Radioactive waste management

Is waste management exclusive to electricity generation? 

All human activity generates waste to a greater or lesser extent. These are substances, materials, or objects, remains of natural products or manufacturing processes, for which no further use is foreseen.

In our society, there is a continuous increase in the production of waste for many reasons, including rapid population growth and increasing technification and industrialization.

The current Waste Act of April 1998 establishes a single classification of waste into two main groups, municipal and hazardous waste. However, for practical purposes, this classification poses problems, given the wide variety of waste generated. For this reason, the Administration plans to address specific regulations that consider the groups of waste that have historically been considered: urban, urban-assimilable, agricultural and forestry, banal and inert, industrial, toxic and hazardous, and sanitary.

In Spain, 300 million tonnes of atmospheric pollutants are produced each year, 20 million tonnes of solid urban waste, 4 million tonnes of hazardous waste, and 2,000 tonnes of radioactive waste, of which only 160 tonnes correspond to spent fuel.

How serious is the problem of waste management in today's world?

Industrialized society is faced with the difficult problem of having to design, implement, and achieve adequate management for all the waste that is produced. Waste management is understood as the set of activities that lead to its reuse, its disappearance or, failing that, its neutralization and evacuation to localized sites, guaranteeing long-term safety.

The global picture of hazardous waste from conventional industry is serious and worrying, in some countries more delayed than in others, but with the common denominator of large volumes and little control and the problem of the location of the waste.

Concern about waste began in Europe with Directive 75/442/EEC, amended by Directive 91/156/EEC, and the creation, by the Commission of the European Union, of Directorate General XI, which prepared and presented to the Council of Europe, in 1989, a management strategy document for all waste.

Despite the importance attached by the Commission to waste policy and the measures adopted over the last twenty years, it has been noted that recycling and reuse are still in an incipient state. This is why the Fifth Action Programme (1993-2000) set long-term objectives for each of the areas, including waste management, to achieve sustainable development.

The Community strategy focuses on a comprehensive waste treatment concept, encompassed in what has been termed the "Management Hierarchy". This comprises the menu of options to be adopted by those who deal with waste and is centered on five main axes: prevention; recovery; safety in transport; optimization of final disposal and corrective action.

In Spain, the current Waste Law in force is 10/1998 of 21 April 1998, which provides a common framework for a homogeneous application of the management hierarchy. In 1990 the public company EMGRISA (Empresa Nacional de Gestión de Residuos Industriales, S.A.) was set up to manage the National Hazardous Waste Plan.

The treatment of radioactive waste is carried out following the General Radioactive Waste Plan, which is approved by the Government and implemented by the National Radioactive Waste Company (ENRESA), created in 1984. The management of these wastes is regulated by a broad legal framework that specifically contemplates all activities relating to their treatment.

The technological development achieved in radioactive waste management contributes to the development of practices applicable to other types of waste, especially those requiring long-term treatment.

What is radioactive waste and where does it come from?

Mankind has lived with radiation and radioactive isotopes since the appearance of our life on earth, where there were radioactive isotopes with very long half-lives, such as potassium-40, uranium-238, uranium-235, and thorium-232, as well as the isotopes resulting from the decay of the latter three. Some naturally occurring radioactive isotopes have also been used by man, such as radium-226 in therapeutic techniques and uranium-235 in nuclear reactors.

Radioactive waste is any waste material or product, for which no use is foreseen, that contains or is contaminated with radionuclides in concentrations or activity levels exceeding those established by the competent authorities.

Radioactive waste is produced in the various applications of radioactivity, namely:

• Energy applications. This is the most important group. The largest volume of radioactive waste is produced in the different stages through which nuclear fuel passes (fuel cycles) and in the decommissioning of nuclear power plants. All these wastes account for about 95% of total production.
• Non-energy applications. Derived from the uses of radioactive isotopes, mainly in three types of activities: research, medicine, and industry. This group is known as the "small producers", because even in the most technologically advanced countries, where the aforementioned activities are highly developed, the volume of radioactive waste generated is small compared to that generated in the production of nuclear power, and may be said to be in the order of 5%, without this meaning that its management should be less rigorous.

