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Our research

Learn about our research on fourth-generation reactors here.

The Research Institute for Nuclear Systems for Low-Carbon Energy Production (IRESNE) is continuing its research in the field of fast reactors with the objective of validating and maintaining the knowledge acquired in the past so it has the possibility to deploy this technology in the future.

1

Reactor studies

IRESNE is working on the following topics in the field of reactor studies:

• Experimental validation:
  Experimental validation is a prerequisite to being able to deploy representative and predictive physical models in our simulation tools. Experimental data improves the accuracy of these models, making them more reliable. Upstream, we development calculation models and tools based on the experimental data collected, then we conduct experiments to validate these models. The experimental validation under way in the field of fourth-generation reactors aims at:
  
  - Confirming the models developed to simulate sodium-air or sodium-water interactions and sodium fires. These models are needed to understand and then define measures to control these risks while ensuring the safety of facilities working with sodium.
  
  - Experimentally validating neutronic assumptions. This is a fundamental area of research that uses microscopic data (neutron paths in the material and resulting reactions) to determine macroscopic orders of magnitude.
  

• Developing and validating multidisciplinary calculation tools:
  Our experts develop and validate the calculation tools needed to design the future fast reactors, relying on numerous disciplines: neutronics, thermohydraulics and thermomechanics.
  Our physicists, experimenters, numerical analysts, computer scientists, and mathematicians have these skills, which allow them to develop and validate powerful calculation software that are used to develop the new generation of fast reactors.
  

• Pushing the boundaries:
  Strengthened by our scientific breakthroughs and wealth of knowledge on fourth-generation technologies, the teams at IRESNE have been working on pre-conceptual designs of innovative fast reactors such as smaller sodium-cooled advanced modular reactors (AMR).
  

• Multiphysics coupling:
  We still develop multiphysics software within the scope of our continuous optimisation approach to studies and technical progress.
  These tools allow us to collect data and perform calculations between different fields of physics (neutronics, thermohydraulics, chemistry, and mechanics) that help us obtain increasingly more refined and reliable predictions.
  
  

2

Fuel studies for fourth-generation reactors

Our fuel experts strive to constantly improve the performance of different fuels by developing:

• A pre-instrumented fuel pin:
  The teams at IRESNE have designed a fuel pin (metal cylinder with a very small diameter containing nuclear fuel) equipped with instrumentation developed either by our teams or within the framework of international collaboration. This tool is designed to identify the properties of nuclear fuel that cannot be determined directly by characterisation during irradiation or testing. This instrumentation must be robust, resistant to hostile environments (radioactive, extreme heat, opacity, etc.) and provide highly accurate and reliable data.

• Analysis of fluid-structure interactions:
  Teams at IRESNE are tasked with studying the dynamic interactions between a structure and a fluid. These interactions lead to the exchange of energy between the flow and the structure. In some cases, this non-conservative process has a positive stabilising effect. However, it often has an opposite effect by provoking instabilities.
  When a structure is elastic, these interactions lead to what we call “fluid elastic” forces that in turn result in excessive vibrations. Using our hydraulic test platform, we can characterise, model and simulate fluid/structure interactions of fuel assemblies to be able to predict the different possible interactions during reactor operation.
  

• A digital platform devoted to studying nuclear fuel:
  The PLEIADES digital platform is used to study the behaviour of fuels used in all reactor technologies and either uses or develops specific calculation tools for these technologies. First developed and validated by the CEA in the 1990s, the fuel performance code called GERMINAL is constantly being refined and improved by our physicists and mathematicians. This code is used to simulate the thermomechanical behaviour of (U, Pu)O2 mixed oxide fuel under nominal and incident conditions in a fast reactor. In brief, this platform allows us to study the fuel’s response to strain and failure when subjected to mechanical and thermal stresses.
  

• The Phenix data bank :
  The sodium-cooled fast reactor prototype called Phenix located on the CEA Marcoule site is currently being dismantled but during its lifetime, research was conducted on nuclear waste management through experiments on the transmutation of minor actinides that could be implemented in future systems. The experiments conducted in this reactor allow us to collect reliable and invaluable data that is now being used to develop scientific computing tools like GERMINAL. The fuel pins used in these experiments are still being investigated by our experts to collect key data that will help us make progress in innovative nuclear technologies and systems for Generation IV.
  
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3

Reactor structures and components

IRESNE studies nuclear technologies that can operate in a sodium-cooled fast reactor environment.

