Usefull information

Activity, Becquerel

The radioactivity of a substance is characterized by its activity. It is defined as decay per second and is measured in becquerels. However, the radiation risk is not depending on the activity, but on the nature of the radiation which is released during decay.

Assignment and modification form

This form is included with each dosimeter delivery. The dosimeter numbers are imprinted on this form, and - if known - the name of the person that have been issued the dosimeter. Beside the assignment, you can also use this form for modifications, for example, if new employees apply for dosimeters. 

Body dose

The body dose includes the terms organ dose and effective dose and describes, for a certain period of time, the sum of the body dose received from external exposure during this period and the subsequent dose, which is caused by activity intake during this period (StrlSchV, §3).

Control area

According to RöV paragraph 19 and StrSchV paragraph 35, control areas are defined as areas where persons may receive an effective dose higher than 6 mSv, or organ doses higher than 45 mSv for the eye lens or 150 mSv for the skin, hands, forearms, feet and ankles in a calendar year.

Dose equivalent

The dose equivalent is the basis of the operational quantities of radiation protection measurement techniques. It is defined at a point in the radiation field in tissue as the product of:

Dose equivalent:  H = Q • D

The quality factor Q (comparable to wR) is a weighting factor for the consideration of the different radiobiological effectiveness of various types of radiation.

Dose equivalent (personal doses): quality  factor Q

Organ equivalent dose (body doses) radiation weighting factor wR.

Dose, dose quantities and dose units

The absorbed dose D, the base quantity and a physical quantity for all dose terms, is defined in the organism independently of the radiation effect. It is the energy that was absorbed in a mass element. The unit of energy dose is expressed in gray [Gy = J / kg].

In order to account for the effect of radiation, the term "equivalent dose H" was introduced. This is the basis of the operational quantities in the radiation protection measurement techniques, and takes into account the biological effects of different types of radiation. The dose equivalent results from the absorbed dose multiplied by a radiation weighting factor wR and is measured in sievert [Sv = J / kg].

The most important quantities for the practical radiation protection are: 

  • Effective dose E
    • measure for the radiation risk of mankind, specifying limit values
    • is also referred to as body dose
    • is not directly measurable

Dose measurement quantities: 

  • Personal deep dose equivalent Hp(10)
    • equivalent dose in 10 mm body depth
    • is measured with whole-body dosimeters
    • provides an estimate of effective body dose
  • Personal surface dose Hp(0,07)
    • equivalent dose in 0,07 body depth
    • is measured with partial-body dosimeters
    • estimate for the local skin dose
  • Environmental dose equivalent H*(10)
    • equivalent dose at 10 mm depth of a 30 cm sphere of tissue-equivalent material
    • is measured as a local dose at a specific position
    • provides an estimate of the effective dose at this point.

Dosimeter, dosimeter probe, detector

A dosimeter is a measuring system for determining the dose quantity. The term dosimeter comprises all components of the system, including the evaluation devices and the evaluation algorithms.

The dosimeter probe is the component of the system that is exposed to the radiation field. This may be, for example, the dose measurement film inserted in the film cassette.

The radiation-sensitive part of a dosimeter is the detector. For the film badge, the detector is the film, for the OSL or TLD dosimeters, the detector is the chip or the crystal, respectively.

Dosimetry

The term dosimetry refers to the measurement of radiation, which is relevant for the assessment of radiation risks. As part of the radiation protection, this technique is usually applied to measure the radiation dose caused by ionizing radiation.

Exposure, radiation exposure

Describes the radiation exposure of a person or a dosimeter.

Film badge dosimeter

The film badge dosimeter is the most commonly used  type of dosimeter. The detector, i.e. the film is worn in an opaque sheath which is  inserted into a cassette. This cassette is equipped with various filters.

The film is exposed by ionizing radiation and visible light. After developing,  different degrees of blackening occur behind the individual filter fields.  The blackening of the film is measured by densitometry, and then the dose behind the individual absorption filters is determined from the blackening.  

Measurement of dose quantities

Generally, the dose is a measure of the total radiation risk within a certain period of time - it is therefore dependent on the exposure time in a radiation field. As in a uniform radiation field the dose is steadily increasing with the time spent in the radiation field, dose limit values are set for specific time intervals. For the dose measurement itself, the measurement results are added up over a predetermined time. For this purpose, the dosimeter must be able to store measurement values, a property that should be inherent in its measurement system (e.g. physical measurement value storage in TLD). Dosimeters, which store values through their own measurement system, are called passive dosimeters. Active dosimeters, however, detect the dose through a continuous dose rate determination that can be directly displayed.

Monitoring area

A monitoring area, defined as not belonging to the control area, is an operation area in which persons may receive an effective dose higher than 1 mSv, or organ doses higher than 15 mSv for the eye lens, or 50 mSv for the skin, hands, forearms, feet and ankles in a calendar year.  

