Waste management: a crucial matter
The issue is urgent. Although they have operated their nuclear power plants for decades, none of the Union countries which opted for nuclear energy have implemented acceptable and lasting solutions for the highly radioactive and long-life irradiated materials that are building up in safe but 'provisional' depots at the production sites. This failure to act is seriously compromising the prospects of benefiting from a sector with zero greenhouse gas emissions as part of a European energy strategy for the 21st century. Reprocessing, separation, transmutation and geological disposal are all possible solutions.
Although it does not represent an environmental 'threat' likely to suddenly run out of control – as could be true in the case of a serious fault in reactor safety systems – radioactive waste is the Achilles heel of a future electronuclear industry. It has been seized upon by the fiercest opponents of nuclear energy as a reason in itself to shut down the sector – a view that is not without public support.
|Research at the Asse salt mine (alongside the Gorleben salt dome – DE) with a view to the long-term storage of nuclear waste. In addition to granite, which provides an excellent geological shield, other underground formations are being studied as possible environments for deep permanent disposal.|
The fact is that this waste is building up all the time. Although very harsh measures already apply to storage security, the problem of disposing of these materials – which sometimes have a very long radioactive life – remains unresolved. Geological burying remains the single possible and acceptable solution (subject to the confirmation of current studies), yet there is no country in the world which has effectively put it into action.
To understand the issues involved in this complex problem, it is first necessary to define exactly what is meant by the rather general term 'nuclear waste'. Nuclear waste consists of a wide range of radioactive elements which are defined in terms of their activity levels – low- and medium-level waste (LMLW) and high-level waste (HLW) – and the duration of this activity. For the latter, the dividing line stands at 30 years – under 30 years, it is referred to as short-life waste and, beyond this period, long-life waste.
LMLW: danger management
LMLW makes up about 90% of nuclear waste. It comprises the consumable materials and protection equipment used at nuclear power plants, but also, to a large extent, the radioactive waste from non-energy sectors such as radiography technologies, imaging and tracing. Despite its low intensity – representing just 1% of the total radioactivity that must be managed – it undoubtedly has the potential to seriously damage human health, so rigorous precautions must be respected when handling and storing such material.
|Plan of the geological disposal project at Äspö (SE), at present Europe's most advanced in terms of feasibility. Image of an underground handling device.|
Given its diverse origin, all European countries, whether or not they have an electronuclear programme, are faced with the same problem of waste management. The Commission's latest estimates put the volume at around 150 000 m3 for the Union as a whole, plus several tens of thousands of m3 stored in the candidate countries.
Nevertheless, considerable progress has been made as regards the rate at which nuclear plants produce this kind of waste. In the early 1990s, when the power generated by the electronuclear sector was comparable to today's levels, annual production was around 80 000 m3. Experts believe that the dismantling of plants will reverse this trend. It is estimated that in the near future the total volume of short-life waste in the Europe of 25 will increase at the rate of around 40 000 m3 a year.
In most cases, however, this category of waste is not cause for major concern. Following various treatment processes to reduce its volume and activity it is solidified in concrete, bitumen or polymers ready for permanent surface storage at specialised centres.
For the small fraction of this LMLW with a radioactive life which exceeds 30 years, the problem is more complex. Representing about 17 000 m3 in the Union as a whole, this originates mainly in the fuel cycle plants of the nuclear industry. The present practice of surface storage for periods of a century or more is far from satisfactory. Consequently, this must be considered for geological disposal.
High-level waste problems
The second category, known as high-level waste (HLW), comes from the used fuel of nuclear plants. This highly radioactive and heat-emitting waste can remain active for thousands if not hundreds of thousands of years. It contains a variety of elements:
|Unloading, plus a view of spent fuel in a cooling pond at the d'Oskarshman/SKB plant (SE).© Bengt/O.Nodin|
The spent fuel is made up of about 96% uranium and 1% plutonium, both of which are major actinides. Some countries have chosen not to reprocess this fuel, in which case it is known as Spent Fuel destined for Direct Disposal (SFuDD). The Union has already accumulated about 12 000 tonnes of SFuDD, with another 5 500 tonnes being held by those countries set to join the Union later this year. Annual production is estimated at 1 730 tonnes in the Europe of 25.
