2.1 What Radiation and Radioactivity Are
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Table 2.4 Properties of neutron radiation
What will emit neutron radiation • Neutron sources (soil gauges, well-logging sources, AmBe,
and Cf-252 neutron sources)
• Operating nuclear reactors
• Particle accelerators (research, medical)
• Nuclear weapons (low level)
Detectors and instruments
Neutron detectors (Helium-3, BF3, and others)
Health effects
• External neutron radiation can expose the entire body
(including internal organs)
• Many neutron sources also emit alpha radiation
Protective equipment
• Anti-contamination clothing to reduce skin contamination
• Respiratory protection (if airborne)
• Cover open cuts, scrapes, or wounds
Levels of concern
• Any sustained neutron dose rate above natural background
levels should be investigated
Other comments
• Background neutron levels will vary widely
• Different instruments will have different background
neutron levels
• Neutron levels can increase somewhat when near large
structures (called the “ship effect”) on the water or on land
lower-energy x-ray radiation. Table 2.3 summarizes some important information
about gamma radiation.
2.1.4 Neutron Radiation
Neutrons are subatomic particles that are given off during nuclear reactions such
as nuclear fission or from radioactive sources comprised of beryllium mixed with
an alpha-emitting radionuclide (e.g. Am-241 and beryllium, or AmBe). Neutrons
are highly penetrating and will pass through most solid materials; they are best
shielded by using hydrogen-rich materials (e.g. water, plastic) and neutron-absorbing
elements such as boron. Bombarding materials with neutrons can cause them to
become radioactive. Due to their higher mass, neutrons are much more biologically
damaging than are beta particles or gamma rays; neutron absorption can also cause
materials to become radioactive. Table 2.4 summarizes some important information
about neutron radiation.
2.1.5 Radioactivity Units
Radioactivity is measured in terms of the number of radioactive decays (also referred
to as “disintegrations”) an amount of radioactive material (a radioactive source)
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Table 2.4 Properties of neutron radiation
What will emit neutron radiation • Neutron sources (soil gauges, well-logging sources, AmBe,
and Cf-252 neutron sources)
• Operating nuclear reactors
• Particle accelerators (research, medical)
• Nuclear weapons (low level)
Detectors and instruments
Neutron detectors (Helium-3, BF3, and others)
Health effects
• External neutron radiation can expose the entire body
(including internal organs)
• Many neutron sources also emit alpha radiation
Protective equipment
• Anti-contamination clothing to reduce skin contamination
• Respiratory protection (if airborne)
• Cover open cuts, scrapes, or wounds
Levels of concern
• Any sustained neutron dose rate above natural background
levels should be investigated
Other comments
• Background neutron levels will vary widely
• Different instruments will have different background
neutron levels
• Neutron levels can increase somewhat when near large
structures (called the “ship effect”) on the water or on land
lower-energy x-ray radiation. Table 2.3 summarizes some important information
about gamma radiation.
2.1.4 Neutron Radiation
Neutrons are subatomic particles that are given off during nuclear reactions such
as nuclear fission or from radioactive sources comprised of beryllium mixed with
an alpha-emitting radionuclide (e.g. Am-241 and beryllium, or AmBe). Neutrons
are highly penetrating and will pass through most solid materials; they are best
shielded by using hydrogen-rich materials (e.g. water, plastic) and neutron-absorbing
elements such as boron. Bombarding materials with neutrons can cause them to
become radioactive. Due to their higher mass, neutrons are much more biologically
damaging than are beta particles or gamma rays; neutron absorption can also cause
materials to become radioactive. Table 2.4 summarizes some important information
about neutron radiation.
2.1.5 Radioactivity Units
Radioactivity is measured in terms of the number of radioactive decays (also referred
to as “disintegrations”) an amount of radioactive material (a radioactive source)