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Understanding activities that produce radioactive wastes in the UK 1

Understanding activities that produce radioactive wastes in the UK

Understanding activities that produce radioactive wastes in the UK

Conditions of Publication

The NDA is seeking to make information on its activities readily available, and to enable interested parties to have access to and influence on its future programmes.

The report may be freely used for non-commercial purposes. However, all commercial uses, including copying and re-publication, require permission from the NDA. All copyright, database rights and other intellectual property rights reside with the NDA. Applications for permission to use the report commercially should be made to the NDA Information Manager.

Although great care has been taken to ensure the accuracy and completeness of the information contained in this publication, the NDA cannot assume any responsibility for consequences that may arise from its use by other parties.

© Nuclear Decommissioning Authority 2015. All rights reserved

Please do not hesitate to contact the NDA if you have any queries about radioactive waste. Such feedback and queries should be addressed to:

Nuclear Decommissioning AuthorityInformation Access ManagerHerdus HouseWestlakes Science & Technology ParkMoor RowCumbriaCA24 3HU

Email: [email protected] Tel: 01925 802077

Contents

Introduction 3

About the NDA 4

What is radioactivity and radiation? 5

What is radioactive waste? 7

How much radioactive waste is there? 9

What activities produce radioactive wastes? 10

An overview of the activities in the nuclear fuel cycle that produce radioactive wastes 16

How radioactive wastes are managed 20

Factsheets 26

Radioactivity 27

Radioactive wastes 30

Uranium mining and milling 32

Uranium enrichment and fuel manufacture 35

Operating a nuclear power reactor 38

Spent fuel reprocessing 44

Decommissioning of nuclear power facilities 49

Wastes from defence activities 56

Wastes from research activities 58

Wastes from medical activities 61

Wastes from industrial activities 63

Glossary and definitions 65

Ref: 23527545


Introduction

In the UK, we use radioactive materials for a range of purposes, such as generating power, treating medical illnesses and conducting research. Radioactive materials are also used in the industrial and defence sectors.

Waste is often generated as a by-product from these processes. Materials that have no further use, and are contaminated or activated by radioactivity above certain levels, are known as radioactive wastes.

This report provides an overview of how radioactive wastes are produced in the UK and should be particularly useful for those who are new to the nuclear sector or those with a general interest in the topic.

This report is in two parts. The first part provides an introduction to radioactivity, an overview of the nuclear fuel cycle and information about how radioactive wastes are produced and managed. The second part is a series of fact sheets that provide more detail on the main activities and processes that create radioactive wastes.

If you need any further information, there are many other technical reports available on our website www.nda.gov.uk

Image: Waste storage at the Low Level Waste Repository in Cumbria


About the NDA

The Nuclear Decommissioning Authority (NDA) was established by Government in 2005. We take responsibility, on behalf of the Government and taxpayers, for overseeing the clean-up and decommissioning of 17 of the UK’s civil public sector nuclear sites. These sites range from Sellafield, which is a complex industrial site spread across two square miles, to smaller sites containing nuclear research facilities.

We aim to deliver safe and sustainable solutions to the challenge of nuclear clean-up and waste management. This means:

• never compromising on safety or security• taking full account of our social and environmental responsibilities• always seeking value for money for the taxpayer• actively engaging with stakeholders

We deliver our mission through others, primarily Site Licence Companies (SLCs), which are licensed to operate our nuclear sites. At least every five years we review and publish a strategy that sets out our strategic direction and describes our long-term objectives.

Some of our facilities continue to form an essential part of the nation’s nuclear infrastructure, which means they must continue to be operated safely and effectively until they have fulfilled their purpose.

Continued operation of these facilities and successful clean-up depend on the availability of suitable waste management routes and facilities. Managing waste effectively is essential to the delivery of our mission and is a significant part of our programme.

We are not responsible for radioactive wastes produced at commercial nuclear power stations that are operated by other organisations in the UK, or for wastes produced in the industrial or defence sectors. However, we do work with companies in these sectors to share knowledge and experience. The activities that lead to the production of those wastes are also described in this report to give a complete national picture.

Hartlepool

Heysham

Torness

Spent fuel reprocessing

Nuclear power reactors

Culham

Nuclear energy R&D

Harwell

Defence

Vulcan

Clyde

Rosyth

EskmealsBarrow

Derby

Donnington

Devonport

Portsmouth

Aldermaston

Fuel fabrication & uranium enrichment

Medical & industrial

Waste disposal facility

Cardiff Amersham

Sheffield

Silwood Park

Sellafield

Wylfa

Trawsfynydd

Chapelcross

Hunterston

BerkeleyOldbury

Hinkley Point

Dungeness

Bradwell

Sizewell

Dounreay

Winfrith

Springfields

Capenhurst

LLW Repository

Burghfield

NDA Sites

Image: The map shows the locations of the major radioactive waste producing sites in the UK. There are no major radioactive waste producers in Northern Ireland. There are many sites that produce small amounts of radioactive waste (such as hospitals, industrial, educational facilities) that are not shown.


What is radioactivity and radiation?

Atoms are the basic building blocks of matter. Some unstable atoms break apart spontaneously over time in a process called radioactive decay. When this happens radiation is released, mostly in the form of particles (alpha and beta) and electromagnetic energy (gamma rays). Free neutrons can also be ejected from the atom’s nucleus when the atom splits (neutron radiation).

An alpha particle is made up of two protons and two neutrons. A beta particle is an electron. Neutron radiation consists of fast moving neutrons. Gamma rays, like visible, infrared, and ultraviolet light, are part of the electromagnetic spectrum.

The released radioactivity may travel through air and some materials. While alpha radiation can be stopped by a thin sheet of paper and beta radiation can be stopped by a thin sheet of metal, gamma radiation may need a thick block of concrete or metal (e.g. lead) to stop it.

The activity of a radioactive substance decreases over time. The time it takes for the amount of radioactivity to decrease by half is called the half-life. Different radioactive atoms have different half-lives: some can be a less than a second and some can be many thousands of years.

Elements and isotopesAn atom is made from a nucleus surrounded by electrons. The nucleus contains particles called protons and neutrons. An element (such as hydrogen, gold or uranium) is a substance that cannot be broken down into simpler substances by chemical means. Elements are distinguished by the number of protons in the nuclei of its atoms.

Isotopes are variations of an element which have the same number of protons but different numbers of neutrons. As an example, the two common isotopes of uranium both have 92 protons in their nucleus but different numbers of neutrons: uranium-235 has 143 neutrons and uranium-238 has 146 neutrons.

Different isotopes of the same element will have the same chemical properties but slightly different physical properties. The small difference in their masses means that isotopes can be separated from each other. The ability to separate isotopes is important in the manufacture of nuclear fuel.

Image top: The basic structure of an atom.Image bottom: How the different types of radiation may be stopped by materials

Nucleus

Electron,negative charged

Neutron,neutral charge Proton,

positive charge

Alpha

Beta

Gamma

Alpha radiation can be stopped by skin or paper.

Beta radiation can be stopped by a thin sheet of aluminium.

Gamma radiation requires several centimetres of lead or concrete to be stopped


Natural and artificial sources of radiation

Radioactive decay is a natural process that has been happening continuously since the Universe was created. Many of the everyday materials in our environment contain naturally-occurring isotopes that undergo radioactive decay and emit radiation. These contribute to the total background radiation.

In the UK, about half of the natural radiation we receive comes from radon gas. This gas is formed by radioactive decay of the small amounts of uranium that is present naturally in rocks and soils.

Other sources of natural radiation are cosmic rays from space and naturally-occurring isotopes such as carbon-14, which is found in all animals and plants, and in the food we eat.

Radiation can also be man-made. The most significant source of artificial radiation for most people is exposure to medical X-rays.

The total amount of background radiation we experience is low. About 84% of this background radiation is from natural sources, about 15% from medical practices and less than 1% from nuclear power, industrial and defence activities.

Radon, 50%

Medical, 15%

Fallout 0.2% Occupational 0.2%

Nuclear discharges <0.1%Products <0.1%, 1.0%

Gama rays (from buildings and the ground), 13%

Cosmic rays, 12%

Internal (from food and drink), 9.5%

Other <1%Fallout 0.2% Occupational 0.2%Nuclear discharges <0.1%


What is radioactive waste?

Waste is any substance or object which the holder intends to or is required to discard. A ‘radioactive waste’ also contains radioactivity above certain levels defined in legislation.

Some radioactive substances or objects are not considered to be wastes because they have potential value and could be used in future. This includes uranium and plutonium, which could be used to make nuclear fuel. This also includes spent nuclear fuels, which could be reprocessed and reused. These are called radioactive materials.

At present, these materials are being safely stored in case they are needed in future. If Government decides that these materials have no future use, they would then be reclassified as waste. The Government will make this decision based on economic, environmental and safety grounds.

Naturally-occurring radioactive materials (NORM), such as rocks and minerals, are not considered to be radioactive waste when they are in their natural state. NORM wastes arise when these materials are concentrated through industrial activities, for example mining and mineral processing, or drilling for oil.

How do wastes become radioactive?

Radioactive wastes are produced as a by-product from many important industrial, medical, research and defence activities. The nuclear industry as a whole works hard to reduce the amount of radioactive waste it produces, but some waste production is unavoidable.

When we use radioactive materials, some radioactive material will inevitably be transferred to the things they come into contact with, causing them to become ‘contaminated’. This leads to radioactive wastes being generated. These wastes include everyday items such as equipment and tools, water and air filters, and the protective clothes that workers wear. In nuclear reactors, most of the internal components (such as tanks and pipes) will come into contact with radioactive materials during normal operations and will become contaminated.

Another way that items can become radioactive is if a material is in contact with (or close to) a source of neutron radiation. The free neutrons interact with the nuclei of other atoms to form new isotopes. These isotopes may be unstable, undergo radioactive decay and release further radiation. Items that have been subjected to neutron radiation and have become radioactive as a result are said to have been ‘activated’ by radiation.

This can occur in the core of a nuclear reactor when free neutrons are released by the fission (splitting apart) of uranium in fuel. A common example is when stable cobalt (cobalt-59), which is added to steel to make it corrosion resistant, becomes activated to form radioactive cobalt-60.

One important difference between contamination and activation is that contamination tends to occur only on the surfaces of materials but activation also occurs inside materials. A second important difference is that contamination can potentially occur where ever there are radioactive materials, but activation can only occur in the presence of a strong neutron emitter.

Many of these contaminated and activated components will be classed as radioactive waste when the facility is eventually shut down and decommissioned. These ‘decommissioning wastes’ form the greatest amount of radioactive waste in the UK.


What is radioactive waste made from?

Most radioactive waste produced in the UK is solid and made from a variety of materials and items, including discarded protective clothing used by workers, redundant tools and equipment, or concrete and steel from dismantled buildings.

Some radioactive wastes are liquids or sludges, but these are usually turned into solids by drying them or incorporating them into a solid matrix (usually cement or glass) to make them more stable and easier to contain.

A few types of radioactive waste gases are produced, such as radon, but only in relatively small amounts.

How radioactive waste is classified

In the UK, radioactive wastes are classified according to the type and quantity of radioactivity they contain and how much heat that this radioactivity produces.

High level wastes (HLW) are those wastes where the temperature may rise significantly as a result of their radioactivity, so this factor has to be taken into account in the design of waste storage or disposal facilities.

HLW arises as a liquid from the reprocessing of spent nuclear fuel. These liquids are subsequently treated to form solid glass blocks.

Intermediate level wastes (ILW) are those exceeding the upper boundaries for LLW that do not generate sufficient heat for this to be taken into account in the design of waste storage or disposal facilities.

The major components of ILW are metal items such as nuclear reactor components, graphite from nuclear reactor cores and sludges from the treatment of radioactive liquid effluents.

Low level wastes (LLW) are those which contain relatively low levels of radioactivity. More specifically, wastes where the radioactive content does not exceed 4 GBq (gigabecquerels) per tonne of alpha, or 12 GBq per tonne of beta/gamma activity.

Most LLW comes from the operation and decommissioning of nuclear facilities, and is mainly scrap metal items, paper and plastics. Some smaller amounts of LLW also come from hospitals and universities.

Very low level waste (VLLW) is a sub-category of LLW with specific activity limits. VLLW includes small volumes of waste, principally from hospitals and universities that can be safely disposed of with household, commercial or industrial waste (either directly or after incineration), and larger volumes of waste from nuclear sites that can be disposed to appropriately permitted landfill facilities. The major components of VLLW from nuclear sites will be building rubble, soil and steel items arising from the future dismantling and demolition of nuclear reactors and other nuclear facilities.


How much radioactive waste is there?

Every three years, Government and the NDA publish reports that describe the UK’s Radioactive Waste & Materials Inventory1. These reports provide information on the amounts and types of radioactive waste that have already been produced and estimates of future waste arisings. Information is also provided about radioactive materials; these are items that are not classed as waste now but may be in future if no further use can be found for them.