Other countries have, however, chosen to recycle this waste at two sites, one at La Haye in France and the other at Sellafield in the U.K. These plants extract a new fuel from it which can be used at power plants, thereby reducing the radiotoxicity and volume of residual waste after processing.
Finally, there is the 3% of fission products (caesium, selenium, strontium, iodine, technetium, etc.) and minor actinides (neptunium, americium and curium) which come from the irradiation of fuel inside the reactor. Irradiation also leads to the formation of very diverse radionuclides in the shells and sleeves which come into contact with the fuel.
The total volume of waste from the reprocessing of used fuel, fission products and minor actinides currently stored in the Union is about 6 000 m3 and is increasing at the rate of 240 m3 a year. If the SFuDD is then added to this figure, the result is the equivalent of a building with a surface area of 850 m2 rising to a height of almost 30 metres, with an extra floor three metres high being added on every year. That is the scale of the problem facing Europe's electronuclear industry. The real challenge, scientific as well as political, is how to manage this volume, the burden of which will be handed down to numerous generations to come.
HLW is at present stored around the nuclear plants themselves or at provisional disposal sites where it is cooled in ponds or ventilated wells. This cooling phase must continue for about 50 years. But then what? Given the present state of our knowledge and technology, only one solution can be envisaged, at least in the medium term: the storage of high-level waste in deep geological deposits.
This concept, which all the experts seem to favour, originated in 1997 in Africa, during a study of the uranium deposits at Oklo (Gabon). Two billion years ago, an exceptional concentration of ores triggered a chain reaction in these genuine 'natural reactors'. This continued for 500 years before being extinguished, leaving radioactive fission products trapped in the sediments. So, why not follow this example? The depositing of waste in deep geological formations could be 'the' viable response to the unmanageable life of various radionuclides. That left the matter of testing the technological feasibility.
|Reprocessing oven, control room and barrel filling and storage operations, and reprocessed uranium control room at the Tricastin-Pierrelatte (FR) site.|
© Cogema – P.Lesage
The Hard Rock Laboratory (HRL) in Äspö (Sweden), built between 1990 and 1995, played a central role in subsequent studies. This is a vast underground complex lying at a depth of 460 metres beneath the huge mass of granite in the 'Scandinavian shield', two metres of which is enough to keep out radiation. This particularly suitable rock formation has resulted from a very ancient mountain range.
Scientists at the HRL, which receives European funding, are trying to reproduce the conditions of a future subterranean nuclear waste deposit. The heat emitted by radioactivity is mimicked, for example, by electrical resistance. This technique makes it possible to study the many questions raised by the prospect of storing waste for hundreds of thousands of years. How will the rock react to such exposure to heat and radiation? Can underground water circulation be affected? How can the waste be treated to prevent its corrosion? What materials must be used to fill the wells containing the waste?
All these questions are being studied by the consortium of European laboratories participating in the Prototype Repository project, headed by the Swedish firm Svensk Kärnbränslehantering AB in Äspö. The aim is to assess, over a number of years, the performance of a disposal site tested on a life-size scale and to develop models to predict long-term behaviour. In the medium term, Sweden could decide to build a permanent disposal site for its radioactive waste in its granite subsoil.
Neighbouring Finland has already taken the political decision. Following a long and remarkable democratic debate, the Olkiluoto site, adjacent to one of the country's two nuclear plants, was chosen. Work on building the underground disposal site, which is also located in granite rock, is due to begin in 2010 for completion around 2020. The Finnish Parliament has passed a law stating that a further assessment will be made in 2050 to decide whether or not the site should become permanent, taking into account the technologies available at the time.
