Measuring radioactive doses
Dosimetry, the measure of absorbed radioactive doses, is a vital tool in the field of radioprotection. Being able to measure the radiation present in a specific place or felt by a specific person (referred to as individual dosimetry) is crucial to being able to calculate the average or effective doses in the area.
Dosimetry in nuclear medicine
Thermoluminescent ring used for the radioprotection of the staff of a Nuclear Medicine Service handling radioactive substances with gloves. These dosimeters measure the doses at fingertips.
There is a large variety of situations in which radioactive doses need to be measured, and an equally large variety of rules and regulations governing the maximum doses allowed. These two factors have led to the development of different detection techniques, techniques which are constantly improving with time.
Individuals who are frequently exposed to radioactivity, either by working in the nuclear industry or elsewhere, regularly wear dosimeters to measure and control the doses absorbed. This worker from the Brennilis demolition plant wears an electronic dosimeter in addition to the legally required strip of dosimetric film. The advantage of the electronic device is that it allows him to check the instantaneous dose absorbed at any given time, as opposed to the average value indicated by the film.
The oldest and best-known of these techniques is the dosimetric film, a method that is still useful in measuring the dose present over a short period of time. Its major drawback, however, is its inability to follow the variation in exposure over longer stages.
Individual dosimetry should, ideally, fulfil a wide range of tasks. Apart from providing permanent surveillance (to ensure that the absorbed dose does not surpass the legal maximum), it should also say more about the type of radiation, the nature of the risks, and serve as an automatic alarm.
Such dosimeters would also need to work in almost every conceivable environment (varying temperatures, levels of humidity, geographical position etc.), and have high levels of precision. Higher store is placed on robustness than on accuracy, however, as even an approximate measurement is better than none at all...
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