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Radiation is an invisible but crucial part of our environment. Understanding radiation norms, including natural background levels, maximum doses, and radiation in food, is essential for safety. In this article, we will explore the key aspects and standards of radiation that everyone should be aware of.
Different countries have varying norms, often contradicting each other. Therefore, we will use the strictest values. Norms increased after radiation accidents will not be considered.
All norms are based on the accumulated dose. The maximum allowable radiation dose for a person is considered to be 1000 µSv per year. However, this dose does not include the natural radiation background. Adding the average radiation background, we get 1500-2000 µSv per year. The natural radiation background typically ranges from 0.05 to 0.10 µSv per hour. This will be our baseline.
If the annual limit is converted to an hourly rate, 2000 µSv equates to a radiation level of 0.22 µSv/h over the course of a year. Therefore, you would need to live in a place with this background level for a year to accumulate 2 mSv.
However, since people do not spend 100% of their time in one place, such as a home with this background level, the background level in a home should exceed 0.40 µSv/h to accumulate a dose above 2000 µSv.
A level up to 30 µSv/h is considered normal for residential areas. However, I would not recommend living at 0.30 µSv/h; it’s better if the background level is lower.
A small radioactive object measured close to the device can show quite high figures. These indicators can be alarming. It may seem that the 2000 µSv norm can be quickly accumulated under such conditions. However, since we measure close to the source, the high dose rate only exists on the surface of the radiation source and can only irradiate a specific part of the body, like a hand. Consequently, the harm will be different, and the chance of developing cancer will be lower.
To calculate the harm to the entire body, measurements should be taken at a distance of 1 meter from the source. Here, the inverse square law comes into play; the radiation from the source weakens incredibly with distance. Most radiation sources are undetectable by instruments at a one-meter distance. Even powerful sources show only a negligible fraction of what they indicate up close.
Thus, if a radiation source has been near you for a long time, the dose rate from it should be measured where you were, not at the source. Additionally, the exposure time and dose rate at the exposure site must be calculated.
This is an area where most dosimeter owners lack knowledge and make mistakes. You cannot simply bring any dosimeter close to food and determine if it contains dangerous levels of radioactive materials. The problem lies in the norms. For a person, the radiation levels in food are so small that if a dosimeter reacts to food in normal mode, it means the food contains thousands of times the allowable limit. If the excess is not so high but still dangerous to health, ordinary and even professional devices will show nothing.
Sensitive scintillation devices with a special mode for measuring activity are required for measurements not influenced by the surrounding background. The food itself also needs preparation, as different geometry and weight can affect the readings. These measurements are not quick; it can take at least an hour.
Only in such conditions can the activity of food products be measured. The Radiacode dosimeter is sensitive enough for such measurements. It has a special mode and several container options for measurements, with their geometry programmed into the software.
Radioactive isotopes accumulate in the body and irradiate it from within for years. Even small amounts of radioactive substances, if present in the body for a long time, can result in a high dose.
The unit of activity for measuring food contamination is the Becquerel. One Becquerel equals one decay per second of a radioactive atom (not to be confused with CPS – CPS is just a registered part).
Typically, the norms for Becquerel content in food depend on the average frequency of consumption by the population. This system is very inaccurate because an unusual diet can lead to the accumulation of large amounts of isotopes in the body. I recommend avoiding food products if they contain more than 100 Becquerels per kilogram.
The good news is that there are not many food products at risk, so there is no need to check everything.
Other foods do not accumulate radiation as much and do not need checking during peacetime.
Knowing the maximum allowable levels of radiation helps to accurately assess risks and minimize radiation exposure.
