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understand your dose

Understand your dose

Your passive dosimeter is designed to measure the doses of ionizing radiation to which you have been exposed during your professional activities. On this page, we will explore the concept of passive dosimetry, dosimeters suitable for your exposure, as well as the various types of ionizing radiation, their measurement, and their effects on health.

What is dosimetry?

Dosimétrie passive

Individual dosimetry is the measurement of the dose received by an individual.

It can be of two types: internal or external.

For internal dosimetry, the source is located inside the body. It can occur after ingestion, inhalation of radionuclides. Measurement is carried out through the analysis of excreta (urine, feces, etc.), in vivo dosimetry, or through anthroporadiametry.

For external dosimetry, the source is located outside the body, resulting in irradiation. Measurement is done using dosimeters.

In the context of professional exposure, regulations require at least the wearing of a passive dosimeter for all classified workers entering monitored areas.

The implementation of dosimetry is generally overseen by the Radiation Protection Adviser (RPA) .

The different types of dosimeters, how are they worn?

The personal dosimeter is worn:

  • At the chest and under the lead apron if necessary
  • At extremities (finger, wrist, ankle…)
  • As close as possible to the lens of the eye with the sensor between the lead glasses and the head

The passive personal dosimeter is worn for a defined period (monthly or quarterly), depending on the nature and dose expected to be received.Please, always follow the instructions of your the Radiation Protection Adviser (RPA).

Outside of wear times, the dosimeter should be stored on a badge board outside regulated areas with the lowest possible background noise. This location should always have a control dosimeter, clearly identified as such, which should never be worn under any circumstances.

Radiation protection
What is a Sievert?

The sievert accounts for the biological effect produced by a given absorbed physical dose on a living organism.

It is the unit of equivalent or effective dose.

The dose equivalent is not a directly measurable physical quantity but is obtained through calculation. It depends on the energy imparted to tissues, the type of radiation, and the tissue traversed.

One sievert is equivalent to one joule per kilogram.

[Sv] =⁻¹

The dose expressed transmitted by the dosimetry laboratory is in sieverts, for reference:

1 Sv = 1000 mSv = 1,000,000 µSv

What are the different types of ionizing radiation?

There are many types of radiation, some visible and others invisible. Most of them are non-ionizing, such as radio waves, microwaves, and infrared radiation.

Radiation is considered ionizing when it is capable of removing electrons from matter. This includes, among others, ultraviolet, X-ray, or gamma-ray radiation.

To become more stable, a nucleus can emit various types of radiation: alpha, beta, gamma, and X-rays. These radiations are of different natures and do not have the same penetration power.

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What are the effects of ionizing radiation?

The deterministic effects occur after exposure and may include symptoms such as nausea, vomiting, fatigue, and skin lesions (radiodermatitis). The onset of effects can range from hours to several months, or even years for cases of fibrosis or cataracts.

Stochastic effects may take years, or even decades, to manifest and can include cancers, cardiovascular diseases, and congenital malformations. They are more difficult to predict and attribute to exposure to ionizing radiation, especially in cases of low doses and over longer periods.

The impact of ionizing radiation on health depends on several factors, such as the dose of radiation received, the duration of exposure, the type of radiation, and individual sensitivity to radiation.

In practical terms, what does a dose of radiation represent?

For annual cumulative doses:

  • 1.1 mSv: Average exposure for medical reasons in European Union
  • 2.4 mSv: Worldwide average of background natural radioactivity
  • 12.5 mSv: Average natural radioactivity on Kerala Coast (India)

For point doses:

  • 0.006 mSv: Approximate value for a dental panoramic X-ray
  • 0.02 mSv: Approximate value for a chest X-ray
  • 0.06 mSv: Round-trip Paris / New York flight
  • 0.1 mSv: Approximate value for an arm X-ray
  • 4 mSv: Approximate value for a mammogram
  • 12 mSv: Approximate value for an abdominal CT scan
  • 100 mSv: Lowest known level with carcinogenic effects
  • 400 mSv: Maximum dose received in one hour during the Fukushima disaster
  • 2,000 mSv: Approximate value for localized radiotherapy
  • 6,000 mSv: Approximate exposure for workers who worked at the Chernobyl site during the disaster