The inventory is an estimate based on the best available information at a specific point in time. The inventory of wastes and materials that exists is continually evolving, as new wastes are being created, treated and disposed. Forecast waste arisings may also change due to advances in waste processing methods, commercial decisions about how many new reactors may be built or changes to decommissioning plans.

Information about the estimated waste volumes and types is needed for future waste management planning. The latest inventory data, collected in 2013, shows the different types of waste that will be produced, from all sources including future arisings will be:

Total reported volume by waste type (m3)High Level Waste (HLW) 1,100Intermediate Level Waste (ILW) 290,000Low Level Waste (LLW) 1,400,000Very Low Level Waste (VLLW) 2,800,000Total 4,500,000

To put these numbers into perspective, the volume of St Paul’s Cathedral, in London has been estimated as 152,000 m3. So, to contain all of the radioactive waste produced over whole lifetime of current facilities (another 100 years), we would need the equivalent space of 31 cathedrals. This sounds like a lot, but to put this into context, we produce 31 cathedrals worth of household waste every nine weeks in the UK!

Although the greatest volume of radioactive waste is VLLW, the vast majority of the radioactivity (over 90%) is contained in the relatively small volume of HLW.

Around 91% by volume of all radioactive wastes are produced in England, 6% in Scotland and 3% in Wales. There are no major radioactive waste producers in Northern Ireland.

ILW

LLW

HLW

5%0.00005%

95%

VLLW63.2%

LLW30.4%

ILW6.4%

HLW0.02%

Total volume 4.5 million cubic metres

Images: The relative proportions of the different types of radioactive waste, this includes all waste that is in stock and forecast to arise in the UK. Left: by volume and right by activity. HLW is only a very small proportion of the total waste volume but contains most of the activity.

1 DECC & NDA (2015) UK Radioactive Waste Inventory www.nda.gov.uk/ukinventory


What activities produce radioactive wastes?

A range of activities lead to the production of radioactive wastes in the UK. Radioactive wastes are produced as a by-product from nuclear power generation and from defence, research, medical and industrial activities.

This section of the report outlines the key activities. Further detail can be found in the factsheets.

The nuclear fuel cycleThe ‘nuclear fuel cycle’ is the sequence of industrial activities needed to process radioactive materials to manufacture nuclear fuel and generate electricity by nuclear power. It also includes the activities needed to manage the spent (used) nuclear fuel afterwards.

Fuel fabrication

Enrichment

Conversion

Natural Uranium

Spent fuel storage

Transport

Reprocessing

Uranium and plutonium from spent fuel

U and Pu could be converted into a stable form for disposal.

Reactor

Depleted uranium

Image left: Spent fuel storage ponds at Oldbury Image above: The nuclear fuel cycle and the main activities that lead to radioactive wastes being produced.


Mining and milling

The nuclear fuel cycle starts with uranium mining in places such as Asia, Africa, Canada and Australia where large uranium ore deposits are found.

Once the uranium ore has been mined, it is crushed and milled at the mine to separate out the uranium-bearing minerals from other minerals in the rock. The uranium-rich material that is collected is a yellow powder called yellowcake because of its colour. Yellowcake is a uranium oxide and is the basic raw material for manufacturing nuclear fuel.

Milling also produces very large amounts of crushed rock waste material known as ‘tailings’ that are usually collected and stored as large piles and slurry ponds at the mine site.

Although there are some uranium ore deposits in the UK, they are generally quite small and uneconomic to mine. For this reason, there is no commercial mining or milling in this country, and so no wastes from these activities are produced here.

Uranium enrichment

Some yellowcake produced in overseas uranium mills is shipped to the UK, where it is processed in uranium conversion and enrichment plants.

Yellowcake is a uranium oxide which contains uranium isotopes in their natural proportions. The majority is uranium-238 (more than 99%) with the remainder being uranium-235 (about 0.7%) and uranium-234 (less than 0.1%).

The uranium-235 isotope is needed to power a nuclear reactor. However, the small amount of this isotope that occurs naturally is not sufficient to sustain a nuclear chain reaction. This means it has to be concentrated (‘enriched’) before the fuel can be manufactured.

Centrifuges are commonly used to enrich the uranium-235 by separating it from the uranium-238, taking advantage of the very small mass difference between these isotopes. The solid uranium oxide is first converted to a gas (UF6 uranium hexafluoride known as ‘hex’). A centrifuge spins this gas at a very high speed which forces the heavier uranium-238 isotope to move towards the outer rim, and separates it from the lighter uranium-235.

This enrichment process produces a lot of secondary ‘depleted uranium’ by-product which contains most of the uranium-238. This is not a waste because of its potential energy value and because it has a range of other possible uses. The NDA currently safely stores its depleted uranium stocks.


Fuel fabrication

The older, first generation nuclear power reactors in the UK used a uranium metal fuel but these reactors have now reached or are reaching the end of their operational lifetimes. No new metal fuel is required.

The newer reactor designs use uranium oxide (UO2) fuel. To manufacture this fuel, the enriched uranium is converted back from ‘hex’ to a solid uranium oxide powder, which is then used for manufacturing fuel. To make the fuel, this powder is compressed and baked to form solid ceramic fuel pellets.

Each pellet is about one centimetre across, and many pellets are encased (clad) within metal fuel rods. Multiple fuel rods are arranged together to produce complete fuel assemblies. Many different fuels and assembly designs are manufactured to fit particular reactor types for UK and overseas customers.

Fuel manufacture produces relatively small amounts of waste compared to other activities in the nuclear fuel cycle.

Reactor operations and electricity generation

Newly manufactured fuel assemblies are transported to the operating nuclear power reactor sites around the UK for loading into the reactor cores. A typical commercial nuclear reactor contains around 100 tonnes of enriched uranium fuel.

During the operation of a nuclear reactor, the nucleus of a uranium-235 atom captures a free neutron to form the heavier uranium-236 isotope. This is unstable and so spontaneously fissions (splits apart) into two smaller atoms, known as fission products. This process releases heat energy and more neutrons that cause further fissions to occur in a chain reaction. The chain reaction is controlled by using materials that can absorb excess neutrons. This is the essential process used to produce energy in a nuclear power reactor

The heat given off as a result of fission can be used to generate steam, which drives turbines for electricity generation in much the same way as any other power station. To maintain efficient operation and to ensure enough heat is produced by the reactor, about one-third of the nuclear fuel needs to be replaced every 12 to 18 months, as it is gradually used up.

The spent (used) fuel removed from the reactor is stored in a cooling pond at the reactor site for at least several months to allow radioactive decay to reduce the amount of heat emitted by the fuel. This spent fuel is not considered to be a waste because the remaining uranium-235 and other elements it contains may potentially be recovered by reprocessing.

Routine operation of a nuclear power reactor produces radioactive waste but not in very large amounts. The main operational wastes produced are the resins used to extract radioactive and chemical contamination from liquids, such as the cooling pond waters, as well as any used components and protective clothing that may be contaminated.

Image: Fresh uranium oxide fuel pellets. Source - P. A. Scholle & D. S. Ulmer-Scholle, 1997, SEPM Photo CD-14, Environmental Sciences 5, SEPM, Tulsa, OK.



Typical spent fuel contains less than one third of the uranium-235 that was present in the pre-irradiated fuel. The rest is converted to various fission products during the nuclear reactions that take place inside the reactor. Plutonium is also produced in a reactor when uranium-238 in the fuel absorbs a neutron and undergoes beta decay.

Reprocessing enables the remaining uranium and the plutonium to be recovered. The uranium recovered by reprocessing can be reused to manufacture new fuel pellets. The plutonium can also be used together with uranium to manufacture new fuel, such as mixed oxide fuel (MOX).

The processes used for managing spent fuel from Magnox and Advanced Gas-Cooled Reactors (AGR) in the UK are broadly similar, although there are some technical differences which are not detailed here.

Reprocessing spent fuel is a complex process that first involves separating the spent fuel from the metal components of the fuel assemblies. Then the spent fuel is dissolved in acid and a chemical separation process is used to recover the uranium and plutonium.

In the UK, spent fuel is currently reprocessed at Sellafield. A variety of spent fuels were also reprocessed at the Dounreay site until the mid-1990s.

It is intended that no spent fuel will be reprocessed in existing facilities after 2020. The spent fuel that is not reprocessed will need to be stored until the disposal route becomes available. Work is underway to develop a Geological Disposal Facility (GDF) for higher activity wastes and spent fuel requiring disposal.

Image: Sellafield reprocesses spent oxide fuel in the thermal oxide reprocessing plant (THORP)


Vitrification of the reprocessing wastes

The residual acidic liquid produced by reprocessing spent fuel contains most of the unwanted fission products. This liquid is highly radioactive and generates heat, which means it has to be handled very carefully and must be converted to a stable solid form for storage. This is done by evaporation to produce a dry powder which is then incorporated into molten borosilicate glass. The molten glass is then poured into stainless steel canisters, where it cools and solidifies. This process is called vitrification, and produces a heat and corrosion resistant glass product.

This glass product is classified as HLW. The canisters containing the glass HLW are safely stored at Sellafield until a way to dispose of them has been developed. Work is underway to develop a Geological Disposal Facility (GDF) for higher activity wastes, including the HLW produced by the reprocessing of spent fuel.

Several other radioactive wastes are also produced during the different stages of reprocessing and vitrification. These are mainly wastes classified as ILW, and include the metal cladding separated from the spent fuel and items such as filters that are used to clean (‘scrub’) the gases generated during the high temperature process.

Image: The liquid waste from the reprocessing of spent fuel is dried, mixed with glass, melted and then poured into stainless steel canisters.


Decommissioning

At the end of the operational life of a nuclear reactor, or any other nuclear facility, it will need to be decommissioned. This involves the decontamination and full or partial dismantling of buildings and their contents to achieve an agreed site end state.

Before sites develop their decommissioning plans, it is good practice for them to ensure that they have an understanding of the types of waste that will arise from decommissioning and the proposed approach to waste management.

Once a facility has been shut down, there is a transition phase during which the facility is prepared for decommissioning. This includes removing any fuel and other readily accessible radioactive materials and contaminated equipment. Liquids are drained from pipes and tanks, which are also removed.

Following this transition phase, facilities are decontaminated, which means removing radioactive contamination which may be on surfaces. This makes the later stages of decommissioning easier and reduces the total volume of radioactive waste arising.

After a nuclear facility has been decontaminated, it can be dismantled and, depending on the proposed end state, demolished.

Remediation may also be required to manage any areas of contaminated soil or groundwater. This ensures the protection of people and the environment during the next use of the site.

Decommissioning may be carried out immediately following permanent shutdown and transition or may be deferred for a predetermined period. The deferral period can range from a few months to a number of decades depending on the size and complexity of the decommissioning project, and the purpose of deferral. A deferred decommissioning strategy is typically selected to take benefit from radioactive decay of the shorter lived isotopes (reducing the radiation hazard and the activity inside the reactor itself) or to manage constraints such as the availability of waste management infrastructure or financial resources.

Decommissioning produces large volumes of concrete, brick, steel and soils that need to be managed. A small proportion is managed as radioactive waste, but the majority is non-radioactive, such as bricks and concrete from office buildings. These non-radioactive wastes can be managed in the same way as conventional demolition rubble and some can be reused and recycled.

Image: Demolishing the fuel fabrication plant at the Dounreay nuclear site in Scotland.


An overview of the activities in the nuclear fuel cycle that produce radioactive wastes

This table provides a summary of the main activities in the nuclear fuel cycle that produce radioactive wastes, together with a list of the main processes involved in that activity and a list of the main types of wastes that are produced.

Activities Processes Examples of Waste Materials Category of Waste

Open cast miningSolution miningMilling of ore

Mill tailingsSlurries

None in the UK

Oxide to fluoride gas conversionGas centrifuge

Depleted uraniumOperational wastes*

ILWLLW

Oxide reconversionHeating and pressingFuel assembly

Operational wastes* ILWLLW

Fuel loading and unloadingReactor operations and using fuel Cooling pond storage

Operational wastes*Spent fuel**

ILWLLWVLLW

Shearing and splitting of fuel elementsDissolutionChemical recovery of uranium and plutoniumVitrification

High level waste glassFuel debris and swarfOperational wastes*

HLWILWLLW

Chemical decontaminationPhysical decontaminationDemolitionLand remediation

Reactor core graphiteConcrete and brickFerrous metalsRedundant equipmentLiquids and sludges

ILWLLWVLLW

HLW = High Level Waste ILW = Intermediate Level Waste LLW = Low Level Waste VLLW = Very Low Level Waste

*Operational wastes arise during the normal day-to-day operations of a nuclear facility. They consist principally of organic materials (such as cellulose and plastic), metals and various inorganic materials. Examples include redundant equipment, used protective clothing, fuel element components, filters, and resins and sludges from the treatment of liquid effluents.

**If declared as waste.

Mining and milling

Conversion andenrichment

Fuel manufacture

Reactor operationsand generation

Spent fuelreprocessing

Facilitydecommissioning


Legacy waste

In addition to radioactive wastes that are produced by current activities in the nuclear sector, the UK has accumulated a large volume of waste from past civil and defence programmes, known as ‘legacy waste’.