These two Scandinavian countries are by far the most advanced in defining their waste management policies. Other countries are still at the stage of seeking the best storage concept in other geological formations. In the underground laboratories at Mol (Belgium) and Bure (France), for example, researchers are looking at the possibility of storing nuclear waste in deep clay deposits. In Germany, studies are being carried out in the former salt mines at Asse and Morsleben and in the underground exploration of the Gorbelen salt dome. But in these countries, as in the United Kingdom and Spain, a final choice has yet to be made. The great unknown remains the difficulty of winning public acceptance for such solutions – and, in particular, the degree of opposition from the 'not in my back yard' brigade.
In this fragmented European landscape, what role can the Union play? Two Commission Directorates-General are currently involved: Research, and Transport and Energy. In early 2003, at the initiative of Energy Commissioner Loyola de Palacio, two new Directives on safety in the nuclear sector and the management of radioactive waste were submitted for the approval of the Member States and the European Parliament.
The 'waste’ proposal called on the Union countries to stop dithering and to get a grip on the problem. The text did not say what solutions should be adopted; nor did it advocate the EU assuming responsibility for the problem, leaving that firmly in the hands of those Member States which chose the nuclear option. What it did do was set a precise timetable for the Member States to take a final decision on the choice of disposal sites – to be subsequently vetted by the Commission – by 2008 and to have them operational by 2018. Deemed 'coercive', to date this proposal (together with the 'safety' Directive) has failed to be adopted in the face of strong opposition.
Urgent need for research
The Union is, on the other hand, in a position to provide the Member States with the scientific elements essential for a rational decision. That is where the research DG comes in. Under the Sixth Framework Programme (FP6), nuclear waste management is a major research priority for Euratom and the focus of many of the activities at the Joint Research Centre (JRC), especially at the Institute for Energy in Petten (the Netherlands) and the Institute for Transuranium Elements (ITU) in Karlsruhe (DE).
|Loading bay at dry storage wells for spent fuel and waste at Cadarache – Saint-Paul-lez-Durance (FR).|
© Cogema – Lefevre
The ITU's expertise is seen as particularly strategic and the possible key to a promising development, i.e. one day, mastering the operational technologies with which to isolate the most harmful radio-elements and transmute them into other elements which are less active and have a shorter life. Major research was carried out on this subject in 13 Euratom projects during the Fifth Framework Programme (1998-2002) and others are currently being launched under FP6.
Advanced chemical techniques made it possible, for example, for the Partnew project to perfect the synthesis of organic solvents which permit the extraction of two minor actinides: americium and curium. The aim now is to transmute these radionuclides into isotopes with a shorter life – or which are not radioactive at all – by bombarding them with rapid neutrons. This approach has already brought results in the case of technetium 99 which, with a radioactive life of 211 000 years, has been converted into a stable element, ruthenium 100.
Transmutation on an industrial scale remains a matter for the future, however, although there are a number of avenues to be explored. 'One promising technological way forward is the development of dedicated reactor burners using a waste-enriched fuel, i.e. one rich in minor actinides,' explains Alex C. Mueller of the Institut de Physique Nucléaire d’Orsay (France), a partner in the European PDS-XADS project. Fundamental physicists and nuclear industrialists are working together on this project to make an initial feasibility study for such a reactor burner in which the necessary neutron source for transmutation would be a proton accelerator.
No time to dither
Researchers engaged in waste management research therefore bear a heavy responsibility. If they do not find a lasting solution within the next decade, nuclear programmes will inevitably be abandoned. By then, the accumulation of waste – made worse by the progressive dismantling of the power plants that are still operating today – will have become unmanageable. The exorbitant costs, in terms of safety and security, of continuing the 'provisional' storage would exceed the burden future generations could bear. Any dithering in the face of this demand would, literally, be a 'time bomb'.
In June 2001, the Russian Duma surprised the whole world by passing a law authorising the importing of foreign nuclear waste. This represents a clear infringement of the international principle, applied within the Union, which makes each country responsible for managing its own nuclear waste. Is this a sign that events are getting out of control? Could we imagine a nightmare scenario in which some countries become genuine nuclear dustbins?