Table of Contents

1-Introduction

The purpose of this report is to summarize the second year of research activity related to Yann Argotti's PhD inside the RISC / ISI group at LAAS-CNRS. This PhD candidate is registered at EDSYS school and INSA Toulouse in "Computer science and embedded systems" specialization track. Claude Baron, RISC / ISI group responsible and Philippe Esteban, member of RISC / ISI group, are co-joint thesis directors. Thesis subject is "Study of Qualimetry essentials applied to embedded software product and organization, with consideration" This second year was the continuity of the first year during which an analysis of the thesis problematic was performed, identifying several road blockers that we started to address mainly from a theoretical point of view. So, this year we began to apply our contributions to qualimetry theory against automotive software development, demonstrating their applicability, interests, and benefits. Moreover, we synthetized the thesis progress over the production of two research papers, one submitted to IEEE Transaction of Software Engineering journal [START_REF] Argotti | Qualimetry Applied to Embedded Software Development: Definition and Approach[END_REF] which was unfortunately rejected, but with some constructive feedback, and one to ERTS 2020 conference [START_REF] Argotti | Quality Quantification Applied to Automotive Embedded Systems and Software[END_REF] which was accepted and then presented on end of January 2020 (see Annex for a copy of both papers).

In parallel, we initiated a new systematic literature review on quality models related to software product, process and project. The goal of this work is to perform a study not only to build a unique and precise landscape of quality models in this field, but also to create the necessary quality model substrate to decide which model(s) we must be using in order to complete the construction of our solution.

Thus, and because this research work is incremental and multi-annual, the next parts of this report are a complement to the 1 st year activity report and cover an update of goals we are targeting for this PhD work, an update of our research work organization and a review of our current achievements before concluding.

2-Updated goals

Since Qualimetry is by definition the quantification of Quality for any object, including process, and considering the technological barriers seen in previous section, the inceptive thesis main goal is to:

Define and evaluate an optimized Quality Model in order to bridge and quantify quality not only for software development (ie requirements, models, source code) but also for software organization, with conformance1 to ASPICE MAN. However, on first year and then on second year, our further study and analysis performed on Qualimetry and quality models required us to refactor slightly and consolidate these originals goals. Indeed, we were able not only to confirm our early statement that there is no obvious solution for quality model for software development and for software organization, but also that there is a misunderstanding about Qualimetry2 [START_REF] Argotti | Quality quantification in Systems Engineering from the Qualimetry Eye[END_REF] and we identified gaps on quality model classification and on decision for the quality model solution to apply/use. Comparison studies we can found in [START_REF] Boukouchi | Comparative Study of Software Quality Models[END_REF], [START_REF] Wadhwa | A Comparative Study of Software Quality Models[END_REF] or [START_REF] Abiud | An analytical comparative analysis of the software quality models for software quality engineering[END_REF] illustrate clearly that fact. Only some work done by Oriol et al. [START_REF] Oriol | Quality models for web services: A systematic mapping[END_REF] including ontology consideration and 51 quality model references open the perspective of a solution. So, to be able to address our main initial goal, we can decompose it into: To help and support these tasks, we are adding a fourth sub-goal that must be achieved in parallel to these ones: this is the creation a unique tool and quality model database. Moreover, that tool will demonstrate that our proposal is viable and usable.

3-Updated organization of research work

Research work is organized into several incremental steps, organized around the goals and sub-goals defined and refined in previous section. Indeed, the first step was to proceed on study and analyze the current concepts and problematics behind the thesis subject. This study was based on a rigorous state of the art, started from the early listed references, on qualimetry, quality quantification, quality models and our fields of interested which are embedded software product and its organization. In addition, and as written in previous section, our analysis concluded on the need to build a precise quality model landscape using a specific taxonomy for quality model and then followed by a need to construct a methodology on decision / oracle to generate optimum quality model solution.

This global approach is acting on the theory field. However, we will need to exercise regularly our findings against the practical field, applying on some specific case studies, such as software product quality models and continuous integration process. These experiments phases will allow us to loop back to correct, consolidate, optimize our taxonomy, decision methodology and then quality model landscape. We are planning multiple back and forth loops between theory and practice field to be able to converge on a suitable and practicable solution. To support also these experiments, we are planning to implement a tool. The research work organization is summarized in Figure 1. We see the various task sequence, the theory vs practice aspects, and their loopback and the tool supporting our overall approach. We can notice that we have completed first task and are currently focusing in parallel on quality model taxonomy (or classification methodology) and decision to reflect work on quality model landscape. Also, we note that due to our current workload, we have to consider delaying the extend metrics study and realization.

4-Current achievements

As indicated in section 1-, our first-year contributions were done mainly from a theorical point of view to qualimetry. So, our first achievements on 2019 were the application of our theory contributions, and more particularly polymorphism ones, against one of our current use cases: automotive embedded software.

(1)

Our first achievement is the successful application of the degree of polymorphism formula (1), introduced by Nei and Li in 1979 [START_REF] Nei | Mathematical model for studying genetic variation in terms of restriction endonucleases[END_REF] in genetic domain, against two well-known quality model standards which are also successively referenced in the successive versions of Automotive SPICE [START_REF]13 / Automotive SIG[END_REF]: ISO/IEC 9126 [START_REF]Part1: Quality Model[END_REF] and ISO/IEC 25010 [START_REF]-Systems and software engineering -Systems and software Quality Requirements and Evaluation (SQuaRE) -System and software quality models[END_REF]. Even if ISO/IEC 25010 is replacing officially ISO/IEC 9126 as standard software product quality model, the degree of polymorphism is indicating that the two quality models are disjoined by ~68% 3 which is not minor differences between the two models. Figure 2 is illustrating some of the differences between these two quality models. An additional achievement linked to that distance formula is our exploration with regards to the impact and benefits of quality model distance. The needs to use or refer to that distance between quality models are associated to a need to evaluate, modify, change or update quality model due to a variety of root causes such as: change of life cycle stage (e.g. from design to implementation), evolution of product (e.g. addition of new features), insufficient quality area coverage (e.g. gaps in safety or security), change of targeted product (e.g. from car to truck), new or updated process or standard (e.g. from ISO/IEC 9126 to ISO/IEC 25010), …. The main benefits are enumerated here: Another application aspect to which we contributed was the design and internal publication of a project scorecard for Renault and Renault Software Labs. This scorecard, showed in Figure 4, is part of Alliance (ie Renault -Nissan -Mitsubishi) SoftWare Process (ASWP). It integrates usage of software product, process and project metrics, includes all metric definitions, "risk vs opportunity" based thresholds and a mapping between each metrics with corresponding ASWP process. Its junction with a quality model is realized thanks to the software product quality indicator which aggregate software metrics accordingly to that quality model. Completing that scorecard, we started the implementation of automatic metrics collection and corresponding graphic generation (ie pie charts, cumulative flow charts and trend charts -see Figure 5) in python language with yaml, jira, matplotlib, numpy and pandas library. On second half of this year, our focus was on the creation of a precise quality model landscape in the fields of software product, process and project. Therefore, to acknowledge the benefit of such effort, we first performed a coarse quality model survey, identifying 196 distinct models with their number of citations within the survey (cf Figure 6) which was much more productive than Oriol et al. [START_REF] Oriol | Quality models for web services: A systematic mapping[END_REF] paper with 51 quality models: that paper is the one with the most important number of cited quality models to our knowledge. In addition, we analyzed that set of quality models, splitting by basic vs standard vs tailored, and per main technology: components (e.g. COTS), web, service, open-source, reuse. The conclusion of our analysis (see Figure 7), also based on citation numbers and the 9 challenges identified by Thapar et al. [START_REF] Thapar | Challenges to the Development of Standard Software Quality Model[END_REF], allowed us to identify an early list of 10 candidate quality models which could be used as a basis for our quality model genome: McCall, Boehm, Dromey, FURPS, ISO 9126, GEQUAMO, Bawane, Alvaro (CQM), Kalaimangal and ISO 25010. To conclude on this section, we would like to highlight that we detailed and promoted part of our contributions with conference presentations and the achievement of two submitted papers. Thus, we presented our last year accepted paper to IEEE International System Conference (SysCon) in April 2019. We submitted a research paper against to IEEE Transaction of Software Engineering journal, with a scope of software engineering. Unfortunately, it was rejected but the reviewers provided some constructive hints to refactor the paper. The second submission this year was done to Embedded Real-Time System (ERTS) 2020, with a scope of embedded systems and software, and contained practical application aspects. That second paper was successfully accepted and presented in the conference. A copy of these two papers is available in the Annex section.

