NANTeL - National Academy for Nuclear Training e-Learning Radiation Protection and ALARA Questions and Answers 1 — Questions and Answers
Question 1: Which of the following best defines the ALARA principle?
- A philosophy to use engineering and administrative controls to prevent any radiation exposure.
- A regulatory requirement to keep radiation doses below the annual federal limit of 5,000 mrem.
- Making every reasonable effort to maintain radiation exposures as far below the dose limits as is practical. (Correct answer)
- The mandatory use of time, distance, and shielding on every radiological job, regardless of dose rates.
Correct answer: Making every reasonable effort to maintain radiation exposures as far below the dose limits as is practical.
ALARA, an acronym for "As Low As Reasonably Achievable," is a core principle and regulatory requirement in radiation protection. It means making every reasonable effort to keep radiation exposures as far below the established dose limits as is practical, taking into account technology, economics, and other societal factors. It is not about eliminating all exposure or simply staying under the limit, but about optimizing protection.
Question 2: A worker needs to perform a task in a high radiation area with a dose rate of 200 mrem/hr. The worker's administrative dose limit for the week is 100 mrem. What is the maximum time the worker can spend in the area to remain within their administrative limit?
- 15 minutes
- 60 minutes
- 30 minutes (Correct answer)
- 45 minutes
Correct answer: 30 minutes
To calculate the maximum allowable time, divide the dose limit by the dose rate. Time = Dose Limit / Dose Rate. In this scenario: Time = 100 mrem / 200 mrem/hr = 0.5 hours. 0.5 hours is equal to 30 minutes. This calculation is a fundamental application of the 'Time' principle in radiation protection.
Question 3: According to the inverse square law, if a worker doubles their distance from a point source of radiation, how will their exposure rate change?
- It will be reduced to one-half of the original rate.
- It will be reduced to one-quarter of the original rate. (Correct answer)
- It will be reduced by a factor of two.
- It will not change.
Correct answer: It will be reduced to one-quarter of the original rate.
The inverse square law states that the intensity of radiation from a point source is inversely proportional to the square of the distance from the source. Therefore, if you double the distance (multiply by 2), you reduce the exposure rate by a factor of 2 squared, which is 4. The new exposure rate will be one-quarter of the original.
Question 4: Which of the following is considered an engineering control for radiation protection?
- Posting a "Caution - Radiation Area" sign.
- Requiring workers to wear a self-reading dosimeter (SRD).
- Conducting a pre-job ALARA briefing.
- Installing permanent lead shielding around a pipe. (Correct answer)
Correct answer: Installing permanent lead shielding around a pipe.
Engineering controls are physical modifications to a facility or equipment to reduce hazards. Installing permanent lead shielding is a physical barrier designed to reduce radiation levels. Signage, dosimetry, and briefings are all examples of administrative controls, which are rules and procedures to reduce exposure.
Question 5: A nuclear worker's annual occupational dose limit for the whole body (Total Effective Dose Equivalent - TEDE) as set by the NRC is:
- 100 mrem
- 500 mrem
- 5,000 mrem (Correct answer)
- 50,000 mrem
Correct answer: 5,000 mrem
The U.S. Nuclear Regulatory Commission (NRC) sets the annual occupational dose limit for adults at 5,000 mrem (or 5 rem) for the Total Effective Dose Equivalent (TEDE). This limit is designed to keep the risk to radiation workers at a level comparable to other safe industries.
Question 6: What is the primary purpose of an Administrative Control Level or Administrative Dose Limit?
- To replace the federally mandated dose limits set by the NRC.
- To provide an early warning and prevent workers from approaching their legal dose limits. (Correct answer)
- To set dose limits for members of the public outside the facility.
- To measure the effectiveness of shielding materials.
Correct answer: To provide an early warning and prevent workers from approaching their legal dose limits.
Administrative Dose Limits are set by the licensee (the nuclear facility) at levels below the legal limits established by the NRC. Their purpose is to act as a trigger point for investigation and action, ensuring that workers' doses are properly managed and that they do not approach their legal annual limits. This is a key part of implementing the ALARA philosophy.
NANTeL - National Academy for Nuclear Training e-Learning Radiation Protection and ALARA Questions and Answers 1
Which of the following best defines the ALARA principle?