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Global Radiation Exposures

Comparison of Damage among Hiroshima/Nagasaki, Chernobyl, and Semipalatinsk

Category

Hiroshima

Nagasaki

Chernobyl

Semipalatinsk

Time

August 6, 1945

August 9, 1945

April 26, 1986

1949-1989

Cause

Atomic bombing

Atomic bombing

Nuclear power plant accident

Nuclear weapons tests

No. of those exposed

About 350,000

About 270,000

1.6-9 million

(Depending on different statistics. Details unknown.)

About 1 million

(Details unknown)

No. of fatalities

About 140,000

About 70,000

About 30 (Due to acute radiation injury)

Unknown

Scope of damage

2-km radius zone and the surrounding area

Same as on the left

The former Soviet Union and Europe

Eastern part of Kazakhstan


1.Hiroshima/Nagasaki

Radiation dose in a zone 2 kilometers from the hypocenter of the atomic bomb was the largest. Also, those who entered the city of Hiroshima or Nagasaki soon after the atomic bomb detonation and people in the black rain areas were exposed to radiation. Table 1 shows dose assessment using the dosimetry system 2002 (DS02). Radiation included gamma (gamma) rays as well as neutrons. This table shows radiation dose released at the moment of the atomic bomb detonation. In addition, some people were exposed to radiation from black rain containing nuclear fission products (“ashes of death”), and others to radiation induced by neutrons absorbed by the soil upon entering these cities soon after the atomic bomb detonation. However, radiation doses from black rain or by early entry into the cities have not been calculated in detail. The number of victims is estimated to be 280,000.

Table 1. Radiation doses using DS02

Dose

    Distance (km)

    Hiroshima (mGy)

    Nagasaki (mGy)

Gamma ray
0.5
1.0
1.5
2.0
35,700
4,220
549
81
83,000
8,620
983
138
Neutron
0.5
1.0
1.5
2.0
6,480
260
9
0.4
2,970
125
5
0.2

2.Chernobyl
In the Chernobyl accident, subsequent to the completion of nuclear fission, radiation was released from resultant fission products in the reactor; therefore, atomic bomb-type radiation which is released at the time of nuclear fission was not included. An estimated 3-4 exabecquerel (exa=1018) was released. Some say that the Chernobyl accident released as much as 300 times the lethal radioactive fallout of the Hiroshima bomb. Radiation had been released for 10 days and scattered in different directions as the wind shifted. Fallout in the form of dust or rain was scattered on earth, and people were exposed to radiation. Cecium-137, strontium-90, iodine-131, and plutonium are the major radiation source for the contamination. In addition to 135,000 residents within a 30-km radius of the nuclear power plant, 280,000 people living in the highly contaminated area were evacuated. The victims are divided into the following four groups: (1) plant operators and fire fighters at the time of the accident, (2) workers involved in the recovery and cleanup after the accident (liquidators), (3) people evacuated from the 30km zone immediately after the accident, and (4) residents in highly radioactive contaminated zone. According to the report of the former Soviet Union, about 300 people were hospitalized immediately after the accident, and about 240 people were diagnosed as having acute radiation injury. Of them, 28 people died of radiation injury. (With one missing person at the accident site, one person who died from burns on the day of the accident, and one person who died of a different disease at a later date, a total of 31 people were said to be killed by the accident.) Estimates of the number of exposed individuals vary; some reported 1,600,000, and other reported 9,000,000. These estimates can vary significantly depending on the scale and condition of exposure.

3.Semipalatinsk
At the Semipalatinsk Test Site, a total of 456 nuclear tests, including 111 atmospheric tests, were conducted for a period of 40 years from 1949. Radiation exposure in Semipalatinsk is mainly due to atmospheric tests-from radioactive clouds containing lethal fallout that resulted from nuclear explosions. A mushroom cloud that resulted from a nuclear explosion, after having attained a certain height, traveled horizontally. Under a certain meteorological condition, a cloud, as narrow as 2 kilometers in width, traveled a few hundred kilometers. Inhabitants were exposed to radiation from dusts falling out of a radioactive cloud or radioactive materials in the cloud. Unlike Hiroshima or Nagasaki, gamma rays and neutrons at the time of nuclear fission were not included. Residents in Dolon Village, who are said to have been exposed to high dose of radiation, may have been exposed to over 1Gy. Radiation contamination was observed extensively around the test site, resulting in radiation exposure of over one million inhabitants. Although the entire residents of some villages were evacuated, evacuation in Semipalatinsk was not as large-scale as that in Chernobyl.

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