Nuclear energy

What Is a Sievert in Radiation?

The sievert (Sv) is the SI unit of the amount of radiation derived from the quantity of ionizing radiation. The international system of units (SI) uses this unit to measure radiation. The symbol that represents this unit is Sv.

What is a sievert in radiation?

Sv measures the effect on the health of low levels of ionizing radiation.  It can be any type of radiation -e.g., X-rays, gamma rays, neutrons. Sievert is raw in dosimetry and radiation protection.

The amounts measured in sieverts represent a stochastic health risk. We define radiation dose assessment as the probability of inducing cancer or causing genetic damage.

The sievert unit is the most widely used talking about artificial and natural radiation.

Man-sievert is the unit for the collective effective dose. It is the sum of all significant individual amounts in a group of people over the period considered.

What Is the Meaning of the Equivalent Dose of Radioactive Material?

The equivalent dose is a measure of the radiation dose a tissue receives. We express it in sievert.

Specialists have made several attempts to correct the different biological effects of different types of ionizing radiation. The equivalent dose is a less actual amount than the absorbed radiation dose but is biologically more relevant.

We can get the equivalent dose for tissue by multiplying the absorbed dose by a radiation weighting factor. This factor depends on the type of radiation.

Technics can determine the effective radiation dose for an individual. To get it, you can multiply the equivalent dose in each organ by a tissue-weight factor. This weighting factor depends on the part of the body exposed to radiation.

The unit to measure the absorbed dose is the gray (Gy). It represents the energy transmitted by radiation to living tissue.

Health Effects on Humans

In some reference countries, professionally, the radiation that a person receives can not exceed 20 millisieverts (mSv) per year. In a consecutive five-year period, the maximum is 100 mSv.

The maximum is an average of 1 mSv (0.001 Sv) of an effective dose per year for the public. It does not include medical treatments.

Acute radiation syndrome (ARS) is a collection of health effects. They are due to high radiation exposure that one receives from ionizing radiation over a short period. It is also known as radiation sickness or radiation poisoning.

Some examples of doses received in the two worst nuclear disasters:

  • In the Fukushima nuclear accident, the technicians were exposed to 400 millisieverts per hour.

  • In the Chernobyl nuclear accident, the amount of radiation is estimated at 80,000 man-sieverts. However, some individuals received significantly higher doses.

  • In the Tokaimura nuclear accident, Hisashi Ouchi received between 10 and 20 sieverts. The highest dose a human has been exposed to.


Published: July 14, 2015
Last review: September 27, 2020