5-Conclusion

In conclusion, like first year, this second year was quite productive in term of contributions and achievements: seven new contributions over which five of them are already acknowledged by peers either by a presented ERTS conference paper or company internal peer reviews and agreements. We note that the scope of our achievements is not only software engineering but also system engineering.

Moreover, we consider having performed a serious step forward in our thesis research work this year. Indeed, it was the first time that we successfully applied our contributions to qualimetry theory against a real use case, and more particularly, the application of our polymorphism concepts to the automotive embedded software.

In our next steps we are going to complete our research work on quality model systematic literature review, taxonomy, genome and then finalize our answer to our thesis subject: "Study of Qualimetry essentials applied to embedded software product and organization, with considerations to software entropy".

1 -

 1 Introduction .................................................................................................................................... 2-Updated goals ................................................................................................................................. 3-Updated organization of research work ......................................................................................... 4-Current achievements ..................................................................................................................... 5-Conclusion ..................................................................................................................................... References ............................................................................................................................................ Annexes ................................................................................................................................................. A-First part of quality model classification and decision tool: get_synonyms.py ........................ B-Journal paper: IEEE Transaction on Software Engineering ....................................................... C-Conference paper: ERTS Conference 2020 ...............................................................................

Figure 1 -

 1 Figure 1 -Current research and development flow ................................................................................ Figure 2 -Few highlighted differences between ISO/IEC 9126 and ISO/IEC 25010 ............................... Figure 3 -Ad-hoc & universal polymorphism applied to Automotive ...................................................Figure 4 -Our project scorecard linked to quality model, process, product and project metrics ..........Figure 5 -Examples of several implemented metric graphics ................................................................Figure 6 -Coarse quality model survey: list of 196 quality models vs their citations ............................Figure 7 -Coarse quality model survey: detail results of our analysis.................................................... Figure 8 -Our four-filter stage publication selection process ................................................................ Figure 9 -Systematic literature review: referenced quality models per publication year ..................... Figure 10 -Systematic literature review: list of the 125 referenced quality models vs their citation numbers .................................................................................................................................................. Figure 11 -Systematic literature review: distribution of quality modeling types ..................................

Figure 2 -

 2 Figure 1 -Current research and development flow ................................................................................ Figure 2 -Few highlighted differences between ISO/IEC 9126 and ISO/IEC 25010 ............................... Figure 3 -Ad-hoc & universal polymorphism applied to Automotive ...................................................Figure 4 -Our project scorecard linked to quality model, process, product and project metrics ..........Figure 5 -Examples of several implemented metric graphics ................................................................Figure 6 -Coarse quality model survey: list of 196 quality models vs their citations ............................Figure 7 -Coarse quality model survey: detail results of our analysis.................................................... Figure 8 -Our four-filter stage publication selection process ................................................................ Figure 9 -Systematic literature review: referenced quality models per publication year ..................... Figure 10 -Systematic literature review: list of the 125 referenced quality models vs their citation numbers .................................................................................................................................................. Figure 11 -Systematic literature review: distribution of quality modeling types ..................................

  6 [3], ISO/IEC 25010[START_REF]-Systems and software engineering -Systems and software Quality Requirements and Evaluation (SQuaRE) -System and software quality models[END_REF], ISO 26262[START_REF]:2011 -Road vehicles -Functional safety -Part 6: Product development at the software level[END_REF] and ISO/TS 16949:2009 [36]. Secondary initial thesis goals are to exercise this quality model and achieve:  Software Maturity within Continuous Integration process measurement o Traceability / Quality by design / Change impact o Test efficiency o Project Landing zone (Time to market vs risk & complexity)  Software Aging measurement o Software Model Aging (e.g. Impact from Maintenance, FOTA and/or Complex system vs impact to safety & reliability) o Product Aging Landing zone

1 -

 1 Build a precise landscape for quality model for software a. Build a taxonomy for quality model, b. Perform a systematic literature review of quality models for software product, process & project, c. Reference and classify found quality models based on our taxonomy, 2-Create a SW product quality model genome a. Build a methodology to create a quality model genome, b. Build a first candidate list of SW product quality models to be used as a 1 st quality model basis as genome creation, c. Identify SW product quality model main genes 3-Define an oracle for decision to get optimum quality model(s) solution, a. Identify key criteria for oracle definition (e.g. Non-Parametric Linkage usage against genome), b. Build a decision oracle for quality model, c. Apply to our case study that oracle to Renault Software Labs use case to generate a basis quality model to be used with polymorphism concept,

4 -

 4 Define and implement a tool to support quality model taxonomy & oracle a. Describe Quality model seen in state of the art (use Yaml for quality model description, pedigree, setup bridge/dictionary of "synonym" =>http://www.atlas-semantiques.eu/?l=EN), b. Apply the computation over the multiple quality model combination, c. Quality model decision helper (oracle?), Thanks to this goal refinement, we can rewrite the first initial secondary goal relying on the taxonomy and oracle studied and developed in our main goal. In addition, we understand that the amount of work required to achieve it may bring risk to not be able to complete on time initial secondary goals. Therefore, the rewritten secondary goals are defined below:  Quality Models and Metrics linked to CI a. Derived oracle identified quality model to ECU covered by CI, b. Apply these derived quality models to CI applicable characteristics and metrics,  Software Aging measurement a. Summarize problematic and difference against regular (ie often associated to reliability) vs our definition of Software Model Aging b. Takes examples: Impact from Maintenance, FOTA and/or Complex system vs impact to safety & reliability, product aging landing zone

Figure 1 -

 1 Figure 1 -Current research and development flow

Figure 2 -

 2 Figure 2 -Few highlighted differences between ISO/IEC 9126 and ISO/IEC 25010

  a. Evaluate risk linked to quality model change (low distance = low risk, high distance = high risk), b. Evaluate change workload and cost, c. Identify most impacted areas and characteristics, d. Identify where quality quantification, assessment and control are changing, e. Identify and evaluate validation path finding change (Capture of different types of bugs possibly never found before, Discard other areas and path) 3 Degree of polymorphism = 0.6792 (0 = identical; 1 = 100% disjoined): 53 leaf characteristics, 32 unique, 8 similar 𝜋 = 𝓍 𝓍 𝜋 f. Support decision and control change / update of quality modelOur next achievement this year concerns the application of ad-hoc 4 and universal 5 polymorphism concept to Automotive quality model product: starting from ISO/IEC 25010, we defined a generic quality model common to all vehicle Electronic Control Unit (ECU), and then deriving it into In-Vehicle Infotainment (IVI) and Body Control Module (BCM) ECU quality models (see Figure3).

