This paper focuses on the data reconciliation technique (DR) in case of numerous biases. DR improves the degree of confidence in available information and generates consistent data. The inventory and analysis of the plant data (position and type of sensors ...) enable an evaluation of the process redundancy. Classical Gross Error Detection and Identification (GEDI) techniques delete the biased variables, decreasing the redundancy. This leads to information loss and possibly an inability to apply DR. The methodology proposed here combines DR, based on a reduced model, and rigorous simulations to locate and estimate multiple biases and to make data consistent in case of inter-connected flows. This methodology is applied to the nuclear fuel recycling process within the scope of a state estimation tool built on a process simulation code.

After the accident at the Fukushima Daiichi Nuclear Power Station occurred in March 2011, the new regulatory requirements for nuclear fuel fabrication facilities were enforced in December 2013, which require licensees of UF6 enrichment and reconversion activity to evaluate chemical effects on the work environment after a UF6 leakage in an accident that could lead to severe accidents. Preparatory to enforcement of this new regulatory requirements, the Incorporated Administrative Agency, Japan Nuclear Energy Safety Organization (JNES), has, as one of the efforts to consider the evaluation methods of UF6 chemical effects and criteria for UF6 leakage required for the regulation, investigated and studied UF6 chemical effects and the regulatory statuses in the U.S., France and U.K.. As the result, it was clarified that it is important to evaluate the consequences of UF6 leakage accidents focused on the acute chemical exposure effects. Concerning the evaluation methods of chemical effects, views, methods and items to be considered about acute chemical exposure effects were investigated. The results were issued as the JNES report JNES-RE-2013-2021 1) . In order to share the information on the safety assessment of UF6 chemical effects to the members of OECD/NEA/WGFCS (the Organisation for Economic Co-operation and Development/the Nuclear Energy Agency/the Working Group on Fuel Cycle Safety) as a good practice of the safety assessment of UF6 chemical effects in Japan, outlines of the original JNES report and some of the latest information were shown in this paper.

The synthesis and evaluation of new extractants for spent nuclear fuel reprocessing are described. New bitopic ligands constituted of phenanthroline and 1,3,5-triazine cores functionalized by picolinamide groups were designed. Synthetic routes were investigated and optimized to obtain twelve new polyaza-heterocyclic ligands. In particular, an efficient and versatile methodology was developed to access non-symmetric 2-substituted-4,6-di(6-picolin-2-yl)-1,3,5-triazines from the 1,3,5-triazapentadiene precursor in the presence of anhydride reagents. Extraction studies showed the ability of both ligand series to extract and separate actinides selectively at different oxidation states (U(VI), Np(V,VI), Am(III), Cm(III), and Pu(IV)) from an acidic solution (3 M HNO3). Phenanthroline-based ligands show the most promising efficiency for use in the group actinide extraction (GANEX) process due to a higher number of donor nitrogen atoms and a suitable pre-organization of the dipicolinamide-1,10-phenanthroline architecture.

New functionalized terpyridine-diamide ligands were recently developed for the group actinide separation by solvent extraction. In order to acquire a better understanding of their coordination mode in solution, protonation and complexation of lanthanides(III), americium(III), and uranium(VI) with these bitopic N,O-bearing ligands were studied in homogeneous methanol/water conditions by experimental and theoretical approaches. UV-visible spectrophotometry was used to determine the protonation and stability constants of te-tpyda and dedp-tpyda. The conformations of free and protonated forms of te-tpyda were investigated using NMR and theoretical calculations. The introduction of amide functional groups on the terpyridine moiety improved the extracting properties of these new ligands by lowering their basicity and enhancing the stability of the corresponding 1:1 complexes with lanthanides(III). Coordination of these ligands was studied by density functional theory and molecular dynamics calculations, especially to evaluate potential participation of hard oxygen and soft nitrogen atoms in actinide coordination and to correlate with their affinity and selectivity. Two predominant inner-sphere coordination modes were found from the calculations: one mode where the cation is coordinated by the nitrogen atoms of the cavity and by the amide oxygen atoms and the other mode where the cation is only coordinated by the two amide oxygen atoms and by solvent molecules. Further simulations and analysis of UV-visible spectra using both coordination modes indicate that inner-sphere coordination with direct complexation of the three nitrogen and two oxygen atoms to the cation leads to the most likely species in a methanol/water solution.

The synthesis and evaluation of solvent extraction performance of N,N,N',N'-tetraalkyl-6,6''-(2,2':6',2''-terpyridine)diamides and N,N'-diethyl-N,N'-diphenyl-6,6''-(2,2':6',2''-terpyridine)diamide are reported here. These new bitopic ligands were found to extract actinides in different oxidation states (U(VI), Np(V and VI), Pu(IV), Am(III), and Cm(III)) from 3 M nitric acid. The presence of three soft nitrogen donors led to the selective extraction of actinides(III) over lanthanides(III) (Ce, Eu) and the presence of two amide functional groups grafted to the terpyridine unit allowed the extraction to occur from a highly acidic medium by minimizing the basicity of the ligand. Ligands bearing long alkyl chains (C4 and C8) or phenyl groups showed increased performances in a polar diluent like nitrobenzene.