What are the problems with radioactive waste?

Answer 1

First, let's define what is meant by "nuclear waste", as it is important to categorize what exactly is waste, in the same way that people's "garbage" is now broken down into categories like "recyclables", "compost", "yard waste", etc.

In general, there are three categories of nuclear waste, rated by their radioactivity: "low-level", "medium-level", and "high-level" waste.

Low-level waste consists of normal materials used in the production or handling of nuclear products, and which does not itself emit any radiation. The primary concern here is toxic issues, as many nuclear products are toxic as well as radioactive. Remember that "nuclear" products are not just reactor fuel - we use radioactive materials in a vast variety of things, from medical devices such as X-Ray, CAT, and MRI machines, to alloys of specialty metals (used in a myriad of places), to even things like batteries. Low-level waste (which composes 99% of all "nuclear waste") is a huge variety of items: normal clothing, latex gloves, metal handling tools, tubs where materials were mixed, etc.

As such, the problem with disposing low-level waste is functionally identical to that of disposing standard "toxic" waste. The items in question aren't really radioactive in any meaningful way, but they still are contaminated with material that can cause significant environmental harm. So, they should be disposed of in the same way we'd like to dispose of things such as toxic chemicals (DDT, Ditoxin, Petroleum byproducts, etc.). Currently, there's only really two ways to get rid of these items: bury them in sealed containers away from people (which, frankly, is not a real good solution, since the time it takes for such toxic material to decompose/break down is quite a while), or burn them in special incinerators.

With low-level waste, there is very little risk associated with transporting the waste to a disposal point. Overall, low-level waste is less difficult to dispose of properly than most toxic industrial chemicals, but more difficult than "ordinary" toxic waste such as household cleaners, etc.

Medium-level nuclear waste is generally metals and other compounds which have been exposed to extended amounts of radiation, and thus have become radioactive themselves. Typical of items in this category are equipment used in a nuclear reactor (as they become radioactive after exposure to the nuclear fuel or coolant), or items used to house, transport, or create the nuclear fuel.

These items do pose a radiological threat, though only over a long period of time. As mildly radioactive materials, people exposed to them over months or years would receive radiation that would significantly increase their chances of developing cancers or other radiologically-induced diseases. However, short-term limited exposure is not particularly threatening.

Medium-level waste is generally not notably toxic - the primary threat is long-term exposure to the material. As such, the disposal problem is to isolate the waste until the level of radiation given off drops to a safe level. As most medium-level waste radiates low-intensity radiation, but does it for an extended time (decades at a minimum, often centuries), disposal methods need to consider long-term isolation storage, though radiation shielding does not have to extensive. As most medium-level waste is building materials or equipment, liquid leakage is generally not a problem. Common solutions are to store such items in a sealed mine. Old salt mines are popular, as they have very little water leakage, and the mild radiation is easily absorbed by the thick salt walls.

High-level waste is what most people think of when "nuclear waste" is spoken of. Reactor fuel makes up most of this category, but also a variety of spent isotopes from X-Ray and MRI and other medical uses is also of a concern. In general, this category is made up of materials that are naturally radioactive, whether being an "ordinary" radioactive element, or a byproduct of nuclear decay that are still radioactive.

Unfortunately, most high-level waste is not only extremely radioactive (giving significant amounts of short-term radiation if touched, ingested, or inhaled), but also quite toxic. Indeed, for many high-level waste products, the long-term toxic hazard outweighs their relatively short-lived radiological hazard. Most high-level wastes are easily absorbed into the ecosystem, able to infiltrate the food chain quickly, and can cause catastrophic damage to all parts of the environment.

As literally the most dangerous materials of the modern world (with the possible exception of customized biological weapon materials), they pose a myriad of problems. Their radiological effects require that they be isolated and contained in heavily-shielded places, while their toxic nature requires such places to be resistant to the corrosive effects of the waste and also to be sealed from contact to the local environment. The radiation characteristics of each material differ wildly, so a solution for one waste material may not be suitable for use by other waste materials. Similarly, the chemical and toxic characteristics of each waste material make designing a one-size-fits-all solution practically impossible. For instance, plutonium has a moderate level of radioactivity, very long half-life, very high toxicity, but is rather chemically inert. Cesium and Strontium, however, have high levels of radioactive emissions, a short half-life, low toxicity, but are highly chemically active (i.e. they easily combine with other molecules and thus are easily absorbed into the ecosystem).

