60,000Bq/L… Not Great, Not Terrible

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Wow, this just popped out of the blue. Japan’s environmental minister stated in a press release that Tokyo Electric Power(TEPco) will have to dump Fukushima nuclear powerplant’s radioactive wastewater into the ocean for dilution as it runs out of storage space (one of the many articles). Well doesn’t that sound like the plot to 2014’s Godzilla!

Irradiated sea monsters aside, there are serious controversies and environmental implications of this decision. The Korean government and Japanese fishermen are quite understandably vocal about their concerns with this decision (McCurry, 2019). Meanwhile, Osaka offers to dump radioactive wastewater into Osaka bay as long as it only contains tritium and is environmentally safe (Johnston, 2019).

What’s the big issue with dumping radioactive wastewater? Radionuclides! Specifically, Caesium-134(134Cs), Caesium-137(137Cs), Strontium-90(90Sr), and Tritium(3H), the most prevalent nuclear fallout products at Fukushima now(TEPco, 2019). These radionuclides emit high-energy particles when they decay, which literally tears up DNA upon contact. This causes cells to reproduce into defunct and cancerous cells or even cell death(S. Dingwall, C.E. Mills, N. Phan, K. Taylor, 2011; Starr; Taggart; Evers; Starr, 2019).
Water treatment at Fukushima Daiichi nuclear plant involves treating the water used to cool the damaged fuel rods in Reactors 1, 2, and 3. The main processes are:

  1. Ion-exchange modules (Kurion/Sarry) that exchange strontium and caesium ions for less harmful ones.
  2. Reverse osmosis (RO) that recycles clean water into the reactor core and concentrates remaining brine
  3. Adsorption of remaining caesium, strontium and other (heavy) metals onto various substrates

“Multi-nuclide removal equipment” for process 3. Source: https://www7.tepco.co.jp/wp-content/uploads/hd03-02-03-001-m120625_01-e.pdf

Now you might have noticed that there is a radionuclide I listed earlier that is missing from the treatment process above. That’s right, it’s tritium! Being an isotope of hydrogen, it is incorporated into a H2O molecule as HTO, and passes seamlessly through all of the processes above just like plain old water. Yet, HTO is as dangerous as any radionuclide when tritium decays. What’s worse, TEPco has 800,000m3 of tritiated water sitting around with no feasible isotopic separation method (METI, 2016).

Fortunately, tritium ionizing radiation possesses very little energy and is unable to pass through physical environments or even the layer of dead skin on your epidermis. Contamination is therefore primarily through ingestion or inhalation of tritiated molecules. Dingwall et al. (2011) referred to Brooks et al. (1976) that found that mice could receive 37,000,000 Bq/L of tritiated water without damaging their DNA and causing adverse health effects.

The Tritiated Water Task Force of TEPco estimates a tritiated water concentration of 0.3 to 3.3million Bq/L as of March 2016. They plan to dilute the tritiated water with seawater until concentration levels are 60,000Bq/L before discharge. They also estimate this concentration to drop by 3 orders of magnitude 100km away from the point of discharge (ie.a maximum of 60 Bq/L). To provide perspective, this exceeds most standards of tritium in drinking water.

 

With all the bad press surrounding Japan, we need to recognise that environments close to the source of discharge face potentially unknown effects of concentrated tritiated water (IRSN, 2012); as well as acknowledge what they have accomplished to reduce impacts as much as they have. Less fear-mongering, more research!