Figure 3 -

 3 Figure 3 -Ad-hoc & universal polymorphism applied to Automotive

Figure 4 -Figure 5 -

 45 Figure 4 -Our project scorecard linked to quality model, process, product and project metrics

Figure 8 -Figure 9 -Figure 10 -

 8910 Figure 8 -Our four-filter stage publication selection process

The company, welcoming student here, is in automotive field which therefore drives standard choices here.Main GoalSecondary Goals

In general, qualimetry is understood as "applied qualimetry" and not really as qualimetry as a science. Main Goal: subgoals Main Goal: subgoals Rewritten Secondary Goals

Common quality model characteristics or "interface" (ie Ad hoc polymorphism: overloading & coercion)

Variations with heritage between quality models (ie Universal polymorphism: sub-classing, inheritance, or overriding, extension)

Confidential C

Confidential C

Once our coarse survey completed, we decided to strengthen our survey methodology, and by consequence the results here, by initiating a quality model systematic literature review following Kitchenham and Charter [START_REF] Kitchenham | Guidelines for performing Systematic Literature Reviews in Software Engineering[END_REF] guidelines. This our final achievement for this year. We adapted the guidelines to our needs, setting a four-filters stage to filter digital library raw publication results into a short list of papers to study. That process and results of filtering stage are described in Figure 8. We can already note that we are finding more models (see Figure 9 and Figure 10), especially before 2004 years, than with our coarse study, extending the result time range: the 2 first quality models on 1968 Rubey & Hartwick [START_REF] Rubey | Quantitative measurement of program quality[END_REF] and Shooman [START_REF] Shooman | Probabilistic reliability : an engineering approach[END_REF]. We are also taking into account predictive and statistical quality models (see Figure 11) and during our referencing of each quality model, we are classifying to them across multiple criteria: the 5 quality perspectives of Garvin [START_REF] Garvin | What does 'product quality' really mean?[END_REF], the DAP purpose of Deissenboeck et al. [START_REF] Deissenboeck | Software quality models: Purposes, usage scenarios and requirements[END_REF], citation number (publisher & google scholar) ….

Annexes A-First part of quality model classification and decision tool: get_synonyms.py

This short python program is the first piece of our tool: it makes a web request to www.atlassmeantiques.eu site in order to get a json based result of synonym and their corresponding constellations. The first text box below is an example of screen display of that python script: it looks for "functional" synonym. The second text box is the python script itself. Journal 2019 -Qualimetry applied to embedded SW development_definition and approach -v0.17-06-19.docx


J.-B Sirven

J Picard

C Maury

M El

ISSUES AND ADVANCES OF CALIBRATION TRANSFER IN LIBS

CALIBRATION TRANSFER?

Spectra in conditions 1

Spectra in conditions 2

Calibration model

Adaptation of calibration model

Use for predictions

Use for predictions

  LIBS is an onsite / online / in situ analytical technique | PAGE 2 CEA | Jean-Baptiste Sirven | Issues and advances of calibration transfer in LIBS Image credit: NASA/JPL.  Are we able to switch from a calibration model to another one obtained in different conditions? -Baptiste Sirven | Issues and advances of calibration transfer in LIBS



  only 2 papers explicitly dealing with calibration transfer in LIBS: Lopez-Moreno et al., J. Anal. At. Spectrom. 20 (2005) 1275-12794 Boucher et al., SciX 2015, abstract #287 CALIBRATION TRANSFER IN LIBS When making calibrations lines, this is equivalent to making a slope correction | PAGE 4 CEA | Jean-Baptiste Sirven | Issues and advances of calibration transfer in What does the slopes ratio mean?  Can we predict it?  Are there cases where slopes are equal? 𝐼 𝑖𝑗 = 𝐹 𝑒𝑥𝑝 × 𝐶𝑚 0 -Baptiste Sirven | Issues and advances of calibration transfer in LIBS ablated mass (depends on the matrix) electron temperature (depends on the matrix and on time) spectroscopic data (depend on the analyte and on the spectral line) analyte concentration experimental factor (depends on the geometry and efficiency of the plasma emission collection setup, on the matrix, and on time) (for given experimental and measuring conditions) TRANSFER FROM ONE ELEMENT TO ANOTHER Calibration of metal impurities concentration (Pb, In, Tl) in liquid sodium | PAGE 6 CEA | Jean-Baptiste Sirven | Issues and advances of calibration transfer in LIBS Determination of T e (t) by a multielemental Boltzmann plot based on trace element lines: -Baptiste Sirven | Issues and advances of calibration transfer in LIBS The error bars take into account the uncertainty on T e experimental theoretical Application to the extrapolation of detection limits of elements of interest in a given matrix:  Background noise (measured experimentally on a blank) (x 10 -6 )  Slopes ratio (wrt Pb)  Predicted detection limit (ppm) CAN WE PREDICT THE ABLATED MASS? Experiment: Samples: several pure metals and one alloy (Mn, 316L Stainless Steel, Ta, Pt, Al, Cu) 10 laser shots at 1 bar, 266 nm, irradiance 0-50 GW/cm² (linear regime) The ablation efficiency is the slope of the line Volume = f(Pulse energy) Empirical model between ablation efficiency and physical properties of metals | PAGE 8 CEA | Jean-Baptiste Sirven | Issues and advances of calibration transfer in 𝐿 𝑡ℎ = 2. 𝐷 𝑡ℎ . 𝜏 : thermal diffusion length D th : thermal diffusivity 𝜏 : pulse duration n : real part of the refractive index Very nice correlation between ablation efficiency and some physical parameters of metals… … but not clearly explained… IS IT SUFFICIENT TO CORRECT MATRIX EFFECTS? Normalization of calibration lines by the ablation efficiency | PAGE 9 CEA | Jean-Baptiste Sirven | Issues and advances of calibration transfer in LIBS 0Fe lines ratio I 239,56 /I 238,2 0,78 0,77 0,79 No significant difference  A POSSIBLE EXPLANATION Not that surprising, see e.g. Aguilera et al., Spectrochimica Acta Part B 64 (2009) 993-998: What about the plasma / spectrometer coupling? | PAGE 10 CEA | Jean-Baptiste Sirven | Issues and advances of calibration transfer in LIBS Cu plasma Ta plasma Fe plasma

