Nuclear Energy

Site Articles

Site Map
Credits

Home Page




Nuclear Energy

Introduction
Henri Becquerel's discovery of natural radioactivity in 1896 made it possible to produce nuclear energy from the 1940s.
The way forward for some, an unacceptable risk for others… This report provides an overview of nuclear technology today.

1 - Radioactivity
The discovery of natural radioactivity in the late 19th century was a gradual process involving several stages.
On November 8, 1895, the German physicist Wilhelm Röntgen discovered an invisible form of radiation capable of producing an image on a photographic plate. The radiation was so unusual that he called it “X-rays.” By placing his hand in its path, he was able to capture an image of his finger bones. The technique of radiography was born.
On January 20, 1896, the mathematician Henri Poincaré presented Röntgen’s discovery to the French Academy of Sciences. One of its members, Henri Becquerel, wondered where these mysterious, invisible rays originated. Poincaré, himself fascinated with physics, suggested that Becquerel investigate a potential link between the fluorescence accompanying the emission of X-rays and the rays themselves. (Fluorescence is the emission of light previously absorbed by certain substances)
After performing unsuccessful tests with various materials, Becquerel tried uranium salt crystals, which he exposed to sunlight on top of a photographic plate encased in black cardboard to shield it from the light. The plate was exposed through the cardboard, and Becquerel concluded that — once excited by light — this salt emitted X-rays. Yet his most important discovery would come a few days later, by sheer coincidence. Becquerel wanted to duplicate his recent successful experiment with uranium and prepared the necessary equipment, before deciding against it, due to insufficient sunlight in Paris that day. Intending to try again later, he stored the photographic plates and uranium salts in a drawer. On March 1st, for the sake of completeness, he decided to develop the plates, which had remained inside the drawer. Much to his surprise, he discovered that they had been strongly exposed in the dark. This phenomenon was independent from the uranium’s fluorescence — uranium salt emits penetrating rays spontaneously, whether it has been exposed to sunlight or not. Becquerel had just discovered radioactivity.
From 1898, Pierre and Marie Curie also became interested in the phenomenon and discovered polonium and radium.
On March 26, 1900, Becquerel identified the beta radiation of radium as an emission of electrons, thus achieving the first detection of an elementary particle. Then Pierre Curie observed that radium emitted considerable energy, a million times greater than any known combustion energy, becoming the first to recognize nuclear energy.
The health hazards of radioactivity were not immediately understood. On the contrary, many therapeutic properties were attributed to radium and it became a popular tonic, prescribed in the form of powders, creams, beverages, compresses, toothpaste and even talcum powder for babies! A grain of radium was displayed at the 1904 Saint Louis World Fair in Missouri, to satisfy public curiosity.
The biological effects of the energy released by radioactivity were observed accidentally by Becquerel. One day, after carrying a vial of radium in his pocket for a few hours, he noticed a red spot on his skin that transformed into a burn. Pierre and Marie Curie confirmed this observation by experimenting on themselves. This was the birth of what would become radiation therapy. In 1903 Becquerel and the Curies received the Nobel Prize in Physics for their discovery of radioactivity, a breakthrough that paved the way for the future of nuclear physics, nuclear energy, the study of the structure of matter and elementary particle physics. In 1911, Ernest Rutherford established the existence of the atomic nucleus and gave the name “proton” to the hydrogen nucleus. He suspected the existence of a neutral proton, or “neutron,” which was identified by James Chadwick in 1932. In 1934, Frédéric and Irène Joliot-Curie discovered artificial radioactivity, and Enrico Fermi demonstrated that nuclei could capture neutrons. Four years later, Meitner, Hahn and Strassmann discovered nuclear fission. In early 1939, Frédéric Joliot identified the chain reaction phenomenon and along with it, the possibility of producing nuclear energy and nuclear weapons.
On December 2nd, 1942, the world’s first nuclear reactor, built by Fermi, became operational in Chicago.

What is radioactivity?
Radioactivity is a natural physical phenomenon in which the atomic nuclei of certain unstable, or radioactive, elements spontaneously transform by releasing energy in the form of radiation. As a result of this process, called radioactive decay, the nuclei lose part of their mass and become more stable.
The radioactive atoms or radioisotopes that produce natural radioactivity have been present in the rocks of the Earth’s crust since the planet was formed. They are also continuously generated by cosmic radiation. In other words, we have been surrounded by natural radioactivity since the dawn of time.
However, we only became aware of our constant exposure to radioactivity 100 years ago, through the research carried out by Henri Becquerel. Gradually, radioactivity’s mechanisms and potential uses became clearer. Today radioactivity has numerous applications, including medical analyses and treatments with radioisotopes, nuclear energy production, non-destructive industrial inspections, environmental studies using radioactive tracers, food and artwork preservation, carbon-14 dating and ionic smoke detectors, to name but a few.

Units of measurement for radioactivity
To measure radioactivity and its effects, three different phenomena must be taken into account: the activity emitted by the radioactive source, the absorbed dose, and the effect of that radiation on the organism or the environment.
The activity of a radioactive source is measured in becquerels, abbreviated Bq. One becquerel corresponds to one nuclear decay per second.
It is in fact a very small unit.
For example, a person who weighs 60 kg has an activity of about 6,000 Bq of radioactive potassium-40 in their skeleton.
The dose absorbed by a target is measured in grays, abbreviated Gy. One gray corresponds to the absorption of one joule of energy by one kilogram of matter (inert or living) exposed to ionizing radiation.
It is used to express high doses, such as those administered in radiation therapy for the local destruction of malignant cells. These doses total tens of grays, which would be a lethal level if it were delivered to the entire body.
The biological effect of a given dose of radiation on a living organism is not a measurable physical quantity. Such effect depends on the energy delivered to the tissues, the type of radiation and the type of tissue concerned. The sievert, abbreviated Sv, is the legal unit of equivalent radiation dose used to quantify this effect. It is defined as a dose of radiation (measured in grays) weighted by dimensionless factors that take its biological effect into account.
The population of France is exposed to an average radiation dose of 3.5 mSv per year.

Human exposure to radioactivity
Based on an evaluation of the radiation sources in France, the country’s population is exposed to an estimated total dose of 3.5 mSv per year, including 2 mSv from natural sources and 1.5 mSv of artificial origin. These figures are averages and can vary according to a number of parameters, such as geographic location.
Natural radiation sources account for about 60% of our total exposure to radioactivity. Most natural radiation is due to radon, a radioactive gas produced by uranium and released by rocks. The remainder comes from telluric radiation emitted by rocks, cosmic rays and the human body’s own radioactivity due to the biological presence of two naturally occurring radioactive elements, potassium-40 and carbon-14.
We are all constantly exposed to natural radioactivity. However, spread out over the days, months and years, its dose rate is low.
Medical analyses and treatments make up 99% of artificial radiation exposure. The remaining 1% is produced by industry, nuclear fallout, nuclear installations and research. It is difficult to reduce these doses other than by improving the equipment involved. Foregoing the examinations and radiation therapy made possible by nuclear medicine would mean turning our backs on the advances of modern medical science.
Even so, radiation is recommended only when its potential benefits outweigh the risks. When radiation is justified, physicians try to use it as efficiently as possible, using a set of Diagnostic Reference Levels (DRL) to limit the doses in relation to the therapeutic goal.
X-ray medical imaging produces the highest levels of human radiation exposure.
However this is not, properly speaking, an example of radioactivity since X-rays are not produced by nuclear reactions but rather by the electronic excitation of atoms.

Fission and fusion
Nuclear energy can be released in two ways: by splitting heavy atomic nuclei, a process called nuclear fission, or by fusing very light nuclei, which is called nuclear fusion.
While controlled fission has long been used for the production of electricity, science has yet to master nuclear fusion, which is difficult to accomplish because it involves the joining of two nuclei that have a natural tendency to repel each other.
In nuclear fission, the nucleus of a heavy atom (a nucleus containing many protons and neutrons, which is the case with uranium and plutonium) splits into two lighter fragments following absorption of a primary neutron. This fragmentation reaction results in the emission of two or three secondary neutrons and in a massive energy release.
Spontaneous fission is an extremely rare phenomenon. For example, for a nucleus like uranium-238, it only occurs once every 2 million decays. The only fissile nucleus found in nature is a uranium isotope (U-235) that is present in very small proportions (0.7%) in uranium ores. There are other fissile nuclei, but they must be produced in reactors. The most commonly used man-made isotopes are plutonium-239 (generated from uranium-238) and uranium-233 (generated from thorium-232).
Fission is most often triggered by the capture of a neutron into a very heavy fissile nucleus made unstable by an excessive number of protons and neutrons. This “overloaded” nucleus then splits into more stable nuclei, releasing energy.
This phenomenon, discovered by Otto Hahn and Lise Meitner in 1938, would have remained relatively insignificant had it not been for the possibility of multiplying it through a chain reaction: the fission releases neutrons that in turn trigger other fission reactions. Under these conditions, nuclear energy is released by considerable quantities of matter rather than just a few isolated atoms.
This chain reaction, which turns into an explosion in an atomic bomb, is controlled in nuclear reactors. The phenomenon of induced nuclear fission was first described by Otto Hahn and Fritz Strassmann on December 17, 1938. In 1939, the chain reaction triggered by neutron emission during fission was discovered by Hans von Halban, Frédéric Joliot and Lew Kowarski in France, and Enrico Fermi in the United States .
Nuclear fusion is a reaction in which two light atomic nuclei join to form a heavier nucleus, for example when a deuterium nucleus and a tritium nucleus fuse to form a helium nucleus and one neutron.
This is the reaction that produces the energy radiated by the Sun, which can reach temperatures of several million degrees.
As of today, there is no man-made device capable of producing energy by controlling nuclear fusion reactions. Researchers are investigating ways to make the energy produced by fusion greater than the energy needed to induce it by heating the atomic particles. An international project called ITER seeks to develop the civil use of nuclear fusion energy to generate electricity.



2 - Nuclear energy
France is the world’s second biggest producer of nuclear electric energy in volume, after the United States, and the first in terms of production per capita. This singular position stems from the country's geological characteristics and from the key role played by French researchers in the discovery of the atom and the understanding of fission mechanisms in the early 20th century. When the oil crisis erupted in 1973, France found itself with no independent access to fossil energy sources, unlike the United States, which had coal, oil and gas, Germany with its coal mines, or the United Kingdom, which had oil and gas from the North Sea. The geographical and political diversity of the world’s uranium sources, combined with easy storage of nuclear fuel on French territory, seemed then —,and may still seem today — to be strong advantages for achieving energy independence in a country with no other resources.
France’s nuclear program, both civil and military, was initiated immediately after World War II. The country’s Atomic Energy Commission was founded in 1945, marking the birth of the French nuclear industry. In 1958, the newly-elected president Charles De Gaulle decided that the country needed to control the entire nuclear cycle. Later, in 1972, president Georges Pompidou gave the go-ahead for the construction of the Pierrelatte uranium enrichment plant at the Tricastin site. It was launched in 1979 and remained operational for 33 years. This plant is now being dismantled. It will be replaced by the Georges Besse II centrifuge separation unit, which will fulfill the same function while also producing as much electricity as two nuclear plants, thanks to its lower energy consumption.
In the 1950s, EDF began operating six natural uranium-graphite-gas reactors, also known as UNGG reactors. This network was gradually phased out from the late 1960s, to be replaced by pressurized water technology, which is still in use today and requires enrichment of natural uranium. France continued to expand its electronuclear infrastructure up until the mid-1990s, eventually reaching the size of 58 reactors across 19 sites.

Now under construction in Flamanville, the EPR (or European Pressurized Reactor) is designed according to the same principles as the reactors currently in operation, but with reinforced safety mechanisms. In 2012, nine reactors were being dismantled in France, including the six of the UNGG network, the first reactor at the Brennilis plant and the two PHENIX and SUPERPHENIX breeder reactors. Their dismantling involves the demolition, processing, evacuation and storage of all the components, including the reactors themselves. The cost of dismantling all 58 reactors now in operation in France has been estimated at €18 billion. This figure is by no means certain, and the actual cost could be two or three times as much. However, a report by the French public audit authority (or Cour des Comptes) in January 2012 indicated that this margin of error has relatively little impact on the cost of nuclear power, amounting to only a few euros per MWh.
The comparison between these production costs and those of other energy sources is often a key point of contention between the pro- and anti-nuclear factions.
Nuclear fuel is another important matter. Besides the fact that France's uranium mines are no longer in operation, the uranium cycle itself is a sensitive issue, even though it is relatively well managed by today’s enrichment and reprocessing plants. The various processes, from the extraction of uranium ore to the reprocessing of spent fuel, are often presented as the stages of a closed cycle, suggesting that uranium, except for the disposal of its final waste, is a renewable fuel. This is both true and false! While the uranium contained in spent fuel can indeed be re-used in a reactor if it is properly re-enriched, this is not possible in France, as the country does not yet have a re-enrichment plant. In addition, the plutonium in spent nuclear fuel can only be recycled once into MOX fuel for pressurized water reactors. A genuine closed cycle, with the multi-recycling of plutonium, is technically possible and could be achieved with fast breeder reactors, as has been demonstrated in the past in plants like PHENIX.
Concerning the storage of long-lived radioactive waste, which accounts for about 3.8% of the volume of all nuclear waste, solutions vary from one country to another. France has opted for storage in deep underground repositories as its system of reference, which is now being tested at the Bure laboratory in the northeastern part of the country. This choice will be the subject of a public debate in 2013. The French nuclear power system is managed by a number of entities in charge of research, plant construction and operation, fuel recycling, the safety of installations, radiological protection, and human and environmental safety, in compliance with both European and international standards.

How does a nuclear power plant work?
A nuclear power plant produces electricity using the heat emitted by the fission of uranium, the mineral that it uses as fuel. Uranium atoms have a heavy, unstable nucleus whose fission is triggered by a collision with a free neutron. This collision results in:
- the splitting of the nucleus into two more tightly bonded nuclei;
- the release of two or three neutrons; and
- the release of energy.
The neutrons thus produced can then interact with other uranium nuclei, continuing the fission process in what is called a chain reaction. In a nuclear reactor, this phenomenon is regulated by control rods that can be used to control the chain reaction in order to vary the power or stop the reactor. Fission can also be controlled through the physical feedback phenomena, which naturally prevent the reaction from going overcritical.
In France, the 58 nuclear reactors in operation are of the PWR type, for “Pressurized Water Reactor.” The enormous quantities of heat produced by uranium fission heat a circuit of water that is kept under pressure. This primary loop heats a secondary circuit of water that transforms into steam and powers a turbine, which in turn drives an alternator. The latter generates an alternating electric current that passes through a transformer, which raises its voltage to facilitate its transmission through very-high-tension lines.
After it leaves the turbine, the steam of the secondary circuit is reverted to water by a condenser cooled with cold water drawn from the sea or a river. This third water circuit is called the cooling circuit. If the water flow in the river is too low, or to avoid draining warm water back into the ecosystem, the water in that circuit can itself be cooled by evaporation on contact with air circulating in tall round towers which are the most visible features of a nuclear power plant.
The three water loops are completely separate and isolated from each other.

The dismantling of nuclear power plants
The dismantling process comprises all of the technical operations undertaken to clean up a decommissioned nuclear installation by eliminating the hazardous substances as well as the structures and equipment that contained them. For a nuclear power plant, this includes the disassembly and processing of all components, including the reactor, and their transfer to a suitable storage site.
In France, EDF is managing the dismantling, now in progress, of its nine industrial reactors that have been permanently shut down: Brennilis, Bugey 1, Chinon A1, A2 and A3, Chooz A, Creys-Malville (SUPERPHENIX) and Saint Laurent A1 and A2.
The dismantling operations are scheduled after the final shutdown and decommissioning phases, which take about 10 years. During the shutdown phase the plant is taken offline, its fuel is removed and its circuits are drained. The fuel is then stored in a spent fuel pit for two years while studies are conducted in preparation for decommissioning.
The decommissioning phase is the point of no return, and must be approved by the government. It consists of disassembling all the equipment and industrial structures that will essentially produce conventional (non-radioactive) waste. This conventional waste is recycled and the nuclear waste is packed in containers and evacuated to suitable storage centers. During this phase, studies are conducted to determine how to proceed with the dismantling in compliance with safety goals. Based on these studies, a new government decree authorizes dismantling, which includes disassembling the reactor building, removing the equipment that is still radioactive, and evacuating the waste to a storage site. The duration of this phase is also estimated at about 10 years, ending with a final decontamination operation. This is followed by the surveys, measurements and impact studies needed to compile the decommissioning report, a process that takes another few years.
The dismantling of the nine French reactors is expected to produce 800,000 tons of conventional waste, which will be recycled, plus 165,000 tons of radioactive nuclear waste.
Once all the dismantling phases have been successfully completed, an installation can be officially decommissioned. It is then removed from the list of nuclear facilities and the site becomes available for other industrial uses. Several other installations are now in the process of being dismantled or decommissioned, including research reactors at the French Atomic Energy and Alternative Energies Commission as well as the reactor jointly operated by CNRS and the University of Strasbourg.
All of these operations are carried out within a strict regulatory framework, in particular in compliance with the so-called “TSN law” on nuclear transparency and safety (N° 2006-686, 13 June 2006).
In France, based on figures provided by the operators (EDF, Areva and the CEA), the Cour des Comptes (public audit authority) assesses the cost of dismantling the 58 reactors currently in operation at just over €18 billion. However, estimates using other countries’ guidelines result in higher figures. Applying international data to the 58 French reactors gives figures ranging between €20 billion according to Belgian guidelines, and more than €60 billion according to German guidelines. A statement issued by the French Nuclear Safety Authority in April 2011 recommended improvements to the methods used to calculate this expenditure. The cost of dismantling a nuclear installation depends on a number of criteria, including the length of the demolition process and whether or not dismantling begins immediately after electrical production comes to a halt.
Several power plants in the United States have already been decommissioned, such as the Maine Yankee site, which was dismantled between 1997 and 2005. The site has been restored, but the long-term storage of its long-lived radioactive waste has yet to be resolved.

