For personal dosimetry, the standard procedure is to wear an individual whole body dosemeter on the chest. Depending on the specific requirements, this can be supplemented with a wrist, finger, eye lens or lead apron dosemeter. Some 10,000 Belgians and Dutch are currently wearing a dosemeter of the Belgian Nuclear Research Centre.
The various types of dosemeters all consist of a holder in which the dosemeter itself is inserted. Inside the dosemeter are the detectors that are sensitive to both beta and gamma rays.
The radiation dose of professionally exposed employees is usually monitored on a monthly basis, but the exchange of the dosemeter every three months is also possible. The natural background radiation is subtracted from the result.
As of today, SCK•CEN offers two types of personal dosemeters. TLD dosemeters are not offered anymore. In 2017, a new type of dosemeter was brought into use, the InLight dosemeter which is based on optically stimulated luminescence (OSL). From 2019 on, the Instadose dosemeter is also offered. This dosemeter uses a miniature ionisation chamber.
InLight Body Dosemeter
The InLight dosemeter detects beta radiation as well as X-rays and gamma radiation. The dosemeter is made of four active items. The 4 detectors consist of carbon doped aluminium oxide but are also positioned behind 4 different filters included in the case. These filters allow to determine the energy of the incident radiation, so that the dosemeter responds in a tissue equivalent way to all radiation energies. This dosemeter detects beta radiation as well as X-rays and gamma radiation so that it measures the depth dose Hp(10) and the surface dose Hp(0,07). One of the advantages of this dosemeter is that we can read it multiple times.
Facts & Figures: InLight dosemeter
- Minimum detectable dose: 50 µSv
- Measuring range: 50 µSv to 10 Sv
- X-rays and gamma energy range: 12 keV to 6 MeV
- Beta energy range: 700 keV to 2.3 MeV (expressed in max E)
- Small and light: 7.5 cm high, 1 cm thick, 18 g
More info in our leaflet
Instadose Body Dosemeter
The Instadose dosemeter of Mirion Technologies is based on the technique of Direct Ion Storage (DIS). Using this technique, incident ionizing radiation creates electrical charges in a small ionization chamber. This charge is then collected in a semi-conductor memory cell. The collected charge is a measure of the accumulated dose received. At the time of lecture, the charge is non-destructively determined via a voltage measurement. Charge is thus accumulated, it will never be lost. The dose for a given period is then evaluated as the difference between two measurements.
The Instadose dosemeter is available in two versions: Instadose+ and Instadose2. The second type measures as well Hp(10) as Hp(0.07). If your application does not require the measurement of Hp(0.07) you can opt for the slightly cheaper version, the instadose+.
Facts & Figures: Instadose dosimeter
- Minimum detectable dose: 80 µSv
- Measuring range: 80 µSv to 1 Sv
- X-rays and gamma energy range: 24 keV to 1.25 MeV
- Small and light: 5 cm high, 1 cm thick, 18 g
More info in our leaflet.
If radioactive products are manipulated by hand, it may be necessary to also wear a finger and/or wrist dosemeter in addition to a body dosemeter on the chest. Like a body dosemeter, a wrist dosemeter contains three detectors. Ring dosemeters consist of a plastic ring with one single thermoluminescent detector.
When a ring or wrist dosemeter is worn, it is important that the detector is directed as much as possible towards the source of radioactivity; usually this means facing the inside of the hand or the wrist. Examples of personnel who wear finger dosemeters are operators working in a nuclear medical department or people working in glove boxes.
Eye lens dosimetry
The existing dose limits for the eye lens were recently made stricter. This means that it is recommended to wear an eye lens dosemeter for certain applications, for example for cardiologists who are working in an interventional cardiology department. Please contact the SCK•CEN dosimetry expert group for information in this field.
Lead apron dosimetry
When a lead apron is used for radiation protection, the question arises as to whether the dosemeter should be worn above or underneath the lead apron. In this case, SCK•CEN suggests double dosimetry. The person then wears a body dosemeter above as well as underneath the lead apron. For the read-out and reporting of the exposure dose, the dosimetry laboratory uses an algorithm that takes the results of both dosemeters into account.