Structural Performance Analysis and Modeling Laboratory (LMAPS) is located at the Fontenay-aux-Roses site (Hauts-de-Seine, France). It is affiliated to the Equipment and Structures Assessment Department (SES), part of the Safety Expertise Unit (PSN-EXP) in the Nuclear Safety Division (PSN). Its objective is to better understand and quantify the performance of structures and equipment playing a major role for nuclear safety, whether these installations already exist or are in the design phase.
Background and research themes
Safety analysis continually incorporates feedbacks and is based on the most recent state of knowledge. It can be used either to identify studies and research programs to conduct in order to support safety assessments or to supplement the base of knowledge backing these analyses and thus, to help improving safety. This identification entails a clear definition of the safety improvements to make, the scientific challenges to tackle and the associated time frames.
Throughout its service life, a structure is subjected to the effects of the environment in which it is located. Depending on the nature of the environment considered, a structure will experience different types of events which will influence its mechanical properties. These events can be categorized according to their characteristic time.
Cases of high time constants (dozen years or more) include pathologies which are characterized by a set of physicochemical processes and whose effects will be to modify the structural properties (strength and ductility). Cases of low time constants (a few seconds or less) include earthquakes, explosions or projectile impacts. These actions are likely to cause a significant deterioration in the structure that may even modify its integrity.
Assessing the performance of a structure at a given time or its evolution over time requires the determination of indicators. These indicators are the result of simulations or tests, which are generally conducted on samples or on representative scale models, which means they are riddled with uncertainties. These uncertainties can be linked, first, to the variance between a prediction and an observation – these are known as random uncertainties – and, second, to a lack of knowledge – these are known as epistemic uncertainties. Factoring these uncertainties into the assessment of the structural performance must be grasped in order to be able to obtain a performance assessment which incorporates all available knowledge.
Figure 1. Topic-based approach at LMAPS. © IRSN
Because safety assessment relies on modeling, especially in case of severe accidents, one of the major challenges is to estimate and manage the uncertainties associated with the performance prediction by means of digital simulations. Within this context, verifying and validating the computing models, as well as the error estimators, are of primary importance.
To quantify and verify the structural performance-time evolution, for which an optimal safety level must be ensured, the LMAPS is pursuing a variety of research activities on several topics on which both experimental and numerical work are under way. The following topics can be mentioned:
Better understanding of structural aging:
Collaboration with IRSN units: Department of Radioactive Waste and Transfers in the Geosphere (PSE-ENV/SEDRE), Studies and Experimental Research Department (PSN-RES/SEREX) and Incident and Accident Management Department (PSN-RES/SEMIA)
Better understanding of the behavior of structures under complex loading:
Damage mechanics, discontinuous kinematics based approaches
Multi-physics, multi-scale approaches (mesoscopic, macroscopic)
Soil-structure interaction (especially during earthquakes)
Collaboration with IRSN units: Department of Characterization of Natural Unexpected Events and Sites (PSE-ENV/SCAN), Systems and Risks Department (PSN-SRDS/SSyR), Department of Severe Accidents (PSN-RES/SAG) and Incident and Accident Management Department (PSN-RES/SEMIA)
Structural performance assessment:
Collaboration with IRSN units: Department of Severe Accidents (PSN-RES/SAG) and Incident and Accident Management Department (PSN-RES/SEMIA), Systems and Risks Department (PSN-SRDS/SSyR).
To improve the approaches allowing to assess the performance of complex structures, the LMAPS is involved and contributes in several research topics which pertain to all steps of the performance analysis chain described in Figure 1:
1. Structure/environment interaction for high time constants: Better understand structural aging
ASCET project (OECD/NEA),
ODOBA project (IRSN), CONCRETE consortium, HARVEST project (OECD/NEA)
Reinforced concrete pathologies: identification, understanding of the mechanisms and identification of the mechanical consequences related to the corrosion phenomenon affecting the steel reinforcements located in reinforced concrete members, which appears under the action of aggressive agents, such as chlorides and carbon dioxide.
