IRRSP - Industrial Radiography Radiation Safety Personnel Radiation Safety Fundamentals Questions and Answers — Questions and Answers
Question 1: An industrial radiographer measures an intensity of 200 mR/hr at a distance of 3 feet from a sealed source. If the radiographer moves to a distance of 12 feet from the source, what will the new radiation intensity be?
- 50 mR/hr
- 12.5 mR/hr (Correct answer)
- 25 mR/hr
- 100 mR/hr
Correct answer: 12.5 mR/hr
The Inverse Square Law states that radiation intensity is inversely proportional to the square of the distance from the source (I₁d₁² = I₂d₂²). The distance increased by a factor of 4 (12 feet / 3 feet). Therefore, the intensity will decrease by the square of this factor (4² = 16). The new intensity is 200 mR/hr divided by 16, which equals 12.5 mR/hr.
Question 2: Which of the following is considered a primary characteristic of a stochastic effect of radiation exposure?
- A dose threshold must be exceeded for the effect to occur.
- The severity of the effect increases with the dose received.
- The probability of the effect occurring increases with dose. (Correct answer)
- The effect is typically observed within hours or days of exposure.
Correct answer: The probability of the effect occurring increases with dose.
Stochastic effects are probabilistic, meaning their likelihood of occurring increases with the radiation dose, but the severity is not dependent on the dose. Cancer is the primary example. In contrast, deterministic effects have a dose threshold and their severity increases with the dose (e.g., skin reddening).
Question 3: A radiographer needs to perform a 10-minute task in a radiation field of 120 mrem/hr. What is the total dose the radiographer will receive?
- 12 mrem
- 60 mrem
- 20 mrem (Correct answer)
- 1200 mrem
Correct answer: 20 mrem
Total dose is calculated by multiplying the dose rate by the exposure time. First, convert the time to hours (10 minutes / 60 minutes/hour = 1/6 hour). Then, multiply the dose rate by the time: 120 mrem/hr * (1/6) hr = 20 mrem.
Question 4: The three fundamental principles for controlling external radiation exposure, often associated with the ALARA concept, are:
- Monitoring, Documentation, and Reporting
- Calibration, Surveying, and Leak Testing
- Alpha, Beta, and Gamma
- Time, Distance, and Shielding (Correct answer)
Correct answer: Time, Distance, and Shielding
The three cardinal principles of radiation protection to keep doses As Low As Reasonably Achievable (ALARA) are minimizing the time of exposure, maximizing the distance from the source, and using appropriate shielding between the source and the individual.
Question 5: The amount of shielding material required to reduce the intensity of a gamma ray beam to one-half of its original value is known as the:
- Linear Attenuation Coefficient
- Tenth-Value Layer (TVL)
- Half-Value Layer (HVL) (Correct answer)
- Specific Gamma-Ray Constant
Correct answer: Half-Value Layer (HVL)
The Half-Value Layer (HVL) is the defined thickness of a specific material that will reduce the intensity of a radiation beam by 50%. For example, adding one HVL of lead will cut the beam's intensity in half.
Question 6: Which of the following instruments is designed to measure an individual's accumulated radiation dose over a period of time, rather than the instantaneous dose rate?
- Geiger-Mueller (GM) Survey Meter
- Thermoluminescent Dosimeter (TLD) (Correct answer)
- Ion Chamber Survey Meter
- Audible Alarming Ratemeter
Correct answer: Thermoluminescent Dosimeter (TLD)
A Thermoluminescent Dosimeter (TLD) or film badge is a type of personal dosimeter that measures the total accumulated radiation dose received by an individual over a specific period (e.g., a month or a quarter). Survey meters and alarming ratemeters measure the current radiation rate (e.g., mR/hr).
IRRSP - Industrial Radiography Radiation Safety Personnel Radiation Safety Fundamentals Questions and Answers
An industrial radiographer measures an intensity of 200 mR/hr at a distance of 3 feet from a sealed source.
If the radiographer moves to a distance of 12 feet from the source, what will the new radiation intensity be?