What is radioactive waste?
This is the residue of any process that uses radioactive material and originates from a range of industries. These include the nuclear industry, hospitals, universities, pharmaceutical companies and research establishments. In general this waste consists of a mixture of radioactive materials and can be solids, liquids or gases.
Is all radioactive waste the same?
No. Radioactive waste is generally divided, for management purposes, into four classes, which relate to the quantities of radioactivity involved and the controls required:
- High level waste (HLW) - extremely high levels of radioactivity arising from the reprocessing of nuclear fuel. Due to its radioactivity it produces its own heat and must be cooled constantly. It is currently kept in special, long-term storage.
- Intermediate level waste (ILW) - lower levels of radioactivity, which do not require cooling. It is currently kept in special storage.
- Low level waste (LLW) - of such low activity levels that it may be disposed of under controlled conditions or to specific authorised sites
- Very low level waste (VLLW) - this waste is of sufficiently low activity that it can be disposed of to landfill sites with domestic rubbish.
What happens to radioactive waste?
Radioactive waste is either disposed of to the environment or treated and stored. As with all industrial waste, the eventual fate of radioactive waste is determined by its impact on people and the environment. Lower activity wastes may be disposed of to the environment, higher activity waste is currently placed in long term storage.
How are radioactive discharges regulated or controlled?
Discharges to the environment are closely regulated and controlled by the Government, through the Environment Agencies. These agencies use a system of legal authorisations to set limits and controls on organisations that store and discharge radioactive waste. There are continuous programmes of inspection and monitoring of the environment around these sites, the results of which are published by the Environment Agencies.
How much radioactive waste is stored in the UK?
According to the Department of Environment Farming and Rural Affairs (DEFRA) in April 2002 the radioactive wastes stored in the UK were:
High Level Waste: volume 1960 cubic metres, mass 3290 tonnes, activity 57,800,000 terabecquerels
Intermediate Level Waste: volume 75,400 cubic metres, mass 90,400 tonnes, activity 5,290,000 terabecquerels
Low Level Waste: volume 14,700 cubic metres, mass 17,800 tonnes, activity 11 terabecquerels
(1 terabecquerel is 1,000,000,000,000 becquerels)
What are the Government's policies for the management of the radioactive waste that is stored?
The Government's policy on management of high and intermediate level waste is under review. In 2001, it began a wide-ranging public consultation to inform the development of its policy in this highly controversial area. The Government set up the Committee of Radioactive Waste Management (CoRWM) to review, evaluate and consult on the various options for managing high and intermediate level radioactive waste.
What are the options for the long-term management of intermediate level and high level radioactive waste?
See the CoRWM website for the options being considered.
What are the risks from long term storage of radioactive waste?
Surface storage may leave a facility vulnerable to terrorist attack or dispersion through accidents. However surface storage greatly eases the long-term management of the material. Underground storage may be less vulnerable to attack but carries a risk of contamination of ground water. Both options present significant challenges eg, in designing structures that will last many centuries.
Does radioactive waste, discharged or stored, represent a significant risk for the people of the UK?
For the vast majority the impact of radioactive waste is very small if not insignificant. Even for people who live near major nuclear sites, the risk is small compared to the other risks of modern living. In planning for long term storage solutions, the Government has set stringent risk targets for the public, which will be used in the selection and development of the site(s).
Is solid radioactive waste still being dumped at sea?
No. This practice was abandoned in 1982 by international agreement.
What is COMARE?
COMARE is an independent expert advisory committee with members chosen for their medical and scientific expertise and recruited from universities, research and medical institutes. Members have never been drawn from the nuclear or electrical power supply industries. COMARE's terms of reference are 'to assess and advise Government and the devolved authorities on the health effects of natural and man-made radiation and to assess the adequacy of the available data and the need for further research'.
COMARE 11 - Why was this report written?
This report considers the geographical distribution of childhood cancer throughout the UK and was produced in response to certain recommendations in their third report (1989). The study was carried out to ascertain whether patterns of cancer incidence around nuclear establishments were different from those in the rest of the UK.
Has this epidemiological study access to the necessary data?
