Nuclear Gauge testing UPDATED ACTUAL
Exam Questions and CORRECT Answers
How do nuclear gauges work? Why does so much care need to be taken when using them? -
CORRECT ANSWER - Nuclear gauges use the interaction of radiation with matter to
measure the density and moisture of material. Radiation sources within each gauge transmit
radiation through the test material. Detectors contained in the gauge measure the radiation that is
scattered by the test material or that passes through it. By calculating the percentage of radiation
that reaches the detectors, the gauge can determine the density or moisture content of test
material.
Introduction to Nuclear Gauge Sources - CORRECT ANSWER - -radioactive source within
the gauge is what makes the gauge work
-source rod extends through the base of the gauge into a predrilled hole up to 12 in.
-Gamma rays are transmitted from the density source->through the test material->counted by
detectors located within the gauge. Average density between the source and detectors is
determined.
-radioactive source itself is smaller than even a penny
-Americium, Californium, and Cobalt allow us to measure density and moisture using a nuclear
gauge.
Elements - CORRECT ANSWER - -The smallest particles of matter are called atoms. All
substances are made up of a limited number of different kinds of atoms
-The radioactive sources in nuclear gauges are made up of elements too. These elements include:
Cesium, Americium, Californium, and Cobalt.
nucleus - CORRECT ANSWER - contsists of both neutrons and protons. The bulk of the
atomic mass is within the nucleus
Electrons - CORRECT ANSWER - negatively charged particles that orbit the nucleus. the
Neg charge of the electrons balances the positive charge of the protons but add very little mass to
the atom.
,Neutron - CORRECT ANSWER - neutral partlces that cluster with protons in nucleus.
Provide mass and act as a "nuclear glue".
Proton - CORRECT ANSWER - positively charged partilces that cluster with neutrons to
make up the nucleus.
Isotope - CORRECT ANSWER - -Atoms of the same element that have different numbers of
neutrons
-The radioactive sources in nuclear gauges are made up of elements too. These elements include:
Cesium, Americium, Californium, and Cobalt.
-Atomic # doesn't change
-Atomic mass changes
-An isotope is identified by writing the chemical symbol with a subscript to the left giving the
atomic number and a superscript giving the atomic mass number.
-Some isotopes are stable, like Carbon 12. Other isotopes are unstable or radioactive, like Carbon
14.
-For an isotope to be stable, the neutron/proton ratio must lie within a relatively narrow range.
For example, Carbon-12 has 6 neutrons and 6 protons in the nucleus , making it a stable isotope.
-As the number of neutrons increases relative to the number of protons, an isotope is more likely
to be unstable or radioactive. Carbon 14, which has 8 neutrons and 6 protons in the nucleus, is
unstable because the ratio of neutrons to protons is too high. This form of Carbon has a familiar
use: Carbon -14 dating of old organic materials.
Radioactivity - CORRECT ANSWER - -the property of certain isotopes to undergo
spontaneous decay which transforms the nucleus to achieve stability.
- When an atom decays the nucleus undergoes changes which alter the ratio of neutrons and
protons and result in the emission of radiation
Radiation - CORRECT ANSWER - emitted during the decay of radioactive material in the
form of subatomic particles and/or electromagnetic radiation.
,Particle radiation - CORRECT ANSWER - consists of high speed subatomic particles which
have mass and energy. Apha, beta, and neutron are types of particle radiation.
electromagnetic radiation - CORRECT ANSWER - consists of bundles of pure energy, called
photons, which have no mass. Gamma rays are a type of elemctromagnetic radiation.
Alpha radiation - CORRECT ANSWER - -Alpha particles consist of two protons and two
neutrons, or the nucleus of a Helium atom.
-Alpha particles result from the decay of heavy nuclei with more than 82 protons. Because of
their large mass (atomic weight of 4) and strong electrical charge (+2 from the two protons),
alpha particles travel only a short distance in matter before losing their energy and coming to a
stop.
-Within the nuclear gauge, the encapsulation of the radioactive material stops all alpha radiation
alpha particle penetration - CORRECT ANSWER - -These particles are virtually harmless as
an external source of radiation, because they lose energy quickly as they travel a short distance in
biologic matter (superficial layer of skin).
-With internal sources the reverse is true, if emitted internally they can be very damaging to
tissue.
