4 ms·

Since the factoid comes from nuclear engineers using the banana for scale, I do wonder a bit how it actually scales up. Is a banana more radioactive than low-le

by belorn 5y ago

Since the factoid comes from nuclear engineers using the banana for scale, I do wonder a bit how it actually scales up. Is a banana more radioactive than low-level nuclear waste?

dmurray 5y ago
No, quite a few orders of magnitude less. A banana is about 0.1 Becquerels/gram [0]. Low-level nuclear waste starts around 100 Bq/g [1]. Below that is another category called very-low-level nuclear waste. Disposing of the latter "does not pose any major problems" - you can put it in landfills, or grind it up and build roads with it - but it is still not recommended that you eat it in large quantities. [0] https://en.wikipedia.org/wiki/Banana_equivalent_dose https://en.wikipedia.org/wiki/Banana_equivalent_dose [1] https://www.radioactivity.eu.com/site/pages/VLLW_Waste.htm https://www.radioactivity.eu.com/site/pages/VLLW_Waste.htm
- belorn 5y ago
  I suspect that the nuclear waste at Fukushima that they intend to release into the ocean is of that category very-low-level nuclear waste. 2.1gram of tritium diluted in 860,000 tons of water. Not sure how many Becquerels/gram that is, but I would be interested to know if its actually higher than the 0.1 of the banana. Is there a minimum level for what can be called very-low-level nuclear waste? (As a minor side note, someone should update wikipedia since VLLW does not seem to exist there as a category and waste with less than 100 kBq/kg is explicitly defined as LLW).
  - dmurray 5y ago
    Surprisingly, it's a lot more radioactive than the bananas. Pure tritium is 3.57×10^14 Bq/g [0] It's being diluted at a ratio of 4x10^11 : 1 so the diluted mixture still has 1000 Bq/g, or four orders of magnitude stronger than the equivalent mass in bananas. Of course, it gets diluted more after you release it into the ocean, but it would take a lot of mixing to get the water down only to banana levels. [0] https://en.wikipedia.org/wiki/Tritium https://en.wikipedia.org/wiki/Tritium
    - belorn 5y ago
      Very interesting. Looking at those numbers, potassium-40 has 32 bg/g. Does that mean that atoms of tritium gives out 10^13 more energy every second compared to potassium-40? It would be funny to see how long a city could survive on just then 1 gram of tritium, and it does give a bit more context to the idea of running a city on potassium-40.
      - dmurray 5y ago
        Potassium atoms are bigger, so I think it's only 10^12 if you want to compare per-atom, but yes.
sushibowl 5y ago
See this chart from the same author: https://xkcd.com/radiation/ https://xkcd.com/radiation/ According to wikipedia, low-level nuclear waste "can range from just above background levels found in nature to very highly radioactive in certain cases such as parts from inside the reactor vessel in a nuclear power plant." From above chart, eating a banana is equal to about 2% of the radiation received from normal background levels in a single day. So I would say, a banana is at least 1-2 orders of magnitude less radioactive than low-level nuclear waste.

by belorn 5y ago

Since the factoid comes from nuclear engineers using the banana for scale, I do wonder a bit how it actually scales up. Is a banana more radioactive than low-level nuclear waste?

dmurray 5y ago

No, quite a few orders of magnitude less. A banana is about 0.1 Becquerels/gram [0]. Low-level nuclear waste starts around 100 Bq/g [1]. Below that is another category called very-low-level nuclear waste. Disposing of the latter "does not pose any major problems" - you can put it in landfills, or grind it up and build roads with it - but it is still not recommended that you eat it in large quantities. [0] https://en.wikipedia.org/wiki/Banana_equivalent_dose https://en.wikipedia.org/wiki/Banana_equivalent_dose [1] https://www.radioactivity.eu.com/site/pages/VLLW_Waste.htm https://www.radioactivity.eu.com/site/pages/VLLW_Waste.htm

belorn 5y ago
I suspect that the nuclear waste at Fukushima that they intend to release into the ocean is of that category very-low-level nuclear waste. 2.1gram of tritium diluted in 860,000 tons of water. Not sure how many Becquerels/gram that is, but I would be interested to know if its actually higher than the 0.1 of the banana. Is there a minimum level for what can be called very-low-level nuclear waste? (As a minor side note, someone should update wikipedia since VLLW does not seem to exist there as a category and waste with less than 100 kBq/kg is explicitly defined as LLW).
- dmurray 5y ago
  Surprisingly, it's a lot more radioactive than the bananas. Pure tritium is 3.57×10^14 Bq/g [0] It's being diluted at a ratio of 4x10^11 : 1 so the diluted mixture still has 1000 Bq/g, or four orders of magnitude stronger than the equivalent mass in bananas. Of course, it gets diluted more after you release it into the ocean, but it would take a lot of mixing to get the water down only to banana levels. [0] https://en.wikipedia.org/wiki/Tritium https://en.wikipedia.org/wiki/Tritium
  - belorn 5y ago
    Very interesting. Looking at those numbers, potassium-40 has 32 bg/g. Does that mean that atoms of tritium gives out 10^13 more energy every second compared to potassium-40? It would be funny to see how long a city could survive on just then 1 gram of tritium, and it does give a bit more context to the idea of running a city on potassium-40.
    - dmurray 5y ago
      Potassium atoms are bigger, so I think it's only 10^12 if you want to compare per-atom, but yes.

sushibowl 5y ago

See this chart from the same author: https://xkcd.com/radiation/ https://xkcd.com/radiation/ According to wikipedia, low-level nuclear waste "can range from just above background levels found in nature to very highly radioactive in certain cases such as parts from inside the reactor vessel in a nuclear power plant." From above chart, eating a banana is equal to about 2% of the radiation received from normal background levels in a single day. So I would say, a banana is at least 1-2 orders of magnitude less radioactive than low-level nuclear waste.