ASNT Industrial Radiography Radiation Safety Practice Test

How many mR does a radiographer receive after making four 10 min exposures in a 100 mR/h field?

1. 100 mR

2. 93.3 mR

3. 66.7 mR

4. 20 mR

The correct answer is: 66.7 mR

To determine the amount of radiation a radiographer receives after making four 10-minute exposures in a 100 mR/h field, we first need to calculate the total exposure time in hours. Four exposures of 10 minutes each total 40 minutes, which is equal to 2/3 of an hour (40 minutes divided by 60 minutes). Next, we calculate the dose received during that time using the rate of 100 mR/h. Since the exposure lasts for 2/3 of an hour in a 100 mR/h field, the radiation dose received can be calculated as follows: Dose = Exposure Rate × Time Dose = 100 mR/h × (2/3) h = 66.67 mR This dose rounds to approximately 66.7 mR, which matches the correct answer. Thus, the radiographer would receive 66.7 mR after completing the four 10-minute exposures in a 100 mR/h field. This demonstrates a fundamental concept in radiation safety: the total dose is directly proportional to both the exposure rate and the duration of exposure.