tritium Radioprotection, vol. 46, n◦ 6 (2011) S627–S632 (Separate English language summary of the ASN White Paper)
In the ocean release scenarios being considered in Fukushima, Fairlie agrees that there will be high levels of dilution. Nevertheless, as the tritium disperses, he says, “It will be found throughout the entire ocean food chain.” The ICRP suggests that 3% of the tritium metabolized from water by marine life becomes potentially riskier OBT, while the IAEA estimates the fraction at 50%. IRSN and others caution that the biological exchange of tritium and other aspects of its action in organisms, such as the effects of exposure on embryos and foetuses, is incomplete. The METI Tritiated Water Task Force report of June 2016 explains that, “When standard values pertaining to radioactive material in food were established [in Japan] in 2012, it was concluded that “it is difficult to conceive of the concentration of tritium in food reaching a dose that would require attention.” This must not be assumed to be the case. Any estimate of risks to humans from tritium exposure should take the uncertainties as well as the possibility of higher risk from OBT fully into account. That said, the roughly 1Bq/kg maximum expected by experts to be found in fish off Fukushima after release is roughly from 100 to 70,000 times lower than drinking water limits around the world. Assuming that 3%-50% of that 1 Bq/kg is OBT, with a potentially higher risk factor, the human exposure risks from this scenario nevertheless appear to be extremely low, close to those of normal background radiation. The Japanese Gov’t is arguing that it is negligible.
FUKUSHIMA FISHERIES COOPS
TEPCO, METI, and other government bodies which share the mandate for dealing with contaminated water from Fukushima Daiichi believe there is no scientific reason to prevent releasing the tritiated water into the Pacific. For them, the largest stumbling bock is the lack of approval from the Fukushima fisheries cooperatives. As described above, these coops agreed to other releases of treated water from Daiichi as long as it’s compliance with safety regulations could be independently confirmed. Since the science indicates similarly minimal risk from releasing the water from the tanks after considerable dilution, what is their objection now? “We are totally opposed to the planned release,” explained Mr Takaaki Sawada of the Iwaki Office of the Fukushima Prefectural Federation of Fisheries Cooperative Associations, known as FS Gyoren. “It’s not a question of money or compensation,” he continued, “nor of any level of concentration we might accept as safe. There aren’t any conditions we would set, saying ‘If you satisfy these conditions then we will agree.’ We do not think it should be our responsibility to decide whether or not to release it. That entire discussion is inappropriate.”
Over the course of our long conversation, Sawada frankly acknowledged that the scientific consensus indicates very low risk if the water is released. “It’s not a question of scientific understanding,” he said. “We understand that tritiated water is released from other nuclear power plants in Japan and around the world. But we think it will be impossible for the public in general to understand why tritium is considered low risk, and expect there will be a large new backlash against Fukushima marine products no matter how scientifically it is explained.” I pointed out that the coops agreed to the release of the subdrain and bypass water from Daiichi, and asked what was different about this. He pointed out that in those cases, the water is pumped out before it is contaminated, and the public seems to understand that the contamination levels are already very low.
Fisheries coops, or kumai, are organized at each fishing port, of which there are 14 in Fukushima, only 2 of which, in Soma and Iwaki, are now operating commercially. The Fukushima coops have a total of about 1400 members at present. FS Gyoren is a prefectural federation, or rengo kumiai, that exists to facilitate communication and cooperation among the individual coops. There is a national rengo kumiai as well, called Zengyoren. These are not companies, and are not top-down organizations. Rather, each local port kumiai maintains independence. And though in meetings with Tepco or the government FS Gyoren communicates the concerns of members based on the kumai’s own meetings, no real full consensus has been reached regarding the proposed releases. It is a difficult situation with many possibilities for dissatisfaction and dissent. As an outside observer, I expected that some trust-building conditions, such as more transparent and conscientious monitoring, or further limits to the concentration and quantities released, could be satisfied which would allow the coops to agree to the ocean discharge. But now I think they won’t budge, particularly after TEPCO chairman Kawamura’s surprise announcement last summer that the decision had already been made without their approval. The kumiai will, I think, force the decision to be made against their strong opposition. I think they’re right that Japanese society is primed for a large backlash against Fukushima seafood no matter what the science and measurement shows.