How is radioactive waste classified?

Radioactive waste can be classified according to various criteria, such as its physical state (solid, liquid and gaseous), type of radiation emitted (alpha, beta, gamma), radioactivity content, half-life of the radionuclides it contains, heat generation, etc.

From the point of view of their management, radioactive waste in Spain is currently classified as follows:

• Low and intermediate-level waste.
  • They have low specific activity per radioactive element.
  • They do not generate heat.
  • They contain beta-gamma emitting radionuclides with half-lives of less than 30 years, which means that they reduce their activity to less than one thousandth in a maximum period of 300 years.
  • Their alpha emitter content must be less than 0,37 GBq/t (0,01 curios/tonne on average).
• High-level waste.
  • The radionuclides contained in high-level waste have a half-life of more than 30 years.
  • They contain long-lived alpha-emitting radionuclides in appreciable concentrations above 0.37 GBq/t (0.01 Ci/t).
  • They generally give off heat.

Not all countries use the same classification of waste, which is why the Commission of the European Union has recommended unifying criteria, for which it proposes the following classification, to enter into force on 1 January 2002.

• Transition radioactive waste.

Waste, mainly of medical origin, disintegrates during the temporary storage period and may then be managed as non-radioactive waste, provided that clearance values are respected.

• Low and intermediate-level waste.

Their radionuclide concentration is such that the generation of thermal energy during their disposal is sufficiently low.

• Short-lived waste.
  • Radioactive waste containing nuclides with a half-life less than or equal to that of Cs-137 and Sr-90 (approximately 30 years), with a limited concentration of long-lived alpha radionuclides (4,000 Bq/g in individual batches of waste and an overall average of 400 Bq/g in the total volume of waste).
• Long-lived waste.
  • Long-lived radionuclides and alpha emitters whose concentration is higher than the limits applicable to short-lived waste.
• High-level waste.

Waste with a concentration of radionuclides such that the generation of thermal energy during storage and disposal must be taken into account. This type of waste is mainly obtained from the treatment/conditioning of spent fuel.

What wastes are generated in the various applications of radioactive isotopes?

The radioactive waste generated by small producers comes mainly from three types of facilities: health care, industrial and research facilities.

In medical and hospital facilities, the use of radioactive isotopes for the diagnosis and treatment of diseases is widespread and growing.

Thus, unencapsulated radioactive elements, usually in the liquid phase, are used for diagnosis by tracers with Tc-99m, 1-125, H-3, or C-14, or for the treatment of thyroid diseases (1-131) or blood diseases (P-32). These activities generate solid radioactive waste: cotton wool, rubber gloves, syringes, etc., as well as liquid radioactive waste, which is classified as intermediate-level waste.

On the other hand, encapsulated sources are used in the treatment of tumors, with the use of Co-60 being very frequent. These sources, once removed, are managed as intermediate-level waste.

Encapsulated sources are also used in industrial installations. Lower activity sources are used in process control. For non-destructive testing of metal constructions by gammagraphy, higher activity sources are needed, and in irradiators for sterilization of medical or food materials, higher activity sources (e.g. cesium-137) are needed. In all cases, these sources, at the end of their useful life, are considered as low and intermediate-level waste.

In research facilities, wastes come from teaching and research reactors, metallurgical hot cells (auxiliary research facilities where tests, manipulations, trials, etc. are carried out), pilot plants, and decontamination facilities. These wastes are of a highly variable physical, chemical, and radioactive nature and can cover the whole range of radioactive waste classification.

What changes does the fuel undergo in a nuclear reactor?

The nuclear fuel, during its stay in the reactor core, is subjected to high neutron irradiation, and its constitution is transformed over time.

Before the fuel is introduced, three different parts can be characterized:

• The fuel itself (UO2).
• The cladding.
• Structural materials (grids, guide tubes, etc.).

