Practice use of building factors in shielding design for an accelerator

In X-rays shielding the contribution of the scattering radiation generated in the barrier could be important, this component usually doesn't take into account. The calculation is generally perform with a simple but conservative formalism. This contribution is able to take into account by the use of buildup factors, but their tables are for monochromatic gamma rays only. Based in theses tables we calculate the buildup factors for an x ray polychromatic spectrum beam provided by linear accelerator and we parametric ed the results for his practical use. (Author) 9 refs