mm TBC…

Majestic convention center

Welcome ABSTRACT As a fast, direct and remote technique, laser-induced breakdown spectroscopy is particularly relevant for online or in situ analysis, or to measure samples with limited access, like in the nuclear sector or in planetary exploration. In these cases, quantitative analysis can be difficult for different reasons. First, environmental conditions are not completely controlled and instrumental drifts may occur. Secondly, matrix-matched calibration samples are not always available. Thirdly, the samples matrix is known to a certain extent, with a possible high variability that can induce unexpected spectral interferences. In addition, due to practical or cost constraints, feasibility studies are frequently performed on matrices and/or analytes and/or experimental conditions other than that of interest, and the question of analytical performances that would be obtained in the real situation is raised. Calibration transfer could be helpful to cope with those issues. In the field of NIR spectroscopy, where it is widely studied, this concept generally relates to the use of a multivariate calibration model obtained with an instrument to predict samples measured with another instrument. In LIBS, this definition is somewhat restrictive and can be broadened in different ways. Thus, we could consider transferring a calibration from one matrix to another, which is equivalent to compensating for matrix effects. But it can also be related to the calibration transfer for a given matrix from one element to another, or for a given element, from one line to another. Furthermore, a change in experimental conditions can also be dealt with by calibration transfer approaches.

In this talk we will review the interest of calibration transfer in LIBS as well as the existing works on the subject. Recent results obtained in our laboratory will be presented to illustrate the different definitions of calibration transfer given above. Issues and perspectives of such approaches will be discussed.

| PAGE 16 CEA | Jean-Baptiste Sirven | Issues and advances of calibration transfer in LIBS


Thibaut Souilliart

Emmanuel Rigaud

Alain Le Bot

Christian Phalippou

WEAR INDUCED BY STOCHASTIC SLIDING IMPACTS

Vibrations of the steam generator tubes in nuclear power plants induce stochastic impacts between the tubes and their supports. As a consequence, wear is generated. A test rig is designed and used to perform impacts between two metal crossed cylinders with various incidence angles and impact velocities. The normal and tangential components of the contact load are measured during the tests. Rate and duration of impacts, instantaneous ratio between normal and tangential loads for each impact are deduced. Influence of incidence angle and impact velocity on impact duration, ratio between tangential and normal loads during impact and wear volume is highlighted.

INTRODUCTION

Heat exchangers of Pressurized Water Reactor (PWR) are composed of thousands of tubes supported by baffles and Anti-Vibration Bars (AVB). Functional clearances are needed between tubes and bars because of thermal expansion and assembly purposes. In steam generators, tubes are excited by high flow rates. This excitation could lead to a dynamic response characterized by sliding impacts between tubes and AVB and generate wear [START_REF] Phalippou | PWR steam generator tube and AVB wear under perpendicular impacting[END_REF].

For mechanical systems subjected to sliding impacts, several types of wear exist according to the motions and the bodies involved [START_REF] Ko | Metallic wear-a review with special references to vibration-induced wear in power plant components[END_REF]. Sliding impacting is usually studied as an erosive and percussive process which leads to both surface and volume degradation. Surface degradation can be associated with adhesion [START_REF] Bowden | The Friction and Lubrication of Solids[END_REF] (metal transfer due to sheared asperities junctions) and abrasion [START_REF] Rabinowicz | Friction and Wear of Materials[END_REF] (cutting of the rubbing surface by hard asperities). Volume degradation is often described as the formation and propagation of subsurface fatigue cracks in the material (delamination) [START_REF] Suh | The delamination theory of wear[END_REF][START_REF] Rice | Characteristics of metallic subsurface zones in sliding and impact wear[END_REF].

Engel [START_REF] Engel | Impact Wear of Materials[END_REF][START_REF] Engel | Percussive impact wear: A study of repetitively impacting solid components in engineering[END_REF][START_REF] Engel | Impact wear model for steel specimens[END_REF] develops a model to predict impact wear based on surfaces conformance in terms of wear formation and a strong dependence with shear stress concerning wear evolution during time. Levy [START_REF] Levy | Impact fretting wear in CO2-based environments[END_REF] proposes a model based on a proportionality with load and sliding distance during impact. Connors [START_REF] Connors | Flow-induced vibration and wear of steam generator tubes[END_REF], Frick [START_REF] Frick | An empirical wear projection technology with steam generator tube applications and relations to work-rate and wear simulations/tests[END_REF] and Hoffman [START_REF] Hofmann | PWR steam generator tube fretting and fatigue wear phenomena and correlations[END_REF] also propose impact wear models derived from Archard equation. The wear law proposed by Lewis includes both a term derived from Engel model and a dependency with sliding distance [START_REF] Lewis | A modelling technique for predicting compound impact wear[END_REF].

Erosion results from the impact of streams of solid particles on a surface and not from the impact of two macroscopic bodies. Nevertheless, asperities which constitute the contact have a size similar to erosive particles and kinetic energy of the solid impactor and an erosive particle have the same order of magnitude. Therefore, erosive models can be relevant to describe wear of macroscopic bodies [START_REF] Rigaud | Influence of incidence angle on wear induced by sliding impacts[END_REF][START_REF] Kaiser | Wear damage resulting from sliding impact kinematics in pressurized high temperature water: energetical and statistical approaches[END_REF].

An experimental work is performed in order to confirm this hypothesis and to highlight influence of test parameters on wear volume. The first section presents the test rig that have been designed and used to generate impacts with various incidence angles and velocities. Load and wear measurement protocols, wear conditions and testing parameters are explained. The second section goes through the obtained impact characteristics in terms of load evolution during impact and generated wear. Experimental results are shown in the third section. Influence of incidence angle and impact velocity on impact duration, ratio between tangential and normal loads during impact and wear volume is highlighted and discussed.

PRINCIPLE OF EXPERIMENT Test rig

The test rig is shown in Figure 1. Two shakers are placed at ±45° to the vertical and excite a hard steel cylinder sample. Two identical springs with the same stiffness (k = 590 N/m) provide the connection between the shaker and the sample holder (m = 0.17 kg). Thus, the natural frequency f0 of the impactor is 9.5 Hz.

The incidence angle α to the horizontal is obtained by setting a specific ratio between the amplitudes of each of the two shakers sinusoidal inputs. Therefore, any test with an incidence angle between 10° and 90° can be performed.

During its motion, the impactor hits a mild steel cylinder sample that is expected to wear. Cylinders are crossed so that a point contact is obtained.

FIGURE 1. TEST RIG.

Test samples

The impactor cylinder (Ø = 7 mm, L = 7 mm) has a Vickers hardness of 820 Hv whereas the target (Ø = 7 mm, L = 7 mm) has a Vickers hardness of 145 Hv. Both have a Young modulus of 200 GPa.

Load measurement protocol and signal processing

The three components of the contact load are measured by a 3-axis piezoelectric load transducer placed behind the sample. Its stiffness is equal to 740 N/µm for the Z component and 170 N/µm for the X and Y components. The mass supported by the load transducer is about 0.1 kg (sample and sample holder), so the measure of the contact load is accurate up to 7 kHz for the tangential components and 14 kHz for the normal component. Signals are acquired with a dynamic signal acquisition card and a high sampling rate of 50 kHz in order to correctly measure the contact load during impact.

