AbstractThe full-range Monte Carlo program RECAP was used in a consistent analysis of parameters measured in seven H2O-moderated uranium lattices: four were lattices of slightly enriched rods and three were natural-uranium-slab lattices. The most important parameters were: epithermal-to-thermal ratios for238U capture (ρ28) and for235U fission (δ25), ratio of238U fission-to-235U fission (δ28), eigenvalue, integral fast/epithermal spectrum comparisons with a variety of detectors, and resonance integrals for isolated uranium and UO2rods (calculated with the Monte Carlo program RESQ, supplemented by ZUT and TUZ at higher energies). The analysis of these lattices was fairly unambiguous and served to test the input nuclear data for238U,235U, and H2O. With one exception, leakage was small (<20%) and parameters were measured in nearly asymptotic flux spectra. These covered a wide range of hardness as reflected in the change of parameters:ρ28ranged from 0.5 to 12;δ25from 0.04 to 1.1; andδ28from 0.05 to 0.44. The Monte Carlo cell calculations were corrected for leakage by means of the homogenized lattice programs P3MG and MUFT-MAGMA. With a straightforward choice of current“best”nuclear data, the calculations reproduce virtually all the parameters over the whole range of lattices. There are two qualifications: some reduction of smooth238U capture integral is required to match the lattice measurements (by an amount barely compatible with the isolated rod measurements), and there is too much calculated epithermal235U fission in the very tight lattices.