AMMO-66 Module 04: Radiation Safety Exam
U.S. Army/DOD Radiation Safety Course
2026/2027 Certification Cycle | Military Radiation Safety Certification
Exam Structure
The AMMO-66 Module 04 Radiation Safety Exam for the 2026/2027 certification cycle is a 50-
question, multiple-choice examination covering all core radiation safety domains.
Introduction
This comprehensive study guide prepares military personnel and civilian employees for certification
in the safe handling and management of radioactive materials. The content focuses on understanding
radiation hazards, applying strict safety protocols to minimize exposure, using monitoring equipment
correctly, and complying with Department of Defense and federal regulations governing radiation
safety programs.
Answer Format
All correct answers and safety procedures are presented in bold and green, followed by detailed
rationales that reference key regulations (10 CFR, AR 385-40), explain radiation physics principles,
calculate dose relationships, and justify specific protective actions in accordance with ALARA (As Low
As Reasonably Achievable) philosophy.
DOMAIN 1: PRINCIPLES OF IONIZING RADIATION
Question 1
Ionizing radiation is defined as electromagnetic or particulate radiation that has
sufficient energy to remove electrons from atoms or molecules, creating ions. Which of
the following is NOT a type of ionizing radiation?
A) Alpha particles
,B) Beta particles
C) Visible light
D) Gamma rays
C) Visible light
Visible light is non-ionizing radiation because its photon energy (approximately 2-3 eV) is below the
ionization threshold (typically 10-20 eV). Alpha particles, beta particles, and gamma rays all
possess sufficient energy to ionize atoms. According to 10 CFR Part 20, ionizing radiation includes
all forms of radiation that can produce ionization in matter, excluding visible light and other non-
ionizing forms.
Question 2
An alpha particle consists of:
A) A single proton
B) A single neutron
C) A helium-4 nucleus (2 protons and 2 neutrons)
D) An electron
C) A helium-4 nucleus (2 protons and 2 neutrons)
An alpha particle is a helium-4 nucleus consisting of 2 protons and 2 neutrons. Alpha particles are
emitted during alpha decay of heavy radioactive elements. Due to their large mass and positive
charge, alpha particles have a short range in air (a few centimeters) and cannot penetrate the outer
layer of human skin, but they are highly hazardous if inhaled or ingested, as stated in AR 385-40
(Army Safety Program).
Question 3
The half-life of a radioactive isotope is defined as:
A) The time required for all atoms to decay
B) The time required for half of the original number of atoms to decay
C) The time required for the radiation to reach background levels
D) The time required for the material to become non-radioactive
B) The time required for half of the original number of atoms to decay
Half-life is a fundamental concept in nuclear physics. It is the time required for a radioactive sample
to decay to half its original activity. This is independent of the initial amount and is a characteristic
property of each radioactive isotope. For example, Cobalt-60 has a half-life of 5.27 years, meaning
, after 5.27 years, half of the original Co-60 atoms will have decayed. Understanding half-life is
critical for calculating residual radiation levels and determining safe storage times, as required by
10 CFR Part 20.
Question 4
Which type of radiation has the greatest penetrating power and requires lead or
concrete shielding for protection?
A) Alpha particles
B) Beta particles
C) Gamma rays
D) Neutrons
C) Gamma rays
Gamma rays are high-energy photons with very high penetrating power. They can pass through
several centimeters of lead or several feet of concrete. Alpha particles can be stopped by paper, and
beta particles can be stopped by a few millimeters of aluminum. Gamma rays require dense
shielding materials like lead (minimum 5 cm) or concrete (minimum 30 cm) for adequate protection.
This is a critical principle in the ALARA (As Low As Reasonably Achievable) approach to radiation
protection, as specified in 10 CFR 20.1201.
Question 5
The energy of gamma radiation is measured in:
A) Roentgens (R)
B) Rads (Radiation Absorbed Dose)
C) Electron volts (eV) or Million electron volts (MeV)
D) Curies (Ci)
C) Electron volts (eV) or Million electron volts (MeV)
Gamma ray energy is measured in electron volts (eV) or million electron volts (MeV). One electron
volt is the energy gained by an electron when accelerated through a potential difference of one volt.
Roentgens measure ionization in air, rads measure absorbed dose, and curies measure activity
(decay rate). Understanding the distinction between these units is essential for radiation safety
personnel, as outlined in AMMO-66 Module 04 and 10 CFR Part 20.