Due to these serious problems of toxicity, chemically active nature, and high radiological risk, transportation of these items is difficult to do safely. Disposal consists of extreme isolation and containment in highly-corrosion-resistant containers.

Fortunately, high-level waste is a very small amount. It can be further reduced by efficient recycling and re-processing "spent" reactor fuel, allowing for up to 90% of the "spent" fuel to be re-used, and thus kept out of the waste disposal chain. Estimates for the worldwide annual volume of high-level waste depend on the amount of recycling that happen, but it is relatively small - in the dozens of tons. Thus, while the problem is extremely difficult, fortunately the amount of such materials is tiny.

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To answer the question, each form of waste has different levels of problems associated with it. Broadly, here are the categories of problems:

• Toxic - the material is poisonous or unhealthy if ingested, inhaled, or touched.
• Corrosive - the material causes significant damage to other materials which come in contact with it.
• Radioactive - the material emits radiation which may cause harm to living tissue
• Explosive/Heat Risk - the material may explode under certain circumstances, or is significantly exothermic (i.e. produces heat on its own)
• Chemically Reactive - the material is prone to producing volatile, toxic, or other dangerous compounds when exposed to the normal environment.
• Militarily Valuable - the material has military value; that is, it is an important ingredient in creating some sort of weapon

Each level of nuclear waste (and, even within each level) has a different combination of the above characteristics.

Toxic materials must be either rendered chemically non-toxic, or isolated from exposure to the environment. Transportation of these materials is generally dangerous, as accidents are hard to clean up and the effects of a spill can be widespread.

Corrosive materials must be rendered chemically inert, or stored in special containers resistant to the corrosive effects. Transportation is very dangerous, as they pose a severe hazard to the area around the accident (though less danger to large areas).

Radioactive materials must be stored in shielded containers until the amount of radiation emitted by the material is at a safe level. Transportation is generally safe, as accidents are relatively easy to contain (though expensive).

Explosive and Exothermic materials must either being chemically neutralized, or sealed in a non-reactive container and isolated from any outside contact. Transportation is an extreme hazard, as any accident can result in almost total destruction of the area around the spill (though, no larger-scale damage).

Chemically Reactive materials must be either be chemically destroyed (i.e. turned into a compound which isn't reactive), or stored in special chemically inert, sealed containers. As with explosive/exothermic materials, transportation is extremely hazardous, as any accident can cause widespread destruction.

Militarily Valuable materials must either be guarded from theft, or reformulated into materials that are impractical for making into a weapon. Transportation is expensive due to required police/military protection of the material, but is not otherwise difficult.

It should be noted that while most of the above solutions mention chemically changing the material into a non-problem compound as an option for disposal, in reality, the expense of doing so is usually prohibitive. In many cases, it is not practical to sort the materials enough to allow for custom chemical treatment. In other cases, the cost of the process to do the conversion is extremely high or has severe environmental side-effects. Mostly, however, we simply don't know how to chemically adjust the waste into something safe.

Note that many (most) of the problems associated with the disposal of nuclear waste also apply to the disposal of any of the myriad of industrial chemicals in common use in any industrialized society. Indeed, the actual danger posed by the use of industrial chemicals is considerably larger than that of nuclear waste, due to two factors: (1) industrial chemicals are used/transported/disposed of on a vastly grander scale than any nuclear material (several million times the amount of chemicals are used vs nuclear materials) and (2) industrial chemicals are handled (and disposed of) with far less care than nuclear materials. In addition, in a pound-for-pound comparison, nuclear materials are not much more damaging to the environment than many industrial chemicals, and generally no more difficult to clean up (which is to say that both industrial chemicals and nuclear materials are difficult, expensive, and time-consuming to clean up, but neither is significantly more than the other).

Answer 2

The problem foremost in storing nuclear waste is it's half-life. Spent reactor fuel will emit deadly radiation from 200 to 500 years and weapons grade plutonium has a half-life of over 2,500 years.

Answer 3

It takes years to not be radioactive anymore.

Answer 4

By burying it , it will cause methane gas in the air and add to the greenhouse effect. It can also kill under ground animals and can cause pollution depending on what waste it is.