Theory:

Permitted range of radiation:
The International Commission on Radiological Protection (\(ICRP\)) has recommended specific maximum acceptable radiation exposure limits that are thought to be safe without causing any significant harm to people. The safety limit for overall radiation exposure is \(20\ milli\ Sieverts\ per\ year\).

The safety limit of roentgen exposure is around \(100\ mR\) per week. When exposed to \(100\ R\), it can result in fatal diseases like leukaemia (the destruction of red blood cells in the blood) or cancer. If a body is exposed to \(600\ R\) for an extended period of time, it leads to death.
Dosimeter:
A dosimeter is a device that detects the amounts of ionising radiation exposure.
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Dosimeter
 
The device is commonly employed in areas such as nuclear power plants and medical imaging facilities, where radiation exposure is possible. The wearer of a pocket dosimeter receives an instantaneous reading of their exposure to \(X-\ rays\) and \(γ-\ rays\).
Preventive measures:
1. Radioactive materials should be stored in a lead container with a thick wall.
 
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Lead container
 
2. While working with harmful radioactive materials, lead-coated aprons and gloves should be worn.
 
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A man wearing a lead apron
 
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Lead apron and gloves
 
3. One should avoid eating while working with radioactive materials.
4. Only tongs or a remote control device should be used to handle radioactive materials.
5. Users should use dosimeters to monitor their exposure to radiation.
Reference:
https://commons.wikimedia.org/wiki/File:Lead_Apron_worn_by_Dr_Danny_Sands.jpg
https://commons.wikimedia.org/wiki/File:Radiation_protection_apron,_1920-1958_Wellcome_L0065297.jpg
https://upload.wikimedia.org/wikipedia/commons/6/6d/Gelbe_Tonne.jpg