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For the validation of the recently released evaluated nuclear data files JEF-2 and ENDF/B-VI a first set of benchmark calculations for thermal systems important for criticality safety and LWR-neutronics were performed and compared with corresponding calculations based on JEF-1 and the MCNP-3B library (ENDF/B-IV, ENDL-85). The processing of the JEF-2 and ENDF/B-VI data which are given in the ENDF-6 format was performed by an updated version of the nuclear data processing system NJOY. Both multigroup libraries with 316 groups in MATXS-format and MCNP-libraries (continuous data with a very fine energy resolution) based on JEF-2 and ENDF /B-VI were generated. The ORNL uranyl nitrate benchmarks as well as the PNL Pu nitrate benchmarks were analysed by deterministic (ANISN/ONEDANT-S N -method) and Monte Carlo methods (MCNP-3B). The group constants for the S N -calculations were generated by a combination of TRAMIX and RSYST/CGM.

Scattering laws S(α,β) were derived in ENDF-6 format for the most important materials as liquid H2, D2, 4He and solid Be, Bi used in cold and superthermal neutron sources by considering the incoherent as well as the coherent scattering dynamics at working temperature. For cold and superthermal neutron source design calculations including the determination of heat production coupled n-γ cross-section matrices and Kerma factors were generated.