Proposals are made for improving the heterogeneous diffusion procedure for reactor design and operating calculations. The procedure is based on the use of pin-by-pin properties for the assemblies and on low-order discretization for the reactor diffusion calculation. It proposes the introduction of a second-generation superhomogénéisation equivalence technique between the flux and cross-section edit calculations to yield heterogeneous diffusion properties consistent with exact control rod worth calculations. This equivalence technique is designed to preserve the pin-cell reaction rates and the assembly integrated fluxes. Two-group colorset benchmarks are proposed to validate the new procedures. Numerical results are also given for typical fine-group test cases.