Section 8 - Part I Typical Questions

1. Disks or foils of copper, cadmium, or aluminum are often incorporated into thermoluminescent dosimeters (TLDs) in order to:

  1. measure neutrons via the n-alpha reaction. 
  2. facilitate the annealing process. 
  3. filter out high-energy background radiation. 
  4. filter out low-energy background radiation. 
  5. provide information about the photon energy spectrum.

2. A mono-energetic photon beam is measured to have an exposure rate of 100 mR hr-1 at 1 meter. An absorber of 0.2 m thickness ( mu= 6.93 m-1) is placed in the beam. What is the shielded exposure rate at 5 meters from this source?

  1. 1 mR hr-1 
  2. 4 mR hr-1 
  3. 5 mR hr-1 
  4. 20 mR hr-1 
  5. 25 mR hr-1

3. According to ANSI Z136.1 "For the Safe Use of Lasers", what Class applies to a laser which emits light in the visible portion of the spectrum such that eye protection is normally afforded by the aversion response including the blink reflex?

  1. Class 1. 
  2. Class 2. 
  3. Class 3R. 
  4. Class 3B. 
  5. Class 4.

4. The maximum dose rate permitted at any point on the external surface of a package of radioactive material offered for transport in other than a sole-use transport vehicle is:

  1. 2 mrem/hr. 
  2. 5 mrem/hr. 
  3. 25 mrem/hr. 
  4. 50 mrem/hr. 
  5. 200 mrem/hr.

5. Right-angle scattered x-ray radiation exposure measured one meter from the beam of a fluoroscope will be:

  1. about 0.01% of the incident beam at the scatterer. 
  2. about 0.1% of the incident beam at the scatterer. 
  3. about 1% of the incident beam at the scatterer. 
  4. about 10% of the incident beam at the scatterer. 
  5. of little significance and can be ignored for all practical purposes.

6. Most of the documented harmful biological effects in humans from microwave radiation are attributed to hyperthermia. These include damage mainly to the eyes and:

  1. muscle. 
  2. testicles. 
  3. cardiovascular system. 
  4. nervous system. 
  5. skeleton.

7. If an airborne release occurs because of a loss of coolant accident at a light water power reactor in which fuel damage but no core melt occurs, the first radioisotope of concern through the food chain is:

  1 90Sr. 
  2. 137Cs. 
  3. 3H. 
  4. 135Xe. 
  5. 131I.

8. When air is sampled by being pulled through a filter paper, the radioactivity at equilibrium on the filter paper due to naturally occurring radon daughters is:

  1. proportional to the flow rate of the sampler. 
  2. dependent only on the total volume of air sampled. 
  3. dependent on the period of time required for radioactive equilibrium on the filter paper to be established. 
  4. dependent on the volume of air sampled after radioactive equilibrium on the filter paper has been established. 
  5. independent of the flow rate of the sampler.

9. The biologically most significant type of interaction of thermal neutrons with atoms in tissue is:

  1. ionization. 
  2. elastic scattering. 
  3. inelastic scattering. 
  4. hydrolization. 
  5. capture.

10. All of the following are common causes of significant radiation exposure in the use of x-ray diffraction equipment except:

  1. alteration or removal of shielding in order to perform a specialized analysis. 
  2. visual alignment of the beam without using a leaded glass shield. 
  3. placement of fingers in the primary beam while changing samples. 
  4. failure to incorporate shielding in the walls of the room in which the unit is housed. 
  5. failure to realize that x-ray beams are emitted from exit ports other than the one of immediate concern.

11. To avoid criticality when processing waste fissionable material, the size and shape of the container and the concentration are most important for:

  1. a liquid slurry. 
  2. small, dry solid pieces. 
  3. dry powder. 
  4. large solid pieces. 
  5. an alloy of less dense metals.

12. A solution contaminated with plutonium has spilled on the ground near a facility. There are no other radioactive materials in the solution. Which one of the following is the most appropriate primary survey instrument to assess the extent of the contamination?

  1. Portable thin NaI(Tl) scintillator (FIDLER). 
  2. Portable high purity Ge spectrometer. 
  3. End-window GM survey meter. 
  4. Air-proportional alpha survey meter. 
  5. Gas-proportional alpha survey meter.

13. A certain radioisotope has a biological half-life in the human body which is three times as long as its radiological half-life. What is the effective half-life?