The nuclear fuel cycle
The nuclear fuel cycle encompasses all the necessary operations for supplying fuel to a nuclear reactor, and for storing, reprocessing and recycling the spent fuel. Uranium in its natural state contains only 0.7% uranium 235, its fissile isotope, the remaining 99.3% being non-fissile uranium 238. Before it can be used in the pressurized water reactors of France’s nuclear power plants, it must be enriched with uranium 235 to reach a concentration of 4 to 5%. Uranium is enriched in the form of a gas and then transformed into an oxide, a black powder that is then compressed into small pellets weighing about 7g each. These pellets are inserted into metal tubes called fuel rods, which are in turn grouped in fuel assemblies and placed in the core of the reactor.
After it is used to generate electricity in the reactor core (2-6 years), the fuel’s uranium 235 is depleted and must be replaced. At this point, its U-238 has also been converted into plutonium and heavier actinides. The fuel is first transferred to a spent fuel pool, where it remains for a few years to allow the most radioactive short-lived fission by-products to decay. The irradiated fuel is then placed in a storage site to await reprocessing or ultimate disposal in a repository.
Reprocessing nuclear fuel involves mechanical and chemical processes to isolate the various elements in the spent fuel, separating those that are potentially reusable, especially uranium and plutonium, from waste products. Known as ultimate or final waste, these waste products are calcined and then vitrified in an inert matrix in preparation for storage.
In France, a part of the plutonium is recycled into MOX (mixed oxide) fuel, a mixture of uranium and plutonium oxides that can be used in certain reactors and in the future EPR.
The uranium, which still represents 95% of the mass of the spent fuel, is also recyclable — it can be re-enriched and used in certain reactors.
The re-enrichment process requires ultracentrifugation, a technology that is only available at the Seversk plant in Russia and the Urenco plant in the Netherlands. At present, France outsources its uranium enrichment primarily to Russia, pending the completion of the Tricastin site at the Georges Besse II plant, which will house an ultracentrifuge. About 10% of the country’s reprocessed uranium (RPU) is re-enriched, while the remainder is stored. The recycling of part of the spent uranium and plutonium reduces France’s natural uranium needs by about 12% each year.
Countries that have reprocessing plants for nuclear waste include France (at the Hague site), the United Kingdom, Russia and Japan. The US has closed its reprocessing installation for economic reasons. Pro and anti-nuclear factions disagree over the transportation of spent fuel to be reprocessed, that of reprocessed uranium to re-enrichment plants and the risks posed to personnel, the local populations and the environment. Recycling as it is today is not highly cost-effective, since natural uranium can still be obtained at relatively low cost. However, if the use of nuclear power continues to increase around the world, the need for optimal management of natural resources and wastes will require increasingly effective recycling of spent nuclear fuel.

Nuclear waste management
The practical uses of radioactivity — whether in nuclear medicine, research laboratories, military applications, and the electronuclear industry — generate waste that must be disposed of safely.
This waste is characterized by its level of radioactive activity and its duration, which determine how dangerous it is. Four categories have been defined:
- The first two are long-lived high level waste (HLW-LL) and long-lived intermediate level waste (ILW-LL). This is mainly waste from the reactor core that remains strongly radioactive and will retain considerable radioactivity for hundreds of thousands or even millions of years. This waste does not, however, remain “highly radioactive” on a geological scale — it gradually transforms into long-lived low-level waste (LLW-LL). Permanent storage is currently the preferred option in France, where the Parliament will be reviewing all related decisions over the next few years.
- Short-lived low and intermediate level waste (LILW-SL). This is mostly technological equipment (gloves, overalls, tools, etc.) contaminated through use in a nuclear plant.
- Lastly, very low level waste (VLLW), consisting mostly of contaminated materials like scrap metal, rubble and concrete from the dismantlement of a nuclear site. Although it is not strongly radioactive, this waste is expected to generate greater volumes than those of the other categories. The associated management system is already operational, in particular in the ANDRA1 repositories.
For financial and safety reasons, each storage solution must be adapted to the nature of the waste. Due to its level of radioactivity and lifespan, short-lived very low level and low and intermediate level waste does not require deep underground storage. Similarly, long-lived low-level waste can be stored at medium depths, between 15 and 200 meters underground. Deep underground storage, the option that has been chosen by several countries including France, is solely intended for long-lived high and intermediate level waste, which represents about 0.2% of the total volume of radioactive waste.
In France, ANDRA studies and validates this storage method at the Bure underground laboratory in the northeastern part of the country. If the trials are conclusive and the government gives its approval, a deep storage repository will be built nearby, i.e. in a geological layer similar to the one where the studies have been carried out. Nuclear repositories are built in non-seismic areas, in geological formations with very little groundwater (e.g. argillaceous rock or granite).
The concept of deep underground storage is presented as a solution that does not burden future generations with the management of the waste produced today. In the longer term, its supporters argue that underground storage is also a response to a potential breakdown of society in the future. The storage sites are designed to be safe even if they fall into oblivion and are no longer monitored — it is a passive concept where safety does not depend on future generations.
Opponents, on the other hand, believe that burying radioactive waste is not a viable solution, as illustrated by the example of Germany's Asse site in Lower Saxony. This nuclear repository in a former salt mine was infiltrated by water, resulting in the contamination of the surrounding area. Critics also emphasize that a society capable of operating nuclear reactors and managing the associated risks should be able to propose a more reversible waste management solution, with the possibility of benefiting from future technological breakthroughs. They point out that, in any case, the most highly radioactive waste can only be buried after about 70 years of storage above ground, the time needed for its power of decay to subside to a point that it will not cause excessively high temperatures underground.
1 - Agence Nationale pour la Gestion des Déchets Radioactifs (National Agency for the Management of Radioactive Wastes)

Radiological protection
Radiological protection, or radiation protection, encompasses all measures taken to protect people and their environment by preventing or reducing the harmful effects of the ionizing radiation to which they might be exposed, either directly or indirectly.
Radioelements, i.e. atoms with radioactive nuclei, emit radiation that interacts with other matter, possibly ionizing it by removing one or more electrons from its atoms. This is called ionizing radiation.
Ionizing radiation has two types of effects on human health:
- Short-term (or deterministic) effects such as temporary masculine sterility, burns, tissue necrosis, nausea or fatigue;
- Long-term (or stochastic) effects such as cancer and genetic anomalies.
The tissues that are most vulnerable to radiation are the reproductive tissues, those involved in blood cell formation, the skin and the lens of the eye.
The three basic principles of radiological protection, related to the source and regardless of the circumstances of exposure, are:
- Justification: techniques involving ionizing radiation must not be used if there are alternative solutions, unless the benefit to society outweighs the risk;
- Optimization, or what is called the ALARA (“as low as reasonably achievable”) principle: keeping exposure to ionizing radiation to a minimum;
- Dose limitation: legally-defined maximum radiation thresholds per person per year.
There are three main sources of exposure: natural, professional / medical, and environmental due to current or past human activity involving ionizing radiation.
- Natural radioactivity can cause external exposure due to telluric or cosmic radiation, or internal exposure due to radioactive elements in food, drinking water, or the air we breathe (radon gas). In both cases, the radiation is absorbed by the body. The intensity of natural radiation varies from one geographic area to another. In France it averages 2.4 mSv per person per year.
- The medical sector (radiation therapy, radiology), the nuclear industry, research laboratories and many industrial sectors (food preservation, X-ray inspection) use ionizing radiation. The level of exposure is determined by a number of factors, including the type of radiation, the distance from the source, the duration of exposure, the thickness and material of the protective barriers, as well as the possible presence of dynamic confinement systems. The worksites are subjected to regular technical inspections and to measurements of the radiation doses received by the personnel. Operational dosimetry, which measures external exposure in real time, became mandatory in France in 2000 for all personnel working in a controlled zone. It supplements passive dosimetry (with delayed readout), which has been required for all types of restricted zones for the past 30 years. Internal exposure is assessed by measuring isotope levels in urine, feces and secretion samples, or by anthropogammametry (whole body counting). For workers exposed to radiation, the total effective dose, the sum of external and internal exposure, is limited to 20 mSv per year. For the rest of the population, the maximum dose is 1 mSv per year, excluding medical, natural and environmental exposure.
- Environmental exposure associated with human activity primarily concerns the environmental impact of the nuclear industry. In France, it is subject to radiological monitoring by the National Network for the Measurement of Environmental Radioactivity (RMN)). This multidisciplinary network was set up in 2003 in order to respond to societal concerns about nuclear power.