Optical density

The optical density is defined by the densitometric measurement and is the measure of the blackening degree of a film. After a light beam has passed through the film, the light intensity (I0) is measured both before and behind the film.

Optically Stimulated Luminescence

The principle of optically stimulated luminescence (OSL) is similar to the principle of the thermally stimulated luminescence (TL). Energy in the form of ionizing radiation collides with the BeO-based detector and is stored by lifting electrons to higher energy levels.

In this process, electrons are caught in so-called electric traps until an excitation by light occurs again so that the electrons fall back to a lower energetic basic level. In this manner, the detector releases the stored energy in the form of light, i.e., it is stimulated to emit light. The light output measured with photomultipliers is a measure unit for the dose.

Unlike in the thermally stimulated luminescence, the excitation in the optically stimulated luminescence is achieved by light and not by heat.

Partial-body dosimeters

Partial-body dosimeters are used in locally limited radiation fields and for determining the partial body dose. For this purpose, ring dosimeters are used.

Compared to the limit values set out for whole-body doses, the limit values for the partial-body doses are higher because they include only the risk for the respective body areas. Depending on the affected organ, these values are different.

Personal dose

The personal dose refers to the dose equivalent measured at a representative point of the body surface exposed to radiation.

Radiation (ionizing)

Photon or particle radiation, which can lead to the formation of ions.

Radioactivity

The ability of a substance to transform over time into another substance is referred to as radioactivity. The process of transformation through the radioactive decay of individual nuclei is completed in stages. Although it is impossible to predict when a particular atom will decay, the course of time of the decay can, however, be calculated for a large number of substances. The time in which the half of the atomic nuclei are transmuted is called half-life. In addition to the half-life, there is another parameter for the radioactivity of a substance: namely, the activity. Usually, during the nuclear decay process, energy is released in the form of nuclear radiation.

Radon

Radon is a natural radioactive noble gas that is formed from the decay of radium in the soil. The gaseous radon can escape from the ground and accumulate in caves, buildings, mines or in the groundwater. Such accumulations cause radon concentrations that constitute a radiological pollution of breathing air.

Radon concentration, radon exposure

Radon concentration is expressed in becquerels per cubic meter, and describes the amount of radon in a given volume of air.

The radon pollution during a specific time interval defines the radon exposure. It is the product of the residence time and the average radon concentration, and is expressed in becquerel hours per cubic meter.

Responsivity of a dosimeter probe

The responsivity of a dosimeter probe is defined by the ratio of the measurement display to the true dose value and represents a comparison value for the characterization of the dosimeter sensitivity.

Sievert (Sv), Gray (Gy)

Sievert is the measure unit of differently weighted radiation doses and the unit of the dose equivalent H. The sievert unit is used to analyze the radiation risk and to determine the radiation exposure of biological organisms.

Gray is the unit for the absorbed dose D and it describes the energy absorbed per mass without taking into account the different biological effects of radiation.

StrlSchV - Radiation Protection Ordinance

The Radiation Protection Ordinance is under the Atomic Energy Act a regulation on the protection against damage caused by ionizing radiation. It regulates the use of radioactive materials and nuclear fuels as well as the construction and operation of facilities for the generation of ionizing radiation. The construction and operation of X-ray equipment and sources of stray radiation are excluded - they are subject of the X-Ray Ordinance.

Thermoluminescence (TLD)

TLD are doped solid-state materials that can store the energy of ionizing radiation in the detector crystal and release this upon selective heating in the form of light. The light intensity is a measure unit for the absorbed radiation. Through heating, the detector is at the same time reset to zero and can be used again.  

Types of radiation

Ionizing radiation can occur in the form of photon or particle radiation.

Photon radiation, like visible light, is an electromagnetic wave. There is a distinction between X-rays and gamma rays. Through deceleration of electrons, for example in X-ray tubes, x-ray radiation is formed. The gamma radiation, however, is a photon beam which is emitted by radioactive substances. The X-ray radiation covers the low energy range from 5 to 400 keV, the gamma radiation covers a higher one in the MeV energy range.

Electron (beta) and neutron (gamma) radiation is a particle radiation. In dosimetry, alpha and ionizing radiation plays only a minor role, since they have very short ranges and are already shielded by air or clothing.

Verification threshold

The measured personal dose values, that are smaller than this threshold, are considered as body dose. If higher values are determined, an individual test must be carried out.

Whole-body dosimeter

Whole-body dosimeters are used to measure the personal dose. They are also used in not locally limited radiation fields. Since a uniform irradiation is expected here, the limit values for  the whole-body dose are lower than those of the partial-body doses.

X-ray Ordinance (RöV)

The X-ray Ordinance (Ordinance on the protection against damage caused by X-rays) regulates the construction and operation of X-ray facilities as well as sources of stray radiation with acceleration energies between 5 keV and 1 MeV.

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