A complete acquisition of the contact load during the full length of the test is impossible due to storage space limitations. Therefore, signals are acquired during 1500 evenly distributed acquisition windows of 1 second.

Signals are processed in order to automatically find each impact and retrieve the impact rate, flight and contact durations, normal and tangential components of the contact load during impact. Ratio between maxima of tangential and normal loads µ is then calculated for each impact.

Wear conditions and testing parameters

All tests are performed with the following characteristics. The test duration is 17 h, the excitation frequency f is chosen about 30 Hz and the excitation levels of the shakers are adjusted in order to obtain a maximal normal load during impact of 12 N in average. The Hertz theory applied to an equivalent static contact predicts a maximal contact pressure about 1.5 GPa, a contact diameter of 120 µm and a depth of indentation 𝜹𝜹 𝒏𝒏 of 2.1 µm. As the actual contact area is smaller than the apparent one, pressure would be concentrated at the top of surface asperities and could generate local plastic deformation.

Moderate contact loads are applied to focus more on erosive wear than on fatigue or delamination. The set of parameters is chosen to get a substantial amount of wear in a relative short time.

Wear volume analysis

At the end of a test, worn sample is removed from test rig and wear scars are analyzed with an optical interferometer (Figure 2). Negative, positive and natural volumes of wear are then retrieved.

Uncertainty on volume is calculated based on uncertainties of the interferometer measurement and the surface adjustment. Minimal wear volume that can be measured is estimated at 10 -3 mm 3 .

FIGURE 2. INTERFEROGRAM OF A WEAR SCAR

IMPACTS CHARACTERISTICS

Large time scale Figure 3 shows the time evolution of normal load during 1 s. Impacts are clearly distinguishable as quick variations of the contact load. A free flight period separate two successive main impacts which usually last about 50 ms. Some main impacts are followed by multiple lower amplitude impacts during a short period (about 30 ms). It can be understood as successive rebounds of the impactor that occur after the main impact. The dynamics of the system is highly nonlinear due to impacts. The resulting trajectory may therefore be periodic, aperiodic or even chaotic. In this case, the trajectory is clearly not periodic and therefore the magnitude of impacts is not constant. The impact rate also differs from the excitation frequency for the same reason. During a 17 hours duration test, the total number of impacts typically ranges from 1.8 to 3.7 million that is to say from 30 to 60 impacts per second.

FIGURE 3. LARGE TIME SCALE EVOLUTION OF 𝐹𝐹 𝑛𝑛

Short time scale

Figure 4 shows the time evolution of normal load during a single impact. This curve has a bell shape like expected for a typical shock [START_REF] Rigaud | Influence of incidence angle on wear induced by sliding impacts[END_REF]. Contact duration is retrieved from the main peak of normal load and usually ranges from 0.4 to 0.8 ms. The maximal value of load during this particular impact is about 20 N. The free oscillation of the sample is observable after the impact and its frequency is about 2 kHz. The slight perturbation of the bell shape near the maximal value is also due to the influence of this eigenmode. This free response is supposed to have a minimal influence on the value of the maximal load amplitude.

FIGURE 4. SHORT SCALE TIME EVOLUTION OF 𝐹𝐹 𝑛𝑛 DURING IMPACT

Wear characteristics

Observed wear scars are typically oval and their shapes give information about the mechanical processes that take place during impacts. Material is either removed as wear debris or displaced by plastic deformation. Thus, positive volumes correspond to displaced material and natural volumes correspond to removed material.

In the following, wear volumes 𝑊𝑊 𝑡𝑡𝑡𝑡𝑡𝑡 and 𝑊𝑊 𝑖𝑖𝑖𝑖𝑖𝑖 are defined as natural volume and natural volume per impact, that is to say difference between positive and negative measured volumes. In this way, only removed material is taken into account.

EXPERIMENTAL RESULTS AND DISCUSSION

Impact duration and 𝝁𝝁 � The observed impact durations range from 0.4 to 0.9 ms and the corresponding load curve is systematically bell-shaped.

Figure 5 shows average impact duration 𝑡𝑡 𝚤𝚤𝑖𝑖𝑖𝑖 ������ versus 𝜇𝜇̅ defined as the average of instantaneous ratio between 𝐹𝐹 𝑡𝑡 and 𝐹𝐹 𝑛𝑛 during a complete test. 𝑡𝑡 𝚤𝚤𝑖𝑖𝑖𝑖 ������ increases with 𝜇𝜇̅ , from 0.4 ms for normal impacts to 0.9 ms for impacts with a high tangential component. This increase of 𝑡𝑡 𝚤𝚤𝑖𝑖𝑖𝑖 ������ may highlight an increase of the sliding distance 𝛿𝛿 𝑡𝑡 during contact.

FIGURE 5. IMPACT DURATION VERSUS 𝜇𝜇̅

Instantaneous ratio 𝝁𝝁 � and incidence angle

Experiments with various incidence angles are performed. Whereas 𝜇𝜇̅ and 𝛼𝛼 � are usually independent, 𝜇𝜇̅ is here observed to be inversely proportional to incidence angle in the explored range (Figure 6). The linear dependence between 𝜇𝜇̅ and 𝛼𝛼 � is expressed in equation ( 1) and is consistent with previous observations [START_REF] Rigaud | Influence of incidence angle on wear induced by sliding impacts[END_REF] under the similar experimental conditions. 𝜇𝜇̅ = -0.02𝛼𝛼 � + 1.9 (15°≤ 𝛼𝛼 � ≤ 70°)

FIGURE 6. 𝜇𝜇 � VERSUS INCIDENCE ANGLE

Incidence angle and wear

Wear volume is compared with 𝛼𝛼 � to make the connection with erosive wear models (Figure 7). Indeed, most of these models relate wear with incidence angle [START_REF] Finnie | Erosion of surfaces by solid particles[END_REF][START_REF] Bitter | A study of erosion phenomena[END_REF][START_REF] Tilly | A two stage mechanism of ductile erosion[END_REF][START_REF] Brach | Impact dynamics with applications to solid particle erosion[END_REF][START_REF] Sundararajan | A comprehensive model for the solid particle erosion of ductile materials[END_REF].

Experimental results show that wear increases as the incidence angle is more and more grazing. These experimental values are compared to the erosive wear model of Brach [START_REF] Brach | Impact dynamics with applications to solid particle erosion[END_REF][START_REF] Brach | Classical planar impact theory and the tip impact of a slender rod[END_REF] and Sundararajan [START_REF] Sundararajan | A comprehensive model for the solid particle erosion of ductile materials[END_REF] in which a normalized shear energy 𝑇𝑇 * is introduced (equations ( 2) and ( 3)). In this model, wear volume is assumed to be proportional to this shear energy.

