Toxic waste removal

Last week I spoke about how nuclear power is actually produced through the process of nuclear fission. Although it is a very interesting process scientifically, there are some major challenges that arise after nuclear energy has been created - nuclear waste. At every stage of the nuclear fuel cycle, nuclear waste is produced, either through the process of uranium mining or through the reprocessing of the fuel that is left over. In fact, according to Greenpeace, the level of spent nuclear fuel is increasing by around 10,000 tonnes annually. Not only that, but unlike our normal household rubbish, this nuclear waste cannot be dumped in a bin but has to be stored carefully due to it's radioactive nature which I will explain later.

According to the United States Nuclear Regulatory Commission (USNRC), there are two types of nuclear waste - high level and low level waste. Low level waste is any item that has been used during the process to create nuclear energy and has been exposed to some form of radiation. That includes everything from mops, medical tubes, equipment and even the clothes that have been worn by staff working in nuclear power plants. High level waste, however, is the spent fuel that has been used during the nuclear fission process. That is where the concern lies. During the process of nuclear fission, transuranic elements are produced. Although these elements do not produce enough heat energy, they take longer to decay and account for a large majority of the radioactive waste that decays over a period of around 1,000 years according to Molecke's 1980 study. Some of the radioactive isotopes in these elements decay within minutes, however some of the elements take quite long to decay - for example Plutonium-239 has a half life of over 24,000. The safe storage of these radioactive elements is a major concern for scientists and governments across the world. Most recently, writing for the American Geophysical Union, Colgan et al. (2016) reported that nuclear waste which has been buried under the Greenland ice during the Cold War period might be released due to rising global warming which is melting the ice layers. The study concluded by saying that this radioactive material might even be released into oceans by the end of the century - yikes! If you think that this is another doomsday scenario by an expert then you are completely WRONG. A radiation leak worth £240m occurred during March 2015 at the Waste Isolation Pilot Plant in New Mexico, US which sent shockwaves through the scientific community. There are many other nuclear waste leak examples, some of which I will mention later in my blog, however let's have a look at some of the ways in which radioactive waste is stored.


How is radioactive waste stored?

One of the main ways in which nuclear waste is stored is through underground repositories where radioactive material is held in canisters or tankers for hundreds of years. An interesting example is the Oilkiuoto repository on the west coast of Finland which is currently being constructed. This 3 billion euro underground facility, as Gibney (2015) reports in 'Nature', will start storing nuclear waste by 2023.

Oilkiuoto underground repository under construction

The main problem, however is public opposition against such large nuclear disposal sites and this poses a key challenge for governments as they try to find new disposal sites. Earlier in 2013, there were plans to build a nuclear disposal facility in West Cumbria near the Lake District however these plans were scrapped because of public opposition. For a minute have a think. Would you want a nuclear disposal site close to your house? Well, I guess the answer would probably be NO. 

Secondly, low-level nuclear waste (which I mentioned earlier) is usually stored overground as it is deemed to be safer in terms of radioactivity. This again presents new problems for engineers, governments and scientists. If radioactive waste is stored overground, there is a heightened risk of corrosion due to air humidity levels (Larsen 2015). Air humidity levels need to be controlled to allow the easy ventilation of air to avoid any corrosion and the cost of keeping these facilities is substantial as this type of low-level waste could stay radioactive for over 25 years. Complex computer generated simulations, as the image below shows, need to be analysed to monitor air ventilation. In a nutshell, nuclear waste poses key challenges for society, both above and below the ground. This can be in financial terms through constant maintenance and even social terms through public opposition and safety risks. 

Simulations showing the circulation of air flow around a nuclear storage facility