Environmental monitoring and measurements
For environmental monitoring on a worldwide scale, the International Commission on Radiological Protection (ICRP) issues recommendations on the measurement of radiation exposure and safety precautions and standards for sensitive installations. Although not legally binding, the commission’s recommendations are adopted and adapted at the national level. In Europe, the Euratom treaty requires each member state to monitor the levels of environmental radioactivity within its borders, whether it has nuclear power or not. At the international level, the IAEA provides guidance on methods and good practice.
Environmental radioactivity is monitored at two levels: in the immediate surroundings of nuclear installations and also in more remote locations that are not directly affected by these installations, in order to identify any external sources of radioactivity that may affect these areas.
Routine monitoring is carried out regularly by collecting samples of air, water, soil and food, which are then analyzed in the laboratory. In addition, remote monitoring networks measure the radioactivity in the atmosphere and waterways near nuclear installations. The scope and characteristics of these networks vary significantly from one country to another.
In France, inspections and monitoring are performed by the ASN with the technical backing of the IRSN which monitors radiation in France through a network using both sample analyses and continuous monitoring equipment. Other ministerial departments and state services also carry out health inspections on food, livestock raised for food and drinking water.
Each of France’s nuclear sites is subjected to a health and environmental impact study before it goes online. These studies evaluate the consequences of the sites’ radioactive emissions and wastes on the population and the environment. They also help the ASN to set up a regulatory framework for monitoring the environment around each installation as well as its liquid and gas emissions. This system is formalized in a ministerial order that requires operators of nuclear facilities to monitor their waste emissions as well as the environmental conditions both inside and outside the sites.
In order to guarantee the accuracy of the results published, the ASN certifies the laboratories that collect and analyze samples as part of the regulatory measurements of radioactivity. They are the only parties authorized to carry out these measurements, whose results are made available to the public through the RMN (http://www.mesure-radioactivite.fr/public/s-carte.html). Associations like ACRO (Association for Radioactivity Monitoring in Western France) and CRIIRAD have their own laboratories and also carry out inspections and evaluations of the radioecological quality of nuclear sites. In parallel, the CLI (Local Information Commissions), in association with these sites, provide monitoring and information, and also promote public dialogue on nuclear safety, radiological protection and the impact of nuclear activities on people and the environment. The CLIs can commission measurements and evaluations to assess the safety of the installations’ waste emissions.
Another monitoring group, the Becquerel network, was formed by seven laboratories of the CNRS National Institute of Nuclear and Particle Physics (IN2P3) to address concerns about the nuclear industry’s impact on the environment. A national platform for the analysis of radioelements, the network's expertise in the behavior of radionuclides in the environment and in the development of cutting-edge detectors is widely recognized. The network conducts environmental studies on radioecology, the transfer and accumulation of radionuclides in the environmental compartments, and the characterization of the health and environmental risks posed by radioactivity. It also carries out radiological inventories prior to the dismantling of nuclear installations.

Costs of the different electrical production methods
The report of the Cour des Comptes (public audit authority) of January 31, 2012 included a highly detailed evaluation of the costs incurred by the French electronuclear industry in 2010 using various methods. One approach is the current economic cost*, which consists in calculating an overall cost per megawatt hour of electricity produced over the entire operational life of a given production facility. It is used to compare the cost of nuclear power with that of other energy sources, including hydropower, wind, solar, biomass and geothermal plants, as well as natural gas, coal and petroleum.
The problem lies in finding precise, reliable figures on the cost of a megawatt hour for each energy production method. Different sources were consulted, resulting in cost estimates ranging from €20 to €60 per MWh for hydropower, €70 to €85 for onshore wind power, €110 to €200 for offshore wind, €170 to €350 for solar, a consistent rate of €110 for biomass, €62 to €81 for CCG (combined cycle gas) and €44 to €70 for coal. (The latter two estimates do not include the carbon tax, which can increase the cost of a MWh by several tens of euros.)
These figures are estimates, provided as a general indication to allow non-experts to make comparisons. In practice, the actual costs of a given energy source can be double or even triple the estimate, depending on variables such as the load factor for wind turbines or the power output and geographic location of solar panels.
In comparison, according to the 2012 French public audit authority report, the economic cost of a megawatt hour of nuclear-generated electrical power is €49.50.
Taking into account the evolution of the investments needed between now and 2025 for maintenance and post-Fukushima safety upgrades, this figure rises to €54.20.
A debate is underway on whether the calculation of the cost of electricity should include all or part of the past cost of publicly-funded research and development.
The public audit authority estimates the cost of a megawatt hour produced by the Flamanville EPR, France's first nuclear plant of the third generation, at €70 to €90.
For the sake of completeness, it should also be specified that in addition to the production costs for each technology, the service provided to the power grid must also be considered, in particular the guaranteed minimum production and peak capacity reserves. For example, the service provided by a nuclear reactor or gas power plant is not the same as that of a wind farm, whose production is intermittent.
*The current economic cost is an updated calculation taking the following elements into account: initial investments, operating and maintenance costs, investments for upgrades (e.g. replacing large components) and provisions for future costs (waste treatment, dismantling).

Nuclear agencies: Who does what?
1 - In France
The French Nuclear Safety Authority (ASN) is an independent administrative body that monitors civil nuclear activities in France. Each year it submits a report to Parliament on the state of nuclear safety and radiological protection in the country.
The Institute for Radiological Protection and Nuclear Safety (IRSN) is a public research organization on nuclear and radiological hazards. It evaluates the safety procedures implemented by nuclear power plant operators and proposes measures to protect the population in the case of an accident. This institute also contributes to raising public awareness and carries out studies and research projects on radiological and nuclear hazards. Finally, the IRSN is in charge of the radiological monitoring of the French territory and its populated areas.
The High Committee for Transparency and Information on Nuclear Safety (HCTISN) provides information and promotes exchanges and dialogue on the risks associated with nuclear activities.
Areva is a French industrial group (formed from the merger of Framatome, Cogema and Technicatome) in which the government owns a stake exceeding 80%. Its activities focus primarily on nuclear energy, including uranium mining, nuclear fuel production, reactor construction, spent fuel reprocessing, radioactive material transport, nuclear propulsion and nuclear site operation.
ANDRA (National Agency for the Management of Radioactive Wastes) is a government-funded industrial and commercial body entrusted with the long-term management of the radioactive waste produced in France. It operates independently from the waste producers, under the auspices of the government ministries in charge of industry, research and the environment.
The CEA (Atomic Energy and Alternative Energies Commission) is a state-funded industrial and commercial organization involved in four major fields: low-carbon energies (including nuclear power), information and health technologies, large-scale research infrastructures, as well as defense and general security. It is the majority shareholder in Areva.
CNRS (French National Center for Scientific Research) stepped up its involvement in nuclear energy issues after the “Bataille Law” on nuclear waste management was adopted in 1991. Today the organization’s NEEDS program (a French acronym for “Nuclear Energy, Environment, Waste, Society”) brings together the country’s leading academics in the field of nuclear energy, encompassing disciplines such as physics, geology, the humanities and chemistry.
EDF (Electricité de France) is France's main electricity producer and supplier, operating as a state-owned limited liability company.
EDF also buys and sells energy in other countries depending on its needs and production levels.
77.71% of French electricity is generated by nuclear power (source: AIEA – 12 April 2012).
2 – International agencies
The NEA (Nuclear Energy Agency) is the nuclear agency of the Organisation for Economic Co-operation and Development (OECD). Its mission is to help its 30 member countries to develop civil nuclear energy.
The IAEA (International Atomic Energy Agency) is an intergovernmental body under the auspices of the United Nations whose mission is to ensure compliance with the Nuclear Non-Proliferation Treaty and foster cooperation in the peaceful use of nuclear energy.
Euratom, also known as the EAEC (European Atomic Energy Community), is a European public body in charge of coordinating research programs on nuclear energy.

