Wherever we live and whatever our lifestyle, we are exposed to radiation. Most radioactive material is natural and has been present throughout history.
The term 'radiation' covers a wide spectrum incorporating radio waves, microwaves, infrared radiation, visible light, ultraviolet light, X-rays and gamma radiation. The last two are known as ionising radiations because they have enough energy to affect atoms. Some materials also emit radiation in the form of alpha particles and beta particles.
In a vacuum, X-rays and gamma rays travel at the speed of light. At high intensity they need considerable amounts of shielding, e.g. concrete or lead, to stop them. Alpha particles travel only a few centimetres in air and are stopped completely by a sheet of paper. Beta particles can travel a few metres in air, but are stopped by a 1 cm thick Perspex sheet.
X-rays, gamma rays and alpha and beta particles are released by radioactive elements. X-rays can also be produced electrically. X-rays were discovered by Wilhelm Röntgen in 1895 and by 1896 an X-ray department had been set up at the Glasgow Royal Infirmary.
Marie and Pierre Curie extracted the radioactive elements polonium and radium from the mineral pitchblende in 1898. Both elements had been previously unknown.
Natural radioactive minerals persist in the environment since the formation of the planet. These minerals emit gamma radiation. Building materials deriving from quarried rock, including concrete and plaster, also contribute to this natural gamma radiation.
Radon is a natural radioactive gas and is the greatest source of exposure to ionising radiation for most people, representing about half their average annual dose. It is formed by the decay of the radioactive element radium which is found in minerals in soils, rocks and building materials. Outside, radon gas disperses into the atmosphere. It can accumulate in poorly ventilated areas, for example in building basements. Radon atoms decay to give other radioactive atoms; if radon is inhaled these atoms can stick to and irradiate the lung tissue. Read the UK geohazard note 577 KB pdf on naturally occurring radon.
Small amounts of radioactive material can be found in food and drink, e.g. brazil nuts, shellfish and bananas. The radioactive content is present as a proportion of the potassium in these foods. As potassium is essential to a healthy diet, the risk from avoiding such foods is greater than the risk from enjoying them as part of a balanced diet.
Cosmic radiation is natural gamma radiation that comes from outer space. Despite being partially absorbed by the atmosphere, a significant amount reaches the Earth's surface. Exposure to radiation from this source increases with altitude: a transatlantic flight will increase an average person's annual dose by about 2.5 per cent.
Articifial radiation has medical uses, such as diagnostic X-rays and therapeutic treatments for cancer and other conditions, such as overactive thyroid.
Industrial uses include electricity generation, sterilisation of equipment, thickness gauges in textile manufacture and the paper making industry, and level detectors for hoppers in agriculture and the mining industry.
Fallout from historical weapon detonations and from incidents and accidents such as those at Chernobyl and Fukushima is another source.
In the UK approximately 15 per cent of the average annual dose comes from medical procedures. Industrial uses and fallout together are responsible for less than one per cent of the average annual dose.
Radioactive waste is generated in various industries including mining, oil and gas extraction, medical facilities, the nuclear industry, land remediation and research.
The waste can be divided into three types depending on the amount of radioactivity.
The UK has been operating commercial nuclear reactors since 1956 with up to 28 per cent of our electricity being generated in nuclear power stations over this period. This proportion has now dropped to about 17 per cent because the older nuclear power stations have reached or are approaching the end of their working lives. All but one of those still operating will be retired by 2023. Whether or not we build new nuclear power stations, we have a legacy of radioactive waste from over 50 years of commercial exploitation of nuclear power for which a safe, long term means of disposal is required.
The current accumulated waste volume from power generation, other industrial uses and medical uses is approximately 400 000 m3, enough to fill Wembley Stadium about three and a half times. Many earth scientists agree that deep geological disposal of radioactive waste in a suitable geological environment is the best means of disposing of this waste.
The White Paper says that BGS will undertake a desk-based study of the geology of England, Wales and Northern Ireland to assess which areas may be more or less geologically suitable to host a deep geological disposal facility for the disposal of the UK's radioactive waste. This will be undertaken on a regional basis and will use the information held by BGS to identify those areas where rock types and their geological environment is likely to be suitable to host a facility and those less likely to be suitable. This work will be undertaken over the next two years and the resulting reports will be available to all stakeholders to provide information for decisions on whether to participate in the process of identifying a site for a deep geological disposal facility or not.
