International
Tables for
Crystallography
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C, ch. 10.1, pp. 958-960

## Section 10.1.1. Definitions

D. C. Creagha and S. Martinez-Carrerab

aDivision of Health, Design, and Science, University of Canberra, Canberra, ACT 2601, Australia, and bSan Ernesto, 6-Esc. 3, 28002 Madrid, Spain

### 10.1.1. Definitions

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Ionizing radiation is defined as radiation that by its nature and energy has the capacity to interact with and remove electrons from (i.e. ionize) the atoms of substances through which the radiation passes. Sufficiently energetic radiations may cause permanent changes in the nuclei of the atoms of the substance. Radiation may be propagated in the form of electromagnetic radiation (X-rays and γ-rays) or particles (β and α particles, neutrons, protons, and other nuclear particles).

In the list of definitions that follows SI units will be used. The relation between these SI units and the earlier system of units is given in Table 10.1.1.

 Table 10.1.1| top | pdf | The relationship between SI and the earlier system of units
QuantitySIEarlier
Absorbed dose
[gray (Gy = J kg−1)]
1 J kg−1
0.01 J kg−1
Activity [becquerel
(Bq = s−1)]
1 Bq
3.7 × 1010 Bq
2.7 × 1011 Ci
1 Ci
Dose equivalent
[sievert (Sv = J kg−1)]
1 Sv
0.01 Sv
100 rem
1 rem
Exposure 1 C kg−1
2.58 × 10−4 C kg −1
3876 R
1 R

#### 10.1.1.2. Absorbed dose

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The energy per unit mass imparted to matter by ionizing radiation at the place of interest [SI unit = gray (Gy)].

#### 10.1.1.3. Activity

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The number of nuclear transformations per unit time occurring in a radionuclide.

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Protection against ionizing radiations such that the radiation doses received by an individual from internal or external sources, or both, are as low as reasonably achievable and do not exceed the maximum levels given in Table 10.1.2.

 Table 10.1.2| top | pdf | Maximum primary-dose limit per quarter [based on National Health and Medical Research Council (1977), as amended]
 Note: The annual MPD is typically twice the quarterly MPD.
Part of bodyMPD (i)MPD (ii)
(workers)(public)
Gonads, bone marrow, whole body 30 mSv (3 rem) 2.5 mSv (2.5 rem)
Skin, bone, thyroid 150 mSv (15 rem) 15 mSv (1.5 rem)
Hands, forearms, feet, ankles 400 mSv (40 rem) 35 mSv (3.5 rem)
Organs (including eye lens) 80 mSv (8 rem) 7.5 mSv (0.75 rem)
Abdomen of female of reproductive age 13 mSv (1.3 rem) 1 mSv (0.1 rem)
Foetus between diagnosis of and completion of a pregnancy 10 mSv (1 rem)

Note: The maximum primary dose limits as set here are advisory only, and ultimately one should strive to achieve an MPD limit as low as reasonably achievable (often referred to by the acronym ALARA), economic and social factors being taken into account.

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Ionizing radiation other than that to be measured, but which contributes to the quantity being measured.

#### 10.1.1.6. Becquerel (Bq)

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The SI unit of activity 1 Bq corresponds to one nuclear transformation per second. It replaces the curie (Ci).

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An area where the occupational exposure of personnel to radiation or radioactive material is under the supervision of a designated radiation safety officer.

#### 10.1.1.8. Dose equivalent

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Product of absorbed dose and quality factor (Subsection 10.1.1.24). This enables the dose received by individuals to be expressed on a scale common to all ionizing radiations. Where the term `dose' is used without qualification it is implied that `dose equivalent' is meant.

#### 10.1.1.9. Exposure of X-ray or γ-radiation

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A measure of the radiation at a certain place based on its ability to produce ionization in air. [SI unit = coulomb kg−1. It replaces the röntgen (R).]

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#### 10.1.1.11. Glove box

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A closed box having polymer gloves and viewing ports that is used to enclose completely radioactive materials whilst being manipulated.

#### 10.1.1.12. Gray (Gy)

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The SI unit of absorbed dose. [SI unit = 1 J kg−1. It replaces the rad.]

#### 10.1.1.13. Half life

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The period of time in which half the nuclei in a given sample of a particular radionuclide undergo decay.

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Apparatus capable of producing ionizing radiation.

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All radiation except the useful beam coming from within a protective housing.

#### 10.1.1.17. Licensable quantity

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The amount of any radionuclide or mixture thereof that is permitted under statutory regulations.

#### 10.1.1.18. Maximum permissible concentration

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The concentration of a radionuclide in the air when breathed or water when ingested that would result in an individual receiving the maximum permissible dose (to the whole body or to a specific organ depending on the radionuclide in question).

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#### 10.1.1.20. Non-stochastic effects

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Effects on a biological system in which the severity of the effect varies with the dose and for which a threshold is likely to occur.

#### 10.1.1.21. Nuclide

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A species of atom characterized by the number of protons and neutrons in its nucleus.

#### 10.1.1.22. Occupied area

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An area that may be occupied by personnel and where a radiation hazard may exist.

#### 10.1.1.23. Protective housing

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A housing of an X-ray tube or of a sealed source intended to reduce the leakage radiation to a specified level.

#### 10.1.1.24. Quality factor (QF)

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A non-dimensional factor used to reduce the biological effects of radiation to a common scale (see Table 10.1.3).

 Table 10.1.3| top | pdf | Quality factors (QF)
X-rays, γ-rays, and electrons 1
Neutrons, protons, singly charged particles of rest mass not greater than one atomic mass unit of unknown energy 10
α particles and multiply charged particles 20

1 Sv = (dose in grays) × QF.

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A laboratory in which irradiating apparatus or sealed radioactive sources are used or stored. It does not contain any unsealed radioactive material.

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The contamination of any material, surface or environment, or of a person by radioactive material.

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Any substance that consists of, or contains any, radionuclide provided that the activity of such material is greater than 0.1 Bq kg−1.

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A laboratory in which unsealed radioactive material is used or stored. It does not contain any irradiating apparatus.

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The potential danger to health arising from exposure to ionizing radiation.

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A laboratory in which unsealed radioactive material and/or sealed radioactive material or irradiating apparatus is used or stored.

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Species of atom that undergoes spontaneous nuclear transformation with consequent emission of corpuscular and/or electromagnetic radiations.

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The toxicity attributable to ionizing radiation emitted by a radionuclide (and its decay products). It is related to both radioactivity and chemical effects.

#### 10.1.1.33. Sealed source

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Any radioactive material firmly bonded within metals and sealed in a capsule or similar container of adequate mechanical strength so as to prevent dispersion of the active material into its surroundings under foreseeable conditions of use and wear.

#### 10.1.1.34. Sievert (Sv)

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The SI unit for dose equivalent.

#### 10.1.1.35. Stochastic effects

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Effects on a biological system in which the probability of an effect occurring rather than its severity is regarded as a function of dose without threshold.

#### 10.1.1.36. Unsealed source

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A source that is not a sealed source and that can produce contamination under normal conditions.

#### 10.1.1.37. Useful beam

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That part of the primary and secondary radiation that passes through the aperture, cone, or other device for collimating a beam of ionizing radiation.