[en] Nuclear heating inside an MTR reactor has to be known in order to be able to control samples temperature during irradiation experiments. An R and D program has been carried out at CEA to design a new type of in-core calorimetric system. This new development, started in 2002, has for main objective to manufacture a calorimeter suitable to monitoring nuclear heating inside the 70 MWth OSIRIS material testing reactor operated by CEA's Nuclear Energy Division at the Saclay research center. An innovative calorimetric probe, associated to a specific handling system, has been designed to provide access to measurements both along the fissile height and on the upper part of the core, where nuclear heating still remains high. Two mock-ups of the probe were manufactured and tested in 2005 and 2009 in ex-core area of OSIRIS reactor for process validation, while a displacement system has been especially studied to move the probe along a given axial measurement range. This paper deals with the development, tests on preliminary mock-ups and the finalization of the probe. Main modeling and experimental results are presented. Moreover, alternative methods to calibration for nuclear heating rate measurements which are now possible with this new calorimeter are presented and discussed. (authors)

[en] Nuclear heating rate inside an MTR has to be known in order to design and to run irradiation experiments which have to fulfill target temperature constraints. This measurement is usually carried out by calorimetry. An innovative calorimetric system, CALMOS, has been studied and built in 2011 for the 70 MWth OSIRIS reactor operated by CEA. Thanks to a new calorimetric probe, associated to a specific displacement system, it provides measurements along the fissile height and above the core. Development of the calorimetric probe required manufacturing and irradiation of mock-ups in the ex-core area, where nuclear heating rate does not exceed 2 W.g"-"1. The calorimeter working mode, the different measurement procedures, main modeling and ex-core experimental results have been already presented in previous papers. In this paper, we present in-core results obtained from 2011 to 2013 with the final device. For the first time, this new experimental measurement system was operated in several experimental locations, with nominal in-core thermal hydraulic conditions, nominal neutron flux and nuclear heating rate up to 6 W.g"-"1 (in graphite). After a brief presentation of the displacement system specificities, first nuclear heating distributions are presented and discussed. The Finite Element model of the calorimeter was upgraded in order to match calculated temperatures with measured ones. This 'validated' model allowed to estimate a Kc factor which tends to correct small nonlinearities when heating rate is calculated from the 'calibration method'. A comparison is made between nuclear heating rates determined from 'calibration' and 'zero methods'. In addition, an evaluation of the global uncertainty associated to the measurements is detailed. Finally, a comparison is made with available measurements obtained from previous calorimeters. (authors)

[en] Nuclear heating rate inside an MTR has to be known in order to design and to run irradiation experiments which have to fulfill target temperature constraints. This measurement is usually carried out by calorimetry [1, 2]. An innovative calorimetric system, CALMOS, has been studied and built in 2011 for the 70 MWth OSIRIS reactor operated by CEA. Thanks to a new calorimetric probe, associated to a specific displacement system, it provides measurements along the fissile height and above the core. The development of the calorimetric probe required the manufacturing and the irradiation of mock-ups in the ex-core area, where nuclear heating rate does not exceed 2 W.g^-1. The calorimeter working mode, the different measurement procedures allowed with such a new probe and main modeling and experimental results have been already presented [3, 4]. In this paper, we present the first results obtained during several measurement campaigns carried out in 2012 and 2013 inside the OSIRIS core with the final device. For the first time, this new experimental measurement system was operated in nominal in-core thermo hydraulic conditions with nominal neutron and gamma fluxes (up to 6 W.g^-1) in several experimental locations. After a brief presentation of the displacement system specificities, first nuclear heating distributions are presented and discussed. Experimental data were also used to upgrade the Finite Element model of the calorimeter in order to match measured temperatures with calculated ones. This model allowed to estimate a Kc correction factor which takes into account small nonlinearities when the heating rate is deduced from the calibration method. A comparison is made between nuclear heating rates determined from the probe calibration and from the zero method. In addition, an evaluation of the global uncertainty associated to the measurements is detailed. Finally, a global comparison is made with available measurements obtained from previous calorimeters. (authors)

[en] Laser Induced Breakdown Spectroscopy (LIBS) is a powerful technique for determining the elemental composition of materials based on measuring line emission from excited ions and neutral atoms in a transient laser-produced plasma. Nearly all the elements, even the light ones, can be simultaneously analysed at atmospheric pressure and without any preparation, or with limited sample preparation. Able to perform fast and remote analyses, it looks quite well suited to analyzing nuclear materials. Usually, quantitative analysis becomes possible as soon as the calibration curve is performed using reference samples. The presentation will first deal with the general aspects and characteristics of the technique. Examples of representative applications developed by Cea for the nuclear industry will be presented. The interest of the technique has been demonstrated for the analysis of simulated Ce-U Mox pellets or for the study of radionuclide migration through porous soil. As remote analysis is concerned, analytical results on samples isolated into glove boxes or hot cells will be discussed. The demonstrated versatility of this technique will allow online monitoring of reductive liquid-liquid extraction process as well as analysis of solid salt or metal samples. Other results obtained with a specific LIBS system designed for onsite measurements during decommissioning of nuclear installations will also be presented. As microanalysis is concerned, the microprobe LIBS instrument developed by Cea will be described and results of high resolution chemical mappings of simulated Mox nuclear fuel will be presented