Yes, the study used as a database the National Registry of Childhood Tumours for the time period 1969-1993 which includes data on 12,415 cases of leukaemia and non-Hodgkin's lymphoma and 19,908 solid tumour cases.
What are the main conclusions?
Many cancers (including leukaemia) were shown to cluster in a non-random fashion in high socio-economic areas. The clustering was not more marked near nuclear power generating plants but there were excesses of some types of cancer near Sellafield, Dounreay, Aldermaston, Burghfield and Harwell. There was also a trend of risk with distance from Rosyth. The excesses, types of cancer and time scales were not consistent around these sites.
Are the clusters of cancers linked with radioactive discharges?
Because there are not anomalous clusters of childhood cancers around all nuclear sites where there are discharges, the report concludes that the two are not specifically linked. However, the clusters in time and space around Sellafield (actually in the village of Seascale) and Dounreay are not likely to be due to non-random clustering. COMARE mentions population mixing as a possible explanation.
Does COMARE suggest a causative link with any agent for childhood cancer?
The Committee explores and explains the multistage theories of cancer induction and concludes that the present study's results are consistent with an infective process i.e. one of the steps in the development of cancer is a rare and unusual response to one or more (unidentified) infective agents.
Overall will this report quell fears of whether childhood cancers are linked to radiation exposure from the environment?
The simple is answer is, no, although in general living near a power generating plant does not seem to confer excess risk. However, there are still largely unexplained and persistent excesses of cancers around certain sites which are historically those which have discharged the most radioactive materials.
How are radioactive sources controlled in the UK?
There are long standing legal controls on the use, storage and transport of radioactive sources. It is the user's responsibility to comply with this legislation. Compliance is monitored by the Environment Agencies (England and Wales and Scotland), the Health and Safety Executive and the Department for Transport. Part of the legislation is to ensure the security of sources to prevent their loss, misuse or misappropriation.
What measures are in place to prevent the illicit import of radioactive material into the UK?
Devices to detect radioactive material may be deployed at points of entry into the UK where there are both permanent installations and mobile equipment (Home Office). In addition, various industries operate radiation detection equipment to identify unauthorised movements of radioactive materials (e.g. the metal recycling and nuclear industries).
What incidents have occurred with sources in the UK?
Details of incidents involving radioactive material are published by Public Health England. There is also the Ionising Radiations Incident Database (IRID) which analyses reported incidents in the workplace. The site newsletters of the major nuclear operators also contain information about incidents.
Who co-ordinates international safeguards for safety and security of radioactive material?
The International Atomic Energy Agency has sponsored many initiatives to improve the safety and security of radioactive sources. Originally the initiatives were introduced because of a number of incidents involving the mishandling of disused sources outside regulatory and institutional control. Now the IAEA action plan includes measures to reduce the risk of trafficking and malicious use of radioactive materials.
How easy is it to disperse the contents of a sealed source into the environment?
The design and manufacture of sealed sources is to exacting British or international standards (BSI). These specify rigorous tests for resistance to impact, fire and corrosion to maintain integrity under normal and accident conditions. Determined and very extreme actions would therefore be needed to breach source integrity. In the unlikely situation that the capsule is breached it would be possible for the source to contaminate the immediate environment. Widespread contamination is more difficult, and dilution and dispersion may reduce the risk to individuals.
How easy is it to steal a radioactive source?
Several levels of security surround radioactive sources. Highly active sources used in hospitals in radiotherapy are usually encased in substantial shielding extremely difficult to remove and impossible to do so covertly. Handling such sources would represent a significant risk to the potential thief. Smaller sources of radioactive material are theoretically more vulnerable, but covert misappropriation would still be extremely difficult. The potential use as a health threat would be much smaller.
Do radioactive sources leak?
