All tube housings must be constructed so that leakage radiation at a distance of 1 meter from the target cannot exceed _____ when the tube is operated at any of its specified ratings.

The maximum allowed leakage radiation from tube housings is set to ensure patient and personnel safety by minimizing exposure to ionizing radiation. According to established safety standards, the limit for leakage radiation at a distance of 1 meter from the target must not exceed 100 mR/hour when the x-ray tube is operated at any of its specified ratings.

This standard is crucial because it helps ensure that the radiation emitted from the x-ray tube when not in use is kept at a safe level, thus reducing the risk of unnecessary radiation exposure to individuals who may be near the equipment. This regulatory measure protects both patients who are receiving x-ray examinations and healthcare staff who operate the radiologic equipment.

The other values, such as 50 mR/hour, 200 mR/hour, and 500 mR/hour, exceed or do not align with the stipulated safety regulations, thus underscoring the importance of the 100 mR/hour figure as the correct standard for leakage radiation.