AbstractGeneralized bias operators (GBOs) can be derived from the differences in the calculations of a nuclear system by two methods. One method is accurate and expensive and the other one is less accurate and less expensive. These GBOs serve to improve the accuracy of the less accurate methods for systems similar to the original one. Two applications are discussed. In the first application, diffusion-type calculations with GBOs give transport calculations quality results. In the second application, one-dimensional calculations with GBOs replace two-dimensional calculations. The method is applied for calculating the Zion-2 core.