The object in planning x-ray protection for any installation is to reduce the x-ray intensity at all positions where personnel will be stationed to a value such that no one will receive more than 0.1 r during any 24-hour period. No hard and fast rules need be laid down for accomplishing this; the methods to be used are best left to the ingenuity of those making the plans. Almost any space can be made safe against x-rays by the use of lead or concrete walls of sufficient thickness, though in practice such an installation would probably be considered prohibitively expensive, especially when protection against very penetrating radiation is required. The alternative is to consider other methods of protection to be used in addition to radiation barriers. In the interest of economy, full consideration should therefore be given to all three of the following factors: (1) distance from barrier to x-ray source; (2) direction of x-ray beam; (3) radiation barriers. Distance from Barrier to X-Ray Source: The intensity...