The release of Fukushima wastewater, and why it's a nothing burger

After a decade since the accident, Japan recently (on 24th of August 2023) started to release treated waste water from Fukushima into the ocean. Predictably, as anything that mentions the word ‘radiation’, this has been extensively covered by all major media outlets. What every journalist should’ve made clear to the public is the following:

This will have no impact on human health or the environment.

The Fukushima Daiichi Incident

On 11th of March 2011, the Tōhoku earthquake shook the Island of Japan. It was an undersea mega-thrust with a seismic magnitude of 9.0 to 9.1. The 4th most powerful earthquake on record and the #1 most powerful on record in Japan. The earthquake together with the subsequent monster tsunami led to over 19000 deaths, 6000 injuries, and 2500 people missing according to reports. However, very quickly, all eyes had turned onto one particular nuclear power plant.

The Fukushima Daiichi power plant had 3 of the 6 reactors being active at the time. These initiated automatic scram (emergency shutdown) after the seismic sensors were triggered; but no damage was done to the plant directly by the earthquake. However, even after fission been terminated, the reactor will still produce significant amounts of heat from the radioactive decay of fission products. For this reason, the core must be actively cooled for some time until the core has reached ‘cold shutdown’. If heat isn’t dissipated, the fuel will become hotter and hotter.

The power plant had several back-up diesel generators ready to power the cooling system in case of off-site power loss (which also happened). Nevertheless, these generators were all wiped out when the tsunami swept over the walls and flooded the basements where the generators were held. A station blackout had occurred about 1 hour after the earthquake when the tsunami hit the plant. Even so, the very motors and pumps of the cooling system were situated at a lower elevation than the reactor building. These were also destroyed by the tsunami. Even if power was still available, the cooling system would’ve still been compromised. Furthermore, the roads were damaged, making quick fixes to the cooling systems difficult.


After the cooling system failed, the cores in 3 units began heating up in the following three days. Water started to evaporate, exposing the fuel, which began to meltdown. The molten fuel (called corium) burned through the pressure vessel and reach the concrete bottom of the primary containment vessel. The extent of the meltdown is different for each of the 3 units. Heating escalated faster in unit 1 compared to units 2 and 3. The problems didn’t end here. The pressure continued to increase. Furthermore, when the fuel-cladding (made of zirconium) becomes very hot, it will react with water producing hydrogen gas. To release the pressue and avoid a hydrogen explosion from happening inside the core, the gas (along with some volatile fission products) was vented outside the primary containment and into the building. Hydrogen explosions later occurred in these buildings, blowing off the roofs. To cool the cores, water was injected into the reactor vessels. This water is the source of the wastewater that is now being released into the ocean.

PLEASE NOTE: I tried to briefly summarize the timeline of the Fukushima accident, in exchange of glossing over many major details. See here, here, and here for further info.

The Aftermath was the disaster

The impacts of this accident couldn’t be overstated. Although, I would argue that the nature of these impacts is different from what many people think. For one, the consequences of the earthquake & tsunami has been confused with the consequences of the nuclear disaster. There was widespread confusion about a particular map, many believing it showed radioactive water leaking into the Pacific. The map actually depicted the height of the tsunami wave. Snopes had to set the record straight on this.

Another reason is that people are easily scared of anything that is associated with ‘radiation’, leading to highly skewed risk perceptions, which isn’t limited to nuclear power. It also makes people afraid of cell phones, WiFi, and power lines. This fear of radiation has been exploited by anti-nuclear movements. That’s not just me asserting this based on my biased pro-nuclear stance. It’s explicitly part of their documented strategy. The document in question was produced during a meeting called Conference for a Nuclear Free 1990s – No More Chernobyls held by NIRS, SECC and Greenpeace. I cannot quote all of it, but it’s interesting to go through the whole document. But quoting one of the major talking points included under “Antinuclear Strategies for the 1990s”:

Develop a strategy now to take advantage of the next severe nuclear accident to kill nuclear power

Is anyone really surprised about this? Not me at least. To an extend, this strategy was successful. In the wake of Fukushima, many nuclear plants were closed in 2011 and thereafter.

30% of Japan’s electricity prior to Fukushima was nuclear, but these were all shut down right after the disaster. Only 11 of 33 operable reactors were reactivated and are currently operating. On the other side of the world, this event had major influences on politics in Germany. The proposal of a nuclear phaseout has been pushed around in Germany for a long time. The announcement of completing the nuclear phaseout deadline by 2022 was first announced in 2000 by the German cabinet led by Gerhard Schröder. This didn’t become official policy right away. Schröder’s successor, Angela Merkel, decided to extend the use of nuclear beyond the 2022 deadline in 2010. However, when 2011 and Fukushima rolled around, anything but a quick nuclear phaseout had become politically untenable in Germany. Merkel changed her position in response to the public outcry, the 2022 deadline became official policy, and Germany started shutting down nuclear power plants in rapid succession. Germany shut down 8 of 17 operating reactors in 2011. Were such decisions justified? In my opinion… no. Not even remotely.