Whilst there are risks associated with disposal of any industrial waste, be it radioactive or not, results from experiments and test sites from all over the world agree that, provided all the appropriate conditions are chosen, there is a low risk to human health from deep geological disposal of radioactive waste. Methods of disposal have been, and are continuing to be, extensively tested by a wide range of organisations, including here at BGS. The amount of high-level radioactive waste, the most radioactive material, is proportionally very small (0.07 per cent of total radioactive waste). Another feature of radioactive waste is that radioactivity decreases with time — after about 600 000 years the radioactive waste will be less radioactive than the uranium ore from which the fuel was made. It is also important, when considering the effects of radioactive waste, to take into account the natural background levels of radiation that we experience all the time.
The surface above the deep geological disposal facility will most likely look like an office park or a small industrial estate, with a series of small to medium sized buildings on the site. At other sites around the world where underground research laboratories have been constructed deep below the surface, for example in Sweden, France, Belgium and Japan, the surface footprint is small and consists of a few medium sized buildings.
A deep geological disposal facility would be constructed in a similar way to a deep mine, using special machinery to dig down to the appropriate depth, putting in supports to preserve the structure along the way, and will likely be about 200 – 1000 m deep. The radioactive waste will be placed into specially constructed galleries in the rock. The waste itself will be placed into a protective canister. The canister is made of different layers (or blankets) of material that are placed around the waste to protect the environment. Each of the layers acts as a barrier to protect the waste from leaking out. The rock also acts as one of these layers or barriers; in fact it is the final outside barrier. Inside the rock, there are layers of artificial materials each with different properties and providing different types of shielding. These artificial layers are called the engineered barriers. The structure is similar in some ways to a Kinder egg!
The suitability of a location for the development of a deep geological disposal facility for radioactive waste largely depends on groundwater flow. This relates not only to how fractured or cracked the rocks are, but also how much water moves through them. If groundwater flow is low (for example, if the cracks or fractures are not connected to each other), then an area with fractured rocks could still be suitable.
The suitability of a location for the development of a deep geological disposal facility for radioactive waste largely depends on groundwater flow. This relates not only to how porous the rocks are (how much open space or how many voids/holes there are in the rock), but also how much water moves through them. If the spaces are not connected to each other so that water cannot flow from one to another then groundwater flow would be low and then an area with porous rocks could still be suitable.
Deep geological disposal is planned for depths of between 200 and 1000 metre4s below the surface and in the UK this means that the facility will be constructed below natural groundwater levels. At this depth, the water levels are not affected by the weather and any existing groundwater conditions around the deep geological disposal facility will not change whether there is flooding or not. Surface flooding will have no effect on the suitability of the site at this depth; the only impact would be on the location of the surface buildings.
BGS undertakes research into a wide range of issues relevant to deep geological disposal of radioactive waste, with a particular emphasis on understanding the properties of different rocks (such as the strength of the rocks, what the rocks are made of, how the rocks behave at different temperatures) and how these properties influence the way radioactivity moves in the geological environment. We have extensive experience of engineered barriers (such as clays and cements), geological disposal facility host rocks and overlying geology. Our studies in this area focus on the physical, chemical and biological processes that affect how the properties of the rocks may change over long periods of time.
Research examples include:
Micro-organisms (microscopic creatures such as bacteria) around a deep geological disposal facility could slow the movement of radioactivity. The use of micro-organisms may be in the form of artificially grown biofilms. These films plug the spaces through which water and gas could otherwise flow. Our research examines the impacts of microbial activity on different rock types under the conditions likely to be found in a facility.
Decay and corrosion of the waste and construction materials in a deep geological disposal facility leads to the formation of gases that may contain some radioactivity. Whilst a facility aims to limit gases from reaching the near surface, pressures from gas build-up may open pathways or force groundwater through the waste and surrounding rocks. Our research examines how gases form and move through the facility and surrounding rocks.
Modelling the geology below the surface using a computer and specialised software is an important part of the process of siting a deep geological disposal facility. It allows the geologists to better understand the geology and to visualise it in a way not possible in the past. It can also be a powerful communication tool to present the geological understanding of an area to interested people including the public, councillors and others involved in the siting process. More information on 3D geological modelling.
Natural, archaeological and industrial analogues are equivalent structures that have similar properties to parts of deep geological disposal facilities. They have a unique role to play in helping us understanding the evolution of facility system components over timescales beyond those that we can practically or realistically test with most laboratory experiments. Download Earthwise Issue 21 for more information 6.11 MB pdf.