-can be stopped by a single sheet of ordinary paper
Beta radiation - CORRECT ANSWER - -Beta radiation is a high-energy electron ejected from
the nucleus of an atom as a neutron breaks down into the electron and a proton. The beta particle
has a tiny mass and an electrical charge of -1. Beta particles travel only a short distance in solids
before they are absorbed.
-While alpha particle penetration is stopped by a single sheet of paper, a 1/16 inch thick sheet of
aluminum will stop most beta particles.
beta penetration - CORRECT ANSWER - Within the nuclear gauge, the encapsulation of the
radioactive material prevents alpha and beta radiation from escaping and being a hazard.
Gamma Radiatio - CORRECT ANSWER - -Gamma rays are a form of electromagnetic
radiation, much like x-rays, radio waves, and visible light.
, -Gamma rays have no mass, no electrical charge, and travel at the speed of light.
-Gamma rays, however, are much more energetic and penetrating than visible light.
-While alpha particles are stopped by a single sheet of paper, and a 1/16 inch thick sheet of
aluminum stops beta particles, it takes several inches of lead to stop most gamma rays.
Gamma penetration - CORRECT ANSWER - -Strong- absorbed by lead
-Gamma radiation is the most hazardous form of radiation found in a nuclear gauge. 2" of lead
will stop 99% of Cs137 gamma radiation.
Neutron radiation - CORRECT ANSWER - -unlike alphas and betas, neutrons have no
electrical charge.
-Since they have no electrical charge, neutrons are neither repulsed by nor attracted to other
charged objects. They interact with matter through direct, physical collision.
-To be detected, neutrons must be thermalized, or slowed down first. The primary means of
thermalization is an interaction with hydrogen atoms. Once neutrons are slowed, they can be
detected by a helium-3 detector located in the gauge.
Neutron Penetration - CORRECT ANSWER - -very high
-stopped at concrete.
cross section - CORRECT ANSWER - the probability of a neutron interacting with an
element
neutron particle penetration - CORRECT ANSWER - neutrons are electrically neutral, they
are very penetrating and basically unaffected by heavier elements such as lead.
-neutrons interact with light weiht elements such as hydrogen.
-water serves best as a neutron shield because it has lots of H.
thermalization - CORRECT ANSWER - neutrons have been slowed down to the speed of an
air molecule, about 1.25mps.
-any material containing large amounts of H is a good neutron thermalizer.
Exam Questions and CORRECT Answers
How do nuclear gauges work? Why does so much care need to be taken when using them? -
CORRECT ANSWER - Nuclear gauges use the interaction of radiation with matter to
measure the density and moisture of material. Radiation sources within each gauge transmit
radiation through the test material. Detectors contained in the gauge measure the radiation that is
scattered by the test material or that passes through it. By calculating the percentage of radiation
that reaches the detectors, the gauge can determine the density or moisture content of test
material.
Introduction to Nuclear Gauge Sources - CORRECT ANSWER - -radioactive source within
the gauge is what makes the gauge work
-source rod extends through the base of the gauge into a predrilled hole up to 12 in.
-Gamma rays are transmitted from the density source->through the test material->counted by
detectors located within the gauge. Average density between the source and detectors is
determined.
-radioactive source itself is smaller than even a penny
-Americium, Californium, and Cobalt allow us to measure density and moisture using a nuclear
gauge.
Elements - CORRECT ANSWER - -The smallest particles of matter are called atoms. All
substances are made up of a limited number of different kinds of atoms
-The radioactive sources in nuclear gauges are made up of elements too. These elements include:
Cesium, Americium, Californium, and Cobalt.
nucleus - CORRECT ANSWER - contsists of both neutrons and protons. The bulk of the
atomic mass is within the nucleus
Electrons - CORRECT ANSWER - negatively charged particles that orbit the nucleus. the
Neg charge of the electrons balances the positive charge of the protons but add very little mass to
the atom.
,Neutron - CORRECT ANSWER - neutral partlces that cluster with protons in nucleus.
Provide mass and act as a "nuclear glue".
Proton - CORRECT ANSWER - positively charged partilces that cluster with neutrons to
make up the nucleus.
Isotope - CORRECT ANSWER - -Atoms of the same element that have different numbers of
neutrons
-The radioactive sources in nuclear gauges are made up of elements too. These elements include:
Cesium, Americium, Californium, and Cobalt.
-Atomic # doesn't change
-Atomic mass changes
-An isotope is identified by writing the chemical symbol with a subscript to the left giving the
atomic number and a superscript giving the atomic mass number.