Under irradiation, these materials undergo the following transformations:

• In the fuel (UO2), as a result of the break-up of the atoms, fission products (F.P.) appear, which are generally beta and gamma emitters. Neutron capture reactions transform part of U-235 into U-236 and part of U-238 into the heavy elements known as transuranic (TRU), such as plutonium, neptunium, americium, and curium, which are characteristically alpha emitters.
• In turn, the plutonium generated (Pu-239) is partly fissioned, as it is a fissile element (1 g of Pu-239 is equivalent to 1 g of U-235) and contributes to the generation of energy and the inventory of fission products.
• The emergence of U-236, fission products, and TRU limit the degree of burn-up, even if U-235 and plutonium remain because they interrupt the fission chain reaction by capturing neutrons (they are neutron poisons) and the elements have to be removed from the reactor core, and replaced by new ones in an operation called refueling, in which between one third and one-quarter of the total number of elements in the core are renewed. This operation is done, depending on the type of plant, in cycles of 12, 18, or 24 months. The elements removed are known as irradiated, spent, or burned fuel.
• In the sheath and in the structural materials, so-called activation products appear, formed by neutron capture reactions by some of their constituent elements, giving rise to radioactive elements. The most important radioactive isotope formed is cobalt-60.

A 1,000 MW reactor uses between 20 and 30 tonnes of fuel per year. The spent fuel contains more than 99.5% of the artificial radioactivity generated in the production of electrical power in nuclear power plants.

Spent fuel contains fission products and transuranic elements generated during fuel burn-up in the reactor, as well as unconsumed uranium (considering the more general case of no reprocessing of spent fuel).

The fission products are gamma and beta emitters, with only gamma radiation having a large penetrating power and consequently being present outside the fuel with a value depending on the type of radioisotope considered; beta radiation never goes outside the fuel. These gamma emitters, taking into account their half-life and energy, will have decayed to natural background radioactive values in about 700 years.

Unconsumed uranium and transuranium elements are essentially low-penetrating alpha emitters (they have the same characteristics as radioactive ores); from the point of view of the radiation emitted, they do not constitute a risk after a storage period of 700 years, as do fission products. These elements are therefore only dangerous if they are released and find their way to be inhaled (for which they need to be transformed into gases) or ingested (for which they need to enter the food chain of plants, animals, and humans).

In other words, the impact of a high-level waste repository, after 700 years, would be analogous to that of a toxic waste safety deposit.

What can be done with spent fuel?

In the early days of the use of nuclear energy for electricity production, the treatment of spent fuels, also called reprocessing, was considered indispensable to recover the U and Pu present in them for further use as energy materials.

In the late 1960s, a shortage of commercial reprocessing capacity was foreseen in view of the planned construction of nuclear power plants, although the technology seemed relatively simple and the costs low. In the 1970s, reprocessing proved to be technically difficult, and increasingly stringent safety standards increased costs considerably. At the same time, offers of commercial reprocessing services were seriously affected by a change in US policy in the late 1970s on Pu recycling (non-proliferation of nuclear weapons). This, together with the fall in the price of U and price competition for enrichment services, has meant that there are now only two options for enrichment management: "open cycle" or "closed cycle".

The "open cycle" considers spent fuels as high-level radioactive waste for disposal in deep geological formations (AGP).

The "closed cycle" carries out the treatment of spent fuels (reprocessing) to recover the U and Pu present in them for use as energy materials.

Since the beginning of the 1990s, given the difficulties, mainly social and political, that have arisen in all countries for the public acceptance of deep geological disposal (DGS) of high-level waste, some of these countries, mainly France and Japan, have proposed to research and develop the separation and transmutation (ST) of certain long-lived radionuclides present in the irradiated elements. The aim is to reduce the long-term radiotoxic inventory of high-level waste and thus the radiological risk of its disposal. This new form of spent fuel management is known as the "advanced closed cycle".

