RPT 113EXAM 3Page 1

NAME: ______July 15, 2008

  1. The typical fixed air sampler system in a nuclear facility (or stack monitor) collects or monitors three forms of radioactive air samples. Name the three. (12 pts)
  1. For two of the above air sample types, two have specific “media” for collecting samples (media can be removed and taken to the lab for analysis). Name those two media types and match which air sample forms from question 1 they are used for. (8 pts)
  1. How would the intrinsic efficiency of a scintillation detector change for high energy photons, as the scintillation material density is increased? (5 pts)
  2. The intrinsic efficiency of the detector would increase.
  3. The intrinsic efficiency of the detector would decrease.
  4. The intrinsic efficiency of the detector would not change.
  5. The intrinsic efficiency for low energy photons is zero.
  1. You have started a low-volume air sampler operating in an outdoor work area to collect an air sample for gross airborne activity. You set the flow rate of the sampler at 20 liters per minute (lpm) and plan to operate the sampler during the dayshift for 8 hours. During the sample collection time, construction activities took place nearby creating a lot of dust that blew into your work area. How will the dust change the air sample volume and why? (5 pts)
  2. Increases the volume because dust is heavier than air
  3. Decreases the volume because the dust will clog the sample filter
  4. Does not change the volume because the sampler has a fixed flow rate
  5. Does not change the volume because the sampler uses a positive displacement pump
  1. In the system below, what is the most common crystal used for gamma ray detection? (5 pts)


  1. In the system above, what is the pinkish component, from the photocathode to the output? (5 pts)
  1. Why does a scintillation detector not operate within one of the three operating regions (Ionization, Proportional, Geiger) of the gas amplification curve? (5 pts)
  2. It utilizes a vacuum for detection
  3. It operates at a higher voltage
  4. It operates at a lower voltage
  5. It utilizes a solid detector
  1. The right kind of scintillator can be used to distinguish between alpha and beta radiation. How is that done? (5 pts)
  2. A removable beta shield
  3. Alpha radiation produces larger signals
  4. Beta radiation produces larger signals
  5. A removable alpha shield
  1. You’re working in a lab that reuses liquid scintillation vials by washing them with very hot water and steam. If one vial didn’t really come clean and had some residual radioactivity left in it, when it was used again, what would be the result? (5 pts)
  2. Counts would be lower than actual
  3. Counts would be higher than actual
  4. There would be no change in the counts
  5. It would depend on the type of cocktail used.
  1. What is the primary reason you would choose a liquid scintillation counter for an analysis over a Geiger counter? (6 pts)
  1. T / F LSC cannot be used to distinguish between higher and lower energy beta radiation. (5 pts)
  1. You are assigned to retrieve REMP air samples from the field around your plant. Why do you need to be quick about processing and getting the air samples ready for analysis? (5 pts)
  1. LSC is used to analyze water samples for one radionuclide that is almost undetectable by other means. What is the radionuclide? (5 pts) And what radiological property makes it so hard to detect? (5 pts)
  1. If you moved a sample from one location to a new location twice as far from the detector, the count rate will go up or down (state which) and by what factor? (6 pts)
  1. Recordkeeping is important in a REMP program. When you have to collect samples, you have to record some data. Name three items that you would record for each sample collected. (8 pts)
  1. You’ve taken an air sample and analyzed two different media types that were part of the air sampling equipment. One media type yielded a gross airborne contamination level of 0.03 μCi. The other media type indicated 0.02 μCi. What is the correct answer below? (5 pts)
  2. Airborne contamination is averaged to 0.025 μCi
  3. Airborne contamination is totaled to 0.05 μCi
  4. Airborne contamination is 0.03 μCi because you always take the higher value
  5. Airborne contamination is 0.01 μCi because you subtract one value as background