𝑇𝑇 * = 1 (1+𝜆𝜆) 𝜇𝜇 � µ 𝑐𝑐 �2 - 𝜇𝜇 � µ 𝑐𝑐 � cos 2 𝛼𝛼 � (2)
µ 𝑐𝑐 = 1 (1+𝜆𝜆)(1+𝑒𝑒) tan 𝛼𝛼 � ( 3
)
𝑇𝑇 * is defined as a dimensionless energy transferred to target during an impact. This definition takes two sources of energy dissipation into account: an energy associated with the impactor rebound (through 𝑒𝑒) and an energy associated with friction (through 𝜇𝜇̅ and 𝛼𝛼 �). Considering asperities as spherical erosive particles treated as point masses, it is assumed that 𝜆𝜆 = 0. Furthermore, 𝑇𝑇 * can be expressed only with 𝜇𝜇̅ considering the experimental law between 𝜇𝜇̅ and 𝛼𝛼 � (equation 1). 𝜇𝜇̅ is obtained from load measurements during the test. The definition of the restitution coefficient 𝑒𝑒 is chosen as the ratio between rebound velocity and incident velocity. It is measured with a laser vibrometer on several impacts and we obtain in average 𝑒𝑒 = 0.85.

Figure 7 shows a very fine agreement between measured wear volumes per impact and the normalized shear energy as predicted by Brach in the range [15° 70°]. No experimental investigation has been made for incidence angle under 15°.

This result confirms that erosive models can be relevant to describe wear of macroscopic bodies [START_REF] Kaiser | Wear damage resulting from sliding impact kinematics in pressurized high temperature water: energetical and statistical approaches[END_REF].

Instantaneous ratio 𝝁𝝁 � and wear

Wear is compared with 𝜇𝜇̅ (Figure 8). As 𝜇𝜇̅ and 𝛼𝛼 � are found to be related with a nearly linear relation (equation ( 2)), it is consistent to find that wear increases with 𝜇𝜇̅ . It is interesting to note that 𝜇𝜇̅ = 1 seems to be a transitional value between two wear modes. Observed wear for 𝜇𝜇̅ > 1 is much more important than for 𝜇𝜇̅ < 1.

FIGURE 8. 𝑊𝑊 𝑖𝑖𝑖𝑖𝑖𝑖 VERSUS 𝜇𝜇̅

CONCLUSION

Impact wear between two steel crossed cylinders is studied. Experiments are performed and influence of 𝜇𝜇̅ on impact duration is highlighted as well the linear dependence between 𝜇𝜇̅ and 𝛼𝛼 �. The influence of 𝜇𝜇̅ on wear is highlighted and experimental results are compared to an erosive wear model. These results confirm the importance of shear stress on wear formation.

Further work is in progress and aims at adapting the test rig in order to make impacts between real heat exchanger tubes and AVB instead of steel cylinders. In this way, experimental contact geometry and materials will be more consistent with the real ones. Displacement of the impactor will also be measured in order to obtain information about incidence and rebound velocities and angles and about sliding distance during impact.

FIGURE 7 .

 7 FIGURE 7. EVOLUTION OF T* (-) AND 𝑊𝑊 𝑖𝑖𝑖𝑖𝑖𝑖 (o) VERSUS 𝛼𝛼 �


Luca Dioni
email: luca.dioni@fresnel.fr

Robert Jacqmin
email: robert.jacqmin@cea.fr

B. Stout. A Multipurpose Fast Marco Sumini

Brian Stout

A * Midex

A Multipurpose Fast Neutron Beam Capability at the MASURCA Facility

I. INTRODUCTION

ASURCA, which stands for "mock-up facility for fast breeder reactor studies at Cadarache" is a zero-power critical facility, which was built in the 60's for the purpose of studying experimentally the physics of fast neutron lattices and cores [START_REF] Bignan | Experimental Reactor Physics Perspectives in France[END_REF].

Until the early 90's, MASURCA was operated almost exclusively for experimental validation studies of sodiumcooled fast neutron reactor cores. Subsequent programs were directed towards nuclear waste transmutation physics, while other similar facilities in Europe and in the USA were permanently shut down. These transmutation experiments, most notably the European Commission sponsored FP5/MUSE-4 program [START_REF] Mellier | The MUSE experiments for sub critical neutronics validation[END_REF] -which involved a sub-critical lead-cooled core coupled with a neutron generator -attracted interest among European countries and were carried out as part of international collaborations.

The MASURCA facility is currently undergoing a major multiyear refurbishment work in preparation for new programs in support of future fast reactors, mainly the ASTRID demonstrator [START_REF]Fourth-generation Sodium-cooled Fast Reactors -The ASTRID Technological Demonstrator[END_REF]. This work entails not only improvements in the instrumentation and measurement techniques, but also the possible use of the facility for a broader spectrum of fast neutron physics applications. This paper presents the first results of a prospective investigation of MASURCA as a fast neutron source from which a well-characterized fast-neutron "beam" of sufficient intensity could be extracted and used for various purposes. This investigation takes full advantage of the unique features of the facility and of the favourable reactor building characteristics. The feasibility is evaluated by means of modern neutron transport simulation codes, both deterministic and Monte Carlo.

II. THE MASURCA FACILITY

A. Main Features MASURCA (Fig. 1a) is a low-power, air-cooled reactor having a rated maximum neutron flux level of about 10 11 neutrons cm -2 s -1 at the core centre, which corresponds to a thermal power of 5 kW [START_REF] Assal | Experimental Measurements at the MASURCA Facility[END_REF].

Experimental configurations are constructed by loading subassemblies (called "tubes"), vertically, in a square lattice. These stainless steel structure tubes have a 106 mm x 106 mm horizontal cross section and are about four meter long. They are filled with small rodlets or platelets of various types (fissile, fertile, structure, coolant, absorber, air, etc.), arranged in such a way as to represent average material concentrations and geometrical patterns of interest (Fig. 1b). Hundreds of such tubes can be loaded, allowing core diameters up to approximately 3.8 m. A typical experimental configuration consists of a quasi-cylindrical fissile core, radially surrounded by a fertile blanket or steel reflector, itself surrounded by shielding tubes. As a consequence of the large and diverse inventories of materials available at MASURCA, there is considerable flexibility in the configurations that can be simulated.

A shutdown mechanism is provided by four to eight Safety Rods (SR), depending on the characteristics and size of the core. A calibrated, low-worth Pilot Rod (PR) is used to adjust the core reactivity near the critical state. Some of the structure tubes have openings in their opposite sides, at mid-height, so that horizontal measurements channels running across the core in the X and Y directions can be made. Local measurements are typically obtained by moving small fission chambers through such radial channels, from the open space surrounding the biological shield (Label 18 in Fig. 1). A radial channel as large as 10x10 cm 2 in cross-sectional area can even be arranged (Label 16 in Fig. 1), as was done for the MUSE-4 experiments, which are further discussed below.

B. The MUSE-4 Program as an illustration of the MASURCA flexibility

The high flexibility of MASURCA is best exemplified by the MUSE-4 program (2000-2004) [START_REF] Mellier | The MUSE experiments for sub critical neutronics validation[END_REF]. In this series of experiments, a neutron source was generated by fusion reactions of deutons impacting a tritium (or deuterium) target placed at the centre of various sub-critical neutron multiplying media (Fig. 2). This setup was used to investigate the physics of ADSs (Accelerator Driven Systems).

The GENEPI variable-frequency pulsed deuton accelerator and its associated high-voltage 250 kV unit were conveniently located in the large open space provided by the "accelerator room" on the North side of the reactor hall, which was already equipped with a biological shield. The deuton beam was focussed and transported to the MASURCA core centre thru a vacuum guide tube running through a pre-arranged 10x10 cm 2 radial channel, from an opening made in the reactor biological shield. Further advantage was taken of the large space available in the accelerator room to install an on-line beam monitoring instrument, facing the opening. This instrument was made of silicon detectors which detected the protons and alpha particles emitted at nearly 180° angle of the incident beam and returning thru the guide tube.