[en] Nuclear heating inside a MTR reactor has to be known in order to design and to run irradiation experiments which have to fulfill target temperature constraints. This measurement is usually carried out by calorimetry. The innovative calorimetric system, CALMOS, has been studied and built in 2011 for the 70 MWth OSIRIS reactor operated by CEA. Thanks to a new type of calorimetric probe, associated to a specific displacement system, it provides measurements along the fissile height and above the core. This development required preliminary modelling and irradiation of mock-ups of the calorimetric probe in the ex-core area, where nuclear heating rate does not exceed 2 W.g"-"1. The calorimeter working modes, the different measurement procedures allowed with such a new probe, the main modeling and experimental results and expected advantages of this new technique have been already presented. However, these first in-core measurements were not performed beyond 6 W.g"-"1, due to an inside temperature limitation imposed by a safety authority requirement. In this paper, we present the first in-core simultaneous measurements of nuclear heating and conventional thermal neutron flux obtained by the CALMOS device at the 70 MW nominal reactor power. For the first time, this experimental system was operated in nominal in-core conditions, with nominal neutron flux up to 2.7 10"1"4 n.cm"-"2.s"-"1 and nuclear heating up to 12 W.g"-"1. A comprehensive measurement campaign carried out from 2013 to 2015 inside all accessible irradiation locations of the core, allowed to qualify definitively this new device, not only in terms of measurement ability but also in terms of reliability. After a brief reminder of the calorimetric cell configuration and displacement system specificities, first nuclear heating distributions at nominal power are presented and discussed. In order to reinforce the heating evaluation, a systematic comparison is made between results obtained by different methods, the probe calibration coefficient and the zero method. Thermal neutron flux evaluation from the SPND signal processing required a specific TRIPOLI-4 Monte Carlo calculation which has been performed with the precise CALMOS cell geometry. In addition, the Finite Element model for temperatures map prediction inside the calorimetric cell has been upgraded with the recent experimental data obtained up to 12 W.g"-"1. The Kc coefficient, taking into account nonlinearities with regard to the calibration, has been reevaluated so as to make relevant measurements up to the nominal reactor power. Finally, the experience feedback acquired until now with this first CALMOS version led us to improvement perspectives. A second device is currently under manufacturing and main technical options chosen for this second version are presented. (authors)

[en] This work is devoted to the study of the gas pressure effect on the laser-induced breakdown spectroscopy signal intensity of carbon. Experiments are performed, using a 1064 nm Nd:YAG laser, with carbon solid samples placed inside a high pressure chamber filled with helium or nitrogen, the gas pressure varying from 1 to 80 atm. The signal intensity of the carbon line (247.86 nm) decreases with increasing pressure. As the plasma size strongly decreases with pressure, two collection optical setups are used, showing different raw results. To take into account the plasma size evolution with pressure, calculated corrections are applied to the collected light intensity. Carbon line emission is measured and corrected as a function of pressure in both gases. At 1 atm, the emission line is found to be greater in helium than in nitrogen by a factor of approximately 3, whereas the intensities in the two gases become close to each other at 80 atm

[en] Nuclear heating inside a Material Testing Reactor (MTR) needs to be known in order to design and to run irradiation experiments that have to fulfill target temperature constraints. To improve the in core nuclear heating knowledge of the French OSIRIS reactor operated by CEA, an innovative calorimetric system CALMOS (French acronym for CALorimetre Mobile OSiris) has been studied, manufactured and tested. This device can be inserted in any in-core experimental location. It is based on a mobile probe moving axially along the core height. First tests of this new probe, offering several ways for the heating evaluation, were performed in the reactor periphery. Then, two complete prototypes dedicated to in core measurements (calorimeter and the associated displacement system) were designed and tested during several reactor cycles. This paper presents a comprehensive analysis of all the results collected during the measurement campaigns carried out between 2013 and 2015 with these new prototypes in various reactor conditions. A comparison is made with previous calorimeters and obtained advantages are emphasized. This new calorimeter has been designed as a real operational measurement system, well suited to characterize the radiation field inside an MTR reactor. (authors)

[en] The accurate quantification of nucleic acids is essential in many fields of modern biology and industry, and in some cases requires the use of fluorescence labeling. Yet, in addition to standardization problems and quantification reproducibility, labeling can modify the physicochemical properties of molecules or affect their stability. To address these limitations, we have developed a novel method to detect and quantify label-free nucleic acids. This method is based on stoichiometric proportioning of phosphorus in the nucleic acid skeleton, using laser-induced breakdown spectroscopy, and a specific statistical analysis, which indicates the error probability for each measurement. The results obtained appear to be quantitative, with a limit of detection of 10⁵ nucleotides/μm² (i.e. 2 x 10¹³ phosphorus atoms/cm²). Initial micro-array analysis has given very encouraging results, which point to new ways of quantifying hybridized nucleic acids. This is essential when comparing molecules of different sequences, which is presently very difficult with fluorescence labeling