References:

^Back to the Top^

Brooks, A. L., Carsten, A. L., Mead, D. K., Retherford, J. C., & Crain, C. R. (1976). The Effect of Continuous Intake of Tritiated Water (HTO) on the Liver Chromosomes of Mice. Radiation Research. https://doi.org/10.2307/3574329

Cecie Starr; Ralph Taggart; Christine Evers; Lisa Starr. (2019). Biology: The Unity and Diversity of Life, 15th Edition. Retrieved from https://www.cengage.com/c/biology-the-unity-and-diversity-of-life-15e-starr/

Dingwall, S., Mills, C. E., Phan, N., Taylor, K., & Boreham, D. R. (2011). Human health and the biological effects of tritium in drinking water: Prudent policy through science – Addressing the ODWAC new recommendation. Dose-Response. https://doi.org/10.2203/dose-response.10-048.Boreham

E. Johnston (2019). Osaka mayor Ichiro Matsui offers to take in tainted Fukushima water and dump it into Osaka Bay. Japan Times. https://www.japantimes.co.jp/news/2019/09/17/national/osaka-mayor-offers-take-tainted-fukushima-water-dump-osaka-bay/#.XYMScCgzZEY

IRSN (2012) Radionuclide sheet: Tritium and the environment. Institut de radioprotection et de sûreté nucléaire. https://www.irsn.fr/EN/Research/publications-documentation/radionuclides-sheets/environment/Pages/Tritium-environment.aspx

J. McCurry (2019). Fukushima: Japan will have to dump radioactive water into Pacific, minister says. The Guardian. https://www.theguardian.com/environment/2019/sep/10/fukushima-japan-will-have-to-dump-radioactive-water-into-pacific-minister-says

METI (2016).Tritiated Water Task Force Report, June 2016. Ministry of Economy, Trade and Industry https://www.meti.go.jp/english/earthquake/nuclear/decommissioning/pdf/20160915_01a.pdf

Appendix:

Radionuclide concentrations around reactor sites(pardon my underlining skills)
Source for Table: https://www4.tepco.co.jp/decommission/data/analysis/pdf_csv/2019/3q/2tb-east_19091301-j.pdf
Source for sampling sites around the reactors: https://www4.tepco.co.jp/en/nu/fukushima-np/f1/smp/form_pdf/2tb-east_form-e.pdf

 

4 thoughts on “60,000Bq/L… Not Great, Not Terrible”

  1. Hi Sam,
    I have 3 questions.
    As I was reading your post and about how water containing radioactive isotopes can be / is being treated at the source…
    1) Are you saying that the earthquake didn’t damage the water treatment facilities ? Or does the radioactive wastewater have to be brought somewhere else for treatment now ?
    2) I understand that absorption through the skin isn’t possible. But if the water is just sitting around like you said, then couldn’t people be exposed through inhalation ?
    3) What is a Bq ? I’ve never seen this unit – can you put it in context, i.e., convert to ppm or ppb or something like that ?
    Thanks,
    jc

  2. Hi Samuel!
    Interesting post! Glad to hear the Japanese government is still making significant efforts to combat the slew of environmental problems that resulted from the Fukushima nuclear disaster.
    When you mentioned fear-mongering, I was instantly reminded of the international community’s fear of consuming products from the Fukushima area, which still exists today (despite the Japanese government claiming it has been scientifically proven to be safe for consumption). Do you think the same stigma exists for this wastewater situation? What then do you think the government can do to change public perceptions?
    – Jiajun

  3. Hi Samuel 🙂

    Thank you for writing this article. I would like to ask…since radioactive water can be cleared into safe drinking water through reverse osmosis, why aren’t the Japanese govt doing that to the contaminated water? Or am I wrong to say that reverse osmosis can clean up the water?

    Really appreciate your knowledge and insights.

    – Cal

    • Hi Cal!
      Yes, heavy radionuclides can be effectively eliminated from the contaminated coolant water through reverese osmosis, ion-exchange membranes, and adsorption onto substrates. However, the difficulty with tritiated water is that it is energy-intensive and expensive to it seperate from regular old water. Afterall, they have the same chemical properties and only differ by 1 atomic mass!
      Reverse osmosis has already been incorporated into the reactor cooling system, and the diluted tritium contaminated water is safe to discharge on paper. However, we do not know what effects the tritium contaminated water might have on the environment, so it never hurts to take precautions!

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