Revised nomograms for calculating thicknesses of shields against direct X-r
ays emitted at voltages of 75 to 450 kV are given. The nomograms have been
obtained for the most common shielding materials, such as lead, iron, and c
oncrete, with due account of accurately measured spectra of primary radiati
on from the source, contribution of the secondary radiation, and recently i
ntroduced NRB-96 regulations of radiation safety.