III. MOTIVATION FOR AN EXTRACTED NEUTRON BEAM

The preceding considerations suggest that MASURCA could be used as a versatile fast neutron source capable of delivering a steady fast neutron flux of up to 10 11 neutrons cm - 2 s -1 in all directions, and that a fraction of this neutron flux having energies distributed in the 1 keV to 5 MeV range could be delivered to the accelerator room thru a prearranged radial air (or vacuum) channel and an adjustable-size window in the biological shield. This opportunity results from the combination of several favourable features: fast neutron spectrum, kW-level thermal power as opposed to just ~100W in most critical facilities, small neutron attenuation thru air in experimental channels, easy access to the reactor core from all sides, large and diverse inventories of materials so that the neutron source spectrum can be tailored to different needs. Such an extracted "beam" of fast neutrons adaptable in intensity, size and energy spectrum, could serve several purposes. Potential applications include neutron activation analyses, semi-integral neutron cross section measurements, testing of medical equipment for neutron capture therapy, validation of neutron radiography systems for the detection of nuclear materials, neutron instrumentation testing, etc.

Before definite statements can be made about the practical use of such a beam for specific applications, several conditions must be met. These conditions relate to the beam characteristics in intensity, energy spectrum, gamma-toneutron background, at various positions along the channel, as well as to the sensitivity of these characteristics to changes in the source neutrons and in the general experimental setup. These feasibility issues were investigated by numerical simulations, which are described hereafter.

IV. FEASIBILITY STUDY

A. Calculation models

For this feasibility study, two 3-D quasi-spherical models of small sodium-cooled fast reactor cores were considered. Such simple models have the advantage of not requiring large computational times, while being sufficiently representative of the main physics phenomena for a preliminary assessment. The two models differ only in the type of fuel utilized: one is a MOX fuel, based on the fissile isotope Pu 239 (Configuration MOX), while the other one is a metallic fuel, based on U 235 (Configuration U-METAL). The isotopic fractions are shown in Table I. The fissile core is centred at the X=0, Y=0 position in the MASURCA co-ordinate system. It is surrounded by a 32-cm thick reflector composed of sodium and stainless steel (Fig. 3). This reflector shell is itself surrounded radially by a 43-cm shield made of steel and absorber materials. About one meter of air separates the core from a biological shield made of 90 cm of concrete.

In these simple concentric spherical shell models, the radial beam channel is approximated by a right circular air-filled cone starting at the core-reflector interface (A), having its vertex at the centre of the spheres and extending outwards past the concrete wall (B). The opening angle of the cone was derived from the constraint of a maximum beam exit port radius of ~15 cm in the biological shield, and was found to be 5.36 degrees.

The different zones and geometrical characteristics of the models are summarized in Table II.

B. Calculation tools

The feasibility study was performed with two well-known neutron transport codes: the deterministic code ERANOS2 [START_REF] Rimpault | The ERANOS Data and Code System for Fast Reactor Neutronic Analyses[END_REF], and the continuous-energy Monte Carlo code TRIPOLI-4 [START_REF] Trama | Overview of TRIPOLI-4 version 7 Continuous Energy Monte Carlo Code[END_REF], using the nuclear data library JEFF-3.1. The codes were used in two successive steps. The ERANOS-2 code was first used for finding thecritical radii of the cores (these spherical critical radii shown in Table II were actually derived from realistic R-Z configurations) using the given material concentrations. These critical radii, together with the total (isotropic) flux level in the cores, and the intensities of the fission sources, were then used as inputs to propagation calculations performed with TRIPOLI-4.

In the TRIPOLI-4 simulation, surface tallies were defined to count the particles, both neutrons and photons, travelling in the channel and crossing successive spherical shells within the cone. These tallies provide a measure of the outgoing surface current (particles cm -2 s -1 ) and energy distribution of the particles. In order to estimate the sensitivity of the neutron spectrum at the exit of the beam (in the biological shield), material changes were made in the core loading and their impact assessed on the "uncollided" portion of the neutron beam, i.e., the of core neutrons in the cone that reach the channel exit port directly from the core edge. A zero current of returning particles was set on the outer shell boundary. All calculations were normalized at 1 kW total thermal power.

V. RESULTS AND DISCUSSION

The radial profile of the total neutron flux is shown in Fig. 4a for Configuration MOX and Fig. 5a for Configuration U-METAL. The (isotropic) neutron flux level at the core centre is on the order of 10 10 neutrons cm -2 s -1 .

In either configuration, the neutron current intensity (directional flux) at the channel entrance is on the order of 10 9 neutrons cm -2 s -1 , and on the order of 10 6 neutrons cm -2 s -1 at the channel exit. This intensity compares favourably with those of other machines in which attempts have been made to 0.0E+00 5.0E+09 develop fast neutron beams. Note that, should that be deemed necessary, higher outgoing beam intensities could be reached by moving the core off-centre, in the direction of the channel, and simultaneously reducing the reflector or shield thickness.

Figs. 4b and4c show the energy distribution of the outgoing neutron current at the beginning of the channel (A), at the core-reflector interface, and at the end of the channel (B) at the outer boundary, for Configuration MOX. Figs. 5b and5c show the corresponding plots for Configuration U-METAL.

The total exiting neutron spectrum retains some of the source fast neutron distribution characteristics, but also includes, as expected, a slowing-down component, due to the many scattered neutrons that come from the whole system, as no attempt was made to filter those out in this preliminary investigation.

In order to appreciate the relative importance of the scattered neutrons, the spectra of uncollided neutrons are plotted in Fig. 6. The results are compared with the total spectrum obtained for Configuration MOX (Fig. 6a) and Configuration U-METAL (Fig. 6b).

Fig. 6 provides information about the origin of the neutrons reaching the channel exit. The highest part of the spectrum (MeV range) is dominated by neutrons coming directly from the core, while there is a growing contribution of scattered neutrons as one moves to lower energies, especially in the keV and lower energy regions. It is interesting to note that the detailed energy structure down to ~1 keV (especially around The intensity of the total uncollided current is on the order of 10 5 neutrons cm -2 s -1 , which is about an order of magnitude lower than the total beam intensity at the channel exit. Regarding the intensity of the outgoing gamma-ray current at the end of the channel, it is on the order of 10 5 photons cm -2 s - 1 , a relatively high value which will require appropriate shielding and proper discrimination in the detection system.

In Fig. 4b and Fig. 5b, the harder spectrum of the uranium metal system (Configuration U-METAL), compared with the plutonium oxide system (Configuration MOX), is clearly visible at the beginning of the beam, but much less so at the channel exit (Fig. 7a).

In order to appreciate this difference better, the outgoing current of uncollided neutrons has been plotted in Fig. 7b, at the exit of the channel.