Its experts also focus their research on reactor structures and components, which must be able to withstand numerous interactions between themselves and other components in the reactor while in service. They must be robust and resistant to the hostile environment in which they are placed. The technologies involved in this type of reactor must take into account new properties, particularly those due to the use of sodium as the coolant.

The institute investigates the feasibility of innovative components and develops instrumentation capable of inspecting structures when immersed in sodium.

• Magnetohydrodynamic pumps:
  Our researchers study magneto-hydrodynamic pump concepts that are compatible with the properties of the metal sodium coolant. These pumps are designed to move the conducting coolant by means of a combined electric and magnetic field. A demonstration pump called PEMDYN was fully designed and tested by our teams on the experimental platform developed to investigate liquid metals.
  

• Heat exchangers:
  Heat exchangers have also been investigated by our scientists. As sodium reacts chemically with water, the steam generator driving the turbogenerator will probably be replaced by a gas conversion system. In this case, the heat from the secondary sodium system is transferred to nitrogen, which under pressure then expands in the turbines, powering them to produce electricity. Sodium-gas heat exchangers represent a veritable breakthrough in this power conversion system, but numerous obstacles must still be overcome, particularly in terms of efficiency.

• Cold traps:
  Cold traps are components specific to SFRs; they are designed to purify liquid sodium through the crystallisation of sodium oxide (Na2O) of sodium hydroxide (NaH). This continuous filtration is needed to remove the impurities that exist in the liquid sodium at the start of reactor operation. These impurities become activated when the sodium flows through the reactor core, thus making the sodium radioactive and therefore rendering maintenance and dismantling operations very complicated. This purification process has undeniable advantages, being very efficient and boasting a high retention capacity. By purifying the sodium, it retains its excellent core cooling properties.

• Effective and robust instrumentation in sodium:
  - Measuring the gas quality in the gas-cover plenum.
  Feedback collected from experimental reactors has shown that it is important to monitor the quality of the cover gas in the plenum. For this reason, IRESNE is developing instrumentation capable of accurately measuring the composition of the elements having accumulated in the top part of the reactor, which is an extremely hostile environment. This instrumentation therefore helps ensure reactor safety.
  
  - Performing measurements in sodium.
  Our experts design clever, innovative solutions to adapt to the specific properties of sodium, e.g. opacity, high temperatures nearing 550°C during operation and 200°C at shutdown. As sodium carries sound well, acoustic instrumentation provides a good way of monitoring the appearance of off-normal conditions during reactor operation (presence of bubbles, sodium boiling, cavitation in the mechanical pumps, gas or water leaks, impacts from migrating objects, mechanical failures, etc.) and of checking the good condition of the reactor structures during shutdown. This instrumentation also makes it possible to identify components or fuel assemblies that require handling.
  
  - Detecting sodium leaks.
  Sodium leaks can have significant consequences on reactor safety. This is why the teams at IRESNE design new devices and enhance patented methods to detect sodium leaks. These new methods specifically aim to significantly reduce the time needed to detect any leaks.
  
  

• Experimentation to improve fourth-generation reactor structures and components:
  Research on SFR structures and components are made possible through experimental validation using our liquid metal testing platform called PAPIRUS. This platform is used to test new technologies intended for fourth-generation reactor designs. Experiments on simulating fluids are also conducted to qualify computer codes whenever this is possible; for instance, water is a good simulating fluid to characterise flows.
  

4

Nuclear safety

Nuclear safety is the overriding concern of all stakeholders taking part in the development and construction of nuclear reactors in France and across the world.

Within the scope of Generation-IV sodium-cooled fast reactors, our safety research focuses on the management of core meltdown accidents and sodium-related chemical risks. The scientists at IRESNE work in various fields:

• Severe accident scenarios
  

• Development of digital simulation tools:
  To study severe accident scenarios and develop innovative, reliable solutions, our experts are developing digital simulation tools to better understand the interactions that can result in accidents and be able to describe the sequencing of different possible scenarios.
  

• Experimentation on model materials:
  Our scientists also conduct experiments with the most developed models thanks to the PLINIUS experimental platform. This platform is devoted to studying severe nuclear reactor accidents by conducting tests between 200 and 3500 K with prototypical simulant corium.
  

• Measuring the displacement of molten fuel material:
  To study the phenomena capable of impacting the nuclear safety of a reactor, we are working on nuclear instrumentation that can be placed in the core to measure the displacement of molten fuel material.