carbon fibre

Recycling carbon fibre composites: a difficult task

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Carbon fibre composite materials are increasingly widespread, and their use continues to rise every year. Recycling these materials remains difficult, but is nevertheless necessary at the European level for environmental, economic and legislative reasons. At IMT Mines Albi, researchers are working on a new method: vapo-thermolysis. While this process offers promising results, there are many steps to be taken before a recycling system can be developed. 

 

The new shining stars of aviation giants Airbus and Boeing, the A350 and the 787 Dreamliner, are also symbols of the growing prevalence of composite materials in our environment. Aircraft, along with wind turbines, cars and sports equipment, increasingly contain these materials. Carbon fibre composites still represent a minority of the composites on the market — far behind fiberglass — but are increasing by 10 to 15% per year. Manufacturers must now address the question of what will become of these materials when they reach the end of their lives? In today’s society, where considering the environmental impact of product is no longer optional, the recycling issue question cannot be ignored.

At IMT Mines Albi, scientific research being carried out by Yannick Soudais[1] and Gérard Bernhart[2] addresses this issue. The researchers in polymer and materials chemistry are developing a new process for recycling carbon fibre composites. This is no small task, since it requires separating the fibre present in the form of a textile or unidirectional filaments from the solid resin polymer that forms the matrix in which it is plunged.  Two main processes currently exist to try to separate the fiber from the resin: pyrolysis and solvolysis. The first consists of burning the matrix in an inert nitrogen atmosphere in order to avoid burning part of the fiber. The second is a chemical method based on solvents, which is very laborious, because it requires high temperature and pressure.

The process developed by the Albi-based researchers is called  “vapo-thermolysis” and combines these two processes. At present, it is one of the most promising solutions in the world to move toward the wide-scale reuse of carbon fibres. Besides Albi, only a handful of other research centers in the world are working on this topic (mainly in Japan, China and South Korea). “We use superheated water vapor which acts as a solvent and induces chemical degradation reactions,” explains Yannick Soudais.  Unlike with pyrolysis, there is no need for nitrogen. And compared to the traditional chemical method, the process takes place under atmospheric pressure. In short: vapo-thermolysis is easier to implement and master on an industrial scale.

After recovery, reuse

The simplest way to reuse carbon fibres is to spread out the bundle of interlinked fibres on a flat surface and reuse it in this form, as a carpet. They will therefore be used to make composites for decorative parts rather than structural parts. The size of the recovered fibres can also be further reduced to be used as reinforcements for polymer pellets. This approach makes it possible to produce automobile parts using injection, for example. Demonstrations illustrating this type of reuse have been carried out by the researchers in collaboration with the Toulouse-based company Alpha Recyclage Composites (ARC).

But the real challenge remains being able to reuse these fibers for higher-performance uses.  To do so, “we have to be able to make spun fibers from short fibres,” says Gérard Bernhart. “We’re carrying out extensive research on this topic in partnership with ARC because so far, no one in the world has been able to do that.” These prospects involve techniques specific to the textile industry, which is why the researchers have formed a partnership with the French Institute of Textiles and Clothing (IFTH). For now, the work is only in its exploratory stages and focuses on determining technologies which could be used to develop reshaping processes. One idea, for example, is to use ribbed rollers to form homogenous yarns, then a card to create a uniform voile, followed by a drawing and spinning stage.

For manufacturers of composite parts, these prospects open the door to more economically-competitive materials. Of course, recycling is an environmental issue and certain regulations establish standards of behavior for manufacturers. This is the case, for example, for automobile manufacturers, who must ensure, regardless of the parts used in their cars, that 85% of the vehicle mass can be recycled when it reaches the end of its life. But mature, efficient recycling processes also help lower the cost of manufacturing carbon fibre composite parts.

When the fibre is new it costs €25 per kilo, or even €80 per kilo for fibres produced for high-performance materials. “The price is mainly explained by the material and energy costs involved in fibre manufacturing,” says Gérard Bernhart. Recycled fibres would therefore lead to new industrial opportunities. Far from being unrelated to the environmental perspective, this economic aspect could, on the contrary, be a driving force for developing an effective system for recycling carbon fibres.