What were the health impacts of Fukushima?

Hydrogen explosions and radiation burns led to 16 non-fatal injuries. But the release of radiation is obviously the main point of concern. How many have died from radiation exposure due to Fukushima? The first (and only one to my knowledge) that has been officially announced was in 2018. A worker who was diagnosed with lung cancer in 2016. The Ministry of Health, Labor and Welfare granted compensation to his family. Exactly when the worker died has not been made public to uphold privacy. The worker was a man in his 50s, had been working for over 28 years at nuclear stations since 1980. He was in charge of monitoring radiation levels at the Fukushima plant, while wearing full protective suit and a full face-mask. During the year of 2011, he was exposed to 34 millisieverts (mSv). From 2011 to 2015, his overal radiation exposure was 74 mSv. His cumulative radiation dose from 1980 to 2015 was 195 mSv.

Just to briefly elucidate this unit of measurement (Sieverts). It represent radiation exposure in terms ‘equivalent dose’ regarding the effects on health. There are different types of radiation (alpha, beta, gamma, etc). These don’t have same health effects per unit of particle absorbed by the body. The unit of Sievert accounts for the difference, such that a full body dose of 1 Sv of gamma radiation is comparable to 1 Sv of alpha radiation. Aside from this, health effects is also determined by how much of, and what parts of the body, are exposed. A particular level exposure within a very short time interval is also different from the same level of exposure spread out across a long time interval.

Some examples to get a feeling of what sievert or millisievert represents:

  • 0.0005 mSv eating one brazil nut (5 grams).
  • 0.01 mSv eating 100 grams of brazil nuts (potassium-40 and radium)
  • 0.08 mSv transatlantic flight (cosmic radiation)
  • 0.18 mSv annual exposure for nuclear power station worker on average
  • 1.70 mSv annual exposure for occupational flight attendance on average
  • 2.40 mSv annual natural background radiation (world wide average)
  • 3.10 mSv annual natural background radiation (USA average)
  • 6.00 mSv annual natural background radiation (areas with some of the highest levels of natural background radiation, e.g. Ramsar, Iran. Please note: such high levels of natural background radiation doesn’t correlate with higher cancer rates).
  • 8.00 mSv annual natural background radiation (Finland average)
  • 8.00 mSv annual background radiation next to Chernobyl confinement structure
  • 10-30 mSv full body CT scan
  • 80 mSv spending 6 months in the international space station
  • 100 mSv the lowest annual dose at which an increased rate (0.55% on top of the baseline) is statistically observed at the population level.
  • 400 mSv when received in a short time interval, some symptoms of radiation sickness may be apparent but it highly varies.
  • 800 mSv annual background radiation at the beach near Guarapari, Brazil
  • 1000 mSv maximum cumulative exposure allowed for a NASA astronaut during their entire career.
  • 2000 mSv when received in a short time interval, exposure will cause severe radiation sickness.
  • 4000-5000 mSv when received within a short time interval, exposure will kill ~50% of people (usually within 30 days), but mortality rates vary greatly depending on medical treatment received.
  • 8000 mSv when received within a short time interval, exposure is 100% fatal, even with medical treatment.

So was the lung cancer of this worker related to Fukushima? The dose received in the years following Fukushima was 74 mSv. That is below the 100 mSv annual dose where effects on cancer rates become clear. Now either (1) lower levels of radiation are tolerated such that there is no significant health effect, or (2) there are still effects but these become too small to be detectable and distinguishable from other factors and statistical noise. The conservative approach has been called the linear-no-threshold (LNT) model that extents the linear relationship between radiation exposure and risk of cancer all the way to zero. Some have argued against this, claiming there is a threshold at or below 100 mSv. There are also a fringe few who argue that low radiation levels are actually beneficial (hormesis). That’s a huge debate in and of itself, which I am not going to dive into. Still, based on the LNT model [0.55% additional risk of dying from cancer per 100 mSv], being exposed to 74 mSv would cause an additional risk of dying from cancer of ~0.4% and the total exposure of 195 mSv would be ~1.1%. Remember, this is in addition to the baseline. The overall rate is much higher (with the baseline), and it could be much higher depending on a multitude of unknown factors. Again, the real effects of low levels of radiation is so difficult to parse out. Especially on an individual level like this case. So there is no way to establish causality.

So why did the ministry grant compensation? Under the established guidelines, a cancer-related death of a nuclear station worker will be recognized as work-related if the cancer has developed ≥5 years after being exposed to a cumulative dose of ≥100 mSv (source). So the ministry doesn’t have to establish cause to grant compensation.