  1. three-fourths of its radiological half-life. 
  2. four-thirds of its radiological half-life. 
  3. four times its radiological half-life. 
  4. one-third of its biological half-life. 
  5. its biological half-life.

14. When uranium hexafluoride is released to the atmosphere, hydrolysis results in the production of hydrofluoric acid and uranyl fluoride. The primary health hazard associated with such a release is:

  1. chemical toxicity of uranium. 
  2. radiotoxicity of uranium. 
  3. chemical toxicity of UF6. 
  4. chemical toxicity of HF. 
  5. chemical toxicity of F2.

15. In branching decay, a substance may decay by two or more modes. If there were only two modes of decay, the formula for the half-life would be:

  1. T1/2 = (λ1 + λ2)/ln
  2. T1/2 = (T1/2)1 + (T1/2)2 
  3. T1/2 = 1/ λ 1 + 1/ λ 2 
  4. T1/2 = ln2/ λ 1 + ln2/ λ 2 
  5. T1/2 = ln2/( λ 1 + λ 2)

16. An investigator has received some 95Zr (half-life = 65 days) for use in a long-term study. He finds the zirconium to be contaminated with 60Co (half-life = 5.24 years) such that the ratio of 60Co activity to the 95Zr activity is 0.012. After the initial assay, the activities of the two emitters will become equal in:

  1. 280 days. 
  2. 290 days. 
  3. 340 days. 
  4. 360 days. 
  5. 430 days.

17. The count rate for an effluent particulate filter is measured in a proportional counter. Which of the following system calibration parameters is most crucial in converting the result to an activity for use in airborne concentration assessment?

  1. FWHM resolution. 
  2. Fano factor. 
  3. Absolute efficiency. 
  4. Intrinsic efficiency. 
  5. Signal-to-noise ratio.

18. For a narrow beam of photons, the relaxation length is that thickness of absorber that will reduce the photon intensity to ­­­­__________ of its original intensity.

  1. 1/10. 
  2. 1/2. 
  3. 1/log 2. 
  4. 1/ln 2. 
  5. 1/e.

19. In a satisfactory "air-walled" ionization chamber the ionization per cubic centimeter would be:

  1. inversely proportional to the density of the gas in the chamber. 
  2. inversely proportional to the gamma-ray energy absorbed per cubic centimeter of wall material. 
  3. independent of the volume of the chamber. 
  4. independent of the density of the gas in the chamber. 
  5. directly proportional to the linear stopping power of the walls for electrons.

20. An ionization chamber was exposed to 10-2 C kg-1 of x-rays at a rate of 10-4 C kg-1 s-1. The same chamber was then exposed to 10-2 C kg-1 at the rate of 10-2 C kg-1 s-1. If the second exposure reading was less than the first reading, the most likely cause is:

  1. recombination. 
  2. leakage. 
  3. resolving time. 
  4. a decrease of energy absorption. 
  5. an increase in absorption coefficients.

21. Which diagram of atmospheric conditions would result in lofting following release from the indicated stack? Note: Dashed lines represents the adiabatic lapse rate and the solid line represents current conditions.


22. An air sample is counted for 10,000 counts. What is the relative probable error in percent?

  1. 0.1 
  2. 1 
  3. 10 
  4. 100 
  5. 1,000

23. A school district draws its drinking water from an aquifer that contains quantities of Ra-226 requiring pre-treatment. The water is passed through an ion-exchange resin prior to distribution. Which of the following best defines the Ra-226 loaded resin?

  1. Source Material 
  2. UNORM 
  3. NORM 
  4. TENORM 
  5. Byproduct Material

24. The figure shows five traces labeled A through E for a fixed filter Constant Air Monitor. Each represents a physically possible combination of a fixed or varying concentration of a single nuclide collected on the filter, with negligible self-absorption. The CAM trace starts at a background level, increases as the airborne activity is collected, and then continues after all activity in the sampled air is gone.


Which trace most likely represents a nuclide with a half-life of about 20 minutes?

  1. Curve A. 
  2. Curve B. 
  3. Curve C. 
  4. Curve D. 
  5. Curve E.

25. What is the appropriate location for a declared pregnant fluoroscopist to wear an assigned fetal badge?

  1. Over the lead apron at the collar 
  2. Under the lead apron at the chest 
  3. Over the lead apron on the upper left arm 
  4. Under the lead apron at the abdomen 
  5. Declared pregnant workers are restricted from performing fluoroscopy and would not be issued a fetal badge.

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