What is the safest way to dispose of radioactive waste?

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If nuclear is one of ways to obtain green energy, what are the byproducts of the experience and how do we sustainably rid ourselves of said byproducts safely?

In: Engineering
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That’s an ongoing problem as more waste develops. From the NRC (Nuclear Regulatory Commission)

> There are four categories of byproduct material:
>
> 1. Radioactive material that results from the fissioning, or splitting apart, of enriched uranium or plutonium in nuclear reactors. Examples include cobalt-60, cesium-137 and iridium-192.
>
> 2. Tailings or waste produced by processing uranium or thorium from ore.
>
> 3. Certain processed radium-226 or material that becomes radioactive in a particle accelerator used for a commercial, medical or research activity. Examples include fluorine-18, cobalt-57 and iodine-123.
>
> 4. A naturally occurring radioactive source that is processed to increase its concentration and that the Commission decides could pose a threat to people and the environment similar to that of radium-226.
>

This gives us a few different things that need to happen. The waste from a nuclear reactor might be purified and reused, while waste from mining/the waste from that purification [might need to be buried](https://www.nrc.gov/waste/hlw-disposal/yucca-lic-app/photo-loc.html). It’s certainly a problem, but IMO, it’s overblown how bad it is, at least compared to everything else that we already do.

There are only a small amount of byproducts from nuclear reactors. These small amounts are still dangerously radioactive and fall in one of three categories: low, medium and high level waste, where low level is less than 5, medium level is between 5 and 100 and high level is beyond 100 years. These years indicate when a byproduct is no longer dangerously radioactive.

Short and medium level waste can be stored in containers lined with protective material, which are stored in a warehouse somewhere. Some companies have an “above ground” mound of the stuff, where the entire mound is lined with a protective barrier.

High level waste is not only highly radioactive, but also extremely hot. Therefore, these materials need to be stored in a cold, controlled environment, until it falls within the parameters of low or medium levels, after which it can join it’s brethren in containers or in a mound.

After the stuff has lost radioactivity, it can be disposed of or recycled for further use.

When spent fuel is taken out of the reactor, it’s generating quite a bit of heat, so to keep it from melting it needs to be stored in a pool of water for a few years. But after that it’s cooled down enough that, left to itself, there isn’t much that will happen to it. I mean, it’s a ceramic material.

The medium-term solution is to store in large steel & concrete canisters; that’s good enough for decades. And the volume isn’t that big. If the USA got all its electricity from nuclear, at the density of this storage area,

https://www.connyankee.com/html/about_cy.html

one square mile would suffice for the next 40 years. The US has many square miles of desert.

The long-term solution is some variation of ‘dig a deep hole in the ground, put it in, fill the hole’. We know this will work because it worked in the distant past. Natural reactors ran, immersed in moving ground water *with no containment at all* for the fission products. And the result was … nothing much.

> Most of the non-volatile fission products and actinides have only moved centimeters in the veins during the last 2 billion years.[4] Studies have suggested this as a useful natural analogue for nuclear waste disposal.[9]

https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

Tough issue. First one has to understand half life. Half life is the amount of time half of a sample takes to decay. Say something has a half life of 1 day. After one day half of the material would decay, another day and half of tje half would decay, etc. Two points should stand out. The first is that isotopes with short half lives are more dangerous because they are decaying faster but become less harmful faster. Isotopes like U238 have a half life of 4 billion years. The stuff is radioactive forever but most people are surprised to find that the material is not dangerous because the decay rate is so slow. This means that most radioactive waste has to he handled differently early than it has to be handled later. Early on, the waste is high in materials that have a short half life. These are often stored on site under water(for cooling and containment) for a few years. After this time has passed and the material is considered low level waste it needs to be transferred to storage for a significant amount of time, maybe thousands of years. One of the best ideas in my opinion is ceramic encapsulation. The idea is that you pack the waste in a clay like material that does not allow water to penetrate and throw the stuff back in a nuclear mine.

Just stick in a container and leave it here. I know it seem weird, but that very true. People freak out because some of those byproduct last thousands of years, but that doesn’t make them that dangerous. Isotope either decay fast and strong, or slow and weak. You won’t have an byproduct lasting millions of years while blasting high level radiation.

So if you make a safe container, you can just leave it next to the nuclear reactor where it can be monitored. It won’t last forever, but it’s gonna be safe and since we can moniter it we can know when we gonna need to make another containement. Having it next to the reactor also limit the issues of transporting nuclear waste accross the country to an underground facilities, it’s cheaper and make it possible to recover the waste if we ever want to reprocess it.

We can also make underground permanent storage facilities, but it’s debatable if that really the better option.

What is true is that no matter what way we do it, nuclear waste is only a tiny amount. We reject in the environment way more dangerous waste chemical and nuclear on a day to day basis without a care in the world. The issues with nuclear waste is that it’s concentrated, which make it way easier to deal with, but attract way more attention.

Here some good video on the subject, and a video on reprocessing.

[https://www.youtube.com/watch?v=KnxksKmJa6U](https://www.youtube.com/watch?v=KnxksKmJa6U)

[https://www.youtube.com/watch?v=UA5sxV5b5b4](https://www.youtube.com/watch?v=UA5sxV5b5b4)

Nuclear energy, contrary to popular belief, is remarkably clean, efficient, and safe. Accidents are rare, the only danger lies in disposing of waste. Typically this is done by storing the radioactive materials in deep indoor cooling pools for a while (5-10 years-ish)

After this there isn’t much that can be done. Radioactive isotopes irradiate their surroundings ad Infinitum, and the only real option at the moment is to isolate them. One such option is to stick them at the bottom of an abandoned salt mine and fill it with concrete. It really doesn’t matter where you put it, the goal is to limit contact with dangerous materials.

This means we need to take into account future generations; some isotopes have a half-life (the rate at which a radioisotope activity will reduce by half) of 150,000+ years, which means we would need to warn people about them, far into the future.

Examples of some ideas are on this wiki page: https://en.m.wikipedia.org/wiki/Long-time_nuclear_waste_warning_messages

(They’re really cool ideas, like constructing a giant forest of black concrete spikes, and big stone obelisks in many languages warning of what lies there – here’s a really good video touching on the topic): [19:50-23:10] https://youtu.be/7MOKTU9tCbw

The safest way is one in which nobody ever comes across the damn stuff ever again. We don’t know how foolish future generations will be, perhaps the big obelisks and black spikes, etc will attract even more visitors. I mean, the pyramids did a fat load of good.