Health Physics Part I - Typical Questions

1. The roentgen is equal to:

1.0 coulomb/kg.
 1.00 × 10^-3 coulomb/kg
 5.28 × 10^-3 coulomb/kg
 2.58 × 10^-4 coulomb/kg
 5.28 × 10^-4 coulomb/kg
2. The term solubility or transportability, when applied to the metabolism of radionuclides, refers to the:

metabolic breakdown of a radionuclide-containing compound which allows its incorporation into body tissues.
 solubilization of a radionuclide-containing compound by means of hydration, ion exchange, or esterification reactions.
 translocation dissimilation of a radionuclide-containing compound by means of biological-chemical action.
 property of a radionuclide-containing compound which results in its transfer across body membranes.
 translocation of a radionuclide-containing compound from one point to another under conditions of physiological dysfunction.

3. 9.25 x 10^11 Bq (25 Ci) of a gas, with a half-life = 2.3 h, is uniformly distributed in the air in a 2.5-m x 10-m x 15-m room. The effective room ventilation rate is 150 m^3/h. After 1 hour, the activity concentration in the room is:
7.32 x 10^8 Bq/m^3
 1.10 x 10^9 Bq/m^3
 1.23 x 10^9 Bq/m^3
 1.73 x 10^9 Bq/m^3
 2.47 x 10^9 Bq/m^3

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

alteration or removal of shielding in order to perform a specialized analysis.
 visual alignment of the beam without using a leaded glass shield.
 placement of fingers in the primary beam while changing samples.
 failure to incorporate shielding in the walls of the room in which the unit is housed.
 failure to realize that x-ray beams are emitted from exit ports other than the one of immediate concern.
5. The eyes are most susceptible to exposure to microwave radiation of frequencies around:
150 MHz
 300 MHz
 1,500 MHz
 3,000 MHz
 5,000 MHz
6. An investigator has received some zirconium-95 (half-life = 65 days) for use in a long-term study. He finds the zirconium to be contaminated with cobalt-60 (half-life = 5.24 years) such that the ratio of (µCI Zr-95) is 0.012. After the initial assay, the activities of the two emitters will become equal in:

280 days
 290 days
 340 days
 360 days
 430 days
7. The International Commission on Radiation Units and Measurements has considered it necessary in radiation protection to provide a factor that denotes the modification of the effectiveness of a given absorbed dose by linear energy transfer. This factor is the:
Equivalent Dose
 Relative distribution functions
 Quality Factor
 Relative Biological Effectiveness
 Distribution factor

8. Which one of the following solid-state materials has the most constant response per roentgen over the energy range of 0.01 to 1 MeV when used as a dosimeter without special shields to correct for energy dependence?

