| ++The Hiroshima Bomb++ |
The atomic bomb that exploded 580 meters above Hiroshima
was powered by the splitting of 855 grams of uranium. The energy released
was equivalent to 15,000 tons of TNT.
The splitting of uranium nuclei generated both initial
radiation (gamma rays and neutrons) and residual radiation. The neutron
radiation lasted a brief instant. The initial gamma rays remained at a
dangerous levels for approximately 20 seconds. Residual radiation consisted
of gamma and beta rays emitted over an extended period.
The bomb created a high-temperature, high-pressure,
fireball which grew to a diameter of approximately 410 meters one second
after detonation. The fireball emitted intense thermal rays for up to three
seconds and continued to glow for approximately ten seconds. The shock
wave at the leading edge of the blast traveled 11 kilometers in 30 seconds. |
| ++Damage by the A-bomb++ |
| ++Damage from Heat and Blast++ |
The super-hot fireball (several million degrees Celsius in the center)
emitted thermal rays primarily as ultraviolet and visible light radiation.
The temperature on the ground near the hypocenter reached three to four
thousand degrees Celsius.
The fireball also created a super-sonic shock wave and pressure of
several hundred thousand atmospheres. Around the hypocenter, this pressure
reached 35 tons per square meter. The initial shock wave was followed by
winds blowing at up to 440 meters per second.
The following table describes the damage caused by this intense heat
and blast. |
| ++Damage from Radiation++ |
As shown in the following table, initial radiation was heaviest within
two kilometers of the hypocenter. A dose of 4.5 gray is said to be the
level at which half of the exposed die. Thus, initial radiation may have
been the primary cause of death for at least half of those exposed outdoors
within one kilometer of the hypocenter.
There were two types of residual radiation. Induced radiation resulted
from the interaction of initial radiation neutrons with material in the
ground and buildings. Fallout ("ashes of death") derived from fission fragments
produced when the uranium atoms were split. Levels of induced radiation
remained high within one kilometer of the hypocenter for approximately
100 hours after the explosion. Radiation from fallout and fission fragments
was weaker but lasted longer. Furthermore, large amounts of radioactive
material fell with the black rain. |
| ++A-bomb Damage to Human Bodies++ |
The damage done to human bodies by radiation has been referred to
generally as A-bomb disease. A-bomb disease is now classified in relation
to radiation dose and is roughly divided into two groups - acute damages
and aftereffects.
Acute damage refers to symptoms that appeared within four months
of the bombing (by the end of December, 1945). In addition to complications
associated with burns and external injuries, common symptoms of radiation
exposure included hair loss, bleeding, and lowered levels of white blood
cells.
The symptoms known as aftereffects began with keloids, which appeared
the year after the bombing. Later radiation produced high rates of cataracts,
leukemia, and various cancers (thyroid, breast, lung, etc.). It also produced
high rates of birth defects among those exposed in uterus (microcephaly,
infantilism, etc.).Some victims who entered the city after the bombing
became sick or died from what is believed to be exposure to residual radiation. |
| ++Protest Telegrams++ |
Successive mayors of Hiroshima sent telegrams protesting
every nuclear weapon test since 1968.
They were sent to the countries responsible for the tests, and each
expressed the fervent hope that it would be the last such telegram.
The 567th telegram is currently the last one that protested against
a subcritical underground testing by the U.S. in February, 1999. |
| ++ Model of "Dome" reproduced on the scale of 73/100 ++ |
Huge numbers of people unable to endure the pain of their injuries
or burns jumped into the river that runs in front of the A-bomb Dome. Thousands
of corpses were seen floating in all of Hiroshima's rivers. The one-majestic
dome of the Hiroshima Prefecture Industrial Promotion Hall will be preserved
in perpetuity on the bank of the Motoyasu River as a mute reminder of the
tragedy and concrete appeal for world peace. |