CHP Radiation Protection Principles 3 — Questions and Answers
Question 1: The committed effective dose equivalent (CEDE) accounts for dose from:
- External radiation fields only
- Internally deposited radionuclides integrated over 50 years (Correct answer)
- Neutron activation products in the body
- Skin contamination measured at the time of intake
Correct answer: Internally deposited radionuclides integrated over 50 years
CEDE integrates the dose from internally deposited radionuclides over a 50-year period (70 years for children) following a single intake.
Question 2: Which radiation protection quantity is used to assess stochastic risk across different tissues and organs?
- Absorbed dose
- Equivalent dose
- Effective dose (Correct answer)
- Kerma
Correct answer: Effective dose
Effective dose sums equivalent doses to individual organs weighted by tissue weighting factors (wT), reflecting whole-body stochastic risk.
Question 3: A contaminated surface reads 10,000 dpm/100 cm². This value represents:
- Dose rate from the surface
- Surface contamination level in disintegrations per minute (Correct answer)
- Airborne radioactivity concentration
- Derived air concentration (DAC)
Correct answer: Surface contamination level in disintegrations per minute
Disintegrations per minute per 100 cm² (dpm/100 cm²) is a standard unit for quantifying surface contamination activity.
Question 4: What does the term 'specific activity' describe?
- Activity per unit energy of a radionuclide
- Activity per unit mass of a radioactive material (Correct answer)
- Dose rate at a specific distance from a source
- Number of disintegrations per specific time interval
Correct answer: Activity per unit mass of a radioactive material
Specific activity is the radioactivity per unit mass (e.g., Bq/g or Ci/g) of a given radionuclide or radioactive material.
Question 5: Under the concept of optimization in radiation protection, the goal is to keep doses:
- At zero whenever technically feasible
- Below regulatory limits only, without further consideration
- As low as reasonably achievable considering economic and social factors (Correct answer)
- At the same level for all workers regardless of job tasks
Correct answer: As low as reasonably achievable considering economic and social factors
Optimization (ALARA) requires reducing doses below limits to levels that are reasonable considering economic and societal benefit versus detriment.
Question 6: The dose equivalent in tissue from fast neutrons is primarily determined by:
- The neutron's charge interacting with orbital electrons
- Nuclear recoil protons and heavier ions produced by elastic scattering (Correct answer)
- Gamma rays emitted when neutrons scatter off nuclei
- Bremsstrahlung radiation from neutron deceleration
Correct answer: Nuclear recoil protons and heavier ions produced by elastic scattering
Fast neutrons lose energy primarily through elastic scattering with hydrogen nuclei, producing high-LET recoil protons that cause biological damage.
Question 7: Which statement correctly describes the inverse square law for point sources?
- Dose rate is inversely proportional to distance
- Dose rate is inversely proportional to the square root of distance
- Dose rate is inversely proportional to distance squared (Correct answer)
- Dose rate decreases linearly with distance
Correct answer: Dose rate is inversely proportional to distance squared
For an isotropic point source, dose rate decreases with 1/d², so doubling the distance reduces exposure by a factor of four.
CHP Radiation Protection Principles 3
The committed effective dose equivalent (CEDE) accounts for dose from: