NRRPT - National Registry of Radiation Protection Technicians Dosimetry and Exposure Control Questions and Answers

Question 1

A radiation worker needs to perform a task in a high radiation area with a dose rate of 150 mrem/hr. The administrative dose limit for this task is 100 mrem. What is the maximum stay time permitted for the worker to complete the task without exceeding the administrative limit?

Accepted Answer

40 minutes

Answer

Stay time is calculated by dividing the allowed dose by the dose rate. In this case, Stay Time = 100 mrem / 150 mrem/hr = 0.667 hours. To convert this to minutes, multiply by 60: 0.667 hours * 60 minutes/hour = 40 minutes.

Question 2

Which of the following personal dosimeters uses a crystalline solid that, when heated after exposure to ionizing radiation, emits light proportional to the dose received?

Accepted Answer

Thermoluminescent Dosimeter (TLD)

Answer

A Thermoluminescent Dosimeter (TLD) contains a crystalline material (like Lithium Fluoride) that traps energy from ionizing radiation. When heated, this stored energy is released as visible light, and the amount of light is proportional to the radiation dose absorbed by the crystal.

Question 3

A technician measures a dose rate of 400 mR/hr at a distance of 2 feet from a point source. If the technician moves to a distance of 8 feet from the source, what will the new dose rate be, according to the inverse square law?

Accepted Answer

25 mR/hr

Answer

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 (from 2 ft to 8 ft). Therefore, the dose rate will decrease by a factor of 4², which is 16. The new dose rate is 400 mR/hr / 16 = 25 mR/hr.

Question 4

The fundamental principle of ALARA (As Low As Reasonably Achievable) in radiation protection means that:

Accepted Answer

Radiation exposures should be maintained as far below the dose limits as is practical, taking into account social and economic factors.

Answer

ALARA is a cornerstone of radiation safety philosophy. It doesn't just mean staying below regulatory limits, but making every reasonable effort to reduce doses further, balancing the benefits of the reduction against the costs (both economic and social).

Question 5

What is the primary operational difference between an Optically Stimulated Luminescence (OSL) dosimeter and a Thermoluminescent Dosimeter (TLD)?

Accepted Answer

OSL dosimeters can be re-read multiple times, while the signal from a TLD is typically erased upon reading.

Answer

The key difference is the stimulation method. OSLs use light (typically from a laser) to stimulate the detector material, which does not deplete the stored signal, allowing for multiple readouts. TLDs use heat, which releases all the stored energy at once, zeroing out the dosimeter.

(NRRPT) National Registry of Radiation Protection Technicians Practice Test

(NRRPT) National Registry of Radiation Protection Technicians Practice Test

NRRPT - National Registry of Radiation Protection Technicians Dosimetry and Exposure Control Questions and Answers