Calcium Sulfate (CaSO4:Mn)
 Calcium Flouride (CaF2:MN)
 Lithium drifted Germanium
 Low-Z glass rods
 Lithium Flouride (LiF)
9. The response time of an ionization chamber-type survey meter used to measure an X-ray beam is not influenced by the:
inertia of the meter
 range selector resistance
 circuit capacitance
 RC time constant
 incident X-ray photon energy
10. In a satisfactory "air-walled" ionization chamber the ionization per cubic centimeter would be:
inversely proportional to the density of the gas in the chamber.
 inversely proportional to the gamma ray energy absorbed per cubic centimeter of wall material.
 directly proportional to the stopping power of the walls for electrons.
 independent of the density of the gas in the chamber.
 independent of the volume of the chamber.
11. Bi-205 (half-life = 15.3 days) decays to Pb-205 (half-life = 3 x 10 ^7 years). If a pure sample of Bi-205 has an initial activity of 5 x 10^10 Bq, how much total sample activity will be present after a decay period of 90 days?
1.4 x 10^8 Bq
 8.5 x 10^8 Bq
 1.7 x 10^9 Bq
 4.2 x 10^10 Bq
 5.0 x 10^10 Bq
12. The half-value thickness for 1 MeV photons in lead approximates 1 cm. A 100-millicurie essential mass-less source of zinc-65 (gamma-ray energy = 1.12 MeV) produces a dose rate of 30 milliroentgens/hour at 1 meter without shielding. What would the dose rate be at about 10 cm from this source with the addition of a 5-cm thick lead shield if the build-up factor is 2.1?
0.02 milliroentgens/hour
 0.9 milliroentgens/hour
 2 milliroentgens/hour
 20 milliroentgens/hour
 200 milliroentgens/hour
13. In routine environmental surveillance, certain samples are collected and analyzed for specific reasons. In this regard, which one of the following statements is incorrect?
Foodstuffs are analyzed because they are generally the main route of radionuclide intake by the general population.
 Air and water are analyzed because they are always the most sensitive indicators of environmental releases.
 Mud and silt are analyzed because they are often good indicators of the history of radionuclide wastes in an aquatic environment.
 Aquatic organisms are analyzed because they concentrate certain radionuclides and aid in the assessment of radionuclide contamination.
 Milk and milk products are analyzed because these are generally the major avenue of intake of Strontium-90, particularly among younger population groups.
14. The method most commonly used today for removing noble gases from effluent waste streams from nuclear reactors and chemical processing plants is:
cryogenic distillation.
 chelation with EDTA.
 adsorption on activated charcoal.
 countercurrent ion exchange.
 absorption in freon.
15. Californium-252 fissions spontaneously. When placed in needles, it may be better than radium-226 for radiotherapy of malignant tumors with poorly oxygenated cells because:
gamma radiation has about the same effect on poorly oxygenated cells as on normal cells.
the relative biological effect for fast neutrons is less for poorly oxygenated cells than for normal cells.
 the oxygen enhancement ratio is less for the high LET fast neutron radiation than for low LET gamma radiation.
 fast neutrons are more destructive of poorly oxygenated cells than of normal cells.
 the oxygen enhancement ratio is greater for the high LET fast neutron radiation than for the LET gamma radiation.
16. A worker is exposed to 2340 Bq m^-3 (6.3 x 10^-8 uCi/cm^3) iodine^131 for 4 hours. The MPC (air) for iodine^131 is 333 Bq m^-3 (9.0 x 10^-9 uCi/cm^3). The worker was wearing cotton overalls, rubber boots, rubber gloves, and an air-purifying respirator with particulate combination cartridges. Which one of the following gives the closest number of MPC-h that you would credit the worker with?
0.5 MPC-h
 1 MPC-h
 4 MPC-h
 7 MPC-h
 28 MPC-h
17. 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:
proportional to the flow rate of the sampler.
 dependent only on the total volume of air sampled.
 dependent on the period of time required for radioactive equilibrium on the filter paper to be established.
 dependent on the volume of air sampled after radioactive equilibrium on the filter paper has been established.
 independent of the flow rate of the sampler.
18. Based upon diffusion equations, if gaseous radioactivity is being discharged from a stack and the flow of air through the stack is significantly increased without an increase in the rate of discharge of radioactivity, what will be the observed change in air concentrations downwind of the stack? (Assume no change in effective stack height.)
A significant increase.
 A slight increase.
 None.
 A slight decrease.
 A significant decrease.
19. 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:
2 mrem/hr
 5 mrem/hr
 25 mrem/hr
 50 mrem/hr
 200 mrem/hr
20. To avoid criticality when processing waste fissionable material, the size and shape of the container and the concentration are most important for:
a liquid slurry.
 small, dry solid pieces.
 dry powder.
 large solid pieces.
 an alloy of less dense metals.
21. For a given energy, the greatest radiological hazard from bremsstrahlung would be expected from:
protons
 positrons
 muons
 alphas
 neutrons
22. The USNRC normally requires licensees to leak test sealed sources:
before every use.
 after every use.
 every three months
 every six months.
 once per year.
23. Radionuclide concentrations in uranium mine atmospheres are usually expressed in terms of "working levels." One "working level" is defined as:
any combination of radon daughters in one liter of air that will result in the emission of 1.3 x 10^5 MeV of alpha energy.
 the total alpha energy released through decay of 100 picocuries per liter of Rn-222 in equilibrium with its progeny.
 that concentration of Rn-222 which, when in equilibrium with its progeny, will result in the release of 4.8 x 10^4 MeV of total beta energy per liter per minute.
 that concentration of Rn-222 which, when in equilibrium with its progeny, will result in no single radionuclide being above its DAC for air.
that concentration of Rn-222 which, when in equilibrium with its progeny, will be such that the sum of the fractional DAC's does not exceed unity.
24. The maximum concentration of a radionuclide aerosol at ground level downwind from stack is proportional to the:
emission rate of the aerosol in the stack gas.
 concentration of the aerosol in the stack gas.
 inverse of the square root of the stack height.
 emission rate of the stack air.
 inverse of the square root of the wind velocity.
25. The exposure rate at the open beam port of an X-ray diffraction unit could be expected to be:
1 to 10 mr/minute
 100 mr/minute to 1 R/minute
 10 to 100 R/minute
 100 to 1,000 R/minute
 10,000 to 100,000 R/minute
26. An ionization chamber was exposed to 2.58 x 10^-2 C kg^-1 (100 R) of x-radiation at the rate of 4.30 x 10^-4 C kg^-1 s^-1 (100 R minute^-1). The same chamber was then exposed to 2.58 x 10^-2 C kg^-1 (100 R) at the rate of 2.15 x 10^-2 C kg^-1 s^-1 (500 R minute^-1). If the second reading of the ionization chamber was less than the first reading, the most likely cause is:
recombination
 leakage
 resolving time
 a decrease of energy absorption
 an increase in absorption coefficients
27. The report from a passive personnel monitoring dosimeter (badge) is 1 mSv (100 mrem) deep dose (photon), 1 mSv (100 mrem) deep dose (fast neutron) and 100 mSv (10,000 mrem) additional shallow dose (beta). Following ICRP-60 guidance, the approximate effective dose would be:
2 mSv (200 mrem)
 3 mSv (300 mrem)
 12 mSv (1,200 mrem)
 21 mSv (2,100 mrem)
 102 mSv (10,200 mrem)
28. The NCRP Report 106 recommends a limit of 75 microcurie-hours (2.775 x 10^6 Bq-hours) for beta "hot particle" exposures to the skin. This limit is based on:
a ten-fold increase in the risk of radiation-induced skin cancer
 early radiographers'/radiologists' experiences with "skin erythema dose"
 the limit on effective dose and the ICRP weighting factor for skin
 the avoidance of ulceration to even minute areas of the skin
 extrapolation from the threshold for incidence of ultraviolet burns
29. The figure below shows five traces labeled A through E for a fixed filter Constant Air Monitor (CAM). Each represents fixed or varying concentrations 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 long-lived nuclide present in the air at a fixed concentration?
Curve A
 Curve B
 Curve C
 Curve D
 Curve E
 

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