Excessive leakage radiation measured on two mobile X-ray units due to the methodology used by the manufacturer to calculate and specify the required tube shielding.

During the quality control (QC) procedure of a new mobile X-ray unit, it was revealed that the leakage radiation was well in excess of the current limit of 1 mSv h(-1). As a result, this unit was returned to the vendor company and it was replaced by a new unit of the same brand and model. Leakage measurements revealed that the second unit presented the same problem. After consulting the vendor company and the tube manufacturer, it was discovered that the excessive leakage identified in these two X-ray units was not due to a defective construction, but due to the methodology with which the maximum permissible leakage and therefore the tube shielding had been determined. In this study, the implications of using such methods to the radiation protection of personnel and public are discussed.