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Cake day: August 8th, 2023

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  • what neutrons? we’re talking about shielding of spacecraft moving out of earth’s magnetosphere, not a spacecraft travelling through core of active nuclear reactor

    the kind of radiation that is relevant are high energy protons (and alphas and electrons, with a sprinkle of heavier nuclei) from sun, mostly. there’s no relevant source of neutrons

    (and incidentally water is pretty good at absorbing neutrons too)


  • skillissuer@discuss.tchncs.detoTechnology@lemmy.worldHow can we get to Mars faster
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    13 days ago

    water does not expand upon irradiation, what the fuck are you talking about. you can’t reflect high energy protons (what would be important in radiation in interplanetary travel) you can only either absorb them or let them pass, there’s no third option, same for anything above uv and electrons

    to a first approximation (rather good one at that) (for gammas) absorption is proportional to how much mass per area unit is used as a barrier. 1 g/cm^2 of water is just as good barrier as 1 g/cm^2 of lead or steel. this means that you can absolutely use completely normal, regular potable water as a radiation shield

    Water in its purest form would have to take on mass to “absorb” radiation, expanding a hull and destroying it over time.

    i’m not even sure what it’s supposed to mean, unless your understanding of ionizing radiation is uncut nonsense

    chemically speaking, it’s completely fine to irradiate water because whatever is formed as a result of radiolysis would just most of the time form water back, with the rest becoming very weak solution of hydrogen peroxide. this is big part of the reason why water is used as a coolant in nuclear reactors

    there are also specific nuances to stopping anything that is not gammas, like secondary x-rays, gammas from neutron absorption etc and this actually favours light element shields, like water or liquid hydrogen, for this kind of radiation shielding










  • because these end up generating most of electricity. older plants matter less specifically because these are less efficient - operating them means more fuel costs per MWh. normally, you can see new flashy plants generating all the time it’s practical, because these are more efficient, have less maintenance downtime etc and when demand grows, progressively less efficient units start generating coming from spinning reserve. the two exceptions are NPPs which are best operated at constant high power because of their neutron physics and renewables that are literal free energy so everything they do is taken in. the only place where you can improve efficiency of NPPs is in turbine, and that probably is pretty well optimized unless turbine is very old, because increasing steam temperature would mean changed conditions in reactor in way that could happen to be out of spec. we have figured out wind power pretty well, and perovskites aren’t a thing, and won’t be a thing until they become more durable, which they won’t. in all cases, upgrades would have to make sense both economically and/or in emission costs. this includes CHP and laying municipal heating grids, and good luck with that with how dysfunctional american local govts are (where probably biggest emission gains from CHP could be made)

    you can redo this for other types of thermal powerplants and come to the same conclusion. if you say that saltman&co and his assemblage of lying machines can outsmart thousands of turbine engineers, you might be a shill for making other people believe that or a moron for believing that yourself