No, as long as they are handled correctly or not damaged. Sealed radioactive sources are manufactured in such a way as to prevent leakage. A sealed source is a radioactive material that is either permanently sealed in a capsule or closely bonded and in a solid form. The capsule or material of a source is manufactured strong enough to remain leak-tight under the conditions of use and wear for which the source was designed and also under foreseeable mishaps. Sealed sources are classified by an International Standard ISO2919 based on test performance. These standards specify, appropriate to the type and application, general requirements, performance tests, production tests, marking and certification. Prototypes of sources are tested for resistance to temperature, external pressure, impact, vibration, and puncture in classes of increasing severity. Sources intended for a specific application, e.g. industrial radiography, nuclear medicine, cancer treatment, sterilisation of medical equipment, etc have to meet minimum criteria outlined in the standard. Radioactive sources used in certain medical applications or for tracer studies, e.g. for environmental purposes, are by their nature open (unsealed). These are governed by legislation so that, during storage, handling and use, administrative and engineering controls are required to maintain containment. All sources are issued from the manufacturer with instructions for handling and storage. Sources are only sold to organisations that have appropriate regulatory authority to hold and work with such items. All sources are transported in appropriate types of transport containers in accordance with the current national and international transport regulations. The user is required to comply with regulations governing work with sources and their storage when not in use. These arrangements are subject to regulatory audit. Finally, when declared spent, sources can only be transferred to organisations that are authorised by regulatory authorities to handle and manage such wastes.
What precautions are taken to ensure industrial and medical sources can't be lost?
Procedures for extensive and thorough record keeping must be demonstrated before anyone can be registered as a legal holder and user of radioactive sources. In the UK, medical radiation sources are subject to the same high level of surveillance as industrial sources.
What happens when an object suspected to be a radioactive source is found?
When the police are informed of a suspect source, they initiate The National Arrangements for Incidents Involving Radioactivity (NAIR). Through NAIR, the Police have access to local radiological protection expertise that can provide a rapid initial assessment. If necessary a secondary response can be triggered to provide support with more specialist equipment.
What was the Windscale Fire?
The accident occurred in October 1957 when a fire broke out in the core of a nuclear reactor at Windscale Works (part of the Sellafield site) on the west coast of Cumbria. This led to an uncontrolled release of activity to atmosphere during the 10th and 11th October. The resultant plume of radioactive material travelled over much of England and parts of northern Europe.
What radioactivity was released?
At the time of the accident, the radionuclide identified as being of principal concern was the fission product iodine-131. It was known that iodine concentrates in the thyroid gland and that children’s thyroids were particularly sensitive. Although iodine-131 has a relatively short half-life of 8 days, the route of intake via cow’s milk was taken seriously after initial monitoring results were obtained, and a milk distribution ban was instigated over an area of 500 km2. The inventory of radionuclides released was dominated by the noble gas xenon-133 (26,000 TBq) and tritium (5,000 TBq), followed by volatile fission products iodine-131 (1800 TBq) and caesium-137 (180 TBq), but also an important alpha emitter, polonium-210 (42 TBq). In terms of the collective effective dose to the population, iodine-131 contributed 37%, polonium-210,37% and caesium-137 15% .
How was the accident detected and what were the immediate consequences?
The first indication of the fire came from radiation monitors detecting increased levels of radioactive material in the cooling air passing up the exhaust chimney. Filters (known as 'Cockcroft’s Follies' after Sir John Cockcroft who had them installed as an afterthought) had been placed at the tops of the 120 m chimneys, and these filters probably averted a worse accident because they trapped radioactive particulate material from the fire. Nevertheless, radioisotopes of volatile elements, such as iodine-131, were carried by the cooling air through the filters and released to the atmosphere. A mixture of fission products and some other radionuclides, notably polonium-210, were released. Initially the radioactive cloud was carried on the wind towards the northeast, but then a northwesterly wind blew the plume to the southeast, over England and on to mainland Europe.
Why did the Windscale accident happen?
The reactor in which the fire occurred was one of two constructed to produce plutonium for the UK’s nuclear weapons programme, which were known as the Windscale Piles. These reactors used uranium metal fuel and a graphite moderator, and cooling was achieved by blowing environmental air through the core and out of a 120 m high chimney. Because of the relatively low operating temperature of the reactors, energy (known as Wigner energy) became stored in the graphite moderator and had to be occasionally released – this was done by heating the core by running the reactor at low power. On this occasion, because of poor positioning of thermocouples, the operators were unaware that part of the core was becoming overheated and eventually one or more of the fuel cans failed. This led to a fire which was eventually brought under control by flooding the core with water. A closed official inquiry – the 'Penney Inquiry' – reported in late October 1957 and its conclusions and recommendations were selectively summarised in a White Paper published the next month, but the 'Penney Report' itself was not made public until 1988 because of its political sensitivity. Both Windscale Piles were mothballed after the accident and never restarted, and decommissioning work continues today.