These three options have two key steps in common: the temporary storage of spent fuels and the subsequent disposal, either of the spent fuels themselves or of the residues from current or advanced reprocessing.

If spent fuel is reprocessed, what wastes and other materials are generated?

In principle, U and Pu are recovered for subsequent use as energy materials, and low, medium, and high-level waste is obtained, which must be managed appropriately.

Currently, the countries that totally or partially reprocess their spent fuels, either in their own facilities or by contracting services from abroad, are France, the United Kingdom, Japan, Russia, Germany, Belgium, the Netherlands, China, India, and Switzerland. Only the first two offer reprocessing services, which entails, in addition to the high cost, the return of the recovered U and Pu, as well as all the waste produced, previously conditioned in different types of containers.

After the necessary temporary storage of the spent fuel, the uranium pellets contained in the spent fuel rods are unsheathed in the reprocessing process by cutting and chopping them. The pellets are dissolved with a mixture of acid and water, the resulting liquid solution is treated with solvents capable of extracting the isolated uranium on the one hand and the plutonium on the other hand, leaving the fission products and the rest of the actinides in the aqueous acid solution.

Thus, the aqueous solution contains most of the artificial radioactivity contained in the spent fuel; it is a high-activity liquid waste that is stored in tanks until it undergoes a vitrification process to fix the radioactivity in an insoluble solid product.

The final product that remains is an airtight stainless steel capsule containing the glass containing the radioactivity that was in the fuel, this package being the high-level waste.

The pieces of cladding resulting from the decoating are a radioactive material due to the effects of activation and are also contaminated by their contact with the pellets, so they constitute a solid waste of medium radioactivity. These remnants of the sheaths are placed in stainless steel drums and the remaining voids are filled with cement. The package obtained is a medium activity waste.

Finally, reprocessing facilities produce technological and process wastes, which are low-level wastes that are cemented and packaged in conventional casks to form a low-level package.

In reprocessing, no new artificial radioactivity is generated, only the radioactivity present in the spent fuel is worked with, distributing it more rationally and reducing the radioactivity due to the separated uranium and plutonium. This makes it possible to reduce not only the volume but also the isolation time required for the radiotoxicity of the final waste to fall to natural radiation values.

What is the management of spent fuel considered as waste?

When the open cycle strategy is chosen, the spent fuel must be managed as a high-level radioactive waste, passing through an intermediate stage of temporary storage prior to its final management.

The temporary, or intermediate, storage begins in the plant's own pools where the spent fuel is discharged after its removal from the reactor, in order to allow its radioactivity and residual heat to decay.

As the capacity of these pools is limited, it is necessary that after a certain period of time the fuel be transferred to intermediate storage facilities awaiting final management. This stage of management is considered to be satisfactorily resolved on the basis of different techniques, such as storage in the pools themselves or dry storage (metallic or concrete casks, chambers, etc.), and there are independent or centralized installations with operating experience throughout the world.

In Spain, once the fuel pool had been filled, the Trillo NPP built a temporary above-ground spent fuel storage facility in 2002, with a capacity for the storage of 80 casks specially designed to house 21 spent fuel assemblies each. At the end of 2005, there were 10 casks containing a total of 210 fuel assemblies in this Individualised Temporary Storage Facility (ITSF).

Other temporary storage facilities are foreseen for the fuel from the rest of the nuclear power plants, which should be in operation prior to the dates on which the pools at each plant become saturated.

As regards final management, there is international consensus on the technical feasibility of deep geological repositories (DGS), there being a high degree of development in this respect in many countries, although the implementation processes are slower than expected, fundamentally due to problems of public acceptance and the existence of satisfactory temporary solutions.

Although several countries are at a very advanced stage of PFA (USA, France, Germany, Sweden, Finland, etc.), there are currently no operational facilities at the industrial level, except the Waste Isolation Pilot Plant (WIPP) in the USA, for defense waste.

