Table 2-1. Neutron Flux Densities to be Regarded as Equivalent to a Radiation Level of 1 Millirem per Hour (mrem/h) *

TM 55-315

Table 2-1. Neutron Flux Densities to be Regarded as Equivalent to a Radiation Level of 1 Millirem per Hour

(mrem/h) *

Flux density equivalent to 1 mrem/h (Neutrons per square

centimeter per second) (n/cm2/s)

Energy of neutron

Thermal

268.0

5 keV

228.0

20 keV

112.0

100 keV

32.0

500 keV

12.0

1 MeV

7.2

5 MeV

7.2

10 MeV

6.8

* Flux densities equivalent for energies between those listed above may be obtained by linear interpolation.

c. Gamma Radiation. Gamma radiation is high-energy electromagnetic radiation similar to x-rays. Compared on

the basis of the same energy, gamma rays are more penetrating than alpha or beta particles.

d. Neutron Radiation. The intensity of neutron radiation is expressed in terms of "neutron flux", which is the

number of neutrons passing through a unit area in a unit time. A neutron is an uncharged particle present in all atomic

nuclei except those of light hydrogen. Compared on the basis of the same energy, neutrons are more penetrating than

beta particles and may be more or less penetrating than x-rays or gamma rays, depending upon the neutron cross

section of the interacting medium.

2-32. Radiation Units

Radiation units are indirect measures of the quantity of radiation. In this manual, radiation units are the radiation

absorbed dose (rad), roentgen (R), and roentgen equivalent man (rem).

2-33. Radioactive Article

A radioactive article is any manufactured instrument or article that has radioactive material as a component part.

2-34. Radioactive Contents

Radioactive contents are the radioactive materials, together with any contaminated liquids or gases, within the package.

2-35. Radioactive Decay Chain

A radioactive decay chain is a succession of nuclides, each of which transforms into the next until a stable nuclide is

formed. The first member of the series is called the parent, the intermediate members are called the daughters, and the

final member is called the end product.

2-36. Radioactive Material

Radioactive material is any material with a specific activity greater than 0.002 microcurie per gram (uCi/g) (see para 2-43

below).

2-37. Radionuclide

A radionuclide is a species of atom, characterized by the number of protons and neutrons in its nucleus, that exhibits the

property of radioactivity.

2-38. Radionuclides, A1 and A2 Values

Table 2-2 lists the A1 and A2 values for radionuclides.

2-39. Roentgen (R)

A roentgen is that quantity of X or gamma radiation that will produce, as a result of ionization, one electrostatic unit of

electricity, of either sign, in 1cc of dry air at 0 and standard atmosphere pressure. The mass of 1cc of dry air under the

standard conditions specified is 0.001293 gram. One roentgen is equivalent to energy absorption of 86.9 ergs per gram

in air. A milliroentgen (mR) is one-thousandth (10-3) of a roentgen.

2-40. Roentgen Equivalent Man (rem)

The rem is a measure of the dose of any ionizing radiation to body tissue in terms of its estimated biological effect

relative to a dose of one roentgen of x-rays. (One millirem (mrem) equals one-thousandth (10-3) of a rem.) The relations

of the rem to other dose units depend on the biological effect under consideration and the conditions of irradiation. For

this manual, any of the following is considered to equal a dose of 1 rem.

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