 

[1] Yannick Soudais is a researcher at the Rapsodee laboratory, a joint research unit between IMT Mines Albi/CNRS
[2] Gérard Bernhart is a researcher at the Clément Ader Institute, a joint research unit between IMT Mines Albi/ISAE/INSA Toulouse/University Toulouse III-Paul Sabatier/CNRS

 

cerveau, brain

Imaging to help people with brain injuries

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People with brain injuries have complex cognitive and neurobiological processes. This is the case for people who have suffered a stroke, or who are in a minimally conscious state and close to a vegetative state. At IMT Mines Alès, Gérard Dray is working on new technology involving neuroimaging and statistical learning. This research means that we can improve how we observe patients’ brain activity. Ultimately, his studies could greatly help to rehabilitate trauma patients. 

 

As neuroimaging technology is becoming more effective, the brain is slowly losing its mystery; and as our ability to observe what is happening inside this organ becomes more accurate, we are opening up numerous possibilities, notably in medicine.  For several years, at IMT Mines Alès, Gérard Dray has been working on new tools to detect brain activity.  More precisely, he is aiming to improve how we record and understand the brain signals recorded by techniques such as electroencephalography (EEG) or infrared spectroscopy (NIRS). In partnership with the University of Montpellier’s research center EuroMov, and Montpellier and Nîmes University Hospitals, Dray is putting his research into application in order to support patients who have suffered heavy brain damage.

Read on I’MTech Technology that decrypts the way our brain works

This is notably the case of stroke victims; a part of their brain does not get enough blood supply from the circulatory system and therefore becomes necrotic. The neurons in this part of the brain die and the patient can lose certain motor functions in their legs or arms. However, this disability is not necessarily permanent. Appropriate rehabilitation can mean that stroke victims regain a part of their motor ability. “This is possible thanks to the plasticity of the brain, which allows the brain to move functions stored in the necrotic zone into a healthy part of the brain,” explains Gérard Dray.

Towards Post-Stroke Rehabilitation

In practice, this transfer happens thanks to rehabilitation sessions. Over several months, a stroke victim who has lost their motor skills is asked to imagine moving the part of their body that they are unable to move. In the first few sessions, a therapist guides the movement of the patient. The patient’s brain begins to associate the request for movement to the feeling of the limb moving; and gradually it recreates these neural connections in a healthy area of the brain. “These therapies are recent, less than 20 years old,” points out the researcher at IMT Mines Alès. However, although they have already proven that they work, they still have several limitations that Dray and his team are trying to overcome.

One of the problems with these therapies is the great uncertainty as to the patient’s involvement. When the therapist moves the limb of the victim and asks them to think about moving it, there is no guarantee that they are doing the exercise correctly. If the patient’s thoughts are not synchronized with their movement, then their rehabilitation will be much slower, and may even become ineffective in some cases. By using neuroimaging, researchers want to ensure that the patient is using their brain correctly and is not just being passive during a kinesiotherapy session. But the researchers want to go one step further. By knowing when the patient is thinking about lifting their arm or leg, it is possible to make a part of rehabilitation autonomous.

“With our partners, we have developed a device that detects brain signals, and is connected to an automatic glove,” describes Gérard Dray. “When we detect that the patient is thinking about lifting their arm, the glove carries out the associated movement.” The researcher warns that this cannot and should not replace sessions with a therapist, as these are essential for the patient to understand the rehabilitation system.  However, the device allows the victim to complete the exercises in the sessions by themselves, which speeds up the transfer of brain functions towards a healthy zone.  Like after fracture, stroke patients will often have to go through physiotherapy sessions both at the hospital and at home by themselves.

Un gant connecté à un système de détection de l'activité du cerveau peut aider à la rééducation post-AVC.

A glove which is connected to a brain activity detection system can help post-stroke rehabilitation.

 

The main task for this device is being able to detect the brain signals associated with the movement of the limb.  When observing brain activity, the imaging tools record a constellation of signals associated with all the background activities managed by the brain. The neuronal signal which causes the arm to move gets lost in the crowd of background signals.  In order to isolate it, the researchers use statistical learning tools. The patients are first asked to carry out guided and supervised motor actions, while their neural activity is recorded. Then, they move freely during several sessions, while being monitored by EEG or NIRS technology. Once sufficient data has been collected, the algorithms can categorize the signals by action and can therefore deduce, through real-time neuroimaging, if the patient is in the process of trying to move their arm or not.

In partnership with Montpellier University Hospital, the first clinical trial with the device was carried out on 20 patients. The results were used to test the device. “Although the results are positive, we are still not completely satisfied with them,” admits Dray. “The algorithms only detected the patients’ intention to move their arm in 80% of cases. This means that in two out of ten times, the patient thinks about doing it without us being able to record their thoughts using neuroimaging.” To improve these detection rates, researchers are working on numerous algorithms which categorize brain activity.  “Notably, we are trying to couple imagery techniques with techniques that can detect fainter signals,” he continues.