What about the larger public? Did radiation have any impact on public health? The radiation exposures to the public were much lower than what the workers received at the plant. The impacts on cancer rates would’ve been even lower to the point of being insignificant and undetectable, even if we monitored every individual carefully over their entire life. This is the conclusion reached by UNSCEAR. Quoting from UNSCEAR 2020 Report on Radiological Consequences from the Fukushima Accident 10 years later and the FAQs and Answers page on their 2020/2021 Fukushima report.

Since the UNSCEAR 2013 Report, no adverse health effects among Fukushima residents have been documented that could be directly attributed to radiation exposure from the accident, nor are expected to be detectable in the future.

Exposure to radiation could lead to an increased incidence of disease in the exposed population. However, for example, with cancer, it is not generally possible to distinguish by observation or testing whether or not the disease of a specific patient has been caused by the radiation exposure. The Committee has therefore assessed the risks resulting from radiation exposure following the accident by estimating whether any increased incidence of a particular disease, calculated theoretically from the estimated doses, would be detectable compared to the normal statistical variability in the baseline incidence of the disease in that population. The Committee’s conclusion is that its revised estimates of dose are such that future radiation-associated health effects are unlikely to be detectable.

Link to the full UNSCEAR 2020/2021 Report Volume II.

PLEASE NOTE: I should make it clear that this should NOT absolve TEPCO of their responsibility of the incident. Fukushima was entirely avoidable if they followed the safety recommendation that were neglected, as illustrated by the sister nuclear plant. I have mentioned the full name of the power plant here; Fukushima Daiichi. ‘Dai-ichi’ stands for ‘number-1’. The sister plant located nearby, Fukushima Daini (‘Dai-ni’ for number-2), incorporated design changes, such as diesel generators being located inside the waterproof reactor building. While Daini was also struck by the tsunami, it was fine and reaching cold shut down within 2 days. Hence why (being hyperbolic) nobody knows that there even is a Fukushima Daini.

However, the lack of significant health impact due to radiation doesn’t mean there were NO impacts on public health. There indeed were deaths related to the Fukushima disaster. Over 2000 deaths in fact. Not from radiation, but from the disorganized evacuation, interrupted medical care, and suicide. The vast majority of the deaths were among the elderly who were piled into buses, without access to food, water, and medical care.

“If you compare nursing homes that evacuated with those that didn’t, the death rate was three times higher among those who moved,” says Sae Ochi, a doctor at the Japan agency for medical research and development who has worked in Fukushima.

To make matters worse, the evacuation was completely unnecessary according to this study conducted by Phillip J. Thomas, professor of risk management at the University of Bristol, and colleagues. Quoting from professor Thomas:

With hindsight, we can say the evacuation was a mistake. We would have recommended that nobody be evacuated. The sort of dose for even the worst-affected villages was something that was accepted in the nuclear industry 30 years ago.

This is one example of how the consequences of our responses to nuclear accidents are often more severe than the consequences of the accidents themselves. For more on this, read this paper. Another impact on public health due to our reaction to Fukushima was the result of the aforementioned closures of nuclear power plants. When they were shut down, what took their place? The gap was mostly filled by dirty fossil fuels, which are deadlier by orders of magnitude than any nuclear accident, even when fossil fuels are working “perfectly fine” as intended.

Japan’s energy mix changes over decades:

The nuclear shutdown was also a bad idea in Germany. A common argument in defense of the nuclear phaseout involves pointing out that Germany installed renewables that filled in for nuclear. That’s true, but it overlooks a major point that shouldn’t be ignored. The point being: Germany could’ve made more progress, over twice as much, with phasing out deadly fossil fuels (coal in particular) just by keeping the existing nuclear power plants online. In other words, the renewables that filled in for nuclear plants could have been used more effectively by replacing deadly coal or gas plants instead. Hence, the pollution and the associated mortality from those coal and gas plants were avoidable.

What’s the difference in terms of deaths? The increased and/or avoidable air pollution from this resulted in an estimated 21,000 deaths from 2011 to 2017. According to a paper published in 2019, if Germany kept the nuclear plants that were still operational just prior to Fukushima, they could’ve prevented up to 4,600 deaths between 2011 and 2017. If they kept the nuclear plants that were still operational in 2017, an additional 16,000 deaths could’ve been avoided between 2017 and 2035. If Western Eruope and the USA would follow Germany’s example, this would lead to 200,000 preventable deaths by 2035.

Germany recently shut down their last nuclear plants in March 2023. The original 2022 deadline was delayed due to the energy crisis, which… I mean… the very fact that they were forced to keep the last nuclear plants online through the winter during the energy crisis… this alone should’ve made it abundantly clear that keeping the nuclear plants is the smarter decision. Let’s just hope the rest of the Europe and USA doesn’t follow Germany’s example.

