"This report of the National Council on Radiation Protection and Measurements (NCRP) is concerned with radiations produced by accelerators of charged particles having energies from 9.1 to 100 MeV. The material in this report includes recommendations concerning structural shielding and details of accelerator-facility design as they pertain to radiation protection. The scientific committee responsible for the preparation of this report was charged with preparing a guide to good practice in radiation protection for all types of particle accelerators, taking into full consideration their broad application in research, medicine, and industry. In carrying out this objective, the committee has endeavored to organize into a single report the recommendations and guidelines for the many accelerator designs, performance ratings, and applications, without resorting to over-generalization or undue conservatism. There is some overlap of this report with the coverage of other NCRP reports, but an attempt has been made to limit duplication of material except where it is justified for the sake of continuity, or because of the need to complement the coverage of the following existing NCRP reports, or to update their information and recommendations: NCRP Report Nos. 14 (1954a); 31 (1964b); 34 (1970a), which was superseded by NCRP Report No. 49 (1976); 38 (1971a)." --From the Preface, page iii.