When these wastes were generated, the UK faced very different challenges and priorities, and waste arising from these programmes was managed differently compared to how we manage waste today. At the time, waste was not always separated into different types.

Some of these legacy wastes are mixtures of solids, liquids and sludges that are currently contained in purpose-built structures known as ponds and silos, at sites such as Sellafield and Dounreay. The NDA is working to retrieve these wastes so that they can be converted to a solid form of ILW for safe long-term storage, prior to disposal.

Other activities that produce radioactive waste

In the UK, the vast majority of radioactive waste (over 90%) is produced by activities that are part of the nuclear fuel cycle. Much smaller amounts of waste are produced by defence, research, medical and industrial activities.

Image left: A silo at the Sellafield site that contains legacy wastes from past reprocessing operations. Image above: The proportion of radioactive waste (by volume) produced by different parts of the nuclear fuel cycle and other activities in the UK.

ILW

LLW

HLW

5%0.00005%

95%

Defence

Fuel fabrication anduranium enrichment


Nuclear power reactors

Nuclear energy R&D

Medical & industrial

Total reported volume 4.5 million cubic metres includes waste in stock and forecast arisings from 2013-2120

72.2%

5.4%

1%

4%

16.4%


Defence

Radioactive wastes are produced in three main areas of the defence sector.

The first is the nuclear powered submarine fleet. Small amounts of operational wastes are produced by each active nuclear powered submarine. This happens in the same way that wastes are produced by operating a commercial power reactor, although on a much smaller scale.

Larger volumes of radioactive waste are also produced as nuclear powered submarines are retired from the fleet and decommissioned. The Submarine Dismantling Project (SDP) is the name of the Ministry of Defence programme to deliver the safe, secure and environmentally responsible dismantling of 27 submarines. The reactor and other contaminated parts of the submarine will be classed as radioactive waste when the submarines are finally dismantled.

The second area of defence that produces radioactive waste is the production, management and decommissioning of strategic deterrent nuclear weapons.

Finally the third area relates to the production of radioactive wastes from the clean-up of defence sites that may have become contaminated during historic military operations.

Research into nuclear energy and other nuclear applications

The UK maintained a large programme of research into commercial nuclear energy up until the 1980s. Many test and prototype fission reactors, both large and small, were operated at research sites across the country. Most of these experimental reactors are now shut down and are being decommissioned, which generates radioactive wastes.

Research into fusion reactor technology still continues in the UK. This research is mostly done at the Joint European Torus (JET) facility at Culham, which is currently the largest of its kind in the world. Experiments and tests using JET produce small amounts of waste during its operation, mostly contaminated with tritium.

Other academic and industrial research work takes place in many universities and research establishments across the UK. This research is very diverse, ranging from developing new radiotherapy treatments to testing novel solid materials to encapsulate liquid radioactive wastes.


Medical and industrial applications

Radioactive materials are used for a wide range of purposes in the medical industry. In particular, radioactive materials are used for the sterilisation of equipment, and to help diagnose and treat medical illnesses.

Radioactive sources and radiopharmaceuticals (drugs that contain radioactive materials) are manufactured at specialist centres and are transported to hospitals where they are used to diagnose conditions and to treat patients. Many different isotopes and several types of sources (both solids and liquids) are used in medical treatments.

Relatively small amounts of radioactive wastes are produced during the manufacture, use and recycling of radiopharmaceuticals. Used radioactive sources are often returned to the manufacturer for recycling.

The industrial sector uses radioactive sources in a number of ways. The most common use is for non-destructive testing of materials and components. For example, gamma rays emitted from sealed radioactive sources are often used to test the quality of welds or the thickness of products, such as paper.

Some types of smoke alarm commonly used in homes and offices contain the radioactive isotope americium-241 to detect smoke particles. The amount of radioactive material used in these devices is very small.

Another growing industrial application is biological sterilisation. In this process, gamma rays are used to sterilise objects such as surgical equipment before an operation. Irradiation is also increasingly used to preserve food, such as fruit, vegetables and fish, by killing bacteria.

Image: A typical sealed radioactive source used in medical and industrial applications. Source - www.iaea.org


How radioactive wastes are managed

The continued operation of nuclear facilities and the decommissioning of sites both depend on the availability of suitable waste management routes and facilities.

Radioactive waste management involves a series of steps, and those steps depend on the nature of each waste material and what might finally be done with it. Most radioactive wastes are managed in the following way:

• planning: Wherever possible, we aim to reduce the production of wastes. We also plan how wastes will be managed before they arise

• waste treatment: Many radioactive wastes are treated in some way soon after they arise. Waste treatment techniques vary and depend upon the type of waste that needs to be managed and the intended disposal route. Examples of treatment include removing surface contamination, shredding and compacting the waste, drying it and solidifying it by mixing it with cement

• packaging: Most radioactive wastes will ultimately be packaged. This means that the treated waste is placed into specially engineered containers for safe storage and disposal. It also allows for easier handling and transport

• storage: Some wastes have to be safely stored until a suitable disposal route becomes available. Storage may last for a few months to many decades

• transport: Radioactive wastes may need to be transported from the site where they are produced to another location for safe storage or disposal. Transport is usually by road or rail and is subject to strict conditions

• disposal: Placing wastes into specially engineered facilities where they will remain permanently

All activities on nuclear sites, including the management and disposal of radioactive wastes are strictly controlled and monitored by regulators.

Image: Management of low level waste at the Repository in Cumbria


Integrated waste strategy

The NDA has developed an integrated waste strategy that describes how radioactive and non-radioactive waste is managed in a coherent way across all of our sites.

When we make decisions about waste management it is important to consider:

• risk reduction as a priority• centralised and multi-site approaches• application of the Waste Hierarchy

The Waste Hierarchy sets out a priority order for managing waste materials based on their environmental impacts.

In simple terms, the preference is always to avoid producing wastes in the first place.Opportunities to safely reuse or recycle materials are always considered before disposal.

Waste minimisation

When waste generation cannot be prevented, measures are taken to minimise the amount of radioactive waste that is produced.

This is achieved by:

• planning operations, so that the consumption of resources is controlled and kept to a minimum

• minimising the amount of equipment coming into contact with, and becoming contaminated by, radioactive material so reducing the amount of radioactive waste produced

• sorting wastes to identify items or parts of items that are contaminated by higher levels of radioactivity. These ‘hotspots’ can then be separated out and sent for disposal, whilst the remaining material may be suitable for reuse or recycling

• reducing the volume of the waste, to ensure best use of the limited space in our storage and disposal facilities. Techniques for reducing volume include compaction and incineration (for solid wastes) and evaporation and filtration (for liquid wastes)

Waste characterisation

Waste characterisation is the first stage in any waste management process. This involves assessing the waste to collect information about its radiological, physical and chemical properties.

The data collected enables the waste to be classified correctly and a suitable waste management route to be selected.

Image: A summary of the Waste Hierarchy. Disposal is the least preferred option.

Preferred Approach

Waste Prevention

Waste Minimisation

Re-use of Materials

Recycling

Disposal


Reuse

Equipment and materials can be reused either directly, or after refurbishment. This helps to ensure that we make best use of our resources and means that we avoid sending items for disposal that could be useful elsewhere.

An example of reuse in the nuclear sector is the use of ‘mules’. Mules are containers for temporarily storing waste materials until a permanent disposal package is manufactured. After each use, the mules are cleaned, checked and made ready for reuse.

Lead shielding bricks from buildings are also reused within the nuclear sector. Lead is an excellent barrier against radiation.

Recycling

Some radioactive wastes can be safely recycled following treatment at specialist facilities.

Recycling is a good option for managing metals with low levels of surface radioactivity. The waste metal may be cut into pieces and taken to a recycling facility where the contaminated surface is removed, leaving clean metal beneath. The clean metal is then rigorously checked before it can be approved for recycling alongside other metals.

Some metals can also be melted, the radioactive contaminants removed and the clean, molten metal separated out for recycling. This is how the boilers from the Berkeley nuclear power station were recycled.

Some other radioactive materials can also be recycled. For example, lightly contaminated concrete may be crushed and recycled as backfill in a waste disposal facility, but only in specific cases that have been permitted by regulators.

Incineration

Some combustible LLW and VLLW, such as plastic, textiles and oils, can be incinerated. This means burning the waste at very high temperatures in a controlled chamber, in specially authorised facilities. This helps to reduce the volume of waste for disposal by around 90% or more. After incineration, only ash and filter dust is left.

Incineration is also used for certain medical and industrial radioactive wastes. Overall, the total amount of LLW which is currently sent for incineration is small.

Image: The boilers from the Berkeley nuclear power reactor being sent to Sweden for metal recycling.


Storage

Storage is typically used as an interim measure for managing higher activity wastes until final options for disposing of the wastes become available. In some cases, it is necessary to store wastes for several decades, therefore robust storage facilities have been built.

Most wastes are treated to turn them into a stable solid before they are placed in storage. Often this is achieved by mixing the wastes with cement and solidifying the waste-cement mixture in steel drums or concrete boxes.

The HLW produced by reprocessing spent fuel at Sellafield is made into a solid glass (vitrified). These wastes are held at Sellafield in special stores that have been specifically designed to allow the glass waste to cool while their radioactivity decays.

Government policy is that wastes resulting from the reprocessing of overseas spent fuel should be returned to the country of origin, and HLW should be returned as soon as practicable after vitrification.

Image: The radioactive waste store built at the Hunterston A nuclear power reactor site in Scotland


Disposal

If radioactive waste cannot be safely and cost-effectively reused or recycled, it will be disposed. Disposal means placing the waste into specially engineered facilities, or using it as a construction material in the facility, where it will remain permanently.

Disposal of LLW and VLLW

LLW is typically disposed in purpose built facilities. The biggest of these in the UK is the Low Level Waste Repository (LLWR), which is located south of Sellafield, in Cumbria. This has several old, legacy disposal trenches that are now closed. Current disposals are made in a specially engineered facility with concrete-lined disposal ‘vaults’.

At the LLWR, waste is grouted with cement in metal containers to make a robust solid. The grouted metal containers containing the waste are placed within the engineered vaults until the repository can be covered with an engineered cap and closed. Most of the radioactivity in the waste will decay within a few hundred years.

The Dounreay site, in the north of Scotland, has also constructed a LLW repository for its own waste.

Some LLW and VLLW waste streams can be disposed of at suitably authorised and permitted landfill sites alongside household, commercial and industrial wastes. There are controls on the amount of radioactive waste that can be disposed of at these conventional landfill sites.

Image: The Low Level Waste Repository (LLWR) in Cumbria. The waste is grouted inside the red containers.


Disposal of higher activity wastes

‘Higher activity waste’ includes HLW, ILW and a small amount of LLW that cannot be disposed in the LLWR. Currently, there are no long-term disposal facilities available for higher activity wastes in the UK.

At the moment, higher activity wastes are typically treated to turn them into a stable form, packaged and then kept in robust interim storage facilities until a long-term management solution is developed. Management of radioactive wastes is a matter for the devolved Governments, and different policies for managing higher activity wastes are being developed in the countries of the UK.

The UK Government’s policy for managing higher activity wastes is ‘geological disposal’. This involves placing waste deep underground in a Geological Disposal Facility (repository) with no intention to retrieve the waste once the facility is closed. It is proposed that spent fuel that has also been declared as waste would also be disposed at such a facility.

A Geological Disposal Facility (GDF) is a highly engineered facility with multiple engineered barriers, several hundred metres underground and constructed in a suitable geological environment. The combination of the engineered barriers and the host rock will safely isolate the waste from people for many hundreds of thousands of years.

There is no Geological Disposal Facility yet operating but the UK Government is currently developing a site selection process to find a volunteer host community with suitable geology. The geological characteristics of the site are important for the long-term safety of the facility. Most importantly, it should provide a stable environment for the multiple engineered barriers and should not provide any pathways that could allow radioactivity to return to the surface.

The Scottish Government policy is that the long-term management of higher activity radioactive waste should be in near-surface facilities. Facilities should be located as near to the site where the waste is produced as possible. Developers will need to demonstrate how the facilities will be monitored and how waste packages, or waste, could be retrieved. This policy does not cover HLW because there is none in Scotland. It also does not cover spent fuels or radioactive materials that are not presently classified as waste.

The Welsh Government has also decided to adopt a policy of geological disposal for the long term management of higher activity waste and continues to support the policy of voluntary engagement.

Image: Artist’s impression of a Geological Disposal Facility.

26Understanding activities that produce radioactive wastes in the UK

FACTSHEETS:

Contents

Radioactivity 27

Radioactive wastes 30

Uranium mining and milling 32

Uranium enrichment and fuel manufacture 35

Operating a nuclear power reactor 38

Spent fuel reprocessing 44

Decommissioning of nuclear power facilities 49

Wastes from defence activities 56

Wastes from research activities 58

Wastes from medical activities 61

Wastes from industrial activities 63


FACTSHEET:

Radioactivity

Atoms, elements and isotopes

Atoms are the basic building blocks of matter in the natural world.

