Radioactive waste management is more than just a technical question. Though the waste is not a health threat, its disposal has become a societal issue with a blend of ethical and political considerations. Technical solutions exist for every waste type. They must be clearly explained.

Aside from very low-level waste (VLLW), radioactive waste is classified according to two criteria for purposes of long-term management: the activity level (number of disintegrations per second) and the half-life. For although the half-lives of some radioactive elements can be counted in mere seconds, they can be millions of years for others, whose activity levels are accordingly very low (these radionuclides being practically stable). The activity level of waste indicates its toxicity and therefore its potential impact on humans. Four activity levels are recognized: very low, low, medium and high. The radioactive half-life is split into two categories: short half-life waste (essentially containing beta and gamma emitters) and long half-life waste (containing alpha emitters).

Distinguishing between storage and disposal

In the nuclear industry, storage and disposal mean completely different things. For the former, the situation is temporary, pending waste packaging or the shipment of packaged waste. Disposal, on the other hand, is a situation that will ultimately become permanent, even when a certain degree of reversibility is possible. In fact, radioactive waste management starts at a very early stage, during the design and operation of nuclear facilities, whether they be industrial, medical or otherwise, to reduce waste volumes as much as possible.

And significant progress has been made in this area, with greater treatment efficiency leading to a five-fold reduction in long-lived waste volumes and a ten-fold reduction in their radiotoxicity. Each category of waste is then packaged according to a specific process. Short-lived low-level waste – which accounts for most of the volume – is compacted and packaged in metal drums, encapsulated in concrete, bitumen or special resins. This waste is generally isolated until its radioactivity has fallen to its natural level.

The French have built a special surface disposal facility in the Aube department for this type of waste. Other countries have opted for a near-surface solution, i.e., slightly below the surface.

The question is more complex for long-lived high-level waste, as their potential toxicity is greater and, depending on the specific case, remains significant for periods of up to several tens of thousands of years. Moreover, their radioactivity results in significant heat generation requiring special precautions. This final waste is packaged when the used nuclear fuel is treated, through vitrification and compaction, and is then placed in monitored storage pending permanent disposal. Testing and evaluation of the latter are currently being conducted under the law of 30 December 1991 (see Research mandated by the "Bataille law"), which will be supplemented by legislation expected in 2006 or 2007 at the latest. The need for an adequate level of reversibility will be defined in this legislation, if the parliament deems it necessary.

Reversibility is also being studied in the United States, Germany and Sweden, but so far nothing has been decided. Countries are conducting research into permanent disposal methods based on their specific geology.

Possible solutions

A variety of solutions have been considered for radioactive waste disposal from the very beginning, including disposal under the polar icecap or burial on small desert islands. Undersea disposal was viewed as more realistic, and, in 1967, eight European countries created a nuclear repository in the Atlantic 700 km from the Gulf of Gascony and 4,000 m beneath the ocean surface. Low- and medium-level waste immersion operations complied with the London Convention on the Prevention of Marine Pollution and with the recommendations of the International Atomic Energy Agency (IAEA). The former USSR also deposited large quantities of waste in the Kara Sea. The slow rate of migration from the ocean bottom to the surface confers a certain safety to immersion. In addition, the dilution effect ensures that any radiation remains below allowable thresholds.

Nevertheless, European countries abandoned this option several years ago. For high-level waste, the solution currently recommended by the experts (IAEA, OECD) is deep geologic disposal. In this case, waste packages are buried at a depth of several hundred meters in structures for which it is certain that there will be no geological upheavals for millions of years. A principle of functional complementarity is then applied to ensure radioactivity retention. These functions are physical and mechanical mechanisms, the main one being radionuclide migration.

To limit migration, the designer of the disposal site often reasons in terms of "containment barriers" between the waste package and the immediate environment, including man-made barriers (encapsulation of radioactivity in a glass matrix, bitumen or cement; steel container) and natural barriers (geologic formation). The latter is the principal protection, for many millennia.

Indeed, the geologic formation must meet very rigorous requirements, such as the absence of free water and very low permeability. To characterize suitable rock, two criteria apply: it must be geologically and hydrogeologically stable. In other words, to prevent radionuclide migration, water must not flow through the rock.

Essential laboratories

For research on deep geologic disposal, researchers are interested in understanding the physico-chemical mechanisms that affect the behavior of waste packages, firstly through mathematical modeling, but also by observing natural analogs (volcanic glass, elements found in the Oklo natural reactors in Gabon) and by performing full-scale experiments. The main phenomena studied are those involving water (in liquid or vapor form), heat and radiation from the package itself.

Every country faced with finding a solution for the disposition of their radioactive waste acknowledges the necessity of creating dedicated laboratories to test the performance of various soils as geologic barriers, the migration of radioactive elements in the ground and the interactions between materials that have been disposed of and the natural environment. These underground laboratories are essential tools for determining the conditions under which a repository could be developed and operated. About twenty such laboratories are currently either under construction or in operation around the globe.

The main ones are in Belgium, Canada, the Czech Republic, Germany, France, Hungary, Japan, Sweden, Switzerland and the United States. Research is being carried out on various types of terrain, including clay in Mol, Belgium; salt at Asse, Germany; granite at Grimsel (Switzerland), Stripa (Sweden) and Pinawa (Canada); and shale in Japan. Surface disposal of low- and medium-level waste is currently practiced in Canada, the United Kingdom, United States and France.

Management organizations

Operators in every country with a nuclear power program are confronted with the problem of radioactive waste management. With the exception of Finland, where operators themselves assume responsibility for disposal, each country has an organization or agency dedicated to this mission.

Their mandate is to design, build and operate disposal facilities for existing and future radioactive waste. In Belgium, for example, the Belgian Agency for Radioactive Waste and Enriched Fissile Materials (ONDRAF) has fulfilled this role since 1980. In Canada, the Nuclear Waste Management Organization (NWMO) began performing this task more recently, in 2002. In Switzerland, it is the National Cooperative for the Disposal of Radioactive Waste (NAGRA) and the Commission on Waste Management (CGD), while it is the Swedish Nuclear Fuel and Waste Management Co. (SKB) in Sweden. In France, the National Radioactive Waste Management Agency (ANDRA) created in 1979 manages the Centre de l'Aube disposal facility for short-lived low- and medium-level waste in Soulaines, which is currently in operation. ANDRA also operates the Morvilliers disposal facility near Troyes, a few kilometers away from the Soulaines facility, for very low-level waste. In most countries, radioactive waste management policy is defined in legislation introduced by the government and passed by parliament. This is notably the case in Belgium (law of 8 August 1980), Japan (voted by the Diet in May 2000), Finland (May 2001), Sweden (April 2003) and Spain. In the United Kingdom, long-term waste management will fall under the responsibility of the Committee on Radioactive Waste Management (CoRWM) formed in late 2003 following the national debate on this subject that began in September 2001, with a final decision to be made by 2006.