Question 6
Beta particles are:
U.S. Army/DOD Radiation Safety Course
2026/2027 Certification Cycle | Military Radiation Safety Certification
Exam Structure
The AMMO-66 Module 04 Radiation Safety Exam for the 2026/2027 certification cycle is a 50-
question, multiple-choice examination covering all core radiation safety domains.
Introduction
This comprehensive study guide prepares military personnel and civilian employees for certification
in the safe handling and management of radioactive materials. The content focuses on understanding
radiation hazards, applying strict safety protocols to minimize exposure, using monitoring equipment
correctly, and complying with Department of Defense and federal regulations governing radiation
safety programs.
Answer Format
All correct answers and safety procedures are presented in bold and green, followed by detailed
rationales that reference key regulations (10 CFR, AR 385-40), explain radiation physics principles,
calculate dose relationships, and justify specific protective actions in accordance with ALARA (As Low
As Reasonably Achievable) philosophy.
DOMAIN 1: PRINCIPLES OF IONIZING RADIATION
Question 1
Ionizing radiation is defined as electromagnetic or particulate radiation that has
sufficient energy to remove electrons from atoms or molecules, creating ions. Which of
the following is NOT a type of ionizing radiation?
A) Alpha particles
,B) Beta particles
C) Visible light
D) Gamma rays
C) Visible light
Visible light is non-ionizing radiation because its photon energy (approximately 2-3 eV) is below the
ionization threshold (typically 10-20 eV). Alpha particles, beta particles, and gamma rays all
possess sufficient energy to ionize atoms. According to 10 CFR Part 20, ionizing radiation includes
all forms of radiation that can produce ionization in matter, excluding visible light and other non-
ionizing forms.
Question 2
An alpha particle consists of:
A) A single proton
B) A single neutron
C) A helium-4 nucleus (2 protons and 2 neutrons)
D) An electron
C) A helium-4 nucleus (2 protons and 2 neutrons)
An alpha particle is a helium-4 nucleus consisting of 2 protons and 2 neutrons. Alpha particles are
emitted during alpha decay of heavy radioactive elements. Due to their large mass and positive
charge, alpha particles have a short range in air (a few centimeters) and cannot penetrate the outer
layer of human skin, but they are highly hazardous if inhaled or ingested, as stated in AR 385-40
(Army Safety Program).
Question 3
The half-life of a radioactive isotope is defined as:
A) The time required for all atoms to decay
B) The time required for half of the original number of atoms to decay
C) The time required for the radiation to reach background levels
D) The time required for the material to become non-radioactive
B) The time required for half of the original number of atoms to decay
Half-life is a fundamental concept in nuclear physics. It is the time required for a radioactive sample
to decay to half its original activity. This is independent of the initial amount and is a characteristic
property of each radioactive isotope. For example, Cobalt-60 has a half-life of 5.27 years, meaning
, after 5.27 years, half of the original Co-60 atoms will have decayed. Understanding half-life is
critical for calculating residual radiation levels and determining safe storage times, as required by
10 CFR Part 20.
Question 4
Which type of radiation has the greatest penetrating power and requires lead or
concrete shielding for protection?
A) Alpha particles
B) Beta particles
C) Gamma rays
D) Neutrons
C) Gamma rays
Gamma rays are high-energy photons with very high penetrating power. They can pass through
several centimeters of lead or several feet of concrete. Alpha particles can be stopped by paper, and
beta particles can be stopped by a few millimeters of aluminum. Gamma rays require dense
shielding materials like lead (minimum 5 cm) or concrete (minimum 30 cm) for adequate protection.
This is a critical principle in the ALARA (As Low As Reasonably Achievable) approach to radiation
protection, as specified in 10 CFR 20.1201.
Question 5
The energy of gamma radiation is measured in:
A) Roentgens (R)
B) Rads (Radiation Absorbed Dose)
C) Electron volts (eV) or Million electron volts (MeV)
D) Curies (Ci)
C) Electron volts (eV) or Million electron volts (MeV)
Gamma ray energy is measured in electron volts (eV) or million electron volts (MeV). One electron
volt is the energy gained by an electron when accelerated through a potential difference of one volt.
Roentgens measure ionization in air, rads measure absorbed dose, and curies measure activity
(decay rate). Understanding the distinction between these units is essential for radiation safety
personnel, as outlined in AMMO-66 Module 04 and 10 CFR Part 20.
Question 6
Beta particles are:
