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Japan's Fukushima nuclear plant prepares to release diluted radioactive water into the sea

www.koreatimes.co.kr /www/world/2023/07/501_354984.html

There go my swimming on Korea's east side plans for this year.

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  • Every day the Earth receives 50 tons of radioactive material from the Sun, so, can we see this in a global perspective : what are the numbers ?
    ( sorry if this is a double : server is lagging because of DDOS attack )

    • I'm very rusty here, so please correct me where I'm wrong.

      Isn't most of the radiation that makes it to the earth's surface from the sun just EM radiation? That acts a lot different than radiation due to nuclear decay. Your use of the unit 'tons' makes me think you're talking about particle radiation, of which the only one that reaches earth's surface in large quantities would be muons, which may as well be ignored because they aren't interacting with anything.

      The water being released by Japan has the following isotopes:

      Isotope Half-Life (years)
      Tritium (3H) 12
      Carbon-14 5,370
      Cobalt-60 5.2
      Strontium-90 28.8

      All four of these isotopes decay via beta decay.

      So, a comparison to the Sun seems weird here.


      Here's an IAEA overview as of February 2023,

      The discharge of the ALPS treated water into the sea will be conducted after i) purification/re-purification to meet regulatory standards set based on international standards with an exception of tritium and ii) to allay the concerns of the consumers, the target concentration of tritium should be the same as the operational target (less than 1,500 Bq/L, that is less than 1/40 of the regulatory standard value for tritium) by sufficient dilution (more than 100 times) by sea water, prior to the discharge into the sea, and iii) The total annual amount of tritium to be discharged will be at a level below the operational target value for tritium discharge of the Fukushima Daiichi NPS before the accident (22 trillion Bq/year).

      So it's diluted well below internationally accepted concentrations. Moreover, the release is even less than when it was operational!

      • That 50 ton per day I recalled from long ago. So I had to make some search, here's what I found :

        1. Ground Level Enhancement
          These effects are usually measured as elevated levels of neutrons and muons. These events can increase the radiation dose of an individual at sea level or while in an aircraft, though not by enough to significantly increase an individual's lifetime risk of cancer. ...and
        2. "solar wind"
          400 km/s x 5 ions/cm3 x 1g/mol x ...(6400km)2 x 3.1416 x 1e15cm3/km3
          ... x 86400s/day x 1/(6.02e23 ions/mol) This is about 37 tons per day, mostly proton and alpha particles.
          ...
          I used the diameter of the earth instead of that of the magnetic field around the Earth, this is simplistic but should give an order of magnitude. I did not find better information and the real value should be found by someone else.
        solar wind details inside :

        Properties and structure
        Velocity and density :
        "Near the Earth's orbit at 1 astronomical unit (AU) the plasma flows at speeds ranging from 250 to 750 km/s (155–404 mi/s) with a density ranging between 3 and 10 particles per cubic centimeter and"...

        • You're right and I completely forgot about those somehow.

          For pespective,

          On average, Americans receive a radiation dose of about 0.62 rem (620 millirem) each year. Half of this dose comes from natural background radiation. Most of this background exposure comes from radon in the air, with smaller amounts from cosmic rays and the Earth itself.

          So, cosmic rays contribute hardly (about 4%) any to the radiation we receive every day.

          I'm no expert here, clearly, so I'm not sure how to compare these units of radiation with the ones being provided for the Fukushima water release; those numbers are provided in becquerel from the sources I found.

    • The released water has around 1500 Bq/kg. If you were to drink a cup of that water (not even diluted further), you’d get a dose of 0.375 mSv. That’s like 100 flight hours, or an x-ray (depends). Two months of just sitting at home will get you that dose.

    • That's a weird comparison, isn't the concentration in one place which makes radioactive materials dangerous? (Not saying that the water has enough radioactive material, just saying that comparing it to the sun and the whole world doesn't make sense).

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