VERCORS project (EDF), CONCRETE consortium
2. Structure/environment interaction at low time constant: assess the containment capacity of a structure under extreme loading
VULCAIN project (CSTB), MACUMBA project (IRSN)
IRIS project (OECD/NEA)
Earthquake: contribution in experimental programs and model developments, which may be non-linear, to predict in a satisfactory way the behavior of structural components or reinforced concrete structures subjected to an earthquake.
MACUMBA project (IRSN), IRSN-CEA collaborative efforts
3. Structure/environment interaction at two time constants: assess the containment capacity of a structure under extreme loading beyond its initial service life
IRSN-CEA collaborative efforts
4. Performance assessment
Local and global quantities of interest: contribution in the estimation of specific indicators (leak volume, capacity, opening of cracks, etc.).
CONCRETE project, MACUMBA project (IRSN)
The research topics in which the LMAPS is involved are clearly complementary. There are two elementary fields (topics #1 and #2), one integrating field (topic #3) and, finally, one field with applicative target (topic #4).
Figure 2. Research topics in which the LMAPS is involved. © IRSN
The role of LMAPS is to provide responses to the needs that arise from safety analyses, especially in the fields of civil engineering and level 1 and 2 probabilistic safety assessment (PSA) studies. To achieve this objective, the LMAPS conducts targeted support studies which usually last for a few months. To complete these studies, the LMAPS has building models of French nuclear sites and models of some sensitive equipment. The LMAPS ensures these models take into account all available knowledge, which are the crucial tools it needs to perform studies or counter-assessment studies in support of safety analyses. The topics of these support studies can be of several types because they depend on the needs identified. For example, the LMAPS is interested in the following subjects:
Behavior of containments (single- and double-walled);
Behavior of the reactor building under several accident conditions;
Behavior of the equipment access hatch.
Dr Benjamin Richard, head of laboratory: non-linear behavior laws, description of cracking by kinematic enrichment, seismic dynamics
Julien Clément, research engineer: soil-structure interaction, seismic dynamics, fragility
Dr Jacques Jabbour, engineer-researcher: concrete pathologies, accelerated test methods, design of complex experimental campaigns
Dr Sandrine Kevorkian, engineer-researcher: dynamics, impact
Dr Georges Nahas, engineer-researcher: concrete pathologies, reinforced concrete pathologies, accelerated test methods, advanced aging models
Abdelatif Ammar, PhD student (2017-2020, collaboration with Sherbrooke University, Ifsttar)
Chaymaa Lejouad, PhD student (2016-2019, collaboration between CEA, ENS Paris Saclay)
Arnaud Montabert, PhD student (2017-2020, collaboration between ENS,
Arthur Pichelin, PhD student (2017-2020, collaboration with LMDC, Paul Sabatier University)
Aya Rima, PhD student (2018-2021, collaboration between ENS Paris Saclay, CSTB)
Facilities and methods
The LMAPS relies on the resources, skills and equipment of the Nuclear Safety Division (PSN) at the Fontenay-aux-Roses, Cadarache and Saclay sites.
For activities which require IT resources:
Some research of interest to the LMAPS conducted outside the IRSN uses the following tested resources:
Partnerships and research networks
The LMAPS works with a robust network that is nationally and internationally renowned. Within IRSN, most of the PSN Research units collaborate with the LMAPS on topics of common interest.
The LMAPS has the following national partners:
ENS Paris Saclay, Cachan
ENS Ulm, Paris
LMDC (Laboratory for Construction Durability and Materials), Toulouse
CEA (French Sustainable Energies and Atomic Energy Commission), Saclay
IFSTTAR (French Institute of Science and Technology for Transport, Spatial Planning, Development and Networks), Champs-sur-Marne.
LMA (Mechanics and Acoustics Laboratory), Marseille
Université de Pau et des Pays de l’Adour, Pau
Électricité de France (EDF), Framatome
The LMAPS has the following international partners:
Sherbrooke University, Canada
Canadian Nuclear safety Commission (CNSC)
Nuclear Regulatory Commission (NRC)
The LMAPS is a founding member and leader of the CONCRETE consortium which brings together IFSTTAR, LMDC, LMA, LMT Cachan and several IRSN units (PSN-RES/SEREX,
PSE-ENV/SEDRE/LETIS and PSN-EXP/SES/LMAPS).
LMAPS is also deeply involved in different scholarly societies and international organizations: