Dosimeter

November 1, 2021

The dosimeter is a measuring instrument for protection against radiation hazard . Radiation is the emission of waves or particles, there are many types of radiation and we are all subjected to it daily. However, if it is carrying high levels of energy, an ionizing effect occurs.

This process of abundant energy emission ionizes the objects with which it comes into contact, having adverse consequences on biological organisms. Radioactive agents can be substances with unstable atomic nuclei, although the different types of radiation are emitted by different sources, for example, the thermal that is emitted when a body is at a very high temperature.

The first dosimeters were created in 1970 in response to the need created by the increase in diseases that occurred as a result of the development of technology that emits radiation. They were called field effect transistors but they did not have great sensitivity, so it took time and a great team to perfect their operation.

What is a Dosimeter?

The Dosimeter is a radiation measurement instrument , it is used in dosimetry which is a scientific subspecialty dedicated to the calculation of radiation absorbed by tissues, it belongs to the field of medical physics. The radiation emitted is read in sieverts (SV), where one sv is equal to 1 joule per kilogram.

Remember that the joule is the unit by which energy, electricity and heat are measured; Therefore, 1 sv would indicate the absorption of 1 joule (energy) for the kilograms that the body has exposed. Apart from sv, measurements in grays (GY), and rad and rems are also known, for which 100 rad / rem is equivalent to 1 sv / gy.

Dosimeters are made of polyethylene, which is common plastic. They have a screen where the radiation reading appears and additionally has a vibrating alarm in case of a high reading. Its operation is due to the sensitivity of the films that have a celluloid support coated with silver halide crystals.

These crystals interact with the electrons that are released in ionizing radiation, generating an image that leads to measurement. The films are sensitive to light, humidity and high temperatures so they have an opaque packaging, but care should be taken not to expose the dosimeter to these conditions.

What is a Dosimeter for?

Radiation is not easily perceivable, in fact, when symptoms derived from its absorption begin to show, significant and irreversible damage to cells has already occurred. The dosimeter as an instrument, measures the levels of radiation emitted and / or absorbed by a body , allowing the person to know their level of radiation exposure.

In fact, personal dosimetry has been developed to constantly monitor the degree of radiation exposure of people working in hazardous environments. These dosimeters are for personal use, transportable and must be carried by staff at all times while in the exhibition area.

How does a Dosimeter work?

The dosimeter may seem like a complex instrument, but it is actually quite simple to use; being easily manipulated for those who need it. The dosimeter should be placed in a place like the chest where the greatest amount of radiation will be received.

At the time of use, your reader must be at “0” and at the end of using it, it must also be set to “0”. This must be calibrated and for this the “calibration curve” is used but these are already calibrated. Its storage is carried out in an environment with relative humidity conditions of 40% and a temperature of 21 ° C.

Uses of a Dosimeter

The dosimeter is mandatory in any place that works with material, substance or technology that generates radiation. Such as a nuclear thermal power plant, nuclear fuel processing plants, exploitation of radioactive minerals, manipulation of machinery that generates radiation greater than 5kv, etc.

For this, personal dosimeters are used , which are for exclusive use, they must be used in such a way that they receive the same type of exposure as the person. Therefore, if said person wears a protective suit, the dosimeter is placed under it to maintain the same level of exposure, likewise it should not be used outside the work area to keep its measurements accurate.

Dosimeters are mandatory for use in places with risk of ionizing radiation exposure, they have a maximum authorized measure to which a person can be exposed in a certain amount of time, and this is read in msv ; the only way to determine such exposure is by using the dosimeter.

Dosimeter types

The dosimeters are differentiated into three classifications, the personal ones, by readability and by area of ​​use. However, the classification by area of ​​use are equally personal, but they are not differentiated by operation but by design. Those of readability are of two types, the electronic ones that offer a direct reading and those that do not. Those for personal use are the following:

  • Feather

Named for its shape, it detects gamma, beta, and x-ray radiation. It works by reducing the voltage of an internal capacitor through exposure to ionizing radiation.

  • Film

Classic operation through film that blackens when in contact with radiation. The downside to this method is that the result must be compared with other films.

  • Termoluminiscencia

It performs its measurement by reacting x or gamma rays with the instrument’s crystals. It is sensitive to the amount of light emitted by radiation.

Those of area are three, ring, used by people in the area of ​​nuclear medicine; the wrist ones, used in radiofrequency and whole body. As you can see, these vary in the area of ​​the body to be used, which depending on the job will be the most exposed to radiation.

Characteristics of a Dosimeter

If you are in a situation where you need to use the dosimeter, it is best to know the instrument as deeply as possible; Since they are used in risky environments, it is vital to know their operation to determine if they are performing the measurements correctly. So I will name its characteristics to better understand the instrument :

  • They are made of a material called Polystyrene, which is nothing more than plastic
  • It has filters made of lead and copper, between 0.5 to 1.0 mm thick
  • Internal structure: dosimetric film or condenser
  • As it is not electrical, an optical densitometer is required to perform the reading.
  • Its dimensions vary considering the model and design

Dosimeters tend to be changed quarterly to avoid damage and reading errors. Also for reading, sometimes a dosimeter is kept with a certain standard reading, outside the radiation exposure zone and comparisons are made with the results obtained from the others.

Importance of the Dosimeter

The dosimeter is an instrument of great importance for health and safety. In nuclear accidents it has been fundamental to determine the magnitude of the event and is essential to guarantee the health of all those who work in areas exposed to radiation .

Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
This is my personal project but I also collaborate in other blogs, it is the case, the most important web on water currently exists in the US, if you are interested you can read my articles here.

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