Shielding Calculations

To determine the shielding necessary for a diagnostic x-ray installation certain preliminary information is essential. The required thickness of shielding can be calculated using the formular. In both instances answers to the following questions are required:

 

1. What is the distance between the nearest point of the area to be shielded and the mean operational position of the x-ray tube?

2. Is the area to be designated as a controlled or uncontrolled area, i.e. will the area be occupied by radiation workers (subject to the limit of 20 mSv per year) or non-radiation workers (subject to the limit of 1 mSv per year)?

3. What will be/is the occupancy factor (T) of the area? The occupancy factor is defined as the time an area is normally occupied, expressed as a fraction of the working week.

4. Will the intervening shield between the x-ray tube and the occupied area act as a primary or secondary protective barrier, i.e. will the barrier be required to attenuate the direct useful beam or stray (leakage and scattered) radiation only?

5. What will the use factor (U) of the required protective barrier? The use factor is defined as the fraction of the operational time during which the useful beam will be/is directed at the barrier or area under consideration.

6. What will be/is the workload (W) of the x-ray unit? The workload indicates the operational time of an x-ray machine expressed in terms of milliampere-minutes per week.

7. What will be/is the maximum and average operating tube potential, and output?