An atom is made from a nucleus surrounded by electrons. The nucleus contains particles called protons and neutrons. An element (such as hydrogen, gold or uranium) is a substance where all of its atoms contain the same number of protons, giving it unique chemical properties.

Isotopes are variations of an element which have the same number of protons but different numbers of neutrons. As an example, the two common isotopes of uranium both have 92 protons in their nucleus but different numbers of neutrons: uranium-235 has 143 neutrons and uranium-238 has 146 neutrons.

Different isotopes of the same element will have the same chemical properties but slightly different physical properties, due to the differing number of neutrons in the atoms nucleus.

Image top: The structure of an atom, with a central nucleus surrounded by electrons.

Nucleus

Electron,negative charged

Neutron,neutral charge Proton,

positive charge


Radioactivity and radioactive decay

Radioactive decay is the spontaneous disintegration (breaking apart) of an unstable isotope. When this happens radiation is released, mostly in the form of particles (alpha and beta) and electromagnetic energy (gamma rays).

Radiation type Details Stopped by

Alpha (α) Particle made from two protons and two neutrons.Alpha radiation is most harmful if breathed in or eaten. However, it can only travel about 5cm in air and can be stopped by a thin layer of material such as paper, clothing or the skin.

Paper, clothing or the skin

Beta (β) High-speed, high-energy electrons or positrons.Beta radiation is less harmful than alpha if breathed in or eaten, but it can travel further (about 20 cm in air) and is more penetrating. It passes through paper but is stopped by a few millimetres of aluminium or a thin piece of lead.

Thin sheet of aluminium or lead

Gamma (γ) High frequency electromagnetic radiation.Gamma radiation can travel a long way through air, and is extremely penetrating. Several centimetres of lead or metres of concrete are required to stop it. Whilst it is still potentially harmful, it gets weaker as you move away from the source.

Several centimetres of lead or metres of concrete

Other types of radiation are released during nuclear reactions, such as neutron radiation. Neutron radiation happens when a neutron is ejected from the nucleus of an atom. Neutron radiation is emitted by nuclear fusion reactions in the sun, in the form of cosmic rays, and is also produced inside a nuclear power reactor by nuclear fission of the uranium-235 contained in the nuclear fuel.

The free neutron then interacts with the nuclei of other atoms to form new isotopes. These isotopes may be unstable and undergo radioactive decay and release further radiation. Materials that have been bombarded by free neutrons and have become radioactive as a result are said to be activated, rather than contaminated by radiation.

The amount of radioactivity given off by a radioactive substance decreases over time. The time it takes for the amount of radioactivity to decrease by half is called the half-life. Different radioactive atoms have different half-lives: some can be a less than a second and some can be many thousands of years.

Time (days)

Rad

ioac

tivity

Graph: A graph showing radioactive decay of a substance with a half-life of two days.


Natural and artificial sources of radiation

Radioactive decay is a natural process that has been happening continuously since the Universe was created. Many of the everyday materials in our environment contain naturally-occurring isotopes that undergo radioactive decay and emit radiation. These contribute to the total background radiation.

In the UK, about half of the natural radiation we receive comes from radon gas. This gas is formed by radioactive decay of the small amounts of uranium that is present naturally in rocks and soils.

Other sources of natural radiation are cosmic rays from space and naturally-occurring isotopes such as carbon-14, which is found in all animals and plants, and the food we eat.

Radiation can also be man-made. The most significant source of artificial radiation for most people is exposure to medical X-rays.

A very small amount of artificial radiation exposure comes from nuclear weapons testing and the operation of nuclear power plants. In a nuclear power plant, a large amount of the isotope uranium-235 is brought together in a controlled manner to cause nuclear reactions to occur. The heat energy produced by these nuclear reactions is used to generate electricity. These reactions are what give a ‘nuclear reactor’ its name.

The total amount of background radiation we experience is quite low, with about 84% being from natural sources, about 15% from medical practices and less than 1% from nuclear power, industrial and defence activities.

Radon, 50%

Medical, 15%

Fallout 0.2% Occupational 0.2%

Nuclear discharges <0.1%Products <0.1%, 1.0%

Gama rays (from buildings and the ground), 13%

Cosmic rays, 12%

Internal (from food and drink), 9.5%

Other <1%Fallout 0.2% Occupational 0.2%Nuclear discharges <0.1%

Image: The different sources that contribute to background radiation in the UK. Source: Watson, S J, et al (2005). HPA-RPD-001 — Ionising Radiation Exposure of the UK Population: 2005 Review. ISBN 0-85951-558-3.


FACTSHEET:

Radioactive wastes

What is radioactive waste?

Waste is any substance or object which the holder intends to or is required to discard. A ‘radioactive waste’ also contains radioactivity above certain levels defined in legislation.

Some radioactive substances or objects are not considered to be wastes because they have potential value and could be used in future. This includes uranium and plutonium, which could be used to make nuclear fuel. This also includes spent nuclear fuels, which could be reprocessed and reused. These are called radioactive materials.

At present, these materials are being safely stored in case they are needed in future. If Government decides that these materials have no future use, they would then be reclassified as waste. The Government will make this decision based on economic, environmental and safety grounds.

Naturally-occurring radioactive materials (NORM), such as rocks and minerals, are not considered to be radioactive waste when they are in their natural state. NORM wastes arise when these materials are concentrated through industrial activities, for example mining and mineral processing, or drilling for oil.

How do wastes become radioactive?

Radioactive wastes are produced as a by-product from many important industrial, medical, research and defence activities. The nuclear industry as a whole works hard to reduce the amount of radioactive waste it produces, but some waste production is unavoidable.

When we use radioactive materials, some radioactive material will inevitably be transferred to the things they come into contact with, causing them to become ‘contaminated’. This leads to radioactive wastes being generated. These wastes include everyday items such as equipment and tools, water and air filters, and the protective clothes that workers wear. In nuclear reactors, most of the internal components (such as tanks and pipes) will come into contact with radioactive materials during normal operations and will become contaminated.

Another way that items can become radioactive is if a material is in contact with (or close to) a source of neutron radiation. The free neutrons interact with the nuclei of other atoms to form new isotopes. These isotopes may be unstable, undergo radioactive decay and release further radiation. Items that have been subjected to neutron radiation and have become radioactive as a result are said to have been ‘activated’ by radiation.

This can occur in the core of a nuclear reactor when free neutrons are released by the fission (splitting apart) of uranium in fuel. A common example is when stable cobalt (cobalt-59), which is added to steel to make it corrosion resistant, becomes activated to form radioactive cobalt-60.

One important difference between contamination and activation is that contamination tends to occur only on the surfaces of materials but activation also occurs inside materials. A second important difference is that contamination can potentially occur where ever there are radioactive materials, but activation can only occur in the presence of a strong neutron emitter.

Many of these contaminated and activated components will be classed as radioactive waste when the facility is eventually shut down and decommissioned. These ‘decommissioning wastes’ form the greatest amount of radioactive waste in the UK.


What is radioactive waste made from?

Most radioactive waste produced in the UK is solid and made from a variety of materials and items, including discarded protective clothing used by workers, redundant tools and equipment, or concrete and steel from dismantled buildings.

Some radioactive wastes are liquids or sludges but these are usually turned into solids by drying them or incorporating them into a solid matrix (usually cement or glass) to make them more stable and easier to contain.

A few types of radioactive waste gases are produced, such as radon, but only in relatively small amounts.

How radioactive waste is classified

In the UK, radioactive wastes are classified according to the type and quantity of radioactivity they contain and how much heat that this radioactivity produces.

High level wastes (HLW) are those wastes where the temperature may rise significantly as a result of their radioactivity, so this factor has to be taken into account in the design of waste storage or disposal facilities.

HLW arises as a liquid from the reprocessing of spent nuclear fuel. These liquids are subsequently treated to form solid glass blocks.

Intermediate level wastes (ILW) are those exceeding the upper boundaries for LLW that do not generate sufficient heat for this to be taken into account in the design of waste storage or disposal facilities.

The major components of ILW are metal items such as nuclear reactor components, graphite from nuclear reactor cores and sludges from the treatment of radioactive liquid effluents.

Low level wastes (LLW) are those which contain relatively low levels of radioactivity. More specifically, wastes where the radioactive content does not exceed 4 GBq (gigabecquerels) per tonne of alpha, or 12 GBq per tonne of beta/gamma activity.

Most LLW comes from the operation and decommissioning of nuclear facilities, and is mainly scrap metal items, paper and plastics. Some smaller amounts of LLW also come from hospitals and universities.

Very low level waste (VLLW) is a sub-category of LLW with specific activity limits. VLLW includes small volumes of waste, principally from hospitals and universities that can be safely disposed of with household, commercial or industrial waste (either directly or after incineration), and larger volumes of waste from nuclear sites that can be disposed to appropriately permitted landfill facilities. The major components of VLLW from nuclear sites will be building rubble, soil and steel items arising from the future dismantling and demolition of nuclear reactors and other nuclear facilities.


FACTSHEET:

Uranium mining and milling

Overview

The largest uranium ore deposits are found in Asia, Canada, Australia and Africa. Most of the world’s uranium is mined in these countries. There are some uranium ore deposits in the UK but they are too small to be economic and so no commercial mining happens in this country.

Uranium ore is often extracted from the ground in conventional open cast mines, that are essentially just very large open pits, or in deep mines where tunnels are excavated underground.

When the uranium is deep below ground, it is sometimes extracted using in-situ leaching (solution mining). This involves pumping acidic water into the ore to dissolve the uranium, and pumping the uranium-rich water back to the surface.

Milling is a process to separate the uranium from the other metals and minerals in the rock, and to collect the concentrated uranium ore. The product is a fine yellow powder known as yellowcake, which is the basic raw material for manufacturing nuclear fuel.

Even in the richest ore deposits, uranium makes up less than 20% of the total rock. In most deposits it is much less abundant.

This means that both mining and milling produce very large amounts of waste rock, and contaminated waters and sludges. The waste rock is known as mill tailings, and the contaminated water and sludge is held in ponds at the mine and mill sites. These are classed as naturally-occurring radioactive material (NORM) wastes.

What is uranium ore and where is it mined?

There are many different uranium minerals and only a few of these are mined commercially. Many of the mined ores contain uraninite, a uranium-rich ore made mainly from uranium oxide.

The largest uranium ore deposits are found in Asia, Canada, Australia and Africa. There are some uranium ore deposits in the UK but they are too small to be economic and so no commercial mining happens in this country.

How uranium is mined

The method used to mine uranium depends primarily on how deep the ore is and its grade (the concentration of uranium in the ore). The three main options include open cast mining, underground mining and in-situ leaching (solution mining).

Open cast mining

The most common form of mine is an open cast mine and many different rocks and minerals are extracted in this way around the world, including clay and coal. An open cast mine is effectively a large open pit dug into the ground surface.

An open cast mine is usually excavated using explosive blasting and the broken rock removed with excavators. Often this material is used to screen the mine to reduce its visual impact.

Open cast mining is usually the simplest, safest and most cost-effective way to extract ore that is relatively close to the surface, but it does have a relatively high environmental impact. In order to access the uranium ore body, very large amounts of material may need to be excavated, including any soil, vegetation and rock.


Deep mining

Deep mining involves excavating vertical shafts and horizontal or inclined tunnels from the surface to the ore. Much less rock needs to be removed to access the ore compared to open cast mining but the rate of excavation tends to be slower and the process is more hazardous for miners.

In-situ leaching

In-situ leaching (also known as solution mining) is used for extracting uranium from some of the deeper ore deposits and from lower grade ores.

In-situ leaching involves dissolving the uranium contained within the ore underground. The uranium-rich solution is then pumped back to the surface for processing.

This method of mining has the advantage that only the uranium is extracted from the ground. No bulk waste rock is produced and there is much less disturbance to the surface environment than happens with an open cast mine.

The method is only suitable for some types of ore which are contained in porous rock formations that allow the mining solution to flow through them. The ore also needs to be contained within impermeable layers of clay or rock to avoid contamination of the surrounding groundwater aquifers.

Image: Illustration of in-situ leaching of uranium.

Upper clay layer

Lower clay layer

Uranium ore deposit Uranium ore

is dissolved into solution

Injection well: Mining solution pumped

down into boreholes

Recovery well: Solution containing dissolved

uranium extracted

Sand, clays and gravels


Uranium milling

Milling is the process used to extract the uranium from the mined ore or from the mining solution used in-situ leaching.

The first stage of milling is to crush the rock and ore until it is roughly the grain size of sand. Sulphuric acid is then used to leach the uranium from the crushed rock.

A multi-stage chemical process follows to precipitate the uranium from solution or to extract it using ion-exchange resins.