Detecting Consciousness After Head Trauma

The improvement in these brain activity detection tools is not only useful for post-stroke rehabilitation. The IMT Mines Alès team uses the technology that they have developed on people who have suffered head trauma and whose state of consciousness has been altered. After an accident, a victim who is not responsive, but whose respiratory and circulatory functions are in good condition, can be in several different states. They can be in either a total and normal state of consciousness, a coma, a vegetative state, a state of minimal consciousness, or have locked-in syndrome. “These different states are characterized by two factors, consciousness and being awake,” summarizes Dray. In a normal state, we are both awake and conscious. However, a person who is in a coma is neither awake nor conscious. A person is a vegetative state is awake but not conscious of their surroundings.

According to their different states, patients receive different types of care and have different prospects of recovery. The huge difficulty for doctors is being able to identify patients who are awake without being responsive, but whose state of consciousness is not yet gone. “With these people there is a hope that their state of consciousness will be able to return to normal,” explains the researcher. However, the patient’s state of consciousness is sometimes very weak, and we have to detect it using high-quality neuroimaging tools. For this, Gérard Dray and his team use EEG paired with sound stimuli. He explains the process. “We speak to the person and explain to them that we are going to play them a series of signals which have deep frequencies, in between these signals there will be high-pitched frequencies. We ask them to count the high-pitched frequencies. Their brain will react to each sound. However, when they are played a high-pitched sound, their cognitive response will be more important, as these are the signals which the brain will remember. More precisely, a wave called P300 is generated when we are innervated. In the case of the high-pitched sounds, the patient’s brain will generate this wave in an important way.”

Temporal monitoring of brain activity after an auditory stimulus using an EEG device.

 

The patients who still have a state of consciousness will produce a normal EEG in response to the exercise, despite not being able to communicate or move. However, a victim who is in a vegetative state will not respond to the stimuli. The results of these first clinical trials carried out on patients who had experienced head trauma are currently being analyzed. The first bits of feedback are promising for the researchers, who have already managed to detect differences in P300 wave generation. “Our work is only just beginning,” states Gérard Dray. “In 2015, we started our research on the detection of consciousness, and it’s a very recent field.” With increasing progress in neuroimaging techniques and learning tools, this is an entire field of neurology that is about to undergo major advances.

 

catenary catenaries

A mini revolution in railway catenaries

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The decade-long ACCUM project carried out by SNCF, Stratiforme Industries, the Valenciennes Railway Testing Center and IMT Lille Douai has led to the development of a new catenary cantilever system for railways. This advance represents a major change in this field, where equipment has seen little change over the past 50 years.

 

When asked to draw a train on a railway track, odds are that most people would not think to include the poles along the railway. Yet these vertical support structures, placed every 20 to 60 meters along electrified railway lines, are essential for supporting the overhead lines that power the trains. The portion located at their peak, which is responsible for holding the wires, plays an especially crucial role. It is composed of a cantilever system, which must at once support the contact wire at a constant height with centimeter precision (for high-speed lines), and withstand significant mechanical constraints arising from the voltages applied to the wires, while ensuring the electric insulation between the wire and the pole.

A traditional catenary cantilever is made up of numerous parts which take a long time to assemble.

 

The catenary cantilever system is an extremely sensitive piece of equipment which has remained virtually unchanged for a half a century. Composed of some hundred parts assembled to form a triangular metal tube, current cantilevers are a real puzzle to assemble and adjust. “Since the stresses are triangulated on the structure, when an adjustment is made at one location within the system, everything is shifted, and it all has to be adjusted again,” explains Patrice Hulot. An engineer at Lille Douai, he contributes to the ACCUM[1] project, which aims to simplify catenary cantilevers.

Les armements caténaires ACCUM sont en composites, et bien plus simples à monter pour les opérateurs.

The ACCUM catenary cantilevers are made from composites, and are much easier for operators to assemble.

 

This modernization project has been carried out over the last ten years by the SNCF and Stratiforme, a company that specializes in composite materials. In 2019, it culminated in the installation of 50 prototypes on test lines at the Railway Testing Centre (CEF), followed by installations on commercial lines. It represents a revolution for SNCF lines, and offers catenary operators the first in-depth modification of this system in fifty years.

A universal catenary cantilever system

What sets apart the new cantilevers developed through the ACCUM project is that they are composed of a limited number of parts to assemble on site. “Everything is delivered 80% pre-assembled,” says David Cnockaert, project manager at Stratiforme. “And these final components to be assembled make it possible to cover all the different types of post configurations and railways.” Furthermore, these new fittings can be used for 1,500 volt and 25,000 volt lines alike. The flexibility of this system allows it to be described as universal, since it can be adapted to all types of electrification, hence its name –ACCUM, the French acronym for “universal multi-voltage composite catenary cantilever.”

The first systems to be installed demonstrated how easy they are to assemble compared to the previous systems, with the major benefit being the time needed for adjustment and fine-tuning, which represents up to 50% of the total time needed to install or replace cantilevers. This therefore makes it possible to reduce the time required to set up the cantilevers,  significantly increasing the availability of railways during renovation work while reducing installation costs and the duration of work to put in new lines. These results are even more satisfactory since they are only the initial results. “Operators had decades of experience to optimize the installation of the old systems, so the installation of the new cantilevers will clearly take less time in the months and years to come,” says Patrice Hulot.

This innovation has received praise within the industry. The project was rewarded at JEC World in March — the global composite materials show — by an Innovation Award. It should be noted that while, for the moment, the new catenary cantilever has only been implemented on the French railways, this mini revolution in railway equipment has the potential for international success. The SNCF is a global leader in the high speed rail sector, in terms of both rolling stock and infrastructure. Its competitors therefore closely monitor developments in the field. This means that Japan or North Africa could soon be added to the list of future markets for the universal composite catenary cantilever.

 

[1] FUI ACCUM project, co-funded by BPI France and the Hauts-de-France region and accredited by the i-TRANS competitiveness cluster. Project leader: Stratiforme. Partners: IMT Lille Douai, ARMINES, Railway Testing Center (CEF) and the SNCF Network.

 

Civiq

CiViQ: working towards implementing quantum communications on our networks

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Projets européens H2020End 2018, the CiViQ H2020 European project was launched for a period of three years. The project aims to integrate quantum communication technologies into traditional telecommunication networks. This scientific challenge calls upon Télécom Paris’ dual expertise in both quantum cryptography and optical telecommunication, and will provide more security for communications. Romain Alléaume, a researcher in quantum information, is a member of CiViQ. He explained to us the challenges and context of the project.

 

What is the main objective of the CiViQ project?

Romain Alléaume: The main objective of the project is to make quantum communications technologies and, in particular, consistent quantum communications, much better adapted for use on a fiber-optic communications system. To do this, we want to improve the integration, miniaturization, and interoperability of these quantum communication technologies.

Why do you want to integrate quantum communications into telecommunication networks?

RA: Quantum communications are particularly resistant to interception because they are typically based on the exchange of light pulses containing very few photons.  On such a minuscule scale, any attempt to eavesdrop on the communications and therefore measure them will come up against the fundamental principles of quantum physics. These principles guarantee that the system will disrupt communications sufficiently for the spy to be detected.

Based on this idea, it is possible to develop protocols called Quantum Key Distribution, or QKD. These protocols allow a secret encryption key to be shared with the help of quantum communication.  Unlike in mathematical cryptography, a key exchange through QKD cannot be recorded and therefore cannot be deciphered later on. Thus, QKD offers what is called “everlasting security”. This means that the security will last no matter what the calculating power of the potential attacker.

What will this project mean for the implementation of quantum communications in Europe?

RA: The European Community has launched a large program dedicated to quantum technologies which will run for 10years, called the Quantum Technology Flagship. The aim of the flagship is to accelerate technological development and convert research in these fields into technological innovation.  The CiViQ project is one of the projects chosen for the first stage of this program.  For the first time in a quantum communications project, several telecommunications operators are also taking part: Orange, Deutsche Telekom and Telefonica. So it is an extensive project in the technological development of coherent quantum communications, with research ranging from cointegration with classic forms of communication, to photonic integration. Although CiViQ has to allow the implementation of quantum cryptography on a very large scale, it must also outline the prospects for a universal use of communications. This reinforces security of critical infrastructures by relying on the networks’ physical layer.

What are the technological and scientific challenges which you face?

RA: One of the biggest challenges we face is merging classical optical communications and quantum communications.  In particular, we must work on implementing them jointly on the same optical fiber, using similar, if not identical, equipment.  To do that, we are calling on Télécom ParisTech’s diverse expertise.  I am working with Cédric Ware and Yves Jaouen, specialists in optical telecommunications.   The collaboration allows us to combine our expertise in quantum cryptography and optic networks.  We use a state-of-the-art experimental platform to study classical-quantum conversion in optic communications.

