• ladicius
    link
    fedilink
    arrow-up
    15
    ·
    1 day ago

    Would splitting one single atom in a non dense environment start a nuclear chain reaction? And why do I ask such questions when it’s simply a cartoon to snicker about?

    • alpine_jim@piefed.social
      link
      fedilink
      English
      arrow-up
      23
      arrow-down
      1
      ·
      1 day ago

      no, there are lots of atoms splitting inside your body every second.

      a single U-235 atom’s fission, releasing ~200MeV, (~30 picojoules), in ideal circumstances could maybe nudge a very small fine grain of sand (~ micrograms) enough to see movement (small fraction of a millimetre) under a microscope .

      It takes months of refining to make nuclear fuel that’s suitable for sustaining a chain reaction.

      it’s an interesting question, I’m glad I did the research checking that the orders of magnitude match!

      • Photonic
        link
        fedilink
        arrow-up
        3
        arrow-down
        9
        ·
        1 day ago

        There are no atoms splitting inside the body. Nuclear decay happens, but not nuclear fission.

        • alpine_jim@piefed.social
          link
          fedilink
          English
          arrow-up
          12
          arrow-down
          1
          ·
          edit-2
          21 hours ago

          Alpha and beta decay are types of fission.

          further, if you only want to look at fissions with similarly-sized daughter products, there are several micrograms of fissile atoms in each of us, so random fissions are indeed constantly happening.

          • Photonic
            link
            fedilink
            arrow-up
            2
            arrow-down
            6
            ·
            edit-2
            4 hours ago

            I understand your confusion, since particles are ejected from the nucleus in both processes. They’re similar but not the same. Alpha decay may seem to be a bit of a grey zone, since the atom expels a helium nucleus, so the atom is “split” into two very asymmetric parts, but it is generally not considered a fission process. Alpha decay and spontaneous fission are actually competing processes.

            And spontaneous fission is possible, but it’s extremely rare. For your example of Uranium, which, in nature, is overwhelmingly (99.3%) U-238:

            Spontaneous fission is extraordinarily rare on a per-atom basis. Uranium-238, the most common uranium isotope on Earth, has a spontaneous fission half-life of about 8.4 × 10¹⁵ years.

            Source

            So with the uranium in your example there is a non-zero chance of spontaneous fission occurring, but it’s very unlikely, with alpha decay being about 2 million times more likely to occur. So, alpha decay will be the overwhelmingly dominant process, leaving virtually no room for spontaneous fission over the short span of a human lifetime.

            Beta decay is something else entirely where no protons or neutrons leave the core, so there is no fission to speak of.

            EDIT: I see the Lemmy downvote bandwagon has arrived, but:

            booing

    • Photonic
      link
      fedilink
      arrow-up
      2
      ·
      edit-2
      11 hours ago

      A nuclear chain reaction can only be sustained through very specific molecules that have the ability to undergo fission and release neutrons while they do. Those released neutrons then need to interact with new fissile molecules that surround the first one.

      The chain reaction also requires that there are enough of those molecules and that they are packed closely enough together, so the reaction doesn’t fizzle (no pun intended) out.

      That only happens in an environment like enriched uranium, which is uranium with an artificially high percentage of U-235 that doesn’t occur naturally –at least not anymore.

    • AeronMelon
      link
      fedilink
      arrow-up
      4
      ·
      1 day ago

      Was that not Albert Einstein’s fear regarding the bomb? That Earth’s atmosphere would simply ignite when exposed to the initial reaction?

      I think our sitting here, snickering at a comic about a biblical nuclear explosion, is proof that it wouldn’t happen.