On the other hand, research on new technologies such as separation and transmutation (ST), promoted through international organizations (NEA, IAEA, and EU) and countries such as France, Japan, and the USA, is intensifying to assess the feasibility of this method to minimize the volume and radiotoxicity of the waste.

What is the potential interest in the separation and transmutation of long-lived radionuclides?

Interest in these techniques, the basic objective of which is to reduce the radiotoxic inventory of high-level waste and hence its long-term radiological risk, has been revived in recent years at the initiative of Japan and France, as a result of the problems associated with the acceptance of final disposal of high-level waste in geological formations. A major economic and human effort will be required for its development and implementation, as well as the international collaboration of all the countries that have to manage spent fuels from their nuclear power plants.

To meet the objective of these techniques, it is necessary to separate some radionuclides with long half-lives and high radiotoxicity, such as mainly plutonium already recovered in the current reprocessing and the so-called minority actinides (neptunium, americium, and curium). It has also been proposed to separate some long-lived fission products such as technetium, iodine, cesium, and zirconium.

The objective of transmutation is the transformation of certain long-lived radionuclides into shorter-lived radionuclides or stable isotopes. The operation preceding transmutation is the conversion of the previously separated chemical elements containing the radioactive isotopes to be transmuted into suitable solid forms.

This can be done by fission or neutron activation. In principle, existing reactors of the light water type could be suitable for this purpose, but it has been shown that high energy neutrons, and preferably high flux, are needed, so studies are moving towards fast reactors and systems driven by particle accelerators. These accelerators emit a beam of high-energy protons, which upon impact on a heavy metal (e.g. lead) produce a high flux of very energetic neutrons, capable of fissioning long-lived radionuclides.

Such systems are also known as hybrid reactors, and although they could be used to produce electrical power, currently proposed projects under investigation in the USA, France, Switzerland, and Japan are intended to be used only as transmutational systems.

What other radioactive waste is generated in nuclear power generation?

Radioactive waste generated in the production of nuclear power is usually grouped according to the sequence before and during the operation of the nuclear power plant.

Waste generated before the nuclear power plant.

They contain only natural radioactivity and are the design materials: a) from uranium mining; b) the separation of uranium from minerals extracted in concentrate manufacturing plants (yellow cake); c) enrichment in uranium-235 to increase the concentration of the fissile isotope; and d) the manufacture of nuclear fuel.

Waste generated in the operation of nuclear power plants.

They have their origin in the fission or "burning" of the fuel that is introduced into the reactor to produce energy. The change that occurs in the fuel when it is burned is explained in a previous question.

A very small fraction of the fission products contained in the fuel element passes into the water of the cooling circuit due to defects in the sheaths or diffusion through them; Radioactive products formed by the activation on the surface of the structural materials in the reactor core can also pass into the water; Finally, some impurities contained in the cooling water and substances used in its treatment are activated, giving rise to radioactive products.

For these reasons, process and maintenance waste resulting from the purification of the water in the cooling circuit is produced in nuclear power plants, most of which is low-level waste and, in some cases, medium-level waste. About 100 m3 of this type of waste is produced per year of operation in a 1,000 MW plant, containing a total of 400 curies of activity.

On the other hand, the nuclear fuel, once the established degree of burnout has been reached, is removed from the reactor core and placed in the spent fuel pools of the nuclear power plant itself, whose mission is its radiobiological isolation, the dissipation of its residual heat and its provisional storage awaiting further management. Pool water becomes contaminated, and its decontamination by filtration and absorption produces small amounts of low-level waste.

Finally, we must include here the radioactive waste produced in the dismantling of the plants.

What waste is produced in uranium mining, as well as in the manufacture of concentrates and nuclear fuel?

In uranium mining and in the manufacture of natural uranium concentrates, residual materials are generated, in which small amounts of uranium and most of the descendants of the uranium decay chain are found, that is, it is radioactivity due to radionuclides found in nature.

In uranium mines, the solid residual materials are made up of rocks, with such a low uranium content that their use is not economical (mining tailings), which accumulate in the so-called "slag heaps."

