# What is the sievert?(unit that shows exposed dose to living body)

To show strength of the radiation in the nuclear plant, it often hears of micro sievert/hour on the television and the radio, etc.What one is this?

## The sievert is a unit that shows the exposed dose to the living body.

Sievert (Sv) is a unit that shows the exposed dose to the living body. The sievert is an amount of exposed dose, and no ,in a word, strength of the radiation.

## Radiation exposure each unit time dose shows strength of the radiation.

The exposed dose each unit time is used for showing strength of the radiation to the living body. The unit is shown by radiation exposure an hour dose. However, radiation exposure an hour dose should be only called a sievert, and it note it in the report such as the televisions because it is likely to use it as strength of the radiation.

## Relation between micro sievert and millisievert

Might it be said the micro sievert, and say millisievert. μ is 1/1,000,000, and the milli is 1/1,000. Saying millisievert, it increases to 1,000 times that of the micro sievert.

1 [Sv] = 1,000 [mSv], and 1 [mSv] = 1,000 [μSv]

## Amount of natural radiation

The amount of the natural radiation that excludes the inhalation such as radons in Japan reaches a value different by the composition of the rock of the land and the region. In Japan 0.8-1.2 It becomes the value of [ mSv/year ]. West Japan's amount of the radiation tends to be larger than that of East Japan. This is because of abounding reaching of West Japan granite to surface of the earth directly.

A large amount of radiation ..human body.. becomes harmful though very small amount radiation like the natural radiation never almost influences the human body. The unit used when it knows the human body received doses of radiation of which extent is a sievert.

The exposed dose from the radon in air is called 1.26 millisieverts year. This radon is the one that leaks from the earth interior and comes out, and exists in the natural world. When the amount of this and the above-mentioned natural radiation is added, the amount of the natural radiation that our living body receives will be called 2.4 millisieverts in one year.

## Symptom of amount of radiation radiation exposure and human body received in short course

150 millisieverts = man temporarily becomes infertility.

250 millisieverts = Decrease white blood corpuscle

500 millisieverts = Decrease lymphocyte

1 sievert = Acute radiation damage happens. Becoming turbid of evil intention, vomiting, and crystalline lens etc.

## Doses of radiation that person dies

2 sieverts = The person of 5% dies.

4 sieverts = The person of 50% dies.

7 sieverts = The person of 100% dies.

## Exposure in medical institution

The radiation exposure dose when the CT inspection is undergone once in the hospital is about 7 millisieverts. There is an exposure of 0.5-3 millisieverts in the X rays taking a picture of the stomach. The exposure in the medical testing seems to have to worry from the natural radiation.

## Radiation exposure dose allowed by law(The exposure by the natural radiation and treatment is excluded.)

The doctor or neither engineer nor the nurse who treats the radiation and the radioactivity must exceed 20[ mSv/year ].

A general person must not exceed 1 [ mSv/year ]. When this is added, natural doses of radiation become 3.4[ mSv/year ] on this because there is 2.4[ mSv/year ]. (This is about 0.4 [μSv/h] )

## Strength of radiation due to accident of nuclear plant

Strength of the radiation in the site due to the nuclear reactor accident of the first nuclear plant in Fukushima March 15, 2011 was broadcast with 400 millisievert per hour. Strength of this radiation is very dangerous. It is strength that the person of 100% dies when it is defenseless and it exists here for 18 hours.