More broadly, how does the project reflect the work of other European projects that you are carrying out in quantum communications?

RA: As well as CiViQ, we are taking part in the OpenQKD project. This is also part of the Quantum Technology Flagship.  The project involves pilot implementations of QKD, with the prospect of Europe developing a quantum communications infrastructure within 10 to 15 years’ time. I am also part of a standardization activity in quantum cryptography, working with the ETSI QKS-Industry Standardization Group. With them, I mainly work on issues such as the cryptographic assessment and certification of QKD technology.

How long have you been involved in developing these technologies?

RA: Télécom Paris has been involved in European research in quantum cryptography and communications for 15 years. In particular, this was through implementing the first European network as part of the SECOQC project, which ran from 2004-2018. We have also taken part in the FP7 Q-CERT project, which focuses on the security of implementing quantum cryptography. More recently, the school has partnered with the Q-CALL H2020 project which focuses on the industrial development of quantum communications. As well as this, the project is working on a possible “quantum internet” in the future. This relies on using quantum communications from start to finish, which is made possible by the increase in the reliability of quantum memories.

In parallel, my colleagues who specialize in optic telecommunications have been developing world-class expertise in coherent optical communications for around a decade.  With this type of communications, CiViQ aims to integrate quantum communications, by relying on the fact that the two techniques are based on the same common signal processing techniques.

What will be the outcomes of the CiViQ project?

RA: We predict that there will be key contributions made to experimental laboratory demonstration of the convergence of quantum and classical communications, with a level of integration that has not yet been achieved.  A collaboration with Orange is also planned, which will involve issues regarding wavelength-division multiplexing. The technology will then be demonstrated between the future Télécom Paris site in Palaiseau, and Orange Labs in Châtillon.

Finally, we predict theoretical contributions to new quantum cryptography protocols, techniques involving proofs of security and the certification of QKD technology, which will have an impact on standardization.

nuclear

Nuclear: a multitude of scenarios to help imagine the future of the industry

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Article written in partnership with The Conversation.
By Stéphanie Tillement and Nicolas Thiolliere, IMT Atlantique.

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[dropcap]N[/dropcap]uclear energy plays a very important role in France – where 75 % of the country’s electricity is produced using this energy – and raises crucial questions concerning both its role in the future electricity mix and methods for managing the associated radioactive materials and waste.

But the discussions held as part of the recent Multiannual Energy Plan (PPE) gave little consideration to these issues.  The public debate on radioactive material and waste management set to launch on Wednesday 17 April may provide an opportunity to delve deeper into these issues.

Fifty-eight pressurized water reactors (PWR), referred to as “second generation,” are currently in operation in France and are responsible for producing the majority of the country’s electricity. Nineteen of these reactors, were put into operation before 1981 and will reach their design service life of 40 years over the next three years.

The future of the nuclear industry represents a crucial question, which will likely have a lasting effect on all industry stakeholders  – electricity producers, distribution system operators, energy providers and consumers. This means that all French citizens will be affected.

Imagining the future of the nuclear industry

Investment decisions regarding the electricity sector can establish commitments for the country that will last tens, or even hundreds of years, and this future clearly remains uncertain. Against this backdrop, forward-looking approaches can help plan for the future and identify, even partially, the possible consequences of the choices we make today.

Such an approach involves first identifying then analyzing the different possible paths for the future in order to asses them and possibly rank them.

The future of the nuclear industry includes a relatively wide range of possibilities: it varies according to the evolution of installed capacity and the pace with which new technologies (EPR technology, referred to as “third generation” or RNR technology, referred to as “fourth generation”) are deployed.

Given the great degree of uncertainty surrounding the future of the nuclear industry, research relies on simulation tools;  the “electronuclear scenario” represents one of the main methods. Little-known by the general public, it differs from the energy scenarios used to inform discussions for the Multiannual Energy Plan (PPE). The nuclear scenario represents a basic building block of the energy scenario and is based on a detailed description of the nuclear facilities and the physics that controls them. In practice, energy and nuclear scenarios can complement one another, with the outcomes of the former representing hypotheses for the latter, and the results of the latter making it possible to analyze in greater detail the different paths set out by the former.

