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International audience; The MAGIX code (a French acronym standing for Automatic Gamma and X-ray Measurement) is a software developed to analyze γ/X spectra on the topic of severe accident diagnosis. Indeed, the gamma spectra obtained after a severe reactor core accident are complex because they are composed of hundreds of lines of short-lived fission products and Fukushima accident demonstrated a lack in robustness of data interpretation during a crisis. MAGIX allows a complete and entirely automatic analysis of the spectra, with identification of radionuclides and calculation of activities. It can analyze spectra measured by detectors with excellent resolution such as HPGe detectors as well as detectors with medium resolution (e.g. CZT and LaBr3). For most detectors, the analysis of the spectra can be done without a detection efficiency curve because its process can include the calculation of a relative detection efficiency. MAGIX accepts spectra corresponding to any experimental setup (energy slope, energy range, resolution, absorber, etc.). However, these experimental conditions can have an impact on the quality of the results. Results on spectra simulated in different configurations showed that the analysis of the HPGe spectrum with the user defined efficiency and with the MAGIX detection efficiency were close. Furthermore, they also showed that the accuracy of activities was similar with increasing energy slopes but decreased with resolution degradation, with fewer correctly identified radionuclides in this case.

A tensorial formalism adapted to the case of symmetric-top molecules has been recently developed in Dijon (El Hilali et al., J Quant Spectrosc Radiat Transf 2010;111, 1305–1315) [18]. It is based on the O ( 3 ) ⊃ C ∞ v ⊃C3v group chain and allows a systematic expansion of the Hamiltonian and dipole moment operators, including all possible interactions for a given rovibrational polyad system. This suite of programs is used to analyze and simulate the mid-infrared spectrum of methyl iodide in order to test its performance. The v6 fundamental band has been recorded using the FTIR Bruker HR125 at the AILES beamline of the SOLEIL Synchrotron facility with the Globar internal source. 3882 lines up to J=61 were assigned and fitted with only 16 tensorial parameters.

International audience; After the Fukushima accident, it became essential to have a way to monitor in real time the evolution of a nuclear reactor during a severe accident, in order to react efficiently and minimize the industrial, ecological and health consequences of the accident. Among gaseous fission products, the tetroxide of ruthenium RuO$_4$ is of prime importance since it has a significant radiological impact. Ruthenium is a low volatile fission product but in case of the rupture of the lower head by the molten corium, the air entering into the vessel oxidizes Ru into gaseous RuO$_4$, which is not trapped by the Filtered Containment Venting Systems. To monitor the presence of RuO$_4$ allows making a diagnosis of the core degradation and quantifying the release into the atmosphere.To monitoring the presence of RuO$_4$, FTIR measurement was selected. To study the feasibility of the monitoring, high-resolution IR measurements were realized at the French synchrotron facility SOLEIL on the infrared beam line AILES. Thereafter theoretical calculations were done to simulate the FTIR spectrum to describe the specific IR fingerprint of the molecule for each isotope and based on its partial pressure in the air.

International audience; Following the Fukushima accident, a lot of recommendations was drawn by international organizations (IAEA, OECD, NUGENIA network ) in order to improve the safety in such accidental conditions and mitigate their consequences. One of these recommendations was to improve the robustness of the instrumentation, which was dramatically lacking at Fukushima, as well as to better determine the Source Term involved in nuclear accident.The DECA-PF project (Diagnosis of a degraded reactor core through Fission Product measurements) was elaborated in this context and selected as one of 21 collaborative RandD projects in the field of nuclear safety and radioprotection, funded in May 2013 by the French National Research Agency.Over the months following the Fukushima accident, a CEA crisis team was held in order to analyze on-line the situation taking into account the data delivered by TEPCO and other organizations. Despite the difficulties encountered concerning the reliability of these data, the work performed showed the high capacity of Fission Products (FP) measurements to get a diagnosis relative to the status of the reactors and the spent fuel pools (SFP). Based on these FP measurements, it was possible to conclude that the main origin of the releases was coming from the cores and not from the SFP, in particular for SFP-4 which was of high concern, and that the degradation level of the reactors was very large, including probably an extensive core melting. To improve the reliability of this kind of diagnosis, the necessity to get such measurements as soon as possible after the accident and as near as possible from the reactor was stressed.In this way the present DECA-PF project intends to develop a new and innovative instrumentation taking into account the design of the French nuclear power plants on which sand bed filters have been implemented for severe accident management. Three complementary techniques, devoted to measure the FP release on-line, are being studied Gamma spectrometry, with an industrial objective to build a prototype aimed at improving the capacity of the present radiation monitoring system,Gas chromatography, for the quantification of the fission gases (Xe, Kr) as well as potential carbon oxides produced in case of Molten Corium Concrete Interaction,Optical absorption spectroscopy, the objective of this most innovative technique being to quantify the tetra-oxide of ruthenium, which could be produced in case of lower head failure, and the gaseous forms of iodine (molecular and organic) released in the environment.A global description and the present status of this project is presented, focusing on the Source Term establishment at the outlet stack of the sand bed filters and on the perspectives of implementation of the on-line gamma spectrometry equipment.

International audience; Iodine is a highly radio-toxic element, due to its affinity to the thyroid, and represents the major part of the radioactivity released during a nuclear accident. In the context of nuclear safety and radio-protection, we are interested in identifying the iodine gaseous species which are released, in the nuclear power plants, under molecular (I$_2$) and organic (CH$_3$I) forms. Therefore, we are working on providing a spectroscopic database for both species. While the infrared spectrum of the ν6 band of methyl iodide was previously studied, only 4000 lines were assigned. We present the rovibrational analysis of a high quality experimental spectrum, of this band, recorded at the AILES beamline of the sychrotron SOLEIL, (780-850 cm$^{−1}$) with the glowbar internal source.The analysis of this incomplete spectrum was accomplished in collaboration with the LISA and led to 5000 experimental frequencies accurately measured at a resolution of 10$^{−3}$ cm$^{−1}$. The analysis of the full spectral range is in progress. On the other hand, we tested the C3$v$TDS package of the XTDS$^2$ program developed in Dijon on the CH$_3$I prototype molecule. These results will be shown and discussed. In the case of the molecular iodine, we are developing, in collaboration with the university of Joseph Fourier in Grenoble, an IBB-CEAS (Incoherent Broad Band Cavity Enhanced Absorption Spectroscopy) to measure its absorption spectrum at 520 nm.