In Table III, the fractions of outgoing neutrons are compared over three energy intervals: thermal (E th <0.5 eV), epithermal (0.5 eV<E epi <10 KeV) and fast (E fast >10 KeV). It can be concluded from Fig. 7 and Table III that the contribution of scattered neutrons dominates that of the uncollided neutrons at the beam exit by more than an order of magnitude, with the consequence that differences in core fissile constituents are hardly visible. Different geometrical arrangements could have been considered to modify this ratio and achieve a higher proportion of uncollided neutrons, but this possibility was not investigated as part of this initial study.

VI. CONCLUSION

In this prospective study, we investigated the possible use of the MASURCA experimental reactor as a fast neutron beam source, taking advantage of the unique features and high flexibility of the facility. Simple spherical models were used to quantify the intensity, energy spectrum, and sensitivity of the directional neutron flux, which would travel in a speciallyarranged radial air-filled channel and exit past the biological shield, in the adjacent "accelerator room", some 2.7 to 2.9 meters away from the core outer surface.

Results of numerical simulations show that a neutron current on the order of ~4 10 6 neutrons cm -2 s -1 can be reached at the channel exit, when the core is operated at 1 kW thermal power, corresponding to a central flux of 3.8 10 10 neutrons cm - 2 s -1 . The corresponding gamma flux level at the channel exit was found to be about 10 5 photons cm -2 s -1 . As expected, the spectrum of the exiting neutrons contains a significant intermediate-energy component, resulting in a low sensitivity to the core fissile constituents. Indeed, in the model setups considered, only about 5 to 10% of the neutrons in the exiting beam are uncollided neutrons from the core, the others being neutrons that have undergone scattering collisions in various parts of the system.

On the basis of these preliminary findings, we conclude that MASURCA definitely has the potential for delivering a continuous fast neutron beam of some ~10 7 neutrons cm -2 s -1 in the accelerator room, 70% of those neutrons having energies in the 10 keV to 5 MeV range. Such a fairly high intensity neutron beam could have several applications. Further studies are needed to determine geometrical setups (off-centred core position, filters, …), in which the relative contribution of uncollided neutrons would be significantly increased, and thereby the sensitivity to the core fissile constituents improved. As part of these studies, fast neutron spectrometric techniques will be investigated, capable of providing a high energy resolution characterization of the beam.

A

  Multipurpose Fast Neutron Beam Capability at the MASURCA Facility L. Dioni, R. Jacqmin, M. Sumini, B. Stout Abstract-In this paper we investigate the possible future use of the CEA Cadarache MASURCA experimental fast reactor to generate a fairly high-intensity continuous beam of fast neutrons, having energies distributed in the 1 KeV to 5 MeV range. Such an extracted beam of fast neutrons, tailorable in intensity, size and energy, would be rather unique; it would be of interest to neutron-based research and could open a range of new applications at MASURCA. We report the results of numerical simulations which have been performed to evaluate the feasibility of such a beam port and to characterize it spectrally.

1 .

 1 (a) Cut-away View of the MASURCA Reactor Building and (b) an Example of a Typical MASURCA Fuel Tube Arrangement.

Fig. 2 .

 2 Fig. 2. Horizontal Cross-sectional View of the MUSE-4 Critical Configuration, the Numbers Indicate the Positions of the Foils (for Foil Activation Measurement) in the Experimental Channels [5].

Fig. 3 .

 3 Fig. 3. Schematic View of the Calculation Models.

4 .

 4 Configuration MOX: (a) Total Neutron Flux Radial Profile; (b) Energy Spectrum of Neutron Outgoing Current at the Beginning of the Channel; (c) Energy Spectrum of Neutron Outgoing Current at the End of the Channel.

5 .

 5 Configuration U-METAL: (a) Total Neutron Flux Radial Profile; (b) Energy Spectrum of Neutron Outgoing Current at the Beginning of the Channel; (c) Energy Spectrum of Neutron Outgoing Current at the End of the Channel.

6 .

 6 (a) Comparison Between Total and Uncollided Neutron Current at the End of the Channel for Configuration MOX and (b) for Configuration U-METAL.

7 .

 7 Computed (a) Total=Collided+Uncollided, and (b) Un-collided Outgoing Current Spectra for Configuration MOX (softer spectrum) and Configuration U-METAL (harder spectrum). the large 2.8 keV Na-23 and 28 keV Fe-56 scattering resonances) is preserved though.

TABLE I .

 I FUEL COMPOSITIONS OF THE TWO MODELS

	Configuration	Element	Isotope	Fraction (%)
	MOX	Pu (~27 %)	Pu 238	0.2
			Pu 239	78.7
			Pu 240	19.1
			Pu 241	1.4
			Pu 242	0.7
		U (~73 %)	U 235	0.3
			U 238	99.6
	U-METAL	U (100 %)	U 235	30.3
			U 238	69.7

TABLE II .

 II GEOMETRICAL CHARACTERISTICS OF THE CALCULATION MODELS

	Configuration	Zone	Main Materials	R sphere (m)
	MOX	Core	fuel + sodium	0.44
		Reflector	steel + sodium	0.76
		Shield	steel + absorbers	1.18
		Air		2.30
		Concrete		3.20
	U-METAL	Core	fuel + sodium	0.28
		Reflector	steel + sodium	0.60
		Shield	steel + absorbers	1.02
		Air		2.30
		Concrete		3.20

TABLE III .

 III FRACTIONS OF THERMAL, EPITHERMAL AND FAST NEUTRONS IN THE TOTAL AND UNCOLLIDED OUTGOING CURRENTS

		1.0E+06			1.0E+06
	Current [n/cm 2 s]	1.0E+02 1.0E+03	Current [n/cm 2 s]	1.0E+02 1.0E+03 1.0E+04 1.0E+05
		1.0E+01			1.0E+01
			1.0E-09 1.0E-07 1.0E-05 1.0E-03 1.0E-01 1.0E+01			1.00E-091.00E-071.00E-051.00E-031.00E-011.00E+01
			Energy [MeV]			Energy [MeV]
			1.0E+06
					1.4E+04
	Currrent [n/cm 2 s]	1.0E+02 1.0E+04 1.0E+05	Current [n/cm 2 s]	4.0E+03 6.0E+03 8.0E+03 1.0E+04 1.2E+04
					2.0E+03
			1.0E+01		1.0E+01
			1.0E-09 1.0E-07 1.0E-05 1.0E-03 1.0E-01 1.0E+01			1.0E-09 1.0E-07 1.0E-05 1.0E-03 1.0E-01 1.0E+01
			Energy [MeV]			Energy [MeV]
						J total	J th /J total	J epi /J total	J fast /J total
				Total MOX Uncollided MOX	4.07×10 6 3.48×10 5	0.28 0.02	0.27 0.10	0.45 0.88
				5.23×10 6 Uncollided U-METAL 2.63×10 5 Total U-METAL	0.28 0.02	0.25 0.05	0.46 0.93

ACKNOWLEDGMENTS

We thank the Laboratoire d'Etudes de Physique of the CEA Cadarache (CEA-DEN/CAD/DER/SPRC/LEPh), especially Yannick Peneliau and Jean Tommasi, for their technical assistance.

This work has been carried out thanks to the support of the A*MIDEX grant (n°ANR-11-IDEX-0001-02) funded by the French Government « Investissementsd'Avenir » program.

, initiative d'excellence Aix-Marseille.