How-To: Manage nuclear waste
The benefits and risks of nuclear power generation and usage are an ongoing topic of discussion – and often disagreement – with radioactive waste continuing to occupy one of the top spots on the “risk” list.
And while it goes without saying that this form of power has always brought with it a certain amount of concern – previous power plant accidents and the threat of nuclear war are enough to scare any human being – the issue of radioactive waste may stand-out even more to industry leaders than the memory of Hiroshima.
So just how risky is this top-of-mind risk?
According to the World Nuclear Association, it is not as extreme as many believe. As recently as August 2015, the Association stated the following:
• The amount of radioactive wastes is very small relative to wastes produced by fossil fuel electricity generation.
• Used nuclear fuel may be treated as a resource or simply as a waste.
• Nuclear wastes are neither particularly hazardous nor hard to manage relative to other toxic industrial wastes.
• Safe methods for the final disposal of high-level radioactive waste are technically proven; the international consensus is that this should be geological disposal.
As of 2013, it was reported that there were 437 operational nuclear reactors creating electricity, and all of the 437 reactors were located in 31 countries. In 2015 there are 67 civil fission electric reactors under construction. These new facilities are in 15 countries, including some in Gulf States, Asia, and 28 in the Peoples Republic of China. Regardless of how “risky” the risk, we still need solutions.
Options for storage and disposal of nuclear waste
Some of the radioactive waste from nuclear power plants is considered low-level radioactive waste (LLW). Most of the LLW is sent to land-based disposal sites where it is expected to be kept of long-term management. This is how around 90 percent of all nuclear waste is managed around the world.
When intermediate level waste (ILW) and high level waste (HLW) is considered, there have been different management options for this waste investigated. The goal is to find safe and environmental solutions to the storage of this waste that is acceptable to the public. Some countries have just begun to do the research, while other countries, such as Finland and Sweden have advanced with their investigations and in gaining public support for places to keep this waste. In the United States, there is a site below ground in salt formations in the state of New Mexico where waste from defense related sites is currently stored.
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Many countries, such as the Czech Republic, Finland, France, Japan, the United Kingdom and the United States, use near surface disposal. This means the LLW is stored at ground level, or at depths of 10 meters for these countries. Sweden and Finland also store ILW materials for short periods of time at these disposal sites.
The International Atomic Energy Agency (IAEA) recommends that near surface disposal can be used in near-surface facilities at ground level. These facilities can be set up with engineered barriers, or without the engineered barriers. When nuclear waste (LLW) is stored at surface level, there is a protective covering placed over the materials that is a few meters thick. The wasted containers are put in vaults, and after the vaults are filled, and then they are backfilled. Eventually they will be covered and capped with an impermeable membrane. Then the membrane is covered with topsoil. Often these facilities will be built with some sort of drainage system added, and sometimes there are also gas venting systems added.
Near surface disposal facilities can also be built in caverns that are below ground level. When near surface disposal sites are begun at ground level, access is from the surface. When the surface disposal site is in a cavern, access to the nuclear waste site is tens of meters below the surface of the Earth, and the material is accessed through a drift.
Another way to store nuclear waste that is being investigated is deep borehole disposal. This method has been indicated to have a high potential for “robust” isolation of waste, and could present a way to dispose of some wastes that might be able to go into storage faster than current methods, according to the U.S. Department of Energy.
When sites are chosen for these facilities, the long-term expectations for changes in climate must be taken into consideration. The waste associated with LLW and ILW generally has a half-life of about 30 years so stability must be taken into consideration for at least that length of time.
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Another form of radiation comes from uranium mining. While the uranium is being mined, “fine sandy tailings” are left behind. These remains of the mining process have almost all of the radioactive elements that are naturally occurring in uranium ore. Companies make dams that collect the tailings, then they are covered with clay and rock which is intended to stop the leaking of radon gas and made the radioactive materials stabile in the long-term. In the short-term, these materials are often covered with water for a few months, after which it will have about 75 percent of the original radioactivity.
The global approach
French radioactive waste disposal agency Andra is in the process of designing a deep geological nuclear repository in Bure in Eastern France. This site has clay which they believe will be a good way to keep the nuclear waste from leaking and causing other difficulties. They believe this repository will be able to operate at up to 90 degrees C, which they think will be reached about 20 years after the nuclear waste has been stored.
Belgium is considering a similar process for storing spent fuel and HLW. Their investigation into a disposal process involves placing the waste in high integrity steel containers, then in excavated tunnels with the clay, which is self-sealing. This clay is self-sealing and has low permeability so that almost no groundwater can get into the nuclear waste. The Netherlands is considering a similar method.
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The UK uses Nirex Phased Disposal Concept which is intended to store fairly large volumes of ILW and LLW. The nuclear waste is sealed into cemented stainless steel containers. These containers are then stored in a repository that is below the water table. Eventually, the waste will be backfilled with special cement which is intended to prevent waste from reaching the groundwater. Similar forms of storage of nuclear waste are considered in France, Japan, Sweden and Switzerland.
Transporting nuclear waste
The most important safety guarantee in transporting nuclear waste and many other hazardous materials is found the way it is packaged. There have been recommendations by the International Atomic Energy Agency that have been implemented around world as part of the legal provisions for transporting these materials. These standards and recommendations make it relatively safe to transport the waste no matter what method is being used.
There are different levels of packages depending on the danger of the product being shipped. There are different designations, for example Type B or Type C. The larger the letter, the more care needs to be given to the package. When examined, prior to the transportation, things such as radiation shielding, mechanical thermal characteristics and tightness and quality assurances are examined.
It can be difficult to find the cost of transporting and storing nuclear waste, but in 2012-2013, the UK spent about £1.6 billion. In Germany, the reported costs were from USD$50 million to USD$70 million a year, just to transport the nuclear waste.
With the hundreds of nuclear facilities around the world, and dozens more being built, it is apparent that nuclear energy is not going away soon. It is incumbent on countries and citizens to find safe places to store the waste from these facilities.
Drax advances biomass strategy with Pinnacle acquisition
The Group’s enlarged supply chain will have access to 4.9 million tonnes of operational capacity from 2022. Of this total, 2.9 million tonnes are available for Drax’s self-supply requirements in 2022, which will rise to 3.4 million tonnes in 2027.
The £424 million acquisition of the Canadian biomass pellet producer supports Drax' ambition to be carbon negative by 2030, using bioenergy with carbon capture and storage (BECCS) and will make a "significant contribution" in the UK cutting emissions by 78% by 2035 (click here).
This summer Drax will undertake maintenance on its CfD(2) biomass unit, including a high-pressure turbine upgrade to reduce maintenance costs and improve thermal efficiency, contributing to lower generation costs for Drax Power Station.
In March, Drax secured Capacity Market agreements for its hydro and pumped storage assets worth around £10 million for delivery October 2024-September 2025.
The limitations on BECCS are not technology but supply, with every gigatonne of CO2 stored per year requiring approximately 30-40 million hectares of BECCS feedstock, according to the Global CCS Institute. Nonetheless, BECCS should be seen as an essential complement to the required, wide-scale deployment of CCS to meet climate change targets, it concludes.