In the production of concentrates, the main residual materials are the remains of ore from which the maximum possible uranium has been separated (plant waste). These overburden are stacked in so-called “overburden docks,” which are generally located within the factory itself.

In these stages, the largest volume of waste in the cycle is produced. In the case of mining, depending on the type of deposit and the exploitation method, they can vary between 3 and 8 tons of waste per kilogram of final uranium obtained. In concentrate factories, this parameter is, in average values, around one ton of waste per kilogram of extracted uranium.

Although it is natural radioactivity that these residual (sterile) materials possess, it has been brought to the surface and concentrated in one area. In the event of rain, there may be runoff and leaks that contaminate surface and subsoil waters (for example, with radium). The wind can also be an agent of dispersion of radioactivity, as it can carry solid particles or radon, which is a gaseous radionuclide produced in the decay of radium. These effects are avoided by carrying out operations known as "remedial actions", which mean a form of sufficient confinement for this natural radioactivity.

The operations consist of filling the galleries of the indoor mines, or the open-air voids in the open pit mines, once exhausted, with the most radioactive debris, leaving the rest piled in the waste dumps duly covered with layers of earth. , which will be revegetated, in such a way that its leaching and erosion by atmospheric agents is minimal.

In the case of concentrate factory dams, a cover is made with successive layers of asphalt, rocks, and clay to prevent the action of wind and water.

In both cases, waste dumps and dikes, while carrying out pollution protection operations, the waste piles are stabilized in order to prevent landslides.

The uranium concentrate, to be used as nuclear fuel, must be enriched in the isotope uranium-235, for which it is converted to gaseous uranium hexafluoride, from which solid uranium oxide is obtained, which is used, in a later stage, to manufacture the ceramic tablets that are inserted into the rods that make up the fuel element.

In these operations, small amounts of waste are produced as a result of the contamination that originates in the different phases, as well as the result of by-products and rejects from the process used.

In both cases, the waste generated only contains natural radioactivity. All of them are waste that is packaged in metal drums for subsequent definitive storage.

What waste is produced during the dismantling of nuclear power plants?

When the definitive shutdown of a nuclear power plant takes place, all the spent fuel in it is removed from the plant in the shortest possible time, both in the reactor core and stored in its pools. In the case of light water reactors, the cooling water and other contaminated liquids are then treated, concentrating and solidifying them with cement, obtaining low or medium-activity solid waste that is removed from the plant.

All low and medium-activity solid waste stored at the plant awaiting shipment to final storage is also removed.

Two different but related processes will then take place, which are decontamination and dismantling.

Decontamination encompasses all cleaning operations to remove small deposits of radioactive waste that may be fixed on the surfaces of the vessel, in pumps, circuits, equipment, floors, etc.

Dismantling is the disassembly and demolition of structures, pipes, and components, concrete or metal, that are internally contaminated, and their treatment as radioactive waste. 85% of the total of a nuclear power plant never becomes radioactive or contaminated and is conventional waste and debris.

What strategy is used to isolate radioactive waste?

The principle behind landfill storage of any type of waste is to isolate it from the human environment, placing a system of barriers between it and people that prevents its return forever, or that minimizes the risks to a practically zero value in the case of return, although this is highly unlikely. This is called confinement.

For radioactive waste, the barrier system must maintain its effectiveness until the radioactivity has decreased due to radioactive decay to the levels set by the competent authorities. In this case, the concept of perenniality that many conventional wastes carry with them is eliminated.

Regardless of the scientific advances that will allow, in the future, the development of technologies capable of eliminating or reducing the radiotoxicity of these wastes (such as separation and transmutation), the strategy to be followed for the final storage of waste is currently internationally accepted and typified. radioactive waste, that is, for its definitive confinement.

The danger to be avoided would be that rainwater or groundwater would eventually come into contact with the radioactive waste, dissolve any of the radionuclides present, and transport them to the human environment.