-Some isotopes are stable, like Carbon 12. Other isotopes are unstable or radioactive, like Carbon
14.
-For an isotope to be stable, the neutron/proton ratio must lie within a relatively narrow range.
For example, Carbon-12 has 6 neutrons and 6 protons in the nucleus , making it a stable isotope.
-As the number of neutrons increases relative to the number of protons, an isotope is more likely
to be unstable or radioactive. Carbon 14, which has 8 neutrons and 6 protons in the nucleus, is
unstable because the ratio of neutrons to protons is too high. This form of Carbon has a familiar
use: Carbon -14 dating of old organic materials.
Radioactivity - CORRECT ANSWER - -the property of certain isotopes to undergo
spontaneous decay which transforms the nucleus to achieve stability.
- When an atom decays the nucleus undergoes changes which alter the ratio of neutrons and
protons and result in the emission of radiation
Radiation - CORRECT ANSWER - emitted during the decay of radioactive material in the
form of subatomic particles and/or electromagnetic radiation.
,Particle radiation - CORRECT ANSWER - consists of high speed subatomic particles which
have mass and energy. Apha, beta, and neutron are types of particle radiation.
electromagnetic radiation - CORRECT ANSWER - consists of bundles of pure energy, called
photons, which have no mass. Gamma rays are a type of elemctromagnetic radiation.
Alpha radiation - CORRECT ANSWER - -Alpha particles consist of two protons and two
neutrons, or the nucleus of a Helium atom.
-Alpha particles result from the decay of heavy nuclei with more than 82 protons. Because of
their large mass (atomic weight of 4) and strong electrical charge (+2 from the two protons),
alpha particles travel only a short distance in matter before losing their energy and coming to a
stop.
-Within the nuclear gauge, the encapsulation of the radioactive material stops all alpha radiation
alpha particle penetration - CORRECT ANSWER - -These particles are virtually harmless as
an external source of radiation, because they lose energy quickly as they travel a short distance in
biologic matter (superficial layer of skin).
-With internal sources the reverse is true, if emitted internally they can be very damaging to
tissue.
-can be stopped by a single sheet of ordinary paper
Beta radiation - CORRECT ANSWER - -Beta radiation is a high-energy electron ejected from
the nucleus of an atom as a neutron breaks down into the electron and a proton. The beta particle
has a tiny mass and an electrical charge of -1. Beta particles travel only a short distance in solids
before they are absorbed.
-While alpha particle penetration is stopped by a single sheet of paper, a 1/16 inch thick sheet of
aluminum will stop most beta particles.
beta penetration - CORRECT ANSWER - Within the nuclear gauge, the encapsulation of the
radioactive material prevents alpha and beta radiation from escaping and being a hazard.
Gamma Radiatio - CORRECT ANSWER - -Gamma rays are a form of electromagnetic
radiation, much like x-rays, radio waves, and visible light.
, -Gamma rays have no mass, no electrical charge, and travel at the speed of light.
-Gamma rays, however, are much more energetic and penetrating than visible light.
-While alpha particles are stopped by a single sheet of paper, and a 1/16 inch thick sheet of
aluminum stops beta particles, it takes several inches of lead to stop most gamma rays.
Gamma penetration - CORRECT ANSWER - -Strong- absorbed by lead
-Gamma radiation is the most hazardous form of radiation found in a nuclear gauge. 2" of lead
will stop 99% of Cs137 gamma radiation.
Neutron radiation - CORRECT ANSWER - -unlike alphas and betas, neutrons have no
electrical charge.
-Since they have no electrical charge, neutrons are neither repulsed by nor attracted to other
charged objects. They interact with matter through direct, physical collision.
-To be detected, neutrons must be thermalized, or slowed down first. The primary means of
thermalization is an interaction with hydrogen atoms. Once neutrons are slowed, they can be
detected by a helium-3 detector located in the gauge.
Neutron Penetration - CORRECT ANSWER - -very high
-stopped at concrete.
cross section - CORRECT ANSWER - the probability of a neutron interacting with an
element
neutron particle penetration - CORRECT ANSWER - neutrons are electrically neutral, they
are very penetrating and basically unaffected by heavier elements such as lead.
-neutrons interact with light weiht elements such as hydrogen.
-water serves best as a neutron shield because it has lots of H.
thermalization - CORRECT ANSWER - neutrons have been slowed down to the speed of an
air molecule, about 1.25mps.
-any material containing large amounts of H is a good neutron thermalizer.
