Metrology

Quantities and units used in radiation protection

The metrology of ionizing radiation uses different quantities, called physical, operational or radiation protection quantities.

For the purpose of controlling the radiation source and making its metrological process more reliable, ATRON has a complete measuring chain, coupled with a control-command system.
The ambient conditions of pressure, temperature and humidity are recorded to accurately determine and control the measurement environment in order to stabilize the temperature at 19 ± 1 °C and the humidity at 50 ± 10%.
Ionisation chambers make it possible to measure in KERMA in air the ionizing radiation emitted by the ATRON installation. These chambers, connected to the primary beam by the National Metrology Laboratory (CEA / LNE / LNHB), allow calibration of the radiation survey meters with an uncertainty lower than 7%.

From physical quantities

Physical quantities are the only directly measurable ones. All other measurement quantities of ionizing radiation are traceable by calculation or calibration.

The absorbed dose and KERMA are directly measurable quantities, called physical quantities.
The dose is the energy deposited per unit mass by ionizing radiation in a medium. It is expressed in Gray (Gy). KERMA designates the kinetic energy delivered per unit mass. It is used for the dosimetry of neutral particles and is also expressed in Gray. At the electrostatic equilibrium, KERMA is proportional to the dose.
On the ATRON installation, KERMA in air is used as reference quantity for the connection of operational quantities to the national standard.

To operational quantities

Operational quantities measure the exposure of workers and the public to ionizing radiation.

Even if most ionizing radiation measuring instruments provide an indication of ambient dose equivalent H*(10) in Sv/h, this quantity is not directly measurable.
This is a useful operational quantity defined by ICRU to measure exposure of workers and the public to radiation.
Calibration of the devices for measurement of ionizing radiation, carried out by ATRON in dose equivalent rate, requires to refer to the energy spectrum of the radiation field and its intensity: H*(10) (Sv/h) = Hk (Sv/Gy) × K (Gy/h)

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