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The Daya Bay Reactor Neutrino Experiment is designed to determine precisely the neutrino mixing angle θ 13 with a sensitivity better than 0.01 in the parameter sin 2 2θ 13 at the 90% confidence level. To achieve this goal, the collaboration will build eight functionally identical antineutrino detectors. The first two detectors have been constructed, installed and commissioned in Experimental Hall 1, with steady data-taking beginning September 23, 2011. A comparison of the data collected over the subsequent three months indicates that the detectors are functionally identical, and that detector-related systematic uncertainties exceed requirements.

The Daya Bay experiment was the first to report simultaneous measurements of reactor antineutrinos at multiple baselines leading to the discovery ofν e oscillations over km-baselines. Subsequent data has provided the world's most precise measurement of sin 2 2θ 13 and the effective mass splitting ∆m 2 ee . The experiment is located in Daya Bay, China where the cluster of six nuclear reactors is among the world's most prolific sources of electron antineutrinos. Multiple antineutrino detectors are deployed in three underground water pools at different distances from the reactor cores to search for deviations in the antineutrino rate and energy spectrum due to neutrino mixing. Instrumented with photomultiplier tubes, the water pools serve as shielding against natural radioactivity from the surrounding rock and provide efficient muon tagging. Arrays of resistive plate chambers over the top of each pool provide additional muon detection. The antineutrino detectors were specifically designed for measurements of the antineutrino flux with minimal systematic uncertainty. Relative detector efficiencies between the near and far detectors are known to better than 0.2%. With the unblinding of the final two detectors' baselines and target masses, a complete description and comparison of the eight antineutrino detectors can now be presented. This paper describes the Daya Bay detector systems, consisting of eight antineutrino detectors in three instrumented water pools in three underground halls, and their operation through the first year of eight detector data-taking.

The design and development of a water-soluble heterocyclic ligand are believed to be an alternative way for improving the separation efficiency of actinides from lanthanides. Herein, we designed and synthesized a novel hydrophilic multidentate ligand: disulfonated N,N′-diphenyl-2,9-diamide-1,10phenanthroline (DS-Ph-DAPhen) with soft and hard donor atoms, as a masking agent in aqueous solutions for Am(III) separation. The combination of N,N,N′,N′-tetraoctyldiglycolamide in kerosene and DS-Ph-DAPhen in aqueous phases could separate Am(III) from Eu(III) across a range of nitric acid concentrations with very high selectivity. The coordination behaviors of Eu(III) with DS-Ph-DAPhen in aqueous solutions were studied by UV−vis titration, electrospray ionization mass spectrometry, and Fourier transform infrared spectra. The results indicated that Eu(III) ions could form both 1:1 and 1:2 complexes with the DS-Ph-DAPhen ligand in aqueous solution. Density functional theory calculation suggests that there are more covalent characters for Am−N bonds than that for Eu−N bonds in the complexes, which supports the better selectivity of the DS-Ph-DAPhen ligand toward Am(III) over Eu(III). This work demonstrates a feasible alternative approach to separating trivalent actinides from lanthanides with high selectivity.

Separation of trivalent actinides (An(iii)) and lanthanides (Ln(iii)) in spent nuclear fuel reprocessing is extremely challenging mainly owing to their similar chemical properties. Two amine-type reagents, tetrakis(2-pyridyl-methyl)-1,2-ethylenediamine (TPEN) and its hydrophobic derivative N,N,N',N'-tetrakis((4-butoxypyridin-2-yl)methyl)-ethylenediamine (TBPEN), have been identified to possess a selectivity for Am(iii) over Eu(iii). In this work, the structures, bonding nature, and thermodynamic behaviors of the Am(iii) and Eu(iii) complexes with these two ligands have been systematically studied via scalar relativistic density functional theory (DFT) calculations. According to Mayer bond order and the quantum theory of atoms in molecules (QTAIM) analyses, interactions between the ligands and metal cations exhibit some degree of covalent character with relatively more covalency for Am(iii) complexes. In comparison with TPEN, TBPEN has better extractability but worse separation ability for Am(iii) and Eu(iii). Four nitrogen atoms in pyridine moieties may be responsible for the different extraction abilities of TPEN and TBPEN, while two nitrogen atoms in amine chains of these ligands appear to play more important roles in the separation of Am(iii)/Eu(iii). These different extraction behaviors may be attributed to the longer and thinner 'capsule' shaped TBPEN ligand compared to TPEN. Our study might provide new insights into understanding the selectivity of the amine-type ligands toward minor actinides, and pave the way for designing new TPEN derivatives for extraction and separation of An(iii)/Ln(iii).