What lessons about emergency planning were learnt from the accident?
One enduring legacy of the Windscale accident was the subsequent attention given to emergency planning around nuclear sites. Multi-agency committees were established, including elected members of local councils and all the emergency services. Regular exercises are held to test responses to an incident both on and off-site. Arrangements were updated in the light of other events, particularly the accident in the USA at Three Mile Island and the major accidents at Chernobyl and Fukushima. Off-site incident control now rests with the local police and briefing goes all the way to top levels of Government.
Is there still a risk?
As long as the radioactive materials released from the Windscale Fire remain in the environment, there may be a tiny increased risk to the population. However, most of the released fission products, apart from caesium-137, will have physically decayed and present no ongoing risk. Of the other materials, polonium-210 has a half-life of 138 days and has long gone, but tritium (t½ = 12.3 a) and the very small amount of plutonium released (0.02 TBq) continue to present a risk legacy.
What were the health effects?
There were no early health effects because radiation doses were not high enough. Long-term health effects would arise from the irradiation of tissues such as the thyroid, mainly as a result of intakes of radionuclides, such as iodine-131, producing an increased risk of cancer. Assuming a linear relationship between dose and cancer risk, the collective dose in the population, which resulted from external exposure and intake of radionuclides by either inhalation or ingestion, can be used as a broad predictor of potential long-term effects. The overall estimated collective effective dose of 2000 man-Sv (of which approximately 800 man-Sv was from ingestion of milk and other foodstuffs, 1000 man-Sv from inhalation and 250 man-Sv from external irradiation) may result in around 200 extra cancers throughout England over many years. Considering UK variations in cancer incidence and natural background radiation (which includes a component from polonium-210), these potential extra cancers will be statistically undetectable, although thyroid cancer incidence is being monitored.
How were the public protected?
The public were protected by a milk distribution ban, which was instigated at a radioactive iodine-131 activity concentration in milk of 3.7 kBq/litre. This ban, imposed for a few weeks, covered a coastal strip of land from 10 km north of Windscale to around 20 km to the south, a total area of about 500 km2 and affecting about 600 farms. The highest I-131 activity concentrations in milk in farms close to Windscale were around 30 kBq/litre (which compares with the highest levels in the same area after Chernobyl of around 0.4 kBq/litre). The milk withheld from sale was poured away.
What was the effect on workers?
Some of the workers involved in controlling the fire and the clean-up received higher than normal doses, although the mean recorded external dose for October 1957 was only 6 mSv. A study in 2010 of the 470 male employees involved in emergency work and the clean-up operations found no measurable effect on their mortality or cancer morbidity risks in the 50 years following the accident when compared with Sellafield workers employed in 1957 but not involved in fire operations.
Could the same thing happen in today's nuclear reactors?
The Windscale Piles were the first large-scale reactors in the UK. Their crude design and operation must be viewed in the political context of the early Cold War era and the policy of the UK Government to quickly build up an independent nuclear deterrent. While the first Magnox reactors at Calder Hall and Chapelcross had a dual military and electricity generation function, all other power reactors in the UK have been solely for electricity generation. Because of the design and construction of modern reactors and the sophisticated safety features now built in, a similar accident could not happen. However, the Windscale accident happened because of faulty design and operator error, as in the Chernobyl accident 29 years later, while the 2011 accident at Fukushima Dai-ichi demonstrated the importance of defence in depth.
Was this the world's first serious nuclear accident?
The Windscale Fire was the first (and only) serious nuclear accident in the UK, but a major accident (the Kyshtym Accident) occurred less than two weeks earlier at the Mayak weapons plutonium production complex in the Southern Urals of the then USSR, when there was a big chemical explosion in a radioactive waste storage tank. A large quantity of radioactive material was released to atmosphere, causing severe off-site contamination and the evacuation of around 10,000 people. The accident was not officially acknowledged by the Soviet authorities until 1989.