Hiroshima nuclear bomb radiation?

Question

As of now, there is no effect way to clean up nuclear radiation. I heard it takes hundreds of years for the radiation from a nuclear explosion to decrease to a safe level, until then the environment within the vicinity of the explosion is uninhabitable.

Now, my question is: how could the Japanese rebuild Hiroshima and Nagasaki right after the nuclear explosion? If I'm not mistaken, there is a Hiroshima Peace Memorial Park right in the city center where the Atomic Bomb Dome marked the ground zero of the nuclear explosion.

If radiation released by an nuclear explosion is so dangerous, how can these two cities become habitable to human in such a short time?

Maybe I should ask it under Science -> Physics? Not sure if this is the right place. XD

Answer 1

A few facts to clear the air

Both the Hiroshima and Nagasaki bombs were fission weapons. Modern nuclear bombs are fusion weapons. Fusion actually releases less alpha, beta and gamma radiation than a comperable sized fission weapon. But, fusion weapons actually use a fission trigger and this releases considerable quantities of these radiation forms.
The primary energy release from both types of weapons, however is in the form of heat.

The Hiroshima bomb was a uranium bomb using an impact trigger. The Nagasaki bomb was a plutonium bomb using an implosion trigger. Impact triggers are not as efficient so more of the fuel in the Hiroshima bomb did not fission and this was spread across the area by the explosion. Essentially, the Hiroshima bomb was much dirtier.

Not everyone in Hiroshima died either in the explosion or subsequently from radiation poisoning or other radiation related diseases. Approximately 200,000 were killed in the explosion, mosty from the heat flash. There have been another 200-300,000 "excess deaths attributed to the effects of the bomb (incidently, even the highest estimated death count from Hiroshima is less than the verified fatalities from the fire bombing of Dresden).

Not everything was destroyed. In Hiroshima today, the remains of a large concrete building that largely survived the blast stand as a memorial. Other concrete buildings also survived. Hiroshima, like most Japanese cities of the time was largely constructed of wood and paper, these of course burned to the ground.

Now, sixty years later the only remaining effects of the bombing at Hiroshima is a slightly higher leukemia rate.

There is of course no scientific data to support the contention that it takes "hundreds of years" for the radiation from a nucear explosion to decrease to safe levels.

Incidently, I've been to Hiroshima and walked directly below the detonation point, and I don't glow in the dark.

Answer 2

Land is in very short supply in Japan. Yes, there are health dangers associated with rebuilding and repopulating the city, however the social demands to get the city running again out-weighed the risks.
The worst of the radioactive isotopes burn themselves out after a few months. The isotopes that are still left last for a very long time, but give off only very low level radiation. This radiation slightly increases the risk of cancer for people living in the area. It is also recommended that people not eat plants grown from the soil around the blast area because the plants concentrate the isotopes in their leaves.
A similar incident happened at bikini atoll where they tested the H bomb. You can safely go there nowadays, it is a beautiful tropical paradise, but don't eat the coconuts!! The coconuts give off moderate radiation and the soil gives off low level radiation.
There are places out in New Mexico and Navada where the eary A bomb tests were done. These areas are also still very radioactive.

Answer 3

Not much was known about the effects of radiation back then. American inspectors toured the drop zone protected only by white cloth tied around their shoes while it was still fresh and 'hot'. I think fresh earth was laid down after a basic clean-up and wash down.
"Hiroshima" by John Hershey tells how awful it was. 100,000 people instantly vaporized in less than 2 seconds. Eyes boiled out of living heads. People couldn't be helped up because their skin pulled off their bodies like fried chicken skin when grabbed. But it stopped the war and really did save millions of lives that would have been lost in a land invasion.

Answer 4

There are three types of radiation released in a nuclear explosion, alpha, beta and gamma. Gamma radiation is the most energetic and therefore the most dangerous to short term health...gamma radiation is what gives people radiation sickness. However because of the high energy of gamma radiation it also has a very short "half life"...it looses 90% of its energy/lethality every 7 hours. Alpha radiation is the next most energetic but unlike gamma radiation it has a very long half life and it takes a large quantity to cause acute sickness. Ingestion of alpha and beta particles does contribute to birth defects and cancers over a long period of time.

Many studies have been done on the population of Hiroshima and Nagasaki over the years...especially by the US DOD...like guinea pigs.

Answer 5

The bombs that were dropped on Nagasaki & Hiroshima where Atomic Bombs which are realitivly small compaired to ICBM's that we think of when we think Nuclear Bombs.
The Modern weapons are the ones that could theroeticly leave radiation for hundreds of years.

Answer 6

The Voice of Reason posted, "The Hiroshima bomb was a uranium bomb. The Nagasaki bomb was a plutonium bomb.Essentially, the Hiroshima bomb was much dirtier".

Answer 7

there's only about 6% above the normal radiation level in hiroshima, which is a lot but not enough to drastically affect life.

Answer 8

Certain mitigation steps have been taken there and at test sites to remove contamination, the soil or anything else, and bury it in special landfills, but they are still learning about and dealing with the long term effects. It is generally believed that as long as the radiation levels are low you can safely be exposed for limited periods, maybe if you lived on ground zero you would have problems. There are links at survivormall.com that might answer the more technical aspects of your question. You have to remember these explosions were quite minor in strength compared to modern weapons.

Answer 9

several factors determined the radioactivity levels of the area after the bombing.

1) the bombs were not nearly powerful as the bombs that we have today.

2) they were uranium bombs, not plutonium or other types.

3) they were detonated in the air above the city, not close to the ground.

4) the winds dispersed much of the radioactive material once it became airborne in the mushroom cloud.

Answer 10

Your avater looks like mine get a hair cut.