The concentrated uranium is then heated to remove any residual liquid. The final solid product from milling is a fine yellow powder of uranium oxide (predominantly U3O8) that is known as yellowcake. Yellowcake contains the different isotopes of uranium in their natural proportions.

Radioactive wastes produced by uranium mining and milling

Uranium mining and milling produces very large amounts of waste, primarily in the form of excavated rock, ores that contain too little uranium to be profitable and mill tailings.

Mill tailings are produced during the processing of uranium ore. They are sand-like, crushed rock residues, which are left over after the uranium has been extracted. The tailings contain all of the natural, radioactive radium that was present in the original ore, and so produce radioactive radon gas.

Large ponds of waste slurry are also produced because significant volumes of water are used in the milling process. These ponds are usually dammed to contain the slurry and are allowed to dry by natural evaporation.

These wastes are classed as naturally occurring radioactive material (NORM) wastes.

The mill tailings and the slurry ponds have the potential to be damaging to the environment due to their radioactivity and chemistry. Great care is needed to contain these wastes, particularly to avoid spills of contaminated water.

There are no commercial uranium mining or milling operations in the UK, and no wastes from uranium mining or milling are produced here.

Image: The tank farm at the White Mesa Hill uranium mine and mill in the USA. Source www.energyfuels.com


FACTSHEET:

Uranium enrichment and fuel manufacture

Overview

The uranium oxide powder produced from overseas mining and milling is called yellowcake. Yellowcake must be processed further before it can be used as a nuclear fuel. The two main steps in this process are uranium enrichment and fuel manufacture.

Uranium enrichment involves taking natural uranium and increasing the concentration of uranium-235 isotope, which is the essential component of nuclear fuel. This is usually done in a centrifuge to separate uranium-235 from the heavier and more abundant and heavier uranium-238 isotope.

Fuel manufacture involves taking the enriched uranium and turning it into a solid fuel pellet form. Many pellets are then encased (clad) within individual metal fuel rods. Multiple fuel rods are arranged into complete fuel assemblies that can be used in nuclear power reactors.

Uranium enrichment and fuel manufacture produces some operational wastes but not in large amounts. These typically include storage containers, used protective clothing and cleaning materials, and equipment components replaced during maintenance.

Enrichment does produce large amounts of a by-product material, known as depleted uranium. This is not considered as a waste because of its potential energy value and also because it has a number of industrial and defence uses.

Yellowcake – the raw material for nuclear fuel

The uranium oxide powder produced from overseas uranium mining and milling is called yellowcake. Yellowcake must be processed further before it can be used as a nuclear fuel. The two main steps in this process are uranium enrichment and fuel manufacture.

Image: Yellowcake is the raw material for manufacturing nuclear fuel. Source Uranium Energy Corp, US


Uranium enrichment

Yellowcake is a uranium oxide which contains uranium isotopes in their natural proportions. The majority is uranium-238 (more than 99%) with the remainder being uranium-235 (about 0.7%) and uranium-234 (less than 0.1%).

The uranium-235 isotope is needed to power a nuclear reactor. However, the small amount of this isotope that occurs naturally is not sufficient to sustain a nuclear chain reaction. This means it has to be concentrated (‘enriched’) before the fuel can be manufactured.

Most commercial nuclear power reactors require low enriched uranium (LEU) fuel with a uranium-235 content of between 3 to 5% to operate efficiently. Submarine reactors and nuclear weapons require more highly enriched uranium (HEU) with a uranium-235 content greater than 20%.

Separating isotopes

It is not possible to separate isotopes of the same element using chemical processes because they all have the same chemical properties. Separation of uranium-235 can only be achieved by taking advantage of the small mass difference between it and the slightly heavier uranium-238 isotope. The main method used to enrich uranium-235 is the gas centrifuge.

Converting to a gas

To form a gas suitable for centrifuging, the uranium oxide is converted to uranium hexafluoride (UF6) which is commonly referred to as ‘hex’. This is done using a complex multi-stage wet process.

The hex is a white crystalline solid at normal temperatures and pressures, but readily forms a gas at about 60°C.

At the enrichment plant, UF6 is heated and the gas produced is then fed into a centrifuge to be enriched.

Gas centrifuge

A gas centrifuge is used to enrich the uranium-235 isotope needed in nuclear fuel. A centrifuge is a machine with a cylinder which rotates rapidly separating the contents based on their mass.

The UF6 gas is fed into a centrifuge where it is spun rapidly at over 50,000 revolutions per minute. This causes the heavier uranium-238 to become concentrated towards the outer part of the cylinder and the uranium-235 to be concentrated towards the centre.

Separation of isotopes by gas centrifuge is not total, and so the slightly enriched gas from one cylinder is fed into another, along a cascade, in a continuous process. At the same time, the slightly depleted gases are fed back to the beginning of the cascade to be centrifuged again.


Fuel manufacture

The enriched UF6 ‘hex’ extracted from the gas centrifuge is converted back to a solid uranium oxide (UO2) in a high temperature kiln, together with steam and hydrogen.

This process produces a ceramic powder which is then ground to ensure evenly sized granules. This powder is then fed into dies, compressed and heated in a furnace to form the solid ceramic fuel pellets used in most nuclear power reactors.

Most fuel pellets are around one centimetre diameter, and many pellets are encased (clad) within individual metal fuel rods. Multiple fuel rods are arranged into complete fuel assemblies.

Different reactor types each require a different fuel assembly design.

All of the advanced gas cooled reactors (AGR) and the Sizewell B pressurised water reactor (PWR) currently operating in the UK use uranium oxide (UO2) fuel.

The older Magnox reactors used a special type of fuel made of natural uranium metal but these reactors have now reached or are reaching the end of their operational lifetimes. No new metal fuel is required.

Mixed oxide (MOX) fuel

MOX fuel combines uranium with plutonium that is recovered during the reprocessing of spent (used) fuel. MOX fuel used to be manufactured at Sellafield for overseas customers but this operation has now stopped.

No UK reactors use MOX fuel. However it may be used in the future, depending on commercial decisions on new reactor designs and their operation.

Radioactive wastes produced by enrichment and fuel manufacture

Uranium enrichment and fuel fabrication produce small amounts of LLW and ILW, such as:

• used ‘hex’ storage and transport containers

• solid waste ‘cake’ made largely of silica and produced during the purification of yellowcake

• typical operating wastes such as ion-exchange resins, paper and filters

Depleted uranium

The uranium enrichment process produces very large volumes of depleted UF6 ‘tails’ as a by-product (containing about 0.25% uranium-235). These ‘tails’ are drawn from the gas centrifuges after the enriched UF6 has been obtained, and then solidified.

These depleted tails are not considered to be a waste because of their potential energy value due to the remaining uranium-235, and because they have other possible uses.

They may be re-enriched or converted to depleted uranium (DU) metal. DU metal is very dense and has many industrial and defence uses, such as in bullets and trim weights in commercial airplanes.


FACTSHEET:

Operating a nuclear power reactor

Overview

Three different types of nuclear power reactors have operated commercially in the UK – the first generation Magnox reactors, the second generation Advanced Gas Cooled Reactors and one Pressurised Water Reactor.

Nuclear power reactors generate thermal (heat) energy by nuclear fission. This is the splitting of an unstable heavy nucleus into two smaller ones, with the release of energy. In a power reactor, the fuel is the radioactive isotope uranium-235.

To maintain the power efficiency of a reactor, some of the spent (used) fuel is periodically removed from the reactor and replaced with fresh fuel. On average, about one-third of the fuel is replaced every 12 to 18 months but this depends on the design of the reactor and how long the reactor has been running.

Routine operation of a nuclear power reactor does not produce a lot of radioactive waste. The main operational wastes are used clothing and cleaning materials, components replaced during maintenance, and ion-exchange resins used to extract radioactive and chemical contamination from liquids, such as the cooling pond waters.

Types of nuclear power reactors

Three different types of nuclear power reactors have operated commercially in the UK:

• the first generation Magnox reactors, located at 11 sites in the UK. These reactors use uranium metal fuel contained in a ‘magnesium non-oxidising’ alloy sleeve, which gave the reactors their name. The first Magnox reactor was located at Calder Hall in Cumbria, and began generating electricity in 1956. All but one of these reactors are now closed and are being prepared for decommissioning. The last operating Magnox reactor, at Wylfa in Wales, is scheduled to close in 2015

• the second generation Advanced Gas Cooled Reactors (AGR), located at 8 sites in the UK. These reactors use an enriched uranium oxide fuel. The first AGR began generating electricity in 1976, and all of these reactors remain operational

• one Pressurised Water Reactor (PWR) at Sizewell in Suffolk that also uses an enriched uranium oxide fuel. This reactor began generating electricity in 1995 and remains operational

Government has stated that nuclear power is and will continue to be a key part of the UK’s low-carbon energy mix*.

A series of new reactors have been proposed to help meet the UK’s future energy demands. The designs include PWRs and boiling water reactors (BWRs).

* BIS (2013), The UK’s Nuclear Future


Nuclear fission in a power reactor

All commercial nuclear power reactors generate thermal (heat) energy by nuclear fission. This is the splitting of an unstable heavy nucleus into two smaller ones, with the release of energy.

In a power reactor, the fuel is the radioactive isotope uranium-235. This isotope captures a free neutron to form the heavier uranium-236 isotope. The addition of an extra neutron into the nucleus makes this isotope unstable and so it spontaneously fissions (splits apart) into two smaller atoms, known as fission products, releasing further neutrons and heat energy. This is the essential process used to produce energy in a nuclear power reactor.

As well as generating heat energy, the fission process also releases other free neutrons. These neutrons can, in turn, be captured by other surrounding uranium-235 atoms. If there is a sufficient ‘critical mass’ of uranium, then a continuous chain reaction can begin.

To ensure the efficiency of the fission process, the free neutrons need to be slowed down to ensure they are captured by the uranium-235 atoms. This is done using a moderator material which is usually water or graphite, depending on the reactor design.

The fission reactions can be controlled or stopped altogether by inserting control rods into the reactor. These are made from materials that absorb neutrons without undergoing fission.

Plutonium can also be formed in nuclear fuel when uranium-238 captures a free neutron to form uranium-239. This uranium isotope then undergoes multiple decay steps to produce plutonium-239. This isotope is also radioactive but has a long half-life (approximately 24 thousand years) so it can accumulate in the nuclear fuel.

Image: The nuclear fission of the isotope uranium-235 initiated by the capture of a free neutron.

HeatEnergy

Nucleus

Uranium nucleus

Nucleus becomes

unstable and splits apart

(fission)

Fission products

Release of neutrons that go on to cause

further fission reactions


Anatomy of a nuclear power reactor

All nuclear power reactors aim to do the same thing - they use the heat generated from nuclear fission to create steam. This steam can then be used to drive turbines for electricity generation, in exactly the same way as other types of power station.

Although there are various different reactor designs, there are a number of common features. These are summarised below:

Fuel – The fuel contains the fissile material responsible for sustaining the nuclear fission chain reaction. Fuel types include uranium metal (Magnox reactors) or uranium oxide pellets (AGR and PWR reactors).

Fuel Cladding – The reactor fuel is contained within a cladding material. This protects the fuel and also contains the products of the fission reactions. The cladding material must be corrosion resistant and must not absorb neutrons. Cladding material types include magnesium alloy in Magnox reactors, stainless steel in AGRs and zirconium alloy in PWRs.

Moderator – The moderator slows down neutrons so that the uranium atoms can readily absorb the neutrons required for fission. The moderator must slow down the neutrons, but not absorb the neutrons itself. A typical moderator is graphite.

Coolant – The coolant draws heat away from the central part of the reactor (the reactor core) and takes it to the heat exchanger, where steam can be generated in a separate, secondary circuit. The coolant must be easy to pump, have good heat transfer properties and be non-corrosive. The coolant must not absorb neutrons. Typical coolants include carbon dioxide (gas), water, molten metal or molten salts.

Control mechanisms – The chain reaction is controlled by using materials that absorb neutrons. Typically, these materials are in the form of control rods, which can be moved in and out of the reactor core as required. Example control rod materials include cadmium, hafnium, boron and gadolinium. In some reactor designs, neutron absorbers, such as boric acid, can also be added to the coolant.

The reactor core is contained within a highly-engineered reactor pressure vessel (RPV).

The coolant used to remove heat directly from the reactor core is contained within a sealed ‘primary coolant circuit’. Heat is extracted from the primary coolant circuit using a heat exchanger, which allows the transfer of heat to a separate, secondary circuit containing water. As the water in the secondary circuit heats up, it turns to steam, which is then used to spin a turbine connected to a generator for electricity.

After the steam in the secondary circuit has passed through the turbine, it must be cooled again (condensed) so that the water can be reused. To do this, a separate cooling circuit and second heat exchanger is used.

Water used for cooling the steam in the second heat exchanger can be drawn from a local river, lake or the sea. This water is never in contact with radioactive materials and can be discharged back to the environment afterwards. An important aspect of the design of nuclear power reactors is ensuring that the primary, secondary and cooling water circuits are all separate from each other, to prevent radioactive materials from escaping the reactor core.

