Analytical developments for high precision isotope measurements on transmutation target in the phenix fast neutron reactor

H. Isnard (1) , G. Ferlay (1) , S. Eymard (1) , O. Vigneau (1) , J-F. Lebrat (1) , M. Phelip (1) , T. Vercouter (2)

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)
2 DPC - Département de Physico-Chimie

The objective of the PROFIL-R (fast spectrum) and PROFIL-M (moderated spectrum) experiments, performed between 2003 and 2008 in the French fast neutron reactor Phénix, was to collect accurate information on the total capture integral cross sections of the principal heavy isotopes and some important fission products in the spectral range of fast reactor. The method consists of the irradiation of pure isotope samples and the determination of the composition change induced by irradiation. The elements present in powder form are representative of actinides and fission products present in irradiated fuels and cover all the applications for which accurate capture integral cross section are necessary. Then, accurate measurements of isotopic compositions and concentrations of the elements (actinides and fission products) before and after irradiation are required. The major difficulty for the analyses of products is the low quantity of the initial powder enclosed in steel container (3 to 5 mg) and the very low quantities of products formed (several $\mu$g) after irradiation. During several years developments have been performed in different laboratories of the CEA for the conception of a system implanted in shielded cell installations to open the steel container, collect the integrality of the powder and quantitatively dissolve each product. For several powders, like metallic ruthenium, metallic silver or metallic rhodium, this last step was a challenge due to the very high resistance of these metals to acid solutions. After recuperation and dissolution the second stage consists of mass spectrometric measurements in order to obtain isotope and elemental ratio at uncertainty of few per mil level. As very low measurement uncertainties are required for these applications, elemental and isotopic measurements are usually performed with state of the art mass spectrometric techniques such as thermal ionization mass spectrometry (TIMS) and multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS) associated with the isotope dilution technique (ID). Furthermore it requires preliminary chemical separation to eliminate the elements which could prevent ionization and/or generate isobaric interferences in the mass spectrum of the analytes during measurements, thus leading to non-accurate isotopic analysis. We present the axes of analytical developments performed in the Nuclear, isotope and elemental analytical development laboratory (LANIE) to acquire accurate isotope ratios. Innovative method of separation like the hyphenation of liquid chromatography with ICPMS and MC-ICPMS or the use of collision reaction cell present in recent generation of ICPMS, have been developed. Several examples of analyses of irradiated transmutation targets will be presented. These various analytical developments demonstrate the considerable gains that can be expected in the near future in terms of sample amounts, handling time, and waste production associated to the high precision elemental and isotopic characterization of irradiated samples.

Domains: Nuclear Experiment [nucl-ex]; Nuclear Theory [nucl-th]

H. Isnard, G. Ferlay, S. Eymard, O. Vigneau, J-F. Lebrat, et al.. Analytical developments for high precision isotope measurements on transmutation target in the phenix fast neutron reactor. GLOBAL 2015, Sep 2015, Paris, France. ⟨cea-02509737⟩