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Abstract. The status of the Joint Evaluated Fission and Fusion file (JEFF) is described. JEFF-3.1 comprises a significant update of actinide evaluations, materials evaluations that have emerged from various European nuclear data projects, the activation library JEFF-3.1/A, the decay data and fission yield sub-libraries, and fusion-related data files from the EFF project. The revisions were motivated by the availability of new measurements, modelling capabilities and trends from integral experiments. Validations have been performed, mainly for criticality, reactivity temperature coefficients, fuel inventory and shielding of thermal and fast systems. Compared with earlier releases, JEFF-3.1 provides improved performance with respect to a variety of scientific and industrial applications. Following on from the public release of JEFF-3.1, the French nuclear power industry has selected this suite of nuclear applications libraries for inclusion in their production codes.

The chlorine nuclear quadrupole resonance has been used to determine the C-C1 bond directions in a single crystal of 1,2,4,5-tetrachlorobenzene. With these data, the phases for the (0kl) structure amplitudes were determined directly and used in a Fourier projection. The results for the n.q.r. measurements and the two-dimensional X-ray analysis agree within 1-2 ° in the bond orientations.The angle between adjacent C-C1 bonds in the molecule is 63± l°. The interpretation in terms of strained models is discussed in relation to the n.q.r, experiments.

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