Control Rods

ReactorVessel

Pump

Reactor

Containment StructureSteam Line

Pump

SteamGenerator

Cooling Tower

CondensorCoolingWater

Turbine

Generator


Operation of a power reactor

The normal operation of a commercial power reactor involves a number of activities and processes that lead to wastes being produced. These activities include wastes from reactor maintenance, refuelling, and the storage and transport of spent fuel.

Routine liquid and gaseous discharges must be authorised by the environmental regulators and be strictly controlled and monitored.

Reactor maintenance

Routine maintenance and refurbishment is undertaken periodically to replace used reactor core components at the end of their operational lives. These activities lead to the production of wastes, including items such as used control rods, control rod chains and monitoring equipment.

Refuelling

Periodically, the spent (used) fuel assemblies are removed from the reactor core and replaced with fresh fuel. Typically, approximately one third of the fuel is re-placed every second or third year, but this depends on a wide range of factors, including the reactor type, its operating time and efficiency. Most reactors need to be shut down whilst refuelling takes place.

Image: The refuelling machine at the Wylfa Magnox reactor.


Storage of spent fuel

Spent fuel assemblies removed from the reactor core are placed in water filled cooling ponds for a minimum of 90 days. This allows any short-lived radioactivity to decay and the spent fuel to cool. Some corrosion of the metallic parts of the fuel assemblies can occur, leading to a build-up of sludge in the cooling pond.

The water in the ponds is actively circulated and cooled through heat exchangers. This water is also routinely filtered (through sand) and decontaminated through ion-exchange resins.

Transport of spent fuel

After it has cooled, spent fuel that is intended to be reprocessed is packed into special shielded flasks for transport to Sellafield.

The flasks are packed into specially designed transport containers. These containers are extremely strong and have thick lead and steel walls to shield the spent fuel, protecting workers and the public from radiation.

A transport container can be used for multiple journeys and is monitored and decontaminated between journeys to maintain safety.

Image left: A cooling pond for spent fuel at Sellafield.Image above: Transport of spent fuel by rail.


Radioactive wastes produced during power reactor operations

A broad range of wastes and materials are produced during normal operation of a power reactor and associated spent fuel cooling ponds, although the quantities are small compared to reactor decommissioning wastes.

Fuel element debris (FED) is produced when fuel is handled at the reactors. This is mostly Magnox metal, stainless steel, other alloys and some graphite.

Miscellaneous activated components (MAC) are produced during routine maintenance work. These are highly radioactive, usually metallic items.

Contaminated liquid wastes and sludges are also produced during normal operations. Magnox metal corrodes in water, and its corrosion products and sludge accumulate in the bottom of cooling ponds.

Spent ion exchange resins and sand filters used to clean cooling pond and other waters on site are routinely produced, as are filters used to clean gaseous discharges. Used protective clothing and equipment are also routinely produced as LLW.

The spent fuel removed during refuelling is not considered to be a waste because it has the potential to be reused in future. After cooling, some spent fuel is transferred to Sellafield for storage or to be reprocessed to recover uranium and plutonium that can be reused to manufacture new fuel.


FACTSHEET:


Overview

In the UK, all of the commercial nuclear power reactors use uranium as fuel. The isotope uranium-235 is necessary for sustaining the nuclear fission chain reaction, which generates the heat needed to power the electrical generators.

Over time, the amount of uranium-235 in the fuel decreases as it is gradually used up in the fission reactions and is converted to other fission product isotopes. This reduces the efficiency of the reactor.

To maintain power output, some of the used fuel is periodically removed from the reactor and replaced with fresh fuel. This spent fuel still contains some uranium-235 and also plutonium that was created as a consequence of the nuclear reactions.

The spent fuel can be reprocessed to recover the remaining uranium and the plutonium. These can then used to manufacture new nuclear fuel.

Reprocessing is a complex process that is undertaken on an industrial scale at the Sellafield site in Cumbria. It involves dissolving the spent fuel and separating out the uranium and plutonium products from other elements that are not useful.

The process produces very highly radioactive wastes that contain most of the fission products. These are converted into a glass wasteform through a process called vitrification, and then stored until they can be finally disposed.

About reprocessing

Spent fuel from both Magnox and AGR reactors in the UK (and from some overseas reactors) is reprocessed at facilities in Sellafield. The processes used for managing both types of spent fuel are broadly similar, although there are some technical differences which are not detailed here.

Magnox fuel is a uranium metal. The use of reprocessing technology to manage Magnox spent fuel has been ongoing for over 50 years. Approximately 50,000 tonnes of Magnox spent fuel has been produced in this time. The Magnox reactors have now reached or are reaching the end of their operational lifetimes. When all have closed, no further spent fuel from Magnox facilities will be produced.

AGR and PWR fuel is uranium oxide (UO2). A large proportion of the spent AGR fuel produced has already been reprocessed in the industrial scale thermal oxide reprocessing plant (THORP).

Decisions made recently mean that no spent fuel will be reprocessed in existing facilities after 2020. The spent fuel that is not reprocessed will need to be stored until the disposal route becomes available. Work is underway to develop a Geological Disposal Facility (GDF) for higher activity wastes and spent fuel requiring disposal.


Stages in spent fuel reprocessing

There are a number of stages involved in spent fuel reprocessing.

Decanning and shearing

The first step of reprocessing is the removal of the metal fuel cladding, to leave just the spent fuel material. In the case of Magnox fuel, the decanning produces Magnox swarf (irradiated magnesium non-oxidising cladding material) which is a waste.

The dismantling of the AGR and other fuels is more complex. The fuel assemblies first need to be disassembled to remove any stainless steel and graphite components. The AGR fuel rods are then sheared into pieces.

Acid dissolution

After decanning, the separated spent fuel is dissolved in nitric acid to produce a radioactive solution containing the uranium, plutonium and fission products that were contained in the spent fuel.

The nitric acid does not dissolve any remaining metallic components, so some insoluble solid items, such as the fuel cladding, and particulate fines are separated and treated as waste.

Image: Aerial image of Sellafield site where spent fuel reprocessing occurs


Uranium and plutonium extraction

The uranium and plutonium in solution needs to be extracted and separated from the remaining and unwanted fission products. This is done using a sequence of chemical extractions in a process known as PUREX (Plutonium Uranium Redox Extraction).

The extraction process takes advantage of the natural affinity of uranium and plutonium to associate with organic materials.

In the first step, the organic, oily liquids kerosene and tri-butyl phosphate (TBP) are added to the acidic solution, and intensively mixed. During mixing, the uranium and plutonium becomes concentrated in the organic liquid phase, and the fission products remain in the acidic solution.

When mixing stops, the organic liquid and the acidic solution naturally separate out from each other due to their different physical properties. Almost all of the fission products remain in the aqueous acidic phase which is drawn off as a separate liquid waste stream. This liquid waste (known as a raffinate) is highly radioactive.

A chemical reducing agent is then progressively added to the remaining organic solution which causes the plutonium and uranium to separate. Finally, the separated liquid uranium and plutonium product streams are solidified for safe storage.

Image: Diagram illustrative the PUREX process. Source - European Nuclear Society

Organic liquids Dissolved fuel

Intensive Mixing

Liquids separate out

Highly radioactive raffinate waste

Liquid containing uranium and plutonium


Vitrification of the liquid waste

The highly radioactive liquid waste (raffinate), which contains the fission products, has no further use and so is classified as a waste. This liquid is converted to a stable solid for safe storage, in a process called vitrificaton.

The liquid raffinate is first concentrated in an evaporator and then dried to granules in furnace known as a calciner. The granules are mixed with borosilicate glass particles and melted in a metallic container.

In the molten state, the waste becomes intimately mixed with the borosilicate glass, and is then poured into a stainless steel container and left to cool and solidify. Once cooled, a stainless steel lid is welded on to the top of the container.

Borosilicate glass is used to solidify the raffinate because it is a corrosion resistant material suitable for final disposal in a geological repository. The resulting glass is robust and heat resistant.

The filled containers are stored on site at Sellafield until a Geological Disposal Facility (GDF) becomes available.

Image: The continuous vitrification process used to solidify the highly radioactive liquid wastes from reprocessing

Highly radioactive raffinate

MELTER

Waste cools and solidifies to form a

glass in the container

Glass forming materials are

added

STAINLESS STEEL

CONTAINER


Radioactive wastes produced during spent fuel reprocessing

Radioactive wastes are produced at each stage in spent fuel reprocessing.

At the earliest stage in the cooling ponds, corrosion of the fuel assemblies can cause the build up of sludge and metal items which require management. The treatment of cooling pond water also leads to contaminated ion exchange resins that are classed as ILW.

The metallic parts of the fuel assemblies are separated from the spent fuel itself during decanning and shearing. These metal parts are ILW.

When dissolved in acid, any remaining residues from the dissolution process will be wastes, such as sludges and remaining metallic components.

Highly radioactive liquid waste (raffinate) produced during spent fuel reprocessing is converted into a solid form in a process called vitrification. The vitrified waste contains all the fission products from the spent fuel and therefore contains most of the radioactivity.

The gases from vitirification facilities are treated using a series of scrubbers and absorbers before they can be safely discharged to the atmosphere.

Some operational LLW is also produced during spent fuel reprocessing, including redundant equipment, used tools and protective clothing.

Image: Stainless steel containers for the storage of vitrified waste.


FACTSHEET:

Decommissioning of nuclear power facilities

Overview

All nuclear reactors and other types of nuclear facilities need to be decommissioned when they reach the end of their operational life. This involves the decontamination and full or partial dismantling of buildings and their contents to achieve an agreed site end state.

Once a facility has been shut down, there is a transition phase during which the facility is prepared for decommissioning. This includes removing any fuel and other readily accessible radioactive materials and contaminated equipment. Liquids are drained from pipes and tanks, which are also removed.

Following this transition phase, facilities are decontaminated, which means removing radioactive contamination which may be on surfaces. This makes the later stages of decommissioning easier and reduces the total volume of radioactive waste arising.

After a nuclear facility has been decontaminated, it can be dismantled and, depending on the proposed end state, demolished.

Remediation may also be required to manage any areas of contaminated soil or groundwater. This ensures the protection of people and the environment during the next use of the site.

Decommissioning may be carried out immediately following permanent shutdown and transition or may be deferred for a predetermined period.

Decommissioning produces large volumes of material, including concrete, brick, steel and soils. Much of this material is non-radioactive and can be managed in the same way as conventional demolition waste.

Responsibility for decommissioning

All nuclear reactors and other types of nuclear facilities need to be decommissioned when they reach the end of their operational life. This involves the decontamination and full or partial dismantling of buildings and their contents to achieve an agreed site end state.

The NDA has been established to manage the decommissioning of the UK’s civil nuclear legacy. This legacy includes a wide range of facilities, such as reactors, chemical plants, research and development facilities, and waste processing and fuel fabrication plants.

Owners of the current fleet of commercial reactors and other nuclear facilities are responsible for making arrangements for decommissioning when their facilities reach the end of their operational life.

Hazard and risk reduction

Decommissioning activities are carried out to achieve a progressive and systematic reduction in risk to people and the environment resulting from radiological, chemical, biological and industrial hazards associated with a facility. Where the risks are ‘intolerable’, urgent action is taken to reduce these risks.

Undertaking decommissioning activities introduces conventional hazards, for example the use of cutting tools, which should be considered in decommissioning plans.


Decommissioning strategies

Decommissioning may be carried out immediately following permanent shutdown and transition, or may be deferred for a predetermined period. The deferral period can range from a few months to a number of decades depending on the size and complexity of the decommissioning project, and the purpose of deferral.

A deferred decommissioning strategy is typically selected to take benefit from radioactive decay of the shorter lived isotopes (reducing the radiation hazard and the activity inside the reactor itself) or to manage constraints such as the availability of waste management infrastructure or financial resources.

It is planned that most of the commercial power reactors in the UK will be managed using a deferred decommissioning strategy. Following transition, the reactors will be safely enclosed for several decades. This will allow radiation levels within the reactor to decay, and will give time for waste management infrastructure to be put in place.

Many other types of redundant nuclear facilities in the UK, such as research reactors and laboratories, are smaller and less complex and therefore decommissioning typically commences immediately after shutdown and transition.

Image: Magnox reactors on the Berkeley site in 2010 as they transition to Care and Maintenance under a deferred decommissioning strategy.


This diagram illustrates the general stages involved in decommissioning a nuclear site. The level of work involved in each stage and the order of work is dependent upon the nature of the site and the agreed Site End State. Not all steps will be involved for some sites, some activities may occur the same time and some steps may be repeated. Remediation is part of land quality management, along with other activities, such as the prevention of leaks and characterisation.

