NRRPT PREP DETECTION AND MEASUREMENT STUDY
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Question Number: 399 Detection and Measurement
In NTE (nuclear track emulsion) film, the tracks are caused by:
A) alpha particles.
B) beta particles.
C) gamma photons.
D) recoil neutrons.
E) recoil protons. Answer: The correct answer is: E
In this fast neutron responsive dosimeter, recoil protons from elastic scattering with hydrogen
atoms in the film create short "tracks" of ionization as stable silver atoms are created. These
tracks are counted either by eye or mechanically and equated to total neutron dose equivalent.
Question Number: 400 Detection and Measurement
The sensitivity of photographic film to photons is energy dependent primarily because of:
A) varying conditions of temperature and humidity during exposure.
B) strong photoelectric absorption by the silver bromide in the emulsion.
C) varying energies of the Compton-scattered photons.
D) pair production.
E) build-up. Answer: The correct answer is: B
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,Film is considered to be "energy dependent" since it is most efficient for photon detection when
interaction is by photoelectric effect. As we know, photoelectric effect predominates only below
200 keV. This is one reason that filters are used in film badges.
Question Number: 401 Detection and Measurement
What is the effective half-life in the human body for Cobalt-60, if the biological half-life is eight
days?
A) 0.125 days
B) 1.52 days
C) 7.97 days
D) 45.8 days
E) 1.52 years Answer: The correct answer is: C
A good thumb rule for calculating effective half-life is that if the isotope has a half-life greater
than 100 days, the effective half-life (Teff) is only a bit less than the biological half-life. The
effective half-life is never greater than the biological half-life. The equation to calculate Teff is as
follows:
Teff = Tb * Tr / Tb + Tr Where:
Tb = biological half-life
Tr = radiological (physical) half-life
Question Number: 402 Detection and Measurement
If the DAC for Rn-222 is 3.0 x 10 -8 µCi /ml, the working level is: A) 9.0 x 10-8 µCi /ml
B) 9.0 x 10-9 µCi /ml
C) 3.0 x 10-9 µCi /ml
D) 6.0 x 10-7 µCi /ml
E) 6.0 x 10-8 µCi /ml Answer: The correct answer is: A
According to 10 CFR Part 20 Appendix B, the DAC for Rn-222 is 1/3 of the working level.
Question Number: 403 Detection and Measurement
An individual who receives 40 DAC-hours will receive a committed effective dose equivalent of:
A) 10 millirem
B) 40 millirem
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,C) 80 millirem
D) 100 millirem
E) 1250 millirem Answer: The correct answer is: D
Assuming the DAC is based upon the sALI, one DAC-hour is equal to a CEDE of 2.5 mrem.
Therefore:
40 DAC-hrs * 2.5 mrem/DAC-hr = 100 mrem
Question Number: 404 Detection and Measurement
The full width at half maximum peak energy for a Cesium-137 photopeak using a GeLi detector
is 3 keV. The photopeak energy is 0.662 MeV. The percent resolution of the detection system for
this energy is:
A) 0.22%
B) 0.45%
C) 4.53%
D) 22.0%
E) 45.3% Answer: The correct answer is: B
% resolution = (FWHM/peak energy) * 100%
= (3 keV/662 keV) * 100%
= .453 %
Question Number: 405 Detection and Measurement
What is the main advantage of using a proportional counter?
A) It operates in a higher voltage region.
B) It is able to differentiate between different types of radiation.
C) It causes significantly more free electrons.
D) It is less energy dependent than other detectors.
E) It possesses higher sensitivity than other detectors. Answer: The correct answer is: B
In the proportional region, radiations with different specific ionization create pulses of different
heights. By using pulse height discriminators, alpha can be distinguished from beta-gamma
pulses.
Question Number: 406 Detection and Measurement
3
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, What are the constituents of the fill gas P-10?
A) 10% argon and 90% methane
B) 50% argon and 50% methane
C) 90% argon and 10% methane
D) 60% argon and 10% methane
E) 10% argon and 60% methane Answer: The correct answer is: C
P-10 is used in gas-filled detectors in the proportional and G-M regions. The argon serves as the
ionization gas, the methane is an organic quench gas.
Question Number: 407 Detection and Measurement
You are setting up a count room for analysis of airborne and surface contamination samples at a
facility where the isotopes of concern are transuranics, fission products, and activation
products. Your BEST selection of instruments would be:
A) Geiger-Mueller detector with scaler, zinc sulfide scintillation detector.
B) Geiger-Mueller detector with scaler, GeLi detector.
C) gas flow proportional counter, GeLi detector.
D) zinc sulfide scintillation detector, GeLi detector.
E) sodium iodide scintillation detector, gas flow proportional counter. Answer: The correct
answer is: C
Since the isotopes of concern are emitting alpha, beta, and gamma radiations, a proportional
counter will be necessary for its capability to distinguish between alpha and beta-gamma. Since
airborne contamination is being measured, gamma spectroscopy capability (in this case GeLi has
the best resolution) is required to identify radionuclides having different DACs.
Question Number: 408 Detection and Measurement
A meter reads 40,000 net cpm and the efficiency of the detector is 40%. How many dpm does
this represent? A) 10,000 dpm
B) 16,000 dpm
C) 10,000 dpm
D) 100,000 dpm
E) 1,000,000 dpm Answer: The correct answer is: D
4
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GUIDE EXAM LATEST 2026/2027 UPDATED VERIFIED
QUESTIONS AND SOLUTIONS A+ PASS
GUARANTEED|COMPLETE STUDY GUIDE WITH 100%
ACCURATE QUESTIONS &ANSWERS. EXCELLENCE
GUARANTEED.
