Fundamentals Flashcards
6 cards from real IRRSP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Fundamentals flashcards as text
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?
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.
Which of the following is considered a primary characteristic of a stochastic effect of radiation exposure?
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).
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?
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.
The three fundamental principles for controlling external radiation exposure, often associated with the ALARA concept, are:
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.
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:
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.
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?
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).