Operation and decommissioning of uranium mines
Uranium, an element found in the Earth’s crust at an average concentration of 3 ppm (parts per million), is extracted primarily from open pit and underground mines, and today more and more commonly by leaching, also called ISR (for in-situ recovery). The financial viability of a deposit depends on many parameters, including the quantity and grade of the ore and the geographic location, geological configuration and depth of the seam(s), as well as environmental, economic and political considerations. Uranium ores can contain concentrations ranging from a few hundred ppm to 195 kilograms of uranium per ton for the McArthur River Mine in Saskatchewan, Canada. Today the most productive mines are located in Canada, Kazakhstan, Australia, Namibia, Russia and Niger. In 2010, those six countries supplied 54% of the world’s uranium production. The fissile isotope U-235, found in natural uranium at a concentration of only 0.7%, is a rare, precious resource.
In France, uranium was extracted between 1945 and 2001 from 210 mines in 25 départements (administrative regions), mostly located in the central part of the country. About 52 million tons of uranium ore were processed over that period, yielding 76,000 tons of uranium.
Because most of France's ore contains very little uranium and is extracted from mines distant from any nuclear site, shipping the ore is not economically viable and it must be processed on site. Mined ore is ground into a fine powder and then chemically treated to dissolve and extract the uranium. In the case of in-situ leaching, an acid solution is injected directly into the ground through a borehole and retrieved through another borehole.
A uranium mine generates many types of wastes: atmospheric emissions (including radon, a highly toxic gas emitted by the ore itself), liquid wastes, solid wastes (sludge, etc.), waste rock containing very little uranium, which is not processed but stored outside the mine, and finally, ores with a low uranium content, which are also stored. Because these different types of waste can contaminate the environment and pose a potential threat to local populations, the entire extraction process must be carefully controlled, as well as the decommissioning of the mines once they are depleted. In France, CNRS laboratories, working in association with the Becquerel network, regularly monitor the levels of radioactivity in the soil and water near uranium mines in order to analyze the risk of groundwater contamination and address the issues linked with waste rock storage. Studies on the management of long-term risks are conducted with the help of CNRS researchers in the humanities and social sciences.
The public is kept informed through France’s Local Information Commissions (CLI), which involve other organizations like the IRSN (French Institute for Radiological Protection and Nuclear Safety) and CRIIRAD (Commission for Independent Research and Information on Radioactivity). IRSN and CRIIRAD also perform their own analyses.

3 - Social aspects of nuclear energy
From the beginning, civil nuclear power has always been promoted as a peaceful form of “clean energy.” Based on a reliable, state-of-the-art technology, it offers a solution for achieving energy independence without petroleum, a limited resource that is found only in certain parts of the world. France chose to develop nuclear power, joining the many other industrialized countries around the world that started building nuclear plants in the 1960s and 1970s.
Then the first accidents began to alter public opinion, casting doubt on the advisability of this choice. In 1979, the nuclear leak at Three Mile Island in the United States highlighted the fact that many plants were located near densely populated areas. In 1986, the Chernobyl catastrophe in the Ukraine (then a Soviet Republic) demonstrated that the consequences of a nuclear incident could extend beyond a country’s borders. And in 2011, the Fukushima disaster showed that accidents are always possible, even in countries known for their technological prowess, like Japan.
Although the risk of nuclear accidents is theoretically very low, they do indeed happen and can have devastating effects, including the contamination of the environment and the evacuation of all the residents of the affected areas, often for an indefinite period of time. These consequences are the subject of in-depth studies, in particular because radioactivity is a phenomenon whose duration far exceeds the human lifespan.
There is also the issue of nuclear waste, for which an acceptable long-term solution must be found. Its effects concern at least several hundred future generations, in addition to the risk of an accident during transportation, which is always a possibility. Of course, many researchers and engineers are working on the safety of nuclear power plants and the management of their waste. Watchdog organizations like the Nuclear Safety Authority in France ensure compliance with standards, which are now the same worldwide. The objective is to reduce the risk of an accident as much as possible, which is mostly an economic consideration based on a cost-benefit analysis.
The Fukushima disaster focused public attention on the nuclear issue once again. The accident in Japan not only raised questions about the safety of nuclear installations but also led to a general rethinking of the relations between the nuclear industry and society. Long imposed as a political choice decided by the government, nuclear energy is opposed by many non-governmental organizations and private citizens. The Japanese have turned strongly against it, and the Germans have followed suit.
Nuclear energy is not just about technology. It is also a social issue that encompasses more than energy independence, economic perspectives and the requirements of sustainable development. The existence and awareness of its risks have an impact on the populations that has never been fully taken into account. For a long time the fear it engenders, whether justified or not, was ascribed to ignorance, and nuclear energy supporters in politics and industry tried in any way they could to influence the population at large, which was considered incapable of conceiving an informed opinion. Without a doubt, this approach had an adverse effect on the public debate for many years. But here again, things changed after the Fukushima accident. In July 2011, the French Academy of Sciences issued an opinion declaring that research on nuclear energy should not be the sole prerogative of the organizations that produce and deploy it, but should be pursued in universities and public research bodies like CNRS. This came as a sweeping endorsement of academic research as a whole, and especially of programs in the Humanities and Social Sciences, independent from the nuclear operators, which could help initiate a true public debate on the issue.

Economic perspectives of nuclear power
A report published on December 15, 2011 by the Parliamentary Mission on "Nuclear Safety, and the Role and Future of the Nuclear Sector" emphasizes that the nuclear industry is an emblem of France’s world-renowned technological know-how and supports tens of thousands of jobs. The paper also highlights the fact that safe energy is essential to ensure the power and independence of the country and its industries.
A report by the French public audit authority published on January 31, 2012, provides a detailed analysis of the costs of the electronuclear industry. The initial public investment is estimated at €188 billion. Today, annual current expenditures for nuclear power total €10 billion for EDF (€8.9 billion in operating costs and €1.1 billion in provisions for spent fuel and long-term waste management) and €644 million for the government (€414 million for research and €230 million in safety, security and public information expenses).
Future costs, which are difficult to estimate at present, are evaluated at €79.4 billion (including €62 billion for EDF). They cover the dismantling of decommissioned power plants and the management of spent fuel and final wastes. Added to this figure are the extra costs of the post-Fukushima safety assessments. Following a report issued in early 2012 by the ASN recommending complementary safety evaluations of priority nuclear installations in light of the accident at the Fukushima Daiichi nuclear plant, EDF has agreed to make the necessary investments.
Also according to the public audit authority, considerable investment will be needed in the short- and medium-term to maintain current production levels, which will inevitably affect the overall cost of electrical production.

The Three Mile Island, Chernobyl, Le Blayais and Fukushima accidents: Causes and lessons learned
Three Mile Island
On March 28, 1979, at the Three Mile Island nuclear power plant in Pennsylvania (USA), a failure of the main feedwater pumps of unit 2 (TMI-2), combined with an erroneous signal indicating that an open relief valve was closed, caused the reactor to overheat. Part of the core melted down, but the reactor building’s containment vessel was not breached and no radioactivity was released into the environment.

Chernobyl
On April 26, 1986, during a safety improvement experiment at the Chernobyl power plant in the Ukraine (then part of the USSR), a series of six critical human errors caused the chain reaction in one of the site’s four nuclear reactors to spiral out of control. The temperature of the reactor core rose, generating enough heat to melt the fuel rods, whose uranium oxide pellets exploded upon contact with the surrounding water. This was followed by the explosion of hydrogen formed by the steam generated by the superheated water. With no containment vessel to protect it, the reactor core was then exposed to the open air and the graphite used to slow the neutrons caught fire. Large amounts of radioactivity were released into the environment in the following 10 days until the fire was finally contained.

Le Blayais
On December 28, 1999, after a storm that caused the Gironde estuary in western France to burst its banks, the basement levels of the Blayais power plant, in particular units 1 and 2, were flooded, incapacitating some of the safety systems. However, the emergency equipment took over and disaster was avoided.

Fukushima
On March 11, 2011, following a Richter scale 9 earthquake in the Pacific Ocean off the northeastern coast of Japan, the reactors at the Fukushima nuclear power plant were shut down and the cooling system was activated. But two hours later, a 15-meter tidal wave overwhelmed sea defenses, which had been built to withstand waves of “only” 5 meters, flooding everything in its path and destroying the plant’s cooling circuits. The temperature of the reactor cores then rose, causing the fuel cladding to melt. Hydrogen formed and exploded, destroying reactor buildings and thus releasing a large amount of radioactivity into the air and sea.

Since the risk of a nuclear plant breakdown is theoretically very slight, each major accident serves as a basis for future improvements.
The Three Mile Island failure had positive repercussions in terms of reactor safety, giving rise to a new safety-oriented culture and leading to improvements at nuclear sites across the world.
The Chernobyl catastrophe provided a real-life lesson for the management of serious nuclear accidents, including communication and public information. While it was quickly blamed on an ageing Soviet regime incapable of ensuring the maintenance of its power plants, it dramatically demonstrated the potential cross-border impact of a nuclear accident. These consequences, which can directly or indirectly affect many different countries — including the most remote — motivated the introduction of the International Nuclear Event Scale (INES ), which, like the Richter scale for earthquakes, is used to assess the severity of nuclear accidents.
The Fukushima disaster, which could have been prevented if, for example, seawalls had been higher, has refocused attention on the need to ensure the safety of nuclear installations even under the most extreme and unlikely conditions. In France, the flood risk at French nuclear sites was re-evaluated and works were initiated to raise the seawalls, following the Blayais plant incident in 1999. In the wake of Fukushima, the French government asked the ASN, its Nuclear Safety Authority, to carry out complementary safety assessments (ECS).

