Tepco measures Tritium concentration at 290Bq/L in ground water at a location near Fukushima-Daiichi. Nearby, on July 18, it was 1,700Bq/L.Using numbers from this WHO page. You can calculate that for every Becquerel (Bq) of water contaminated with Tritium, you will get 1.8E-8 mSv of exposure for an adult.

— NucNet Nuclear News (@NucNetupdates) July 25, 2013

1.8E-8 mSv/Bq for tritium

Thus, we can calculate for worst case of 1,700 Bq/L. This will give us 1700Bq * 1.8E-8 = 30,3E-6 mSv per liter consumed by 1 adult.

Let assume now that this adult will drink 2 liters of this water at this concentration every week for 1 year. Which is practically impossible, but just for calculating a worst case scenario.

This give us: 30E-6 mSv/L * 2 L/week * 52 weeks/year = 0,00312 mSv/year or 3,12 uSv/year.

Is this a big radiation exposure?

You can compare this to the exposure I measured while taking is trip from Montreal to Toronto

http://radio-activity-studies.blogspot.ca/2013/01/radiation-durant-un-voyage-en-avion.html

Where I was exposed for a less that 1 hour to 350uR/hr or 3.5uSv/hr.

Conclusion is, you will be exposed to more radiation on a typical plane trip than drinking 2 liters per week for 1 years of Fukushima Tritium contaminated water.

Did I made a mistake on my calculation? Let me know.

According to information from NucNet, your calculations are correct. The WHO, based on recommendations by the International Commission on Radiation Protection (ICRP), has set an upper acceptable limit of tritium in drinking water of 7000 Bq per liter.

ReplyDeleteYou also have to take into account the tritium is naturally occurring in water in small quantities (and is even used in dating of water-based liquids like vintage wines). And an intake of tritium with water can have an effect on the body quite different from being exposed to radiation of the same quantity (in uSv) from the outside.

So, your calculations are correct, but the comparison is flawed due to the nature of the exposure that you are talking about. However, you would be interested to know that the EU is currently preparing legislation that could limit the number of hours pilots are allowed to work due to the exposure to radiation that you talk about.

All good comments. I would like to study more how to compare the internal radiation and external. I assume WHO calculation took this into account.

ReplyDeleteHow would you compare? Since this is well under 7000 Bq/L?

ReplyDelete