radioactivity, how long is it dangerous.

[ricksfolly]

I just read a Travel folder on Hiroshema and not one word in it about radioactive hot spots, 50 years after the A Bomb, so just how long does deadly radioactivity really last? Definitely not the 458 half life years, as we've been led to believe.

ricksfolly

 

[spud_meister]

Depends on the source, and any number of factors.

 

[MaggieD]

I just read a Travel folder on Hiroshema and not one word in it about radioactive hot spots, 50 years after the A Bomb, so just how long does deadly radioactivity really last? Definitely not the 458 half life years, as we've been led to believe.

ricksfolly

I love questions like this!!

You didn't read about any hotspots because there aren't any:

Doses from residual radioactivity in both cities are now far below the annual background dose (0.001-0.003 Sv); hence, there are no detectable effects on human health. Radioactivity was over 90% gone by one week after the bombings and was less than the background level by one year.

People often ask, "If uranium and plutonium pose a potential hazard in nuclear waste sites and were present at dangerous levels in the environment following the Chernobyl nuclear accident, why aren't Hiroshima and Nagasaki still uninhabitable?"

There are two ways residual radioactivity is produced from an atomic blast. The first is due to fallout of the fission products or the nuclear material itself--uranium or plutonium (uranium was used for the Hiroshima bomb whereas plutonium was used for the Nagasaki bomb)--that contaminate the ground. Similar ground contamination occurred as a consequence of the Chernobyl accident, but on a much larger scale (click here for more-detailed explanation). The second way residual radioactivity is produced is by neutron irradiation of soil or buildings (neutron activation), causing non-radioactive materials to become radioactive.

Here's "the rest of the story" -- Frequently Asked Questions - Radiation Effects Research Foundation