Question Number: 399 Detection and Measurement
In NTE (nuclear track emulsion) film, the tracks are caused by:
A) alpha particles.
B) beta particles.
C) gamma photons.
D) recoil neutrons.
E) recoil protons. Answer: The correct answer is: E
In this fast neutron responsive dosimeter, recoil protons from elastic scattering with hydrogen
atoms in the film create short "tracks" of ionization as stable silver atoms are created. These
tracks are counted either by eye or mechanically and equated to total neutron dose equivalent.
Question Number: 400 Detection and Measurement
The sensitivity of photographic film to photons is energy dependent primarily because of:
A) varying conditions of temperature and humidity during exposure.
B) strong photoelectric absorption by the silver bromide in the emulsion.
C) varying energies of the Compton-scattered photons.
D) pair production.
E) build-up. Answer: The correct answer is: B
1
APPHIA - Crafted with Care and Precision for Academic Excellence.
,Film is considered to be "energy dependent" since it is most efficient for photon detection when
interaction is by photoelectric effect. As we know, photoelectric effect predominates only below
200 keV. This is one reason that filters are used in film badges.
Question Number: 401 Detection and Measurement
What is the effective half-life in the human body for Cobalt-60, if the biological half-life is eight
days?
A) 0.125 days
B) 1.52 days
C) 7.97 days
D) 45.8 days
E) 1.52 years Answer: The correct answer is: C
A good thumb rule for calculating effective half-life is that if the isotope has a half-life greater
than 100 days, the effective half-life (Teff) is only a bit less than the biological half-life. The
effective half-life is never greater than the biological half-life. The equation to calculate Teff is as
follows:
Teff = Tb * Tr / Tb + Tr Where:
Tb = biological half-life
Tr = radiological (physical) half-life
Question Number: 402 Detection and Measurement
If the DAC for Rn-222 is 3.0 x 10 -8 µCi /ml, the working level is: A) 9.0 x 10-8 µCi /ml
B) 9.0 x 10-9 µCi /ml
C) 3.0 x 10-9 µCi /ml
D) 6.0 x 10-7 µCi /ml
E) 6.0 x 10-8 µCi /ml Answer: The correct answer is: A
According to 10 CFR Part 20 Appendix B, the DAC for Rn-222 is 1/3 of the working level.
Question Number: 403 Detection and Measurement
An individual who receives 40 DAC-hours will receive a committed effective dose equivalent of:
A) 10 millirem
B) 40 millirem
2
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,C) 80 millirem
D) 100 millirem
E) 1250 millirem Answer: The correct answer is: D
Assuming the DAC is based upon the sALI, one DAC-hour is equal to a CEDE of 2.5 mrem.
Therefore:
40 DAC-hrs * 2.5 mrem/DAC-hr = 100 mrem
Question Number: 404 Detection and Measurement
The full width at half maximum peak energy for a Cesium-137 photopeak using a GeLi detector
is 3 keV. The photopeak energy is 0.662 MeV. The percent resolution of the detection system for
this energy is:
A) 0.22%
B) 0.45%
C) 4.53%
D) 22.0%
E) 45.3% Answer: The correct answer is: B
% resolution = (FWHM/peak energy) * 100%
= (3 keV/662 keV) * 100%
= .453 %
Question Number: 405 Detection and Measurement
What is the main advantage of using a proportional counter?
A) It operates in a higher voltage region.
B) It is able to differentiate between different types of radiation.
C) It causes significantly more free electrons.
D) It is less energy dependent than other detectors.
E) It possesses higher sensitivity than other detectors. Answer: The correct answer is: B
In the proportional region, radiations with different specific ionization create pulses of different
heights. By using pulse height discriminators, alpha can be distinguished from beta-gamma
pulses.
Question Number: 406 Detection and Measurement
3
APPHIA - Crafted with Care and Precision for Academic Excellence.
, What are the constituents of the fill gas P-10?
A) 10% argon and 90% methane
B) 50% argon and 50% methane
C) 90% argon and 10% methane
D) 60% argon and 10% methane
E) 10% argon and 60% methane Answer: The correct answer is: C
P-10 is used in gas-filled detectors in the proportional and G-M regions. The argon serves as the
ionization gas, the methane is an organic quench gas.
Question Number: 407 Detection and Measurement
You are setting up a count room for analysis of airborne and surface contamination samples at a
facility where the isotopes of concern are transuranics, fission products, and activation
products. Your BEST selection of instruments would be:
A) Geiger-Mueller detector with scaler, zinc sulfide scintillation detector.
B) Geiger-Mueller detector with scaler, GeLi detector.
C) gas flow proportional counter, GeLi detector.
D) zinc sulfide scintillation detector, GeLi detector.
E) sodium iodide scintillation detector, gas flow proportional counter. Answer: The correct
answer is: C
Since the isotopes of concern are emitting alpha, beta, and gamma radiations, a proportional
counter will be necessary for its capability to distinguish between alpha and beta-gamma. Since
airborne contamination is being measured, gamma spectroscopy capability (in this case GeLi has
the best resolution) is required to identify radionuclides having different DACs.
Question Number: 408 Detection and Measurement
A meter reads 40,000 net cpm and the efficiency of the detector is 40%. How many dpm does
this represent? A) 10,000 dpm
B) 16,000 dpm
C) 10,000 dpm
D) 100,000 dpm
E) 1,000,000 dpm Answer: The correct answer is: D
4
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