The environmental and human consequences of nuclear accidents
Environmental consequences of nuclear accidents
The environmental consequences of nuclear accidents are difficult to assess. In most cases, the state of biodiversity before an accident is not well known, which means that there is no baseline from which to measure change. After a nuclear accident, the human population is evacuated, but the animals and vegetation remain. The soil and all edible plants growing in it are contaminated for many years. The only serious accident that occurred long enough ago to offer some perspective is the 1986 Chernobyl disaster in the Soviet Union (now Ukraine). Recent studies have revealed that the site is now home to a rich but in some ways unusual biodiversity. Animal species thrive in the area, partly because they have no fear of hunters for lack of human presence in the exclusion zone! The forest in this “no man’s land,” spanning a 30-km radius around the plant, was renamed the “red forest” after the color of the trees, which were severely burned by radiation. Starting in 1987, the Soviet authorities excavated some 900 trenches to bury contaminated plant matter and highly radioactive waste from the ravaged plant under a thin layer of clean sand.
In the past decade, Ukrainian researchers, backed by teams from the CEA, IRSN and CNRS, have observed that in one of the trenches, number T22, some nucleotides (cesium-137, strontium-90 and plutonium) are migrating faster than expected given the site’s physico-chemical characteristics. A microbiological investigation revealed that the phenomenon is probably partly due to bacteria in the soil, some species of which trap radionuclides on their surface (biosorption), while others incorporate them (bioaccumulation). These mechanisms make it possible to immobilize the radioactivity or, through cellular migration, to propagate it.
Microbiological analyses of this type should shed light on the migration of radionuclides in the environment.

Human consequences of nuclear accidents
In the case of a serious accident at a nuclear power plant, the authorities evacuate the neighboring populations to avoid potential exposure to the highly radioactive substances that could be emitted and carried by the air, also contaminating the soil and water. Penetrating the body through breathing, an open wound or the ingestion of contaminated food or water, these particles settle in certain organs, resulting in internal irradiation. For example, radioactive iodine settles in the thyroid and cesium-137 in the muscles and the heart.
If exposure to radiation is especially intense or of long duration, the accumulation of radioelements in the cells is likely to cause cancer. Nonetheless, it remains difficult to evaluate the precise impact of a nuclear accident on the health of local populations.
A 2005 UN-sponsored report on the Chernobyl disaster by the World Health Organization (WHO) and the International Atomic Energy Agency (IAEA) evaluated the number of immediate deaths caused by the accident at fewer than 50, plus 2,200 premature deaths due to radioactivity among the 200,000 most exposed “liquidators” (cleanup personnel). In addition, records show about 4,000 diagnoses of thyroid cancer that can be attributed to the Chernobyl accident among children and teenagers aged below 18 in 1986. Thyroid cancer is rare in that age range and it is safe to presume that these cases were induced by exposure to the radioactive iodine released in the first few days after the accident. However, these figures are the subject of much controversy among the international scientific community and it is difficult, more than 20 years on, to have a reliable estimate of the number of victims of this catastrophe.
Nuclear accidents can also have severe psycho-sociological consequences for the affected human populations, including stress, which can lead to suicide, displaced families losing everything overnight and the fear of contamination. After Chernobyl, many pregnant women in the area had abortions for fear of giving birth to deformed babies.

The time factor in decision-making
One of the problems facing a country in the wake of a nuclear accident is the resettlement of the local population after the immediate evacuation of the contaminated areas.
How long should access to a potentially dangerous sector be banned? The Japanese authorities have begun cleanup operations in the “red zone” covering a 20-kilometer radius around the Fukushima plant, but no one knows when the area’s 110,000 former residents will be allowed back.
At Chernobyl, nearly a thousand evacuated inhabitants returned almost immediately to live illegally inside the 30-kilometer exclusion zone, some literally in the shadow of the plant. These “samosioli” are entirely self-sufficient, preferring a known risk to an imposed exile.
Nuclear energy requires a very long-term political investment and involves decisions whose effects span several decades. It is difficult to go back on such decisions, even after a serious accident like the Fukushima disaster. After taking all its nuclear reactors offline, Japan decided to restart two of them in June 2012, despite public outcry.
Society’s responsibility to future generations is key in the debate on environmental issues, including nuclear power.
In addition to the risk of an accident, the disposal of radioactive wastes — which remain hazardous on a time scale far beyond that of human life — is also a problem. Deep underground storage is being considered. For its proponents, it has the advantage of not burdening future generations with the management of today's waste products. Yet for its opponents, the burial of nuclear waste is not viable over the very long term.

Power plant safety and human safety
Power plant safety
Nuclear power plant safety is an international priority. In France, specific bodies have been established for nuclear risk evaluation. Until 2006, the safety of civil nuclear installations was under state control, but the “TSN law” on nuclear transparency and safety (N° 2006-686, 13 June 2006) advocated the creation of an independent inspection agency, the Nuclear Safety Authority (ASN). One of its branches, the Pressurized Water Reactor Safety Evaluation Department (SEREP) is in charge of all technical procedures aimed at ensuring the safe operation of the country’s 58 PWRs. These were commissioned between 1977 and 1999 at 19 sites, several of which are located in seismic zones.
Safety also has budgetary considerations, and must remain within reasonable limits. It is true that the Fukushima disaster would have been avoided had the seawall been higher, but no one had expected a 15-meter tidal wave.
The safety of a nuclear site is not merely a question of technical reliability — it also depends on the skills and training of its personnel. Many power plants outlive the professional careers of the people who work there, which raises the problem of transmitting the site’s history. In addition, the extreme specialization of job functions and the outsourcing of certain everyday operations are not conducive to the coordinated management of all safety parameters.

Human safety
In the case of an accident at a nuclear site, the plant’s employees are the most vulnerable to radiation exposure. For example, the men who cleared pieces of fuel off the roof at Chernobyl were exposed to maximum doses. Next in the line of exposure are the people who live near the plant, within a radius defined by the authorities (10 kilometers in France). They are made aware of emergency procedures and are given a free number to call for information, as well as iodine tablets to take in the hours following an accident.
The situation for the rest of the population depends on the specific conditions of the accident. Escaped radioactive fallout can form a cloud that drifts to the other side of the planet, or it can be precipitated by rainfall in the immediate vicinity of the plant.
In France, the ASN is active in developing crisis management plans and verifying the emergency alert systems.
The ASN also oversees the transport of radioactive material (spent fuel and nuclear wastes) from power plants to reprocessing and storage sites. Transport safety focuses primarily on the package, which designates the packaging and its radioactive content. Such packages must comply with strict safety standards defined by the International Atomic Energy Agency (IAEA) and enforced in France by the ASN. The packaging itself is subject to a series of regulatory tests, including case-study accidents, prior to certification. These transport packages are designed to protect people (i.e. transport personnel and the public) and the environment, both under normal conditions and if an accident occurs.

Nuclear power and sustainable development
Sustainable development depends on three basic factors: economic, social and environmental.
The primary motivation for choosing nuclear power is economic: it produces relatively inexpensive electricity. As of the end of 2011, 435 reactors were in operation worldwide, generating about 13% of the world’s electricity. France has 58 reactors that supply about 78% of the country’s total electrical production.
In social terms, nuclear power continues to spark controversy. One of the contentious points is EDF’s outsourcing of plant maintenance to external service providers whose employees are exposed to questionable working conditions: financial insecurity and continuous exposure to radioactivity from holding down multiple jobs.
In terms of environment, nuclear power has one oft-cited advantage: it produces very little or no greenhouse gases (GHG). However, this low GHG score does not take into account the uranium mining carried out in other countries, nor the transport of uranium and nuclear waste. In addition, uranium mines are a source of environmental pollution not only when in operation but also for many years after. Another important consideration is that nuclear power is not a renewable energy source: today's PWRs (pressured water reactors) and their immediate successors, the EPRs (European pressurized reactors) use large quantities of natural uranium, a resource that could be depleted in slightly less than 100 years at current consumption rates. Moreover, a permanent solution for the disposal of nuclear waste has yet to be adopted. If they cannot be recycled or eliminated, these radioactive substances will slowly accumulate on the planet.