To dispel this danger, the strategy is based on: a) making insoluble and stable packages with the waste, capable of resisting the aggression of water for a long time, b) designing an enclosure specially prepared to prevent water from having access to its interior, where the packages will be definitively placed, c) locate and build the enclosure in a geological formation, superficial or deep in the Earth's crust, that can guarantee the integrity of the waste for the time required, while preventing or delay their return to the biosphere in the event of a highly unpredictable failure of the entire barrier system.

Nature provides good proof of the viability of this storage strategy. In the early 1970s, while searching for uranium in Gabon, it was discovered that fission reactions had occurred in an area called Oklo. A combination of facts, such as an extraordinarily high concentration of uranium ore and the presence of water, which acted as a moderator, caused the complex to function as a natural nuclear reactor.

The phenomenon began 2,000 million years ago, remaining intermittently active for about 500,000 years. The result was the generation of fission products and transuranides. Most of these substances, as well as their descendants, have remained retained in the same place where they were generated. The geochemical environment of the area has made the migration of these radioactive elements difficult, despite the fact that the characteristics of the geology were very far from those currently required for storage of radioactive waste.

How is low and medium-level waste transported?

The transport of radioactive substances is carried out in accordance with the recommendations established by the International Atomic Energy Agency (IAEA). In the European case, the current legislation is the European Agreement for the Carriage of Dangerous Goods by Road (ADR). The set of measures established by the regulations aims to reduce the probability of an accident occurring and, if it does occur, mitigate its effects.

Transport security is based on the concept of a package, this being the set formed by the radioactive material to be transported and the packaging that confines it. The degree of resistance of this packaging is proportional to the radioactive activity it contains and the physical-chemical form of the substances transported, taking into account their dispersion capacity. Safety is reinforced through the design of specially conditioned vehicles.

Drivers receive specific training, both on the applicable regulations and on the characteristics of the materials they transport, and on the procedures for action in the event of an accident.

According to the geographical location of the producing centers (nuclear power plants, hospitals, industries, research centers, etc.) and the characteristics of the waste to be removed, ENRESA prepares a program in which the dates, times, and routes are established. of withdrawal. These data are communicated, with sufficient advance notice, to the Nuclear Safety Council, the Ministry of Economy, the Civil Guard, Civil Protection, etc.

To ensure that the requirements demanded by current regulations and the company's internal standards are met, ENRESA requires the implementation of quality systems according to UNE-ISO standards, verifying their application through external audits (to transport companies) and internal audits. (to your organization).

ENRESA, in coordination with the General Directorate of Civil Protection, has established a Contingency Plan for the Transport of Radioactive Waste, which classifies the different possible incidents or accidents that could occur during transport. This Plan also establishes the responsibilities of the different organizations or authorities involved.

The documentation generated to organize the expedition and the computer system used to make it possible to know, at all times, the nature of the cargo: the origin of the waste, number of containers, characteristics of each of them (content, radiological data, etc.). In this way, the authorities and organizations in charge of safety have all the information that allows them to optimize the means of intervention based on the characteristics of the transported waste.

ENRESA has a 24-hour intervention team that would immediately travel to the scene of the accident, in order to recondition the damaged materials to remove them from public roads as soon as possible and, subsequently, carry out the necessary cleaning and decontamination work.

How is low and medium-level waste stored?

In the case of low and medium-level waste, the package (called "package") is a metal drum that contains the waste, generally immobilized in cement.

These wastes only need to be confined for a maximum of 250-300 years. The strategy followed for its treatment is definitive storage.

The technology normally used consists of building, around the waste, a system of engineering barriers, located inside, or on a stable geological formation, at the same time suitable to act as a barrier in the event of failure of the artificial ones.

In Spain, the El Cabril storage facility in Hornachuelos (Córdoba) has been in operation since 1992 for this type of waste, built with French multiple barrier technology.

Low and medium-activity waste from nuclear power plants arrives at El Cabril packaged in 220-liter metal drums. These drums are placed in cubic-shaped reinforced concrete containers measuring 2 meters on each side, immobilizing them with a cement slurry.