OperationTransition:

Preparation for Decommissioning

Decontamination & Dismantling

DemolitionRemediation (Ground &

Groundwater)Landscaping

Decommissioning

Deferred Decommissioning

- Preparing for Safe Enclosure

Deferred Decommissioning- Safe Enclosure

Site End State

This may involve the removal of

operational materials (e.g. spent

fuel) and wastes

Facility Shut Down

Stages in decommissioning

There are several stages involved in decommissioning a nuclear facility, depending on whether a continuous or deferred decommissioning strategy is followed. Most of these stages will result in some radioactive waste being produced.


Transition from operations to decommissioning

Defuelling is the first activity after the reactor is shut down. This involves the removal of all spent fuel from the reactor core, the cooling ponds and stores, which is then transferred for storage or reprocessing.

Defuelling of a commercial Magnox or AGR reactor will take about two years to complete because of the large number of fuel assemblies that need to be packaged and transferred. Completion of defuelling will remove around 99% of the radioactivity from a reactor site and so will greatly reduce the hazard.

Preparations for decommissioning also involve removing the vast majority of radioactive materials and sources that have been used during operations.

This typically involves draining all of the liquids from tanks and pipework, and removing all accessible and non-fixed radioactive sources, contaminated components and materials. By their nature, the wastes arising from the transition phase are similar to those that arise during normal reactor operations.

Image: A reactor may contain over 50,000 fuel assemblies that all need to be removed from the site during defuelling. These will be transported in special containers like the one shown here.


Preparations for safe enclosure

If a decision is taken to defer decommissioning then preparations may be required according to the period of deferral. This may include the removal of equipment and large components, such as boilers and steam generators. These large components may be sent off site to specialist facilities for decontamination, allowing the clean steel to be recycled.

In the case of a power reactor, the pressure vessel and the main containment structures are kept intact during safe enclosure. Therefore, as part of preparations, the structures may need to be sealed and the atmosphere controlled.

Ancillary buildings outside of the main facility, such as offices, stores, laboratories, turbine halls and cooling towers, may be decontaminated, if required, and demolished during this stage. Conversely, other facilities may be built such as waste stores that will contain the wastes until the site is finally cleared.

Safe enclosure

The safe enclosure or deferral period may last many decades. For many of the UK power reactors, this period is also known as the period of Care and Maintenance.

During the period of safe enclosure, typically the key activities that will take place are monitoring and any essential maintenance work to provide assurance that the enclosure remains safe. Another essential element of the safe enclosure period is the maintenance of records that describe the status of the enclosed facility and the proposed decommissioning plan such that decommissioning can recommence efficiently and effectively. It may also be necessary to control access to the site.

Few radioactive wastes will be produced during the safe enclosure period except for items that have been used for monitoring and maintenance in active areas.

Berkeley reactors enter care and maintenance

The Magnox reactors at the Berkeley site were the first in the UK to enter Care and Maintenance in December 2010. They will remain closed with only routine inspection, monitoring and maintenance work until 2074 when final dismantling is scheduled to begin.

Image: The sealing of the Magnox reactors on the Berkeley site in 2010 as they transition to Care and Maintenance under a deferred decommissioning strategy.


Decontamination and dismantling

Decontaminating a facility involves the complete or partial removal of radioactive substances or material from surfaces or from within a system or item. This reduces the magnitude of radioactivity within a facility which may facilitate decommissioning (e.g. allowing man access for further dismantling), reduce the period required before dismantling, minimise the volume of radioactive waste arising, and increase the potential for recycling and reusing components.

Simple washing and mechanical cleaning techniques are often sufficient to decontaminate surfaces. They are likely to generate secondary wastes (e.g. washing water) that will need to be managed.

Dismantling is carried out to reduce the size of components so that they can be removed more easily and placed in waste containers. There are a range of different techniques used for dismantling from mechanical cutting techniques such as shears and saws to thermal cutting techniques using torches and lasers. These can be operated manually or remotely using robotic systems to minimise the exposure of workers to radiation.

Demolition and final site remediation to achieve agreed end stateAfter dismantling the internal structures, systems and components within a facility, the building may be demolished unless the end state allows for its reuse. Demolition involves conventional demolition techniques.

Depending on the next use of the site, further work may be required to remediate any ground and groundwater contamination. This may involve:

• removing contaminated soil or buried structures, such as foundations and pipework

• breaking the pathway between contamination and sensitive receptors for example using physical barriers, or

• using the process of ‘monitored natural attenuation’ to monitor the natural degradation of contaminants over time

As with the decommissioning of conventional industrial sites, it may also be appropriate to use institutional controls, such as land use restrictions, to manage risks to people and the environment from residual contamination.


Site End States

Every NDA site has an agreed Site End State. The Site End State sets out the high-level remediation objectives for the site, considering the land’s next planned use or probable future uses.

For many NDA sites, the Site End State is not scheduled to be achieved for many decades, so it is important to ensure that there is flexibility in the long term site decommissioning and remediation plans.

A wide range of issues could affect the proposed Site End State, such as changes in policy and regulations, advances in technology and changes in the desires of a community through generations.

It may not be realistic or even necessary to remediate a site to its natural pre-industrial condition. Therefore, for some sites, remediation work will focus on preparing the site for future industrial uses.

Radioactive wastes produced during decommissioning

The majority of radioactive waste produced in the UK arises from later stage decommissioning activities, where large building structures are dismantled and demolished, and land is remediated.

The greatest amount of radioactivity is associated with the spent fuel that is removed from a power reactor site during defuelling operations. This spent fuel is not considered to be a waste, as it has the potential to be reprocessed to recover uranium and plutonium that can be reused in new fuel manufacture.

ILW will be produced during the transition and dismantling stages. These are typically in the form of liquids and sludges, and wet materials such as ion-exchange resins (used to remove contamination from liquids). These wastes will usually be mixed with cement to make a solid material, and will be stored on the site until a disposal route is available.

The metallic reactor components will be very radioactive when the facility is first shut down but the majority of the radioactivity will come from radionuclides in steel that have relatively short half-lives.

In the UK, radioactive wastes are categorised by their radioactivity content. Allowing for radioactive decay during a period of safe enclosure may mean that some of the steel from decommissioned reactors can be disposed as LLW rather than ILW.

Large volumes of material will be produced when the buildings are finally demolished and the site remediated. This will be in the form of building rubble, concrete, soil and steel items. Most of this demolition material is not radioactive and so can be managed in the same way as conventional demolition rubble, and may be reused or recycled.

Some of the demolition material will be contaminated with low levels of radioactivity, and will be treated and disposed as LLW or VLLW.

Current Site Use/State

Site End State

Site End Use

Image: A representation of a site’s progress from current use, to site end state and then to its next planned use.


FACTSHEET:

Wastes from defence activities

Overview

Defence activities produce radioactive wastes that are broadly similar in type to those from civilian nuclear power production. The total amount of waste produced is, however, much less.

The largest volumes of radioactive waste arise within the Royal Navy during operation, maintenance and decommissioning of nuclear powered submarines.

Other radioactive wastes are produced during activities to maintain the UK’s strategic nuclear weapons capability, and from clean-up of disused military sites.

Submarine operation

All of the current fleet of Royal Navy submarines are powered by pressurised water nuclear reactors (PWRs). These reactors work in much the same way as a civil nuclear power reactor, but on a smaller scale and using more highly enriched nuclear fuel. These differences are reflected in the wastes that are produced.

Radioactive wastes are produced during normal operations. These include items such as used protective clothing, ion exchange resins used to decontaminate liquids and redundant equipment.

Additional wastes are produced during the periodic refit of the submarines and refuelling of the reactors.

Image: The nuclear-powered submarine HMS Vengeance at Devonport dockyard during a periodic refit and refuelling operation. Source - Ministry of Defence


Submarine decommissioning

Once a submarine has reached the end of its operational lifespan it will need to be decommissioned.

Decommissioning is undertaken in stages, with the first stage being defuelling. Spent fuel from submarines is removed and sent to Sellafield where it is stored in a cooling pond for several years.

The reactor compartments are the only part of the submarine structure to contain radioactive materials. During operations, the metallic parts of the reactor compartment will become radioactive due to neutron activation.

Out of service nuclear powered submarines are kept at the naval dockyards at Rosyth in Fife and Devonport near Plymouth. It is proposed that these submarines will be dismantled and the reactor compartments will be disposed as radioactive waste.

Nuclear deterrent

The manufacture and maintenance of new nuclear weapons and the dismantling of old, redundant ones produces some radioactive wastes.

Some of these wastes are broadly equivalent to the radioactive wastes produced within civilian nuclear operations, but in smaller amounts.

Clean-up of disused military sites

Many old military sites are no longer needed, and so are being cleaned-up so that they can be made available for other uses. Some of these sites are contaminated with radioactive substances, such as radium that was used on luminous dials in aeroplane cockpits. Clean-up of these sites can produce wastes such as contaminated soils.

Radioactive wastes produced by defence activities

Many different radioactive wastes are produced from manufacturing, maintenance, operation and decommissioning of nuclear submarines and nuclear weapons. Examples include:

• used filters and resins from submarine reactor operations, decontamination of pond water and liquid treatment

• metallic reactor components from development, testing and decommissioning submarine reactors

• depleted uranium ammunitions, contaminated targets and ground from weapons testing

• contaminated land from the clean-up of disused military sites to make them available for reuse


FACTSHEET:

Wastes from research activities

Overview

A wide range of research activities have been undertaken in the UK, which have led to the production of radioactive wastes. Research activities have benefited the nuclear, defence, medical and industrial sectors.

Research into commercial nuclear fission

In the early days of the nuclear industry in the 1940s until the 1980s, there was a large Government funded research programme into nuclear fission reactor technology.

Many different reactor designs and fuel types were investigated. That research programme led to the successful development of the early Magnox reactors and the later Advanced Gas Cooled Reactors (AGR) that have been built and operated commercially in the UK.

Experimental fission reactors

During the research programme, 19 test and prototype fission reactors, both large and small, were operated at the research sites of Harwell, Winfrith, Windscale and Dounreay. These include the Graphite Low Energy Experimental Pile (GLEEP) reactor at Harwell, which was built in 1946 and was the very first nuclear reactor in Europe.

These experimental reactors were supported by an array of laboratories and facilities for material testing, and for fuel manufacture, analysis and reprocessing.

During their operation, a wide range of irradiated fuel materials were produced, together with many different types of solid and liquid wastes.

These experimental reactors and associated facilities have now all shut down and are being decommissioned, or have already been decommissioned.


The Dounreay fast reactors

The Dounreay site in the north of Scotland was home to research on fast breeder reactor technology.

These fast reactors differ from conventional thermal reactors in a number of ways. Most importantly they use high energy fast neutrons that interact with uranium to produce much more fissile material than they use. They effectively ‘breed’ new fuel as they operate. For this reason they are sometimes called ‘breeder’ reactors.

Two fast reactors were operated at Dounreay. The Dounreay Fast Reactor (DFR) which is housed in the famous ‘golf ball’ spherical dome and the Prototype Fast Reactor (PFR) that trialled full-scale power operations.

Fast reactor research has stopped in the UK, and both the DFR and PFR are now closed and are being decommissioned.

Due to their novel design and operations, a much more diverse range of solid and liquid wastes come from DFR and PFR than from commercial Magnox or AGR reactors.

Image: Fast reactor at Dounreay


Research into nuclear fusion

In the UK, research into nuclear fusion is being conducted at the Joint European Torus (JET) facility at Culham, which is currently the largest facility of its kind in the world.

A fusion reactor does not use conventional nuclear fuel. Instead energy is generated through the fusion of radioactive hydrogen isotopes (deuterium and tritium). Radioactive wastes produced during operation and future decommissioning of JET will be contaminated by tritium.

Other civilian nuclear research

Academic and industrial research and development work takes place in many universities and research establishments across the UK.

The scope of research is very wide, and includes work to address challenges across the nuclear, industrial and medical sectors. Examples include research into new radiotherapy treatments and work to test novel techniques for encapsulating liquid radioactive wastes.

Radioactive wastes produced by research activities

Many different radioactive waste types have been produced during operation of the experimental nuclear power reactors and their associated research facilities.

Many of these wastes are unique and are not found at other nuclear sites. Examples include:

• novel irradiated fuels, and high active liquid and solid wastes from their testing and reprocessing

• sodium metal coolants used in the Dounreay fast reactors and contaminated coolant circuits

• mixed wastes that are due to be recovered from old disposals in a deep rock shaft at Dounreay

A wide range of different radioactive wastes are produced from other research activities, although the quantity of waste generated by these activities is relatively small.

Image: The inside of the JET fusion facility. Source: www.ccfe.ac.uk/images.aspx


FACTSHEET:

Wastes from medical activities

Overview


The amount of radioactive waste produced by the medical industry is small. This waste is generated primarily from the manufacture, use and disposal of radioactive sources and radiopharmaceuticals.

Use of radioactive materials


Some medical diagnosis and treatment processes involve the use of radioactive sources, which are sealed within metal containers. The source then releases a controlled amount of radiation through a small window in the container. This beam of radiation can then be directed at a specified area for diagnosis or treatment purposes.

The extent to which the radiation penetrates the body varies and is affected by the radiation type, the energy of the radiation and the density of the material the radiation is travelling through.