Public perception of nuclear power and opinion surveys
Public perception
Private citizens generally feel excluded from the decision-making processes behind nuclear power. For many years, the authorities and players in the industry have sought to reassure the public by promoting the “social acceptability” of nuclear power through a variety of communication techniques. These efforts seem to have paid off: in the 1980s, EDF conducted opinion surveys around nuclear sites to measure social tension caused by the presence of a power plant. These showed that public opinion was rather stable and favorable to nuclear power.
But the lack of information on the contamination from the Chernobyl accident triggered strong demand for greater transparency. After the large-scale demonstrations of the 1970s, the anti-nuclear cause lost momentum in the 1980s once France’s nuclearization was completed. After Chernobyl, the movement was revived in the 1990s, as evidenced by the emergence of Sortir du Nucléaire (nuclear phase-out”), a network gathering more than 700 associations.
Opposition has also arisen in the scientific community, with organizations like CRIIRAD (Commission for Independent Research and Information on Radioactivity), which contests the government’s position on nuclear power and conducts its own public awareness initiatives.
Perhaps unexpectedly, the Fukushima accident, the biggest nuclear catastrophe since Chernobyl, has not fuelled anti-nuclear protests in France. A demonstration organized in Paris two days after the first explosion at the Japanese plant drew a mere 300 participants. Unlike some of their neighbors (especially in Germany and Italy), French voters' political choices since Fukushima reflect their acceptance of nuclear energy. In the rest of the world, most of the countries with high-energy consumption (China, India, the US, the UK, Russia, etc.) have also reasserted their commitment to nuclear power.

Opinion surveys
How can one gauge more precisely what the French think of nuclear energy? As in politics, it all depends on who commissions the survey and on the polling institute that conducts it.
According to the most recent European poll (Eurobaromètre, published in March 2010), 45% of those surveyed are in favor of scaling back their country’s reliance on nuclear power, which represents a 6% increase over 2007. According to another survey, commissioned by EDF and conducted by TNS Sofres on March 15-16, 2011, 55% of respondents are not in favor of phasing out nuclear power, and 62% trust EDF to prevent any risk of a nuclear accident in France.
Meanwhile, an Ifop survey for Europe Ecologie-Les Verts (the Green Party) during the same period revealed that 70% of the French would like to see the country put an end to the development of nuclear power and shut down its nuclear plants (19% in the near future and 51% within the next 25 to 30 years).
As part of a survey carried out for the 2012 French presidential campaign, bringing together three research teams specialized in the study of elections, public opinion and political communication, a series of TNS Sofres–TriÉlec polls provided regular assessments of the level of support in France for the ongoing use of nuclear power. The proportion of respondents expressing a favorable or rather favorable opinion rose from 50% in October 2011 to 58% in December 2011, and 61% in February 2012. One year after the Fukushima accident, which prompted several countries to announce plans to abandon nuclear power in response to the public's growing hostility, the French seem to be more favorable to nuclear energy than ever before. This enthusiasm could be due to the media coverage of the events in Japan (which highlighted the safety of France’s nuclear sites and the Japanese authorities’ inept handling of the crisis), perhaps combined with what analysts call “political framing,” with politicians emphasizing the need for nuclear power.

Nuclear energy, the environment, wastes and society: the NEEDS challenge
In 2012, the CNRS Mission for Interdisciplinarity launched the NEEDS challenge (“Nuclear Energy, Environment, Wastes, Society”), a program aimed at coordinating the interdisciplinary effort on nuclear energy, and bringing together academic research on innovative nuclear technologies, energy transition, waste storage and all aspects of the relationship between society, nature and nuclear technology. NEEDS will build on the research conducted since 1997 as part of the CNRS PACEN project (Program on Research Downstream of the Electronuclear Cycle). This national research program was designed to comply with the requirements of laws N° 2005-781 on energy and N° 2006-739 on the management of radioactive waste and materials, as well as decree N° 2008-357 of April 16, 2008 relating to the missions of CNRS, CEA and ANDRA. Involving key partners in the nuclear industry, NEEDS seeks to build on and promote the extensive know-how of the academic world (CNRS and universities) to develop new expertise in fundamental research and bolster relations between the partners, while helping the academic community to devise research programs ensuring an independent analysis of the future of nuclear energy. This analysis should make an enlightened contribution to the public debate on the various aspects of this source of energy unlike any other, including risks, safety, social organization, waste management, technologies of the future, etc.
The NEEDS challenge fosters scientific programs, networks and diversified know-how to advance research on:
• Reducing the quantity of waste, optimizing the consumption of resources and the management of recyclable materials, and improving the safety of nuclear installations;
• Improving waste processing in order to reduce its volume and its environmental impact in the short and long term;
• Improving knowledge of the molecular and macroscopic mechanisms involved in the isolation and immobilization of radionuclides in a porous geological medium, in order to build public confidence in this type of storage;
• Adapting materials to increase their resistance to the extreme conditions of nuclear energy production (temperature, mechanical stress, air- and watertightness, radiation, chemical media, etc.);
• Analyzing the environmental impact in detail by improving understanding of the transfer and accumulation of radionuclides;
• Encouraging research to take recent social, ethical and political changes into account, especially in the new context created by the Fukushima accident;
• Reflecting on the relationship between knowledge, society and democracy.
This highly interdisciplinary program encompasses seven federative projects based on two consortia of expertise.
The federative projects focus on:
1. Nuclear systems and scenarios
2. Waste processing and packing
3. Porous media for waste containment
4. The environmental impact of nuclear activities
5. Resources: mines, processes, economics
6. Humanities and social sciences: nuclear power, risk and society
7. Materials for nuclear energy
The consortia gather experts in: applied mathematics and physical chemistry/radiolysis. At the interface between fundamental and nuclear energy research, the consortia are the link between the core areas of the NEEDS program, jointly supervised by CNRS and its partners, and CNRS researchers who are busy developing applications beyond the realm of energy.

4 - New production, reprocessing and storage technologies
In France, nuclear energy accounted for about 78% of the country’s total production of electricity in 2011. In May 2012, France’s newly-elected president promised to reduce this proportion to 50% by 2030. In parallel, some experts have proposed scenarios for the complete discontinuation of nuclear power by 2033. In short, the future of the French electronuclear industry is unclear. The same is true around the world, as some populations reconsider their dependence on nuclear power in the aftermath of the Fukushima disaster. Still, one thing is certain: regardless of any future energy choices, the nuclear industry must continue to innovate — in order to improve the safety of its installations, its supply of raw materials, the reprocessing of its spent fuel and the long-term storage of its final wastes. In short, to be ready for the future, whatever it might bring.

80% of the nuclear installations in France will be over 30 years old by 2017. Their renewal is becoming urgent. This is why France is now building its first so-called third-generation reactor, the EPR, at the Flamanville site. Although the EPR uses the same technology as reactors from previous generations, its safety improvements represent a strong argument in its favor. Indeed, in the post-Fukushima world, third-generation nuclear plants could become the standard over the next few decades.

But nothing is written in stone, particularly because the fate of the nuclear industry is also linked to the world’s uranium supply, which in turn is influenced by the evolution of the international nuclear infrastructure. On the basis of the current number of reactors, the uranium resources should be enough to meet demand for the next 200 to 400 years. On the other hand, if the number of reactors worldwide quintuples by 2050, which the experts see as a definite possibility, the nuclear power industry could run out of uranium before the end of the century.
To soften the blow of a possible shortage, and simply to help prevent tensions on the uranium market, the 13 partners of the Generation IV International Forum (Argentina, Brazil, Canada, China, South Korea, Russia, France, Japan, South Africa, Switzerland, the United Kingdom, the United States and the European Union) have agreed to work towards the deployment of fourth-generation nuclear plants by 2040. Their primary advantage is that, unlike previous-generation reactors, which run almost exclusively on uranium 235 (an isotope that makes up only 0.72% of natural uranium), Generation IV makes use of uranium 238 — which accounts for more than 99% of the composition of natural uranium — or thorium, another radioactive element that is found in abundance in nature. Out of 120 proposed concepts, the Generation IV Forum selected six solutions, at least one of which could well replace the current uranium 235-based nuclear technology before the year 2100.

Looking beyond this fourth generation of fission reactors, fusion is the main focus of nuclear experts. For the moment, the process exists only on paper, and even the most optimistic observers do not expect to see a functional fusion reactor for at least another 40 years. But in principle, it offers the possibility of cleaner, safer nuclear energy that would be as sustainable as Generation IV. For the proponents of fusion, this prospect justifies the colossal resources being deployed in the hope of perfecting the technology one day — to the point that some even envisage the possibility of bypassing Generation IV, switching directly from Generation III to fusion. That said, Generation IV also has the advantage of providing a solution — albeit partial — to the question of nuclear waste, and within a much more foreseeable timeframe than that of fusion. Because they use high-energy neutrons, fourth-generation reactors would presumably be able to “incinerate” some of the most problematic nuclear waste, namely the high-activity long-lived radioactive substances, primarily minor actinides.

