# Analysis of the trapu and doublon irradiations in phenix for the experimental validation of the darwin package for fast reactors

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Abstract : The prospect of reprocessing the fissile and fertile subassemblies of the PHENIX reactor, as well as the development of the 4th generation Fast Reactors make it essential to have a validated code for fuel inventory and fuel cycle calculations in Fast Reactors. This validation is based on irradiation experiments that were performed in PHENIX between 1977 and 1981. We have analyzed two of these experiments (i.e. TRAPU and DOUBLON) with the ERANOS-2.2 code system, associated with its nuclear data libraries JEFF-3.1.1 and the depletion module DARWIN-2.3.2. For each experiment, we have computed Calculation/Experiment (C/E) ratios for different isotopic ratios at the end of the irradiation. A fluence adjustment was performed in the calculations in order to match the $^{148}$Nd production. During the TRAPU experiment, ten well characterized fuel pins – of three different enrichment and Pu isotopic vectors – were placed in two subassemblies near the center of the PHENIX core between 1977 and 1979. The analysis of this experiment shows a good C/E agreement for the main isotopes: $^{234}$U, $^{235}$U, $^{236}$U, $^{239}$Pu, $^{240}$Pu, $^{242}$Pu and $^{241}$Am. Discrepancies on some C/E’s ($^{237}$Np, $^{238}$Pu, $^{241}$Pu, ...) are consistent with previous interpretations of TRAPU and with the analysis of separated samples irradiation experiments like PROFIL, that can be interpreted in terms of nuclear data. The purpose of the DOUBLON experiment was the validation of radial fertile blankets calculations, based on a detailed study of two subassemblies – of the first and second rows - that were irradiated in PHENIX between 1978 and 1981. Samples were taken at various heights in 9 fertile pins, chosen at increasing distances from the core. The analysis of this experiment shows that the C/E’s on the final amounts of $^{234}$U, $^{235}$U, $^{236}$U and $^{239}$Pu are excellent. This is all the more important as they are the main isotopes ine final inventory. Concerning the $^{240}$Pu - which is produced in much smaller quantities – the average C/E is also very good, but with a high uncertainty coming from the most peripheral pin. On the contrary, the C/E’s of the $^{238}$Pu, $^{241}$Pu and $^{242}$Pu are higher, with a very important pin-to-pin dispersion. These nuclei are produced in a very small amount, in total they represent less than one thousandth of the Pu produced. They are mainly produced by successive capture reactions on $^{238}$U, which have significant cross-sections only in energy groups where the neutron flux is extremely low. Moreover, some of these resonant cross-sections are described in only one or two groups of our energy mesh, resulting in a large calculation uncertainty on the production rate of $^{238}$Pu, $^{241}$Pu and $^{242}$Pu.
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Conference papers
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Cited literature [11 references]

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• HAL Id : cea-02509740, version 1

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J.-F. Lebrat, J. Tommasi, V. Pascal, R. Eschbach. Analysis of the trapu and doublon irradiations in phenix for the experimental validation of the darwin package for fast reactors. Global 2015 - 21st International Conference & Exhibition: " Nuclear Fuel Cycle for a Low-Carbon Future", Sep 2015, Paris, France. ⟨cea-02509740⟩

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