Rapidly dividing cells are particularly sensitive to damage by radiation. For this reason, some cancerous growths can be controlled or eliminated by irradiating the area, either through external radiotheraphy (directing a beam of radiation at the affected area) or through the use of radiopharmaceuticals. Radiopharmaceuticals are drugs that contain radioactive materials.

Radiopharmaceuticals are chemicals that contain radioactive isotopes. They can be injected into the body, inhaled or ingested for both diagnosis and treatment purposes. These substances can be easily detected and tracked until they disappear leaving no trace.

Different chemicals can be absorbed preferentially by different organs in the body. Taking advantage of this, radiopharmaceuticals can be used to assess the condition of particular organs. In diagnostics, the amount of radioisotope added to the body is very small, just enough to obtain the required information before the isotope decays.

Radioactive sources and radiopharmaceuticals are manufactured by commercial companies at specialist facilities in the UK and overseas. Many thousands of radioactive sources are in use in UK hospitals.

Image: Manufacturing radiopharmaceuticals. Source: www.comecer.com


Radioactive wastes produced by medical activities

Many different radioactive wastes are produced by medical activities, although usually in relatively small volumes. These include:

• used sealed sources from hospitals

• contaminated laboratory equipment and materials

• other solid wastes such as swabs, vials, syringes, gloves and dressings

• liquid wastes, such as mildly active washings from laundry treatment of protective clothing

• waste radiopharmaceuticals - radiopharmaceuticals often have short half lives and so need to be replaced at regular intervals

Radioactive waste from medical applications is typically categorised as LLW, and is often suitable for disposal through incineration at appropriately licensed facilities. Higher activity sealed sources are often returned to the manufacturer for recycling or disposal.


FACTSHEET:

Wastes from industrial activities

Overview

Radioactive materials are used in industry for a wide range of purposes. Radioactive materials are typically used for the sterilisation of equipment, to examine metal welds and joints, to gauge the thickness of items and in various devices, such as smoke detectors. They can also be used as tracers to assess the behaviour of liquid effluents.

Most of these processes use radioactive sources, which are sealed within metal containers. The source then releases a controlled amount radiation through a small window in the container. They may also use radioactive gases or liquids, contained within glass tubes.

In industry, the amount of radioactive waste produced is small. This waste is generated primarily from the manufacture and handling of radioactive sources and from the disposal of these sources after they have been used.

Use of radioactive materials in industry

Gamma sterilisation

Radioactive sources are used for the sterilisation of equipment in the medical industry, particularly for items that would be damaged by heat sterilisation, such as syringes, gloves, clothing and fine instruments.

The food industry also uses gamma sterilisation, extending the shelf life of products and reducing the risk of food-borne diseases.

Gamma radiography

Similar to X-rays, gamma sources are used to penetrate solid objects to show their internal structure. This is called gamma radiography and can be used as part of quality checks in construction and component manufacturing processes, highlighting any flaws in metal casting or welded joints. Different sources are used for different material thicknesses.

Gauging

Radioactive sources are routinely used to measure the thickness of materials. A radioactive source is directed at the material and a detector placed on the other side. The thickness of the material can then be determined by how much radiation passes through the item. This is a common technique used in the manufacture of items such as plastic film and paper, to help with quality control assessments.


Smoke detectors

Many smoke detectors used in homes and offices are Ionisation Chamber Smoke Detectors (ICSDs). These devices contain a small ionisation chamber, in which the air between the electrodes is ionised by a radioactive source. A potential difference is applied between the electrodes, causing a small current to flow. If heavy smoke particles enter the detector, the flow of current reduces, triggering the alarm to sound.

The majority of modern ISCDs use the radioactive isotope americium-241. The amount of radioactive material used in these devices is very small and causes no danger to people. Smoke alarms can be safely disposed of with other household and office waste electrical items.

Tracers

Many different radioisotopes are used as tracers. The radioisotope used is selected on the basis that the half life is just long enough to obtain the required information and does not cause harm to people or the environment. An example is the tracing of sewage dispersion in sea outfalls and small leaks in fossil fuel power station heat exchangers.

Radioactive wastes produced by industrial activities

In industry, the amount of radioactive waste produced is small. This waste is generated primarily from the manufacture and use of radioactive sources and from the disposal of these sources after they have been used.

During the manufacture of radioactive sources, highly radioactive materials may need to be remotely handled and assembled in shielded glove boxes. Many thousands of sources can be manufactured in these glove boxes, leading to an accumulation of wastes contaminated by radioactivity, including equipment, metal shavings, glassware, rubber gloves and paper tissue.

Used sources are managed in a variety of ways. Lower activity redundant sources can often be safely incinerated. Higher activity sources are usually returned to the manufacturer for recycling or disposal.

Returned sources are often sealed in small steel cans, grouted into drums and stored as radioactive waste. This can present a challenge for managing the redundant sources, because grouping sources together could lead to high levels of radioactivity.

Some liquid radioactive wastes are also produced in industry, including mildly active wastes from washing protective clothing.


Glossary and definitions

Advanced gas cooled reactor (AGR): A second generation power reactor that uses a uranium oxide fuel and is cooled by gas.

Atom: An atom is the basic building block of matter. An atom is made from a nucleus surrounded by electrons. The nucleus contains particles called protons and neutrons.

Care and maintenance (C&M): Most of the commercial power reactors in the UK will be managed using a deferred decommissioning strategy. This means that the reactors will be safely enclosed for several decades, allowing radiation levels within the reactor to decay before further decommissioning activities take place. In the UK, some sites refer to this period of safe enclosure as ‘Care and Maintenance’.

Centrifuge: A very fast spinning cylinder that is used to separate the isotope needed in nuclear fuel, uranium-235, from the slightly heavier isotope uranium-238.

Characterisation: The process of assessing the composition of radioactive materials and wastes, and classifying them based on their levels of radioactivity, and physical and chemical properties.

Contamination: Radioactive particles that have accumulated on an exposed surface by contact with a radioactive material or waste.

Conversion: Changing one substance into another using a chemical processes. For example, the conversion of uranium oxide (U3O8) into uranium hexafluoride (UF6) during the manufacture of nuclear fuel.

Cooling pond: A large, water-filled tank used to store and cool spent fuel after it has been removed from a reactor, allowing radioactive decay to reduce the amount of heat emitted by the fuel.

Decontamination: Removing or reducing the radioactive or chemical contamination on materials or items. This may be done using chemical methods to wash off or dissolve contamination, or physical methods such as grinding to remove contaminated material on solid surfaces.

Decommissioning: The activities undertaken at the end of the life of a nuclear facility to decontaminate, dismantle and demolish it.

Defuelling: Removal of all nuclear fuel from a reactor at the end of the reactor’s operational life.

Demolition: Standard methods for knocking down the shell of a building after any internal components or materials that need to be dismantled have been taken out.

Depleted uranium (DU): Uranium containing less than the natural amount of the uranium-235 isotope. This is produced as a by-product from enrichment during the manufacture of nuclear fuel.

Dismantling: Taking apart a facility in a carefully controlled manner. This allows each part of the facility to be handled separately and different materials to be segregated (e.g. to separate contaminated from uncontaminated materials).

Enrichment: The process of increasing the concentration of the uranium-235 isotope using a centrifuge during the manufacture of nuclear fuel.

Environment agencies: The Government bodies responsible for protecting the environment, and for controlling radioactive waste disposal and discharges from nuclear sites. There are separate environment agencies in England, Scotland, Wales and Northern Ireland.

Fission: The splitting apart of heavy atoms in a nuclear reactor to produce smaller atoms and release energy.

Fission products: The smaller atoms produced during the fission process. These are often highly radioactive.

Fuel element debris (FED): Waste material made up of metal components from the cladding of nuclear fuel rods, after their use.

Fusion: A process in which two or more light atoms are formed into a heavier atom, releasing large amounts of energy. This is essentially the same process that occurs in the Sun.


Geological disposal: A long term management option which involves disposing radioactive waste deep underground in a highly-engineered Geological Disposal Facility (GDF).

Hazard: Anything that has the potential to cause harm to people or the environment.

Hex: Uranium hexafluoride, which is a gaseous compound into which solid uranium is converted before it can be enriched in a centrifuge.

High level radioactive waste (HLW): Radioactive wastes that have such a high radioactivity content that they generate heat. This waste is produced at Sellafield as a by-product from the reprocessing of spent nuclear fuel.

Incineration: A waste treatment process where combustible material is burnt. The products are ash, flue gas and heat. The result is a significantly reduced volume of waste.

Intermediate level radioactive wastes (ILW): Radioactive wastes with a radioactivity content above the limit for LLW but are not heat generating. ILW is produced during normal operations, maintenance and decommissioning activities at nuclear facilities, and also by reprocessing of spent nuclear fuel.

Isotope: Atoms of the same element which have the same number of protons but different number of neutrons. Two common isotopes of uranium include uranium-235 and uranium -238, both have 92 protons in their nucleus but different numbers of neutrons.

Low level radioactive waste (LLW): Radioactive wastes which are not suitable for disposal as ordinary wastes, but only have low levels of radioactivity.

Low level waste repository (LLWR): The facility in Cumbria used for the disposal of LLW.

Magnox: A type of reactor that uses uranium metal fuel. Named after the magnesium non-oxidising alloy sleeve used to contain the fuel.

Milling: The process for extracting uranium-rich minerals from ore.

Miscellaneous activated components (MAC): A variety of waste materials, typically small in size, that have been irradiated during normal reactor operations.

Mixed oxide fuel (MOX): A nuclear fuel that combines a mixture of uranium and plutonium oxides.

Neutron activation: The capture of a free neutron by a stable non-radioactive atom, causing it to become radioactive.

Nuclear fuel cycle: The sequence of activities involved in the production and use of nuclear fuel. It begins with mining uranium ore and involves fuel manufacturing, using fuel in a power reactor, and the management of the spent nuclear fuel afterwards.

Nuclear power reactor: A purpose built power station that uses nuclear fuel to produce heat and to generate electricity.

Naturally-occurring radioactive material (NORM): Natural radioactive materials that are found in the environment. NORM can become concentrated during processes used in the oil, gas and mining industries, leading to NORM wastes.

Post-operational clean-out (POCO): The removal of all accessible radioactive sources and forms of contamination in a nuclear facility at the start of decommissioning.

Primary circuit: The part of a nuclear power reactor that transfers heat from the core to the heat exchangers, where the secondary circuit takes over and drives turbines to generate electricity.

Pressurised water reactor (PWR): A type of nuclear power reactor that uses water under pressure as its primary coolant.

Plutonium (Pu): A heavy, radioactive element that is produced in nuclear fuel as a result of the nuclear fission process.

Plutonium uranium redox extraction (PUREX): A chemical method used in the reprocessing of spent fuel to separate uranium and plutonium from unwanted fission products.


Personal protective equipment (PPE): Protective clothing, helmets, goggles, or other equipment designed to protect the wearer’s body from harm.

Radiation: The process of emitting (radiating) energy in the form of particles or electomagnetic waves.

Radioactive decay: The spontaneous disintegration (splitting apart) of an unstable nucleus, releasing energy in the form of particles (alpha and beta), neutrons or electromagnetic energy (gamma rays).

Radiopharmaceutical: Chemicals that contain specific radioactive isotopes and are used in medicine for the diagnosis and treatment of medical illnesses.

Raffinate: A liquid produced during the reprocessing of spent fuel that contains all the unwanted fission products. Raffinate is highly radioactive and is converted into a solid glass by vitrification for safe storage.

Radioactive waste: A waste material or item containing levels of radioactivity above limits that are defined in law or regulation, and so must be stored and disposed with appropriate prior approval.

Recycling: Processing a waste material to convert it into a useful product.

Reprocessing: A treatment process for spent nuclear fuel that recovers uranium and plutonium, which could be used in the manufacture new nuclear fuel.

Remediation (or restoration): Cleaning-up the land around a facility to remove or treat any areas of land contamination. This is often done after the buildings have been demolished.

Secondary circuit: The part of a nuclear power reactor that produces steam to drive the turbines and generate electricity.

Scabbling: Mechanical removal of the contaminated surface layer of a structure or building (a physical method of decontamination).

Spent (nuclear) fuel: Fuel that has been used in a nuclear reactor.

Swarf: Fragments of Magnox fuel cladding that are produced when the cladding is stripped and removed from the fuel during reprocessing.

Thermal oxide reprocessing plant (THORP): The facility on the Sellafield site used to reprocess spent oxide fuel from UK Advanced Gas Cooled Reactors and some overseas customers.

Tritium: A radioactive isotope of hydrogen containing two neutrons and one proton.

Uranium (U): A naturally-occurring element. Uranium is used as fuel in nuclear power plants. .

Vitrification: The process of converting radioactive waste liquids into a solid and stable glass form that is suitable for long-term storage and disposal.

Yellowcake: Uranium oxide (predominantly U3O8) powder, produced by milling uranium ore.

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