When the filling cement has set, the containers are taken to their final destination, a reinforced concrete cell with a capacity for 320 containers, which once filled, is sealed and covered with a reinforced concrete slab. When all the cells are complete, they will be covered with successive layers of clay and gravel, the outer layer being topsoil for planting shrubs so that the installation is integrated into the landscape in the area.

The number of existing cells in El Cabril is 28 (on two platforms), built on the ground in a geological formation made up of clayey slates.

The waste from radioactive facilities (small producers) arrives at El Cabril unconditioned, an operation that is carried out in the existing facilities there, proceeding from this operation in the same way as with the waste that originated in the nuclear power plants.

The confinement that occurs with this system is sufficient so that the radiological impact is practically zero. In the unlikely event of an unforeseen accidental situation, in which there is degradation of these barriers, the safety objective is that the radiological impact is in any case lower than the natural background. In this regard, it is worth remembering that 70% of low-level waste becomes harmless in a few decades.

El Cabril has the capacity to store about 50,000 m3, a volume that is estimated to be reached by 2020.

What is the international coverage in the creation of standards for the management of radioactive waste?

Since the celebration of the First International Conference on the Peaceful Uses of Atomic Energy in August 1955 (First Geneva Conference), institutions have been created for cooperation and exchange of information, which have been transcendental in the creation of a body of internationally accepted doctrine for the management of radioactive waste.

The institutions outlined below have participated, although some not exclusively, in activities that have provided international coverage.

1. The International Atomic Energy Agency (IAEA)
2. The OECD Nuclear Energy Agency (OECD-NEA)
3. The International Commission on Radiological Protection (ICPR)
4. The European Atomic Energy Community (EURATOM)
5. The World Health Organization (WHO)
6. The International Labor Organization (ILO)
7. The International Organization for Standardization (ISO)
8. The International Energy Agency (IEA)
9. The United Nations Scientific Committee on Atomic Radiation (UNSCEAR)
10. The Committee on Biological Effects of Ionizing Radiation (BEIR)
11. The International Society of Radiology (ICR)
12. The International Maritime Organization (IMO)
13. The Group of Experts for the Study of the Prevention of Marine Environment Pollution (GESAMP)
14. The European Nuclear Association
15. The International Commission on Radiation Units (ICRU)

This set of bodies, independent of each other, is responsible for the great effort to generate basic technological, safety, radiological protection, social, and ethical regulations, with international projection on the issue of radioactive waste.

What is ENRESA?

States with significant nuclear programs have created specific public entities for the management of radioactive waste, or have made the consortium of nuclear energy-producing companies responsible for their creation, reserving in some way technical and financial monitoring and control.

In Spain, the Nuclear Energy Board carried out the studies and procedures necessary for the creation of ENRESA, which took place by Royal Decree 1522/1984. It is a public company, 80% owned by CIEMAT (formerly the Nuclear Energy Board) and 20% owned by SEPI (formerly the National Institute of Industry).

ENRESA's mission is to adequately manage the radioactive waste produced in Spain and, in this regard, it is assigned the various necessary tasks, but without a doubt, the one with the greatest technical and social scope is that of resolving the safe and long-term storage of all waste. radioactive generated.

As established in the Royal Decree establishing ENRESA, the costs of the activities derived from the management of radioactive waste must be financed by the generators of said waste, and they must cover the expenses derived from all the stages of management, even if these are carried out after the useful life of the nuclear power plants or any other generating facility has ended.

In the nuclear power sector, this financing is done through a percentage fee on the revenue from the sale of all the electrical energy consumed in the country. This fee is approximately 0.8%.

In the case of radioactive facilities (small producers), a fee is established for the provision of the service, which must be paid at the time of waste collection.

The updated amount of the amounts collected, including the interest generated, guarantees the payment of management expenses, which will reach their maximum when the definitive treatment of high-level waste is carried out.