My knowledge about school level physics is admittedly not that fleshed out, but we were told that it is possible to convert mass to energy. My google-fu has sadly left me for my question here 🙁
So why can’t we just take e.g. nuclear waste and convert it to energy? After that so is my understanding it wouldn’t simply exist as matter anymore and wouldn’t require to store dangerous trash if you can convert it all to energy.
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The waste is a result of fission byproducts. When U-235 absorbs an additional neutron, the nucleus becomes unstable. The total mass of the nucleus goes above the binding energy per nucleon, the nucleus can’t contain the mass within it and it essentially explodes. When it explodes, or fissions, it releases energy, some in the form of heat, the rest in electromagnetic radiation. That heat is used in a reactor the add energy to the water raising the temperature of the water. When the nucleus fissions, it also releases 2 or 3 neutrons (avg of 2.43) which go on to either be lost out of the reactor, absorbed into a material designed to capture neutrons (a poison), or they may bounce around against the water molecules like pool balls until their energy is very low. Then, they may become absorbed into another U-235 atom to produce another fission. The rest of the fissile material from the original U-235 atom splits into various elements of varying isotopes such as rubidium, strontium, cesium, krypton, and xenon to name some of the more common elements. Most of these elements are unstable and will further decay into other isotopes and elements. All of these leftover elements from fission (fission byproducts) are what make up the nuclear waste. It is generally highly radioactive and made up of many different materials with varying radioactive energies and activities.
TL;DR
The fission of uranium produces other elements that are radioactive and must be disposed of carefully.
While nuclear reactors (and indeed all fuels) do release energy by decreasing mass (E=mc^(2)) the amount of matter converted into energy is tiny (1 kilo of matter convers to 90,000,000,000,000,000 joules of energy). The nuclear reactor therefore doesn’t cause the fuel rod to disappear, just to convert some of its ^(235)U to other atoms, most of which are radioactive – hence nuclear waste.
Lawn grass can be converted to calories (energy), but you probably don’t eat it. Why not? Your body can’t do the process to convert that type of chemical/plant into energy. You’d have to put it in a fire or feed it to a cow.
Same thing. Not all matter is in a form where we can convert it to energy. It can convert, we just can’t make it based on the process we have at our disposal and the state it’s in.
Nuclear just means that it has to do with the nucleus of an atom(protons and neutrons). The elements we use for nuclear power are heavy and we split them into smaller elements releasing the energy that it took to bind them when they were fused. When they break apart those smaller elements are unstable will decay releasing electromagnetic radiation. This waste can stay radioactive for thousands of years.
Electromagnetic radiation is just different frequencies of light, microwaves, radio waves, the light we see or even the light that keeps us warm. Some of these frequencies of light energy can harm us, like gamma rays, and alter our DNA. So the things used in nuclear power plants can give off these harmful forms of radiation but they aren’t the types of elements we can split to get energy. Fission can also cause a chain reaction of splitting elements in a runaway reaction and cause a meltdown so it is very dangerous.
We are working on nuclear fusion that will put lighter elements together into heavier elements. Since this is a combining reaction rather than a breaking reaction we can use more stable elements that won’t decay. This will be a form of “clean” nuclear energy.
Mass can be converted into energy in principle, but we don’t have any technology that does that yet. Nuclear reactors use the other half of the mass-energy equivalence, which says energy has a tiny bit of mass. Uranium has so much energy in the unstable arrangement of its protons and neutrons that you could weigh the energy on a scale.
Once you take most of the energy out of uranium by rearranging its protons and neutrons, you have more than 99% of its mass left. That’s nuclear waste. It’s still extremely radioactive for the next few decades because of the remaining energy that we can’t extract yet.
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