Meanwhile, the transmutation of these actinides, despite being the focus of much research, does not seem to be the most promising solution for “getting rid of” nuclear waste at this stage. This is why France, along with many other countries, favors the option of deep underground storage. Should this solution be approved and adopted, no radioactive materials will be buried before 2025, but this will require close monitoring for at least 100 years — further proof that latest-generation nuclear technologies are more topical than ever!

EPR: Renewing the nuclear infrastructure
Just like the previous generation of nuclear power plants, the EPR (European Pressurized Reactor) is a pressurized water reactor. Power is generated in a core filled with water at a pressure of 155 bars, in which rods of enriched uranium (containing 3 to 5% uranium-235) are exposed to an intense flow of neutrons. This causes uranium to fragment, releasing more neutrons — sustaining the chain reaction — and energy. This energy heats the water, and both are evacuated to produce steam that powers a turbine used to generate electricity.
In terms of technology, the EPR is not significantly different from the existing facilities. Yet it has been the subject of much debate: while its promoters emphasize its very high degree of safety due to greater impermeability and reinforced backup systems for protection in the case of an accident, its detractors agree that the system is too complex. Its direct rival, the American AP-1000, offers a more streamlined design and simpler build. In addition, even if the EPR could become the standard in terms of safety in the post-Fukushima world, some observers feel that it is too early to switch to third-generation reactors. They argue that it would be better to wait for the fourth generation, while continuing to operate second-generation reactors, the most recent of which are sometimes considered to be generation III reactors.
Two EPRs are under construction in China, another in Finland and a fourth in France, at the Flamanville power station. Scheduled for launch in 2016, its cost amounts to €6 billion, or twice the original budget.

Fast reactors: A new horizon for nuclear power?
A nuclear reactor capable of producing its own fuel? It’s not science fiction, but the principle of the breeder reactor, also called fast-neutron reactor. Like other reactors, it produces energy in a plutonium core, but some of the neutrons emitted in the fission reactions are used to bombard the uranium-238 (the most abundant uranium isotope) present in the fuel, transmuting it into uranium-239, then neptunium and ultimately into plutonium.
Several breeder reactor concepts were selected by the Generation IV International Forum, but the most advanced is indisputably the sodium-cooled fast reactor. As the name suggests, it uses sodium as a coolant to transfer heat from the reactor. The same principle was used in the two CEA and EDF PHENIX and SUPERPHENIX breeder reactors, which were decommissioned in 2009 and 1998 respectively. The Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID), an experimental breeder reactor that could go online in 2020, is also sodium-cooled.
Does this mean that sodium-cooled fast reactors are the future of nuclear power? Some critics point to their daunting complexity, in particular the difficulty of using sodium, a liquid so volatile it ignites upon contact with water and air. There is no guarantee that this type of reactor could be made safer than an EPR, but it could nonetheless become viable should uranium become scarcer and therefore more expensive. For this reason, many countries are taking an interest in sodium technology. Another alternative would be the development of gas- or lead-cooled fast reactors, although these technologies are much less advanced.

Will thorium ever replace uranium?
In the public mind, the future of nuclear power is immutably linked to uranium. But in fact, nuclear energy can also be produced through another element: thorium, which could be used for example in molten salt reactors (MSR). This technology means that the fuel is liquid, instead of being solid as in a “traditional” nuclear reactor. This makes it easier to adapt the quantity of fissile material in the core as necessary, and in compliance with safety requirements. In the case of an emergency, a thorium reactor can be drained very quickly.
Besides thorium, a molten salt reactor could possibly run on plutonium and natural uranium, but calculations indicate that it would be difficult to breed the fuel, and there is doubt as to the solubility of plutonium. Although no energy-producing thorium reactor has yet been built, the concept was seriously considered by the specialists at the Generation IV International Forum: thorium was included in the list of six possible solutions for the fourth generation of nuclear reactors, one of which could succeed the EPR generation.
Another advantage of a thorium reactor is that it burns everything. Unlike the other fourth-generation reactors, it could be used to incinerate the transuranic wastes of existing nuclear facilities. Similarly, it could incinerate its own wastes at the end of its service life, along with those of the other generation IV reactors. Besides, abundant quantities of thorium can be found in nature.
China has taken a particular interest in this technology and intends to build on thorium reactor research, much of which was pioneered by French teams. Meanwhile, with less than a dozen specialists still investigating the subject, France seems to have abandoned this solution, at least for the time being.

Nuclear Fusion
Nuclear fusion has become a laboratory joke: “Fusion is the energy of the future — and always will be!” All jokes aside, two facts are noteworthy. Unlike fission, which consists of splitting the nuclei of heavy elements like uranium, the energy produced by fusion is the result of light nuclei merging to form a heavier atom and releasing high-energy particles in the process. This reaction has numerous advantages: it involves light atoms, in particular hydrogen isotopes like deuterium, which is found naturally in seawater; it produces virtually no hazardous waste. Furthermore, the process is so delicate that it is physically impossible for a fusion reactor to spiral out of control.
Secondly, in nearly 60 years of research, no one has yet been able to master nuclear fusion. This is not surprising, considering that it involves controlling a deuterium-tritium gas heated to 150 million degrees (10 times the temperature at the core of the Sun, which transforms the gas into a plasma) and levitated by a magnetic field partially generated by the plasma itself. The process would require materials capable of withstanding temperatures that have never been attained on Earth as well as extremely intense flows of very fast neutrons. Lastly, fusion requires the production of tritium, an element that does not exist in nature, from lithium bombarded by neutrons generated by the reactor itself.
As of 2027, the experimental ITER reactor, under construction at the CEA’s site at Cadarache in southeastern France, will enable specialists to start learning how to control the stability of a fusion plasma. Even so, this colossal €15 billion installation is only the first step towards viable nuclear fusion. The next phase is scheduled to start in Japan in 2033, with another experimental reactor called DEMO, and then with PROTO, the first prototype of what could become an industrial fusion reactor. Only then, provided all these projects come to fruition, will fusion be considered the future of nuclear power.

GUINEVERE: Toward the transmutation of nuclear waste
Among the wastes produced by the nuclear industry, the most problematic are the minor actinides. In addition to contributing to the release of thermal energy by the irradiated fuel, some of these minor actinides remain radioactive for thousands of years. A possible solution for processing these by-products is transmutation — in other words, transforming them into elements that are less radioactive and/or have a shorter half-life. The development of a nuclear reactor specially designed to “incinerate” actinides could make this a reality.
Researchers at the SCK-CEN nuclear energy research center in Belgium, in cooperation with CNRS and CEA, have developed GUINEVERE, a rather unusual reactor, since it is driven by a particle accelerator. With a so-called subcritical core, the reactor is incapable of maintaining a nuclear chain reaction by itself, so an external accelerator supplies the extra neutrons needed to sustain the fission reactions.
GUINEVERE is a research model that produces no significant power, but allows researchers to develop monitoring procedures for future accelerator-controlled systems like MYRRHA, a medium-power reactor that could become operational by 2023. Truly enough, France’s law on the sustainable management of radioactive materials and wastes, which was passed in 2006, does not allow for transmutation before 2040, if this option is chosen. But by then, if all goes according to plan, the advances made possible by the GUINEVERE and MYRRHA systems will have demonstrated the feasibility of the concept.

The geological storage of nuclear waste: A long-term solution?
The French law passed in 2006 on the sustainable management of radioactive materials and wastes establishes storage in deep geological formations as the reference solution for the “permanent disposal” of high-activity long-lived radioactive waste. In 2000, France opened an underground laboratory in Bure (northeastern France) to study the feasibility of this solution, and in particular the confinement properties of clay deposits 500 meters below ground. In a report submitted to the government in 2005, the ANDRA (National Agency for Radioactive Waste Management) concluded that this option was indeed viable.
Should this type of disposal be approved following a public consultation scheduled for 2013, the first radioactive “parcels” could be buried at the Bure site in 2025. According to the researchers, the containers protecting the vitrified nuclear waste will be able to withstand corrosion by moisture for around 1,000 years. After that point, underground water will begin to corrode the vitrified waste, but so slowly that it will take 100,000 to 200,000 years for radioactive elements to be released into the clay deposits. Even then, radioactivity is expected to diffuse very slowly in the clay.
As there are still scientific uncertainties, there is no plan to permanently seal the underground storage galleries of the Bure site before 2125, which should provide enough time to opt for a different solution if necessary. Even so, it seems fairly obvious that it will be impossible to guarantee continued awareness of these contaminated sites from generation to generation over hundreds of thousands of years. By way of comparison, we no longer understand the meaning of the megaliths at Stonehenge, which were erected a mere 5,000 years ago. Nonetheless, burying nuclear waste is currently considered to be the “least worst” solution.


CNRS    sagascience