The waste water is a nothing burger

Apologies for going on a tangent. My original intent was writing this section in particular, but I got side tracked. So, concerning the water. This water is the aforementioned water that was injected to cool the reactors. This water became contaminated with some radionuclides from the reactor, eventually topping over and began to leak into the ocean. The workers at the plant inhibited this lea by freezing the soil. The water is treated to filter out the dangerous radioactive isotopes.

This is the treated wastewater It has been piling up in tanks on site totaling over 1.3 million tonnes of water, and they are running out of space, hence why they are now slowly releasing it into the ocean. The big fuss is about one particular isotope that can’t be feasibly be removed from it. Tritium; an isotope of hydrogen. Most hydrogen atoms on earth are of an isotope that possess only one proton and no neutrons. This isotope is called ‘protium’. Another hydrogen isotope possess one neutron and one proteon, which is called deuterium, or ‘heavy water’ if deuterium is part of a water molecule. The isotope Tritium has 1 proton and 2 neutrons. Tritium is produced by nuclear power plants when hydrogen atoms absorbs the neutrons. These isotopes are chemically identical. A water molecule with tritium is basically the same as any other water molecule, with the only difference being the mass due to the extra neutrons. This is why tritium cannot be removed by the filtration process.

Is tritium a problem? Not really. Tritium is a radioactive isotope, but a relatively benign one. It’s a weak beta emitter such that you would need to drink a large quantity to get a significant dose, and since it’s chemically the same as water, it doesn’t bioaccumulate.

Another radiation unit to explain briefly: becquerel (Bq). An object producing 1 Bq of radiation means there is 1 radioactive decay event occurs inside this object every second. That’s a very small unit. So, bear in mind that the numbers of Bq can get insane, yet still be insignificant. Converting this into the aforementioned unit of Sievert [0.000000018 mSv per Bq of tritium], you would need to drink over 5 billion Bq or GigaBq (GBq) to get the 100 mSv dose with a 0.55% increased cancer risk. You would need to drink 200 GBq to get a 50% chance of receiving a lethal dose. The WHO has set the safety limit of tritium in drinking water at 10,000 Bq per liter. If you only drank water (2 liters per day) containing 10,000 Bq per liter, you would be exposed to ~0.00036 mSv daily. That is less than the radiation dose from one brazil nut (0.0005 mSv). The annual dose would be 0.1314 mSv, which is less than two transatlantic flights (0.08 mSv).

So, how much tritium does the treated water at Fukushima contain? 780 terabequerels (TBq) or 780 trillion Bq. Definitly enough for a lethal dose, but that’s the total amount contained in over 1,345,000 m^3 or 1.345 billion liters of water. Furthermore, they are going to dilute it down to 190 bq per liter before the water is released into the ocean. That’s far below the WHO safety limit. You would need to drink 60 liters of this water to be exposed to the same level of radiation as you get from consuming one brazil nut.

Nevertheless, if you drank 60 liters of the discharge right at the coast of Fukushima, it will indeed kill you… by water poisoning if the salt doesn’t kill you first.

Okay, but what about the impact on the pacific ocean. Even if they dilute it down and slowly release the water into the ocean, they still plan to add 22 TBq of tritium per year into the ocean? What about that? It’s a literal drop in the ocean. Tritium is naturally produced by cosmic rays interacting with the atmosphere. About 150,000 TBq of tritium is literally raining down globally per year, and 220 TBq of tritium falls down in rainwater per year on Japan alone. The pacific ocean itself already contains around 3,000,000 TBq of tritium. In contrast, the tanks at Fukushima contain 780 TBq of tritium, and they plan to release 22 TBq per year in a highly diluted form, which passes even the highly cautious safety limits for drinking water. This is why the IAEA has approved this decision.

Side Note: China has recently been up in arms about Japan releasing this water. This is rather hypocritical since their nuclear reactors, like any other standard reactor, releases tritium into the ocean as well. Far more than what Fukushima will release. Still, even these releases of tritium pale in comparison to the total amount of tritium (and other radionuclides) already present in the environment.


I have been using unfamiliar units like mSv and Bq so far, but I could make this more intuitive by putting it in terms of grams (357 TBq per gram of tritium). The pacific ocean contains 8,400 grams (8.4 kilograms) of pure tritium. The treated water at Fukushima contains 2.2 grams in total, and only 0.06 grams is released every year. The total radioactivity of ocean water would not change significantly in terms of tritium, and that’s not even mentioning all the other naturally occurring radionuclides present in the ocean.



Great post. The irrational fears of anything nuclear is a continued source of sadness.


This topic was automatically closed 7 days after the last reply. New replies are no longer allowed.