Low-level waste (LLW) is generated from hospitals and industry, as well as from nuclear fuel. It includes paper, rags, tools and clothing that contain small amounts of mostly short-lived radioactivity. It does not require shielding during handling and transport, and is suitable for shallow land burial. To reduce its volume, it is often compacted before disposal. 82.67 per cent of the volume of waste produced in the UK is low-level, but it accounts for 0.0003 per cent of the radioactivity of all radioactive waste.
Intermediate-level waste (ILW) contains higher amounts of radioactivity and some requires shielding, such as protective clothing, between stored waste and humans. It typically includes chemical sludges and metal fuel cladding as well as contaminated materials from reactor decommissioning. Smaller items and non-solids may be solidified into vitreous waste, like glass. In the UK, ILW makes up 17.26 per cent of the volume and has 5.8 per cent of the radioactivity of all radioactive waste.
High-level waste (HLW), generated from the 'burning' of uranium fuel in a nuclear reactor, is the most radioactive waste produced and can be long- or short-lived. HLW contains products generated in the reactor core. It is highly radioactive and hot, so requires cooling and shielding. HLW accounts for over 94.2 per cent of the total radioactivity produced industrially, but only approximately 0.07 per cent of the volume of radioactive waste produced in the UK.
For further information please see the Nuclear Energy Agency's briefs: The disposal of high-level radioactive waste and The management of low- and intermediate-level radioactive waste.
A single uranium fuel pellet is often less than a centimetre long. The pellets are placed together in long tubes, which form the fuel rods in nuclear reactors and are used in bundles. When depleted, the bundles of fuel rods are placed in purpose built canisters and may be encased in swelling clay for disposal in suitable rocks.
This depends on which area is selected for a deep geological disposal facility. It is expected that the facility will have an underground footprint area of around 10 km2, so it is possible that some part of the facility will be under private property. However, the minimum depth below the surface is 200 – 1000 m, the equivalent depth of between two and ten Big Bens stacked on top of each other.
At the moment no other country has a fully operating deep geological storage facility for high-level radioactive waste. There are however a number of countries that are further along in the process than the UK. Some countries have chosen to create high-level research facilities below ground at the depth a facility would be and in similar rocks. This allows them to gain better knowledge of the rocks being considered and to run experiments and long-term tests on the rocks and the engineered barriers. Such underground research facilities are operational in Belgium, France, Japan, Korea and Switzerland, with many more under construction. Underground deep geological disposal facility sites for intermediate-level waste are in operation in Germany, Sweden and the USA, and considerable knowledge and experience has been gained from these sites being operated.
The radioactive waste will be disposed of permanently. Before any deep geological disposal facility is licenced to accept radioactive waste, it must undertake a comprehensive safety assessment. In the UK this assessment is required to consider how the facility will perform over a period of one million years following its closure. This assessment must demonstrate that it can meet the strict requirements set out in both international and national legislation and back it up with evidence. In less than one million years the radioactive waste in the repository will be significantly less radioactive than the ore deposits from which the uranium was originally mined.
There are many layers of engineered (artificial) barriers to be breached before the radioactive waste could come into contact with the groundwater or host rocks. The reason for the careful site selection process is because the geology will form a part of the barrier and will reinforce and support the engineered barriers with different properties. One of the most important barriers is a layer of clay called bentonite. Bentonite clay has special properties that reduce the rate at which radioactivity can move out of waste while at the same time prevent groundwater from passing into the waste. Research is currently being undertaken by BGS and others to help understand the different ways that geology can interact with the bentonite clay and other materials.
Decay and corrosion of the waste and construction materials in a deep geological disposal facility eventually lead to the formation of gases, which may contain some radioactivity. The presence and flow of any gas produced from disposing waste underground would depend on the types of rocks that host the facility; however the design of any engineered barriers would take the potential of gas formation into account. Most of the gas produced in a deep geological disposal facility is not radioactive.
The risks from attempting to dispose of radioactive waste in space are much greater than that of deep geological storage. The potential for any storage transporter to explode on its journey through the atmosphere and distribute the waste across a wide area are too high to contemplate.
No. When spent nuclear fuel that has been sent to the UK from other countries has been re-processed, the extracted usable uranium and associated waste will be returned. While this may not be exactly the same material, the total amount of uranium and radioactivity contained in the resulting waste is returned to the country it came from.
For information that relates to radioactive waste and the design of the engineered storage please visit the Nuclear Decommissioning Agency website. For more information about the work that BGS is doing in researching the behaviour of different types of rocks in relation to how they are affected by the storage process, see also:
Contact Dr Richard Shaw for more information.