The aim of studying the nuclear scenario is to analyze one or several development paths for nuclear facilities from a materials balance perspective, meaning tracking the evolution of radioactive materials (uranium, plutonium, fission products etc.) in nuclear power plants. In general, it relies on a complex modeling tool that manages a range of scales, both spatial (from elementary particle to nuclear power plants) and temporal (from less than a microsecond for certain nuclear reactions to millions of years for certain types of nuclear waste).

Based on a precise definition of a power plant and its evolution over time, the simulation code calculates the evolution of the mass of each element of interest, radioactive or otherwise, across all nuclear facilities. This data can then serve as the basis for producing more useful data concerning the management of resources and recycled materials, radiation protection etc.

Emergence of new players

Long reserved to nuclear institutions and operators, the scenario-building process has gradually opened up to academic researchers, driven largely by the Bataille Law of 1991 and the Birraux Law of 2006 concerning radioactive waste management. These laws resulted in a greater diversity of players involved in producing, assessing and using scenarios.

In addition to the traditional players (EDF and CEA in particular), the CNRS and academic researchers (primarily physicists and more recently economists) and representatives of civil society have taken on these issues by producing their own scenarios.

There have been significant developments on the user side as well. Whereas prior to the Bataille and Birraux Laws, nuclear issues were debated almost exclusively between nuclear operators and the executive branch of the French government, giving rise to the image of issues confined to “ministerial secrecy,” these laws have allowed for these issues to be addressed in more public and open forums, in particular in the academic and legislative spheres.

They also created National Assessment Committees, composed of twelve members selected based on proposals by the Académie des Sciences, the Académie des Sciences Morales et Politiques, and the  French Parliamentary Office for the Evaluation of Scientific and Technological Choices. The studies of scenarios produced by institutional, industrial and academic players are assessed by these committees and outlined in annual public reports sent to the members of the French parliament.

Opening up this process to a wider range of players has had an impact on the scenario-building practices, as it has led to a greater diversity of scenarios and hypotheses on which they are based.

A variety of scenarios

The majority of the scenarios developed by nuclear institutions and industry players are “realistic” proposals according to these same parties: scenarios based on feedback from the nuclear industry.  They rely on technology already developed or in use and draw primarily on hypotheses supporting the continued use of nuclear energy, with an unchanged installed capacity.

The scenarios proposed by the research world tend to give less consideration to the obligation of “industrial realism,” and explore futures that disrupt the current system. Examples include research carried out on transmutation in ADS (accelerator-driven reactors), design studies for MSR (molten salt reactors), which are sometimes described as “exotic” reactors,  and studies on the thorium cycle. A recent study also analyzed the impact of recycling the plutonium in reactors of the current technology, and as part of a plan to significantly reduce, or even eliminate, the portion of nuclear energy by 2050.

These examples show that academic scenarios are often developed with the aim of deconstructing the dominant discourse in order to foster debate.

Electronuclear scenarios clearly act as “boundary objects.” They provide an opportunity to bring together different communities of stakeholders, with various knowledge and different, and sometimes opposing, interests in order to compare their visions for the future, organize their strategies and even cooperate. As such, they help widen the “scope of possibilities” and foster innovation through the greater diversity of scenarios produced.

Given the inherent uncertainties of the nuclear world, this diversity also appears to be a key to ensuring more robust and reliable scenarios, since discussing these scenarios forces stakeholders to justify the hypotheses, tools and criteria used to produce them, which are often still implicit.

Debating scenarios

However, determining how these various scenarios can be used to support “informed” decisions remains controversial.

The complexity of the system to be modeled requires simplifications, thus giving rise to biases which are difficult to quantify in the output data. These biases affect both technical and economic data and are often rightly used to dispute the results of scenarios and the recommendations they may support.

How, then, can we ensure that the scenarios produced are robust? There are two opposing strategies:  Should we try to build simple or simplified scenarios in an attempt to make them understandable to the general public (especially politicians), at the risk of neglecting important variables and leading to “biased” decisions? Or, should we produce scenarios that are complex, but more loyal to the processes and uncertainties involved, at the risk of making them largely “opaque” to decision-makers, and more broadly, to the citizens invited to take part in the public debate?

As of today, these scenarios are too-little debated outside of expert circles. But let us hope that the public debate on radioactive waste management will provide an excellent opportunity to bring these issues to a greater extent into the “scope of democracy,” in the words of Christian Bataille.

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Stéphanie Tillement, Sociologist, IMT Atlantique – Institut Mines-Télécom and Nicolas Thiolliere, Associate Professor in reactor physics, IMT Atlantique – Institut Mines-Télécom

This article has been republished from The Conversation under a Creative Commons license. Read the original article (in French).